Fractional Exhaled Nitric Oxide Test

A fractional exhaled nitric oxide (FeNO) level test can help diagnose and manage asthma. It measures the amount of nitric oxide that is exhaled from a breath. Increased levels of nitric oxide are associated with swelling of lung airways. This test can be used to determine whether someone being treated for asthma is responding well to certain medications.

What Is Nitric Oxide?

Nitric oxide is a gas produced by cells involved in the inflammation process associated with asthma.

How Is It Done?

The FeNO test takes less than five minutes for a person to complete and is similar to another breathing test called the pulmonary function test or spirometry. The test is done using a portable device that measures the level of nitric oxide exhaled from your lungs. There will be a technician helping and guiding you through the procedure.

What Do the FeNO Results Mean?

The measurements are used to determine:

• If you should take inhaled corticosteriods to manage your asthma.
• If you are already taking inhaled corticosteroids, the results will show how effective your medications are.
• If you are following your asthma treatment plan.
• If you should modify your therapy plan; you might be asked to do the test three to four times a year.
• In some cases, the results are used to diagnose asthma, along with results of other diagnostic tests.

A higher than normal level of nitric oxide means that there is inflammation (swelling) in the lining of the airways, or could mean that you have allergic asthma. Inflammation typically responds well to corticosteroid therapy.