Exhaled Nitric Oxide


Measurement of fractional exhaled nitric oxide (FENO) is a noninvasive, safe,  method of quantifying airway inflammation. 

FENO in asthma may help  make the diagnosis, monitor compliance with prescribed medications, and predicting pending exacerbations.

FENO is not diagnostic for asthma, nor does a normal FENO measurement exclude the diagnosis of asthma. 

FENO does have utility in predicting steroid responsiveness.

The FENO test use includes:

Assessment of cough, wheezing, and dyspnea

Identifying eosinophilic asthma

Assessing the potential response to anti-inflammatory agents, notably inhaled corticosteroids (ICS)

A baseline FENO should be established during a period of clinical stability for subsequent monitoring of chronic persistent asthma.

It is used to guide changes in anti-inflammatory medications, to assist in the evaluation of adherence to anti-inflammatory medications, and to assess whether airway inflammation is 

contributing to poor asthma control.

FENO measurements have been shown to be increased by nitrate-containing foods such as lettuce.

 FENO measurements may be transiently lowered by drinking coffee or water and smoking cigarettes. 

FENO measurements  should be done after patients refrain from smoking and the ingestion of food or beverages for 1 hour.

Upper and lower respiratory tract viral infections may increase levels of FENO.

Instruments for the measurement of exhaled nitric oxide are available.

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