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96 Cards in this Set

  • Front
  • Back
3 Components of the respiratory anatomy:
1. Airways
2. Exchange site
3. Muscles
What is the airway?
The conducting system
What 6 things compose the "Airway"?
1. Oral passages
2. Pharynx
3. Larynx
4. Trachea
5. Bronchi
6. Bronchioles
What does the Exchange site component of respiratory anatomy consist of?
-Pulmonary artery
-Pulmonary capillaries
-Pulmonary veins
What is the business end of the exchange site?
The site of gas exchange between alveoli and pulmonary capillaries.
What does the total # of alveoli reflect?
The total surface area available for gas exchange.
What does the Muscular system of the respiratory anatomy consist of?
1/2 = pump muscles
1/2 = airway muscles
What are the pump muscles?
Inspiratory & Expiratory
Inspiratory muscles:
-External intercostals
Expiratory muscles:
-Internal intercostals
Airway muscles:
-Upper airways = skeletal mm
-Bronchioles = smooth muscle
What is the chest wall composed of?
-Respiratory muscles
What is the chest wall equilibrium position?
60% of total lung inflation - it keeps the lungs inflated
What is the lung equilibrium position?
Total collapse
What is the equilibrium position of the respiratory system?
40% of VC = FRC --> the happy medium btwn chest wall elasticity and lung elasticity.
What can cause problems with breathing directly related to the pharynx?
Uncoordinated functions of breathing and swallowing - sleep apnea.
What exactly causes sleep apnea?
Improper physiological time sharing of the oropharynx, so the tongue obstructs the oropharynx.
What is the definition of Respiratory Mechanics?
A relationship between:
What happens as pressure within the respiratory system changes?
It results in changes in Airflow and Lung Volume.
What is the function of the thoracic cavity?
To generate the force needed for gas exchange to occur.
What limits the ability of the thoracic cavity to generate force for gas exchange?
The chest wall
What are the Chest Wall Components? (3)
1. Rib cage (most superficial)
2. Pleural space
3. Lungs/alveoli (deepest)
What 3 forces are involved in breathing? (forces=pressure)
1. Alveolar pressure
2. Pleural pressure
3. Transpulmonary pressure
What is alveolar pressure?
The air pressure within the air spaces of the lungs.
Why is alveolar pressure important for breathing?
It determines FLOW because it is the pressure that relates to airway resistance.
What is Alveolar pressure normally?
What happens when alveolar pressure is >0?
What happens when alveolar pressure is <0?
What is Pleural Pressure?
The air pressure between the chest wall and lungs.
What is the result of increased positive-ness of pleural pressure?
Expiration -> it compresses the lungs, squeezing the air out of them.
What is the result of increased negative-ness of pleural pressure?
Inspiration - it sucks on the lungs so air is pulled into them.
What is the normal equilibrium value of pleural pressure? Why?
Negative (due to chest wall elasticity and lung elasticity, each pulling in opposite directions)
What is Transpulmonary pressure?
The difference between alveolar and pleural pressure
What does Transpulmonary pressure reflect?
The lung's elasticity - recoil pressure.
What happens to the lungs when transpulmonary pressure increases?
They open up - dilate
What happens to the lungs when transpulmonary pressure decreases?
They are compressed.
What causes air to flow from the atmospher into alveoli during inspiration?
Changes in pressure - the alveolar pressure becoming subatmospheric.
What causes alveolar pressures to become subatmospheric during inspiration?
A decrease in pleural pressure
What causes pleural pressure to decrease during inspiration?
Inspiratory muscles contracting
-External intercostals
How does the contraction of inspiratory muscles decrease pleural pressure?
By increasing the volume of the pleural space in the thoracic cavity.
What causes pleural pressure to then become more POSITIVE during expiration?
The elastic recoil of the lungs - passively decreasing the volume and increasing pleural pressure.
What causes pleural pressure to increase during increased need for breathing?
Expiratory muscles - cause forced air expulsion.
Which change in pressure is more dramatic during breathing; that in alveoli or pleural?
Pleural pressure changes more dramatically during breathing than alveolar pressure.
Why does pleural pressure change more dramatically than alveolar during breathing?
Because pleural pressure has to overcome both the elasticity of the chest wall and the lungs in order to change alveolar pressure.
4 Important changes that occur during a complete breathing cycle:
1. Lung volume
2. Alveolar pressure
3. Pleural pressure
4. Transpulmonary pressure
How does Lung volume change during a complete breathing cycle (start of insp->end of exp)?
Start of insp: 0 mL
Mid of insp: 250 mL
Start of Exp: 500 mL
Mid of Exp: 100 mL
End of Exp: 0 mL
How does Alveolar pressure change during a complete breathing cycle?
Start of insp: 0
Mid of insp: -1
Start of Exp: 0
Mid of Exp: +1
End of Exp: 0
How does Pleural pressure change during a complete breathing cycle?
