Background: Allergic rhinitis is associated with nasal mucosal inflammation. Exhaled nitric oxide may be a useful marker of inflammation and has recently been shown to be increased in patients with asthma.
Objective: The purpose of this study was to determine whether exhaled levels of nitric oxide are increased with nasal breathing in patients with seasonal allergic rhinitis compared with nonatopic individuals and whether there is an increase with oral breathing consistent with lower respiratory inflammation in the absence of clinical asthma.
Methods: Nitric oxide levels in exhaled air were measured by chemiluminescence in 18 nonatopic volunteers and 32 patients with seasonal rhinitis. Measurements were made with both nasal and oral exhalation and orally after 10 seconds and 60 seconds of breath-holding. The detection limit was 1 part per billion (ppb).
Results: In control subjects nasal levels of nitric oxide in exhaled air (mean +/- SD, 24.7 +/- 9.2 ppb) were higher than those after oral exhalation (11.1 +/- 2.5 ppb, p less than 0.0001). Breath-holding significantly increased levels of nitric oxide in exhaled air in a time-dependent manner. Levels of exhaled nitric oxide were significantly higher for all measurements in patients with seasonal rhinitis, with levels without breath-holding of 35.4 +/- 11.3 ppb (p less than 0.001) in nasally exhaled air and 16.3 +/- 5.9 ppb (p less than 0.001) in orally exhaled air. Nasal levels were significantly higher than oral levels in subjects with rhinitis (p less than 0.0001).
Conclusions: The results indicate that exhaled nitric oxide may be a useful marker for nasal inflammation in patients with seasonal rhinitis and suggest that generalized airway inflammation may be present, even without clinical asthma, in such patients.