Anesthesia Unit Vaporizers (translate).docx

Procedure/Checklist 436-0595

Anesthesia Unit Vaporizers Used For: Anesthesia Unit Vaporizers [10-144]

Also Called: By trade names (e.g., Fluotec 5, Vapor 19.1, Tec 6), which are registered trademarks and should be used only when referring to the specific devices Commonly Used In: Operating rooms, emergency rooms, delivery rooms, trauma rooms, and any areas requiring the administration of an inhalation agent (with anesthesia units) Scope: Applies to the various anesthesia vaporizers used to deliver a known concentration of vaporized liquid anesthetic Risk Level: ECRI Recommended, High; Hospital Assessment, Type

ECRI-Recommended Interval*

Interval Used By Hospital

Major

6 months

months

.

hours

Minor

NA

months

.

hours

Time Required

* Additional periodic calibration and preventive maintenance is normally required annually or biannually (see manufacturer’s recommendation). Only qualified personnel trained and experienced in this function should perform this additional servicing.

Overview An anesthesia unit vaporizer is used to vaporize a liquid anesthetic agent and deliver a controlled amount to the patient. According to the American Society for Testing and Materials (ASTM) standard ASTM F1161-88, anesthetic agent vaporizers are required to be concentration calibrated (i.e., a calibrated knob controls the output concentration). Older vaporizers, such as the Copper Kettle and the Vernitrol, do not have a single control for selecting the concentration of anesthetic vapor. Where possible, these units should be removed from service. Contemporary concentration-calibrated vaporizers are of two types: variable bypass and heated blender. Conventional (variable-bypass) vaporizers. In a variable-bypass vaporizer, the total background gas flow that enters the unit is split into two streams. The

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smaller stream, which acts as the carrier gas, passes through the vaporizing chamber containing the anesthetic agent and becomes saturated with agent vapor; the remainder of the gas bypasses this chamber. A wick may be used in the vaporizing chamber to provide increased surface area for efficient evaporation of the drug and saturation of the carrier gas. The saturated carrier gas leaves the chamber and mixes with the bypass gas. One adjustment is made to set the desired concentration. This adjustment simultaneously balances the carrier and bypass flows to produce the blend required for the set concentration. The mixture exits the vaporizer and is delivered from the anesthesia machine as the fresh gas to be inspired by the patient. Evaporation of the liquid agent contained in the chamber is driven by heat absorbed from the walls of the vaporizer; consequently, when evaporation is occurring, the vaporizer and its contents cool. Because the equilibrium vapor pressure of an agent changes

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Inspection and Preventive Maintenance System pass vaporizer. As a result, the variable-bypass design was abandoned for desflurane, and Ohmeda developed a new vaporizer, the Tec 6, based on a heated-blender design. Figure 2 shows a schematic of this vaporizer.

Figure 1. Schematic illustrating the basic elements of a vaiable-bypass vaporizer with temperature, a temperature-sensitive mechanism is used to automatically adjust the carrier and bypass flows to compensate for temperature changes. Figure 1 presents a schematic of a variable-bypass vaporizer. Desflurane (heated-blender) vaporizers. Desflurane, a volatile inhalation anesthetic marketed by Ohmeda Pharmaceutical Products Division under the trade name Suprane, has characteristics that differ markedly from those currently in use — enflurane, halothane, and isoflurane; for example, its low solubility allows rapid induction of and emergence from anesthesia. Thus, by increasing the speed of recovery, desflurane has the potential to shorten hospital stays (although this has not yet been consistently demonstrated). The boiling point of desflurane — 22.9°C at 760 mm Hg — is just above room temperature; therefore, small increases in ambient temperature or decreases in atmospheric pressure can cause it to boil. Also, because of desflurane’s high minimum alveolar concentration, or MAC (i.e., its low potency), evaporation of sufficient agent to achieve a given anesthetic effect would require much more heat absorption from the vaporizer than occurs with other agents. Furthermore, the change in vapor pressure of desflurane per change in temperature is as much as three times that for the other volatile agents at sea-level atmospheric pressure. These profound effects of temperature and ambient pressure on the vapor pressure of desflurane make stabilizing the delivered concentration at a set point extremely difficult in a passive mechanical system, such as a variable-by-

