Hyperventilation during bronchial challenges in asthmatics: reproducibility and assessment of contributing factors

AbstractAmong asthmatics, the ventilatory response is heterogeneous during bronchial challenge. This study aimed to investigate the reproducibility of the response and to assess possible causes for hyperventilation.Repeated bronchial histamine and methacholine challenges (HiChMeCh) were performed in 10 asthmatic adolescents. Ventilation was monitored by respiratory inductive plethysmography (RIP), in order to minimally affect the spontaneous breathing pattern. FEV1 and the volume of trapped gas (measured as the volume of air mobilized by five maximal breaths after a multiple breath nitrogen washout to 2% N2), were used to assess mainly central and peripheral airways obstruction, respectively.When FEV1 had decreased by at least 20%, mean inspiratory flow (VTITI) increased by 21% and minute ventilation (V′I) by 21% and 23% during HiCh and MeCh, respectively (both P