Pulmonary function tests

Pulmonary function tests (PFTs) are a group of tests that measure how well the lungs take in and release air and how well they move gases such as oxygen from the atmosphere into the body's circulation.

Overview

Pulmonary function tests are done to:

• Diagnose certain types of lung disease such as asthma, bronchitis, and emphysema
• Find the cause of shortness of breath
• Measure whether exposure to chemicals at work affects lung function
• Check lung function before someone has surgery

Types of Pulmonary Function Tests

Pulmonary function tests include:

• Spirometry: This is the most common PFT. Spirometry measures the rate of air flow and estimates lung size. For this test, you breathe into a mouthpiece attached to a machine. The machine records the results.

• Lung volume test: This test measures the amount of air in your lungs, including the air that remains at the end of a normal breath. It also measures how much air remains in your lungs after you have exhaled (breathed out) as much as you can.

• Diffusing capacity test: This test measures how well the lungs exchange gases. This is an important part of lung function. For this test, you breathe in a harmless gas for a very short time. The machine measures how much gas is exhaled.

Results

The results of the tests will be compared with normal values for someone of the same age, height, sex, and race. Results are usually given as a percentage. A value is usually considered abnormal if it is less than 80% of the predicted value.

Risks

Pulmonary function tests are generally safe. Some people may feel short of breath or lightheaded after doing the tests. Rarely, the tests can cause a collapsed lung.

See also

• Respiratory system
• Lung disease
• Spirometry
• Lung volume
• Diffusing capacity