Pulmonary compliance

Pulmonary compliance (or lung compliance) can refer to either dynamic or static lung compliance. Static lung compliance is the change in volume for any given applied pressure. Dynamic lung compliance is the compliance of the lung at any given time during actual movement of air.

The compliance of the lungs demonstrate hysteresis, that is the compliance is different on inspiration and expiration for identical volumes. SeeHysteresis#Respiratory_physiology.

Compliance is greatest at moderate lung volumes, and much lower at volumes which are very low or very high.

Calculation

Static compliance is calculated using the following equation, where ΔV is the change in volume, and ΔP is the change in pleural pressure:

<math>C = frac </math>

For example if a patient inhales 500 mL of air from a spirometer and intrapleural pressure before inspiration is – 5 cm H₂O and -10 cm H₂O at the end of inspiration. Then: <br /><math> Compliance = frac = frac = frac = 0.1;L;times;cmH_2O^</math>

Dynamic lung compliance is ≤ static lung compliance. Dynamic lung compliance is calculated using the following equation, where CD = Dynamic compliance; VT = tidal volume; PIP = Peak inspiratory pressure; PEEP = Positive End Expiratory Pressure):

<math>CD = frac</math>

Clinical significance

It is an important measurement in respiratory physiology....
Read More