Exercise capacity in patients with obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a common disease characterized by repetitive partial or complete closure of the upper airway during sleep. Cardiovascular disturbances are the most important complications responsible for increased morbidity and mortality. It is suggested that daytime somnolence, chronic fatigue, and nocturnal hypoxemia may further impair muscle function and decrease exercise fitness. The aim of this study was to evaluate cardiopulmonary response to exercise in OSAS patients. One hundred and eleven middle aged (50.2 +/- 10 yr), obese (BMI 31.0 +/- 4.6 kg/m(2)) patients (109 M, 2F) with severe OSAS (AHI 47.2 +/- 23.1 h(-1)) were enrolled into the study. OSAS was diagnosed with overnight polysomnography and a symptom-limited cardiopulmonary exercise test was performed on a treadmill using Bruce protocol. The results showed that the most frequent reason for exercise termination were: muscle fatigue and/or dyspnea (66%), increase in systolic blood pressure >220 mmHg (20%), ECG abnormalities, and chest pain (6%). Although the mean V-O2 peak was within the reference value (29.6 +/- 6 mlO(2)/kg/min), in 52 patients (46%) V-O2 peak was <84% of predicted. Hypertensive response to exercise was diagnosed in 39 of patients (35%). Patients with severe sleep apnea (AHI >= 40 h(-1)) were characterized by higher mean blood pressure at rest, at 25%, 50% of maximal work load, at peak exercise and at post-exercise recovery. Several significant correlations between hemodynamic responses to exercise and sleep apnea severity were also noted. We conclude that exercise tolerance can be limited due to hypertensive response in about 20% of patients. Patients with severe OSAS have exaggerated hemodynamic response to exercise and delayed post-exercise blood pressure recovery. Cardiopulmonary response to exercise seems to be related to sleep apnea severity.