Physiology 7th Lecture - Respiratory Physiology Ventilation
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View Physiology 7th Lecture - Respiratory Physiology Ventilation as PDF for free.
More details
- Words: 1,014
- Pages: 8
Respiratory Physiology Ventilation Major functions of respiratory system •
To supply the body with oxygen and dispose of CO2
•
Respiration – four distinct processes must happen: •
Pulmonary ventilation – moving air into and out of the lungs
•
External respiration – gas exchange between the lungs and blood
•
Transport – transport of oxygen and carbon dioxide between the lungs and tissues
•
Internal respiration – gas exchange between systemic blood vessels and tissues
Breathing •
Breathing, or pulmonary ventilation, consists of two phases: •
Inspiration – air flows into the lungs
•
Expiration
Eupnea •
Normal spontaneous breathing of which we are normally unaware
•
Ventilation is matched to metabolic demands
Hyperpnea •
Increased ventilation which matches increased metabolic demands such as exercise
•
Initially, increased ventilation is mainly increased tidal volume
•
Increased frequently is proportionately more important at higher intensities
Hyperventilation •
Inappropriately high ventilation for the metabolic demands
•
Hallmark. Alveolar and arterial are PCO2 decreased
•
Alveolar PO2 is increased
Tachypnea Increased frequency of breathing Ventilation may or may not be changed depending on what happens to tidal volume
Dyspnea Subjective sensation of difficulty to breath. Shortness of breath.
Apnea Temporary absence of cessation of breathing (usually at FRC) Implication that breathing will resume spontaneously Normally, apnea occurs after hyperventilation
Pressure relationships in the thoracic cavity •
Respiratory pressure is always described relative to atmospheric pressure
•
Atmospheric pressure ( P atm ) •
Pressure exerted by the air surrounding the body
•
Negative respiratory pressure is less than
•
Positive respiratory pressure is greater than
P atm P atm
Pressure relationships in the thoracic cavity •
Intrapulmonary pressure ( P pul )
•
pressure within the alveoli
•
Intrapleural pressure ( P ip )
Pressure relationships •
Intrapulmonary pressure and intrapleural pressure fluctuate with the phases of breathing
•
Intrapulmonary pressure always eventually equalizes itself with atmospheric pressure
•
Intrapleural pressure is always less than intrapulmonary pressure and atmospheric pressure
•
Tho forces act to pull the lungs away from the thoracic wall, promoting lung collapse
•
•
Elasticity of lungs causes them to assume smallest possible size
•
Surface tension of alveolar fluid draws alveoli to their smallest possible size
Opposing force – elasticity of the chest
Lung collapse •
Caused by equalization of the intrapleular pressure with the intrapulmonary pressure
•
Transpulmonary pressure keeps the airways open •
Transpulmonary pressure - the pressure difference across the lung. Alveolar pressure minus pleural pressure ( P alv - P pl )
Pulmonary ventilation A mechanical process that depends on volume changes in the thoracic cavity
Boyle's law Boyle's law – the relationship between the pressure and volume of gases P 1⋅V 1= P 2⋅V 2
How do we breath? •
Inspiration is normally active
•
Expiration is normally passive
Inspiration •
The diaphragm and external intercostal muscles (inspiratory muscles) contract and the rib cage
Expiration •
Inspiratatory muscles relax and the rib cage descends due to gravity
•
Thoracic cavity volume decreases
•
Elastic lings recoil passively and intrapulmonary volume decreases
•
Inrapulmonary pressure rises above atmospheric pressure (+1 mm Hg)
•
Gases flow out of the lungs down the pressure gradient
Airway resistance •
Friction is the major nonelastic source of resistance to airflow
•
The relationship between flow (F), pressure (P), and resistance (R) is: F = ΔP / R
•
The amount of the gases that flows in and out of the alveoli is directly proportional to ΔP, the pressure gradient between the atmosphere and alveoli
•
Gas flow is inversely proportional to resistance with the greatest being in the medium-sized ......
