Lung Function Tests

Lung function tests (also called pulmonary function tests, or PFTs) check how well your lungs work. The normal value ranges for lung function tests will be adjusted for your age, height, sex, and sometimes weight and race. Results are often expressed in terms of a percentage of the expected value. Most test results are available right away.

Normal

Test results are within the normal ranges for a person with healthy lungs.

Abnormal

Test results are outside of the normal range for a person with healthy lungs. This may mean that some kind of lung disease is present. There are two main types of lung disease that can be found with lung function tests: obstructive and restrictive.

Obstructive

In obstructive lung conditions, the airways are narrowed, usually causing an increase in the time it takes to empty the lungs. Obstructive lung disease can be caused by conditions such as Reference emphysema Opens New Window, Reference bronchitis Opens New Window, infection (which produces inflammation), and Reference asthma Opens New Window.

FEV1 often increases after using medicine that expands the airways in people with reversible obstructive disease like asthma.

Restrictive

In restrictive lung conditions, there is a loss of lung tissue, a decrease in the lungs' ability to expand, or a decrease in the lungs' ability to transfer oxygen to the blood (or carbon dioxide out of the blood). Restrictive lung disease can be caused by conditions such as Reference pneumonia Opens New Window, lung cancer, Reference scleroderma Opens New Window, Reference pulmonary fibrosis Opens New Window, Reference sarcoidosis Opens New Window, or Reference multiple sclerosis Opens New Window. Other restrictive conditions include some chest injuries, being very overweight (Reference obesity Opens New Window), pregnancy, and loss of lung tissue due to surgery.

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