Ergo. In The Operating Room.pdf

ERGONOMICS IN THE OPERATING ROOM TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

Cover design by Kirsten Bosscher Printed by Print Partners Ipskamp, Enschede Published by Arma an Albayrak ISBN/EAN: 978-90-5155-050-4 © 2008 Arma an Albayrak All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission from the author.

ERGONOMICS IN THE OPERATING ROOM TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

Proefschrift ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof.dr.ir. J.T. Fokkema, voorzitter van het College van Promoties, in het openbaar te verdedigen op dinsdag 16 december 2008 om 15.00 uur door Arma an ALBAYRAK ingenieur Industrieel Ontwerpen geboren te Ankara, Turkije

Dit proefschrift is goedgekeurd door de promotoren: Prof.dr. H. de Ridder Prof.dr. H.J. Bonjer Copromotor: Dr.ir. R.H.M. Goossens Samenstelling promotiecommissie Rector Magnificus, voorzitter Prof.dr. H. de Ridder, Technische Universiteit Delft, promotor Prof.dr. H.J. Bonjer, Dalhousie University, Canada, promotor Dr.ir. R.H.M. Goossens, Technische Universiteit Delft, copromotor Prof.dr.ir. C.J. Snijders, Technische Universiteit Delft, Erasmus Medisch Centrum Prof.dr. J. Lange, Erasmus Medisch Centrum Prof. A. Melzer, University of Dundee, Scotland, UK Dr. med. U. Matern, University of Tubingen, Germany Prof.ir. D.J. van Eijk, Technische Universiteit Delft, reservelid

Dr. G. Kazemier heeft als begeleider in belangrijke mate aan de totstandkoming van het proefschrift bijgedragen.

“Our true mentor in life is science”

Mustafa Kemal Atatürk

TABLE OF CONTENTS

CHAPTER 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7

9 11 12 13 13 14 15

AN OVERVIEW OF ERGONOMIC PROBLEMS DURING SURGERY

PHYSICAL ERGONOMICS SENSORIAL ERGONOMICS COGNITIVE ERGONOMICS

CHAPTER 3 3.1 3.2 3.3 3.4

9

LAPAROSCOPY SURGICAL TEAM AND WORKING ENVIRONMENT ERGONOMICS AIM DESIGN FRAMEWORK OUTLINE OF THE THESIS READING GUIDE

CHAPTER 2 2.1 2.2 2.3

INTRODUCTION

18 24 25

ERGONOMICS IN THE OPERATING ROOMS OF DUTCH HOSPITALS 31

INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION

32 33 34 35

CHAPTER 4 DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION 4.1 4.2

STUDY I: A NEWLY DESIGNED ERGONOMIC BODY SUPPORT FOR SURGEONS STUDY II: IMPACT OF A CHEST SUPPORT ON LOWER BACK MUSCLES ACTIVITY

5.1 5.2 5.3 5.4

39 41

DURING FORWARD

55

BENDING

CHAPTER 5

17

IMAGE QUALITY DURING LAPAROSCOPIC SURGERY

INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION

75 76 79 86 90

CHAPTER 6 6.1 6.2 6.3

PRACTICAL ERGONOMIC SOLUTIONS FOR THE SURGICAL TEAM

PHYSICAL ERGONOMICS SENSORIAL ERGONOMICS COGNITIVE ERGONOMICS

CHAPTER 7

DESIGN FRAMEWORK FOR DESIGNERS: CASE STUDIES

7.1 7.2 7.3

INTRODUCTION CASE I: SENSORIAL ERGONOMICS – ABDOMINAL WALL TENSION MEASUREMENT DEVICE CASE II: COGNITIVE ERGONOMICS - IMPROVING ERGONOMICS OF MINIMALLY INVASIVE SURGERY - GETTING THE MOST OUT OF AN INTEGRATED SUITE 7.4 CASE III: PHYSICAL ERGONOMICS - DESIGN OF A HANDLE FOR CURVED INSTRUMENTS 7.5 CONCLUSION CHAPTER 8 8.1 8.2 8.3

DISCUSSION

DESIGN FRAMEWORK SURGICAL QUALITY FUTURE RESEARCH

95 96 103 104 111 112 115 122 130 136 141 142 145 147

SUMMARY

149

SAMENVATTING

153

REFERENCES

157

ACKNOWLEDGEMENT

163

CURRICULUM VITEA

167

OVERVIEW PAPERS

169

GLOSSARY

171

CHAPTER 1 INTRODUCTION 1.1

LAPAROSCOPY

Minimally invasive surgery is practiced by a growing number of medical disciplines including general, orthopaedic, paediatric, thoracic and vascular surgery as well as in gynaecology and urology. Since the inception of minimally invasive surgery in general surgery, laparoscopic procedures have become a popular technique. Laparoscopy refers to minimal invasive videoscopic procedures in the abdominal cavity. The first video-laparoscopic cholecystectomy (gallbladder removal) was performed in 1985 by the surgeon Erich Mühe in Germany (Jani et al., 2006). Already in 1999 in the United States, 47% of in total 2.,82,308 general surgical procedures were performed with laparoscopy (Jaspers, 2006). Over the past two decades, laparoscopic cholecystectomy has become the gold standard for surgical management of gallstone disease (Lichten et al., 2001). The growing interest for this method of gallbladder removal is driven by the advantages for the patient such as less pain after surgery, shorter recovery time, better cosmetic results and fewer infections complications (van Veelen, 2003). Considering that laparoscopic cholecystectomy has become the gold standard, the basic steps of this procedure should be discussed to understand the many advantages for the patient. A standard laparoscopic procedure starts with a small incision in the abdominal wall, usually the umbilicus. Through a special hollow needle, the abdomen of the patient is inflated with gas (carbon dioxide, CO2), to create workspace for the surgeon. Through other small incisions, so-called trocars are placed which serve as ports to introduce laparoscopic instruments into the abdominal cavity (figure 1.1).

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

Figure 1.1 During laparoscopic procedures several trocars are used which serve as entrance ports for the laparoscopic instruments and endoscope into the abdominal cavity.

These instruments give the surgical team the ability to manipulate the organs. To observe the abdominal cavity, an endoscope equipped with a small video camera is inserted. The camera is attached to the camera controller (processor unit). During laparoscopy, the surgeon uses 5 or 10 mm instruments to perform the procedure successfully. Generally, the required equipment is placed on a laparoscopy trolley, which holds a monitor, a camera controller, an insufflator that is used for inflation of the abdomen and a light source to illuminate the dark abdominal cavity through a light guide cable connected to the endoscope (figure 1.2).

Figure 1.2 Laparoscopy trolley with the required equipment to perform a laparoscopic procedure.

Laparoscopy, like open surgery, requires general or regional anaesthesia and is therefore performed in the operating room (OR). The OR is a complex environment equipped with all the required equipment and instruments to perform all types of surgical procedures. The OR have a high-quality ventilation system to control and guarantee the quality of the airflow lowering infection risk. To provide a safe and clean environment, the OR’s are divided in areas. In the next paragraph, these different areas and the positioning of the surgical team will be introduced.

10

CHAPTER 1: INTRODUCTION

1.2

SURGICAL TEAM AND WORKING ENVIRONMENT

The operating room is the working environment of the surgical team during surgical procedures and can be divided into three work areas (figure 1.3). The sterile area is around the operating table and in most of the OR’s positioned in the centre of the operating room underneath the clean airflow (laminar flow). The surgeon, the resident, and the scrub nurse are working in this sterile area on either side of the operating table. This environment is sterile from waist to breast height of the surgical team. The resident assists the surgeon during the procedure and the scrub nurse is responsible for passing the required instruments to the surgeon or to the resident. The anaesthesiology area is at the head of the patient. The anaesthesiologist is positioned in this area and is non-sterile. The anaesthesiologist is responsible for monitoring the patient and administering of drugs, fluid and blood. The rest of the non-sterile work area in the operating room forms the third area; this area is the work environment of the circulating nurse. The task of the circulating nurse is to supply equipment and instruments from outside the sterile area to the surgical team and operate the equipment in non-sterile area. Dependent on the procedure, the radiology staff, other disciplines, or guests might also be present in this work area.

Figure 1.3 The three work areas in the operating room.

Although the principles are the same for open and laparoscopic procedures, laparoscopy has altered the way surgeons interact with the surgical field in many ways. Despite the changes in surgical practice due to the introduction of laparoscopic surgery, few changes have taken place in the operating room layout, the position, and posture of the members of the surgical team over the last 100 years. Contradictory, the operating rooms are becoming more and more technology driven. The increasing dependency on technology to perform surgical procedures has significant ergonomic implications for the surgical team. This introduces a multi-disciplinary approach to deal with, focusing on one side on the technology-

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

driven trends and on the other side on the social-economic consequences in surgery. Regardless the kind of discipline, in surgery the human plays a central role. Surgery is practiced by humans to cure, care, and prevent the other humans from illness. Because care, cure, and prevention are human-centred, ergonomics plays an important role in the field of surgery.

1.3

ERGONOMICS

“Ergonomics discovers and applies information about human behaviour, abilities, limitations, and other characteristics to the design of tools, machines, systems, tasks, jobs, and environments for productive, safe, comfortable, and effective human use” (Sanders & McCormick, 1993). Since ergonomics has become relevant for product development and product evaluation, the working principle is; “adapt the environment to the workers, instead of adapting the workers to their environment” (Goossens & Van Veelen, 2001). On this perspective, it is not surprising that knowledge in the field of ergonomics has significant contributions to offer improvement of surgical quality and optimisation of working conditions and performance of the surgical team. From ergonomic point of view the surgical quality can be defined as; “the level of efficiency, safety and comfort of a surgical procedures” (van Veelen, 2003). Efficiency is defined as the coefficient between effort and benefit. In this definition, effort also implies e.g. product life span and learning and understanding the use of the product (e.g. it can take several months to learn how to perform a task without errors). Safety deals with the wellbeing of the user (in the case of minimally invasive surgery also the wellbeing of the patient) and the prevention of injury. Comfort can be defined as a physical and mental state in which one is not aware of any discomfort. The surgical quality and the working condition can be influenced by a variety of organizational and economical aspect but also by human-error due to poor ergonomic conditions such as excessive workload, fatigue, poor human-product interaction, poor communication among staff, etc. (Gawande et al., 2003). The field of ergonomics can be divided along the human functions: physical, sensorial, and cognitive ergonomics. All three types of ergonomics are relevant when discovering ways to improve surgical quality. 1.3.1 Physical ergonomics Emphasis lies on the function of the human musculoskeletal system, which is used to adopt postures, move limbs, and conduct external forces through the body. On the product site, this covers products that support the body, tools and special outfits (Goossens & Van Veelen, 2001).

12

CHAPTER 1: INTRODUCTION

1.3.2 Sensorial ergonomics In this area, the focus is on the human senses and human perception. On the product site this includes products that support the senses and perception, such as visual displays, but also tactile displays and auditory displays (Goossens & Van Veelen, 2001). 1.3.3 Cognitive ergonomics Here the emphasis lies on remembering and processing information; on learning, decision making and judging a situation. It is based on knowledge of the psychology of thinking and remembering. The products that support this part of ergonomics can be schemes of structures, mnemonic devices, software to control a process and training devices (Goossens & Van Veelen, 2001).

1.4

AIM

The aim of this thesis is to improve surgical quality through ergonomics in the operating room. The aim can be divided into the following categories: Gain insight into the ergonomic problems in the operating room. Gain insight into the current state of ergonomics in the operating room. Gain insight into the body posture and physical discomfort that surgeons may experience during surgical procedures. Gain insight into problems intrinsic to laparoscopic viewing regarding sensorial and cognitive ergonomics. Development ergonomic solutions regarding the three domains of ergonomics.

1.5

DESIGN FRAMEWORK

During this PhD-research the basic design cycle of Roozenburg and Eekels is used as a design framework (Roozenburg & Eekels, 1995). The most fundamental model of designing (basic design cycle) is supplemented with the Participatory Design (PD) approach. The medical specialists are professional users with their specific needs, work conditions, working environment, (technical) jargon, work culture, etc. When designing products for professional users their involvement in the design process is crucial since designers can use their knowledge and experience to improve the quality of the design proposal. A methodology, which can be used from this perspective, is Participatory Design (PD) that actively involves the user into the design process, leading to the designed product that meets the user’s specific needs. PD is an approach that is

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

characterized by concern with a more human, creative, and effective relationship between those involved in technology’s design and its use (Namioka & Rao, 1996). PD has been started in Norway in the late 60s and early 70s with the development of the first object-oriented programming language SIMULA. Since its inception, more and more product designers are using this approach during their product development. Participatory design assumes that: Users are experts; PD acknowledges the importance of using the expertise of users and treating them as equal partners on a development team. Tools should be designed for the context in which they will be used; participatory design realizes that an important step to designing new tools is to know where they will be used and in what context, which makes it difficult to design a tool away from the environment in which it will be used. There should be methods for observing or interviewing end-users; to gain an understanding of the environment in which the product will be placed and used, there are several techniques used to watch, observe and interview users in their workplace. Recreating or play-acting a work situation will facilitate the design phase; it mediates the expectations of the users by not providing a non-functional prototype at the very beginning of the design phase. Iterative development is essential; the ideal participatory design project has several iterations of a design-feedback loop, where the developers ask the user for their opinion (Namioka & Rao, 1996). During this PhD project, the emphasise was on the user and their knowledge, the environment wherein this knowledge was created and collecting of data from this environment. Therefore, this PhD-research mainly consists of field studies and has therefore a high ecological validity. Some of these field studies are supplemented with experimental studies. During these field studies, it was difficult to control all the preconditions of testing. As a consequence of this, the results are exploratory and, where possible, it will be reflected on theoretical insights.

1.6

OUTLINE OF THE THESIS

This thesis is based on published or submitted articles. Some of the studies have the same starting point but a different focus. Each of the articles was introduced and discussed from the perspective of that particular focus. Inevitably, this has caused some overlap in the information provided in the different chapters. We have therefore included a reading guide for different reader groups (figure 1.5).

14

CHAPTER 1: INTRODUCTION

The outline of this thesis is visualized in figure 1.4. Chapter 2 gives an overview of the ergonomic problems in surgery. In Chapter 3 the surgeons working area is highlighted regarding the current state of ergonomics in the operating rooms. Chapter 4 deals with the discomfort of surgeons during surgical procedures and evaluation of the developed product solution. In Chapter 5 the focus is on the quality of laparoscopic viewing wherein the quality measurements, the factors describing image quality, and surgeons’ perception of the image will discussed. Hereafter in Chapter 6, an overview of some practical ergonomic solutions will described. In Chapter 7 three cases will presented within the design framework as described in paragraph 1.5. Finally, in Chapter 8, the results of this thesis will discussed and recommendations for future research will described. The definitions of the terminology used in this thesis are described in the Glossary.

Figure 1.4 The outline of the thesis.

1.7

READING GUIDE

Cooperation between two different disciplines “Industrial Design” and “Surgery” is the basis of this thesis and, therefore, two target groups were involved; medical specialist and designers. Hence, in some of the chapters, the focus is on the medical specialists and in others on the designers. The different studies discussed in the chapters of this thesis might also be interesting for policymakers. In figure 1.5 a reading guide for different reader groups is shown.

Figure 1.5 Reading guide for different target readers.

15

This chapter is mainly based on the following book chapter and article: Albayrak A and Snijders CJ. (2007). Basics of Surgery: Tools, techniques, attitude and expertise. Maarssen, Elsevier Gezondheidszorg. 151-169. Bonjer HJ, Albayrak A, Stassen LPS, Casseres YA, Meijer DW. Improving the endoscopic image: tips and tricks. Submitted (2008).

16

CHAPTER 2 AN OVERVIEW OF ERGONOMIC PROBLEMS DURING SURGERY

In the last 100 years little changes have take place in the operating room layout while the operating rooms are become more technology driven (Albayrak et al., 2004; Gallagher & Smith, 2003). The increasing dependency on technology to perform surgical procedures introduced ergonomic problems for the surgical team. In this chapter, an overview will be given of the ergonomic problems in surgery. These problems will be discussed along the three domains of ergonomics; physical, sensorial and cognitive. The physical ergonomics will be restricted to the strain of the musculoskeletal system, which is relevant for neck, shoulder, arm, hand problems, lower back, pelvis, and foot. As most of the sensorial and cognitive problems are seen during laparoscopy this two sections will be focused on the laparoscopic procedures.

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

2.1

PHYSICAL ERGONOMICS

2.1.1 Posture 2.1.1.1 Open surgery Open surgery employs large incisions, which allow direct access to tissues and organs. Through the incision, the surgeon can see, feel, and manipulate the organs in a natural way, which means that direct sensory perceptions and feedback are present. During open surgery, surgeons lean forward toward or across the surgical field to see and manipulate the organs. Consequently, during open surgery the posture of the surgeon is characterized by a head-bent and back-bent posture (figure 2.1). The surgeons’ freedom of movement during open surgery is less restricted allow for a more dynamic body posture than during minimally invasive surgery.

Figure 2.1 The surgeon’s head-bent and back-bent body posture is characteristic of open surgery.

Performing open surgical procedures has almost always required standing, uncomfortable body posture and the occasional need to exert substantial forces on tissues (Berguer, 1999). The body posture of the surgeons during open surgery was described as a head-bent and back-bent posture. Surgeons maintain this posture for long periods of time with the result that they experience physical discomfort during and after surgery. After open surgery, 36.5% of the surgeons report pain in the lower back, 20.6% stiffness of the shoulder and 17.5% pain in the neck (Mirbod et al., 1995). The lower back pain is caused by extending the upper body centre of mass forwards (figure 2.2). This leaning forwards results in increased muscle activity to balance the upper body. Finally, leading to neck and back pain, especially in the lower back. Previous studies showed that surgeons and scrub nurses experience substantial stress of the musculoskeletal system due to their frequent and prolonged static flexion of the neck and lower back (Kant et al., 1992). An OWAS-based (Ovako Working posture Analysis System) analysis of nurses working postures, shows that in both orthopaedic and urology wards, the working posture of the nurses was harmful to the musculoskeletal system (Engels et al., 1994).

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CHAPTER 2: AN OVERVIEW OF ERGONOMIC PROBLEMS DURING SURGERY

Figure 2.2 Displacement of the upper body centre of mass forward is accompanied with increased muscle activity in the lower back to balance the upper body.

2.1.1.2 Laparoscopy During laparoscopic procedures, long instruments are used which give the surgeon the ability to manipulate the tissue, as they were replacing the hands of the surgeon with limited tactile feedback. In addition, the perception of the tissue is not direct on the tissue anymore but using a monitor. Consequently, during these kinds of procedures the posture of the surgeon is characterized by straight trunk, rotation and flexion of the neck. The upper limbs of the surgeon are usually in excursion for handling the long instruments (figure 2.3). During laparoscopic procedures, the body movement of the surgeon is very limited resulting in a more static upright body posture compared to open surgery.

Figure 2.3 During laparoscopy the straight trunk of the surgeon is often accompanied by rotation and flexion of the neck. The upper limbs are usually in excursion for handling long instruments.

Although, during laparoscopy the posture of the surgeon is straight predominantly, due to wrong positioning of the monitors the neck is rotated. Furthermore, the operating table is originally designed for open surgery and is not optimal for minimally invasive procedures regarding the height adjustability. The limited adjustability of the operating tables causes excursion of the upper limbs for handling long instruments. Previous studies reported that approximately 10% of

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

surgeons suffer from pain in the upper limbs and neck during and after minimally invasive surgery (Berguer et al., 1997). The characteristic working situation during laparoscopic procedures involves elongated instruments and limited mobility of the surgeon during the procedure (Schurr et al., 1999). Laparoscopy requires greater concentration and places greater mental stress on surgeons comparing to open surgery (Berguer et al., 2001). The surgical team consists of people of different body stature. The operating table is adjusted in height according to the height of the surgeon. Frequently, however, this working height is not optimal for the remaining members of the team and leads to ergonomically poor conditions. Laparoscopy is implemented in the operating rooms with limited adjustments. The current operating tables are originally designed for open surgery and they are not optimal for laparoscopic procedures regarding ergonomic guidelines (Berguer et al., 2002; van Veelen et al., 2002b). The current operating tables are adjustable in height between 725-1215 mm (Albayrak et al., 2004). A previous study showed that the discomfort and difficulty ratings were lowest when instruments handles were positioned at elbow height of the surgeon (Berguer et al., 2002). Regarding this guideline, the ergonomically operating surface height (defined as the navel height of the patient, lying on the operating table while the abdomen is filled with O2) lies between 0.7 and 0.8 of the elbow height (290-690 mm) of the surgeon (van Veelen et al., 2002b). It should be clear that the current operating tables cannot be lowered enough to meet these ergonomic guidelines. This causes excursion/extension of the upper limbs for handling long instruments. Previous studies reported that approximately 10% of surgeons suffer from pain in the upper limbs and neck during and after laparoscopic procedures (Berguer et al., 1997). The characteristic work situation during laparoscopy involves elongated instruments and limited mobility of the surgeon during the procedure (Schurr et al., 1999). Even if, the posture of the surgeon is more upright during laparoscopy, however, it seems to be accompanied by substantially less body movement and weight shifting than during open surgery (Berguer, 1999). This situation could account for increased static postural fatigue. The configuration of the operating room regarding the ergonomics is restricted during laparoscopy. The percentage of total floor space occupied by personnel, furniture and equipment during laparoscopy is increased by 10% compared with open surgery (Alarcon & Berguer, 1996). Increasing OR crowding may present unnecessary hazards to traffic and adversely affect the performance of the surgical team.

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CHAPTER 2: AN OVERVIEW OF ERGONOMIC PROBLEMS DURING SURGERY

The surgical team also has to deal with problems related to non-optimal working height. The surgical team often consists of people with different body heights. Frequently, the height of the operating table is adjusted according to the height of the surgeon. However, this working height is not always optimal for the other members of the team and can lead to poor ergonomics conditions. The working surface height in relation to subject, performing manual work determines the upper extremity effort and the potential of musculoskeletal injury. Even in the most modern and well-equipped operating rooms, surgeons often face ergonomic shortcomings. As a result, the surgeon is frequently forced to adopt uncomfortable body postures that contribute significantly to fatigue and discomfort, which may lead to musculoskeletal disorders. 2.1.2 Neck 2.1.2.1 Open surgery A working environment regarding ergonomics dictates unobstructed line of vision in neutral standing posture. However, in open surgery, the current position of the resident and scrub nurse mandates back and neck torsion and flexion to allow clear vision on the operating field (Gerbrands et al., 2004). To overcome this, most scrub nurses and residents rotate their body towards the operating field and use a footstool, particularly during deep intra-abdominal or intrathoracic procedures. The current height variation of the available footstools is not sufficient for the different body lengths in the surgical team. Because of the position of the patient, surgeons tend to lean forward toward or across the surgical field to see and manipulate the tissue. This body posture resulting in physical complaints due to neck flexion (figure 2.4).

Figure 2.4 Obstructed line of vision of the resident or scrub nurse due to position of the surgeon.

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

2.1.2.2 Laparoscopy Limited number and wrong positioning of the monitors in the operating room results in physical complaints in the neck (flexion, extension, and rotation). 2.1.3 Shoulder/Arm 2.1.3.1 Open surgery Due to the position and depth of the incision during open surgery, surgeons have fixed work posture, tending to work with arms abducted and unsupported. A high static load is imposed on the shoulder-neck region and shoulder joint by this posture. 2.1.3.2 Laparoscopy During laparoscopy, long instruments are used. Due to the fixed insertion point (position of the trocar) of these instruments, the surgical team has manipulating problems. Besides the manipulating problems, these instruments also cause discomfort in the shoulder if the operating table is not adjusted optimally. Since the operating tables are originally designed for open surgery they cannot adjust low enough which cause excursion of the upper extremities. Besides wearing heavy lead apron also caused physical discomfort in the shoulder-neck region (van Veelen et al., 2003b). 2.1.4 Hand 2.1.4.1 Open surgery The instruments that are used in open surgery are distinguished from instruments for laparoscopy with simplicity of their design and favourable mechanical characteristics. They allow the surgeons with short, solid, and direct contact with tissues and good tactile feedback. There are three basic grip principles to handle instruments: Force grip; grip with fingers and thumb around an object. Force-precision grip; force grip that allows more precision: fingers and thumb are in-line with the forearm. Precision grip; grip that uses the thumb and distal joints of the fingers to grasp an object. A common grasping and manipulating problem is that instruments are being used differently than the way they are originally designed for. For instance, using a precision grip on a handle of an instrument that was designed for force grip. This unintended use of the instruments could result in physical discomfort like pressure on the fingers, elbow- and wrist pain.

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CHAPTER 2: AN OVERVIEW OF ERGONOMIC PROBLEMS DURING SURGERY

2.1.4.2 Laparoscopy The complexity and inefficient mechanical properties of instruments for laparoscopy cause grasping and manipulating problems. The internal mechanical design of instruments results in substantially diminished tactile feedback and an unfavourable force transmission ratio from handle to tip (Berguer, 1999). In comparing with instruments for open surgery, 4 to 6 times more force is required to complete the same task with instruments for laparoscopy (Berguer, 1999). The most frequently used instruments for laparoscopy can be divided in 3 groups: dissector, grasper, and scissors. There is a variety of handle design inside this group like axial, angled shank, multifunctional pistol and ring handle. A previous study shows the results of an experimental comparison of various ergonomic handles and their design (Matern et al., 1999). The objective results of this study show that pressure areas caused by rings and pain caused by ulnar deviation occurred frequently when working with the ring handle. 2.1.5 Lower back 2.1.5.1 Open surgery Bending forward of the body during open surgery to see, feel and manipulate the tissue better, results in increased muscle activity, especially in the lower back to balance the upper body. Maintaining this body posture for long periods of time has consequences for static strain and fatigue in the back muscles. The static strain results in muscle contraction. The generalized excitation-contraction sequence of a nerve impulse travelling from the brain and causing a muscle contraction is as follows. ATP (adenosine triphosphate) phosphate) + energy

ADP (adenosine diphosphate) + CP (creatine

ATP is created by the metabolism of the basic foods we eat. This metabolism can occur in two different modes: aerobic, requiring oxygen, and anaerobic, not using oxygen. Aerobic metabolism uses a slow biomechanical pathway. On the other hand, anaerobic metabolism utilizes a fast glycolytic enzyme to break down the glucose molecule into two lactate molecules and produce two ATPs. The lactate molecule in the extracellular fluid of the body forms lactic acid, which is a direct correlate of fatigue. Thus, the trade-off aerobic metabolism is slow but very efficient, while anaerobic metabolism is very fast but inefficient and gives rise to fatigue. During muscle contraction, less blood reaches the working muscle with a corresponding decrease in oxygen availability. This means that the muscle must

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

rely on a smaller amount of aerobic metabolism and a greater amount of anaerobic metabolism with concurrent fatigue (Freivalds, 2004). 2.1.5.2 Laparoscopy During laparoscopy, the body movement of the surgeon is very limited as compared with open surgery and they have a more static upright posture. The static strain results in muscle contraction. Maintaining this position for long periods of time leads to fatigue in the muscles. 2.1.6

Pelvis

2.1.6.1 Open surgery, laparoscopy During open surgery as well as laparoscopy, the surgical team tends to lean toward the rails of the operating table since this is the only supporting surface around the table. The solid and metal edge of this rail results in bruising in the soft tissue around the pelvis region. 2.1.7 Foot 2.1.7.1 Open surgery During open surgery, the diathermy equipment is handled by a knob, which is integrated in the instrument. Due to manual control of this equipment, a pedal is unnecessary. 2.1.7.2 Laparoscopy During laparoscopy, a pedal is used to handle the diathermy and ultra-scission equipment. The current pedals cause positioning problems due to loosing contact which contributes to a poor body posture of the surgeon. In addition, there is a risk of accidentally activating the wrong function (left or right) because of lack of vision. To hold the foot above the right side of the pedal the surgeon has to keep his/her foot generally in dorsal flexion. Due to the dorsal flexion of the foot, surgeon’s weight is not equally divided over both legs and finally results in an ergonomic poor and static body posture.

