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Medical Tests & Exams

Spirometry: Pre and Post Beta-Agonist

What It Is

Spirometry pre and post beta-agonist is a quick, painless test in which a device called a spirometer is used to measure how much air a person’s lungs can hold (air volume) and the speed (air flow rate) of inhalation and exhalation during breathing, both before and after receiving a medication (beta-agonist).

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

Why It’s Done

Beta-agonists are medications that affect the muscles around the airways in the lungs. In people with asthma, these muscles tighten when the airways become irritated, which can result in breathing difficulties and wheezing. Beta-agonists help these muscles relax, allowing the air passages to widen, which makes breathing easier.

Most beta-agonists are given by inhalation. Spirometry pre and post beta-agonist lets health care professionals test the effectiveness of these medications for a particular child and gauge how well his or her lungs are working with and without the medication.


Before the test, your child should avoid cold medicines, caffeine, carbonated beverages, and exposure to tobacco smoke. Your child also should not eat a big meal before the test.

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

On the day of the test, make sure 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, and may be asked to stand during the test. If seated during the test, your child should sit up straight and 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. Your child will be asked to perform this test before and after inhaling a medication. The test may be repeated several times to confirm the accuracy of the results.

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.

Helping Your Child

You can help prepare your child for spirometry pre and post beta-agonist 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 pre and post beta-agonist, speak with your doctor or the person administering the test.

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