Pulmonary compliance (or lung compliance) is the ability of the lungs to stretch in a change in volume relative to an applied change in pressure.^[1]

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

Clinical significance

It is an important measurement in respiratory physiology.^[2][3][4]

• fibrosis is associated with a decrease in pulmonary compliance.
• emphysema/COPD may be associated with an increase in pulmonary compliance due to the loss of alveolar and elastic tissue.

Pulmonary surfactant increases compliance by decreasing the surface tension of water which tends to provide a force to collapse alveolar volume.

Calculation

Compliance is calculated using the following equation, where ?V is the change in volume, and ?P is the change in pressure:^[5]

C = \frac{ \Delta V}{ \Delta P}

For example if a patient inhales 500 ml of air from a spirometer and pleural pressure before inspiration is ? 5 cm H2O and -10 cm H2O at the end of inspiration. Then: Compliance= DeltaV/DeltaP=.5L/(-5cm H2O- (-10cm H2O))=.5L/5 cm H2O=0.1 L/cm H2O

References

fr:Compliance pulmonaire pt:Complacência pulmonar

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