Update on the use of nitric oxide as a noninvasive measure of airways inflammation.

Nitric oxide levels may reflect the inflammatory status of both the upper and lower airways. Measurement of exhaled bronchial nitric oxide is a useful, non-invasive tool in the diagnosis and management of eosinophilic asthma. Nasal nitric oxide may be normal, raised or lowered in disease states; however measurement may be a useful tool in the diagnosis and management of patients with chronic rhinosinusitis, nasal polyps, and cystic fibrosis, as well as in the diagnosis of primary ciliary dyskinesia. Further research is aimed at investigating the role of nitric oxide in allergic rhinitis and nasal congestion. Measuring both bronchial and nasal nitric oxide may assist the combined management of upper and lower airways.