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A version of the Tec 6 (also manufactured by Ohmeda) has been adapted for Drager machines and is compatible with the Drager triple-exclusion interlock system. As of this writing, neither Drager nor Siemens has developed its own desflurane vaporizer. A desflurane vaporizer requires electrical power to heat the agent to a thermostatically controlled 39°C, producing a stable, saturated vapor pressure of 1,500 mm Hg. No wick is used, and no carrier gas enters the sump chamber. Instead, a stream of vapor under pressure flows out of the sump; this stream blends with the background gas stream, which originates from the anesthesia machine’s flowmeters, to achieve the desired concentration. The background gas stream passes through a fixedflow resistor, producing a back pressure upstream of this resistor that is proportional to the background gas flow. The desired desflurane concentration is set on the dial of the adjustable metering valve in the vapor stream; this setting produces a predetermined aperture. The pressure in the vapor upstream of the aperture and the back pressure in the background gas stream are continually sensed by a differential pressure transducer. The transducer controls a pressureregulating valve in the vapor stream between the sump

Figure 2. Schematic illustrating the basic elements of the Ohmeda Tec 6 vaporizer

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Anesthesia Unit Vaporizers and the adjustable metering valve. The pressure-regulating valve permits only that flow from the sump necessary to cause the pressure upstream of the adjustable metering valve to equal the back pressure in the background gas stream. In this way, the ratio of the adjustable metering valve’s resistance to the resistance of the fixed-flow resistor determines the ratio of the flows in each stream, and therefore, the concentration of vapor in the blended output. If the flow from the anesthesia machine’s flowmeters through the vaporizer is altered, the flow of vapor from the sump is automatically adjusted so that the pressures at the two monitored points remain equal, the flow ratio does not change, and the output concentration continues to match its setting. The control circuits and heating elements in the vaporizer are turned on by the act of connecting the vaporizer to electrical power. The unit then heats to and remains at operating temperature as long as it receives power, whether it is delivering agent or is in the standby mode. Consequently, it is warm to the touch while plugged into a live socket.

Citations from Health Devices Avoiding anesthesia mishaps through pre-use checks, 1982 May; 11:210-3. Water in halothane vaporizers [Hazard], 1985 Aug; 14:326. Anesthesia units with a flowmeter-controlled vaporizer [Hazard], 1986 Dec; 15:336.

Do not fill a vaporizer with an inhalation agent unless you are qualified to do so. Always use a scavenging system or appropriate ventilation when inspecting vaporizers. For personal safety, when inspecting vaporizers alone, notify other personnel of your location. Be sure that filler ports are tightly capped before passing gas through the vaporizer.

Procedure Before beginning an inspection, carefully read this procedure and the manufacturer’s instruction and service manuals; be sure that you understand how to operate the equipment and the significance of each control and indicator. Also determine whether any special inspection or preventive maintenance procedures or frequencies are recommended by the manufacturer. Note: This procedure should be done simultaneously with Anesthesia Units Procedure/Checklist 400, where leak testing of the vaporizer has been included with the anesthesia unit. Each vaporizer should have a separate control number. Inspection documentation for up to three vaporizers (on one anesthesia unit) can be included on one inspection form (record each control number), but some hospitals may prefer to use a separate form for each vaporizer. Be sure that the anesthesia system is level and secure. Check that all hoses and fittings are tight.

1. Qualitative tests 1.1

Pre-use anesthesia check fails to find faults [Hazard], 1988 Sep; 17:274-6.

Chassis/Housing. Examine the exterior of the unit for cleanliness and general physical condition. Be sure that housings are intact, that all assembly hardware is present and tight, and that there are no signs of spilled liquids or other serious abuse.

