Patients with obstructive sleep apnea have an abnormal peripheral vascular response to hypoxia

1 Charles A. Dana Institute and the Harvard-Thorndike Laboratory of Beth Israel Deaconess Medical Center, Boston 02215; 2 Beth Israel Deaconess Sleep Disorders Center, Boston 02215; 3 Department of Medicine, Beth Israel Deaconess Medical Center, Boston 02215; and 4 Harvard Medical School, Boston, Massachusetts 02115 Patients with obstructive sleep apnea (OSA) have been reported to have an augmented pressor response to hypoxic rebreathing. To assess the contribution of the peripheral vasculature to this hemodynamic response, we measured heart rate, mean arterial pressure (MAP), and forearm blood flow by venous occlusion plethysmography in 13 patients with OSA and in 6 nonapneic control subjects at arterial oxygen saturations (Sa O 2 ) of 90, 85, and 80% during progressive isocapnic hypoxia. Measurements were also performed during recovery from 5 min of forearm ischemia induced with cuff occlusion. MAP increased similarly in both groups during hypoxia (mean increase at 80% Sa O 2 : OSA patients, 9 ± 11 mmHg; controls, 12 ± 7 mmHg). Forearm vascular resistance, calculated from forearm blood flow and MAP, decreased in controls (mean change 37 ± 19% at Sa O 2 80%) but not in patients (mean change 4 ± 16% at 80% Sa O 2 ). Both groups decreased forearm vascular resistance similarly after forearm ischemia (maximum change from baseline 85%). We conclude that OSA patients have an abnormal peripheral vascular response to isocapnic hypoxia. sleep apnea; blood pressure; vascular resistance