Objective: To determine the relationship between nasal nitric oxide (nNO) concentration and its influence on olfactory function.
Setting: Tertiary otolaryngology care centre.
Participants: Sixty-four patients suffering from chronic rhinosinusitis and 20 healthy subjects participated.
Study design: Prospective study.
Outcome measures: The nNO concentration was measured by chemiluminescence and olfactory thresholds were measured with the phenyl ethanol threshold of the Sniffin' Sticks. In chronic rhinosinusitis patients this measure was done preoperatively and 3 months after endoscopic sinus surgery.
Results: Healthy subjects had significantly higher nNO concentrations and better olfactory thresholds compared to the chronic rhinosinusitis patients, both before and after those had undergone sinus surgery. Olfactory thresholds and nNO concentrations remained unchanged after surgery in the chronic rhinosinusitis group. In the chronic rhinosinusitis group, nNO concentrations correlated positively with the olfactory threshold preoperatively (P < 0.0001) and 3 months after surgery (P < 0.05). In the control group, nNO production did not correlate with the olfactory thresholds (P > 0.05).
Conclusion: Olfactory function and nNO concentration correlate in chronic rhinosinusitis patients but not in healthy subjects. This suggests that both parameters do rather not directly influence each other but it might be the inflammatory processes found in chronic rhinosinusitis that affects olfaction and nNO. Nasal nitric oxide produced by the paranasal sinuses seems not to directly influence olfactory function.