Capacidade de exercício e utilização de pressão positiva contínua nas vias aéreas (CPAP) em crianças e adolescentes com asma grave resistente à terapia

Abstract

Introduction: Asthma is a chronic inflammatory disease of the lower airways, characterized by airflow limitation and bronchial hyperresponsiveness. A subgroup of children with severe asthma does not respond adequately to treatment, and is classified as severe therapy-resistant asthma (STRA). Because of factors such as recurrent wheezing, coughing, shortness of breath, continued use of medications, exercise-induced bronchoconstriction (EIB), and dynamic pulmonary hyperinflation, these patients may have limitations in exercise capacity. Objective: To evaluate exercise capacity and the effect of continuous positive airway pressure (CPAP) on exercise tolerance in children and adolescents with STRA. Methods: This thesis is divided into two articles. Both studies included children and adolescents diagnosed with STRA, aged between six and 18 years. Article 1 consists of a cross-sectional study. Pulmonary function test (spirometry), cardiopulmonary exercise test (CPET) and EIB test were performed. The association between variables was evaluated. Article 2 is a randomized controlled clinical trial with crossover. Participants used, in a random order, CPAP (PEEP 10cmH2O and FiO2 0.21) or placebo (control - CPAP with minimum PEEP), both for a period of 40 minutes. After each intervention, the patients underwent CPET. At a subsequent visit, after a washout period, the patients participated in the procedure opposite to the initial one. All tests followed international recommendations. Results: Study 1 included 24 patients with STRA and mean age of 11.5±2.6 years. The mean forced expiratory volume in the first second (FEV1) was 91.3±9.2%. EIB occurred in 54.2% of the patients. At the CPET, the maximum oxygen consumption (VO2) was 34.1±7.8 mL.kg-1.min-1. When correlating the CPET and spirometry variables, we found a significant correlation between the ventilatory reserve and FEV1 (r=0.57, p=0.003). Likewise, there was a significant correlation between CPET and the percent of FEV1 fall in the EIB test, both for VEVO2 (r=0.47, p=0.02) and for VEVCO2 (r=0.46; p=0.02). Patients with FEV1 <80% presented lower ventilatory reserve (p=0.009). In addition, resting heart rate correlated with CPET peak exercise values, including VO2 (r=-0.40, p=0.04), VEVO2 (r=0.46, p=0.02) and VEVCO2 (r=0.48, p=0.01). In study 2, 13 patients with mean age of 12.30±1.7 years completed the protocols. The peak expiratory flow (PEF) and FEV1 before CPAP and after CPET did not show significant differences. There were no significant differences (p=0.5) between control and CPAP at peak exercise (VO2 in mL.kg-1.min-1 - CON: 33.4±6.3 and CPAP: 34.5±5.9). However, CPAP (12.7±2.1) had a significantly higher total test time (min) (p=0.01) than CON (11.8±1.5). Conclusion: Despite the low impairment of exercise capacity, children and adolescents with STRA and reduced pulmonary function have decreased ventilatory reserve. Different aspects of physical fitness are influenced by distinct determinants, including pulmonary function and EIB. In addition, the use of CPAP prior to physical exercise increases the total time of exercise in children and adolescents with STRA, but does not change the main performance markers on CPET.