Bronchoconstriction-triggered Cough Is Impaired in Typical Asthmatics

Background and objective. Cough is an essential innate protective behavior, which is experienced by even healthy individuals. The mechanism of cough triggered by bronchoconstriction is not yet clear. The aim of this study was to investigate the relation between bronchoconstriction and cough caused by methacholine (Mch) inhalation in typical asthmatics and normal healthy subjects. Methods. We measured bronchial responsiveness to Mch and counted the number of coughs induced by Mch inhalation in 15 typical asthmatics and 20 normal subjects. Results. After inhalation of Mch at the concentration causing 20% or more decrease in forced expiratory volume in 1 second (FEV1) (PC20-FEV1), coughs were provoked in normal subjects (number of cough: 22.5/32 min, range: 3.3–45). Conversely, coughs were hardly provoked in typical asthmatics (median number of cough: 2/32 min, range: 0–4). Conclusions. Although typical asthmatics have increased airway responsiveness, their cough response to bronchoconstriction is impaired.