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 (VO2max) (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 VE/VCO2 (p < 0.01), VE/VO2 (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. VO2max was negatively correlated with AHI (R2 = 0.1363, p < 0.05). In the CPAP but not in non-CPAP treatment group, both VO2max (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.
Key words: Obstructive sleep apnea, continuous positive airway pressure, cardiopulmonary exercise testing, heart rate recovery