Compliance And The Lungs

There are two lungs inside the chest cavity. Each is surrounded by a membrane called the pleura. Each lung is divided into parts called lobes. The right lung has three lobes and the left lung has two lobes.

You'll frequently hear the term "lung compliance" used when measuring the functionality of the lungs. Compliance is the ability of the lungs to be distended and is expressed as a change in volume per unit change in pressure. That is, a measurement of how well the lungs can stretch when filling with air.

There are two factors that affect compliance. These are the connective tissue that consists of collagen and elastin and surface tension in the alveoli, which is controlled by surfactant. Surfactant is a substance that lowers surface tension in the alveoli, thereby preventing interstitial fluid from entering the alveoli.

Compliance is increased in patients who have chronic obstructive pulmonary disease (COPD). Compliance is decreased with patients who have restrictive pulmonary disease. A decrease in compliance results in a decreased lung volume. That is, the lungs become stiff requiring more-than-normal pressure to expand the lungs. This is typically caused by an increase in connective tissue or an increase in surface tension in the alveoli.

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