2.2

SENSORIAL ERGONOMICS

The current ergonomic layout of operating rooms with crowding of free-standing equipment such as the laparoscopy tower, often precludes optimal placement of the monitor in front of the surgeon (Alarcon & Berguer, 1996). Accordingly, the visual axis between the surgeon’s eyes and the monitor is no longer aligned with the hands and instruments, Furthermore, the monitor is often far removed from the surgeon and thus the spatial location of the display system (sensory information) is

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CHAPTER 2: AN OVERVIEW OF ERGONOMIC PROBLEMS DURING SURGERY

remote from the manipulation area at the hand level of the surgeon (Hanna et al., 1998). With the current monitors as the standard image display system for laparoscopic surgery, monocular depth cues within the image are further degraded by “anticues” arising from the monitor. These are caused by the monitor frame and the glare and reflection from the glass of the monitor. All these factors add to the degradation in task performance compared to open surgery with normal monocular vision. Since the image display system during laparoscopic procedures replaces “the eye” of the surgeon, some factors influencing the image quality have to be mentioned. The three major components describing image quality are resolution, luminance and chroma (Hanna & Cuschieri, 2001). Image resolution determines the visibility of details in the image and refers to the sharpness and contrast of the picture; luminance refers to the amount of light available in the image (brightness), and chroma denotes the colour intensity or saturation. Several optical factors may degrade image quality (Eden et al., 1993). Resolution and contrast influence the ability to appreciate fine details of the image. The resolution and contrast can also be reduced by glare. Glare can be caused either by internal reflections (on-axis glare) or by stray light entering the system from outside the field of view (off-axis glare)(Berber et al., 2002).

2.3

COGNITIVE ERGONOMICS

(The theory explained in this section is adopted from Cuschieri, 2006a) Humans perceive the three-dimensional world by a pair of two-dimensional retinas that react to visible light. The resulting image recognized by the subject in the cognitive process is known as a percept, which determines the interpretation of the visual information (Cuschieri, 2006a). Visual psychologists distinguish two kinds of perceptions: direct (perception of objects in 3D space) and indirect (perception of pictures/images of objects rather than the objects themselves) (Cuschieri, 2006a). During open surgical procedures, the surgeon can view the operating field directly. The theory of James Gibson can elucidate the cognitive stage of direct visual perception (Cuschieri, 2006a). This theory postulates a data-driven bottom-up process and implies direct perception (i.e. the visual data have sufficient information and are structured within the optical pathway before reaching conscious perception) (Cuschieri, 2006a). Conversely, during laparoscopic procedures surgeons must operate guided by images rather than reality (indirect perception).

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

According to Gibson, pictures and images of objects have been shown to induce more perceptual errors than direct perception of objects because they are the result of viewing with inadequate information (Cuschieri, 2006a). This consideration is of paramount importance during laparoscopy since the surgical team is almost completely dependent on the indirect perception. The monitor is hereby the only interface between the surgical team and the surgical field and thus the main source yielding/displaying information about the progress of the procedure. A high quality of the image is therefore requisite to allow safe and efficient laparoscopic procedures. 2.3.1 Image quality The image during laparoscopy, displayed on the monitor is a product of the socalled “imaging chain” consisting of light source, light guide cable, endoscope, camera, camera unit and monitor (Schwaitzberg, 2001). This results in several places where the image can be distorted. To be able to structure the complex relation between the quality of the displayed image, surgeons perception of this image, and the several components of the “imaging chain” as described above, the framework of the Engeldrum’s Image Quality Circle (Engeldrum, 2000) could serve as a framework. In figure 2.5 the topics, which are in the scope of this thesis, are shown in perspective of Engeldrum’s Image Quality Circle. The circle on the outside represents the original framework of Engeldrum (Engeldrum, 2000). The circle on the inside shows the topics, which are relevant for this thesis. The technology variables are not included in the research.

Figure 2.5 The circle on the outside represent the original framework of Engeldrum’s Image Quality Circle (Engeldrum, 2000) and the circle on the inside represents the topics, which are in the scope of this thesis. The technology variables are not included in the research.

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CHAPTER 2: AN OVERVIEW OF ERGONOMIC PROBLEMS DURING SURGERY

The Image Quality Circle is a framework, which organizes the multiplicity of ideas that constitute image quality. The Image Quality process begins with determining Customer Quality Preference and in perspective of laparoscopic procedures represents the surgeon’s opinion of image quality. This judgment is connected to the third element Physical Image Parameters. These are objective measures of image quality such as the resolution of the endoscope and monitor and measurements of light transmission of the endoscope and light guide cables. The last part completing the circle is the Customer Perceptions – The “Nesses”. These are perceptual attributes mostly visual that form the basis of the judgment of the surgeon. (Since most visual perceptual attributes like, sharpness, brightness, etc. end with suffix “ness”, this term is used as a shorthand notation to emphasise the connection to human perception). Laparoscopic surgery is introduced without much consideration for ergonomic limitations. The technology that surgeons use to perform laparoscopy caused a human-product miss-match. This has largely to do with shortcomings of the equipment and instrumentation that surgeons have to use or interact, unforeseen ergonomic issues (Gallagher & Smith, 2003). 2.3.2 Cognitive problems during laparoscopic procedures There are several factors intrinsic to laparoscopic viewing that degrade the surgical quality and enhance the probability of error during surgical procedures. Many of the related problems are due to the perceptual and spatial factors. One of the major perceptual problems is that the image on the flat monitor screen contains only monocular (pictorial) depth cues of the surgical field to the surgeon (Hanna & Cuschieri, 2001). This representation of the three-dimensional surgical field on a two-dimensional screen may reduce depth perception since retinal disparity, and therefore the resultant stereoscopic vision (i.e. integrated information from two viewpoints) providing the surgeon a strong sense of depth is missing (Shah et al., 2003). A further perceptual problem in laparoscopy arises from scaling difficulties caused by the magnification and the severely degraded visual image of the anatomy in comparison to the experience of an open procedure (Gallagher & Smith, 2003). The various spatial difficulties encountered during laparoscopy result in problems with cognitive mapping and hand-eye coordination. The monitor presents vastly different images of anatomy due to the perspective and magnification of objects closest to the endoscope. Spatial discrepancies are also caused by a misinterpretation of angular relationships (the azimuth angle), because the entry

27

ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

points of instruments do not correspond with the optical axis of the endoscope camera (Gallagher & Smith, 2003). Another problem with a spatial aspect involves camera etiquette. The surgeon has no direct control over the position or orientation of the endoscope. Instead, the surgeon must rely on the assistant to maintain an optimal position; however, frequently unintentional camera rotation occurs that can lead to disorientation and misinterpretation of position of the organs. One of the problems limiting the surgeon’s acquisition of skill and degrading the surgical quality is due to the fulcrum effect. The fulcrum effect of the body wall causes an inversion of the perceived movements. An internal movement to the right is displayed as a movement to the left on the monitor. For an inexperienced surgeon this results in a significantly poorer performance (Gallagher & Smith, 2003). Some of the problems are caused due to the limitations of the components of the “imaging chain”. Both light guide cables and endoscopes contain glass fibres to transmit light. These glass fibres have a high transmission coefficient. However, reduction of loss in light in light transmission occurs in the delivery system due to; Differences of diameters on the connection of the light guide cable with the light source. Differences of diameter between the light guide cable and the endoscope. Surface losses and bulb absorption. Because of these losses, the transmission coefficient of this part of the imaging channel is reduced to 20 percent in the best system. As a result of all the losses, a typical system will deliver considerably less then 1 W of visible light from a 250 W source lamp (Frank et al., 1997). Additionally, loss in illumination is caused by ageing of the light source and mechanical damage due to repetitive use and sterilization of light guide cables and endoscopes resulting in breakage of fibres. Melted or broken fibres reduce the illuminance of the abdominal cavity. Optimal illumination of the dark abdominal cavity is indispensable for carrying out any minimally invasive procedure. In an endoscope, the lenses are positioned in the centre surrounded by optical fibres that transmit light from the light source to the surgical field (Boppart et al., 1999). This configuration imposes certain problems. In the first place, the level of illumination across the surgical field is uneven, that is, the periphery of the endoscopic field is less well illuminated (Hanna & Cuschieri, 2001).

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CHAPTER 2: AN OVERVIEW OF ERGONOMIC PROBLEMS DURING SURGERY

The coaxial alignment of optical fibres and the optical lens system also results in a shadow less surgical field as both light directions and optical axis subtend the same angle to the target organ. Because shadows constitute very important pictorial depth cues, their absence detracts further from the visual information presented to the surgeon (Hanna & Cuschieri, 2001). In the second place, the viewing angle of the endoscope refers to the angle formed by the two outer visual limits and determines the diameter of the field of view and the magnification. Restricted field of endoscopic vision predispose to iatrogenic tissue injury when instruments move outside the field of view and account for the high percentage of bile duct and bowel injuries that are missed during laparoscopic surgery and declare themselves by virtue of major complications in the postoperative period (Fletcher et al., 1999; Russel et al., 1996). The term distortion is applied to the image where lines at the edge of the image appear curved. Outward curved lines are termed “barrel distortion”, often encountered, in endoscopes. The distortion effect increases with wider field of view. Field curvature indicates that the centre and the edge of the image are not in focus at the same time. This is difficult to perceive during viewing by eye due to the constant refocusing of the human ocular lens. The ergonomic problems discussed in this chapter show how divers the problems are that the surgical team has to deal with in their profession in daily life. The overview also shows the opportunities to improve the surgical quality and optimize the work conditions of the surgical team. In the next chapters, these problems will be analyzed from a certain perspective and the solutions will be discussed.

29

This chapter is based on the following article: Albayrak A, Kazemier G, Meijer DW, Bonjer HJ. (2004). Current state of ergonomics of operating rooms of Dutch hospitals in the endoscopic era. Minimal Invasive Therapy & Allied Technologies. 13(3); 156-160.

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CHAPTER 3 ERGONOMICS IN THE OPERATING ROOMS OF DUTCH HOSPITALS

Most of the laparoscopic procedures are performed in operating rooms, which originally have been designed for open surgery. The ergonomic layout of these operating rooms is often not suited for laparoscopic surgery. This study reports the current state of ergonomics of Dutch operating rooms for laparoscopic surgery. For this purpose, twenty-nine hospitals were visited and an inventory was made of the number of laparoscopy trolleys, presence of ceiling-mounted booms, and number, positioning and dimension of the monitors. Additionally, the number of operating rooms was recorded and the floor surface area of these operating rooms was measured. Positioning of the surgical team and monitors around the operating table were assessed and the range of height adjustment of the operating tables was documented. Results showed that the floor space of current operating rooms is too small to allow use of space occupying technological systems for laparoscopic surgery. Most of the monitors were positioned on a laparoscopy trolley with a fixed height and the operating tables cannot be lowered to a position, which allows an ergonomic posture of the surgical team. Implications of these findings toward positioning and posture of the surgical team are discussed.

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

3.1

Introduction

The majority of current operating rooms (OR’s) have been designed in the second half of the 20th century to allow performance of open surgery. Novel operating techniques, such as laparoscopic and robotic surgery, differ from open surgery in many ways. To perform these types of surgery successfully, trolleys for laparoscopic surgery, monitors, and robotic systems are required. Laparoscopic equipment such as camera, light source, and insufflator are usually placed on one or more laparoscopy trolleys. This trolley-based model restricts the ergonomic configuration of the operating room. Alarcon et al. showed that the percentage of total floor space occupied by personnel, furniture, and equipment during laparoscopic procedures increased by 10% over open procedures (Alarcon & Berguer, 1996). Increasing OR crowding may present unnecessary hazards to traffic and adversely affect the performance of the surgical team (Alarcon & Berguer, 1996). Most references of OR design state that the minimum dimensions for a modern OR should be 37 m2 while specialized rooms require up to 55 m2 of floor space (Quebbeman, 1993). A possibility for optimizing the workspace in the OR is placing laparoscopic equipment on a ceiling-mounted boom. This increases the working space around the operating table and will facilitate positioning of heavy trolleys, improving the ergonomic configuration of the OR. During laparoscopic surgery, longer instruments are used compared to open surgery. Studies have shown that long laparoscopic instruments potentially cause excessive flexion and ulnar deviation of the surgeons wrist and abduction of the arms during manipulation, particularly if the operating table can not be lowered sufficiently (Berguer, 1998; Matern & Waller, 1999). It has been reported that the ergonomically optimal operating height is between 70 and 80 % of the height of the elbow of the surgeon (van Veelen et al., 2002b). Menozzi et al. advised to position the monitors in front of the viewer with a downward gaze of approximately 100 to 250 below eye level (Menozzi et al., 1994). To allow these conditions, monitors should be mobile and in height adjustable. This study reports the current state of ergonomics of Dutch operating rooms for laparoscopic surgery.

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CHAPTER 3: ERGONOMICS IN THE OPERATING ROOMS OF DUTCH HOSPITALS

3.2

Materials and Methods

Twenty-nine Dutch hospitals have been visited. Two of the 29 visited hospitals were academic hospitals, 12 were teaching hospitals and 15 were community hospitals. The operating room departments of each hospital were visited and the following items were recorded: Number of operating rooms per hospital type. Number of available laparoscopy trolleys. Mid monitor height (figure 3.1). Monitor type and dimension. Monitor placement (either on trolley or on ceiling-mounted boom). Operating room floor surface area in m2. Range of height adjustment of operating tables. Positioning of the surgical team.

Figure 3.1 Mid monitor height.

The positioning of surgical teams was registered during 48 laparoscopic cholecystectomies and hernia repairs. To determine the optimum number and positioning of the monitor relative to the user’s eyes, each positioning was analysed.

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3.3

Results

3.3.1 Hospitals and operating rooms The average number of operating rooms per hospital type is presented in table 3.1. Table 3.1 Average number of operating rooms per hospital type. Hospital type

Average number of operating rooms

University hospital

19.5

Teaching hospital

7.6

Community hospital

5.3

3.3.2 Trolleys In the 29 hospitals visited, 69 laparoscopy trolleys were present with a median of two and an average of 2.4 trolleys per hospital. The average number of trolleys at university hospitals was 2, at teaching hospitals 3.25 and at community hospitals 1.7. 3.3.3 Monitors In total 65 monitors were available at the visited hospitals. The average mid monitor height was 163 cm (range 145-180 cm). All monitors were Cathode Ray Tube monitors (classic monitors) except for one monitor being a 13’ inch Liquid Crystal Display. All monitors were placed on trolleys except for two, which were attached on a ceiling-mounted boom. One of the 29 hospitals had ceiling-mounted booms for placement of two monitors. The dimension and the number of the monitors are shown in table 3.2. Fifty-one monitors (81%) were fixed on the top of the trolley. Twelve monitors (19%) were attached to the trolley by a swinging arm, allowing it to move towards or swing over the operating field. Table 3.2 Dimension, number and mobility of monitors per hospital type. Number of fixed monitors per hospital type Monitor dimension (inch)

Academic

Teaching

13

Number of swinging monitors per hospital type Community 2

14

1

18

2

2

19

12

4

4

19 20 21

34

4

Academic

Teaching

Community

5

2

1

1

1 2

1

CHAPTER 3: ERGONOMICS IN THE OPERATING ROOMS OF DUTCH HOSPITALS

3.3.4

Operating rooms

The average operating room floor surface area was 37.45 m2 (range 22.03 to 44.14 m2). The average operating room floor surface area at academic hospitals was 32.1 m2, at teaching hospitals 36.56 m2 and at community hospitals 38.05 m2. 3.3.5 Operating tables The average range of height adjustability of operating tables was from 725 mm to 1215 mm. 3.3.6 Positioning of surgical teams Five different positions of surgical teams were registered (figure 3.2). Position 1 and 4 were encountered in 12% of procedures, position 3 and 5 in 21% of procedures, and position 2 in 67% of procedures. There was no difference in distribution of positioning of the surgical team over each type of hospitals.

Figure 3.2 Different positions of the surgical team during laparoscopic surgery.

3.4

Discussion

Laparoscopic surgery has changed the requirements of modern operating rooms greatly. To allow laparoscopic surgery, multiple monitors and a videoscopic working unit, which is usually assembled in a trolley, are necessary. In the early days of laparoscopic cholecystectomy, a monitor mounted on top of the videoscopic trolley was the only screen available to the surgical team. Positioning the screen in line of the surgeon’s eye and the target organ interfered with the operating table and the respirator, which is commonly standing at the right shoulder of the patient. A short swinging arm carrying the monitor mounted on the trolley can improve the degree of freedom to some extent. Attachment of the monitor on a ceiling-mounted boom allows a placement of the monitor without interference with operating table or respirator. The use of ceiling-mounted booms for supply of oxygen, anaesthetic

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

gases, and electric outlets has become commonplace. Use of ceiling-mounted boom for monitors is, however, rare, given that only one of the visited had such a setup. The disadvantage of attaching a heavy monitor on a ceiling-mounted boom is the necessity to install heavy-duty booms. Moving the monitor and boom requires substantial physical strength. The latest high quality versions of flat screens, which are low in weight, are easy to position and take up less space. In laparoscopic surgery, members of the surgical team stand on both sides of the table in the great majority of procedures. Assessing the position of the surgical team from an ergonomic point of view, position 1 and 4 require one monitor (12% of procedures), position 3 requires two monitors (11% of procedures), and position 2 and 5 require three monitors (77% of procedures) to allow unobstructed line of vision without neck torsion by each member of the surgical team (figure 3.3).

Figure 3.3 Ergonomically optimal positioning of the surgical team and number of monitors.

To allow the surgical team to watch the screen without cervical torsion, this study shows that employment of two or more monitors is mandatory in those instances. In this study, only seven of 29 (24%) hospitals used multiply monitors. When the screen is attached on a ceiling-mounted boom that can be moved up and down, the optimal viewing angle of 10-25 degrees downward gaze can be realized (Menozzi et al., 1994). The optimal dimension of the monitor is determined by the distance between the surgeon’s eye and the screen. In the majority of the hospitals 19-inch screen were used. Considering this screen size, the average distance

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CHAPTER 3: ERGONOMICS IN THE OPERATING ROOMS OF DUTCH HOSPITALS

between the surgeon’s eyes and the screen should be between 70-95 cm (Menozzi et al., 1994). The total length of the arm of the surgeon holding a laparoscopic instrument is approximately 30 cm greater than that of a surgeon’s arm holding an instrument for open surgery. Studies show that long laparoscopic instruments potentially cause excessive flexion and ulnar deviation of the surgeons wrist and abduction of the arms during manipulation (Berguer, 1998; Matern & Waller, 1999). The optimal height of the operating table in open surgery is three quarters of the height of the surgeon’s elbow (van Veelen et al., 2002b). Given that the average height of the elbow of the surgeon (± SD) is 110 cm (male and female) (www.dined.nl, 2004), the table should be positioned at a height of 82.5 cm for open surgery. Adding the length of laparoscopic instrument converts the optimal height of the operating table for laparoscopic surgery to 52.5 cm. To prevent undue strain of the surgeon’s upper limbs, operating tables should be lowered further than currently possible. Berguer et al. showed, using electromyography, that a mismatch between table height and body length of the surgeon increases muscular strain (Berguer et al., 2002). The floor surface area of operating rooms in the first half of the 20th century tended to be greater than in the second half. In the early nineteen hundreds day light was a main source of lighting the surgical field. Therefore, large windows were necessary to provide sufficient exposure to day light. Furthermore, surgical instruments in large canisters were stored in the operating room instead of in a separate room. Due to the development of high power operating lamps and alternative design of the operating room complex, the floor surface area of operating rooms was reduced. The introduction of laparoscopic surgery, image-guided surgery and other new technologies such as ultrasonic and radiofrequency surgery to ablate tissue has again increased the demand for space. The modern operating room should have a surface between 37 and 55 m2 (Quebbeman, 1993). In this study, the average floor surface area of the operating rooms was 37 m2, which indicates that half the operating rooms are not fit for these novel technologies. In conclusion, current operating rooms in The Netherlands are insufficient from an ergonomic point of view to perform laparoscopic surgery. Future designs of operating rooms and laparoscopic equipment should consider basic ergonomic principles to prevent work related injuries and to allow optimal performance of the entire surgical team.

37

This chapter is based on the following articles: Albayrak A, van Veelen MA, Prins JF, Snijders CJ, de Ridder H, Kazemier G. (2007). A newly designed ergonomic body support for surgeons. Surgical Endoscopy 21(10): 1835-1840. Albayrak A, de Ridder H, Bonjer HJ, Goossens RHM, Snijders CJ, Kazemier G. (2006). Reducing muscle activity of the surgeon during surgical procedures. In Proceedings of the 16th World Congress on Ergonomics, Maastricht, The Netherlands: International Ergonomics Association. Albayrak A, Goossens RHM, Snijders CJ, de Ridder H, Kazemier G. Impact of a chest support on lower back muscles activity during forward bending. Submitted (2008).

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CHAPTER 4 DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION

One of the main physical ergonomic problems during surgical procedures is the surgeons’ uncomfortable body posture. Surgeons maintain this position for long periods often resulting in physical discomfort during and after surgery. Furthermore, people of different body height are often present within the surgical team. During both kinds of procedures, the operating table is adjusted in height best suiting the surgeon. Frequently, however, this working height is non-optimal for the other members of the team. Study I is focusing on the design process of development of a product solution that supports surgeons during both open and minimally invasive procedures, reduces the surgeons muscle activity in the lower back and extremities, and solves problems related to non-optimal working height. The aim of Study II is to investigate the impact of the developed product solution on lower back muscle activity during forward bending and to establish a possible relation between the supporting force and the kind of balancing strategy a person adopts.

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

40

CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY I

4.1

Study I: A newly designed ergonomic body support for surgeons

4.1.1 Introduction Increasingly, more general surgeons are performing minimally invasive procedures in addition to open surgery. Although the basics of laparoscopic and open procedures are similar, minimally invasive procedures have altered the way surgeons interact with the surgical field, which requires a change in the surgeon’s posture. A head- and back-bent posture and a twisted torso characterize the posture of the surgeon during open surgical procedures. Conversely, during laparoscopic procedures, the posture of the surgeon is characterized by a head- and back-straight posture. The poor ergonomic posture of surgeons during both kinds of procedures can result in physical discomfort. Due to the position of the patient during open surgery, surgeons tend to lean forward toward or even over the surgical field to see and manipulate the tissue. This leaning forward results in increased muscle activity to balance the upper body. Kant et al. reported that surgeons and scrub nurses exhibited frequent static body postures that were ‘‘distinctly harmful’’ and contributed to physical fatigue during surgery (Kant et al., 1992). Maintaining the uncomfortable position of the body for longer periods results in musculoskeletal fatigue and physical complaints on the part of surgeons. After open surgery, 30% of surgeons report pain and stiffness of shoulders, neck, and lower back (Mirbod et al., 1995). These complaints are caused by extending the centre of gravity of the upper body forwards (figure 4.1).

Figure 4.1 Displacement centre of gravity of the upper body as a result of bending forward.

During laparoscopy, the upper extremities usually are in uncomfortable excursion for handling the long laparoscopic instruments (figure 4.2). The upright posture during these procedures, however, seems to be accompanied by substantially less body movement and weight shifting than during open surgery (Berguer et al.,

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

1997). Cuschieri has described a ‘‘surgical fatigue syndrome’’ that occurs after minimally invasive surgery has been performed for 4 hours (Cuschieri, 1995).

Figure 4.2 Uncomfortable excursion of the upper extremities as a result of using long laparoscopic instruments.

In addition to poor posture, which can cause musculoskeletal fatigue, the surgical team also has to deal with problems related to non-optimal working height. The surgical team often consists of people with different body heights. Frequently, the height of the operating table is adjusted according to the height of the surgeon. However, this working height is not always optimal for the remaining members of the team and can lead to ergonomically poor conditions. The working surface height relative to a subject performing manual work determines the upper extremity effort and the potential for musculoskeletal injury. Furthermore, operating tables were originally designed for open surgery, they are not optimal for minimally invasive procedures. The operating tables are adjustable in height between 725 and 1215 mm (Albayrak et al., 2004). A previous study showed that the discomfort and difficulty ratings were lowest when instrument handles were positioned at the elbow height of the surgeon (Berguer et al., 2002). Regarding the guideline of positioning the instruments at elbow height, the ergonomic operating surface height (defined as the navel height of the patient lying on the operating table while the abdomen is filled with carbon dioxide [CO2]) lies between 0.7 and 0.8 of the operator/assistants elbow height (650–1000 mm) (van Veelen et al., 2002b). It is obvious that current operating tables cannot adjust low enough to satisfy the ergonomic guidelines, thus changing the relation between the height of the surgeon’s hands and the desirable height of the operating table (van Veelen et al., 2002b).

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CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY I

Crowding in the operating room and positioning of the surgical team around the operating table also contribute to the aforementioned problems. Alarcon and Berguer concluded that there is a significant trend toward increasing operating room crowding during laparoscopy (Alarcon & Berguer, 1996). The percentage of operating room space occupied by furniture, equipment, and people increased from 36% for open surgery to 41% for laparoscopy. The median number of pieces of equipment present in the operating room increased from 6 for open procedures to 13 for laparoscopic procedures, reflecting the increased dependency of laparoscopy on technology (Alarcon & Berguer, 1996). Additionally, the freedom of positioning the surgical team and equipment around the operating table is limited because the base of the operating table is usually fixed to the floor. This study aimed to develop an ergonomic body support that supports surgeons during both open and minimally invasive procedures, reduces the surgeons muscle activity in the lower back and extremities, and solves problems related to nonoptimal working height. 4.1.2 Materials and methods During the design process, the participatory design approach was used. This approach involves the user group throughout the whole design process to help ensure that the product designed meets their needs (Muller & Kuhn, 1993). The surgeons of the Erasmus Medical Centre in Rotterdam were closely associated with this study. After a literature study, observations, interviews, and analysis of the current situation, a couple of design criteria were formulated. Based on these design criteria, a prototype was built. The feasibility of this prototype was assessed during surgical procedures in the operating room, and a questionnaire was used to record the value of the prototype as perceived by the participating surgeons. Furthermore, electromyography (EMG) recording was accomplished with one subject using the prototype. 4.1.2.1 Design criteria The most important design criteria were as follows: Support for the body of the surgeon in a natural working posture. A product suitable for use during both open and minimally invasive procedures. Compact construction of the product because of the limited space available around the operating table. Comfortable and safe use of the product by both the P5-woman (5th percentile of short women) and the P95-man (95th percentile of tall men) (percentiles of the Dutch population with regard to body length) (www.dined.nl, 2004).

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

A height-adjustable platform to solve the problems related to non-optimal working height. Sufficient space for positioning of foot pedals for electro surgery. A product mobile by means of wheels. 4.1.2.2 Supporting principles & Biomechanics Taking for granted that surgeons have a head- and back-bent posture during open procedures, support for the surgeons upper body is obvious. To develop a wellconsidered body support, defining the optimal supporting height of the upper body is important. Due to their body posture, surgeons experience physical discomfort in their lower back during and after open surgery. Accordingly, in the biomechanical model the forces are assessed in the lower back (Snijders et al., 2004). For the analysis of load transfer at the lumbar level, a free body diagram was made. The mass centre of gravity of the upper body is located just below the axillaes. Here the gravity force (Fg) is drawn. The disc L5-S1 is located in the cross-section (D) and can be considered as the hinge of a joint (figure 4.3). The horizontal distance between gravity force and this joint is the lever arm (a) of upper body weight. The product of Fg and a produces moment M = Fg x a which tends to rotate the upper body clockwise. This must be counteracted by a moment with counter clockwise direction. This is produced by the back muscle force (Fm) with lever arm b with respect to the middle of the disc. Additionally, the supporting force Fsupport also produces a moment M = Fsupport x c with counter clockwise direction (c is the distance between the centre of the chest support and the centre of the disc (D)). Equilibrium of moments results in; Fg . a = (Fm . b) + (Fsupport . c) or Fm = Fg . a/b – Fsupport . c/b.

Figure 4.3 Free body diagram at the lumbar level.

