Exhaled nitric oxide and airway caliber during exercise-induced bronchoconstriction

Data on the relationship between exercise-induced bronchoconstriction (EIB) and exhaled nitric oxide (NO) in adult patients with asthma are controversial. It is unclear whether endogenous NO may act as either a protective or stimulatory factor in the airway response to exercise or whether changes in exhaled NO simply reflect acute narrowing of the airway. The aim of this study was to assess the changes in the fraction of exhaled nitric oxide (FENO) before and after exercise challenge in patients with asthma and to analyze the relationship between FENO and airway obstruction. Twenty-five non-smoking, steroid-naive, atopic, adult patients with mild persistent asthma and 12 non-smoking, nonatopic, healthy subjects (control group) performed an exercise challenge on a cycloergometer, with monitored ventilation. FEV1 and FENO were measured at baseline and 1, 5,10,15 and 20 minutes after the exercise challenge. Eleven of the asthmatic patients had exercise-induced bronchoconstriction (EIB group) and the remaining 14 did not (non-EIB group). Baseline FENO was higher in the EIB and non-EIB asthmatic groups than in the control group. In the EIB group, FENO was significantly lower 5, 10 and 15 minutes after exercise, and the changes in FENO correlated with variation in FEV1 10 and 15 min after exercise. A significant correlation between baseline FENO and maximal post-exercise decrease in FEV1, was found in asthmatic patients (EIB group). In conclusion, exhaled nitric oxide levels transiently decrease during exercise-induced bronchoconstriction in adult patients with asthma. Baseline FENO might predict the airway obstruction resulting after exercise.