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What Are Lung Function Tests?

Lung function tests, also called pulmonary (PULL-mun-ary) function tests, measure how well your lungs work. These tests are used to look for the cause of breathing problems, such as shortness of breath.

Lung function tests measure:

  • How much air you can take into your lungs. This amount is compared to that of other people your age, height, and sex. This allows your doctor to see whether you're in the normal range.
  • How much air you can blow out of your lungs and how fast you can do it.
  • How well your lungs deliver oxygen to your blood.
  • The strength of your breathing muscles.

Doctors use lung function tests to help diagnose conditions such as asthma, pulmonary fibrosis (scarring of the lung tissue), and COPD (chronic obstructive pulmonary disease).

Lung function tests also are used to check the extent of damage caused by conditions such as pulmonary fibrosis and sarcoidosis (sar-koy-DOE-sis). Also, these tests may be used to check how well treatments, such as asthma medicines, are working.

Overview

Lung function tests include breathing tests and tests that measure the oxygen level in your blood. The breathing tests most often used are:

  • Spirometry (spi-ROM-eh-tre). This test measures how much air you can breathe in and out. It also measures how fast you can blow air out.
  • Lung volume measurement. This test, in addition to spirometry, measures how much air remains in your lungs after you breathe out fully.
  • Lung diffusion capacity. This test measures how well oxygen passes from your lungs to your bloodstream.

These tests may not show what's causing breathing problems. So, you may have other tests as well, such as a cardiopulmonary exercise test. This test measures how well your lungs and heart work while you exercise on a treadmill or bicycle.

Two tests that measure the oxygen level in your blood are pulse oximetry and arterial blood gas tests. These tests also are called blood oxygen tests.

Pulse oximetry measures the blood oxygen level using a special light. For an arterial blood gas test, your doctor inserts a needle into an artery, usually in your wrist, and takes a sample of blood. The oxygen level of the blood sample is measured.

Outlook

Lung function tests usually are painless and rarely cause side effects. You may feel some discomfort during an arterial blood gas test when the needle is inserted into the artery.

For more information about healthy lung function, go to the Health Topics How the Lungs Work article.

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Lung Function Tests Clinical Trials

Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans. To find clinical trials that are currently underway for Lung Function Tests, visit www.clinicaltrials.gov.

 
August 01, 2010 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.

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