•
As airway resistance rises, breathing movements becomes more strenous
Alveolar surface tension •
Surface tension – the atrraction of liquid molecules to one another at a liquid-gas interface
•
The liquid coating the alveolar surface is always acting to reduce the alveolil to smallest size
•
Surfactant, a detergent-like complex, reduces surface tension and helps keep the alveoli from collapsing
Lung compliance •
The ease with which lungs can be expanded
•
Specifically, the measure of the change in lung volume that occurs with a given change in transpulmonary pressure
•
Determined by two main factors
Factors that diminish lung compliance •
Scar tissue or fibrosis
•
Blockage of the smaller passages
•
Reduced production of surfactant
•
Decreased flexibility
•
Examples include:
•
Deformities of thorax
•
Ossification of the costal cartilage
•
Paralysis of ontercostal muscles
Three ways to inflate the lungs •
Increase alveolar pressure – possitive pressure respirators
•
Decrease body surface pressure - “iron lungs”
•
Activate inspiratory muscles – normal way to breath
Cyclical variation of pressure •
Tidal volume: 500ml (350 alveoli)
•
FRC: ~3000ml --> (TV/FRC) ~10%
•
Cyclical variation in PaO2 and PaCO2 is small
Minute ventilation •
Flow (vol/time) moved into or out of the lungs
•
measured by collecting expired volume for a fixed time
•
Normal value is 7.5 L/min (BTPS)
•
V(.)e = Vt x f
Alveolar ventilation V.e = Vt x f
Anatomic dead space •
•
Volume of lung that is not involved in gas exchange •
Include: mouth, trachea ...
•
Ventilation of these areas results in no gas exchange
Estimating anatomical dead space in ml = ideal body weight measured in pounds
Alveolar dead sapce •
Treat lung as of only two types exist: •
With ideal gas exchange
•
With no gas exchange at all
•
Partition poorly ventilated units
•
Alveolar dead space as is
Physiological dead space Defenition – anatimical dead space + alveolar dead space
Partitioning minute ventilation •
Alveolar ventilation: the volume per min entering gas exchange surfaces
•
-V.a = Vt – Vds x f
•
Dead space ventilation: the volume per minute that is wasted
•
- V.ds = Vds x f
Ventilator adjucments & respiratory efficiency •
•
Increase tidal volume •
alveolar ventilation increases
•
dead space ventilation unchanged
increase respiratory frequency •
alveolar ventilation increases
•
dead space ventilation increases
Factors determining alveolar PaCO2 •
insoired air: no CO2
•
increaseing CO2 production
To supply the body with oxygen and dispose of CO2
•
Respiration – four distinct processes must happen: •
Pulmonary ventilation – moving air into and out of the lungs
•
External respiration – gas exchange between the lungs and blood
•
Transport – transport of oxygen and carbon dioxide between the lungs and tissues
•
Internal respiration – gas exchange between systemic blood vessels and tissues
Breathing •
Breathing, or pulmonary ventilation, consists of two phases: •
Inspiration – air flows into the lungs
•
Expiration
Eupnea •
Normal spontaneous breathing of which we are normally unaware
•
Ventilation is matched to metabolic demands
Hyperpnea •
Increased ventilation which matches increased metabolic demands such as exercise
•
Initially, increased ventilation is mainly increased tidal volume
•
Increased frequently is proportionately more important at higher intensities
Hyperventilation •
Inappropriately high ventilation for the metabolic demands
•
Hallmark. Alveolar and arterial are PCO2 decreased
•
Alveolar PO2 is increased
Tachypnea Increased frequency of breathing Ventilation may or may not be changed depending on what happens to tidal volume
Dyspnea Subjective sensation of difficulty to breath. Shortness of breath.
