Bronchodilator effect of deep inspiration and bronchoconstriction-triggered cough

We measured airway responsiveness to methacholine using partial and full flow-volume curves in 28 healthy adults. The expiratory flow at 40% above residual volume from the full forced vital capacity (MEF40) was obtained and the volume was used as the reference volume to determine the isovolume flow from the partial curve (PEF40). Coughs were counted for 32 min during and following the inhalation of methacholine at the provocative concentration which produced a 20% fall or more in FEV1from the post-saline value (PC20-FEV1). The bronchodilator effect of DI on bronchoconstriction induced by methacholine at the PC20-FEV1 concentration was expressed as the ratio of (MEF40-PEF40)/PEF40 (DI index).The number of coughs for 32 min during and following the inhalation of PC20-FEV1 concentration of methacholine was 39.3 ± 29.7 (mean ± SD)/32 min. The number of coughs during and following the inhalation was correlated with DI index (r = 0.57, p = 0.0015), but not with PC20-FEV1 or change in FEV1 or PEF40 by inhalation of the PC20-FEV1 concentration of methacholine.We found that methacholine-induced cough was associated with the bronchodilator effect of DI on methacholine induced-bronchoconstriction in normal subjects.Cough is a common and distressing symptom. Eosinophilic airway disorders such as bronchial asthma (BA), cough variant asthma (CVA) [1], eosinophilic bronchitis without asthma [2], and atopic cough (AC) [3] are important causes of chronic non-productive cough. As the mechanism of cough, at least the following two are considered: one is a cough caused by cough reflex hypersensitivity that is relevant to AC, gastroesophageal reflux disease (GERD) [4] and angiotensin-converting enzyme inhibitor-induced cough [5]. Another is a cough triggered by bronchoconstriction in such as CVA and BA, which responds to bronchodilator therapy [1,6].Capsaicin has achieved widespread use for measurement of cough reflex sensitivity [7]. Several studies suggest that capsaicin-induced cough