How Do You Calculate Lung Capacity?


Quick Answer

Doctors calculate lung capacity using lung function tests, notes WebMD. These tests are useful in determining how much air the lungs hold and how rapidly the person can move air into and out of the lungs. In addition, lung function tests can determine how efficient the lungs are in removing carbon dioxide from the blood and returning oxygen to the blood.

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Full Answer

Lung function tests are sometimes called pulmonary function tests, notes WebMD. Doctors use these tests to make diagnoses of lung disease or to determine the extent of damage to the lungs from lung disease. Doctors may also order lung function tests to gauge the progress of treatment for existing lung disease.

Doctors may also order gas diffusion tests, inhalation challenge tests and residual volume tests to diagnose or monitor lung disease. Other tests include exercise stress tests and body plethysmography.

The most common test of pulmonary capacity and function is spirometry testing. During the test, the patient breathes into a mouthpiece that is attached to a spirometer, which records how fast air moves out of the lungs and how much air moves out of the lungs. There are several different spirometry tests, including those that measure functional residual capacity at the end of a normal exhaled breath and those that measure total lung capacity as the patient inhales deeply.

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