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Lung compliance
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Inflating a lung takes work, and lung compliance measures how much. It is how much volume the lung gains for each change in transpulmonary pressure .. the difference in pressure between the inside of the lung and what surrounds it .. and it is calculated by dividing volume by pressure.
Two things determine it. One is the elastic fibers of the tissue. The other is surface tension inside the alveolus, the force that makes the wet walls tend to stick together; surfactant, the film that lines the inside of the alveolus, lowers it so the lung inflates more easily.
Compliance is the opposite of elastic recoil, also called elastance, which is the lung's tendency to spring back. Low compliance means a stiff lung. It is like two balloons: a new one that is hard to inflate and a stretched-out one that gives with a puff.
Diseases move it in both directions. In pulmonary fibrosis and interstitial lung disease, compliance falls. In emphysema the opposite happens: the elastic fibers are lost and the lung becomes more compliant.
In brief
Lung compliance is the change in lung volume for each change in transpulmonary pressure: volume divided by pressure.
Two factors drive it: the elastic fibers of the tissue and alveolar surface tension, which surfactant lowers.
It is the opposite of elastance, or elastic recoil: low compliance means a stiff lung.
Two balloons: a new one that is hard to inflate and a stretched-out one that gives with a puff.
It falls in fibrosis and interstitial lung disease; in emphysema, loss of elastic fibers raises it.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Pulmonary Compliance, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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