Bidirectional link between upper and lower airways in patients with allergic rhinitis

OBJECTIVE: Exhaled nitric oxide has been proposed as a noninvasive marker of eosinophilic airway inflammation in lower airways. The aim of the study was to investigate the impact of atopy, pollen exposure, and pharmacological treatment on NO production in lower airways of patients with allergic rhinitis. SUBJECTS AND METHODS: Measurements of exhaled NO were performed in 79 non-asthmatic subjects with seasonal allergic rhinitis outside and in pollen season, before and after pharmacological treatment, and in 54 healthy controls. RESULTS: Patients with allergic rhinitis had significantly higher levels of exhaled NO (18.3 ± 11.0 ppb) than healthy controls (13.0 ± 7.2 ppb) measured outside the pollen season (P = 0.0024). Increased exhaled NO levels were also found in patients with allergic rhinitis in the pollen season (27.0 ± 20.0 ppb) compared with the levels outside pollen season (P = 0.0001), before pharmacological treatment. In rhinitic patients treated by nasal corticosteroids and antihistamines in the pollen season, the levels of exhaled NO were significantly lower (17.0 ± 16.4 ppb; P = 0.045) than those before treatment. No difference was found in NO levels in rhinitic patients outside and in pollen season after pharmacological treatment. CONCLUSIONS: This study has shown the presence of eosinophilic airway inflammation in the lower airways in allergic rhinitis patients. A significant increase of exhaled NO after pollen exposure in rhinitic patients underlies the impact of inflammation on the upper respiratory tract. A bidirectional link between upper and lower airways is confirmed by a decrease in exhaled NO in the pollen season, almost to the starting levels, after application of topic corticosteroids and antihistamines.