1.2

Desflurane (Suprane): Considerations for introduc- ing the new inhalation anesthetic agent into clinical practice [Guidance article], 1994 Apr; 23:131-42.

Mount/Fasteners. Check security of mounts or support mechanisms. Verify that the vaporizer is firmly mounted on the anesthesia unit.

1.4

AC Plug. If the unit is so equipped, examine the AC power plug for damage. Attempt to wiggle the blades to determine that they are secure. Shake the plug and listen for rattles that could indicate loose screws. If any damage is suspected, open the plug and inspect it.

1.5

Line Cord. Inspect the cord, if so equipped, for signs of damage. If damaged, replace the entire cord, or if the damage is near one end, cut out the defective portion. Be sure to wire a new power cord or plug with the same polarity as the old one.

Vaporizer leak with Mapleson breathing circuits [Hazard], 1986 Dec; 15:344-5. Concentration calibrated vaporizers [Hazard], 1987 Mar-Apr; 16:112-3.

Test apparatus and supplies Halogenated anesthetics analyzer Hoses and adapters

Special precautions As a general precaution, a vaporizer containing an anesthetic agent should not be tipped. If such tipping occurs, notify the user and follow the manufacturer’s recommended procedures for airing or drying the unit.

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Inspection and Preventive Maintenance System 1.6

Strain Reliefs. Examine the strain reliefs at both ends of the line cord, if so equipped. Be sure that they hold the cord securely.

1.7

Circuit Breaker/Fuse. If the device has a switch-type circuit breaker, check that it moves freely. If the device is protected by an external fuse, check its value and type against that marked on the chassis, and ensure that a spare fuse is provided.

1.8

Tubes/Hoses. Check the condition of all tubing and hoses. Be sure that they are not cracked, kinked, or dirty.

1.10

Fittings/Connectors. Examine all gas and liquid fittings and connectors for general condition. Be sure all fittings are tight.

1.13

Controls. Before moving any controls, check their positions. If any of them appear inordinate or are left in the on position, consider the possibility of inappropriate clinical use or of incipient device failure. Examine all controls for physical condition, secure mounting, and correct motion. Where a control should operate against fixed-limit stops, check for proper alignment, as well as positive stopping. During the course of the inspection, be sure to check that each control performs its proper function. Return all controls to the off position following the test.

1.16 Fluid Levels. Check all fluid levels. If the fluid level is zero, we recommend that you have a qualified user fill the sump with anesthetic agent to continue the inspection. 1.17

1.18

1.20

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Battery. Inspect the physical condition of the battery and battery connectors, if so equipped and readily accessible. Operate the battery-powered functions of the unit for several minutes to check that the battery has an adequate charge. Check remaining battery capacity by activating the battery test function or measuring the output voltage. If it is necessary to replace a battery, label it with the date. Indicators/Displays. During the course of the inspection, confirm the operation of all indicators and visual displays on the unit, if so equipped. Alarms/Interlocks. Operate the device in such a way as to activate each audible and visual alarm, if so equipped. If the device has an alarmsilence feature, check the method of reset (i.e.,

manual or automatic) against the manufacturer’s specifications. Check that the vaporizer interlock allows activation of only one vaporizer at a time. 1.21

Audible Signals. Operate the device in such a way as to activate any audible signals. Confirm appropriate volume, as well as the operation of a volume control, if so equipped.

1.22

Labeling. Check that all necessary placards, labels, conversion charts, and instruction cards are present and legible.

1.24

Site Glass, O-Rings, Keyed Filler Mechanism. Examine the physical condition of the site glass, O-rings, and keyed filler mechanism, if so equipped.

2. Quantitative tests 2.1

Grounding Resistance. If the unit is electrically powered, use an ohmmeter, electrical safety analyzer, or multimeter with good resolution of fractional ohms to m e as u r e and record the resistance between the grounding pin of the power cord and exposed (unpainted and not anodized) metal of the chassis. We recommend a maximum of 0.5 

2.2

Leakage Current. For electrically powered units, measure chassis leakage current to the chassis of the device with the grounding conductor of plug-connected equipment temporarily opened. Operate the device in all normal modes, including On, Standby, and Off, and record the maximum leakage current. Leakage current should not exceed 300 A.

