Patient Information Leaflet

Fractional exhaled nitric oxide (FeNO) test

What is a fractional exhaled nitric oxide (FeNO) test?

A fractional exhaled nitric oxide test is a simple test to see how much nitric oxide is in your breath. It’s often called a FeNO (“fee-no”) test for short. The FeNO test measures inflammation in your airways.

Nitric oxide (NO) is found in the atmosphere and is higher in areas with air pollution. It is also produced in the body, especially if there is inflammation. A higher level of nitric oxide measured in your breath may be a sign of Asthma.

Before your appointment

Before you have the test, there are a few things that you should try to avoid to
ensure that the test is effective:

  • Do not undertake strenuous exercise or exert yourself at least one hour before your test
  • Do not smoke for at least one hour before the test
  • Avoid drinking hot drinks, caffeine, and alcohol at least one hour before the test
  • Avoid eating nitrate rich food for at least three hours before the test. Nitrate rich foods include green leafy vegetables (celery, leek, lettuce, and spinach) and beetroot

You can take your regular medications as normal before the test. Ensure that the nurse is aware of any medication that has been taken beforehand or if any of the activities above have taken place prior to the test.

During your appointment

The test will be conducted by a nurse who will explain the process to you and help to answer any questions you have during your appointment. You will be asked to breathe in deeply, with your mouth open, and then breathe out into a plastic mouthpiece or a cardboard tube attached to a monitor, little by little until your lungs are empty. The breath out will normally take 10 seconds.

You may have to do the same measurement up to 3 times.

Special requirements

All of our patient leaflets are available in large print formats.

If you require additional help or have other accessibility needs, please contact us on 01306 735459