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Medical Tests & Exams


What It Is

Spirometry is a quick, painless test in which a handheld device called a spirometer measures how much air a person’s lungs can hold (also called air volume) and the speed of inhalations and exhalations during breathing (also called flow rate).

This test is used in children older than 5 years. The spirometer has two pieces: a mouthpiece and a tube that connects to a machine, which records and displays the results.

Why It’s Done

Spirometry tells health care professionals how well the lungs are working. It’s used to help diagnose and monitor diseases that affect the lungs and make breathing difficult, such as asthma and cystic fibrosis. It also can be used to:

  • find the cause of shortness of breath, coughing, or wheezing
  • monitor treatment of respiratory problems
  • evaluate lung function before surgery


Before the test, your child should avoid cold medicines, caffeine, carbonated beverages, and exposure to tobacco smoke. Your child also should avoid eating a big meal before the test.

If your child is taking any medications, the doctor might have your child stop taking them for a certain amount of time before the test. The doctor also may ask you to have your child practice for the test, such as by pretending to blow out birthday candles or blowing air at a pinwheel.

On the day of the test, make sure that your child doesn’t wear tight clothing that could interfere with the ability to breathe in and out deeply.

The Procedure

Your child will be asked to follow instructions given during the test. Cooperation is essential for accurate results.

Depending on the doctor’s recommendations, your child might have to wear soft nose clips during the procedure to prevent air from escaping. Your child also may be asked to stand during the test. If seated while the test is performed, your child should not lean forward because this can affect breathing.

Typically, your child will be asked to take a very deep breath, place the device in his or her mouth with the lips sealed securely around the mouthpiece, and then exhale as fast and hard as possible for as long as possible. The test may be repeated several times to confirm the accuracy of the results.


Spirometry is often performed before and after an inhaled asthma medication called a bronchodilator is administered. This can help determine whether a lung problem can be treated with specific medications.

Spirometry usually takes 5-30 minutes, depending on the number of times the test must be done.

What to Expect

Your child might be asked to perform the test more than once to ensure accurate results. The test should be completely painless.

Getting the Results

The results are recorded while the test is being done, and some machines are programmed to review results and suggest interpretations. However, your doctor also will review the results and explain to you what they mean. The results are expressed as percentages and are generally considered abnormal if they’re less than 80% of the normal value based on your child’s age, gender, height, and weight.


Spirometry is considered a safe procedure with little risk. Because the test requires kids to breathe quickly and deeply, some may experience temporary shortness of breath or lightheadedness. This test shouldn’t be performed on kids who have chest pain, a recent history of eye or abdominal surgery, or serious heart disease.

Helping Your Child

You can help prepare your child for spirometry by explaining the importance of following the instructions of the person administering the test.

If You Have Questions

If you have questions or concerns about spirometry, be sure to speak with your doctor or the person administering the test.

Reviewed by: Yamini Durani, MD
Date reviewed: March 2015