Pulmonary Function Testing

What is pulmonary function testing?

Pulmonary (say: POOL-muh-nair-ee) function testing is a series of breathing tests. It measures how well your child�s lungs are working. If your child takes medicine to help him breathe, pulmonary function testing can help figure out how well the medicine is working.

Pulmonary function tests do not hurt. But in order for the tests to work, your child must be prepared to give his full effort. It can be hard work, especially if your child has a breathing problem. Your child must be able to follow very specific instructions and must be willing to cooperate and try his best. 

How to prepare your child for the test

You can prepare your child for pulmonary function testing by making sure that he knows what to expect.

After reading this information carefully, describe the test to your child in a way that he will understand. Make sure your child understands that this test does not hurt. It requires him to be cooperative and follow the pulmonary technologist�s instructions.

You can tell your child, "You are going to be doing some breathing exercises into a machine. You are going to pretend to blow out all of Mommy's candles on her birthday cake. Or pretend to blow up a balloon." 

How long a pulmonary function test may take

A pulmonary function test can take between 15 minutes and 1 hour, depending on how many tests are needed.

Before a pulmonary function test

You do not need to do anything special to get ready for a pulmonary function test.

If your child takes breathing medicine, you may be asked not to give it to him on the day of the test.

Who will be involved with this test

A specially trained pulmonary technologist will test your child�s lungs. A respirologist reads or interprets the test. A respirologist is a doctor who specializes in the study of lungs and breathing.

How the test is done

When a pulmonary technologist is ready, your child will go into the pulmonary function lab. We prefer that parents remain in the waiting room during the test. This helps the child focus on the pulmonary technologist�s instructions so the test goes quickly and smoothly.

Before testing, your child�s height and weight will be measured. Then your child will sit down in a chair in front of a long tube attached to a computer.


  • Pulmonary Function Testing
    Child undergoing pulmonary function test
    For spirometry, your child puts his mouth around a disposable filter which serves as a mouthpiece. This is attached directly to the spirometer.
  • Your child will wear a nose clip to make sure he is breathing only from his mouth during the test.
  • While keeping his mouth sealed around the mouthpiece, your child will be told to breathe in and out normally for a few seconds.
  • Your child will then be asked to take in the biggest breath possible, then blow out as hard, as fast, and as long as possible.
  • The computer will measure how much and how fast air can be blown out of your child�s lungs.

Spirometry is the main test that your child should expect to do during pulmonary function testing. There are other types of breathing tests that your child may be asked to perform.

After the testing

The respirologist will review your child�s pulmonary function test results. This can take up to 2 to 4 weeks. A report will then be sent to your doctor. Your doctor will discuss the results of the test with you at a follow-up appointment.

Side effects

There are no side effects or after-effects from a pulmonary function test.

Key points

  • Pulmonary function testing is a series of breathing tests. They measure how well your child�s lungs are working.
  • The main test is called spirometry. During spirometry, your child will be asked to breathe into a mouthpiece so a computer can measure how much and how fast air can be blown from your child�s lungs.
  • Pulmonary function tests do not hurt.

Laura Seed, M.Sc., RCPT(p)
Allan Coates, MD
Susan Carpenter, RN
Jennifer Leaist, RN, BScN


At SickKids:

Pulmonary function tests are done in the Pulmonary Function Lab of the Respiratory Medicine Department.