Background: Lower exercise tolerance is an important component of asthma and the possible effects of non-invasive ventilation 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 minimum PEEP at 1 cmH₂O 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 significant 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).