Analysis of small airway function in chronic cough patients with positive results in bronchial provocation

Objective To analyze the characteristics of small/large airway function and eosinophilic inflammation in adult patients with chronic cough and bronchial hyperresponsiveness (BHR), and to explore if that small airway dysfunction was associated with large airway function, inflammation and BHR. Methods Chronic cough patients (16-80 years) with positive methacholine provocation reactivity and spirometric results were enrolled in this single-center cross-sectional study.Provocation reactivity, spirometric results, forced mid-expiratory flow at 25% to 75% of forced vital capacity (FEF25%-75%) and fractional exhaled nitric oxide (FeNO) were collected.The difference between normal small airway function group and dysfunctional group in forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC, peak expiratory flow (PEF), FEV1 after provocation, cumulative dose of methacholine provoking a 20% decrease in FEV1 from baseline value (PD20-FEV1) and FeNO was investigated.Correlation between small airway dysfunction and the above clinical features were also analyzed. Results Totally 96 patients were enrolled.76.04% of patients with chronic cough and BHR had small airway dysfunction.FEV1, FEV1/FVC and PEF decreased significantly in group with small airway dysfunction, companied with more serious increase of BHR.FVC and FeNO had no significant correlation with small airway function. Conclusions Small airway dysfunction may be involved in the development of BHR in patients with chronic cough, independently of airway eosinophilic inflammation.The assessment of small airway function combined with eosinophilic analysis could be considered in prediction of BHR. Key words: Asthma, bronchial; Fractional exhaled nitric oxide; Small airways function; Bronchial provocation; cough