Chronic obstructive pulmonary disease severity and its association with obstructive sleep apnea syndrome: impact on cardiac autonomic modulation and functional capacity

BACKGROUND: The study was conducted to determine the impact of chronic obstructive pulmonary disease (COPD) in association with obstructive sleep apnea syndrome (OSAS) on cardiac autonomic control and functional capacity. SUBJECTS AND METHODS: The study was a cross-sectional prospective controlled clinical study. Heart rate variability indices of 24 COPD (n = 12) and COPD+OSAS (n = 12) patients were evaluated and compared by electrocardiographic recordings acquired during rest, active postural maneuver (APM), respiratory sinus arrhythmia maneuver (RSA-m), and the 6-minute walk test (6MWT). RESULTS: The COPD group presented higher parasympathetic modulation during APM when compared to the COPD+OSAS group (P = 0.02). The COPD+OSAS group presented higher sympathetic modulation during RSA-m when compared to the COPD group (P = 0.00). The performance during 6MWT was similarly impaired in both groups, despite the greater severity of the COPD group. CONCLUSION: Subjects with COPD+OSAS present marked sympathetic modulation, and the presence of OSAS in COPD subjects has a negative impact on functional capacity regardless of the severity of lung disease.