exhaled nitric oxide
Pronunciation: FEE-no
Also written as: FeNO — fractional exhaled nitric oxide
A biomarker of eosinophilic airway inflammation measured in parts per billion in exhaled breath, used to guide diagnosis and treatment of pediatric asthma.
Full Definition
Exhaled nitric oxide (eNO or FeNO—fractional exhaled nitric oxide) is produced by airway epithelial cells and eosinophils under the influence of inflammatory cytokines; elevated levels indicate type 2 (eosinophilic) airway inflammation. It is measured non-invasively using a standardized exhalation technique at a controlled flow rate of 50 mL/s and expressed in parts per billion (ppb). In pediatric asthma management, FeNO levels guide initiation and titration of inhaled corticosteroid therapy. Editors must use 'FeNO' (not 'FENO,' 'eNO,' or 'ENO') as the preferred abbreviation in most current guidelines, and values should be reported in ppb without a space before the unit symbol. The device generating the measurement is a chemiluminescence or electrochemical analyzer.
Usage
Usage note: Preferred abbreviation is 'FeNO' per ATS guidelines. Values are expressed in ppb (no space). Do not use 'FENO' in all capitals or 'eNO' without clarifying the abbreviation at first use.
In Context
- "A FeNO level of 42 ppb in a child with recurrent cough supported the diagnosis of eosinophilic asthma and prompted initiation of inhaled corticosteroid therapy." — Clinical consultation letter editing
- "The editor standardized all instances of 'FENO' and 'eNO' to 'FeNO' in accordance with the journal's stated adherence to ATS terminology guidelines." — Journal manuscript copy-editing