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What is the exhaled nitric oxide measurement test?

The exhaled nitric oxygen test (FeNO) is used to indirectly measure the degree of inflammation of the airways.  

What is it for?

It evaluates the fraction of exhaled nitric oxide; a gas produced by the epithelial cells that cover the interior of the airways and is useful for:  

  • Detecting inflammation of the airways.
  • Diagnosing bronchial asthma.
  • Monitoring the response to anti-inflammatory treatment.   
  • Evaluating the effectiveness of the treatment.  
  • Predicting exacerbations.

How is it done?

It is a simple technique in which the patient gently blows through a mouthpiece and follows the instructions of the member of staff responsible for carrying out the test.

How should the patient be prepared?

In order to perform the test, the patient should have a light breakfast and take their usual medication.   

Who will carry out the test?

The test is carried out by nursing staff, technicians, or physiotherapists familiarised with the test and that have been previously trained for it.

Who interprets the results?

The pulmonologist is responsible for evaluating the results of the test and preparing the corresponding report.   

What sensations might there be during the test?

There may be cough and a very slight sensation of breathlessness. The patient is accompanied by health staff during the whole process.

Substantiated information by:

Jorge Moisés Lafuente
Xavier Alsina Restoy

Published: 23 May 2019
Updated: 23 May 2019


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