Efetividade e segurança do treinamento muscular inspiratório na asma: ensaio clínico randomizado

Abstract

Background: Asthma is one of the most prevalent chronic diseases in the world and is considered a serious public health problem. Asthma treatment is based on achieving and maintaining adequate disease control. However, in "real life", suboptimal control of asthma is frequent. In this sense, inspiratory muscle training (IMT) may be a good alternative to complement traditional drug therapy. Objective: To evaluate the effectiveness and safety of the IMT in people with asthma. Methods: This was a double-blind randomized controlled trial. The sample consisted of 29 people with asthma divided into two groups: 14 participants in the low load group (L15%) and 15 in the moderate load group (L50%). IMT was performed 5 days a week for 6 weeks with POWERbreathe® device. The sessions consisted of 30 repetitions twice a day. The L15% group trained with a load of 15% of maximal inspiratory pressure (MIP), while L50% group trained with 50% of MIP. Initially, the participants were submitted to pulmonary function assessments. Then, the Asthma Quality of Life Questionnaire (AQLQ) and Asthma Control Questionnaire (ACQ) were applied. Respiratory muscle strength was obtained by MIP and by maximal expiratory pressure (MEP). The Borg CR10 scale and the distance walked in six-minute walk test (6MWD) were used to assess degree of dyspnea and functional capacity, respectively. Finally, a training diary was used to record adverse events and IMT adherence. Assessments were performed at baseline, after 6 weeks of training and six weeks after cessation of training. Results: After 6 weeks of IMT, MIP increased 20.7 cmH2O and 33.1 cmH2O in the L15% and L50% groups, respectively. MEP showed a gain of 10.4 cmH2O in the L50% group and 8.1 cmH2O in the L15% group. AQLQ showed a probable clinical improvement (above 0.5) in two domains (limitation of activity and emotional function) in the L15% group and in all domains in the L50% group. In the L50% group, there was a potential reduction of 1.13 and 1.42 points on the Borg CR10 scale before and after the 6MWT, respectively. At the end of the IMT, there was no difference in asthma control, 6MWD and pulmonary function for both groups. During the training period, no volunteers were hospitalized or admitted to an emergency department, nor was there an asthmatic crisis due to IMT. Adherence to IMT was not analyzed, since the majority of participants did not record the sessions performed in the training diary. Six weeks after cessation of IMT, only 31% of participants returned for evaluation. Thus, it was not possible to include the effects of training reversibility on our results. Conclusions: In individuals with asthma, home IMT with a low and moderate load proved to be safe and effective in increasing respiratory muscle strength and improving quality of life. In addition, moderate-load training reduced the level of dyspnea.