Exhaled nitric oxide as a simple assessment of airway hyperresponsiveness in bronchial asthma and chronic cough patients

Exhaled nitric oxide (NO) has been suggested to be a marker of airway inflammation. The aim of this study was to evaluate the role of exhaled NO in bronchial asthma and chronic cough patients to predict bronchial hyperresponsiveness (BHR). We measured the exhaled NO concentration using the chemiluminescence method in 52 asthma patients (group I consisting of 24 without prior inhaled corticosteroid (ICS) use, and group II consisting of 28 previously on ICS and 16 chronic cough patients in group III). In addition to regular examinations, spirometry and methacholine inhalation tests using the Astograph were done. In group I, a significantly negative correlation was observed regarding the exhaled NO concentration with FEV1/FVC%, V-50, and BHR that was assessed as Dmin and PD35-Grs, and a positive correlation with peripheral blood eosinophils. In group III, a significantly negative correlation was seen regarding the exhaled NO concentration with BHR. We thus concluded that measuring exhaled NO concentration appears to be a useful noninvasive method to predict the BHR, airway obstruction, and inflammation in asthma and chronic cough patients.