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Exhaled nitric oxide test

Patient information A-Z

An exhaled nitric oxide meter and breathing handle being used by a person for performing an exhaled nitric oxide measurement.
Lung function test equipment

About the exhaled nitric oxide test

Why am I having an exhaled nitric oxide test and what is it?

The exhaled nitric oxide test is designed to measure the amount of inflammation in your airways. Your doctor has asked for you to have this test to either help monitor your asthma or assist with diagnosis of asthma if you are a new patient.

What does an exhaled nitric oxide test involve?

The test involves breathing into a tube on a small hand held device. First you will be asked to blow out into the room and then take a big breath in on the tube. Once your lungs are full, we will ask you to blow down the tube at a set speed for about 10 seconds. The device will measure how much inflammation is in your airways from markers in your exhaled breath.

About your appointment


  • Please take all medication including inhalers as normal (unless otherwise stated in your appointment letter).
  • The test will last approximately 10 minutes.

If you cannot attend your appointment

If you need to rearrange your appointment, or no longer need an appointment, please call us on 01223 217065 at the earliest opportunity. Reallocating appointments helps us to reduce waiting times.

What if I am unwell prior to the appointment?

Please call us on 01223 217065 if you:

  • have had a recent chest infection, or
  • are currently on a course of antibiotics, or
  • have just finished a course of antibiotics for your chest

It may be inappropriate to perform the test at this time and your appointment may be rescheduled.

If you are unwell, please inform us at the earliest opportunity. If you are unwell on the day of the appointment, please still call and let us know as this will allow us to rearrange your appointment for a more suitable time.

Who will be present at my appointment?

Cambridge University Hospitals NHS Trust (CUH) is a teaching hospital and so there may be occasions when a student or staff member accompanies your physiologist. We will, however, always seek your permission first.


You will be asked for consent to perform tests during your appointment. You will also have an opportunity to ask questions before you give consent. In the unlikely event there are risks related to the test, these will be discussed with you before the test starts.

Test results

After your appointment, your test results will be sent to your referring consultant, who will then contact you to discuss the results and the next steps in your treatment.


Due to the nature of the tests and the exertion required, some patients may feel dizzy or faint during testing. Coughing is also common. Serious complications are rare and risks will be kept to a minimum by your physiologist.

Potential but rare complications

  • Airway narrowing in those with sensitive airways.
  • Heart attack in patients with previous cardiac disease.
  • Sudden changes in blood pressure.
  • Stroke.
  • Collapsed lung.
  • Retinal detachment.

These complications are very rare; you will be questioned by your physiologist prior to the test to determine whether you are at increased risk.

Contacts/ Further information

If you are unclear about any of the information provided in this leaflet or have any other questions then please do not hesitate to contact the Lung Function Department at Addenbrooke’s Hospital on 01223 217065 or Clinic 2A on 01223 216645.

Our opening hours are Monday to Friday from 08:30 to 16:30.

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

Other formats

Help accessing this information in other formats is available. To find out more about the services we provide, please visit our patient information help page (see link below) or telephone 01223 256998.

Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151