TY - JOUR T1 - Bronchial hyperresponsiveness is associated with both increased methacholine-induced reduction in airway volume and reduced baseline airway volume JF - European Respiratory Journal JO - Eur Respir J VL - 44 IS - Suppl 58 SP - P2181 AU - Laurent Plantier Y1 - 2014/09/01 UR - http://erj.ersjournals.com/content/44/Suppl_58/P2181.abstract N2 - Background. Airflow reduction in response to bronchoconstrictory stimuli, or bronchial hypersponsiveness (BHR), is a central feature of asthma. However, whether BHR indeed involves excessive reductions in airway caliber, and thus airway volume, was never demonstrated in humans. In addition, whether anatomical determinants predispose to BHR is a matter of debate.Methods. 75 patients with normal baseline spirometry and referred for plethysmographic measurement of lung volumes and methacholine (Mch) challenge because of chronic cough, dyspnea, or wheezing, were included. Airway volume (Vaw) was determined before and after Mch challenge by volumetric capnography using the equal area (Fletcher's) method, and expressed relative to total lung capacity (TLC). BHR was defined by a decrease of FEV1≥20% after exposure to up to 1.6 mg Mch. FEV1/Mch and Vaw/Mch dose response slopes were calculated. Data were analysed with Student's t-test and Spearman's rank order correlation.Results. Patients with BHR had lower baseline Vaw/TLC in comparison with patients without BHR (31.8+/-8 ml/l, N=22 vs 37.8+/-11.7 ml/l, N=53, p=0.047). Patients with BHR also showed considerably higher Vaw reduction relative to the Mch dose (44.3+/-62 %/mg vs 2+/-9 %/mg, p=0.001). Vaw/Mch correlated with FEV1/ Mch (Rho=0.567, p=0.0001).Discussion. This report demonstrates for the first time that patients with BHR exhibited higher Mch-induced reduction in airway volume, i.e. bronchoconstriction. It remains to define whether lower baseline airway volume in patients with BHR relates to underlying disease or anatomical predisposition. ER -