2.10 Concentration Check. Data for up to three vaporizers can be recorded as Items 2.10, 2.11, and 2.12. Record the type and control number of the vaporizer being tested under each item. 2.11 See Item 2.10 2.12 See Item 2.10 Because there are various types of halogenated anesthetic analyzers, follow the manufacturer’s procedure for setup and use of the analyzer. Vaporizers should usually be tested with an oxygen flow of 4 to 5 L/min (nitrous oxide may affect the readings of some vapor analyzers). Test the vaporizers at low, medium, and high concentration settings in the normal clinical use range (e.g., 0.5%, 1.0%, and 3.0% for halothane).

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Anesthesia Unit Vaporizers At one concentration setting (e.g., 1.0% for halothane, 10% for desflurane), test the vaporizer at another flow (e.g., 1 L/min). We recommend that the concentration be 0.3% vapor or 10% of the measured value, whichever is greater. If errors in concentration are observed, allow the vaporizer to operate for a minute or two and recheck the unit. Some units may require a short stabilization period.

3. Preventive maintenance 3.1

Clean the exterior.

3.2

Replace the battery, if so equipped (battery should be replaced at least once annually).

4. Acceptance tests Conduct major inspection tests for incoming vaporizers and, if a vaporizer is position sensitive, any time it is demounted from an anesthesia unit.

Before returning to use Return all controls to the off position, level and secure the unit, and tighten all fittings and tubing.

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Procedure Checklist 461-0595

Anesthesia Unit Ventilators Used For: Anesthesia Unit Ventilators [10-145]

Commonly Used In: Delivery rooms and operating rooms Scope: Applies to ventilators used to deliver inhalation anesthetic agents during surgical procedures that require general anesthesia Risk Level: ECRI Recommended, High; Hospital Assessment, Type

ECRI-Recommended Interval

Interval Used By Hospital

Major

6 months*

months

.

hours

Minor

NA

months

.

hours

Time Required

* Inspection and preventive maintenance intervals should be scheduled according to the manufacturer’s recommendations. However, units should have a major inspection at least every six months. Pre-use checks should be performed before each case by the anesthetist who will be operating the equipment.

Overview Patients undergoing surgery under general anesthesia are routinely paralyzed with muscle relaxants to stabilize the surgical field. Consequently, they are unable to breathe on their own and must be mechanically ventilated either manually by the anesthetist, who squeezes a reservoir bag in the breathing circuit, or automatically by an anesthesia ventilator. A switch valve allows the choice of the method by which ventilation is to be supported. The anesthesia ventilator is typically turned on and off independently of the switching between manual and automatic ventilation. Anesthesia ventilators use positive pressure to inflate a patient’s lungs and deliver a prescribed mixture of gases and vapors to them. This mixture is produced by the anesthesia machine. The ventilator can be built into the anesthesia machine or can be a stand-alone unit connected to the machine by gas tubing and, perhaps, sensor cables. Some anesthesia ventilators have built-in displays and alarms; others rely on the sensors, displays, and alarms of the anesthesia machine to monitor their performance.

In general, an anesthesia ventilator is less sophisticated than a critical care ventilator, having only a control mode of operation, with time cycling. (However, there is at least one ICU-type ventilator that can be used to administer inhalation anesthetics.) A pressure limit prevents exposure of the lungs to excessive pressure. Several other breathing waveshape parameters (e.g., inspiratory:expiratory [I:E] ratio, tidal volume, minute volume, flow) are settable by the operator and controlled by the ventilator. Ventilators designed solely for anesthetic administration typically do not have compressors. During extended procedures and procedures involving open breathing circuit configurations, a humidifier may be included in the breathing circuit. Otherwise, a circle system with an absorber, along with one-way inspiratory and expiratory valves, is used, typically without a humidifier. The ventilator’s pressure-relief and limit valve(s) should be connected to a waste gas scavenging system.

