Lung function tests
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What are lung function tests?

Lung function tests1-3 are important tools that healthcare providers use during the process of diagnosing a person with asthma. Lung function tests are also called “pulmonary function tests.” These tests use different ways of measuring how well a person’s lungs are working.
There are several different types of lung function tests:

Spirometry tests and peak flow tests are usually the first types of tests that healthcare providers use to diagnose asthma. Patients usually take these tests before and after they have taken a bronchodilator medicine (such as albuterol). This type of medicine helps to open up the airways in people who have asthma, and improves their ability to breathe. If the test results show that a person’s lungs are functioning better after taking this medicine than before taking it, then it is likely the person has asthma.
Sometimes, the results of your spirometry tests and peak flow tests don’t provide enough information for your healthcare provider to decide whether or not you have asthma. This means that your healthcare provider may need to use challenge tests or the exhaled nitric oxide test to get more information.

What is a spirometry test?

Taking a spirometry test is very simple. You will be asked to take a deep breath and exhale quickly into a special machine called a spirometer. The spirometer measures the amount of air you can breathe into your lungs, and the speed that you can exhale the air out of your lungs.1-3 Asthma causes inflammation in the airways that can affect the amount and speed of air you can inhale and exhale from your lungs.

What is a peak flow test?

A peak flow test is similar to a spirometry test. During the test, you will be asked to take your deepest breath and then exhale as hard as possible into a small machine called a peak flow meter. This test measures how quickly you can force air out of your lungs, which is a sign of how well your lungs are able to work.1-2

What are challenge tests?

Challenge tests, which are also called trigger tests, are used to measure the function of your lungs in a different way. During this type of test, you will be asked to breath in a very small amount of a substance (either methacholine or mannitol) and then take a spirometry test and/or peak flow test.1-3
These substances are known to cause breathing symptoms in people who have asthma. So if the results of the breathing tests show that your lung function is mildly worse than it was before you inhaled the substance, it is a sign that you probably have asthma. If you do not have asthma, then your lung function will not be affected by inhaling the substance.

What is a nitric oxide test?

Nitric oxide testing is a little less common than the other types of lung function tests. This test measures the amount of nitric oxide that is produced by your lungs by analyzing the air you exhale into a small machine. If you have higher levels of nitric oxide in your lungs, it can be a sign that there is inflammation in your airways caused by asthma.1-3

view references
  1. Mayo Clinic. Tests and Diagnosis. Accessed March 20, 2016. Available at http://www.mayoclinic.org/diseases-conditions/asthma/basics/tests-diagnosis/con-20026992
  2. Asthma and Allergy Foundation of America. Asthma Diagnosis. Accessed March 20, 2016. Available at http://www.aafa.org/page/asthma-diagnosis.aspx
  3. Cleveland Clinic. Diagnosing Asthma. Accessed March 20, 2016. Available at https://my.clevelandclinic.org/health/diseases_conditions/hic_Asthma_An_Overview/hic_Diagnosing_Asthma
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