Exercise-induced Bronchodilation Equalizes Exercise Ventilatory Mechanics despite Variable Baseline Airway Function in Asthma

PURPOSE: We quantified the magnitude of exercise-induced bronchodilation in adult asthmatics under conditions of narrowed and dilated airways. We then assessed the effect of the bronchodilation on ventilatory capacity and the extent of ventilatory limitation during exercise. METHODS: Eleven asthmatics completed three exercise bouts on a cycle ergometer. Exercise was preceded by no treatment (trial(CON)), inhaled β(2)-agonist (trial(BD)), or a eucapnic voluntary hyperpnea challenge (trial(BC)). Maximal expiratory flow-volume maneuvers (MEFV) were performed before and within 40 seconds of exercise cessation. Exercise tidal flow-volume loops were placed within the pre- and post-exercise MEFV curve and used to determine expiratory flow-limitation (EFL) and maximum ventilatory capacity ([Formula: see text]). RESULTS: Pre-exercise airway function was different among the trials (forced expiratory volume 1 second [FEV(1)] during trial(CON), trial(BD), and trial(BC) = 3.3 ± 0.8, 3.8 ± 0.8, and 2.9 ± 0.8 L, respectively; P