Citations from Health Devices Anesthesia systems [Evaluation], 1988 Jan; 17:3.

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Inspection and Preventive Maintenance System Who should service anesthesia equipment [User Experience NetworkTM], 1988 Feb; 17:70.

use by outside vendors can be produced to ensure that those items agreed upon are performed by the vendor.

Barotrauma from anesthesia ventilators [Hazard], 1988 Nov; 17:354.

The following framework should be supplemented by the manufacturer’s recommended preventive maintenance procedures for mechanical ventilators.

Damage to elastic components from Loctite [Hazard], 1989 Jul-Aug; 18:288. Risk of barotrauma and/or lack of ventilation with ventilatorless anesthesia machines [Hazard], 1994 Jan-Feb; 23:54.

1. Qualitative tests 1.1

Chassis/Housing. Examine the exterior of the unit for cleanliness and general physical condition. Be sure that plastic housings are intact, that all hardware is present and tight, and that there are no signs of spilled liquids or other serious abuse.

1.2

Mount/Fasteners. Check that ve ntil ators mounted in anesthesia machines are properly installed. If the device is mounted on a stand or cart, examine the condition of the mount. If it is attached to a wall or rests on a shelf, check the security of this attachment. Check the mounting security of all components.

1.3

Casters/Brakes. If the device moves on casters, check their condition. Verify that they turn and swivel, as appropriate, and look for accumulations of lint and thread around the casters. Check the operation of brakes and swivel locks, if the unit is so equipped.

1.4

AC Plug. Examine the AC power plug for damage, if so equipped. Attempt to wiggle the blades to check that they are secure. Shake the plug and listen for rattles that could indicate loose screws. If any damage is suspected, open the plug and inspect it.

1.5

Line Cord. Inspect the cord for signs of damage, if so equipped. If damaged, replace the entire cord or, if the damage is near one end, cut out the defective portion. Be sure to wire a new power cord or plug with the correct polarity. Also check line cords of battery chargers.

1.6

Strain Reliefs. Examine the strain reliefs at both ends of the line cord, if so equipped. Be sure that they hold the cord securely.

1.7

Circuit Breaker/Fuse. If the device has a switchtype circuit breaker, check that it moves freely. If the device is protected by an external fuse, check its value and type against that marked on the chassis, and ensure that a spare is provided.

1.8

Tubes/Hoses. Check the condition of all tubing and hoses. Be sure that they are not cracked, kinked, or dirty. Check that they are connected to the correct locations.

Test apparatus and supplies Lung simulator with adjustable compliance or ventilator tester Pressure gauge or meter with 2 cm H2O resolution from -20 to +120 cm H2O Various breathing circuit adapters Leakage current meter or electrical safety analyzer Ground resistance ohmmeter Additional items as required for specific manufacturers’ procedures

Procedure Before beginning an inspection, carefully read this procedure and the manufacturer’s instruction and service manuals; be sure that you understand how to operate the equipment, the significance of each control and indicator, and the alarm capabilities. Also determine whether any special inspection or preventive maintenance procedures or frequencies are recommended by the manufacturer. Manufacturers’ recommended procedures for inspection and preventive maintenance of mechanical anesthesia ventilators vary in both methods and required accuracy. In addition, ventilator controls can vary greatly among manufacturers and models. This procedure provides the basic framework for complete ventilator inspection and preventive maintenance. Manufacturers’ recommended procedures should be added where appropriate. References to specific pages of the manufacturer’s manual should be added to the checklist. (The checklist includes blank spaces for the insertion of these reference numbers.) IPM Task ManagerTM, the software component of the Inspection and Preventive Maintenance System, enables easy production of customized procedures and checklists for specific ventilator models and clinical needs. Items performed by outside vendors can be excluded from the checklist; a separate checklist for

2

Inspection and Preventive Maintenance System ©1995 ECRI. All Rights Reserved.