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CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY I

According to biomechanics, a head support is the most effective in reducing the muscle activity in lower back since distance c is maximum. However, this way of supporting is not desirable because the surgeon’s freedom of movement will be reduced dramatically. Additionally, this also will lead to an extra couple (torque) in the neck. Nevertheless, the upper body still must be supported as high as possible. Supporting the upper body at chest height is a viable option because the remaining part of the upper body consists of soft tissue. Pressure due to the supporting force on the soft tissue will not be experienced as comfortable. Because surgeons have an upright body posture during laparoscopic procedures, it is obvious that they should be supported in the semi-standing position. In addition, this way of supporting allows the surgeon to operate in the ergonomic manipulative zone (Gerbrands et al., 2004). The choice of the chest and semi-standing support is described in more detail elsewhere (Albayrak et al., 2006b; Albayrak et al., 2006c). Electromyography using the chest support The effectiveness of the chest support is evaluated by means of electromyography (EMG). The muscle activity of five subjects (P5, P50, P95-woman and P50, P95-man, Dutch population) was measured while they simulating a surgical task according to a protocol. The measurements were done in four conditions; Relaxed standing. Bending forward without support on angle 1 and 2. Bending forward with support on height h1 and angle 1 and 2. Bending forward with support on height h2 and angle 1 and 2. Height h1 was defined as 0.8 x shoulder height, h2 as 0.9 x shoulder height, 1 as 15º and 2 as 20º. A selected muscle group was examined in the laboratory by means of EMG recording according to the protocol. To normalize the data for comparison, the maximum voluntary isometric contraction (MVIC) also was measured, obtained with manually applied resistance (Kumar & Mital, 1996). Before the electrodes were attached, the skin was grated, and then cleaned with alcohol. A reference electrode was placed around the left wrist. For the MVIC and EMG recordings, a portable physiologic measurement system, type Porti 5–16/ASD of TMS International B.V. (Enschede, The Netherlands) was used. The Ag/AgCl surface electrodes with recessed pre-gelled (hydrogel) elements (GE Medical Systems Accessories Europe) were used to collect the EMG and MVIC signals. The raw EMG signals (DC frequency, ~2 KHz) were processed electronically with a sample rate of 1,000 Hz, and the cut-off frequency was 10 ± 200 Hz. The following muscles were examined: Erector spinae muscle (back muscle, right sides about 2 cm from the midline at the level of L5-S1) (Snijders et al., 1998). Semitendinosus muscle (hamstring). Gastrocnemius muscle (calf muscle, caput mediale).

45

ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

SPSS 11.0 for Windows was used for statistical analysis of the results. The Repeated-Measures ANOVA’s, 2 (angles 1 en 2) x 3 (with/without support on height h1 and h2) was done per muscle group. All effects were reported as significant at p 0.05. 4.1.2.3 Development of the ergonomic surgeons body support Based on the formulated design criteria and biomechanical analysis, different sketches were considered. The involved surgeons of the Erasmus Medical Centre have chosen the represented idea. Development of this idea has led to different concepts, the most likely of which is illustrated in concept phase 1. Elaborating the principle in more detail has resulted in the concept demonstrated in phase 2. The final design presents the completely worked out product. Figure 4.4 shows an impression of the design process.

Figure 4.4 Design process for the ergonomic surgeons body support.

4.1.2.4 Prototype Further development of the concept in detail has finally led to building a functional prototype (figure 4.5). The body support consists of different parts. The surgeon stands on a platform that can move up and down (as directed by a remote control). There is a chest support, which the surgeon can activate during open procedures by leaning against it. The chest support is adjustable in height and can be removed easily, which allows the surgeon more space during laparoscopic procedures or

46

CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY I

emergency situations requiring fast removal of the support. A semi-standing support also is integrated into the body support for use during minimally invasive procedures. For positioning and fixation of the foot pedal, metal strips are integrated into the platform. Wheels beneath the base make the prototype fully mobile. When the surgeon stands on the platform, his or her bodyweight causes the wheels to collapse because they are fixed with a spring construction. This solution simultaneously offers stability by standing on the platform and mobility by stepping down.

Figure 4.5 Prototype of the ergonomic surgeons body support.

4.1.2.5 Questionnaire The feasibility of the designed ergonomic body support was assessed during several open and laparoscopic procedures in the operating room of the Erasmus Medical Centre (figure 4.6). For an objective assessment of the prototype, the surgeons involved in developing the body support were excluded from the feasibility study. A questionnaire was used to record the value of the support as perceived by the participating surgeon.

47

ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

Figure 4.6 Feasibility of the prototype during minimally invasive procedures (right side) and open procedures (left side).

4.1.2.6 Electromyography using the prototype To evaluate the effectiveness of the prototype an electromyography study has been done by measuring the muscle activity of one subject (P50-man) while he was simulating a surgical task according to a protocol. The measurements for chest support were performed in four conditions: Relaxed standing. Bending forward without support (angle 15ºand 20º). Bending forward with support on chest height (angle 15º). Bending forward with support on chest height (angle 20º). The measurements for semi-standing support were performed in two conditions: excursion of upper extremities with and without semi-standing support. The bending angles and the upper body extremities were measured using a digital protractor type 106 ES (Mahr, Göttingen, Germany). The same EMG equipment has been used which is discussed previously in this study. 4.1.3 Results 4.1.3.1 Electromyography using the chest support The results of the EMG-recording of the three measured muscles (erector spinae, semitendinosus, and gastrocnemius muscles) are shown in figure 4.7 as percentages of MVC-recording. The minimal muscle activity for all of the three muscles is during relaxed standing. During bending forward without support, the muscle activity increases proportionally with the bending angle. The usage of the chest support reduces the muscle activity systematically especially in the leg

48

CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY I

muscles. The muscle activity reduces proportionally with increasing height of the support. It is remarkable that increasing of the bending angle barely affect this trend. There was a significant interaction between the angle and height at m. erector spinae (back muscle) (F (1.8, 7.1) = 11.19; p = 0.007). At the leg muscles, there was a significant main effect of height: m. semitendinosus (hamstring) (F (1.0, 4.1) = 18.23; p = 0.012); m. gastrocnemius (calf muscle) (F (1.1, 4.3) = 39.30; p = 0.002).

Figure 4.7 Results EMG-recording

4.1.3.2 Questionnaire The results of the questionnaire completed by seven independent participating surgeons are presented in Table 4.1. The results are divided into four categories: personal information about the subjects, type of surgery, and the positioning of the surgical team during the procedure, total operating time, and time of prototype usage as a percentage of the total operating time, and finally the judgment of the participating surgeons. The ‘‘comfort’’ judgment is based on the extent of overall discomfort reduction using the prototype and the user friendliness of different parts

49

ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

of the prototype. For this subgroups: Overall comfort. Comfort during the use of Comfort during the use of Comfort during the use of

reason, the ‘‘comfort’’ judgment is divided in four

chest support. semi-standing support. the foot pedal.

Table 4.1 Results of the questionnaire Subject Personal

1

2

3

4

5

6

7

Gender

F

F

M

M

F

M

M

Height (m)

1.80

1.66

1.88

1.90

1.60

1.82

1.80

Weight (kg)

77

52

82

85

55

80

80

Surgeon/Resident

R

S

S

R

S

S

R

Procedure Kind of surgery

O

O

O

O

O

MIS

MIS

Positioning surgical team

1

1

2

2

2

3

3

Time of usage of body support Total OR time

270

180

380

380

120

70

80

% OR time

57%

44%

27%**

63%**

68%

22%

25%

Comfort overall

Yes

Yes

Yes

Yes

Yes

No

Yes

Comfort chest support

Yes

Yes

Yes

Yes

Yes

Comfort semi-standing support

Yes

Yes

Yes

Yes

Yes

No

Yes

Yes

Yes

Judgment

Comfort to use foot pedal Restriction of movement***

U

U

U

R

R

R

R

Future use

Yes

Yes

Yes

Yes

Yes

Yes****

Yes

Safety

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Simplicity

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Positioning surgical team

1

2

O = Open surgery MIS = Minimally invasive procedure ** These two surgeons have alternated during the procedure *** U = unrestricted, R = restricted **** After processing his suggestions in the product

50

3

CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY I

4.1.3.3 Electromyography using the prototype The results of the EMG recording for the three measured muscles (erector spinae, semitendinosus, and gastrocnemius muscles) with and without use of the chest support of the prototype are shown in figure 4.8 as percentages of MVIC.

Figure 4.8 Results of electromyography (EMG) recording for one subject (P50-man) with and without the chest support.

The minimal muscle activity for all three muscles occurs during relaxed standing. When the surgeon bends forward without support, the muscle activity increases proportionally with the bending angle. Use of the chest support reduces the muscle activity systematically (Table 4.2). Table 4.2 Reduction of muscle activity during bending forward without chest support. Reduction of muscle activity during bending forward without chest support Forward bending angle with chest support

m. erector spinae

m. semitendinosus

m. gastrocnemius

15º

40 %

26 %

77 %

20º

48 %

14 %

70 %

The results of the EMG recording for the three measured muscles (erector spinae, semitendinosus, and gastrocnemius muscles) with and without the semi-standing support are shown in figure 4.9 as percentages of MVIC. The semi standing support is effective in reducing muscle activity in the leg muscles, especially the calf muscle (Table 4.3).

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

Figure 4.9 Results of electromyography (EMG) recording for one subject (P50) man) with and without the semi-standing support.

Table 4.3 Reduction of muscle activity using the semi standing support. Reduction muscle activity (%) with regard to without semi-standing support

With semistanding support

m. erector spinae

m. semitendinosus

m. gastrocnemius

5%

12 %

50 %

4.1.4 Discussion In general, the risk factors for musculoskeletal injury include non-ergonomic body postures, frequent awkward repetitive movements of the upper extremities, and prolonged static head and back postures. In addition, surgeons experience cardiovascular stress during procedures, and the magnitude of this stress can exceed the level of aerobic physical work performed (Berguer, 1999). The fact that surgeons are performing surgery so concentrated that they tend to neglect their posture increases the need for body support. Our design vision has resulted in the development of an ergonomic body support for surgeons that is suitable for use during both open and minimally invasive procedures. Only a few studies have dealt with support for the surgeons’ body. In a previous study, the design of an ergonomic surgeons chair was discussed, but it did not provide any information about the effect of body support on the reduction of muscle activity (Schurr et al., 1999). The results of our study imply that supporting the body by means of a chest support is effective in reducing the activity of the lower back and leg muscles during open surgery. The desired effect of the chest support is closely related to the optimal height of the support (Albayrak et al., 2006b; Albayrak et al., 2006c). According to the variation in body lengths, the chest support must be adjustable in

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CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY I

a range of 40 cm (0.8 x P5-woman shoulder height and 0.9 x P95- man shoulder height) (Albayrak et al., 2006b; Albayrak et al., 2006c). The semi-standing support shows a trend of reduced leg muscle activity similar to that for the chest support. Conversely, the contribution of the semi-standing support to the reduction in activity of the erector spinae muscle is very limited. Laparoscopy has been adopted in operating rooms without any proper adjustments of their design and layout. Because the current operating tables are originally designed for open surgery, they are not optimal for minimally invasive procedures with regard to ergonomic guidelines. The current operating tables are adjustable in height to between 725 and 1,215 mm (Albayrak et al., 2004). A previous study showed that the discomfort and difficulty ratings were lowest when instruments handles were positioned at elbow height of the surgeon (Berguer et al., 2002). With regard to the guideline of positioning the instruments at elbow height, the ergonomic operating surface height (defined as the navel height of the patient lying on the operating table while the abdomen is filled with carbon dioxide [CO2]) lies between 0.7 and 0.8 of the operator/assistants elbow height (650–1000) (van Veelen et al., 2002b). It is obvious that the current operating tables cannot be adjusted low enough to satisfy ergonomic guidelines. According to Berguer et al., redesigning of surgical tables or the operating room workspace is required to optimize the postural ergonomics of laparoscopy (Berguer et al., 2002). However, this is an expensive and time-consuming approach that may interfere with adoption of this solution by the hospitals. A much cheaper and more effective solution for this problem is to position the surgeon on a height-adjustable platform. The platform of the body support is adjustable in height by means of a motor that can be operated by a remote control. This remote control is packed in a sterile cover, allowing the surgeon to adjust the height of the platform independently of assisting personnel during the procedures. The platform is powered from the main supply, and the height of the platform ranges from 60 mm (minimum) to 460 mm (maximum), meaning that 95% of the user group will have a comfortable posture (in combination with the current operating tables). The semi-standing support at the buttocks has a maximum height of 900 mm when the platform is positioned in the lowest position for a tall surgeon. The height of the semi-standing support is proportional to the height of the platform. This allows optimal placement of this support for the whole user group. Due to the positioning of the equipment during both kinds of procedures, surgeons have a limited space around the operating table for movement, which elicits a static body posture. Taking into account the limited space available in the operating

53

ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

room, the body support must be designed as compactly as possible. The design criteria (body support as compact as possible, comfortable and safe use by 95% of the user group, and sufficient space allowed for positioning of the foot pedal for electro surgery) are contradictory conditions. The platform must be large enough for comfortable and safe standing of a tall surgeon while allowing sufficient space for positioning of the foot pedal. On the other hand, it must be as compact as possible considering the limited space. Nevertheless, a compromise was reached by designing the platform with a diameter of 55 cm. The platform is large enough for a P95 man (tall surgeon) to stand comfortably without falling and for positioning of the foot pedal, yet sufficiently compact to be used in the limited space around the operating table. Despite the compactness of the prototype, all seven participating surgeons indicated that the body support is safe in use. A remarkable outcome of the questionnaire is the dichotomy about the restriction of the movements. However, this cannot be dissociated from the positioning of the surgical team during the procedure. Based on this observation, it may be concluded that the surgeons with a negative opinion were standing very crowded. A point of interest for the designer when users are interacting with products is the experienced level of comfort. Van Veelen et al., reports that surgeons frequently complain about pressure areas as well as pain and fatigue in hand and lower limb joints from manipulation of instruments for minimally invasive surgery (van Veelen et al., 2003a). It should be mentioned that we were particularly interested in one of the interactions between our product and surgeons: leaning against the chest support. This may have consequences for breathing because of the pressure on the chest. Nevertheless, none of the surgeons has experienced discomfort using the chest support. Conclusions The optimum working condition for a surgeon is a compromise between the spine and arm positions and the effort and fatigue of their respective supporting muscular groups. The results of this study imply that supporting the body is an effective way of reducing muscle activity, which over the long term may reduce physical complaints and discomfort. Additionally, the product supports the surgeon in his or her natural posture during both open and minimally invasive procedures while solving working height–related problems of the surgical team. Because of the simplicity in its design and compactness, the ergonomic body support can easily be adopted in the current layout of the operating room.

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CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY II

4.2

Study II: Impact of a activity during forward

chest support on lower back muscles bending

4.2.1 Introduction Recently, Albayrak et al. proposed a new design for an ergonomic body support for surgeons that can be used during open as well as minimally invasive procedures (Albayrak et al., 2007). An important element in this design is a chest support meant to reduce lower back pain by minimizing the lower back muscles activity. During open surgical procedures this muscle activity is caused by surgeons taking a head- and back-bent posture for long periods of time. Such posture leads to enhanced muscle activity to keep the upper body in balance (Albayrak et al., 2006b). This may be regarded as one of the main causes for physical complaints in the lower back during and after open surgical procedures. Theoretically, the reduction in the lower back muscles force causing the increased muscle activity can be described by a biomechanical model (Albayrak et al., 2006b; Albayrak et al., 2006c). Figure 4.10 shows the details of such a model for bending forward while leaning against a chest support. The upper body weight (Fg), the back muscle force (Fm) at the level of L5 (lumbar) and the supporting force (Fsupport) are included in this biomechanical model. Note that the model is limited to the sagittal plane and describes a static equilibrium. A cross-section of the trunk is made at L5-S1 (disc). The mass centre of gravity of the upper body is located near the axillae (Snijders et al., 2004). D = L5 – S1 (disc) = forward bending angle a = distance between the mass centre of gravity of the upper body and the centre of the disc (D) b = distance between the back muscles and the centre of the disc (D) c = distance between the centre of the chest support and the centre of the disc (D) Fg = upper body weight being equal to 65 % of the total body weight (Snijders et al., 2004) Fm = back muscle force Fsupport = supporting force

Figure 4.10 Biomechanical model of bending forward while leaning on a chest support. The reaction forces (Frg, Frm, and Frs) in the disc are not drawn in this model.

55

ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

Considering the equilibrium of moment of forces in the sagittal plane at position D, lower back muscle force Fm can be calculated as follows: Without Support (Fsupport = 0) Fm = Fg . (a/b) With Support (Fsupport 0) Fm = Fg . (a/b) – Fsupport . (c/b)

(Equation 1) (Equation 2)

According to Equation 2 a fore head support might be considered most effective in reducing the muscle force in lower back since distance c is maximal (and thus maximises the factor Fsupport . (c/b)). However, a head support is not desirable since the freedom of movements of the surgeon will reduce dramatically. Furthermore, it will introduce an extra load on the neck. Nevertheless, the upper body should be supported as high as possible. Supporting the upper body at chest height (sternum) is a viable option since the around located tissues mainly have a soft structure. A pressure on the soft tissue due to the supporting force will not be experienced as comfortable. To investigate the viability of the chest support, a prototype was built and tested with five participants (Albayrak et al., 2006b; Albayrak et al., 2006c). The participants were three Dutch females (P5, P50, P95-woman) and two Dutch males ((P50, P95-man), percentiles Dutch population (www.dined.nl, 2004)). The experimental conditions consisted of two bending angles and two different heights of the support, both within the area of the chest. The posture of the participants simulated typical head- and back-bent posture of surgeons during surgical procedures. The muscle activity (electromyography, EMG-recording) in the lower back (right side of m. erector spinae) and right leg (m. gastrocnemius and m. semitendinosus) was measured both with and without using the chest support. The results averaged across the participants showed that muscle activity increases proportionally with the bending angle during bending forward without chest support. The usage of the chest support reduced the muscle activity significantly with a major impact on the leg muscles. This reduction was found to depend on the height of the chest support but the resulting Fm appeared almost independent of the bending angle. According to our biomechanical model the latter would imply that Fsupport is growing proportionally with bending angle . Following Kumar and Mital we assume a monotone increasing relation between muscle force and muscle activity (Kumar & Mital, 1996). The experimental results of the above study are qualitatively in agreement with our biomechanical model predictions for the lower back muscles (Equation 1 and 2) since (1) muscle force Fm, and thus muscle activity, increases with bending angle (or distance a) in the

56

CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY II

condition without support and (2) muscle force Fm decreases when Fsupport is larger than zero. This effect is strengthened by increasing height (c) of the chest support. These conclusions hold for results averaged across subjects. However, the question rose what happens at the individual level? The model in fact incorporates two important anthropometric variables, namely body length in parameters a and c and body weight in parameter Fg. Hence, at individual level an additional prediction can be formulated, namely muscle activity increases with body length and weight. To assess the value of the biomechanical model at individual level, a comparison was made between calculated muscle force and measured muscle activity (EMGrecording) in the lower back during bending forward without support. Using the first equilibrium of moment of forces, the muscle force (Fm) of the five participants was calculated for 1 = 15º, 2 = 20º. Distance b was assumed to be constant at 5 cm (Snijders et al., 2004). In order to normalize the EMG-recordings, the “maximum voluntary isometric contraction” (MVIC) was also measured using manually applied resistance (Kumar & Mital, 1996). The resulting calculated muscle forces Fm in Newton (N), EMG-recordings in microvolt (mV), MVIC-recordings (mV) and Fm expressed in percentage MVIC (% MVIC) can be found in table 4.4. Figure 4.11 shows muscle activity as a function of calculated muscle force for two bending angles. Table 4.4 Calculated muscle force and EMG-recordings, both in absolute values and in %MVIC, for five participants in the condition without support and for two bending angles (15º and 20º). Data have been taken from Albayrak et al. (Albayrak et al., 2006b). Muscle Force (N)

EMG (mV)

Body weight

15º

20 º

15º

20º

1 P5 (F)

50 kg

370

494

54

57

2 P50 (F)

70 kg

580

767

33

3 P95 (F)

76 kg

674

892

4 P50 (M)

80 kg

670

5 P95 (M)

90 kg

865

Participants

MVIC (mV)

% MVIC 15º

20º

60

90

95

34

60

55

56

17

20

75

22

26

885

36

39

86

41

45

1144

26

31

92

28

33

F = female, M = male

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

100

P5 (F) P50 (F) P95 (F) P50 (M) P95 (M)

90 80 70 60 50 40 30 20 10 0 250

450

650

850

1050

Calculated muscle force (N) Figure 4.11 Measured EMG-recording, expressed in %MVIC, as a function of muscle force in the lower back calculated according to the biomechanical model without support (Equation 1) for two bending angles. The characteristics of the subjects are presented in Table 4.4.

The biomechanical model appears to predict the conditions within subjects correctly but has some limitations in predicting the observed differences in muscle activity between subjects. Surprisingly, the measured muscle activity (%MVIC) seems to decrease with increasing body length and weight (and hence muscle force) for females as well as males. Interestingly, similar deviations of biomechanical modelling have been reported by others (Arjmand & Shirazi-Adl, 2005, 2006; Granata & Marras, 1995). As a possible explanation, Granata and Marras suggested that appropriate representation of muscle area is essential to the validity and performance of biomechanical models, because muscle force per unit area is highly variable between subjects, depending on participant condition and natural ability (Granata & Marras, 1995). Arjmand and Shirazi-Adl noted that in biomechanical models of trunk load the balance of net external moments is considered only at one cross-section rather than along the entire length of the spine (Arjmand & ShiraziAdl, 2006). Moreover, the evaluated muscle forces, once applied on the system along with external loads, may not necessarily generate the same spinal kinematics under which they were initially calculated (Arjmand & Shirazi-Adl, 2006). Hence, due to their static and two-dimensional approach, biomechanical models seem to have some limitations in predicting conditions between subjects. Nevertheless, biomechanical models are useful to predict conditions within subjects.

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CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY II

Introduction of a chest support into the biomechanical model makes a univocal prediction of the related conditions even more difficult because Fsupport in Equation 2 is not known beforehand. It is an uncertain factor because it depends on how much the participants trust the chest support and are prepared to lean on it. One possible way to assess the value of Fsupport is by comparing muscle activity with and without chest support. To this end, an assumption has to be made about the quantitative relation between muscle activity and force. Considering the relationship observed by Bendix et al. and Kumar and Mital a linear function between EMGrecording (E) and calculated muscle force (Fm) seems to be a good first-order approximation (Bendix et al., 1985; Kumar & Mital, 1996), or E = m . Fm + n, (Equation where m and n are constants. Then, the following relation holds for the condition without support EWOS = m . Fg .(a/b) + n, (Equation and the following relation for the condition with support EWS = m . Fg . (a/b) - Fsupport . (c/b) + n, (Equation with EWOS and EWS being actual EMG-recordings under similar conditions (bending angle and height of the support). Then, Fsupport can be estimated by subtracting eq. 4 from eq. 5 resulting in the following expression Fsupport = (EWOS - EWS) . b/(m . c) (Equation

3)

4) 5)

6)

To evaluate these equations, a similar experimental set-up was used as in Albayrak et al. (2006a; 2007), except that the range of bending angles was extended to larger degrees. The maximum angle was raised from 20º to 40º. Additionally, the number of participants was increased such that the total range of body lengths was extended substantially. Finally, the number of muscles on which EMG-recording was performed was increased to five: two muscles in the lower back, one in the abdomen and two in the right leg. This was done since there are indications that humans tend to follow different balancing strategies during a standing posture (Winter, 1995). This will be reflected in the pattern of EMG-recordings from these five muscles. In this way, a possible relation between Fsupport and the kind of balancing strategy a person is adopting in the current set-up might be established. The aim of the present study is to investigate how individual subjects make use of a chest support and to study the influence on lower back muscle activity during forward bending.

59

ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

4.2.2 Materials and methods 4.2.2.1 Participants In total sixteen healthy volunteers were participating in this study. Nine of the participants were female (age 26.3 ± 2.4 yr; average length 1.66m, range minmax 1.52-1.77m; body mass 63.2 ± 12.4 kg) and 7 male (age 28.8 ± 5.3 yr; average length 1.79m, range min-max 1.70-1.92; body mass 75.9 ± 12.1 kg). The percentiles of the participants were for females; P96, P91, P85, P77, P67, P43, P26, P17, P2 and for males; P98, P76, P47, P35, P24, P15, P7 (www.dined.nl, 2004). 4.2.2.2 Protocol A prototype of a chest support was used during the experiment. The chest support was adjustable in height and bending angle. The chest support was revolving on its vertical axis (figure 4.12).

Revolving chest support Height adjustment

Bending adjustment

Figure 4.12 Experimental set-up chest support.

The muscle activities of the participants were measured by means of EMG-recording while they were bending forward with their hands in their waists. All participants followed the same protocol (P) consisting of thirteen conditions. Each condition was performed during 10 seconds, followed by 15 seconds rest. Each condition was repeated three times and the average value was determined.

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CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY II

The conditions of the protocol were: P1; relaxed standing P2; bending forward without support at angle 1 P3; bending forward without support at angle 2 P4; bending forward without support at angle 3 P5; bending forward without support at angle 4 P6; bending forward with support at angle 1 and height h1 P7; bending forward with support at angle 1 and height h2 P8; bending forward with support at angle 2 and height h2 P9; bending forward with support at angle 2 and height h1 P10; bending forward with support at angle 3 and height h1 P11; bending forward with support at angle 3 and height h2 P12; bending forward with support at angle 4 and height h2 P13; bending forward with support at angle 4 and height h1 Height h1 was defined as 0.8 x shoulder height and h2 as 0.9 x shoulder height. Angles 1, 2, 3, 4 were 15º, 20º, 30º, 40º respectively. 4.2.2.3 EMG-recording A selected muscle group was examined in the lab by means of EMG-recording. In order to normalize the data for comparison, also the “maximum voluntary isometric contraction” (MVIC) was measured (Kumar & Mital, 1996). MVIC’s were all obtained with manually applied resistance. Prior to attaching the electrodes, the skin was grated and then cleaned with alcohol. A reference electrode was placed on the left wrist. For the MVIC- and EMG-recordings, a portable physiological measurement system, type Porti 5-16/ASD of TMS International B.V. (Enschede, The Nederlands) was used. The Ag/AgCl surface electrodes with recessed pre-gelled (hydrogel) elements (GE Medical Systems Accessories Europe) were used to collect the MVIC and EMG signals. The raw EMG signals (DC frequency, ~2 kHz) were processed electronically with a sample rate of 1000 Hz, and the cut-off frequency was 10 ± 200 Hz. The following muscles were examined: m. erector spinae (lower back muscles, both sides at about 2 cm from the midline at the level of L5-S1, (Snijders et al., 1998). m. rectus abdominis (abdominal muscle, 2 cm lateral to midline at the level of the umbilicus, (Snijders et al., 1998). m. semitendinosus (hamstring in the right leg). m. gastrocnemius (calf muscle, caput mediale in the right leg). The software program SPSS 12.0.1 for Windows is used to analyse the results statistically.

61

ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

4.2.3 Results 4.2.3.1 EMG-recording; general Figure 4.13 shows the results of the EMG-recording averaged across all participants as a function of bending angle for each muscle separately.

Figure 4.13 Results of EMG-recording averaged across all participants. Note that scales for muscle activity differ between muscles.

62

CHAPTER 4: DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND EVALUATION, STUDY II

On average, the muscle activity during relaxed standing is 6 %MVIC. The minimal muscle activity for all measured muscles except for m. gastrocnemius is during relaxed standing. During bending forward without support, in general muscle activity increases proportionally with the bending angle. The only exception is m. rectus abdominis where the muscle activity stays at the relaxed standing level. The usage of the chest support reduces muscle activity for all angles with again the exception of m. rectus abdominis where the muscle activity tends to increase. To analyse the general findings statistically, a three-way full factorial within subjects repeated measures ANOVA was conducted with main effects: muscle (5) x angle (4) x height (3; without support and with support at two heights). The results of this analysis are shown in table 4.5. All the main effects and interaction effects turn out to be significant. Table 4.5 Results of full factorial ANOVA within subjects repeated measures.

Source

df

df error

Mean square

F

Sig.

Muscle

4.00

60

3175.83

11.49

.000

Height

1.16

17.47

10796.24

44.70

.000

Angle

1.87

28.11

4390.17

79.82

.000

Muscle * Height

2.04

30.62

6011.18

26.12

.000

Muscle * Angle

3.94

59.23

767.07

11.84

.000

Height * Angle

2.95

44.25

204.66

6.98

.001

Muscle * Height * Angle

5.96

89.52

92.56

2.57

.024

Main effects Regarding the main effect muscle, both sides of m. erector spinae show most muscle activity (right side; 17.51 %MVIC and left side; 15.98 %MVIC). The least muscle activity was measured at m. rectus abdominis (7.28 %MVIC). The muscle activity of m. semitendinosus and m. gastrocnemius was 11.42 and 11.60 %MVIC, respectively. The activity of the lower back muscles differs significantly from that of the m. rectus abdominis. Regarding the main effect height, the muscle activity during bending forward without support (17.86 %MVIC) is significantly higher than with support (height h1 and h2: 10.57 and 9.85 %MVIC respectively). Although, the muscle activity during bending forward with support on height h2 was systematically lower than on height h1, this difference was non-significant. Regarding the main effect angle, the muscle activity increases systematically with the bending angle: 9.56, 10.76, 13.54 and 17.17 %MVIC at 150, 200, 300 and 400 respectively. The muscle activity at the four angles differs significantly from each other.

