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Pulmonary Function Test: Exhaled Nitric Oxide (eNO)

What is an Exhaled Nitric Oxide (eNO) Test?

The Division of Pulmonary Medicine at Cincinnati Children's performs exhaled nitric oxide (eNO) tests.

Exhaled nitric oxide (eNO) is used to measure inflammation in the airway. Nitric oxide (NO) is a gas that is found in the lungs and is produced when we breathe.

eNO levels may be higher in children who have asthma. When airways are inflamed or swollen, higher levels of NO are made.

This test can help your doctor confirm a diagnosis of asthma. eNO levels are sometimes measured to see how well a treatment or medication is working for your child.

Test Procedure

eNO is measured by having your child place his or her mouth around a single use, disposable, filterable mouthpiece. Your child will be asked to inhale deeply and exhale slowly through the mouthpiece.

Time of the Test

The test takes about two minutes. With explanation and practice, testing may take up to 10 minutes.

Preparing Your Child for the Test

Your child should not eat or drink anything for one hour before testing. Certain foods and drinks may be high in nitrates or preservatives and can elevate eNO levels.

Possible Side Effects

There are no side effects and your child may resume normal activities after testing.

Last Updated 05/2022

Reviewed By Anna Baumer, RRT