Skip to content

    Lung Disease & Respiratory Health Center

    Font Size

    Lung Function Tests

    In rare cases, a bronchospasm can occur with inhalation challenge testing. You will be closely monitored during and after the test.

    Exercise stress tests

    Exercise stress tests evaluate the effect of exercise on lung function tests. Spirometry readings are done after exercise and then again at rest.

    Multiple-breath washout test

    The multiple-breath washout test is done to check lung function in people with cystic fibrosis. For this test, you breathe air that contains a tracer gas through a tube. Then you breathe regular air while the amount of tracer gas you exhale is monitored. Test results are reported as a lung clearance index (LCI). A high LCI value means that the lungs are not working well.

    Lung function results are measured directly in some tests and are calculated in others. No single test can determine all of the lung function values, so more than one type of test may be done. Some of the tests may be repeated after you inhale medicine that enlarges your airways (bronchodilator).

    Why It Is Done

    Lung function tests are done to:

    • Determine the cause of breathing problems.
    • Diagnose certain lung diseases, such as asthma or chronic obstructive pulmonary disease (COPD).
    • Evaluate a person's lung function before surgery.
    • Check the lung function of a person who is regularly exposed to substances that can damage the lungs.
    • Check the effectiveness of treatment for lung diseases.

    How To Prepare

    Tell your doctor if you:

    • Have had recent chest pains or a heart attack.
    • Take medicine for a lung problem such as asthma. You may need to stop taking some medicines before testing.
    • Are allergic to any medicines.
    • Have had recent surgery on your eyes, chest, or abdomen, or if you have had a collapsed lung (pneumothorax).

    Do not eat a heavy meal just before this test because a full stomach may prevent your lungs from fully expanding. You should not smoke or exercise vigorously for 6 hours before the test. On the day of the test, wear loose clothing that does not restrict your breathing in any way. You should also avoid food or drinks that have caffeine because it can cause your airways to relax and allow more air than usual to pass through.

    If you have dentures, wear them during the test to help you form a tight seal around the mouthpiece of the spirometer.

    1 | 2 | 3 | 4 | 5 | 6 | 7

    WebMD Medical Reference from Healthwise

    Last Updated: /2, 14 1
    This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

    Today on WebMD

    man coughing
    You may not even know you have it.
    blood clot
    Signs of this potentially fatal complication.
    man coughing
    When a cold becomes bronchitis.
    human lungs
    Causes behind painful breathing, fluid buildup.

    chest x-ray
    Bronchitis Overview
    Copd Myth Fact Quiz
    Energy Boosting Foods

    woman coughing
    Lung xray and caduceus