Anesthesia Unit Ventilators 1.9

Cables. Inspect any cables (e.g., for sensors) and their strain reliefs for general condition. Carefully examine cables to detect breaks in the insulation and to ensure that they are securely gripped in the connectors at each end, which will prevent rotation or other strain. Where appropriate, verify that there are no intermittent faults by flexing cables near each end and looking for erratic operation or by using an ohmmeter.

1.10

Fittings/Connectors. Examine all gas fittings and connectors for general condition. Gas fittings should be tight and should not leak. Verify that keyed connectors (e.g., pin-indexed gas connectors) are used where appropriate, that all pins are in place and secure, and that keying is correct. Connectors to hospital central piped medical gas systems should have the appropriate DISS or quick-connect fitting to eliminate the need for adapters.

1.12

1.13

Filters. Check the condition of gas filters, if included in the unit. Check for corrosion residue indicative of liquid, gaseous, or solid particle contaminants in the gas supply; if found, notify appropriate personnel. Clean or replace if appropriate, and indicate this on Lines 3.1 and 3.4 of the inspection form.

1.17

Battery/Charger. Inspect the physical condition of batteries and battery connectors, if so equipped and if readily accessible. Check operation of battery-operated power-loss alarms, if so equipped. Operate the unit on battery power for several minutes to check that the battery is charged and can hold a charge. (The inspection can be carried out on battery power to help confirm adequate battery capacity.) Check battery condition by activating the battery test function or measuring the output voltage; for lead-acid batteries, measure the specific gravity and check the fluid level. Check the condition of the battery charger and, to the extent possible, confirm that it does, in fact, charge the battery. Be sure that the battery is recharged or charging when the inspection is complete. When it is necessary to replace a battery, label it with the date.

1.18

Indicators/Displays. During the course of the inspection, confirm the operation of all lights, indicators, meters, gauges, and visual displays on the unit and charger (if so equipped). Be sure that all segments of a digital display function. Record the reading of an hour meter, if present.

1.20

Alarms/Interlocks. Induce alarm conditions to activate audible and visual alarms. Check that any associated interlocks function. If the unit has an alarm-silence feature, check the method of reset (i.e., manual, automatic) against the manufacturer’s specifications. It may not be possible to check out all alarms at this time since some may require special conditions that must be established according to the manufacturer’s recommendations; include these in Item 2.4. Verify that any remote alarm indicator (e.g., within the mainframe anesthesia unit) functions properly.

1.22

Labeling. Check that all necessary placards, labels, and instruction cards are present and legible.

1.23

Accessories. Confirm the presence and condition of accessories. Check the condition of reusable Bain circuit and adapters, if available.

1.24

Bellows. Check the physical condition and proper operation of the bellows.

Controls/Switches. Before changing any controls or alarm limits, check their positions. If any settings appear inordinate (e.g., alarm limits at the ends of their range), consider the possibility of inappropriate clinical use or of incipient device failure. Record the settings of those controls that should be returned to their original positions following the inspection. Examine all controls and switches for physical condition, secure mounting, and correct motion. Check that control knobs have not slipped on their shafts. Where a control should operate against fixed-limit stops, check for proper alignment, as well as positive stopping. Check membrane s witche s for dam age (e.g., from fingernails, pens). During the inspection, be sure to check that each control and switch performs its proper function.

2. Quantitative tests 2.1

1.15

Fan. Check physical condition and proper operation, if so equipped. Clean and lubricate if required, according to the manufacturer’s instructions, and note this on Lines 3.1 and 3.2 of the form.

Grounding Resistance. Using an ohmmeter, electrical safety analyzer, or multimeter with good resolution of fractional ohms, measure and record the resistance between the grounding pin of the power cord and exposed (unpainted and not anodized) metal on the chassis of the ventilator or of

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3

Inspection and Preventive Maintenance System the system in which the ventilator is mounted. We recommend a maximum of 0.5 . If the ventilator is a component within an anesthesia unit, grounding and leakage current measurements can be referenced to that unit. 2.2

Leakage Current. Measure chassis leakage current to ground with the grounding conductor of plug-connected equipment temporarily opened. Operate the device in all normal modes, including on, standby, and off, and record the maximum leakage current.

