A decrease in FENO is most consistent with which finding?

A decrease in FENO is most consistent with which finding?

• A. Increased airway inflammation
• B. Decreased airway inflammation
• C. No change in airway inflammation
• D. Airway edema only

Answer: (A)

FENO reflects nitric oxide produced by the airway epithelium in response to eosinophilic inflammation. When airway inflammation decreases, the epithelial cells generate less nitric oxide, so the exhaled level falls. Therefore, a decrease in FENO is best explained by a reduction in airway inflammation, such as after effective anti-inflammatory therapy. Increased airway inflammation would raise FENO, not lower it; no change in inflammation would leave FENO unchanged; and edema alone doesn’t directly alter nitric oxide production, so it wouldn’t explain a decrease in FENO.

FENO reflects nitric oxide produced by the airway epithelium in response to eosinophilic inflammation. When airway inflammation decreases, the epithelial cells generate less nitric oxide, so the exhaled level falls. Therefore, a decrease in FENO is best explained by a reduction in airway inflammation, such as after effective anti-inflammatory therapy. Increased airway inflammation would raise FENO, not lower it; no change in inflammation would leave FENO unchanged; and edema alone doesn’t directly alter nitric oxide production, so it wouldn’t explain a decrease in FENO.