Acute Effects of Inspiratory Muscle Training with Different Loads on Peripheral Muscle Oxygenation Kinetics and Autonomic Response in Patients with COPD: A Protocol for a Randomized Crossover Study.

Background: Chronic obstructive pulmonary disease (COPD) leads to inspiratory muscle weakness, which may contribute to an altered cardiovascular response during the respiratory cycle. In this context, inspiratory muscle training (IMT) emerges as one of the available tools for the treatment and monitoring of patients with respiratory muscle dysfunction. Methods: This is a randomized crossover study, with blinding of both the evaluator and the researcher responsible for statistical analysis. The study will evaluate the acute effects of IMT on peripheral muscle metabolism and the autonomic response in 30 patients with COPD. The primary outcomes will be peripheral muscle oxygenation kinetics, assessed by near-infrared spectroscopy (NIRS), and autonomic response, assessed through heart rate variability (HRV). Participants will be randomly assigned to undergo three different intervention conditions at separate times, with a minimum interval of 48 hours between each session: IMT-S (Strength), aimed at improving inspiratory muscle strength; IMT-E (Endurance), focused on enhancing inspiratory muscle endurance; and Sham, consisting of a Sham IMT intervention. For statistical analysis, continuous variables will be presented as mean ± standard deviation, and data normality will be assessed using histograms and the Shapiro-Wilk test. All analyses will follow the intention-to-treat principle. In cases of missing data due to dropouts or absence in crossover sessions, participants with incomplete data will be retained in the analysis, assuming that data are missing at random. Between-intervention differences will be analyzed using mixed linear models with Bonferroni adjustment for multiple comparisons. The level of statistical significance will be set at 0.05. Conclusion: This study may help to better understand the effects of IMT performed at different loads on peripheral muscle oxygenation behavior, as well on the autonomic response in patients with COPD. These findings may improve the understanding of the physiological impacts of this therapy and support its application in pulmonary rehabilitation programs. Trial Registration: Clinical Trial Registry NCT06827379.