Heart Rate Recovery and Oxygen Kinetics After Exercise in Obstructive Sleep Apnea Syndrome

Background Patients who suffer from obstructive sleep apnea (OSA) have a decreased exercise capacity and abnormal autonomic nervous function. However, the kinetics of early oxygen (O 2 ) and heart rate recovery (HRR) have not been described. Materials and Methods We evaluated 21 men with moderate to severe OSA (mean age: 48 ± 11 yrs, mean apnea‐hypopnea index [AHI]: 55 ± 13) and without known heart disease and 10 healthy men matched for age and body mass index (BMI; controls). Men with OSA underwent overnight polysomnography, and both groups underwent symptom‐limited incremental cardiopulmonary exercise testing (CPET). We recorded the CPET parameters including peak O 2 uptake (V O 2 p), kinetics of early O 2 recovery by the first degree slope of V O 2 during the first minute (V O 2 /t slope), the time required for a 50% decline of V O 2 p during recovery (T 1/2 ), and early heart rate recovery (HRR = HR at maximal exercise − HR at 1 min of recovery), as well as the chronotropic reserve to exercise ([CR] = [peak HR − resting HR/220 − age − resting HR] × 100). Patients with OSA had a lower V O 2 p (28.7 ± 4.0 vs 34.7 ± 6.2 mL/kg/min), V O 2 /t slope (1.04 ± 0.3 vs 1.4 ± 0.17 mL/kg/min 2 ), and T 1/2 (74 ± 10 vs 56 ± 6 sec) compared to controls (all P < 0.001). In addition, both HRR and CR were lower in the OSA group (22.0 ± 7.0 vs 31.0 ± 6.0 bpm, P :0.003, and 79.0% ± 15% vs 99.0% ± 13.0%, P :0.01, respectively). Conclusions Patients with OSA demonstrate reduced exercise capacity, delayed oxygen kinetics, and reduced HRR. These data point to abnormal oxygen delivery and/or oxidative function of the peripheral muscles and impaired autonomic nervous activity in OSA patients. Copyright © 2010 Wiley Periodicals, Inc.