Nasal Nitric Oxide in the Upper Airway Inflammatory Diseases

ABSTRACT

Exhaled nitric oxide (eNO) from the lower respiratory tract is used commonly in diagnosis and treatment monitoring of asthma patients. However, nasal nitric oxide (nNO) has not been widely used in patients with upper airway inflammatory diseases due to its lack of standardized measurement methods. Nasal nitric oxide is produced mainly by the paranasal sinus mucosa and partially by the nasal mucosa and increases with inflammation. Nasal nitric oxide not only locally supports the defensive mechanism of the upper respiratory tract, but also remotely controls pulmonary function by acting as an aerocrine. Nasal NO can be affected by various physiologic and pathologic factors of the upper respiratory tract. This article will review the origin of nNO, its function, various measurement methods, and difference in presentation among upper respiratory tract inflammatory diseases such as allergic rhinitis, upper respiratory tract infection, nasal polyp, rhinosinusitis, primary ciliary dyskinesia, cystic fibrosis, Young’s syndrome, diffuse panbronchiolitis, empty nose syndrome, and obstructive sleep apnea. Future studies should identify the mechanism of action of nNO in various upper respiratory tract inflammatory diseases and obtain highly reproducible normal values of nNO based on a standardized measurement method with a deeper understanding of factors affecting nNO. Then, nNO will be useful for more rapid and simpler diagnosis of various upper respiratory tract diseases and for monitoring their treatment.