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

Interaction effects The interaction between muscle and height is mainly caused by the different ways the muscles react on the usage of the support. The activity of m. erector spinae at both sides reduces gradually to a value of 77% of the activity without support; this value is measured for height h2. Much larger reductions have been found for the leg muscles towards 37% for m. semitendinosus and 19% for m. gastrocnemius. The activity of the m. rectus abdominis increased by 25%. The interaction between muscle and angle can be attributed to the angle at which the different muscles recruited: both sides of m. erector spinae at 150, the m. semitendinosus at 200 and the m. gastrocnemius at 300. The activity of m. rectus abdominis hardly changes with the angle. Finally, the interaction between height and angle can be attributed to increasing difference between muscle activity without support and with support as a function of angle. 4.2.3.2 EMG-recording; per muscle Table 4.6 shows the results of two-way full factorial within subjects repeated measures ANOVA per muscle with main effects angle (4) and height (3). Table 4.6 Results of full factorial ANOVA within subjects repeated measures per muscle.

Source

df

df error

Mean square

F

Sig.

m. erector spinae (right side) Main effect Interaction

Height

1.43

21.49

437.19

13.34

.001

Angle

1.63

24.48

2178.93

59.7

.000

Height * Angle

3.58

53.83

25.85

2.82

.038

Height

2

30

337.09

23.57

.000

Angle

1.31

19.66

2343.65

49.45

.000

Height * Angle

6

90

18.65

5.34

.000

Height

2

30

40.79

7.65

.002

Angle

1.57

23.57

19.21

6.01

.012

Height * Angle

2.35

35.33

5.66

1.66

.201

Height

1.13

16.98

5500.89

28.54

.000

Angle

1.66

25.02

2554.54

37.74

.000

Height * Angle

2.47

37.08

146.99

3.16

.044

Height

1.03

15.47

16711.36

38.58

.000

Angle

1.63

24.56

205.37

2.82

.088

Height * Angle

2.65

39.84

216.39

4.61

.009

m. erector spinae (left side) Main effect Interaction

m. rectus abdominis Main effect Interaction

m. semitendinosus Main effect Interaction

m. gastrocnemius Main effect Interaction

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The measured muscle activity of m. erector spinae at both sides shows a similar pattern (figure 4.13). The minimal muscle activity at both sides is during relaxed standing ( 6 %MVIC). The significant interaction effect is caused by the finding that at 150 the muscle activity without support equals almost the activity with support at height h1 whereas at the other angles the main reduction in muscle activity occurred between these two conditions. The measured activity of m. rectus abdominis remains at the level of relaxed standing for all angles when no support was used. Contrary to the other muscles, the activity increases when the support is used. For all angles, the activity at height h1 is larger than at height h2. There was no interaction effect. The minimal activity of m. semitendinosus is during relaxed standing and at conditions with support at 150 and 200. Without support, muscle activity increases proportionally with the bending angle. With support the muscle activity is recruited starting from 300. The significant interaction effect between height and angle can be attributed to this difference in the angle at which the muscle is recruited in the conditions with and without support. The activity of m. gastrocnemius increases with the bending angle during bending forward without support. Surprisingly, the muscle activity during all conditions is below the activity level at relaxed standing. The interaction is caused by the fact that activity with support is not changing with angle whereas activity without support increases as a function of the angle. 4.2.3.3 EMG-recording; individual level A hierarchical cluster analysis was conducted on the EMG-recording of the five muscles to identify users with similar patterns in muscle activity. This resulted in three clusters. The average data of these clusters can be found in figure 4.14. Cluster 1 represents the largest group consisting of thirteen participants. The three remaining participants had a deviant pattern and were divided in Cluster 2 (two participants) and Cluster 3 (one participant). In figure 4.14 the EMG-recordings of the measured muscles are represented in two parts with the left part representing the conditions during relaxed standing (RS) and without support and the right part the conditions using the chest support (WS = with support). The measurements for the two different heights belonging to the same bending angle were averaged.

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

Figure 4.14 EMG-recording of the measured muscles per protocol condition. Left-hand panel: conditions during relaxed standing (RS). Right-hand panel: conditions using the chest support (WS = with support). The measurements for the two different heights belonging to the same bending angle were averaged.

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The main difference between Cluster 1 and Cluster 2 in the condition without support is the activity of the two leg muscles. In Cluster 1, the activities in these muscles increase systematically with the bending angle. In Cluster 2, only the m. gastrocnemius is increasingly active at 150 and 200 and decreases in activity at 300 and 400, while at the same time the activity of m. semitendinosus increases. Most characteristic aspect of Cluster 3 is the high activity of the two leg muscles with respect to the relatively low activity of the lower back muscles. The main difference between Cluster 1 and Cluster 2 in the condition with support is that the effect of the chest support on the lower back muscle activity is relatively small in cluster 2. Furthermore, the sudden increase of m. semitendinosus for Cluster 2 at 300 is remarkable. Finally Cluster 3, all the muscle activities seem hardly to deviate from that at relaxed standing except for 400. 4.2.3.4 EMG-recording and the biomechanical model Figure 4.15 shows, per cluster, the measured EMG-recording, expressed in %MVIC, as a function of muscle force in the lower back (m. erector spinae (right side)) calculated according to the biomechanical model without support for four bending angles. 35 30 25 20 15 10

Cluster1 Cluster2 Cluster3

5 0 0

500

1000

1500

2000

2500

Calculated muscle force (N) Figure 4.15 Measured EMG-recording, expressed in % MVIC, as a function of muscle force in the lower back calculated according to the biomechanical model without support (Equation 1) for four bending angles. The data for Cluster 1 and 2 are the averages across participants. The equations for the fitted regression lines are: Cluster 1; EMG = 2.8 (SD ± 6.1) + 0.016 Fm (SD ± 0.009) (Adjusted R2 = .99) Cluster 2; EMG = 13.98 (SD ± 7.53) + 0.017 Fm (SD ± 0.006) (Adjusted R2 = .99) Cluster 3; EMG = 17.91 + 0.003 Fm (Adjusted R2 = .93).

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In each cluster the averaged data appear to lie on a straight line as conformed by the linear regressions. Furthermore, figure 6 shows that the data of the different clusters do not overlap. Data of Cluster 1 and 2 show a parallel shift. The characteristic for the participant of Cluster 3 is the little variation of muscle activity with respect to the model prediction. The main suggestion from this figure is that each overall pattern of muscle activity needed for balancing the body results in a different relation between measured muscle activity and model prediction for lower back muscle. The observed linearity on the average level also holds on the individual level. After analysis of the individual data for Cluster 1, no systematic effect of P-value (comprising body length) on the relation between muscle activity and model prediction could be observed contrary to what was found in the previous study (figure 4.11). Furthermore, the range of measured and predicted values between individuals was rather small. No systematic differences between males and females were found. Estimated supporting force In the introduction it was suggested that different balancing strategies will affect the way the chest support is used. In other words, one may expect the three clusters to generate different relations between Fsupport and bending angle. To assess the degree of use of the chest support by the participants, an estimation of the supporting force was made by subtracting the muscle activity without support from the muscle activity with support. According to equation 6 this should results in an estimate of the Fsupport besides a multiplication factor. This factor was determined from the linear regression in figure 6 (parameter m) and the height of the chest support (parameter c) while the value of parameter b was fixed at 5 cm. Figure 4.16 denotes the resulting Fsupport as a function of the bending angle . In addition, figure 4.16 shows the outcome of the linear regression per cluster.

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120

100

80

Cluster 1 (height 1) Cluster 1 (height 2) Cluster 2 (height 1)

60

Cluster 2 (height 2) Cluster 3 (height 1) 40

Cluster 3 (height 2)

20

0 0 -20

5

10

15

20

25

30

35

40

45

Bending angle (degree)

Figure 4.16 Estimated supporting force per cluster and height at corresponding bending angles (Equation 6). The equations for the fitted regression lines are: Cluster 1; Fsupport = 2.92 + 0.28 (Adjusted R2 = .48) Cluster 2; Fsupport = -15.79 + 0.44 (Adjusted R2 = .51) Cluster 3; Fsupport = 96.91 - 0.06 (Adjusted R2 = .003)

Cluster 1 (representing the majority of the participants) and Cluster 2 show a similar pattern in that the estimated supporting force increases linearly with bending angle. The difference between these clusters is that for Cluster 1 Fsupport is always positive while for Cluster 2 it is mostly negative becoming neutral at 400. Apparently, the participants of Cluster 1 increasingly rely on the chest support. The little variation of the estimated supporting force within Cluster 1 suggests a limited use of the chest support. The negative value of Fsupport for Cluster 2 indicates that these two participants hardly made use of the chest support. The main exception is the participant of Cluster 3: first, the estimated Fsupport is independent of the bending angle, and second the value of Fsupport is significantly higher than that of the other participants. Apparently, this participant makes strong use of the chest support.

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4.2.4 Discussion During surgical procedures due to work related circumstances such as positioning of the patient on the operating table and/or equipment in the operating room, surgeons have an ergonomically poor body posture; head-bent and back-bent posture. Beside surgeons there are many other professions contending with similar problems due to poor body posture. Dentists, fruit or flower pickers, and car mechanics for example have a comparable head-bent and back-bent posture. Rohlmann et al. indicate that the load of the trunk is significantly increased during flexion of the upper body (Rohlmann et al., 2001). During flexion of the upper part of the body while standing, the pressure in the disc increased almost nearly to 216% (the intradiscal pressure was 0.50 MPa on average for standing). This value was set to 100% and the values for all activities are related to it for 36º between the thoracolumbar junction and the sacrum (Rohlmann et al., 2001). Maintaining the poor body posture for long periods of time results in musculoskeletal fatigue and experience of physical complaints. The results of our study imply that supporting the body by means of a chest support is effective in reducing muscle activity in the lower back and especially in leg muscles during bending forward. The significant interaction between height and angle in the measured muscles except for m. rectus abdominis shows that both height and angle of the support affects the muscle activity. Optimal adjustment of height and angle is therefore essential for the desired effect of the chest support. Providing the chest support in professions with similar body posture as mentioned above might reduce discomfort. Considering the results per muscle, the activity of m. erector spinae (both sides) during all conditions is highest compared with other measured muscles (figure 4.13). This indicates that participants mainly use their lower back muscles during bending forward. It seems that up to 300 the activity of the lower back muscles is sufficient to keep the upper body in balance. With increasing bending angle the m. semitendinosus is recruited to support the lower back muscles. Using the chest support the muscle activity of m. gastrocnemius is even lower than during relaxed standing. Despite the different roles the four muscles are playing in balancing the body, the chest support is effective to reduce the activity of these muscles. An aberration appears at m. rectus abdominis. The usage of the chest support is accompanied by increasing muscle activity of m. rectus abdominis. A possible explanation is that m. rectus abdominis activity counteract hollowing of the lumbar spine. According to Allison and Henry, the predominant muscle action of the three most superficial abdominal muscles (the Obliques and Rectus) have been associated with predominantly trunk flexion activities with or without combined rotation (Allison & Henry, 2001). In this study, also the role of the co-activation of the antagonists (three most superficial abdominal muscles) in the spinal stability is indicated.

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One parameter with the potential to influence spinal mechanics and stability is intra-abdominal pressure (IAP). IAP has the potential to substantially unload the spine in standing and flexion tasks, a role that depends directly on the IAP magnitude and concurrent level of co-activity in abdominal muscles (Arjmand & Shirazi-Adl, 2005). That is, IAP could indeed even increase the back-muscle forces when large co-activity is generated in the superficial abdominal muscles (the Obliques and Rectus) (Arjmand & Shirazi-Adl, 2005). It seems that m. rectus abdominis is playing a role in the spinal stability. Correspondingly, Juker et al., advocated that muscles of the abdominal wall (rectus abdominis, external oblique, internal oblique, transverse abdominis) and psoas play a fundamental role for the normal functioning of the lumbar spine (Juker et al., 1998). Although identifying individual differences was impossible, the cluster analysis distinguishes (figure 4.14) three user groups regarding their balancing strategies. The participants of Cluster 1 can be mentioned as “sceptical users”. During bending forward without chest support the muscle activity, except the m. rectus abdominis, increases proportionally with the bending angle. The slightly reduction of the muscle activity in the right part of the figure confirms the actually usage of the chest support. The pattern of behaviour of participants in Cluster 1 was characterized by simultaneously recruiting all the measured muscles except for m. rectus abdominis. However, the limited decrease in the back muscle activity indicates that participants in this cluster are sceptical about the chest support whereby they partially manage the balancing of the upper body by themselves. The little variation of the estimated supporting force within Cluster 1 suggests a limited use of the chest support. However, the reduced muscle activity in the leg muscles indicates that the subjects of Cluster 1 are standing relaxed during the use of the chest support. The second cluster can be identified as “non-trusters”. During bending forward without support, primarily the m. erector spinae (both sides) and the m. gastrocnemius are active to keep the upper body in balance. It is obvious that the participants in this cluster are changed their balance strategy after the bending angle of 20º. Hereby a reduction of the m. gastrocnemius is accompanied by an increased activity of the m. semitendinosus. Focusing on the part with support it becomes clear that the usage of the chest support is not optimal. Reduction of the muscle activity, especially in the m. erector spinae is minimal. Even after reaching the bending angle of 20º, the activity of the m. semitendinosus increases dramatically to keep the upper body in balance. The participants of Cluster 2 primarily used the m. erector spinae during bending forward. However, recruiting of m. semitendinosus after reaching the bending angle of 20º indicates the necessity of additional muscle activity at increasing bending angles to keep the upper body in balance. The minimal reduction of the muscle activity indicates that participants of

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this cluster entirely do not trust the chest support. The negative value of the estimated supporting force indicates that these two participants of Cluster 2 hardly made use of the chest support. The participant in the last cluster can be classified as “fully-truster”. The participant in this cluster is keeping the upper body in balance principally with the m. semitendinosus and m. gastrocnemius during bending forward without support. During bending forward with support the muscle activity in all the muscles is decreased dramatically, which shows that the participant trust the chest support totally by leaning against it. An aberration of m. semitendinosus occurs during bending forward with support at 40º. However, recruiting of this muscle is not significant for the behaviour of this participant since the muscle activity is still below the activity without support. With regard to simultaneously recruiting of muscles, Cluster 3 shows similarities with cluster 1. However, in Cluster 3 the activity of m. erector spinae is clearly lower than the activity of leg muscles, indicating the balancing role of the leg muscles during bending forward. Apparently, this participant makes strong use of the chest support since the estimated supporting force is significantly higher than that of the other participants. Humans tend to follow different balancing strategies during a standing posture. Winter describes three strategies (ankle, hip and combined) in relation to displacement of the centre of mass (COM) in an inverted pendulum model of balance in the anteroposterior (A/P) direction (Winter, 1995). The ankle strategy applies in quiet stance and during small perturbations and predicts that the ankle plantar flexors/dorsi flexors alone act to control the inverted pendulum. In more perturbed situations or when the ankle muscles cannot act, a hip strategy would respond to flex the hip, thus moving COM posteriorly, or to extend the hip to move the COM anteriorly. Using a computer simulation the displacement of the COM at each of these strategies was measured. A 10 Nm (Newton meter) ankle moment was applied for 300 ms. The total body COM displacement (posterior) was estimated to be 1.56 cm. The same 10 Nm was applied as hip flexors to stimulate a hip strategy and the posterior displacement of the COM was 2.04 cm. However, a combined ankle and hip strategy was quite possible and with a 10 Nm plantar flexor moment plus a 10 Nm hip flexor moment the COM displaced 3.53 cm after 300 ms (Winter, 1995). The pattern of muscle activity of the identified user groups in the current study are in agreement with the findings of Winter (Winter, 1995). Since the activity of the m. gastrocnemius is the highest compared with other muscles during relaxed standing (figure 4.13), the ankle strategy applies in quiet stance. The participants of Cluster 1 were defined as “sceptical users”. Regarding the simultaneously recruiting of the lower back and leg muscles and limited use of the chest support, it is clear that the participants of Cluster 1 use the combined strategy for balance. Cluster 2 was characterized as “non trusters”. It seems that

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the two participants of this cluster hardly made use of the chest support and adopting the hip strategy since primarily the m. erector spinae is involved for balancing. Conversely, the participant of Cluster 3, defined as “fully-truster”, balances the body using the ankle strategy since mainly the leg muscles are recruited. Conclusions Supporting the body by means of a chest support shows a systematic reduction of muscle activity in the lower back and leg muscles. Identifying three user groups with corresponding balance strategies indicate the variety within the pattern of behaviour of individuals. Measuring the activity of multiply muscles by means of EMG-recording is needed to identify the pattern of behaviour of users. Although the experimental conditions were the same, humans tend to follow different balancing strategies. An advice for product designers is therefore that it is valuable taking the anthropometry and the conditions of the users into account to meet their specific needs. However, not only the anthropometric characteristics of individuals during product development for supporting purposes need to be considered but also the possibility for altering the posture and preferably avoid constraining the user to a certain body posture. Acknowledgement The authors would like to acknowledge the contribution of the company “Professional Health Design” directed by M.A. van Veelen for providing the prototype of the chest support for this study.

73

This chapter is based on the following articles: Albayrak A, Casseres YA, de Ridder H, Goossens RHM, Kazemier G, Meijer DW, and Bonjer HJ. subjective evaluation of image quality during minimally invasive surgery. Submitted (2008).

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Objective and

CHAPTER 5 IMAGE QUALITY DURING LAPAROSCOPIC SURGERY

The technology that surgeons use nowadays to perform minimally invasive surgery (MIS) appears to cause problems for many surgeons resulting in higher complication rates compared to open surgery. Some of these problems are intrinsic to laparoscopic viewing that degrade the surgical quality and enhance the probability of error during surgical procedures such as loss of three-dimensional depth perception, scaling difficulties caused by the magnification of the operating field and by definition degraded visual image of the anatomy (compared to the experience during open surgery). One of the main problems is lack of national standards for inspection and maintenance of equipment and instruments, responsible for creating a good and adequate image. In the current study, the focus will be on the quality of the “imaging chain” during a specific but representative type of MIS, namely laparoscopy. This chapter discuss the study of objective and subjective evaluation of image quality in 36 Dutch hospitals.

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5.1

INTRODUCTION

Minimally Invasive Surgery (MIS) has improved recovery after surgical procedures because of its many advantages for the patient such as reduced postoperative pain, fewer wound-related infections, shorter recovery time and better cosmetics results (Frank et al., 1997). At the same time, MIS has altered the way surgeons interact with the surgical field and the patient, not only physically but also at a cognitive level, requiring additional visual motor and learning skills besides the traditional surgical and medical skills (Berguer, 1999). MIS is more technology-dependent than open surgery since more equipment is needed to perform the same surgical procedure. Furthermore, since the introduction of MIS in the mid 80’s, the main focus has been on technology with less concern about ergonomics (Gallagher & Smith, 2003). The technology that surgeons use nowadays to perform MIS appears to cause problems for many surgeons resulting in higher complication rates compared to open surgery. Some of these problems are intrinsic to laparoscopic viewing that degrade the surgical quality and enhance the probability of error during surgical procedures such as loss of three-dimensional depth perception, scaling difficulties caused by the magnification of the operating field and by definition degraded visual image of the anatomy (compared to the experience during open surgery) (Gallagher & Smith, 2003). A recently published report by the Dutch Inspection of Health Services “The underestimated risks of minimally invasive surgery” contains a list of potential problems threatening patient safety (IGZ, 2007). One of the main problems is lack of national standards for inspection and maintenance of equipment and instruments, responsible for creating a good and adequate image. In the current study, the focus will be on the quality of the “imaging chain” during a specific but representative type of MIS, namely laparoscopy. 5.1.1 The imaging chain The surgical team observes the operative field indirectly via an image on a monitor. In order to generate the monitor image two procedures have to be combined. Firstly, the dark abdominal cavity has to be illuminated. Secondly, the image of the illuminated abdominal cavity has to be captured, transmitted to, and displayed on the monitor screen. The system combining these procedures is known as the “imaging chain” and consists of the following basic components; (1) light source, light guide cable and fibre optic channel of the endoscope to illuminate the abdominal cavity; (2) imaging optics of the endoscope, camera, camera controller and monitor to display the image of the illuminated abdominal cavity on the monitor (Swaitzberg, 2001). The imaging optics are positioned in the centre of the endoscope with optic light fibres located in the periphery (Boppart et al., 1999). To illuminate the abdominal cavity the light from the light source is transmitted

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through the light guide cable and the fibre optic channel of the endoscope. Both light guide cables and endoscopes contain glass fibres to transmit light. In spite of the high transmission coefficient of these glass fibres, reduction of loss in light occurs in the delivery system (light source, light guide cable, and endoscope) due to: Differences of diameters on the connection of the light guide cable with the light source (different brands). Differences of diameter between the light guide cable and the endoscope. Surface losses and bulb absorption. Because of these losses, the light transmission of this part of the imaging channel is reduced to at most 20 percent in the best imaging system. As a result of all the losses, a typical system will deliver considerably less then 1 W of visible light from a 250 W source lamp (Frank et al., 1997). Additionally, loss of illumination is caused by aging of the light source, mechanical damage due to repetitive use and sterilization of light guide cables and endoscopes resulting in melting and/or breakage of fibres. Melted or broken fibres reduce the illuminance of the abdominal cavity. The illuminance of the abdominal cavity is determined by the output of the light source and the quality of light transmission of the light guide cable and endoscope. In other words, the total illuminance of the imaging chain is a product of the transmission of the light guide cable, the transmission of the endoscope and the output of the light source (Albayrak et al., 2006a). Albayrak et al. showed that the total illuminance of the abdominal cavity was significantly correlated with these components (Albayrak et al., 2006a). Once the light enters the abdominal cavity, the luminance is not constant as a consequence of differences in the way organs and tissues scatter light. Human tissues and organs could be categorized on the basis of their luminosity into three basic groups: high luminous tissues such as fat, the stomach and the bowel; medium-luminous organs such as diaphragm and gallbladder; and dark, mostly parenchymatous with high blood contents organs such as the liver and the spleen (Danis, 1998). Luminous tissue will reflect the light and illuminates the screen intensely and conversely, dark tissue will absorb the light and reduce the brightness of the image. The abdominal cavity is illuminated and the resulting image is captured, transmitted to, and displayed on the monitor. The image quality is determined by three major parameters; image resolution, luminance and chroma (Hanna & Cuschieri, 2001). The image resolution determines the visibility of details in the image and refers to the sharpness and contrast of the picture (Berber et al., 2002). Luminance refers to the amount of light available in the image signal and chroma

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ERGONOMICS IN THE OPERATING ROOM: TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

denotes the colour intensity or saturation (Hanna & Cuschieri, 2001). The monitor has a vertical and horizontal resolution that quantifies how close lines (alternating black and white lines) can be to each other and still be visibly resolved. The standard monitors can resolve 600 lines and the monitor is literally the rate-limiting step in improving image resolution (Berber & Siperstein, 2001). Additionally, the vertical resolution is fixed at the number of scanning lines that the system uses, but the horizontal resolution is changeable, depending on the quality of the camera, wiring and the monitor (Berber et al., 2002). 5.1.2 Ergonomics From a perspective of cognitive interaction between the surgeon and the observed surgical field, there are several factors intrinsic to laparoscopic viewing that may degrade the surgical quality and enhance the probability of error during surgical procedures. Since the surgical team observes the surgical field via a monitor, direct sensory perception and feedback are almost nil. Representation of a threedimensional environment on a two-dimensional screen has reduced the depth perception to a set of only monocular (pictorial) depth cues of the surgical field to the surgical team (Hanna & Cuschieri, 2001). Despite the reduced depth perception, the human visual system is still capable of making effective depth inferences from flat images by using visual cues such as texture gradients and shadows provided that that abdominal cavity is well illuminated (Frank et al., 1997). Good illumination will reduce the occurrence of incorrect inferences from the observed monitor image. For example, when surgeons inspect the gallbladder and surrounding structures to identify the cystic duct, the surgeon’s brain seeks a pattern to match his/her mental model of the biliary anatomy stored in long-term memory (Way et al., 2003). The match between the mental model and the observed patterns, which are recorded by the visual system, are simplifications and the visual perception provides therefore an estimate of reality, not an exact copy. Way et.al., showed that 97% of the primary cause of error of bile duct injuries stems principally from a misinterpretation of the anatomy as a result of visual perceptual illusion (Way et al., 2003). Technical flaws were present in only 3% of the injuries. They also provide a list with rules of thumb to help prevent bile duct injuries (Way et al., 2003). Optimizing the image by using a high-quality imaging system is one of the recommendations. This is essential since the imaging system connecting “the eye” of the surgeon to the surgical field during MIS. Hanna et.al., showed that task performance of the surgeon is significantly degraded by current video-endoscopic imaging systems compared to direct binocular vision (like during open surgery) (Hanna & Cuschieri, 2001). Therefore, high quality image is of paramount importance to allow safe and effective surgical procedures.

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No studies were identified dealing with the subjective and objective image quality in practice. The studies, which were found, were based on lab-settings and not carried out in the operating room. Therefore, the aim of this study is to asses the quality of illumination of the abdominal cavity by examining the transmission characteristics of light guide cables and endoscopes. The objective measurements are performed in a representative sample of hospitals in the Netherlands. In addition, the correlation between illumination of the abdominal cavity and surgeons’ subjective experience of this image was established.

5.2

MATERIALS AND METHODS

5.2.1 Selection of hospitals In 2003 and 2004, 36 Dutch hospitals were visited: 5 academic hospitals, 17 teaching hospitals and 13 community hospitals. These hospitals were selected out of 92 hospitals in the Netherlands. 5.2.2 Attended procedures In total 65 minimally invasive procedures were attended. The type and number of attended procedures are representative for the Dutch hospitals (www.nvec.nl, 2004). Figure 5.1 shows the registered national number of surgical procedures in the Netherlands and the number of attended procedures (www.nvec.nl, 2004). Lap. Appendicectomy, 1086 Attended 0 procedures Lap. Splenectomy, 70 Attended 2 procedures

Lap. Cholecystectomy Others, 170 Attended 8 procedures

Lap. Hernia repair Lap. Splenectomy Lap. Appendicectomy Others

Lap. Hernia repair, 999 Attended 14 procedures

Lap. Cholecystectomy, 11109 Attended 37 procedures

Figure 5.1 The registered national number of surgical procedures in the Netherlands and the number of attended procedures (2004).

