Cardiovascular Performance Following Continuous Positive Airway Pressure in Patients with Severe Obstructive Sleep Apnea

Background: Obstructive sleep apnea (OSA) may lead to decreased exercise capacity. We investigated whether continuous positive airway pressure (CPAP) treatment improved cardiovascular performance in OSA patients. Methods: Forty healthy subjects (control group) and 40 severe OSA patients were recruited. The two groups were matched for age, gender, and body mass index. OSA patients were assigned to CPAP and non-CPAP treatment groups in equal numbers. All subjects underwent cardiopulmonary exercise testing (CPET) using a treadmill and an incremental protocol until symptom limitation (Day 0). CPET was repeated at Day 180 in the CPAP treatment group. Results: OSA patients had lower maximal oxygen consumption (V'O 2max ) (1666.3 451.3 vs. 1375.6 227.7 ml/min, 28.2 5.5 vs. 18.9 3.8 ml/min/kg) (p < 0.001), higher maximal V'E/V'CO 2 (p < 0.01), V'E/V'O 2 (p < 0.001), heart rate (HR) reserve (p < 0.001), and blunted HR recovery (HRR) at 1-5 min (p < 0.001) compared to controls. V'O 2max was negatively correlated with AHI (R 2 = 0.1363, p < 0.05). In the CPAP but not in non-CPAP treatment group, both V'O 2max (p < 0.05), HRR (p < 0.001), and HR reserve (p < 0.05) were improved on Day 180 compared to Day 0. Conclusion: Our study demonstrates that CPAP therapy for six months provides clinical benefits by improving cardiovascular performance.