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Background Lower exercise tolerance is an important component of asthma and the possible effects of non-invasive ven-tilation on exercise capacity in individuals with severe therapy-resistant asthma(STRA)are unknown.This study aimed to evaluate the immediate effect of continuous positive airway pressure(CPAP)on exercise tolerance in children with STRA.Methods We performed a controlled,randomized,crossover clinical trial including subjects aged 6 to 18 years old diagnosed with STRA.Clinical,anthropometric and lung function data were collected.The participants in the intervention group(IG)used CPAP(PEEP 10cmH2O and FiO2 0.21)for a period of 40 min.Subjects in the control group(CG)used CPAP with mini-mum PEEP at 1 cmH20 also for 40 min.Afterwards,subjects from both groups underwent cardiopulmonary exercise testing(CPET).After a 15-day washout period,on a subsequent visit,subjects participated in the opposite group to the initial one.Results Thirteen subjects with a mean age of 12.30±1.7 years were included.The variables of peak expiratory flow(PEF)and forced expiratory volume in the first second(FEV1)before using CPAP and after performing CPET did not show sig-nificant differences.Regarding CPET results,there was no significant difference(P=0.59)between groups at peak exercise for oxygen consumption—VO2(CG:33.4±6.3 and IG:34.5±5.9,mL kg-1 min-1).However,the IG(12.4±2.1)presented a total test time(min)significantly(P=0.01)longer than the CG(11.5±1.3).Conclusion The results suggest that the use of CPAP before physical exercise increases exercise duration in children and adolescents with STRA.