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5.2.3 Measurements 5.2.3.1 Objective In this study, two different objective measurements were carried out: The illuminance (I) by the imaging chain has been measured using a digital luxmeter (LX-107; LT Lutron, Taiwan) and is expressed in [lux]. The underlying formula for this measurement is; ITOT = ILS . TE . TLGC. In words, total illuminance (ITOT) of the imaging chain is a product of the output of the light source and the light transmission coefficients of the endoscope and the light guide cable. The resolution (RTOT) of the imaging chain and that of the endoscope (RE) have been measured using a Borescope Test Chart (Olympus Industrial) and expressed by lines per mm (l/mm). 5.2.3.2 Subjective A questionnaire was used to asses the subjective impression of the surgeon of the displayed image during the procedure. To this end, the surgeon was asked to judge, immediately after finishing the surgical procedure, the image on the following items: overall image quality (Q), sharpness (S), contrast (C), brightness (B), and quality of colour (CL). A numerical scale of 1 to 10 was used to express the judgments. 5.2.3.3 Setting The measurements of the imaging chain took place in two settings; In the operating room immediately after a procedure. In the sterilization department at an arbitrary moment during the visit. In the operating room, both objective and subjective measurements took place. In the sterilization department only objective measurements were done. Operating room Immediately after a procedure was finished total illuminance (ITOT) as produced by the imaging chain during that procedure was measured before the light guide cable and the endoscope were detached. The endoscope was attached to a digital luxmeter (LX-107; LT Lutron, Taiwan) (figure 5.2). In addition, the surgeon who performed the procedure was interviewed about his/her impression of the image displayed during the procedure. This interview was done immediately after finishing the procedure since the image was still clear in the memory of the participating surgeon. A questionnaire was used to asses the subjective impression of the displayed image. The resolution of the imaging chain (RTOT) was also measured before the light guide cable and the endoscope were detached. RTOT was measured using a Borescope Test Chart (Olympus Industrial). The endoscope was attached to a custom-made

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cylinder (see figure 5.2) which positioned and fixed the endoscope at a standardized distance of 5 cm from the Test Chart (Rosow et al., 1998). The Test Chart was illuminated by ITOT. The image of the Test Chart was projected on the monitor. The researchers determined the maximum distinguishable number of lines on the monitor. This number indicates the RTOT and is expressed by lines per mm (l/mm). Sterilization department The quality of light transmission of the light guide cable and the endoscope was measured in the sterilization department. Other light guide cables and endoscopes, which were not used during a procedure, could also be tested in the sterilization department, except those, which were in the sterilization process or kept back for acute procedures at the time of measurements. To standardize the measurements of the light guide cables and endoscopes a set of reference equipment (figure 5.2) has been used which consists of; Light source; OES metal halide light source, CLD-S, Olympus Co., LTD. The illumination level of this light source was adjustable. For standardized measurements the illumination level was set on 50% (mean 84*103 lux, SD: ± 99*102 lux) . Light guide cable; Olympus, Ø 5 mm, and 300 cm. Monocular rigid endoscope; Olympus Ø 10 mm and viewing angle of 0º. A digital luxmeter (LX-107; LT Lutron, Taiwan). Custom-made cylinder for positioning and fixating the light guide cable and the endoscope. All these equipment were new. Adjustable illumination level

Reference light source

Custom-made cylinder

Reference endoscope

Photosensor

Digital luxmeter

Reference light guide cable

Figure 5.2 Reference measurement equipment.

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Light guide cables For a standardized measurement, one end of the light guide cable was attached to the reference light source and the other end to a custom-made cylinder which positioned and fixed the light guide cable at a standardized distance of 5 cm from the photosensor (Rosow et al., 1998). The transmitted light from the reference light source through the light guide cable is measured in lux and is a measure for the illuminance of the light guide cable of the hospital (ILGCHOS). After each measurement of ILGCHOS also the illuminance of the reference light guide cable was measured (ILGCREF). Since the same reference light source was used and for both measurements, the light transmission coefficient (TLGCHOS) of ILGCHOS can be calculated using the next formula:

0

ILGCHOS .T TLGCHOS = I LGCREF LGCREF

1

(1)

It was assumed that TLGCREF was constant. Endoscope Although endoscopes of different diameters and different angles are used in minimally invasive surgery, 00 endoscopes with a diameter of 10 mm are most frequently used in laparoscopy. Therefore, only the endoscopes with this dimension were selected. For a standardized measurement, one end of the endoscope was attached to the reference light guide cable (the light guide cable was connected to the reference light source) and the other hand to a custom-made cylinder which positioned and fixed the endoscope at a standardized distance of 5 cm to the photosensor (Rosow et al., 1998). The transmitted light from the reference light source through the reference light guide cable is measured at the end of the endoscope indicating the illuminance of the endoscope of the hospital (IEHOS). After each measurement of IEHOS also the illuminance of the reference endoscope was measured (IEREF). Since the same reference light source and light guide cable was used for both measurements, the light transmission coefficient (TEHOS) of IEHOS can be calculated using the next formula: IEHOS = ILGCREF . TLGCREF . TEHOS IEREF = ILGCREF . TLGCREF . TEREF 0

TEHOS =

IEHOS . IEREF TEREF

1

It was assumed that TEREF was constant.

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The same set-up as described above was used to determine the resolution of the endoscope. The luxmeter was replaced by the Borescope Test Chart (Olympus Industrial). The Test Chart was placed at the front of the endoscope at a standardized distance of 5 cm (Rosow et al., 1998). The resolution of the endoscope was measured by looking through the endoscope by the researchers. The maximum distinguishable number on the Test Chart indicates the resolution of the endoscope (RE) and is expressed by lines per mm (l/mm). The different measurements are shown in figure 5.3 and table 5.1.

2

3 1

4

Figure 5.3 The points of objective and subjective measurements of the imaging chain.

Table 5.1 Overview of the different measurements Light source

Light guide cable

Endoscope

Hospital

Hospital

Hospital

Measuring at point

Variable

Remarks

1

ITOT

OM

TIQ, S, C, B, CL

SM

RTOT

OM/Borescope Test Chart

3

ILGCHOS

OM

1

IEHOS

OM

4

RE

OM/Borescope Test Chart

3

ILGCREF

OM

2

IEREF

OM

Hospital

Hospital

Hospital

2

Hospital

Hospital

Hospital

2+4

Reference

Hospital

Reference

Reference

Reference

Reference

Reference

Reference

Reference

Reference

Hospital Hospital

Reference

OM = Objective measurements SM = Subjective measurements

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5.2.3.4 Model The aim of this study was to assess the quality of light guide cables and endoscopes by objective measurements and establish the correlation between the illuminance of the abdominal cavity and surgeons’ experience of the image. Anderson’s functional measurement theory is used as inspiration to understand and evaluate the correlation between objective and subjective measurements (de Ridder & Majoor, 1990). This theory provides a framework for efficiently describing the unobservable, psychological processes underlying the comparison of stimuli. An essential assumption in functional measurement theory is that sensations evoked by different, independent stimuli are combined to form an internal or psychological response. Figure 5.4 illustrates the application of the functional measurement theory within the scope of this study.

OBJECTIVE RTOT RE ITOT TEHOS

SUBJECTIVE S C Q B C

TLGCH

Figure 5.4 Application of the functional measurement theory within the scope of this study.

The objective measurements RTOT, RE, ITOT, TEHOS, and TLGCHOS form the independent psychophysical functions of the framework. These independent psychophysical functions transform stimuli into sensations S, C, B, and CL. These intermediate sensations are combined to form a psychological response. Subsequently, this psychological response is transformed into overt response Q by the judgment function.

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In this model, the parameter light source is missing which is an essential part of the imaging chain. This parameter is not measured directly but can be calculated by the formula:

ILS =

ITOT TE . TLGC

(5)

SPSS 14.0 for Windows was used for statistical analysis of the results. The level of significance that is used during all the analysis was, = .05. The next assumptions were formulated and tested: Assumption 1: ITOT will differ depending on the kind of hospitals and surgical procedures. Assumption 2: There is a correlation between the independent variables, intermediate variables, and dependent variable (the ILS will be included in the correlation analysis). Assumption 3: The output of the light source ILS will be reduced in the course of time (the reference light source will be used for analysis). Assumption 4: RE will be higher than RTOT. Assumption 5: The measured light guide cables and endoscopes will be systematically lower than the reference equipment.

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5.3

RESULTS

Overview attended procedures in different type of hospitals Table 5.2 Specifications of the attended surgical procedures KIND HOSPITAL

TOTAL N = 65

ITOT

Mean = 47*103 lux SEM: 60*102 Q = 6,8 S = 6,9 C = 6,9 B = 6,5 CL = 6,9

ITOT

N = 45 Mean = 56*103 lux SEM: 76*102 Q = 6,7 S=7 C = 6,9 B = 6,6 CL = 6,9

ITOT

N = 11 Mean = 25*103 lux SEM: 57*102 Q=7 S=7 C=7 B = 6,4 CL = 7,1 N=9 Mean = lux

ITOT

17*103

SEM: 38*102 Q=7 S = 6,6 C = 6,6 B = 6,6 CL = 6,3

ACADEMIC HOSPITAL

TEACHING HOSPITAL

COMMUNITY HOSPITAL

N=5

N = 17

N = 13

N=8 Mean = 81*103 lux SEM: 23*103 Q = 6,3

N = 37 Mean = 50*103 ux SEM: 87*102 Q = 6,9

N = 20 Mean = 28*103 lux SEM: 62*102 Q = 6,9

S = 6,5 C = 6,7 B = 6,6 CL = 6,5

S=7 C = 6,8 B = 6,6 CL = 7

S = 6,9 C = 7,1 B = 6,5 CL = 6,9

N=5 Mean = 121*103 lux SEM: 20*103 Q = 6,7 S = 6,7 C = 6,8 B = 6,8 CL = 6,8

N = 23 Mean = 67*103 lux SEM: 11*103 Q = 6,7 S = 7,2 C = 6,9 B = 6,7 CL = 7

N = 17 Mean = 30*103 lux SEM: 72*102 Q = 6,7 S = 6,8 C=7 B = 6,4 CL = 6,9

N=0

N=8 Mean = 27*103 lux SEM: 77*102 Q = 6,8 S = 6,8 C = 6,7 B = 6,2 CL = 7,2

N=3 Mean = 16*103 lux SEM: 18*102 Q = 7,6 S = 7,5 C=8 B=7 CL = 7

N=3

N=6

Mean = 15*103 lux SEM: 60*102

Mean = 19*103 lux SEM: 52*102

Q = 5,8 S=6 C = 6,5 B = 6,2 CL = 5,7

Q = 7,6 S = 6,9 C = 6,7 B = 6,7 CL = 6,5

N=0

ITOT = Total illuminance imaging chain visited hospital Others = Laparoscopic Splenectomy (2) laparoscopic Nissen fundoplication (1), laparoscopic donor nephrectomy (1), laparoscopic sigmoid resection (1), diagnostic laparoscopy (1), adjustable gastric band (1), laparoscopic sterilization (1), and laparoscopic rectopexy (1).

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5.3.1 Assumption 1 The averaged ITOT is divided into 3 different kind of surgical procedures (laparoscopic cholecystectomy (Lap.Chol), laparoscopic hernia repair (Lap.Hernia), and others) and hospitals and are shown figure 5.5.

160000 140000 120000 100000 80000 60000 40000 Lap.Chol

20000

Lap. Hernia Others

0 Academic

Teaching

Community

Kind Hospital Figure 5.5 The averaged ITOT per hospital type, divided into 3 groups (laparoscopic cholecystectomy (Lap.Chol), laparoscopic hernia repair (Lap.Hernia), and others).

In all of the groups, there is a descending trend of ITOT from academic to community. The ITOT is systematically the highest for academic hospitals. The ITOT during Lap. Cholecystectomy differs significantly between the 3 kind of hospitals: F (2, 340) = 5.67, (p < .01). The ITOT during Lap. Cholecystectomy in the category training hospital is significantly higher than the Lap. Hernia repair; t(22) = 5.6, p < .01. The ITOT during Lap. Cholecystectomy in the category community hospital is significantly higher than the Lap. Hernia repair; t(16) = 4.23, p < .01.

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5.3.2 Assumption 2 The correlation between the independent variables (ILS included), intermediate variables and dependent variable and the corresponding correlation coefficients are shown in figure 5.6. The C (contrast) and B (brightness) is put together since the correlation was high and the double arrows indicating a correlation in both directions.

r = .34

r = .34

RE

RTOT

TLGCHOS r = .46 r = .81 r = -.33

ITOT

TEHOS

r = -.36

C/B

r = .91

Q

r = .47 r = .74

r = .44

ILS

r = .59 r = .36

S

r = .72

CL

r = .78

Figure 5.6 The correlation between the independent variables (ILS included), intermediate variables and dependent variable and the corresponding correlation coefficients.

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5.3.3 Assumption 3 The reference light source was used to analyze the effect of ageing on the level of illuminance (figure 5.7).

120000

110000

100000

90000

80000

70000

60000 10-12-02

28-02-03

19-05-03

7-08-03

26-10-03

14-01-04

3-04-04

Date of visit Figure 5.7 The reduction of the output of the reference light source in the course of time.

5.3.4 Assumption 4 The resolution of the monitor was 5.34 ± 0.89 lines per mm (l/mm) and that of the endoscope was 7.13 ± 0.65 lines per mm (l/mm). 5.3.5 Assumption 5 In total 252 light guide cables of different length and diameter have been tested. The majority, 70% (175) of the total (252) measured light guide cables had a diameter of Ø 4.8 or Ø 5 mm. These cables are selected as the most frequently used ones in different hospitals. Since the reference light guide cable has the diameter of Ø 5 mm, a selection of the measured light guide cables is made with a diameter of Ø 4.8 and Ø 5 mm to compare with the reference light guide cable. The illuminance of the reference light guide cable on average was 83*103 ± 12*103 lux. The results of the illuminance of the selected light guide cables show that 93% of the measured light guide cables had an illuminance less than the reference light guide cable.

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In total, 166 endoscopes have been tested. The illuminance of the reference endoscope on average was 56*103 lux. The results of the illuminance of the measured endoscopes show that 91% of the measured endoscopes had an illuminance less than the reference endoscope.

5.4

DISCUSSION

The advanced technology that surgeons use nowadays during MIS has become complex and has altered the interaction between the surgeon and the equipment. Frequently, this interaction is unnatural and cause problems contributing to the medical errors rates (Verdaasdonk et al., 2007). Some of these errors during surgery are influenced by or related to several factors intrinsic to laparoscopic viewing. Laparoscopic viewing is only possible by the “imaging chain” and the image displayed on the monitor will be as good as the imaging chain’s weakest component (Swaitzberg, 2001). This image is the critical source of information to the surgeon. From this perspective, a subjective and objective evaluation of the image quality in practice is essential. The results of the objective measurements of this study show that total illuminance of the imaging chain (ITOT) differ systematically between the different types of hospitals. This indicates a diversity of the “imaging chain” systems used in the hospitals. In general, each hospital prefers a certain brand to purchase, but in practice it is likely to use different brands of light source, light guide cable and endoscope as one system. While using different brands of equipment as one system it should be considered that these components have to fit properly to each other to prevent light loss due to differences in diameters (Frank et al., 1997). Further evaluation of ITOT shows that ITOT during Lap. Cholecystectomy differs significantly between the three kinds of hospitals. The descending trend of ITOT from academic to community shows that surgeons working at academic hospitals may prefer higher light intensities during surgical procedures. A remarkable finding was that the total illuminance during Lap. Cholecystectomy was significantly higher than during Lap. Hernia repair. According to Danis there are differences in the way that organs and tissues scatter light and makes herein a division of high luminous tissues such as fat, the stomach and the bowel; mediumluminous organs such as diaphragm and gallbladder; and dark, mostly parenchymatous organs such as the liver and the spleen (Danis, 1998). During Lap. Cholecystectomy mainly the gallbladder (medium-luminous organ) and the liver (dark organ) are in sight and during Lap. Hernia mainly the fat and the bowel are in view. The intensity of light reflected by the gallbladder and liver is lower than fat and bowel. This means that under same ITOT conditions the image during Lap.

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Cholecystectomy will be less bright than during Lap. Hernia repair. It seems that surgeons adjusting the light intensity intuitively depending on the kind of organs and tissues which are visible during the surgical procedure. In most of the hospitals, it was observed that the light guide cables and endoscopes were packed separately. Before a surgical procedure starts the necessary instruments and equipment was selected and putted ready for use. It seems that the selection of the light guide cables and endoscopes occurs independently since no correlation was found between these two components. However, a significant correlation between the ITOT and the light transmission coefficients of the endoscope (TEHOS) and light guide cable (TLGCHOS) was found indicating that ITOT is a product of the transmission of the light guide cable and endoscope, and output of the light source (Albayrak et al., 2006a). The total illuminance depends on the light transmission quality of the light guide cable and endoscope. Although, there was no correlation between the light guide cable and the endoscope the TEHOS was systematically lower than the TLGCHOS. Both light guide cables and endoscopes contain glass fibres to transmit light but the amount of glass fibres in the light guide cables are more than that of the endoscope. In addition, the transmission coefficient of the endoscope is determined at the end of the imaging chain, which means that a reduction of loss in light was occurred in the delivery system. A well-known phenomenon during minimally invasive procedures is that the surgeon is confronted with a suboptimal-lighted image. In a situation like this the surgical team have the tendency to turn the knob of the light source to a higher light intensity, mostly up to 100%. This observed phenomenon is in line with the findings of this study. The negative correlation between the illuminance of the light source and transmission coefficient of the light guide cable indicates when a light guide cable have a poor light transmission quality the light intensity of the light source is increased to compensate the light loss. Frequently, this situation results in an overexposed image. However, the results of a previous study show that the 40% of hyper illuminated area can be thus appreciated as the critical limit of hyper illumination (Danis, 1998). Hyper illumination has to be avoided to prevent damage on the fibres of the light guide cable and endoscope due to heat development. In this study, the image quality was assessed by asking the participating surgeon to judge the displayed image in terms of: overall image quality (Q), sharpness (S), contrast (C), brightness (B), and quality of colour (CL). According to Hanna et.al., the image quality is determined by three major parameters; image resolution, luminance and chroma (Hanna & Cuschieri, 2001). The resolution determines the visibility of details in the image and refers to the sharpness and contrast of the image and the luminance refers to the brightness (Hanna & Cuschieri, 2001). The results show that each parameter was correlated to each other and with the overall image quality judgment (Q). The high correlation between the contrast and

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brightness judgment could indicate that surgeons do not make a distinction between contrast and brightness of an image. Hanna et.al also shows that chroma denoting the colour intensity or saturation is a major parameter of the image quality (Hanna & Cuschieri, 2001). However, the findings of this study could not confirm this strongly since the colour judgment was lowest correlated with Q. The quality judgment of the surgeons was influenced by the total illuminance measured during surgical procedure. This is not surprising since ITOT is the amount of light entering the abdominal cavity and the judgment of the surgeon is actually based on the image wherein this amount of light is reflected/absorbed by the surrounding organs and tissues. The negative correlation between ITOT, Q, C and B indicates that surgeons do not appreciate high levels of illuminance as a consequence of hyper illumination of the image. The output of the reference light source is reduced in the course of time. This could be caused by ageing of the light source, surface losses and/or bulb absorption. The surgical team should be aware of this phenomenon. Regularly inspection and maintenance of the light source and replacement of the bulb on time could prevent unnecessary light loss during surgery. The resolution of the monitor was systematically lower than the resolution of the endoscope. This is in line with the findings of Berber, which states that the monitor is the rate-limiting step in improving the image resolution (Berber & Siperstein, 2001). However, it seems that the resolution of the endoscope (RE) can be improved by a higher ITOT and a light guide cable with a high light transmission coefficient since a positive correlation was found between RE, ITOT and TLGCHOS. By improving the resolution of the endoscope, also the resolution of the monitor will be slightly improved since these two are correlated to each other. Furthermore, the illuminance of the measured light guide cables and endoscopes were systematically lower than the reference equipment. During the time of visits, it was observed that the hospitals did not have the equipment to test these components. All components of the imaging chain gradually deteriorate during the lifetime. Therefore, regularly inspection and maintenance of these components is essential for quality assurance of the system. Hence implementation of guidelines for inspection, maintenance and replacement of laparoscopic instruments and related equipment is necessary in each hospital to improve patient safety (IGZ, 2007). Although a high illuminance of the abdominal cavity is not appreciated by surgeons, during Lap. Cholecystectomy the illuminance was significant higher than during Lap. Hernia repair. It seems that surgeons are seeking for an image, which is the

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optimum in their opinion. According to Way identification of structures, take place by matching the patterns, which is sawn to the mental model of that structures stored in long-term memory (Way et al., 2003). Since surgeons generally perform each surgery under same conditions and with same equipment, they probably have a clear view of the expected/familiar image based on their previous experiences. It seems therefore that they are comparing the actual image with the expected/familiar image and use this experience to form their judgment. In this study a questionnaire was used immediately after finishing the surgical procedure to assess surgeons’ subjective impression of the displayed image during the procedure. This way of evaluation have its limitations since surgeons will namely remember the last part of the image and use this as a reference for their judgment. Further research should be done on surgeons’ subjective experience of the displayed image. Other methodology and evaluation techniques should be used which gain more insight into the cognitive processing of judgment. Acknowledgement The authors would like to acknowledge the contribution of the participated hospitals to this study.

93

This chapter is based on the following studies: Albayrak A, and Snijders CJ. (2007). Ergonomy in the OR. In JB Trimbos & GCM Trimbos Kemper (Eds.), Basics of surgery: Tools, techniques and expertise (pp. 151-169). Maarssen: Elsevier gezondheidszorg. Bonjer HJ, Albayrak A, Stassen LPS, Casseres YA, Meijer DA. Improving the endoscopic image: tips and tricks. Submitted (2008).

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CHAPTER 6 PRACTICAL ERGONOMIC SOLUTIONS FOR THE SURGICAL TEAM

In chapter 2, the ergonomic problems of the surgical team were discussed. In this chapter an overview of practical solutions regarding the encountered problems in Chapter 2, are given. The emphasis is on the application of the solutions in daily practice. These solutions will be discussed along the three domains of ergonomics; physical, sensorial and cognitive. The physical ergonomics will be restricted to the strain of musculoskeletal system which is relevant for neck, shoulder, arm, hand problems, lower back, pelvis and foot. As most of the sensorial and cognitive problems are seen during laparoscopy this two sections will be focusing on laparoscopic procedures.

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6.1

PHYSICAL ERGONOMICS

6.1.1 Neck 6.1.1.1 Open surgery Problem: Uncomfortable body posture Solution An ergonomic work environment requires unobstructed line of vision in neutral standing posture with a natural viewing angle between 10º and 25º below the horizontal in the sagittal plane and 30º to left and right (figure 6.1) (Gerbrands et al., 2004).

Figure 6.1 Ergonomic viewing guidelines.

Another solution to prevent physical discomfort in the neck due to obstructed line of vision is the use of an adjustable body support. In addition, problems arising from a non-optimal working height will also solved since the body support is adjustable in height and suitable for users with different body height (figure 6.2).

Figure 6.2 Adjustable body support with semi-standing support.

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6.1.1.2 Laparoscopy Problem: Limited number and incorrect positioning of monitors results in physical discomfort in the neck (flexion, extension, and rotation). Solution The members of the surgical team stand on both sides of the operating table in the majority of the procedures. Assessing the position of the surgical team from an ergonomic point of view, each member of the surgical team should have an unobstructed line of vision without neck torsion. Figure 6.3 shows the ergonomically optimal positioning of the surgical team and the corresponding number of monitors with respect to positioning of the surgical team (Albayrak et al., 2004).

Figure 6.3 Ergonomically optimal positioning of the surgical team and number of monitors.

6.1.2 Shoulder/Arm 6.1.2.1 Open surgery Problem: Due to the position and depth of the incision during open surgery, surgeons have fixed work posture, tending to work with arms abducted and unsupported. A high static load is imposed on the shoulder-neck region and shoulder joint by this posture.

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Solution Optimal positioning of the operating table in height (approximately at the height of umbilicus of the surgeon) as well as in axis (e.g. head-down or head-up, tilt) with respect to the altering body posture of the surgeon during the procedure. 6.1.2.2 Laparoscopy Problem: Manipulating problems of laparoscopic instruments and wearing heavy lead aprons. Solution Lowering the height of the operating table to counterbalance the increased length of the instruments is a practical solution. The operating table should be adjusted in height regarding the tallest person present in the surgical team (shorter persons can use a footstool) to reduce strain on the shoulders. Creating an optimal working height for the surgical team will also decrease manipulation problem of the instruments. The discomfort and difficulty ratings were lowest when instruments handles were positioned at elbow height (Berguer et al., 2002). Regarding the guideline of positioning the instruments at elbow height the ergonomically operating surface height (defined as the navel height of the patient, lying on the operating table while the abdomen is filled with CO2 gas) lies between 0.7 and 0.8 of the elbow height of the surgeon/resident (van Veelen et al., 2002b) (figure 6.4).

Elbow height

Operating surface height

Figure 6.4 The optimal posture of the surgeon/resident during laparoscopy.

In practice, this means for laparoscopy adjusting the operating table on pubic height of the tallest person in the surgical team. Most of the lead aprons, which are currently in use, consist of one part. Replacing these by a lead vest and lead skirt will reduce the weight on the shoulder.

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6.1.3 Hand 6.1.3.1 Open surgery Problem: Grasping and manipulating problems (unintended use) of instruments by using these differently than the way they are originally designed for. Solution Avoid unintended use of instruments. 6.1.3.2 Laparoscopy Problem: Grasping and manipulating problems due to the complexity and inefficient mechanical properties of instruments. Solution Based on an ergonomic approach the new action criteria for laparoscopic instruments are summarized in Table 6.1 (van Veelen, 2003). Table 6.1 New action criteria of laparoscopic dissection forceps.

New action criteria for design of laparoscopic dissection forceps Posture of hand and arm

The angle between handle and shaft must be between 14º and 50º When the handle is manipulated with a precision grip, wrist excursion must be neutral for 70% of the manipulation time When the handle is manipulated with a force grip, wrist excursion must be neutral for 70% of the manipulation time

Forces in hand and arm

The grip opening must be between 60 and 80 mm

Compressive force on the hand

The handle must have a minimum width of 10 mm to prevent extreme contact area pressure

Finger movement

The instrument must be provided with a rotation knob to allow rotation of the instrument tip. This control switch must be manipulated with thumb or 2nd finger and when the instrument is manipulated in free spaces, no friction must be experienced

Any disturbances (e.g. friction and spring forces) must be avoided to enable an optimal force feedback of tissue on the surgeon’s hands: if the handle is manipulated in free spaces, no friction must be experienced

Left-handers

The handle must allow left- and right-handed manipulation

Anthropometrics

The dimension of finger ring must be: inner length min. 30 mm, inner width min. 24 mm

Function handle

The handle of a dissection forceps has to support a precision as well as an force grip for manipulation

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6.1.4 Lower back 6.1.4.1 Open surgery Problem: Static strain and fatigue in the back muscles due to uncomfortable body posture. Solution There are two solutions available. The first one is rest by stretching the upper body upright. During shorter bouts of work, only ATP, CP, and some of the oxygen stored in muscle (myoglobulin) is utilized. During the rest breaks, these sources were replenished with minimal penalty. For longer bouts of work, the muscle utilized the glycolytic process to produce energy quickly at the penalty of elevating blood lactate and incurring fatigue. Thus, the optimum arrangement of work is to have short, frequent work-rest cycles (Freivalds, 2004). The second solution is supporting the body by means of an ergonomic body support (Albayrak et al., 2006b, 2007) (figure 6.5).

Chest support

Semi-standing support

In height adjustable platform

Figure 6.5 Ergonomic body support.

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The platform is adjustable in height by means of a motor, which can be operated by a remote control. The height of the platform ranges from 60 mm (minimum) to 460 mm (maximum), 95% of the user group will have a comfortable posture (in combination with the current operating tables). The semi-standing support at the buttocks has a maximum height of 900 mm (when the platform is positioned in the lowest position for a tall surgeon). The height of the semi-standing support is proportional to the height of the platform. This allows correct placement of this support for the whole user group. During open surgery, the surgeon uses the chest support by leaning against it and during minimally invasive surgery the semistanding support can be used (Albayrak et al., 2007). 6.1.4.2 Laparoscopy Problem: Limited body movement and static upright posture. Solution The two solutions that are discussed in the open surgery section are also valid for laparoscopic surgery. Rest by stretching the upper body upright during the procedure and the use of an ergonomic body support. 6.1.5 Pelvis 6.1.5.1 Open surgery, laparoscopy Problem: Leaning against the solid and metal edge of the rail of the operating table results in bruising in soft tissue around the pelvis region. Solution The developed hip support from foam, which can easily attach to the rails, will prevent the bruising (figure 6.6).

Figure 6.6 Hip support.

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6.1.6 Foot 6.1.6.1 Open surgery During open surgery, the diathermy is activated by pressing a button on the instrument. Due to manual control of this equipment a pedal is unnecessary. 6.1.6.2 Laparoscopy Problem: Positioning problems due to losing contact with the pedal and the risk of accidentally activating the wrong function (left or right) of the pedal because of lack of vision. Solution A new pedal is designed in the form of a flat round disc (figure 6.10) (van Veelen, 2003).

Figure 6.7 Pedal.

Pedal control is based on endo- and exo-rotation of the foot. The switch is activated by positioning the foot on the disc and by rotation of the foot (leg): right rotation activates the coagulation function, and left rotation activates the cutting function. Since the disc is flat and thin, the user can stand on the disc during surgery with the weight spread evenly over both feet. The advantage is that no enduring dorsal flexion of the ankle is needed to control the switch. In addition, the pedal does not obstruct the freedom of movements because the user will not erroneously push the wrong switch (Van Veelen et al., 2003c).

