What Is a Pulmonary Function Test?


Quick Answer

Pulmonary function tests are non-invasive diagnostic tests that measure how well the lungs are working, according to Healthline. They provide feedback about lung volumes, capacities, rates of flow and gas exchange that doctors can use to help diagnose certain lung conditions.

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Full Answer

Pulmonary function tests may include spirometry, a test that measures how much air a person breathes in and out. A plethysmography test is conducted to measure the volume of gas in the lungs. Diffusion capacity, which shows how well the lungs exchange gases, is measured by giving a tracer gas to the patient. Pulmonary function tests can be used to diagnose chronic bronchitis, lung fibrosis, chronic obstructive pulmonary disease or lung cancer, adds Healthline.

Complications from the procedure are generally low, since pulmonary function testing is non-invasive, states Johns Hopkins Medicine. Patients may be asked to wear a bronchodilator after undergoing certain tests, and patients are monitored during the tests for signs of dizziness, faintness or difficulty breathing. Normal results, which are expressed as percentages, are based on the patient's age, height, ethnicity and gender, but values are considered abnormal if they fall below 80 percent of the patient's predicted value, notes MedlinePlus. Abnormal results may mean that the patient has lung or chest disease.

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