Effects of different modalities of inspiratory muscle training as an add-on to conventional treatment of patients with chronic obstructive pulmonary disease (COPD): study protocol for a randomized controlled trial

BACKGROUND: Chronic obstructive pulmonary disease (COPD) leads to peripheral and respiratory muscle dysfunctions. Nowadays, inspiratory muscle training can be geared toward strength or endurance gains. This study aims to investigate the effects of an inspiratory muscle training (IMT) protocol using different therapeutic modalities to be implemented in pulmonary rehabilitation programs. The effects of IMT on exercise capacity were considered as the primary endpoint, and the effects of IMT on inspiratory muscle function, health-related quality of life, and daily physical activity level were considered as the secondary outcomes. METHODS: This study is a blinded-investigator randomized controlled clinical trial. Sixty subjects will be randomly allocated into three groups: (1) pulmonary rehabilitation (PR) associated with inspiratory muscle training without any load (PRWIMT), (2) PR associated with inspiratory muscle training with a linear load (PRIMTLL), and (3) PR associated with inspiratory muscle training with isocapnic voluntary hyperpnea (PRIMTIVH). The protocol will be performed 5 days a week (3 days with supervision) for 10 weeks. The study will assess anthropometric data, lung function, respiratory muscle strength, and functional capacity by the Incremental Shuttle Walking Test and the Six-Minute Walk Test, lung volumes during the submaximal endurance test, peripheral muscle strength of the upper and lower limbs, dyspnea, and quality of life related to health, before and after the training protocol. Normality will be tested using the Kolmogorov-Smirnov test, and variables will be compared by two-way analysis of variance. The significance level was set at p < 0.05. Ethics approval was obtained from the Institutional Ethics Committee in Research (1.663.411). The study results will be disseminated through presentation at specific scientific conferences and publication in peer-reviewed journals. DISCUSSION: The different IMT protocols used in our study will be able to guide respiratory therapists to understand and to include in conventional PR programs the most effective respiratory muscle training type in subjects with COPD. TRIAL REGISTRATION: Brazilian Clinical Trials Registry, RBR-94v6kd. Registered on 11 March 2017. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13063-019-3271-1) contains supplementary material, which is available to authorized users.