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6.2

SENSORIAL ERGONOMICS

Problem: Alignment problems of the monitor with the hands and instruments. Solution Adopting the optimal/ergonomically viewing guidelines in the operating room will reduce overburdening the surgeon (figure 6.8) (Matern et al., 2005; Van Veelen et al., 2002a; van Veelen et al., 2002b).

Figure 6.8 Ergonomic viewing guidelines. Combination of semi-standing support of the buttocks and platform adjustable in height.

Additional to this solution it is also being advised to adopt the solution described in section 6.1.1.2. Problem: Degradation of monocular depth cues due to “anti-cues” arising from the monitor. These are caused by the monitor frame and the glare and reflection from the glass of the monitor. Solution Performing the surgery with dimmed environmental light and correct alignment of the visual axis with the monitor will reduce the glare and reflection from the glass of the monitor.

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6.3

COGNITIVE ERGONOMICS

Problem: There are several factors intrinsic to laparoscopic viewing that degrade the surgical quality and enhance the probability of error during surgical procedures. Many of the related problems are due to the perceptual and spatial factors. Representation of the three-dimensional surgical field on a two-dimensional screen reduce depth perception. Scaling difficulties caused by magnification and impaired visual image of the anatomy in comparison to the experience of an open procedure. The various spatial difficulties encountered during laparoscopy result in problems with cognitive mapping and hand-eye coordination. The surgeon has no direct control over the position or orientation of the endoscope. Instead, the surgeon must rely on the assistant to maintain an optimal position; however, frequently unintentional camera rotation occurs that can lead to disorientation and misinterpretation of position of the organs. One of the problems limiting the surgeon’s acquisition of skill and degrading the surgical quality is due to the fulcrum effect. Solution Surgeons are trained to deal with the problems as described above. In general, the model of Rasmussen can be used to describe human behaviour. In this model three different levels can be distinguished: skills-, rule-, and knowledge based behaviour. Skill based behaviour is the human behaviour whereby the task execution is highly automated. This behaviour can be trained by means of a training in for instance a surgical simulator, pelvitrainer and animal models (Wentink et al., 2003). Factors that improve skill-based behaviour are active or passive feedback of the instrument’s forces and increasing the number of degrees of freedom comparable to the functions available during open surgery (Stassen et al., 2001). During rule-based behaviour task execution is controlled by stored rules or procedures, which have been derived from previous cases, other people’s expertise and instructions. The procedural steps and recognition of anatomy are examples of rule-based behavior during surgery. This behaviour can be trained and improve by means of lectures, textbooks, video instructions, integration of per- and preoperative information and better logistics (Stassen et al., 2001). During MIS the rule-based behaviour can be improved by means of improving the dept perception (e.g. improving pictorial information, parallax and visual motor cues) and enabling the surgeon to control the endoscope himself (Stassen et al., 2001). During knowledge-based behaviour the task execution cannot be automated. The aim is explicitly formulated, based on the analysis of the overall aim (Wentink et

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al., 2003) and best strategy is selected, by means of mental processing and the appropriate actions are taken. Knowledge based behaviour can be trained during actual procedures in the OR or via living animal models outside the OR (Wentink et al., 2003). Training of technical skills Technical skills, which involve knowledge of anatomy and pathology, dexterity, hand-eye coordination, technical proficiency, etc is essential to surgical training (Cuschieri, 2006b; Moorthy et al., 2003b; Scott et al., 2000). In order to perform MIS the surgeon needs highly developed motor skills (Marohn & Hanly, 2004; Matern et al., 1999). Next to the apprenticeship model these skills can be trained in simulated environment which gives the trainee objective and direct feedback of their performance. 6.3.1 IMAGING CHAIN 6.3.1.1 Light source An excellent light source is therefore mandatory for safe endoscopic surgery. The light bulb is the most important part of the light source. An old bulb can cause several alterations to the image quality, as darkening and blurry image. Therefore, it is mandatory to replace the bulb after the recommended period of time (Berguer, 1996). Over a period of time, wear on the arc lamp is indicated by a decrease in the colour temperature emitted. This gradual modification in the colour temperature accounts for the need to adjust the white balance. 6.3.1.2 Light guide cable It is also important to pay attention to the light guide cable, which is responsible for transmitting light from the light source to the endoscope. Light guide cables contain multiple glass fibres, which can melt due to heat generated during light transmission. Another cause of loss of glass fibres is breakage due to kinking of the light guide cable. Light guide cables should be controlled regularly. Objective assessment of the quality of a light guide cable can be done using a lux meter that measures transmitted light. If such a device is not available, the light cable should be attached to the light source, which is turned on at its lowest setting. When the end of the light cable is inspected at an angle almost parallel to its surface, defective glass fibbers can be noted as black dots allowing estimation of the remaining functioning fibbers (figure 6.9). Careful handling and avoiding impact will preserve the longevity of these cables.

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Normal cable

Cable with few broken fibres

Cable with many broken fibres

Figure 6.9 Schematic view of broken fibres of the light guide cable.

6.3.1.3 Endoscope The next step is checking the endoscope. The eyepiece of the endoscope should be inspected for obscuring spots. Glancing through the endoscope will reveal distortion of the image or blurred spots, which require repair of the endoscope. The resolution and distortion characteristics of the endoscope can be measured by using a test chart. A simple rough method for determining broken or melted fibres of the endoscope is to hold the distal tip of the endoscope in the direction of a ceiling or operating lamp. As in the light guide cable, broken or melted fibres will be visible as black dots at the connector for the light guide cable at the proximal part of the endoscope (figure 6.10). The larger the diameter of the cable, the more it heats the endoscope and thereby the more fibres will melt.

Normal endoscope

Endoscope with few broken fibres

Endoscope with many broken fibres

Figure 6.10 Schematic view of broken fibres of the endoscope.

6.3.1.4 Camera When proper functioning of the light source, light guide cable, and endoscope has been confirmed, the camera system needs to be tested. The heart and soul of the endoscopic image is the camera system, consisting of chip camera and camera unit. The chip camera is exposed to repetitive mechanical injury by storing it in the endoscopic working unit or by dropping it. Proper functioning of the chip camera

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can be assessed by employing a test chart (Berber et al., 2002). When such a test chart is not available, the quality of the chip camera and the camera unit can be determined by focusing the camera while not attached to the endoscope on an object with coloured details in the operating room. When these details are not projected with sufficient acuity on the endoscopic screen, another chip camera should be attached to the camera unit to rule out malfunction of the chip camera. If the poor image persists upon attachment of another chip camera, the camera unit requires resetting or overhaul. The setting of the camera unit requires regularly review by technicians. 6.3.1.5 Monitor The monitor displays the final image. In general, the monitor is not subjected to as much wear and tear as the other components of the imaging chain. The most common problem is the manipulation of the monitor controls. Poor adjustments of these controls can degrade an excellent quality input (Schwaitzberg, 2001). The monitor can be easily calibrated by using the reset button on the remote control. Newer monitors have auto calibration programs whereby the colour bars are displayed from the camera and the calibration program properly adjusts the brightness/contrast. 6.3.1.6 Poor image during endoscopic surgery Fogging of the endoscope is one of the most common and annoying imaging problems, which occurs during endoscopic surgery. It jeopardizes the safety of the endoscopic procedure as the view of the operative field becomes unclear. Extraperitoneal surgery appears to be complicated more frequently by fogging than intraperitoneal surgery. Fogging is caused by deposition of vapour on the tip of the endoscope and most often occurs when the lens tip is introduced into the abdominal cavity where the temperature and humidity are higher than the extracorporeal environment. To prevent fogging, heating the endoscope in a warm water bath has been advocated but does not appear effective. Some have suggested that insufflating cold and dry carbon dioxide should occur through a port, which is not used for insertion of the endoscope. However, this measure does not prevent fogging as well. A double walled tube that is slipped over the endoscope has been developed to spray the tip of the endoscope. Use of this device requires a 12 mm trocar to allow insertion of a 10 mm endoscope with this spraying device. Spraying saline or water through this double walled tube cleans the tip of the endoscope but usually leaves a droplet on the lens, which distorts the image. Another approach to the problem of fogging is the use of a specially designed fogless laparoscope (Hashimoto & Shouji, 1997).

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Various agents are available to clean the tip of the endoscope. Most of these agents contain a detergent, which decreases the surface tension of fluid on the lens of the endoscope. The surface of the liver can be used as well to clean the tip of the endoscope unlike other intraperitoneal structures. The nature of the cleaning capacity of the liver surface is unknown. A deteriorating image during endoscopic surgery can be due to increased absorption of light by accumulated blood. Evacuating the blood can improve the clarity of the image. Another possibility to improve the light intensity is to zoom out as much as possible. 6.3.1.7 Sterilization Cleaning and sterilization of the endoscope deserves special attention. In a crossover, clinical study performed by the Departments of Surgery of the Erasmus University Medical Centre Rotterdam and the Reinier de Graaf Gasthuis in Delft the impact of cleaning of endoscopes was investigated. At the hospital in Rotterdam fogging was rarely encountered while fogging was common at the hospital in Delft. Endoscopes were exchanged between hospitals and subjected to local cleaning and sterilization standards. After 3 to 5 cleaning and sterilization cycles in Rotterdam, fogging of endoscopes from Delft disappeared while the opposite occurred in Delft with the endoscopes from Rotterdam. Studying the cleaning procedures in both hospitals revealed that endoscopes were cleaned with methylalcohol and acetone in Delft. The endoscopes in Rotterdam were cleaned with ethylalcohol and after sterilization, a layer of silicone was sprayed on the endoscopes. Therefore, the cleaning process of endoscopes appears of importance. Silicone application can prevent fogging. This is in line with the observation that the tip of the endoscope can also rather effectively be cleaned by rubbing the tip against the surgeon’s glove with contains silicone.

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6.3.1.8 Tips and tricks Inadequate lighted image Components Light source Light guide cable Endoscope Operative field

Solution Set the light source on “automatic” or “manual” max. Replace bulb if recommended period of time is reached Check the light guide cable for damaged fibres Adjust connection to the light source Check the endoscope for damaged fibres Excessive blood leads to absorption of light. Proper irrigation and suction should give a better view

Blurry image Components Endoscope Camera Monitor

Solution Clean the tip of the endoscope (with warm water) Try the use of anti-fogging agents White balance the camera Fine tune the camera Correct adjustment of the monitor controls

Distortion of the image Components Endoscope/camera

Solution Use a test chart to define the distortion and resolution characteristics to assess the quality of this components

Heat generation Check the diameters of the connectors between light source, light guide cable and endoscope

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This chapter is based on the following book chapter: Albayrak A, Wauben LSGL, and Goossens RHM. Ergonomics in the Operating Room – Design framework. (2008). Accepted as book chapter in Ergonomics: Design, Integration and Implementation by Nova Science Publishers, Inc.

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FRAMEWORK FOR DESIGNERS: CASE STUDIES

In this chapter three cases will be discussed which describes medical product solutions in the three domains of ergonomics; sensorial, cognitive and physical ergonomics. In Case 1, the design of an abdominal wall tension measurement device will be discussed followed by the second case which shows how the ergonomics of minimally invasive surgery can be improved by means of an integrated surgical suite. Finally, within the physical domain, the design of a curved instrument for minimally invasive surgery to improve surgeon’s body postures will be illustrated. All the cases will be discussed along the different phases of the basic design cycle according to Roozenburg & Eekels (Roozenburg & Eekels, 1995).

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7.1

INTRODUCTION

7.1.1 Design framework According to Roozenburg and Eekels product development is a goal-directed thinking process in which problems are analyzed, objectives are defined and adjusted, proposals for solutions are developed and the quality of those solutions is assessed (Roozenburg & Eekels, 1995). This thinking process and the procedures that industrial designers follow can be structured by “design methodology”. Design methodology provides designers with knowledge on the design process and also provides a body of methods and rules to be used in designing. Nearly all rules and methods for designing are heuristics; these help in finding a solution for some problems, but do not guarantee that a solution will always be found. Before discussing the structure of a design process, the term “design” has to be defined. The focus is on designing material products and therefore “design” is defined as ‘to conceive the idea for some artifact or system and/or to express the idea in an embodiable form’ (Roozenburg & Eekels, 1995). Roozenburg and Eekels describe designing as a special form of problem solving and reasoning which takes place from goal (the function) to means (the design) (Roozenburg & Eekels, 1995). As in problem-solving in general, in designing many means can realize the goal and it is initially uncertain what means is (the most) effective. It therefore needs no further explanation that design is in essence a trialand-error process that consists of a sequence of empirical cycles, in which the knowledge of the problem as well as the solution increases spirally. The basic design cycle is illustrated in figure 7.1

Figure 7.1 Basic design cycle according to Roozenburg and Eekels (Roozenburg & Eekels, 1995).

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As illustrated in figure 7.1 the design cycle consist of different stages. The stages in the gray boxes have a divergent character, which means that the designer should look very broadly to the content. Conversely, the white boxes have a convergent character and define the focus of the content for the next step. The design process is iterative and it comprises a sequence of reductive steps and deductive step (Roozenburg & Eekels, 1995). The designer compares the so far attained results and the desired results between these two steps. The different stages will be discussed briefly. 7.1.1.1 Analysis phase Generally, an assignment or a direction for a new product idea is provided whereby also the target group is defined. In the analysis phase the designer starts to explore the problems around the new product idea, do research on the target group and try to get insight in their “world”. This explorative research will result in a problem statement. The problem statement should reflect on, who have the problem, what is the problem and what causes this problem. Within this problem statement the designer and his/her team has to define their goals clearly to be able to assess later whether the design proposal is indeed a solution of the defined problem. A list of requirements is mostly drawn up. This is a tool to define the goal more clearly and represents the design specifications, which define the design space for the next step. 7.1.1.2 Synthesis phase In this phase a provisional design proposal is generated. It is a crucial phase since the creativity of the design team plays an important role. In this phase, the designer makes a “synthesis” of the separate ideas, solutions, and present information to make an integral solution. The design proposal generated in this phase is a possibility to solve the problem of which the value will be assessed in the later phases of the design cycle. 7.1.1.3 Simulation phase According to Roozenburg and Eekels simulating is forming an image of the behaviour and properties of the designed product (Roozenburg & Eekels, 1995). In product development often the term “prototype” is used which represents the properties of the new product idea as closely as possible. These properties are related to technical functioning, ergonomics, and the semantic and aesthetic values of the product idea. Simulation of the product gives the design team an impression of the expected functioning in a certain context. This can be done in many different ways but user research gives the design team a well-considered feedback about the expectations of the user of the product, the actually usage, the interaction, anthropometrics and technical functioning.

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7.1.1.4 Evaluation phase In this phase the value of the provisional design proposal is assessed by testing, which means the expected properties are compared with the desired properties as formulated in the design specifications. 7.1.1.5 Decision The expected and desired properties will always differ from each other but it is important to decide if those differences are acceptable or have to be redefined. Since the design cycle is iterative the design team can return to the synthesis phase, for example to generate a better design proposal or to define different design specifications which fit better or formulate recommendations to approve the design proposal. The basic design cycle as illustrated in figure 7.1 is the most fundamental model of designing and it can be perfectly used with different kind of methodologies. 7.1.2 Methodology The medical specialists are professional users with their specific needs, work conditions, language, culture and work environment. When designing products for professional users their involvement in the design process is crucial since designers can use their input to improve the design proposal. A methodology, which can be used from this perspective, is “Participatory Design” which actively involves the user into the design process, leading to the designed product that meets the user’s specific needs. Participatory Design (PD) is an approach that is “characterized by concern with a more humane, creative, and effective relationship between those involved in technology’s design and its use” (Namioka & Rao, 1996). PD is started in Norway in the late 60s and early 70s with the development of the first object-oriented programming language. Since its inception more and more product designers are using this approach during their product development. PD assumes that: Users are experts; PD acknowledges the importance of using the expertise of users and treating them as equal partners on a design team. Tools should be designed for the context in which they will be used; PD realizes that an important step to designing new tools is to know where these will be used and in what context. This makes it difficult to design a tool away from the environment in which it will be used. There should be methods for observing or interviewing end-users; to gain an understanding of the environment in which the product will be placed and used, there are several techniques used to watch, observe, and interview users in their workplace.

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Recreating or play-acting a work situation will facilitate the design phase; it mediates the expectations of the users by not providing a non-functional prototype at the very beginning of the design phase. Iterative development is essential; the ideal PD project has several iterations of a design-feedback loop, where the designers ask the user for their opinion. Hereafter three cases will be discussed regarding the three domains of ergonomics and the phases of the design cycle.

7.2

CASE I: SENSORIAL ERGONOMICS – Abdominal wall tension measurement device

Text is based on and drawings are derived from the master thesis of N.A. Alvarez. Graduation project Delft University of Technology, Faculty of Industrial Design Engineering. (Alvarez, 2006).

7.2.1 Analysis Phase The abdominal wall is an important structure serving many different functions (Grässel et al., 2005). The two major functions are movements of the trunk and regulation of intra abdominal pressure. Moreover, it supports respiration and plays a role in stabilization of the spine. All these functions are facilitated by the coordinated and task specific activation pattern of the abdominal muscles. Due to its vital related functions, the abdominal wall is impossible to keep motionless even for a short period (Junge et al., 2001). 7.2.1.1 Intra Abdominal Pressure (IAP) Intra Abdominal Pressure (IAP) is the internal force that counteracts with the abdominal wall tension. As defined by the World Society of the Abdominal Compartment Syndrome IAP is “the pressure concealed within the abdominal cavity” (www.wsacs.org) (figure 7.2) .

Figure 7.2 Intra Abdominal Pressure (IAP).

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As mentioned before, muscles and IAP are directly related to each other (changes in posture and actions that involve abdominal muscles’ activation have an effect on the IAP). When IAP is measured in healthy non-obese adults during 13 different actions, the highest IAP was generated while coughing and jumping. It was also found that IAP correlated with the Body Mass Index (BMI) (Cobb et al., 2005). 7.2.1.2 Palpation There are different methods of physical examination of the abdomen: observation (inspection), percussion, auscultation (listening to the internal sounds of the body) and palpation. During superficial palpation the specialist assesses the abdominal area by evaluating with his/her hand the tension (tonus), tenderness and soreness of the abdominal wall as well as the presence of superficially localized resistances. The quality of the examination depends on specialist’s experience and the cooperation of the patient during this examination (figure 7.3).

Figure 7.3 Palpation of the abdomen.

7.2.1.3 Problem statement From literature it can be concluded that the abdominal wall tension is related with the IAP, which can influence the wound healing process. Therefore, abdominal wall tension is probably associated with development of incisional hernias (Cobb et al., 2005; Park et al., 2006; Song et al., 2006). IAP is currently measured by means of the bladder pressure, performed invasively with a urinary catheter and is considered an important element to be controlled after abdominal surgeries. IAP is an active measure influenced by many different elements such as the organs’ location and the abdominal wall’s muscular behaviour. For research purposes the abdominal wall tension can be calculated through mathematical models. In practice it is estimated qualitatively by means of palpation but there are no quantitative measurements done in patients yet. If the abdominal wall tension could be measured by means of a non-invasive device, research could be done to evaluate its relation in the development of abdominal conditions such as incisional hernia. Although many research would be

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necessary to find if there is a relation between the abdominal wall tension and the development of incisional hernias (or any other abdominal condition), the design of a device to measure such tension could be an initial step in that direction. The aim of this project was to design a device that measures the abdominal wall tension non-invasively. 7.2.1.4 User research: observational research To gain insight into the palpation process and to identify possible common procedural elements in the patient-specialist interaction, two different specialist were observed; an obstetrician and a gastroenterologist. Although the objectives of the examination and the patient’s abdominal wall’s muscular behaviour are different by these specialists, they both use their hands to evaluate the condition of the abdominal area, and they both first asses the tension and general situation of the abdominal wall. The observations focused on: Actions of the specialist during palpation. Other factors that could have an influence on the outcome of the examination, e.g. environment, kind of patient, etc. In addition, both specialists were interviewed before and after the examination. The results of the observations and interviews showed: During the examination of the abdominal wall different kinds of feedback are used for prognoses; Hardness of the abdomen is relatively evaluated with the reaction of the patient. General geometry of the abdomen, and expected situation of the structures underneath the “irregularities”. For assessment of the abdominal wall’s tension, both specialists pressed with a line of fingers (one or two hands indistinctively) and evaluate the amount of force needed to indent the fingers. Concerning the interaction, the patient had to be kept as relaxed as possible to perform the examination. 7.2.1.5 Technical research The technical research aimed to answer the questions related to the measurements: how to measure? and where to measure? Force measurement tests were done on different points on the abdominal wall with an existing force measurement device. These points on the abdominal wall reacted differently on the force measurement.

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7.2.1.6 List of requirements The requirements, expressed in terms of needs and desires, were divided in “Technical” and “Use” because these were the two main concern areas for the design of the device. Technical requirements were derived from the technical research and were complemented with those necessary to enable the usage of the tool in a clinical research setting. Grouped in “Input”, “Data processing” and “Output”, these requirements were addressed mainly to software qualities, although the inclusion of the position measurement involved usage qualities with impact either on the hardware and/or the software. The applied requirements (grouped in “specialist” and “patient”) included those elements that would have an indirect impact, through the actions or reactions of the users during the measurements. From this set those requirements related to the patient where directed to the tool’s aspect and interface that should point to keep the patient “relaxed”. Summarizing, the concept development should focus on a design for a device to measure the abdominal wall tension by means of force and distance. To facilitate research purposes, the possibility to record elements correlated with the basic measurements, as well as the option to measure and tracks one to seven different points on the abdomen should be included. Such device should be possible to be used in a clinical setting (e.g. intensive care unit, examination room), considering the patient’s reaction on the measurements. 7.2.2 Synthesis Phase Based on the list of requirements four concepts were developed. The main intention was to explore and define the interaction between the specialist, the device, and the patient. The main aim was to consider different possible ways in which the measurements could be performed in a fast and efficient way while the patient was relaxed. These concepts were evaluated afterwards concerning their feasibility to be made into prototypes in a short time.

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Table 7.1 Concepts

Concepts Concept 1

Concept 2

Concept 3

Concept 4

Mean features Soft, warm and semi transparent material containing an array of coupled force and distance sensors. One side ended in the microprocessor, which included input (touch screen or buttons) and output (screen, USB port to download information, etc.) and on the opposite side a counter weight fixed the belt. As the different sensors were fixed on the belt, which at the same time was centre with the middle line and the navel, there was no need to leave marks on the patient or on the device to recognize the points measured the previous time. A pair of “glove like” devices with the sensors in the core and an external replaceable latex protection, which can be used in a similar way as current palpation procedure. On the navel a kind of Global Positioning System (GPS) tracked the position of the measurements every time the hand sensors were activated, sending the sensors’ information along with the relative coordinates. All the components were linked to a microprocessor to control the sensors and store the obtained data. A soft blanket of an elastic material, located over the patient’s abdomen to keep the abdomen warm, intended to enable the specialist to measure on the entire surface as it tracked the point where the pressure was applied. The hand held device measured distance and the blanket measured force and position. Information from the hand device was transmitted wireless to the microprocessor. The big surface area covered sufficiently both thin and big abdomens. One hand tool with one pair of force and distance sensors held by the specialist over the patient’s abdomen. For tracking the points, a grid of silicone with wholes that recorded the position of the measurement. Also connected to a microprocessor.

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7.2.2.1 Concept evaluation For the evaluation of the four concepts a selection of the list of requirements was made. The concepts were evaluated regarding: cost, availability of components, amount of parts, easiness of use and technical complexity. The fourth concept was chosen, as it contained the fewer components, which were commercially available (except from the positioning grid). Another important feature of the chosen concept was its possibility to be modified, as the hand tool could be updated without necessarily affecting the software. 7.2.3 Simulation Phase The chosen concept was re-evaluated and the functions were divided into hardware and the software, looking for flexibility, efficiency, and possible cost reduction. One of the main changes made during detailing was the elimination of the siliconepositioning surface. Its functions were reassigned. Regarding the internal detailing, once the sensors were defined and their dimensions known, sketches were done to define the structure. A prototype of the design proposal was built to evaluate the dimensions, construction, and function of the internal structure (figure 7.4). The final shell was made by means of rapid prototyping for user research. Figure 7.4 presents the prototype and figure 7.5 a rendering of the final design.

Figure 7.4 Prototype

Figure 7.5 Rendering of the final design.

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7.2.4 Evaluation Phase The prototype was evaluated in an experimental setting (figure 7.6). Eight different points were measured regarding the exerted force and the distance. The prototype was connected to a PC for data recording.

Figure 7.6 User research.

The prototype could transport the recorded values of force and distance correctly to the PC. The prototype was used without any problems. 7.2.5 Decision Phase During this phase several recommendation were made: The force sensor used in the user research should be replaced with a calibrated one and the software should be detailed to subtract the resistance of the spring in the measurements. The interface has to be transferred from a desktop version to the pocket PC version. This interface is necessary if the test is going to be done in the clinical setting. In a clinical setting the prototype should be evaluated to assess how patient characteristics like BMI, age, gender, etc influence the measurements. This test could be used to estimate the possibilities and limitations of the tool.

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7.3

CASE II: COGNITIVE ERGONOMICS - Improving ergonomics of minimally invasive surgery - getting the most out of an integrated suite

Text is based on and drawings are derived from the master thesis of G. Scheepens, graduation project Delft University of Technology, Faculty of Industrial Design Engineering (Scheepens, 2007).

7.3.1 Analysis Phase 7.3.1.1 Problem statement The Karl Storz OR1 integrated suite is implemented in one of the ORs of a teaching hospital. This integrated suite is capable of providing an ergonomically sound working environment, but now it is not used to its full potential. An explorative observational study showed that indeed the positioning of supporting equipment is a major source of physical inconvenience for the surgical team. Therefore, this project focused on the positioning of surgical monitors. During the developments of the concepts two surgical procedures were kept in mind, laparoscopic cholecystectomy (LC) and gastric bypass. These procedures were chosen because the LC takes only 45 minutes and are performed mostly by novice surgeons while the gastric bypass takes up several hours and is performed by an expert surgeon. During these procedures the designed product needs to ensure an ergonomically sound surgical monitor placement. The aim of this project was to improve patient safety by enhancing the working environment of the surgeon, creating an ergonomically sound workspace for the surgical team, focusing on the positioning of surgical monitors, where correct positioning is defined as compliance with the ergonomic guidelines. Many other factors influence the working environment, ranging from the design of instrument handles to the illumination of the operating room. The problem to solve within this project reads as follows: Design of a product that supports users in placing monitors in an ergonomically optimal position. It should work with or be an add-on to the Karl Storz OR1 integrated suite. A connection needs to be made between the ergonomic possibilities the integrated suite offers and OR staff who actually uses these possibilities. The main problems identified were: Awareness: Observance of ergonomic guidelines during surgery needs to be enforced and encouraged. This includes communicating that there is a possibility to adjust the settings and why it is important to do so.

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Interaction: Optimal configuration of the equipment needs to be apparent during its positioning. This includes feedback about what the correct settings are, what these are for and how these can be adjusted. Continuity: For every MIS procedure correct positioning is needed and therefore must invoke its use every time a procedure is prepared. To solve the problem, its sub-problems have been divided over the seven characteristics of good interaction design to provide focus points during the synthesis (Saffer, 2007). The characteristics are of equal importance. 1) Trustworthy The product should prove that it is capable of helping the circulating nurse the monitors, it will be likely that there will be surgeons that demand a different setting than the optimal. Availability of the product is essential, it should always work and be present and not be especially be switched on or fetched from afar. To get the surgical team to trust the product, results are essential, on short term in the form of feeling of working in an environment adapted to them and in long term as decrease of physical complaints. 2) Appropriate The product should fit with the OR environment and work within its boundaries. Its communication should be innovative, inviting and effective; it should not take away attention from more important informational devices. The boundaries of OR1 should also be respected (not hinder other functionalities of OR1). Although the product should somewhat force its use on the users, it should allow its users to have the freedom to do what they like. The desire to use the product should be directed at the surgical team and the circulating nurse, while the “how” of the use should be directed towards the circulating nurse. The product should be self-explanatory. 3) Smart The product should support its users in doing that what can be difficult in the demanding OR environment, remembering to position monitors, guidance in where monitors should be placed and propagate the need for positioning the monitors. The positions for the monitors are not absolute and need to be adjusted to the surgeon, specific procedures and to other equipment. Not always is the most ideal position the most optimal position. It is up to the product to direct towards preferred positions and prevent incorrect positioning.

