Abnormal respiratory system physiology Elevated fraction exhaled nitric oxide 2025-04-26T14:44:10Z Fraction exhaled nitric oxide elevated Fractional exhaled nitric oxide (FeNO) is a simple, reproducible, and a noninvasive marker of inflammation that may be elevated in diseases such as ssthma, eosinophilic pneumonia, COPD, pulmonary fibrosis, and interstitial lung disease. The fractional exhaled nitric oxide (FeNO) is elevated above the upper limit of normal. FeNO is an endogenous gaseous molecule which can be measured in the human breath test because of airway inflammation. It has been studied extensively as a marker of inflammation and has been incorporated into an algorithm for asthma management.