Respiratory 14 Flashcards
What is lung compliance?
A measure of the elastic properties of the lungs and a measure or how easily the lungs can expand
What kind of property Lung Compliance?
A dynamic and static property
Why can compliance be a static and dynamic property?
Because it can be measured in the presence and absence of airflow
What is lung compliance given by?
The magnitude of the lung volume produced by given change in transpulmonary pressure
What is compliance the slope of?
A pressure volume curve
What pressure is most important in determining lung volume?
Transpulmonary pressure
What does Static Compliance represent?
The lung compliance measured during periods of no gas flow, such as during an inspiratory/expiratory pause
When is Static Compliance measured?
During functional residual capacity
How is static lung compliance measured?
A patient is asked to make a maximal inspiration and then release a small amount of air. This is when transpulmonary pressure and lung volume is measured. This is repeated at intervals
In what disease would a high lung compliance be seen?
Emphysema
In what disease would a low lung compliance be seen?
In pulmonary fibrosis
What does a stiff lung mean in terms of transpulmonary pressure?
The patient has to make a big effort to expand the chest wall in order to increase transpulmonary pressure that is responsible changing the lung volume
What occurs with transpulmonary pressure in people with high compliance lungs?
A small change in transpulmonary pressure will result in big changes in lung volume
What is flow determined by when measuring dynamic compliance?
- The difference in pressure between the atmosphere and the alveoli
- Airway resistance against which standing forces have to act
When is dynamic compliance measured?
During airflow so either during expiration or inspiration
What does Dynamic compliance reflect?
- Lung stiffness
* Airway resistance that may reduce expansion of the lungs
Why is Dynamic compliance usually lower or smaller than the static compliance?
Because dynamic compliance takes airway resistance into consideration
When does dynamic compliance fall?
When either lung stiffness or airway resistance increases
What is FRC?
Functional Residual Capacity and is the capacity of the lungs after normal expiration
How is the slope of the curve affected during dynamic compliance and static compliance?
The slope of the curve will be reduced in dynamic compliance and will be increased during static
Which airways are collapsed when the lungs are collapsed?
All the medium and small airways
What change in transpulmonary pressure opens the lungs?
An increase in transpulmonary pressue
What is lung Hysteresis on a collapsed lung?
1) increasing transpulmonary pressure has little effect the airways
2) The first airways open and this is followed by other airways
3) When all the airways are open and the volume increases in a linear fashion
4) when volume reaches its max lung compliance decreases
What do changes in pressure and lung volume (lung compliance) look like in a normal healthy patient?
Changes in pressure and volume are minimal
What is Hysteresis?
The difference between the inflation and the deflation compliance path
Why does Hysteresis exist?
Because you have to use more pressure to open an airway rather than keeping an airway that is already open open