Volume (e.g., tidal volume, minute volume, apnea) Fraction of inspired oxygen (FIO2; see Oxygen Analyzers Procedure/Checklist 417) Alarm settings (e.g., high PIP, low MAP, low pressure, low FIO2) should be inspected for proper and accurate activation. 2.5

Pneumatic lines (including air filters). Verify that appropriate gas-specific connectors are used. Check gas filters, if so equipped and accessible.

Measure chassis leakage current with all accessories normally powered from the same line cord connected and turned on and off. This includes other equipment that is plugged into the primary device’s accessory receptacles, as well as equipment plugged into a multiple-outlet strip (“Waber strip”) so that all are grounded through a single line or extension cord.

Gas cylinders (and gauges and regulators, if so equipped). Verify that these are present, securely mounted, and in good condition and that there is an adequate gas supply. Verify that one and only one washer is used to seal the tank to its yoke. Verify that all index pins are present and protruding to the proper length to engage the hole in the tank valve stem and in the correct positions for the gas to be supplied through the yoke.

Chassis leakage current to ground should not exceed 300 A. 2.3

2.4

Modes and Settings. Anesthesia ventilators are usually equipped only with a control mode. However, specialized units may have additional modes such as assist/control and pressure support. Adjustable positive end-expiratory pressure (PEEP) may also be available. The function of these modes should be inspected and verified for proper operation. Check the operation and accuracy of ventilation controls, which may include tidal volume, breath rate, inspiratory time, expiratory time, I:E ratio, pressure limit, or flow. Typically, these tests are performed by attaching the ventilator to a lung simulator or ventilator tester and comparing measured values to settings on the ventilator. The manufacturer should recommend the appropriate ventilator settings (e.g., tidal volume, rate, inspiratory time) to verify proper operation and accuracy (generally within 10%). Monitors and Alarms. The following breathing circuit parameters may be monitored by the ventilator or by the system in which the ventilator is mounted. They should be inspected for accuracy (generally within 10%) according to the manufacturer’s specifications:

2.6

Patient Circuit. Breathing circuit (including filters). Verify that these components are compatible with the ventilator according to the manufacturer’s recommendations (see Health Devices 1988 Apr; 17:109). Check for leaks, the absence of obstructions, and proper flow direction in the breathing circuit, ensuring the proper assembly and function of fittings, adapters, the CO2 absorber, inspiratory and expiratory valves and PEEP valves, the APL valve, the scavenger, and other components. With the ventilator connected to the anesthesia system, check for leaks in the entire system, including the breathing circuit. This does not have to be duplicated if done as part of the Anesthesia Units procedure (see Procedure/Checklist 400). Humidifiers. See Heated Humidifiers Procedure/Checklist 431.

Inspiratory time

Pressure-Relief Mechanism. Check the proper operation of the pressure-relief mechanism by occluding the breathing circuit and measuring the resulting peak pressure on the pressure gauge. Verify that pressure is vented in the breathing circuit.

Airway pressure (e.g., PIP, PEEP, MAP, apnea)

Absorber. See Anesth esi a dure/Checklist 400.

Breathing rate

4

Gas Supply.

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Units

Proce-

Anesthesia Unit Ventilators 3. Preventive maintenance 3.1

Clean the exterior and interior, if needed.

3.3

Calibrate according to manufacturer’s instructions.

3.4

Replace components according to the manufac- turer’s instructions.

4. Acceptance tests Conduct major inspection tests for this procedure and the appropriate tests in the General Devices Pro- cedure/Checklist 438.

Before returning to use Ensure that all controls are set properly. Set alarms loud enough to alert personnel in the area in which the device will be used. Other controls should be in their normal pre-use positions. Attach a Caution tag in a prominent position so that the user will be aware that control settings may have been changed. Recharge battery-powered devices, or equip them with fresh batteries, if needed.