Week 3 - Lung Compliance Flashcards
What units are used to measure trans-pulmonary pressure?
cm H2O
By definition, what is atmosphere’s pressure?
0 cm H2O
At the beginning of a normal tidal volume breath, what is the pressure found in the alveoli?
0 cm H2O
At the beginning of a normal tidal volume breath, what is the pressure found in the pleural space?
-5 cm H2O
What is trans-pulmonary pressure?
The pressure difference between what is in the alveoli and what is in the pleural space.
What is the equation for trans-pulmonary pressure?
P(TP) = P(ALV) - P(PL) The quantity is with respect to being in the alveoli
If pressure in the alveoli is 0 and there is a negative pressure found in the pleural space, what will happen?
The lungs will expand.
What is pneumothorax?
When a breach of the thoracic cavity causes air from the atmosphere to move to the pleural space which forces the lung to collapse. In other words, because there is no trans-pulmonary pressure, there is no force keeping the lungs distended out.
What is lung compliance?
A measure of how easily the lung can be stretched out or inflated. Therefore, compliance is similar to distensibility.
What is the equation for compliance?
C = dV /dP
where dV = change in volume
and dP = change in pressure
Describe normal compliance
Normal value is around 0.2 liters of air per cm H2O and compliance decreases as one moves up the curve.
Describe low lung compliance
There is a relatively small change in lung volume for a given change in Pressure (dV/dP). Also, if one has a low lung compliance, it means that they have a very high recoil.
Describe high lung compliance
There is a relatively large change in lung volume for a given change in Pressure (dV/dP). Also, if one has a high lung compliance, it means that they have a very low recoil.
In what instance would you find someone with lungs that have low compliance?
someone with pulmonary fibrosis
In what instance would you find someone with lungs that have high compliance?
someone with emphysema.