Buffering airway acid decreases exhaled nitric oxide in asthma

Airway biochemistry modulates FENO levels. For example, nitrite is converted to NO in the airway, particularly the inflamed airway, by means of acid-based chemistry. Thus airway pH should be considered in interpreting clinical FENO values. In fact, PBS challenge testing integrates airway pH and FENO analysis, potentially improving the utility of FENO as a noninvasive test for the type and severity of asthmatic airway inflammation.