Chronic Obstructive Pulmonary Disease (COPD) is characterized by prolonged airflow obstruction due to tobacco exposure and environmental factors, making it one of the leading causes of mortality worldwide. In addition to respiratory complications, the disease promotes alterations in the cardiovascular system and peripheral muscle metabolism, contributing to exercise intolerance. In this context, Inspiratory Muscle Training (IMT) emerges as a strategy to enhance exercise tolerance and may influence the modulation of the metaboreflex during IMT application. However, the acute effects of IMT on the peripheral muscle metabolism of individuals with COPD remain poorly understood. Near-infrared spectroscopy (NIRS) is an effective method for analyzing the oxidative capacity of peripheral muscles.

To analyze the acute effect of IMT, with different pressure loads, on the peripheral oxygen desaturation rate in patients with COPD. METHODS: This crossover case series followed five individuals diagnosed with COPD. They underwent two IMT protocols: one strength-focused protocol (IMT-F), using 60% of the patient's maximal inspiratory pressure, and a Sham IMT protocol. During training, tissue oxygenation behavior was measured using near-infrared spectroscopy on the gastrocnemius muscle. The study included individuals capable of performing the IMT protocol and/or functional tests, who had no associated comorbidities such as psychiatric disorders, cognitive impairments, progressive neurological disorders, chronic pain, or an inability to follow commands. Participants who wished to discontinue their participation during the protocol execution or failed to comply with the protocol were excluded. Before participation, all individuals signed an informed consent form.

All participants showed greater desaturation in the IMT-F group compared to the Sham IMT group. The mean peripheral oxygen desaturation rate was higher in the IMT-F condition (-0.0184 ± 0.0210) compared to the Sham IMT (-0.0137 ± 0.0080). CONCLUSION: The results suggest a tendency for greater peripheral oxygen desaturation when patients are exposed to IMT-F. This condition may be explained by various physiological factors present in COPD patients that affect oxygenation and metabolic demand during intense effort. We believe that IMT-F requires more intense contractions of the inspiratory muscles, leading to increased oxygen consumption in this structure, indicating earlier activation of the metaboreflex. This mechanism redirects peripheral blood flow to the inspiratory muscles engaged in activity, potentially being a key factor in the reduction of peripheral tissue oxygenation during this type of training.

This study may contribute to a better understanding of the acute effects of IMT on peripheral tissue oxygenation behavior in COPD patients and may serve as a guide for the development of more effective respiratory rehabilitation protocols for these individuals.