Start of insp: -5
Mid of insp: -7
Start of Exp: -7.5
Mid of Exp: -5.5
End of Exp: -5
How does transpulmonary pressure change during inspiration and expiration?
Inspiration = increased
Expiration = decreased
3 Forces that accomplish the Work of Breathing:
1. Force to expand the lung against its elastic properties
2. Force to overcome viscosity of lung and chest wall
3. Force to move air through airways
What work relates to the force that expands the lungs against their elastic properties?
Compliance work
What work relates to the force that overcomes viscosity of lung and chest wall?
Compliance work
What work relates to the force that moves air through the airways?
Airway resistance work
What is compliance, in a nutshell?
The ability of the lung to stretch
What is compliance, mathematically?
C = -----
Describe the equation for lung compliance:
Compliance equals the change in volume per change in transpulmonary pressure
What are the axes of the lung compliance curve?
X = pleural pressure
Y = change in lung volume
What changes occur on the compliance curve during inspiration? Expiration?
Insp: Ppl becomes more negative
as lung volume increases
Exp: Ppl becomes more positive as lung volume decreases
What happens to the compliance curve if pleural pressure changes more than normal?
Volume changes more than normal also - but to the same degree, so the loop just gets bigger.
What is alveolar pressure at the beginning of inspiration and expiration?
What is the result of alveolar pressure being zero?
Airflow is zero because
F = P(alv)/R
What can you find transpulmonary pressure on the lung compliance curve?
At the beginning and end of inspiration - because Palveolar is zero at those points, it just equals pleural pressure.
What represents compliance on the lung compliance curve?
The slope of the line because Slope = d(V)/d(Ptp)
And Ptp = Ppl at the points.
What is any point on the lung compliance diagram where pleural pressure exceeds Ptp?
Alveolar pressure
So where is pleural pressure?
Anything to the left of the sloped line.
Where is alveolar pressure?
Anything to the right of the line.
What does the pleural pressure to the left of the compliance curve indicate?
ELASTIC WORK: The pressure needed to overcome lung elasticity
What does the alveolar pressure to the right of the compliance curve indicate?
Resistive work - The pressure needed to overcome the loss of energy due to kinetic motion of molecules.
What does Alveolar pressure determine?
What determines airflow at any given alveolar pressure?
Resistance; R=Pa/Airflow
What happens to transpulmonary pressure as lung volume increases?
Ptp increases
What is the lung volume at the lung's equilibrium position (alone)?
What is reflected by Ptp as lung volume is increased during inhalation?
Lung elastic recoil pressure - because the lung wants to collapse back to zero.
When is the only time that pleural pressure becomes positive?
During forced expiration
What is the difference between static and dynamic lung compliance?
The method used to assess each
How is dynamic lung compliance measured?
By obtaining Ptp from Ppl when airflow = zero
How is static lung compliance measured?
By having the person hold their breath at different lung volumes; since airflow=zero Pleural pressure reflects Ptp.
How do dynamic and static lung compliance msmts compare?
They should be equal in healthy patients, but might be different in diseased.
How does filling a lung with saline affect it?
Saline negates the effect of surface tension at the air-surfactant interface.
How does the lung compliance curve change when a lung is filled with saline?
-It takes much less pleural pressure to fill the lung, so the loop is shifted to the left
-Hysteresis is eliminated
What is hysteresis?
The difference between the inspiration and expiration loops on a lung compliance diagram.
What causes hysteresis?
The surface tension on alveoli
What is surface tension?
The force caused by mutual attraction of liquid molecules on an air-liquid interface which tends to collapse alveoli.
What are the implications of surface tension for our air/saline expirement?
It takes much more pressure to fill a lung with air than to fill it with saline.
What happens to surface tension
-during inspiration
-during expiration
Insp: surf tension increases
Exp: surf tension decreases
Why does surface tension increase during inspiration?
Because as the alveoli get bigger the surfactant spreads out and is less effective in reducing the collapsing pressure.
What is the function of surfactant?
To prevent small alveoli from collapsing and emptying into larger alveoli as the lungs deflate.
What law describes collapsing pressure of alveoli?
Law of Laplace
Collapsing P = ---
What has a bigger collapsing pressure normally?
Small alveolus
Why does a small alveolus not empty faster than large during expiration?
Because surfactant reduces T so P is less than for large alveoli
What cells secrete surfactant?
Type II pneumocytes
What happens to lung compliance in an emphesymatous patient?
It is greatly increased because of destruction of lung elastic tissue.
What happens to lung compliance in a fibrotic individual?
It is greatly reduced because the lungs become stiff.
How is vital capacity changed in a person with:
Emph: VC is increased
Fibr: VC is decreased
What is elastic recoil pressure changed at 60% VC in:
Emph: P=5
Norm: P=11
Fibr: P=17
How is lung compliance regulated?
Not physiologically!
If it's changed, its due to disease.