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Diagnostic Test Guide

Pulmonary Function Test

Pulmonary function tests (PFTs) are the main way to measure lung function. Several different types of tests can be done:

Child performing a spirometry test

  • Spirometry: This measures how much air is breathed in and how well air moves in and out of the lungs. It can help find obstruction (blockage) in the airways. Sometimes a medicine (albuterol) is given to see if it helps the airways open. This test can help doctors diagnose things like asthma or bronchiolitis obliterans.

    • Your child will take a big breath in and blow out the air as hard and fast as they can. They will wear a nose clip during the test. Usually children need to be 5 or 6 years old to be able to do this testing.

  • Plethysmography (lung volumes): This measures how much air the lungs can hold. This test can help doctors measure lung stiffness or air trapping.

    • Your child will stand in a clear box and do some deep and regular breathing. Usually children need to be 8–10 years old to be able to do this testing.

  • Diffusion capacity (DLCO): This measures how well the lungs can move oxygen from the air sacs (alveoli) to the bloodstream. Extra inflammation or scarring in the lungs can cause this number to be low.

    • Your child will breathe all the way out and then take a quick breath in. They will hold their breath and then breathe out. Usually children need to be 8–10 years old to be able to do this testing.

  • 6 Minute Walk Testing (6MW): This test measures how far your child can walk in 6 minutes. It measures their heart rate and oxygen levels every minute to make sure oxygen levels don’t drop during exercise. Sometimes kids with chILD will have normal oxygen levels at rest, but oxygen levels drop during exercise.

    • Your child will walk back and forth between 2 markers for 6 minutes. They should walk as fast as they can without running. A pulse oximeter will be used to measure oxygen levels and heart rates each minute. Your child will be asked about whether they feel tired or out of breath.

  • Infant PFTs: Some hospitals are able to do PFTs on babies. This testing can measure spirometry and lung volumes.

This information is for educational purposes only. It should not be used as a substitute for the medical advice of one’s healthcare provider.