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There are many skills that are better developed in humans than in machines and the products’ responsibilities should not try to replace those skills. 4) Responsive The product should communicate incorrect positions as well as correct positions, without annoying users by creating saturated feedback in which important changes are difficult to detect. 5) Clever Using the product should ease workload, by taking away confusion and disagreement about what the correct positions of the equipment are. Taking away confusion about how settings relate to the human body and who has set specific preferences and what these are as well. 6) Lucid (playfulness) Making errors in positioning monitors should be made difficult instead of displaying warnings. The opportunity to undo and redo actions is also important, so the users cannot get the feeling that pressing a button can get them trapped in a part of the system they do not need to visit. Confirming key actions comforts the users and reassures them that accidentally pressing a wrong button cannot lead to serious consequences. This last option gives them the opportunity to use and learn the system by browsing around, without it having serious consequences. 7) Pleasurable There are two sides to pleasure in using products: aesthetic and functional. People are more easily content with the performance of a beautiful product, products that look good are more pleasurable in use and will be used more and better (Tractinsky et al., 2000). Not neglecting this quality needs to be combined with the product functioning properly, obviously improper functionality leads to frustration and irritation in product use. The product does not need to fit the visual aesthetics of OR1’s software since these are about to change drastically in the near future.

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7.3.1.2 List of requirements This list of requirements is based on the problem definition and design vision and Bitterman’s specific conditions and restrictions typical for the OR (Bitterman, 2006). 1. The product will need to be used by inexperienced and experienced users, since in some hospitals the employee directory can change rapidly. 2. During some procedures two people view one monitor. 3. The maximum time during which the product can be used is three minutes. 4. There is no time for users to learn how to use the product. 5. Before the first trocar is inserted the preparation of the procedure needs to be complete, this includes equipment positioning which should not hinder other parts of the preparation. 6. During the procedure the system should not hinder any activities and should comply in case of unforeseen events (e.g. converting a MIS procedure to an open procedure). 7. Therefore the product should… a …be silent. b …not take up much space. c …not cause electromagnetic disturbances. d …not interfere with sterility during the procedure. e …not affect the OR temperature. f …not interfere with the illumination of the procedure (cast shadows, etc.). g …not be visually distracting. 8. The product’s performance should not be affected by the characteristics of the OR environment. The product should be able to withstand… a …the vapours caused by surgery. b …moisture deposits on it. c …thorough cleaning activities 9. The product should always be directly available, charged and switched on when OR1 is in use. 10. The product should posses a possibility to have its standard settings changed and have personalized settings created. 11. The life span of the product should be longer than at least ten years. 7.3.2 Synthesis phase 7.3.2.1 Idea evaluation Eight ideas for equipment positioning were generated and evaluated along the design vision based on the factors awareness, feedback, continuity, and viability (figure7.7). Other factors contributing to the evaluation are the positives and difficulties of every idea.

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Figure 7.7 First-phase ideas: Eight ideas meeting the requirements and evaluated (rating in stars) on four aspects: Awareness, Feedback, Continuity and Viability. The italics lines capture the reasons for the particular ratings in a single line.

Figure 7.7 provides a quick assessment of all the ideas’ pros and cons, but some influence the choice for a particular idea more than others. Awareness, feedback and continuity are equally important, but a high score on viability is essential for the successful implementation of an idea on short term. A low-tech solution has the most potential at the moment. The first-phase ideas (figure 7.7) are technically quite complex and will be difficult to prototype and are more future solutions. Of the first-phase ideas, ideas 5 and 8 seem to be the most promising. Idea 7 does not comply with the need to be an add-on for the integrated suite and “advice” is a

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relatively expensive solution (viability problems). Finally, the visual feedback solution was chosen to elaborate.

Figure 7.8 Second-phase ideas: Evaluation on eight aspects of two promising design directions.

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7.3.3 Simulation phase The most viable concept was the visual feedback solution in which a Light Crystal Diode (LCD) screen on the monitor’s back gives feedback on the ergonomics of the monitor position. A user research was designed mainly to test the usability of the product. Though initially planned, approximate positioning could not be tested. The product was validated with a simulated prototype in the hospital. The set-up consisted of a cart that was used for MIS before the integrated suite became available, with a boom-arm attached monitor (figure 7.9). At the back of the monitor a small video display was attached that displayed the image from a camera mounted on top of the monitor. A laptop was used to project an image overlay on the video.

Figure 7.9 Set up user research.

There are several points of attention that emerged from the user research. Most importantly, distance assessment needs to be improved. The reaction of the surgical team towards the product (or at least towards someone looking into this matter) is favourable. This can also be concluded from the fact that 21 subjects participated in just a few hours and the fact that in the afternoon people started to come in after hearing about the user research from colleagues. 7.3.4 Evaluation phase The results of the user research are used to improve the design proposal (figure 7.10). The essential element of the final product is the LCD that communicates ergonomic positioning of all team members to the circulating nurse. They are the people that have the most direct need for feedback about equipment positioning

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and are most likely to welcome it. This feedback on the LCD is available during the entire procedure; the LCD’s are mounted to the monitors’ backs and their illumination is therefore directed away from the surgical team.

Figure 7.10 Final design.

7.3.5 Decision phase The final design proposal should be evaluated with the users. Regarding the results of this user research the final design proposal should be improved for production. Future versions need to be integrated and joint ventures need to be considered, to be able to provide a complete solution.

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7.4

CASE III: PHYSICAL ERGONOMICS - Design of a handle for curved instruments

Text is based on and drawings are derived from the master thesis of F. Hoolhorst, graduation project Delft University of Technology, Faculty of Industrial Design Engineering (Hoolhorst, 2005).

7.4.1 Analysis phase Minimally invasive surgery (MIS) is a universally adopted way of surgery next to the conventional open procedures. The patient benefits from MIS. However, the disadvantage for the surgeon and his team are bad ergonomics, longer operation times, higher budget for OR equipment, less freedom of movement and the need of extra training. Therefore, new methods and products to improve MIS are regularly introduced. 7.4.1.1 Problem statement At this moment, most of the instruments that are used during MIS are straight and long instruments. It is believed that curved instruments might offer a solution to some ergonomic problems of the surgeon (figure 7.11). Especially when used in solo-surgery, i.e. a form of surgery in which the numbers of team members is minimized.

Figure 7.11 A curved and straight instrument.

The current curved instruments still introduce many problems in the field of physical and cognitive ergonomics. Van Veelen states that problems in this field may lead to higher muscle-activity of the surgeon, resulting in fatigue and discomfort for the surgeon, excessive pressure on sensitive areas of the hand and fingers causing nerve injuries (van Veelen, 2003). The aim of this project was to improve the handle of a curved instrument, paying extra attention to ergonomic problems of the current handles. 7.4.1.2 List of requirements Literature was reviewed on curved instruments, handles for MIS instruments, anatomy of the shoulder, elbow, wrist and hand and body posture. In addition, a practical study to evaluate the use of current curved instruments in the OR was

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performed A set of requirements for the new handle was formulated. The most important requirements are described below. Functional requirements The handle allows one-handed use. The handle can be used with an existing shaft. The handle allows force grip and precision grip. The handle incorporates opening and closing of the tip. The handle allows for fixation of the tip. The relation between force exercised on the handle for opening a closing of the tip and the force on the tip is between 1:5 and 1:7. Ergonomic body posture and instruments comfort The handle can be held comfortably for different rotations within certain limits. The handle should be operated by the sensitive area of the hand. Functional elements like buttons should be easy accessible. The shaft of the instrument has to be in-line with rotation of the forearm. Low muscle activity is necessary to manipulate the functional elements. 7.4.2 Synthesis phase Based on these requirements different ideas were generated. Several product ideas were based on a bar shaped grip (figure 7.12). Other ideas were based on pistol handles (figure 7.13) and finally mouse handles were sketched (figure 7.14).

Figure 7.12 Product ideas for a bar shape grid.

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Figure 7.13 Product ideas for a pistol handle.

Figure 7.14 Product ideas for a mouse grip.

Based on these ideas two concepts for a new handle were introduced. The handles’ shape was based on different clay models and technical principles for opening, closing, and fixation of the instruments were made (figures 7.15 and 7.16).

Figure 7.15 Concept 1.

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Figure 7.16 Concept 2.

7.4.2.1 Idea evaluation The concept choice is based on the evaluation of the idea regarding the general guidelines and requirements that were defined earlier in this project. The requirements were of equal importance. The concept meeting the most requirements was chosen for further development. Some of the requirements could not be used during this phase. Concept 1, based on the mouse grip, met 12 of the important requirements, against Concept 2 that met only 10. Therefore, Concept 1 was chosen to be materialized. 7.4.3 Simulation phase The final design was based on the grip of a ball of Ø50 mm. This ball shape has two asymmetric surfaces, which provide the surgeon a more stable grip. Also by doing so, the grip provides the surgeon feedback on the orientation of the tip. The shape of the buttons has been optimized in order to improve the control. Figure 7.17 shows the final product design.

Figure 7.17 Final product design.

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7.4.4 Evaluation phase The prototype was evaluated in a simulated environment in the OR (figures 7.18 and 7.19). The tasks of the subjects were to cut out a circle (diameter 40 mm), which was drawn on a piece of paper. For executing this task, in the left hand the curved instrument was held. Each subject had to perform the test twice, namely with a straight instrument and with a curved instrument with the new handle. During execution of the user research, the body posture was recorded with two cameras. After the user research, the posture was visually inspected every ten seconds during the task and the following joint angles were measured: Angle of the elbow. Flexion and extension of the wrist. Horizontal flexion of the shoulder. Pronation and supination of the forearm.

Figure 7.18 User research in a simulated OR environment.

Figure 7.19 User research during cleaning and sterilization.

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The results of the user research are shown in figure 7.20. The results are based on a comparison, which was made with an existing straight instrument. The circle diagrams give insight into the subjects’ body posture during the user research. These show how long a certain posture was adopted. The green parts show how long a body posture was adopted regarding the ergonomics guidelines. Practically, no differences could be found in the elbow’s posture. For both instruments, the angle between the upper arm and forearm was almost constantly held in the green zone. It seems that instruments handles do not only influence the posture of the elbow. Elbow posture is mainly influenced by the height and the angle of the instrument’s tip. The main difference in body posture could be found in the flexion and extension of the wrist. With the prototype, the wrist was adopted in an ergonomic posture for 85% of the time. The horizontal flexion of the shoulder was always within the ergonomic zones. There was a slightly difference in the pronation and supination of the forearm. The posture using the prototype was 20% of the time not in the ergonomic zone and for the curved instrument this was 26%.

Figure 7.20 Results of the user research.

7.4.5 Decision phase At the end of the project it was concluded that the new handle design has many advantages with respect to the already existing MIS handles. 7.4.5.1 General design The new handle provides an integral design solution. The ball shape allows hiding controls that can disturb the surgeon during his activity.

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7.4.5.2 Ergonomic comfort The user research results indicated that many ergonomic advantages are expected for the handle. The handle also allows the surgeon to assume a more ergonomic posture. 7.4.5.3 Indications from the user research Remarks of the test subjects during the research indicated that the new handle did not cause pressure points on the hand during use. Furthermore, subjects experienced the prototype as comfortable. Another advantage is that both hands can use the handle.

7.5

CONCLUSION

This chapter showed the several disciplines of ergonomics and its related problems. All of projects are developed and researched by means of the basic design cycle of Roozenburg and Eekels as a design framework. Within each design cycle all domains of ergonomics are included. However, the focus is different. In addition, the problem statement and the amount of available information in analysis phase influences the outcome of other phases. For example, in case of product redesign information on working principles, material, production, and usage are already available. These can be used as valuable input for the synthesis phase. In case of a new innovative product no information is available. This has to be researched in the analysis phase, reducing the amount of time to be spent in other phases such as evaluation by means of user research. This shift of focus is reflected in the three described cases. The differences are discussed briefly. 7.5.1 Case I: Sensorial measurement device

Ergonomics

–

Abdominal

wall

tension

The starting point of this case was rather hypothetical. The assumption was that the abdominal wall tension was probably associated with development of incisional hernia. There was no quantitative method available to measure the abdominal wall tension directly on patients’ abdomen which means that questions as: What to measure? How to measure? and Where to measure? arise. The hypothesis that abnormalities in the abdominal wall tension were associated with development of incisional hernia was an answer to the question “What to measure?”. By measuring the abdominal wall tension an indication of a potential development of incisional hernia was obtained. The next question was “How to measure?”. The performed observational research and interviews with the specialists gained insight into which factors are relevant to formulate a prognosis.

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From this research it has concluded that the level of force exerted needed to indent the fingers was a valuable feedback for the specialist. An existing force measurement device was used to evaluate this principle. Since the abdominal wall has different structures it was important to assess, which points will provide reliable data. As should be clear the design team had a lack of knowledge and therefore from a very early phase in the design process input from research and feedback from the user was needed. The adjusted design cycle for this case is illustrated in figure 7.21.

Input from observational research and interviews Input from technical research performed with an existing force measurement device

Figure 7.21 Adjusted design cycle Case I.

The outcome of this project was a working prototype. With this working prototype user research was performed to evaluate the design proposal. Because of the extensive analysis phase, which was time-consuming, the user research was only superficial. However, the design proved to be a good starting point for further product development. 7.5.2 Case II: Cognitive Ergonomics – Improving ergonomics of minimally invasive surgery- getting the most out of an integrated suite. The starting point of this case was very different from the previous case. There was already an integrated suite available and this suite was capable of providing an ergonomically sound working environment. Therefore, define the pre-conditions of the design proposal. However, the ergonomic possibilities were not used to its full potential. Design team’s approach was: first assess why the surgical team was not

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using the already existing functionality and second how to convince them to use the functionalities. After an observational study, it became clear that the positioning of supporting equipment was a major source of physical inconvenience for the surgical team. The focus was on positioning the surgical monitors. Anticipating on future developments, OR aesthetics and usage, the design had to be an interface. Therefore, approach from the interaction design was chosen as a starting point. Seven characteristics of a good interaction design, which were already evaluated by other experts, were used during synthesis phase to convince the surgical team about its benefits. As should be clear the design team already knew in an early phase of the design process what to design and therefore the project focused on how to design. The adjusted design cycle for this case is illustrated in figure 7.22.

First feedback from user research

Results of user research led to improvements of the design proposal

Figure 7.22 Adjusted design cycle Case II.

The outcome of this project was a detailed simulation. The performed user research with this simulation was in-depth resulting in an improvement of the design proposal. 7.5.3 Case III: Physical Ergonomics – Design of a handle for curved instruments The starting point of this case was as Case I rather hypothetical. The assumption was that curved instruments might offer a solution to some ergonomic problems experienced by the surgeon. Although, this case had a hypothetical starting point

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there were differences with Case I. In this case, there was an existing curved instrument, which had limitations that had to be improved. This well-defined and focused starting point of the process increases the level of elaboration in the next phase of the design cycle. In the synthesis phase next to the drawings, early models (i.e. clay models) were used to evaluate the shape and some technical principles. This gives the design team the advantage of anticipating on the future use of the product. With the knowledge gathered from the first user research the quality of the final design proposal was improved. The adjusted design cycle for this case is shown in figure 7.23.

Knowledge gathered from existing curved instrument

User research with early design models to evaluate the shape and technical principles

In-depth user research by comparing the existing curved instruments with the prototype

Figure 7.23 Adjusted design cycle Case III.

The outcome of this project was a detailed prototype. With this prototype, a user research was performed whereby the existing straight instrument was compared with the prototype of the design proposal. The results of this user research were sufficient to evaluate the design proposal objectively.

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CHAPTER 8 DISCUSSION The transition from open to image-based surgery has changed surgical practice in many perspectives as a consequence of application of advanced high technology in the operating room. The increasing dependency on technology to perform surgical procedures has introduced ergonomic problems for the surgical team (Berguer, 1999). From this perspective it is not surprising that most of the errors in healthcare are related to surgical procedures (Kohn et al., 2000; Moorthy et al., 2004; Verdaasdonk et al., 2007). Therefore there is a societal motive to improve patient safety by reducing medical error rates (IGZ, 2007). Hence both the surgical environment and the human-product interaction have to be analyzed and improved (Cuschieri, 2000; Verdaasdonk et al., 2007). Patient safety and surgical quality are two notions, which are related to each other. Patient safety can be improved by enhancing surgical quality. Surgical quality can be influenced by a variety of organizational and social aspects such as time pressure and inadequate team work but also by human-error due to poor ergonomic conditions such as excessive workload, fatigue, poor human-product interaction, etc (Moorthy et al., 2003a; Reyes et al., 2006). Improvement of surgical quality requests a multi-disciplinary approach, focusing on technologydriven trends and on the other side on societal motive and ergonomics. This includes designs aimed at satisfying human needs and extending possibilities for the medical staff, like nurses, medical specialists and for patients. Besides involving the problems of human-product interaction and the development of new technologies, multi-disciplinary approach also guard the improved opportunities and working conditions of specialists.

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For the Faculty of Industrial Design Engineering (IDE) it means that it will have to educate designers capable of translating the practical needs of the healthcare sector into products specially designed for medical applications in low-tech as well as high-tech applications. In this way, they can contribute to the diagnosis, treatment and prevention of disease and disorders (Goossens et al., 2007).

8.1

Design framework

8.1.1 Methodology At the start of a design process the design team often knows little about the user group, the context and the interaction between the user and their environment. When a design team is involved in the development of a healthcare system they need to gain a total overview that often goes beyond their own knowledge (Kersten et al., 2007). The medical specialists are professional users with specific needs, work conditions, language, culture and work environment. For a design team the first step to understand the problems of the user is gaining insight into the profession of the user group. A design team will get familiar with their profession and problems by literature study, observations, and interviews. The obtained information from practice will be a good start for the design team in the design process. Especially when the user group and their context are unknown for the design team, field research is a suitable method to explore and obtain information from the first hand (Babbie, 2004). Field research has a high ecological validity since all restrictions and conditions from practice are involved in the research. However, field research has its restrictions. Compared with experimental study, field research measurements generally have more validity but less reliability. Also, field research is generally not appropriate for statistical analysis (Babbie, 2004) but the results of a field research are necessary to make assumptions regarding observed problems. These assumptions can further be tested in an experimental research. In this controlled research environment the design team can study the relationship between independent and dependent variables (Graziano & Raulin, 2000). Experiments are suitable for the controlled testing of causal processes (Babbie, 2004). The primary weakness of an experiment is artificiality. The results of an experiment may not reflect the real world (external invalidity) (Babbie, 2004). In this PhD-research both field research and experimental research is applied (figure 8.1).

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Figure 8.1 Overview of the research methods used in this PhD-thesis.

In Chapter 4 study on the discomfort during surgery and evaluation of the developed ergonomic body support as a product solution is discussed. This study starts with a field research wherein observations in the operating room and interviews with users were done. In addition, from the early beginning of the design process the user was involved. In the regular meetings with the users the possible solutions and argumentations were discussed. The gathered information during meetings with the users where used to improve the design proposal. In these interactive meetings, feedback to the user was important to check if the knowledge gathered from the user was interpreted correctly by the designer. Feedback from the user provides knowledge from the “professional” users to the design team and serves as an early evaluation of possible solutions. This early evaluation affects the level of detail of the final design proposal. In the case of the body support (Chapter 4) a working prototype was built whereby different aspects of the design proposal could be evaluated. The final evaluation of the design was done with surgeons in the operating room. This way of user research allows the designer to validate the design proposal within the limitations and restrictions of the operating room. Next to the field study also an experimental study was done in a lab-setting wherein the muscle activity was measured. The advantage of such a controlled experiment was the possibility to look at interrelationships and validate the theoretical biomechanical model.

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In Chapter 5 the study on image quality is discussed. This study was explorative of character and is conducted in the operating room. During this study it was hard to control the research set-up. Between two procedures there was limited time to do measurements and simultaneously the patient had to be transported and the operating room had to be cleaned and prepared for the next procedure. Collecting data in this atmosphere was challenging. The measurements were standardized as far as possible and therefore gain good insight into the practice. However, by analyzing the data it became clear that some assumptions, such as the surgeons’ subjective experience of the displayed image, could not be verified. Since this research was conducted in field there were restrictions to control the research setting. It might be interesting to study surgeons’ subjective experience of the displayed image in a controlled experimental setting. Either in field research or experimental studies, involvement of the user in an early stage of the design process is essential. Where the user can indicate and describe their problems and needs, the role of the design team is to discover the relationships between product usage, context, and user problems. Both field research and experimental studies are valuable and will provide the design team information and new perceptions necessary for the design process. 8.1.2 The basic design cycle The basic design cycle according to Roozenburg and Eekels is a framework that can be used during product development. The iterative process of the basic design cycle gives the possibility and flexibility to involve the user in each design step (Roozenburg & Eekels, 1995). The cases discussed in Chapter 7 show examples how user research is integrated into the design process. These cases also show that the problem statement and the amount of available information in the analysis phase influence the outcome of the next phases. For example, in case of redesign, information on working principles, material, production, and usage are already available for valuable input for the synthesis phase. In case of innovative products no or little information is available which has to be researched in the analysis phase, reducing the amount of time to be spent in next phases such as evaluation by means of user research. A hypothetical start like in Case I, extends the analysis phase. Due to lack of existing or similar products, it is time-consuming to collect the relevant information. Because of time constraints of the project the user research in the end of the process could only be carried on a small amount of data. The outcome was a good starting point for further product development.

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A start whereby the preconditions of the design proposal are already defined but ergonomic possibilities of the design proposal are not used to its full potential like Case II asks for a different approach. The design team already knew in an early phase of the design process what to design and therefore the project focused on how to design. The outcome of this project was a detailed simulation and the user research was in-depth resulting in an improvement of the design proposal. In a redesign project like Case III the starting point was hypothetical but there was an existing product, which had limitations to improve. This well-defined and focused starting point of the process increases the level of elaboration in the next phase of the design cycle. In the synthesis phase next to the sketches, early models (i.e. clay models) were used to evaluate the shape and some technical principles. This gives the design team the advantage of anticipating on the future use of the product. With the knowledge gathered from the first user research the quality of the final design proposal was improved. The outcome of this project was a detailed prototype. With this prototype, a user research was performed whereby an existing laparoscopic instrument was compared with the prototype of the design proposal. The results of this user research were sufficient to evaluate the design proposal. The products designed at IDE include user research in different phases of the design cycle, in which the intended end-users are actively involved. However, this research sometimes has to be conducted in an experimental setting. Especially when designing products for the OR, it is difficult to test these in the sterile field.

8.2

Surgical Quality

From an ergonomic point of view the surgical quality can be defined as; “the level of efficiency, safety and comfort of a surgical procedure (van Veelen, 2003). “Efficiency was defined as the coefficient between effort and benefit. In this definition effort also implies product life span and learning and understanding the use of the product (e.g. it can take several months to learn how to perform a task without errors). Safety deals with the wellbeing of the user (in the case of minimally invasive surgery also the wellbeing of the patient) and the prevention of injury. Comfort was defined as a physical and mental state in which one is not aware of any discomfort”. In this PhD-thesis the relationship between the three notions of surgical quality is interpreted as; “By creating a comfortable working environment for the surgical team the efficiency of the procedure may increase since less effort is needed to achieve the same result. Because of the increased comfort and efficiency, patient safety may improve since the surgical team may concentrate more undisturbed on their primary task, namely performing a surgical procedure” (figure 8.2).

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Figure 8.2 The three notions of surgical quality.

The study on the physical discomfort of surgeons has resulted in development of an ergonomic body support. It was well-known that surgeons had physical complaints due to their poor body posture during surgery but a relevant product solution for this situation was not available (Albayrak et al., 2007; Berguer, 1996, 1997; Berguer et al., 1997; Kant et al., 1992; Mirbod et al., 1995; Nguyen et al., 2001; Schurr et al., 1999; van Veelen et al., 2003b; Vereczkei et al., 2004; Wauben et al., 2006). Preliminary the design proposal, analysis was done and a biomechanical model was used to verify the supporting principle. Of the final design proposal a working prototype was built and user research was done. During this user research it is shown that muscle activity, which was a measure of discomfort, is reduced by using the body support and surgeons found the body support comfortable in use. An user research wherein the product solution was evaluated with 16 participants shows that users adapting different balancing strategies while using the body support. It seems that different kind of users exists and the level of experienced comfort may depend on how the body support is used. These intra-individual differences in usage will influence the efficiency and therefore also the safety. It is hard to measure the improvement of surgical quality objectively. However, the results of these studies have created awareness among the surgeons about their poor body posture, showed that a solution is available and lead to different practical ergonomic solutions (Chapter 6) which they can apply in the operating room. The study on image quality was a large-scaled research in which 36 Dutch hospitals participated. The number of the involved hospitals makes the findings representative. In spite of the societal motive to improve patient safety it was surprisingly to discover that at the time of visits almost none of the visited hospitals

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tested the components of the imaging chain regularly and components were only tested in case of malfunctioning. The results of this study shows a variety of imaging systems used in hospitals and that a large number of endoscopes and light guide cables had insufficient light transmission qualities. The findings of this study have lead to the realization and the importance of introduction of a quality control program. After the visits already some of the hospitals introduce the quality control program in their hospital. Furthermore, a recently published report by the Dutch Inspection of Health Services “The underestimated risks of minimally invasive surgery” refers to the first publication of this study and pleads for introduction of quality control program on national level. Since most of the errors in healthcare are related to surgical procedures, regularly controlling the equipment is not a redundant action and will reduce the product related problems.

8.3

Future research

During this PhD-thesis research has been done on the ergonomics in the operating room. During the PhD-project, new research areas have been defined. The result of the study discussed in Chapter 4 shows that users adapting different balancing strategies while using the same product in the same context. This leads to the question of which aspects define the intra-individual differences. A research on this topic may gain insight into the considerations, which a user makes while using a product. The study in Chapter 5 discusses surgeons’ subjective experience of the displayed image. More research on this topic seems interesting to discover the relation between the quality judgment of the surgeon and the arguments of making a judgment. Finally, another interesting research area is on the applied methodology when designing for professional. The research on this topic may lead to improvements of design methodology for development of products for the operating room.

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148

SUMMARY

At several specializations, more often minimal invasive procedures are performed in addition to open surgery. Laparoscopy is a minimal invasive technique, which is carried out in the abdominal cavity. The first laparoscopic cholecystectomy, removal of the gallbladder, was performed in Germany in 1985 by a surgeon named Eric Mühe and since then this type of procedure is worldwide applied. This popular technique has become the “gold standard” for gallbladder removal and provides many advantages for the patient. The first step of a laparoscopic cholecystectomy starts with inflating the abdomen of the patient with carbon dioxide. By several small incisions, laparoscopic instruments with which the surgeon performs the procedure are inserted into the abdomen cavity. The dark abdominal cavity becomes illuminated by a light guide cable, which is connected to one end with a light source and at the other end with the endoscope, which is positioned in the abdomen. The endoscope transmits the image of the abdomen of the patient by means of a camera to a monitor. The surgeon performs the procedure based on this image. Concerning the sterility, the required equipment is positioned on a trolley, which stands outside the range of the surgical team. In spite of the fact that surgical principles are the same for open and laparoscopic procedures, laparoscopy has changed the way of interaction between the surgical team and the operating field in many ways. These changes however have not led to the required adaptations in the operation room to improve the surgical quality and to optimize the work conditions of the surgical team. In this respect, ergonomics can play a role to fit the work environment to the user and improve the surgical quality accordingly. The aim of this thesis is to improve the surgical quality by applying ergonomics (physical, sensory and cognitive) in the operating room.

