What is the Exhaled Nitric Oxide Test?

Has your doctor recommended that you undergo an exhaled nitric oxide test to determine if you could have asthma? This simple and painless process measures the amount of nitric oxide in your breath, which can be an indication that asthma exists.

What to Expect

If your doctor wants to perform an exhaled nitric oxide test on you either in his office,  at a hospital, or at an outpatient clinic, it can be helpful to understand the logistics of the procedure in advance. This is a noninvasive test that usually takes just a few minutes. You'll be directed to sit down and put the end of a tube into your mouth. Then you'll need to breathe in deeply for a few seconds, followed by a slow exhale. The device will measure your exhalation breath and determine the level of nitric oxide it contains. This process may be repeated several times in order to ensure an accurate reading. You may be also asked to perform other diagnostic tests at the same time.

Why Measure Nitric Oxide Levels?

Everyone has some level of nitric oxide in their breath when they exhale. But for some asthmatics, the related airway inflammation that occurs with this condition can result in a particularly high level. That's why this reading can very meaningful, especially when your doctor puts it together with other findings to identify important patterns that exist.

The Benefits of Using This Measurement

A study conducted by researchers from New Zealand that was published in the American Journal of Respiratory and Critical Care Medicine in 2004 confirmed the benefits of using exhaled nitric oxide measurements for asthma diagnosis. The scientists looked at the effects of exhaled nitric oxide testing on a group of close to 50 participants and discovered that the procedure is quick and easy to perform and the results are more accurate than some other common asthma diagnostic tests.

How to Prepare for an Exhaled Nitric Oxide Test

Before you undergo your own nitric oxide test, you might need to refrain from using your inhaler for an hour or two before your appointment. In addition, avoid exercise, food, drinks, toothpaste, and mouthwash right before the test as well since all of these things can affect the results. Just be sure to check with your insurance company to make sure they will cover the expense of this procedure.

Once the exhaled nitric test is complete if you do have asthma, expect your doctor to use the findings to develop an effective treatment strategy. She may also want to repeat the test periodically to make sure your asthma control medications are working effectively.




"Exhaled Nitric Oxide." National Jewish Health. Nationaljewish.org, n.d. Web 18 Sept. 2011.

"Nitric Oxide Test for Asthma." Mayo Clinic. Mayoclinic.com, 25 Feb. 2011. Web. 18 Sept. 2011.

Smith, Andrew et. al. "Diagnosing Asthma: Comparisons between Exhaled Nitric Oxide Measurements and Conventional Tests." The American Journal of Respiratory and Critical Care Medicine 169 (2004): 473-478. Web. 18 Sept. 2011.