Perform lung function test

• Article
• 2021-02-18

Lung function tests, or PFTs, measure how well your lungs are working.

They include tests that measure lung size and air flow, such as spirometry and lung volume tests. Other tests measure how well gases such as oxygen get in and out of your blood. These tests include pulse oximetry and arterial blood gas tests. Another lung function test, called fractional exhaled nitric oxide (FeNO), measures nitric oxide, which is a marker of inflammation in the lungs. You may have one or more of these tests to diagnose lung and respiratory disease, compare your lung function to expected function levels, check if your disease is stable or getting worse, and if your treatment is working.

The purpose, procedure, inconvenience, and risks of each test will vary.

• Spirometry measures the speed of the air flow and estimates the lung size. In this test, you breathe several times, with regular and maximum effort, through a tube connected to a computer. Some people feel light-headed or tired with the required breathing effort.
• Lung volume tests are the most accurate way to measure how much air your lungs can hold. The procedure is similar to spirometry, except you are in a small room with bright walls. Some people feel light-headed or tired with the required breathing effort.
• The lung diffusion capacity determines how well oxygen gets into the blood from the air you breathe. In this test, you breathe in and out through a tube for several minutes without having to breathe intensively. You may also need to have blood drawn to measure the hemoglobin level in your blood.
• Pulse oximetry estimates the level of oxygen in your blood. For this test, a probe is placed on your finger or on another surface of skin such as your ear. It does not cause pain and has little or no risk.
• Arterial blood gas tests directly measure the levels of gases, such as oxygen and carbon dioxide, in your blood. Arterial blood gas tests are usually performed in a hospital, but can also be done in a doctor's office. For this test, blood is taken from an artery, usually in the wrist where your pulse is measured. You may feel momentary pain when the needle is inserted or when a tube attached to the needle fills with blood. You may have bleeding or infection where the needle was inserted.
• Fractional exhaled nitric oxide tests measure how much nitric oxide is in the air you exhale. For this test, you exhale into a tube connected to the wearable device. It requires steady but not intense breathing. It has few or no risks.

Other tests may be necessary to assess lung function in infants, children, or patients who cannot perform spirometry and lung volume tests. Prior to your tests, you may be asked not to eat certain foods or take certain medications that can affect the results of certain lung function tests.

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