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First, in chapter 2, the ergonomic problems are discussed with sub-chapters in physical, sensory, and cognitive ergonomics. In open surgery, these problems are frequently of a physical nature. The physical complaints are often caused by the uncomfortable posture and the occasional need to exert substantial forces on tissues during the surgical procedures. In comparison with laparoscopic surgery, the sensory and cognitive problems are relative less at open surgery. By the presence of a large incision, the surgical team can see, feel, and manipulate the organs. This way of interaction is more natural than during laparoscopy. The interaction between the operating field and the surgical team has changed with laparoscopic surgery since the surgeon must manipulate the instruments and perform the procedure by means of the image on a monitor. During a laparoscopic procedure, the tactile feedback is limited and there is no direct perception of the organs. Frequently, the surgeon stands uncomfortable and by the static posture, physical complaints are experienced. The problems appear in the sensory area are mostly caused by the incorrect positioning of the monitor, which often cannot be positioned according to the ergonomic guidelines, namely in the field of view of the surgeon and in line with the work area of the hands. On cognitive field problems occur as a result of intrinsic factors of laparoscopic viewing. In chapter 3, the current situation in the Dutch hospitals concerning ergonomics and the aptitude of the operating rooms for laparoscopy is mapped out. For this research, twenty-nine hospitals where visited and an inventory of their equipment such as trolleys and monitors, which are necessary to perform a laparoscopic surgery, has been made. In addition, the dimensions of the operating rooms and height adjustments of the operating tables have been recorded. The results of this research show that most of the operating rooms are not optimally equipped to carry out laparoscopic procedures. They have been built initially for open procedures and are often too small. Most of the monitors are positioned on a trolley that is not adjustable in height, which results in the monitors not standing in an ergonomic eye level. The operating tables could not be positioned, ergonomically seen, low enough for laparoscopy. Mainly by the small number of monitors and their wrong position, the surgical team frequently has an uncomfortable posture. The solutions and directives, which were raised in this study, were related to correctly positioning the monitors according to the ergonomic guidelines and optimizing the position of the surgical team with respect to the present monitors. The topics discussed in the previous chapters create an overview of the daily ergonomic problems, which the surgical team experiences as well as the possibilities, and insights of improving the surgical quality and work conditions of the surgical team.

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The physical complaints and the discomfort that the surgical team experiences during open and laparoscopic procedures has to do with uncomfortable posture, incorrect working height, fatigue due to static body posture and raised muscle activity to balance the body. In chapter 4, a product solution is proposed and the evaluation of this solution is discussed. The product solution, which is discussed in part 1 of chapter 4, is a body-support that supports surgeons at both open and laparoscopic procedures in their natural posture. The design process is described by means of the design cycle. A working prototype shows that the product solution meets the requirements of compactness, mobility, adjustability and is suitable for surgeons with different body statures. The first evaluation takes place with the surgeons in the operating room. In part 2 of chapter 4 the biomechanics, as underlying theory for the product solution, is deeper discussed. A research is done on the reduction of muscle activity by product use. Chapter 5 aims at the sensory and cognitive aspects of laparoscopic procedures and in particular at image quality during laparoscopic surgery. This study consists of objective and subjective measurements in thirty-six Dutch hospitals. The collected data did show that the quality of the components of the imaging chain was not optimal and that most hospitals did not have the equipment to test these components. There were large differences in light intensity of the image chain between the different hospitals and several types of surgical procedures. Chapter 6 reflects on the problems, which are described in chapter 2, and raises applicable practical ergonomic solutions. This chapter has been in particular intended for surgeons who want to tackle the problems, which appear during the procedures. Chapter 7 on the other hand, has been intended for the designers and describes the steps of the design cycle in a number of cases. These cases are subdivided in physical, sensory, and cognitive ergonomics and are related to the medical product development. In chapter 8, different methodologies applied in this thesis are explained. Two methods “field research” and “experimental study” are distinguished and the advantages and disadvantages of these methods are discussed within the context of this thesis. The design cycle of the cases, which are described in chapter 7, is assessed. It emphasizes (i) how the different steps of the design cycle influence each other, (ii) the role of the user research within the design cycle and (iii) how these two influences the development level of the product solution. The influence of the different studies, discussed in this thesis, on the improvement of the “surgical quality” is evaluated and, finally, a couple of interesting research directions, which can be studied more closely, are outlined.

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Bij verschillende specialisaties worden naast open chirurgie steeds vaker minimaal invasieve ingrepen uitgevoerd. Laparoscopie is een minimaal invasieve techniek die in de buikholte wordt uitgevoerd. De eerste laparoscopische galblaas verwijdering werd in 1985 door chirurg Eric Mühe in Duitsland uitgevoerd en sindsdien wordt dit type operaties wereldwijd steeds vaker toegepast. Deze populaire techniek is de “gold standard” voor galblaas verwijdering geworden en kent vele voordelen voor de patiënt. De eerste stap van een laparoscopische galblaas operatie begint met het opblazen van de buik van de patiënt met koolstofdioxide. Door kleine incisies worden laparoscopische instrumenten in de buikholte gebracht waarmee de chirurg de operatie uitvoert. De donkere buikholte wordt verlicht door een lichtkabel die met het ene uiteinde verbonden is met de lichtbron en het andere uiteinde met de endoscoop die zich in de buikholte bevindt. De endoscoop brengt het beeld via een camera over naar een monitor waarop het inwendige van de patiënt te zien is. De chirurg opereert aan de hand van dit beeld. De benodigde apparatuur staat op een trolley die buiten het bereik van het chirurgisch team staat in verband met de steriliteit. Ondanks het feit dat de chirurgische principes hetzelfde zijn voor open en laparoscopische ingrepen, heeft laparoscopie de manier van interactie tussen het chirurgische team en het operatiegebied op vele manieren veranderd. Deze veranderingen zijn echter niet gepaard gegaan met de benodigde aanpassingen in de operatiekamer om de kwaliteit van een chirurgische ingreep te verbeteren en de werkomstandigheden van het chirurgisch team te optimaliseren. In dit opzicht kan ergonomie een rol spelen om de werkomgeving aan te passen aan de eisen van de gebruiker en daarbij de kwaliteit van de operaties te verbeteren.

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Het doel van dit proefschrift is om de kwaliteit van de operatie te verbeteren door het toepassen van ergonomie (fysieke, sensorische en cognitieve ergonomie) in de operatiekamer. Als eerste worden de ergonomische problemen met een onderverdeling in fysieke, sensorische en cognitieve ergonomie in Hoofdstuk 2 besproken. Bij open chirurgie zijn deze problemen vaak van fysieke aard. De fysieke klachten worden vaak veroorzaakt door de oncomfortabele houding en de noodzaak van het uitoefenen van kracht tijdens de operaties. In vergelijking met laparoscopische ingrepen zijn bij open operaties de sensorische en cognitieve problemen relatief minder. Door de aanwezigheid van een grote incisie kan het chirurgisch team de organen zien, voelen en met de hand manipuleren. Deze manier van interactie is natuurlijker dan bij laparoscopie. De interactie tussen het operatiegebied en het chirurgisch team is bij laparoscopische ingrepen veranderd aangezien de chirurg de instrumenten moet manipuleren aan de hand van het beeld dat op een monitor te zien is. Bij deze interactie is de tactiele feedback beperkt en er is geen directe perceptie van de organen. De chirurg staat vaak oncomfortabel en door de statische houding ervaart hij/zij fysieke klachten. De problemen die optreden in het sensorische vlak worden veelal veroorzaakt doordat de monitor niet volgens de ergonomische richtlijnen gepositioneerd kan worden in het zichtveld van de chirurg en in lijn met het werkvlak van de handen. Op het cognitieve vlak treden problemen op als gevolg van intrinsieke factoren van het laparoscopisch beeld. In hoofdstuk 3 wordt de huidige situatie van de Nederlandse ziekenhuizen met betrekking tot ergonomie en de geschiktheid van de operatiekamers voor laparoscopie in kaart gebracht. Voor dit onderzoek zijn er in totaal negenentwintig ziekenhuizen bezocht en is er een inventarisatie gemaakt van de apparatuur dat nodig is om een laparoscopische ingreep uit te voeren zoals: trolleys en monitoren. Hiernaast zijn de afmetingen van de operatiekamers en de hoogte instelling van de operatietafels bepaald. De resultaten van het onderzoek tonen aan dat de meeste operatiekamers niet geschikt zijn om laparoscopische ingrepen uit te voeren. Ze zijn oorspronkelijk ontworpen voor open operaties en zijn daardoor vaak te klein. De meeste monitoren zijn gepositioneerd op een trolley die niet in hoogte instelbaar is, waardoor de monitoren niet op een ergonomisch verantwoorde ooghoogte staan. De operatietafels kunnen ergonomisch gezien niet laag genoeg ingesteld worden voor laparoscopie. Voornamelijk door het geringe aantal monitoren en hun verkeerde positie, stond het chirurgisch team over het algemeen in een oncomfortabele houding. De oplossingen en richtlijnen die in deze studie worden aangedragen, hebben betrekking op een correcte positionering van de monitoren volgens de ergonomische richtlijnen en optimalisatie van de positie van het chirurgisch team ten opzichte van de aanwezige monitoren.

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In de voorgaande hoofdstukken is een beeld gecreëerd van de ergonomische problemen waar het chirurgisch team dagelijks mee te maken heeft, evenals de mogelijkheden en inzichten om werkomstandigheden van het chirurgisch team te optimaliseren en zo de kwaliteit van de chirurgische ingreep te verbeteren. De fysieke klachten en het discomfort dat het chirurgisch team tijdens open en laparoscopische ingrepen ervaart heeft te maken met oncomfortabele houding, verkeerde werkhoogte, statische belasting en verhoogde spieractiviteit om het lichaam te balanceren. In hoofdstuk 4 wordt een productoplossing aangedragen en de evaluatie van deze oplossing besproken. De productoplossing die in deel 1 van hoofdstuk 4 wordt besproken is een lichaamsondersteunend product dat de chirurgen bij zowel open als bij laparoscopische ingrepen ondersteund in hun natuurlijke werkhouding. Het ontwerp wordt procesmatig beschreven aan de hand van de ontwerpcyclus. Een werkend prototype laat zien dat de productoplossing voldoet aan de eisen van compactheid, mobiliteit, instelbaarheid en geschiktheid voor chirurgen met verschillende lichaamsbouw. De eerste evaluatie vindt plaats met de chirurgen in de operatiekamer. In deel 2 van hoofdstuk 4 wordt dieper ingegaan op de biomechanica als onderliggende theorie voor de productoplossing. Een uitgebreid onderzoek wordt gedaan naar de reductie van spieractiviteit door het productgebruik. Hoofdstuk 5 richt zich op de sensorische en cognitieve aspecten van laparoscopische ingrepen en in het bijzonder op de beeldkwaliteit tijdens een laparoscopische ingreep. Deze studie bestaat uit een reeks objectieve en subjectieve metingen in zesendertig Nederlandse ziekenhuizen. De verzamelde data geeft aan dat de kwaliteit van de componenten van de beeldketen niet optimaal zijn en dat er in de meeste ziekenhuizen geen richtlijnen aanwezig zijn om deze componenten te testen. Er zijn grote verschillen in lichtintensiteit van de beeldketen tussen de verschillende ziekenhuizen en verschillende soorten operaties. Hoofdstuk 6 reflecteert op de problemen die in Hoofdstuk 2 zijn beschreven en draagt in de praktijk toepasbare ergonomische oplossingen aan. Dit hoofdstuk is in het bijzonder voor de chirurgen bedoeld die op een snelle manier de problemen willen aanpakken die optreden bij het uitoefenen van de operaties, door het toepassen van de besproken oplossingen. Hoofdstuk 7 is daarentegen bedoeld voor de ontwerpers en beschrijft de stappen van de doorlopen ontwerpcyclus aan de hand van een aantal casus. Deze casus zijn onderverdeeld in fysieke, sensorische en cognitieve ergonomie en hebben betrekking op de medische productontwikkeling.

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In hoofdstuk 8 worden eerst de verschillende methodologieën die zijn toegepast in dit proefschrift, besproken. Hierbij wordt onderscheidt gemaakt tussen “field research” en “experimental study” en worden de voordelen en nadelen van deze twee onderzoeksmethoden binnen de context van dit proefschrift besproken. De ontwerpcyclus van de casus die in hoofdstuk 7 zijn behandeld wordt gediscussieerd. Hierbij ligt de nadruk op (i) hoe de verschillende stappen van de ontwerpcyclus elkaar beïnvloeden, (ii) de rol van het gebruiksonderzoek binnenin de ontwerpcyclus en (iii) hoe de eerste twee het uitwerkingsniveau van het eindproduct bepalen. Er wordt gereflecteerd op welke bijdrage de verschillende onderzoeken hebben geleverd aan het verbeteren van de “surgical quality”. Tot slot worden paar interessante onderzoeksrichtingen uitgestippeld die nader bestudeerd kunnen worden.

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Swaitzberg, SD. (2001). Imaging Systems in Minimally Invasive surgery. Seminars in Laparoscopic Surgery, 8, 3-11. Tractinsky, N, Katz, AS, & Ikar, D. (2000). What is beautiful is usable. Interacting with computers, 13(2), 127-145. van Veelen, MA. (2003). Human-Product Interaction in Minimally Invasive Surgery: A Design Vision for Innovative Products. Delft University of Technology, Delft. Van Veelen, MA, Jakimowicz, JJ, Goossens, RHM, Meijer, DW, & Bussmann, JBJ. (2002a). Evaluation of the usability of two types of image display systems, during laparoscopy. Surgical Endoscopy, 16, 674-678. van Veelen, MA, Kazemier, G, Koopman, J, Goossens, RH, & Meijer, DW. (2002b). Assessment of the ergonomically optimal operating surface height for laparoscopic surgery. J Laparoendosc Adv Surg Tech A, 12(1), 47-52. van Veelen, MA, Meijer, DW, Uijttewaal, I, Goossens, RHM, Snijders, CJ, & Kazemier, G. (2003a). Improvement of the laparoscopic needle holder based on new ergonomic guidlines. Surgical Endoscopy, 17, 699-703. van Veelen, MA, Nederlof, EAL, Goossens, RHM, Schot, CJ, & Jakimowicz, JJ. (2003b). Ergonomic problems encountered by the medical team related to products used for minimally invasive surgery. Surgical Endoscopy, 17(7), 1077-1081. Van Veelen, MA, Snijders, CJ, Van Leeuwen, E, Goossens, RHM, & Kazemier, G. (2003c). Improvement of foot pedals used during surgery based on new ergonomic guidelines. Surgical Endoscopy, 17, 1086-1091. Verdaasdonk, EG, Stassen, LP, van der Elst, M, Karsten, TM, & Dankelman, J. (2007). Problems with technical equipment during laparoscopic surgery. An observational study. Surg Endosc, 21(2), 275-279. Vereczkei, A, Feussner, H, Negele, T, Fritzsche, F, Seitz, T, Bubb, H, et al. (2004). Ergonomic assessment of the static stress confronted by surgeons during laparoscopic cholecystectomy. Surgical Endoscopy, 18, 1118-1122. Wauben, LSGL, Van Veelen, MA, Gossot, D, & Goossens, RHM. (2006). Application of ergonomic guidelines during Minimally Invasive Surgery: A questionnaire amongst 284 surgeons. Surgical Endoscopy, 20(8), 1268–1274. Way, LW, Stewart, L, Gantert, W, Liu, K, Lee, CM, Whang, K, et al. (2003). Causes and prevention of laparoscopic bile duct injuries: analysis of 252 cases from a human factors and cognitive psychology perspective. Ann Surg, 237(4), 460-469. Wentink, M, Stassen, LPS, Alwayn, I, Hosman, RJAW, & Stassen, HG. (2003). Rasmussen’s model of human behavior in laparoscopy training. Surgical Endoscopy, 17, 1241-1246. Winter, DA. (1995). Human balance and posture control during standing and walking. Gait & Posture, 3(4), 193-214. www.dined.nl. (2004). DINED table. Retrieved 10-01-2006 www.nvec.nl. (2004). Endoscopische Landkaart Nederland. Retrieved 15-08-2006, 2006, from http://www.nvec.nl/ www.wsacs.org. Concensus definitions and recommendations. Retrieved March 15, 2006

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ACKNOWLEDGEMENT

It is an exceptional and a pleasant feeling to write my acknowledgement. It is exceptional because it is introducing the end of my PhD-research and at the same time, it is a milestone in my career. It is pleasant because I can finally thank all the people who were involved in my PhD-research. Without their contribution and support, I would not have been able to do my PhD-research and to write this thesis. First of all, I would like to thank my supervisors Huib de Ridder and Jaap Bonjer for their guidance and support during my PhD-research. Dear Huib, I have learned a lot from your scientific character, critical and valuable feedback. You have introduced me in the world of statistics and yes, I believe that a nice graph can tell more then just a thousand numbers. Dear Jaap, your critical and open-minded attitude regarding research in the medical field inspired me a lot. Nevertheless, I was the only engineer in your research group when started my PhD-research in Erasmus MC and from the first day, I had the feeling that I was a member of great medical family. My dear co-promoter Richard Goossens. You have played a multidimensional role during my PhD-research. You are an inspiring mentor when we discussing the research and writing an article. You are a valuable colleague when we are discussing about education and brainstorming about new challenging studies. You are a lovely friend who is always prepared to listen. Thanks for filling these revealing roles and for the confidence that you had in me. My dear mentor Chris Snijders. You were the first person who introduced me in the academic world. You took my hand and said, “you can do it, go Arma an”. I always have the feeling that I can count on you in difficult times. This has encouraged me to keep going. Thanks for being there and for your valuable support.

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My dear mentor Geert Kazemier. I want to thank you for initiating my PhD-research and for your support throughout the whole process. You were a mentor who was challenging me and stimulating me to look further than the obvious facts. My dear collegues from Erasmus MC. I had a great time with you when I was working at the “Z-gebouw”. You have included me in your group and taught me to speak your “language”. The congresses that we visited together were always a great experience! I will never forget you guys! I would like to thank the Erasmus Medical Centre for facilitating and financing the first two years of my PhD-research. The first year was financed by the Department of Surgery, by my supervisor Jaap Boner and the second year by the Department of Operating Room, by Geert Kazemier. I would also thank the employees of Erasmus Medical Centre for their contribution to my PhD-research. Dear Dirk Meijer. I would like to thank you for your contribution and support. I would thank the hospitals, who participated in the studies, for their contribution and hospitality. Their contribution was essential to collect the valuable data. I would like to acknowledge the companies for providing me the equipment and tools, which I have used during my studies. Dear Sacha Silvester and Linda Roos from DDI. When I was came back to the faculty in 2004, my first workplace was in DDI. DDI is a place where the openness, warmness, and multidisciplinary approach of Industrial Design meet each other. It is open because of the construction, it is warm because of the people who are working there and it is multidisciplinary because the harmony between the different specialisms. I had a wonderful time in DDI. Thanks for everything! Dear Linda. In the course of time, we got closer and now you are more a friend than a colleague for me. Our belly dance and aqua aerobics courses were a pleasant activity during our hectic PhD-research. Our conversations were sometimes emotional, sometimes funny and sometimes work related. We cried and laughed together but the most important for me was that you were always there to support me! Thanks! Dear Sonja. I can remember our first meeting in DDI before you start with your PhD. My first impression was, “what an enthusiastic and inquisitive person”. These

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characteristics made our talks never dull and we had many common issues to discuss. Thanks for your reliable friendship! My dear roommate Marijke. When I was employed for my new job, our ways have met in room 3B-11. In my first year as UD, you were always there to share your experience and gave me tips and tricks regarding the educational responsibilities. I have discovered that you have a strong intuition on personal and professional level, which provides me with different insights on different topics. You are the “cool mom” of Elissa and I am very glad to share a room with you. Thanks for everything! Dear Stella and Annelise. You have warmly welcomed me in your group and the door of your room was always open for me. You were always prepared to listen and think along with me. You have made the difficult times easier to pass. Thanks! Dear Martine van Veelen. I would like to thank you for your support and contribution to my PhD-research. With your thesis, you have created a valuable basis on which I built on. Dear Johan, Rick, Arnold, Marijke, Iemkje and Adinda. I would like to thank you for the nice talks that did brighten me up and provided me with new energy to go on. Dear Daan. I am very glad to be a member of your team Applied Ergonomics and Design. I am looking forward for to coming years because there are many opportunities to explore together. Dear Mirjam, Daphne, Amanda, and Monique. Our lovely secretaries of Department ID. I would like to thank you for your support and assistance throughout the whole project. The warmness and the smiles on your faces make you special! Dear PhD’s of the faculty. The different cultures and researches among the PhD’s in our faculty have enriched my perception in many ways. Thanks for the interesting discussions and for the nice social events, we had. It is always fun to be with you! My dear paranimfs, Elif and Mano. These two persons represented with their profession, the two worlds of my PhD-research. On the one hand a designer and on the other hand a medical specialist. These two persons are also representing a unique friendship. Elif you are my “kader arkada m”. We have many familiarities like our roots, which are in Turkey, but also like our future, which is here in Holland, in the faculty of Industrial Design Engineering, where we are so proud of. You are a lovely friend. Mano thanks for providing me with knowledge about the medical world and, thanks for being my friend and my paranimf.

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A special thanks in Turkish for my lovely parents. “Canm annem ve babam. Sizin bana olan büyük deste iniz ve ba araca ma olan inanciniz benim bu günlere gelmemi sa lad. Sizin kznz oldu um için gurur duyuyorum. Her ey için te ekkürler!” Dear Metin, Rina, Yasmin, Kirsten and my parents in law. It is great to have you on my site. The difficult times would not have passed easily without your encouragements and warm support. Thanks for everything! My dear husband René. As none other person, you experienced the more unpleasant side effects of being married with someone who was finishing her PhD. Regardless of my moods, changing from emotional, stressful, bad-tempered, etc., you always succeed in relaxing me and gave me the comfortable feeling again. You were always standing behind me, which makes me confident in what I was doing. A km, thanks for being there today and in the future!

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CURRICULUM VITEA

Arma an Albayrak was born in Ankara, Turkey on December 16th 1975. In 1993, she finished her high school education in Izmir, Turkey. The same year she came to Holland and did her entrance examination for a study on Delft University of Technology. In 1994, she started with her study Industrial Design Engineering at the Delft University of Technology. In 2002, she received her master degree at this faculty. The same year she started with her PhD-research titled “Ergonomics in the operating room: transition from open to image-based surgery”. Her PhD-research was in cooperation with the Erasmus Medical Centre (EMC) in Rotterdam. In the first two years of her PhD-research she was situated in EMC. In 2004, she came back to the faculty Industrial Design to finish her PhD. Since July 2007, she has been employed as an Assistant Professor at the department Industrial Design, section Applied Ergonomics and Design. Her responsibilities include both research and teaching in the field of ergonomics, medisign, usage evaluation methodology and biomechanics.

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OVERVIEW PAPERS

Albayrak A, Wauben LSGL, and Goossens RHM. Ergonomics in the Operating Room – Design framework. (2008). Accepted as book chapter on Ergonomics: Design, Integration and Implementation by Nova Science Publishers, Inc. Albayrak A, Goossens RHM, Snijders CJ, de Ridder H, Kazemier G. Impact of a chest support on lower back muscles activity during forward bending. Submitted (2008). Albayrak A, Casseres YA, de Ridder H, Goossens RHM, Kazemier G, Meijer DW, Bonjer HJ. Objective and subjective evaluation of image quality during minimally invasive surgery. Submitted (2008). Wauben LSGL, Albayrak A, and Goossens RHM. Ergonomics in the Operating Room – An overview. (2008). Accepted as book chapter on Ergonomics: Design, Integration and Implementation by Nova Science Publishers, Inc. Wauben LSGL, Albayrak A, de Ridder H, Jakimowicz J. LED versus Xenion surgical lights: Product evaluation during surgery. (2008). International Conference Healthcare Systems Ergonomics and Patient Safety June 25/28, 2008. Albayrak A, and Snijders CJ. (2007). Ergonomy in the OR. In JB Trimbos & GCM Trimbos Kemper (Eds.), Basics of surgery: Tools, techniques and expertise (pp. 151-169). Maarssen: Elsevier gezondheidszorg. Albayrak A, van Veelen MA, Prins JF, Snijders CJ, de Ridder H, and Kazemier G. (2007). A newly designed ergonomic body support for surgeons. Surgical endoscopy and other interventional techniques, 21(10), 1835-1840.

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Albayrak A, van Veelen MA, Prins JF, Snijders CJ, de Ridder H., Kazemier G. (2006). Rugbelasting bij chirurgen tijdens operaties: Het effect van lichaamsondersteuning. Tijdschrift voor Ergonomie 31 (1): 10-19. Albayrak A, van Veelen MA, Prins JF, Snijders CJ, de Ridder H., Kazemier G. (2006). Reducing muscle activity of the surgeon during surgical procedures. In Proceedings of the 16th World Congress on Ergonomics, Maastricht, The Netherlands: International Ergonomics Association. Albayrak A, Goossens RHM, Bonjer HJ, Casseres YA, Kazemier G, de Ridder H. (2006). Image quality during laparoscopic procedures in practice. In Proceedings of the 16th World Congress on Ergonomics, Maastricht, The Netherlands: International Ergonomics Association. Albayrak A, Kazemier G, Meijer DW and Bonjer HJ. (2004). Current state of ergonomics of operating rooms of Dutch hospitals in the endoscopic era. Minimally invasive therapy & allied technologies, 13(3), 156-160. (TUD) Gerbrands A, Albayrak A, and Kazemier G. (2004). Ergonomic evaluation of the work area of the scrub nurse. Minimally invasive therapy & allied technologies, 13(3), 142-146. (TUD) Casseres YA, Albayrak A, Schot C, Grimbergen CA, Bonjer HJ, and Meijer DW. (2003). Kwaliteit van endoscopische apparatuur en instrumentarium: een voorlopige rapportage. Nederlands Tijdschrift voor Heelkunde, 12(5), 171-174.

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G L O SSAR Y

Abduction Adduction

Biomechanics Cognitive ergonomics

Comfort Dependent variable Ecological validity

Efficiency

A movement of a body segment in a lateral plane away from the midline of the body, such as raising the arm sideways. A movement of the body segment toward the midline as when moving the arm from the outward horizontal position downward to the vertical position. Assumptions Basic tenets that form the bases for more complex scientific theory and research. Application of mechanical principles on living organisms. The emphasis lies on remembering and processing information; on learning, decision making and judging a situation. It is strongly based on knowledge of the psychology of thinking and remembering. The products that support this part of ergonomics can be schemes of structures, mnemonic devices, software to control a process and training devices. A physical and mental state in which one is not aware. A variable assumed to depend on or be caused by another (called the independent variable). Experiments achieve ecological validity when they reproduce accurately the real-life situations, thus allowing easy generalization of their findings to the real world. External validity and ecological validity are closely related but they are independent. Efficiency is defined as the coefficient between effort and benefit. In this definition, effort also implies e.g. product life span and learning and understanding the use of the product (e.g. it can take several months to learn how to perform a task without errors).

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Ergonomics (human-factors)

Experimental study/research

Extension

External validity

Flexion Force grip Force-precision grip Independent variable

Laparoscopy Minimally invasive surgery Participatory design Physical ergonomics

Precision grip Product solution Pronation

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Human factors discovers and applies information about human behaviours, abilities, limitations, and other characteristics to the design of tools, machines, systems, tasks, jobs, and environments for productive, safe, comfortable, and effective human use. Set of procedures that defines a research study at the experimental level of constrain. In experimental research, participants are assigned to groups or conditions without bias, and all appropriate control procedures are used. A movement in the opposite direction of flexion which causes an increase in the angle at the joint, such as straightening the elbow. Refers to the possibility that conclusions drawn from experimental results may not be generalizable to the real world. A movement of a segment of the body causing a decrease in the angle at the joint, such as bending the arm at the elbow. Grip with fingers and thumb around an object. Force grip that allows more precision: fingers are around and object and the thumb is in-line with the forearm. A variable with values that are not problematical in an analysis but are taken as simply given. An independent variable is presumed to cause or determine a dependent variable. A minimally invasive procedure within the abdomen. Surgery performed through small skin cuts or through the natural openings in the human body. Design method that involves the user group in different phases of the design process. Emphasis lies on the function of the human musculo-skeletal system, which is used to adopt postures, move limbs, and conduct external forces through the body. On the product site, this covers products that support the body, tools, and special outfits. Grip that uses the thumb and distal joints of the fingers to grasp an object. A material solution to accomplish a task. Rotation of the hand and forearm that results in a palm-down position.

GLOSSARY

Reliability

Rotation Safety Sensorial ergonomics

Supination Surgical quality

That quality of measurement method that suggests that the same data would have been collected each time in repeated observations of the same phenomenon. A movement of a segment around its own longitudinal axis. Deals with the wellbeing of the user (in the case of MIS also the wellbeing of the patient) and the prevention of injury. In this area, the focus is on the human senses and human perception. On the product site, this includes products that support the senses and perception, such as visual displays, but also tactile displays and auditory displays. Rotation of the hand and forearm that results in a palm-up position. The level of efficiency, safety, and comfort of a surgical procedure.

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