Apnea Temporary absence of cessation of breathing (usually at FRC) Implication that breathing will resume spontaneously Normally, apnea occurs after hyperventilation
Pressure relationships in the thoracic cavity •
Respiratory pressure is always described relative to atmospheric pressure
•
Atmospheric pressure ( P atm ) •
Pressure exerted by the air surrounding the body
•
Negative respiratory pressure is less than
•
Positive respiratory pressure is greater than
P atm P atm
Pressure relationships in the thoracic cavity •
Intrapulmonary pressure ( P pul )
•
pressure within the alveoli
•
Intrapleural pressure ( P ip )
Pressure relationships •
Intrapulmonary pressure and intrapleural pressure fluctuate with the phases of breathing
•
Intrapulmonary pressure always eventually equalizes itself with atmospheric pressure
•
Intrapleural pressure is always less than intrapulmonary pressure and atmospheric pressure
•
Tho forces act to pull the lungs away from the thoracic wall, promoting lung collapse
•
•
Elasticity of lungs causes them to assume smallest possible size
•
Surface tension of alveolar fluid draws alveoli to their smallest possible size
Opposing force – elasticity of the chest
Lung collapse •
Caused by equalization of the intrapleular pressure with the intrapulmonary pressure
•
Transpulmonary pressure keeps the airways open •
Transpulmonary pressure - the pressure difference across the lung. Alveolar pressure minus pleural pressure ( P alv - P pl )
Pulmonary ventilation A mechanical process that depends on volume changes in the thoracic cavity
Boyle's law Boyle's law – the relationship between the pressure and volume of gases P 1⋅V 1= P 2⋅V 2
How do we breath? •
Inspiration is normally active
•
Expiration is normally passive
Inspiration •
The diaphragm and external intercostal muscles (inspiratory muscles) contract and the rib cage
Expiration •
Inspiratatory muscles relax and the rib cage descends due to gravity
•
Thoracic cavity volume decreases
•
Elastic lings recoil passively and intrapulmonary volume decreases
•
Inrapulmonary pressure rises above atmospheric pressure (+1 mm Hg)
•
Gases flow out of the lungs down the pressure gradient
Airway resistance •
Friction is the major nonelastic source of resistance to airflow
•
The relationship between flow (F), pressure (P), and resistance (R) is: F = ΔP / R
•
The amount of the gases that flows in and out of the alveoli is directly proportional to ΔP, the pressure gradient between the atmosphere and alveoli
•
Gas flow is inversely proportional to resistance with the greatest being in the medium-sized ......
•
As airway resistance rises, breathing movements becomes more strenous
Alveolar surface tension •
Surface tension – the atrraction of liquid molecules to one another at a liquid-gas interface
•
The liquid coating the alveolar surface is always acting to reduce the alveolil to smallest size
•
Surfactant, a detergent-like complex, reduces surface tension and helps keep the alveoli from collapsing
Lung compliance •
The ease with which lungs can be expanded
•
Specifically, the measure of the change in lung volume that occurs with a given change in transpulmonary pressure
•
Determined by two main factors
Factors that diminish lung compliance •
Scar tissue or fibrosis
•
Blockage of the smaller passages
•
Reduced production of surfactant
•
Decreased flexibility
•
Examples include:
•
Deformities of thorax
•
Ossification of the costal cartilage
•
Paralysis of ontercostal muscles
Three ways to inflate the lungs •
Increase alveolar pressure – possitive pressure respirators
•
Decrease body surface pressure - “iron lungs”
•
Activate inspiratory muscles – normal way to breath
Cyclical variation of pressure •
Tidal volume: 500ml (350 alveoli)
•
FRC: ~3000ml --> (TV/FRC) ~10%
•
Cyclical variation in PaO2 and PaCO2 is small
Minute ventilation •
Flow (vol/time) moved into or out of the lungs
•
measured by collecting expired volume for a fixed time
•
Normal value is 7.5 L/min (BTPS)
•
V(.)e = Vt x f
Alveolar ventilation V.e = Vt x f
Anatomic dead space •
•
Volume of lung that is not involved in gas exchange •
Include: mouth, trachea ...
•
Ventilation of these areas results in no gas exchange
Estimating anatomical dead space in ml = ideal body weight measured in pounds
Alveolar dead sapce •
Treat lung as of only two types exist: •
With ideal gas exchange
•
With no gas exchange at all
•
Partition poorly ventilated units
•
Alveolar dead space as is
Physiological dead space Defenition – anatimical dead space + alveolar dead space
Partitioning minute ventilation •
Alveolar ventilation: the volume per min entering gas exchange surfaces
•
-V.a = Vt – Vds x f
•
Dead space ventilation: the volume per minute that is wasted
•
- V.ds = Vds x f
Ventilator adjucments & respiratory efficiency •
•
Increase tidal volume •
alveolar ventilation increases
•
dead space ventilation unchanged
increase respiratory frequency •
alveolar ventilation increases
•
dead space ventilation increases
Factors determining alveolar PaCO2 •
insoired air: no CO2
•
increaseing CO2 production
Related Documents
Physiology 8th Lecture - Respiratory System
June 2020 3
Physiology 1st Lecture - Physiology, Homeostasis
June 2020 5
Respiratory System Physiology
June 2020 11
Examville.com - Physiology - Respiratory System
May 2020 14