The clinical value of changes in small airway function in patients with chronic cough

Objective To evaluate the clinical value of small airway function indexes in lung function in the differential diagnosis of patients with chronic cough. Methods One hundred and nine patients with chronic cough were managed with conventional pulmonary function testing and bronchial provocation test. The difference of small airway function between bronchial provocation test positive and negative indicators, and the difference of lung function and the positive rate of bronchial provocation test between small airway dysfunction and normal small airway function was observed. Results Sixty cases in 109 patients had positive bronchial provocation test and 49 eases were negative. Peak expiratory flow (PEF),maximal midexpiratory flow rate (MMEF)75/25, forced expiratory flow of vital capacity (FEF)25, FEF50,FEF75 were lower than those in negative eases (P<0.05 ), ventilatory capacity, forced vital capacity( FVC ),forced expiratory volume in one second (FEV_1, FEV_1/FVC had no significant differences. Forty-eight eases had small airway dysfunction. There were 39 cases with positive bronchial provocation test, and the positiverate was 81.2%. In 61 cases without small airway function, there were 21 cases with positive bronchial provocation test(34.4%). There was significant difference in positive rate of bronchial provocation test between them (P <0.01). Conclusions Small airway function indexes in lung function can predict airway hyperresponsiveness. In a large number of primary hospital where bronchial provocation test can not carry out,it helps to identify patients with early cough variance asthma. In particular, it is more important in young patients with small airway disease. Key words: Cough; Airway resistance; Respiratory function tests; Bronchial provocation tests