The purpose of this study is to verify the effects of continuous positive airway pressure (CPAP) on exercise capacity of children and adolescents with severe therapy-resistant asthma (STRA). A randomized, controlled, crossover clinical trial will be conducted. We expect the use of CPAP to increase exercise capacity in children and adolescents with STRA.

This project aims to verify the effects of continuous positive airway pressure (CPAP) on exercise capacity of children and adolescents with severe asthma therapy-resistant (STRA). A randomized, controlled, crossover clinical trial will be conducted. Children and adolescents between 6 and 18 years old, with a diagnosis of STRA, will be included in the study. Patients wil be recruited in the São Lucas Hospital (HSL) Asthma Outpatient Clinic of the Pontifical Catholic University of Rio Grande do Sul. Patients who accept to participate in the study will perform a medical consultation according to routine outpatient asthma clinic, anthropometric evaluation and pulmonary function tests. Afterwards, they will be randomized into control and intervention groups. Participants in the intervention group will use noninvasive ventilation (NIV) in CPAP mode with 10cmH2O of positive end-expiratory pressure (PEEP), fraction of inspired oxygen (FiO2) of 0.21, for a period of 40 minutes. Participants in the control group will use NIV (CPAP), with a minimum PEEP of 1cmH20 and a FiO2 of 0.21 also for 40 minutes. Afterwards, patients from both groups will perform a maximum cardiopulmonary exercise test (CPET). A sample size of 18 individuals to be included in the study was estimated. The variables studied will be maximal oxygen consumption and the anaerobic threshold (that measures exercise capacity), distance and time (to measure exercise tolerance), peripheral oxygen saturation, peak expiratory flow and the sensation of dyspnea at the end of the CPET.

Inclusion Criteria:

- Individuals with a clinical diagnosis of severe therapy-resistant asthma (STRA), of both sexes, aged between 6 and 18 years, who are under regular follow-up in the asthma outpatient clinic at São Lucas Hospital, PUCRS.

The criteria for the classification of STRA is based on the Global Initiative for Asthma (GINA) guidelines:

• Asthma requiring treatment in steps 4-5 of GINA (≥800 mg/day of budesonide or equivalent, associated with long-acting ß2-adrenergic agonist (LABA);
• Use of continuous oral corticoid or omalizumab, presenting uncontrolled disease;
• Uncontrolled disease characterized by: 1) persistent symptoms or asthma control test (ACT) <20 (> 3 months); 2) acute exacerbations (with intensive care unit admission, at least 2 hospitalizations, or 2 courses of oral corticoid over the last 12 months); Or 3) non-reversible obstruction of pulmonary function, even after corticoid use.

Exclusion Criteria:

- Subjects with cognitive/motor limitations or other chronic diseases (neurological diseases, cardiac anomalies, congenital or immunodeficiencies), which may compromise the evaluation of asthma, as well as the procedures proposed by the present study.

The randomization process will be kept confidential with a single investigator, not involved in data collection or recruitment, so that all other investigators involved will be blinded to the experimental groups throughout the study period.