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compliance.pptx
1. Pulmonary Compliance
The compliance is the ratio between the change in
volume to the change in distending pressure
(transmural pressure). i.e., C = ∆V / ∆P.
2. - Compliance of the lung can be defined as the extent to which
the lung expands for each unit increase in its transmural
pressure.
- For the lungs, transmural pressure = intrapulmonary pressure –
intrapleural pressure. It is called "transpulmonary pressure".
- The normal compliance of the lungs in the average adult human
is approximately 200 ml/cm of water pressure. That is every
time, the transpulmonary pressure increase by one centimeter of
water, the lungs expand 200 milliliters.
4. - From the curve, one can conclude:
The compliance of the lung is more during expiration
(BZA) than during inspiration (AXB). This is known as
"hysteresis" (i.e., forward path is different from the
reverse path). Why????????
The compliance of the lung is determined by the diagonal
line (BYA) connecting the two ends of the curve (average
lung compliance)
5. Factors affecting compliance:
1. Factors in the lung:
- It is affected by elastic forces of the lung (1/3 of compliance) and surface tension
of the fluid lining the alveoli (2/3 of the compliance).
- Lung compliance is decreased in pulmonary congestion, pulmonary fibrosis and
pulmonary edema whereas it is increased in emphysema.
- It is affected by the elastic properties of the thorax caused by elasticity of the
muscles, tendons and connective tissues in the chest wall.
- Chest wall compliance is decreased in case of:
* Deformities of spine. *Arthritis of vertebra.
*Skeletal muscle disease e.g. poliomyelitis. * Obesity.
2. Factors in the chest wall:
