Obstructive sleep apnea reduces functional capacity and impairs cardiac autonomic modulation during submaximal exercise in patients with chronic obstructive pulmonary disease: A follow-up study.

Background: Functional capacity and heart rate variability (HRV) are important prognostic markers in chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea syndrome (OSA). However, the impact of the overlap of these diseases and the one-year clinical follow-up has not yet been evaluated.

Objectives: To assess whether the presence of OSA can impair functional performance and cardiac autonomic control during exercise in patients with COPD; and to verify whether the overlap of these diseases could lead to worse clinical outcomes during the one-year follow-up.

Methods: Thirty-four patients underwent pulmonary function tests, echocardiography and polysomnography for diagnostic confirmation, disease staging, exclusion of any cardiac changes, and allocation between groups. The patients underwent the six-minute walk test (6MWT) to assess functional capacity and HRV during exercise. Subsequently, patients were followed up for 12 months to record outcomes such as exacerbation, hospitalization, and deaths. At the end of this period, the patients were revaluated to verify the hypotheses of the study.

Results: The OSA-COPD group showed greater functional impairment when compared to the COPD group (p=0.003) and showed worse cardiac autonomic responses during the 6MWT with greater parasympathetic activation (p=0.03) and less complexity of the autonomic nervous system, in addition to being more likely to exacerbate (p=0.03) during one year of follow-up.

Conclusion: OSA-COPD produces deleterious effects on functional performance and a greater autonomic imbalance that impairs clinical outcomes.