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*From the Department of Medicine (Drs. Vanhecke, Franklin, Zalesin, Agrawal, and McCullough, and Mr. deJong), Divisions of Cardiology, Nutrition, and Preventive Medicine, William Beaumont Hospital, Royal Oak; and Sleep/Attention Disorders Institutes and Clinical Neurophysiology Services (Dr. Sangal), Troy, MI.
Correspondence to: Thomas E. Vanhecke, MD, Division of Cardiology, Department of Internal Medicine, William Beaumont Hospital, 3601 W 13 Mile Rd, Royal Oak, MI 48073; e-mail: tvanhecke{at}gmail.com
Abstract
Background:Conflicting data exist regarding the effects of obstructive sleep apnea syndrome (OSAS) on cardiorespiratory fitness in morbidly obese individuals with normal resting left ventricular function.
Methods:Ninety-two morbidly obese subjects without any prior diagnosis of OSAS underwent cardiorespiratory fitness testing, two-dimensional echocardiography, and overnight polysomnography. Using the results of the polysomnogram, comparisons were made between subjects with (n = 42) and without (n = 50) OSAS.
Results:Mean body mass index (BMI) for the study population (n = 92) was 48.6 ± 9.3 kg/m2 (± SD); mean age was 45.5 ± 9.8 years, and approximately 69% were female. Despite having a higher resting, exercise, and resting mean arterial pressures, the OSAS cohort had a maximum oxygen consumption that was lower than the cohort without OSAS (21.1 mL/kg/min vs 17.6 mL/kg/min; p < 0.001). There was no difference in BMI, age, gender, waist circumference, and neck circumference between those with and without OSAS. Differences were observed between the cohorts in systolic BP, diastolic BP, and heart rate during rest, exercise, and recovery periods. There was no difference in ejection fraction, diastolic dysfunction, and treadmill test duration between cohorts.
Conclusions:Morbidly obese individuals with OSAS demonstrate reduced cardiorespiratory fitness and differing hemodynamic responses to exercise testing as compared with their counterparts without this disorder. These data suggest chronic sympathetic nervous system activation negatively influences aerobic capacity in OSAS.
Key Words: cardiorespiratory fitness exercise obesity obstructive sleep apnea syndrome stress test
Abbreviations: AHI, apnea-hypopnea index BMI, body mass index bpm, beats per minute CPX, cardiopulmonary exercise stress testing DBP, diastolic BP LVEF, left ventricular ejection fraction OSAS, obstructive sleep apnea syndrome SBP, systolic BP
CO2, carbon dioxide output
E, minute ventilation
O2, oxygen consumption
O2 max, maximum oxygen consumption
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