Measurement of Exhaled Nitric Oxide

Section: Miscellaneous
Effective Date: July 01, 2018
Revised Date: November 14, 2019
Last Reviewed: November 14, 2019


Nitric oxide (NO) is an endogenous messenger and inflammatory mediator that is widespread in the human body. While the role of NO in asthma pathogenesis is still under investigation, individuals with eosinophilic asthma have been found to have high levels of fractional exhaled nitric oxide (FeNO), which decreases with treatment with corticosteroids.

In the gas phase, NO is fairly stable, permitting its measurement in exhaled air. FeNO is typically measured during single breath exhalations. First, the subject inspires NO-free air via a mouthpiece until total lung capacity is achieved, followed immediately by exhalation through the mouthpiece into the measuring device.


Measurement of exhaled NO (i.e. FeNO) may be considered medically necessary in the management of individuals with an established diagnosis of eosinophilic asthma.

Measurement of exhaled NO (i.e. FeNO) for the initial diagnosis of asthma and for all other respiratory disorders is considered experimental/investigational, and therefore, non-covered because the safety and/or effectiveness of this service cannot be established by the available published peer-reviewed literature.

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