Hypoxia-induced vasodilation and effects of regional phentolamine in awake patients with sleep apnea.
Obstructive sleep apnea (OSA) is associated with increased sympathetic nerve activity, endothelial dysfunction, and premature cardiovascular disease. To determine whether hypoxia is associated with impaired skeletal muscle vasodilation, we compared femoral artery blood flow (ultrasound) and muscle sympathetic nerve activity (peroneal microneurography) during exposure to acute systemic hypoxia (fraction of inspired oxygen 0.1) in awake patients with OSA (n=10) and controls (n=8). To assess the role of elevated sympathetic nerve activity, in a separate group of patients with OSA (n=10) and controls (n=10) we measured brachial artery blood flow during hypoxia before and after regional alpha-adrenergic block with phentolamine. Despite elevated sympathetic activity, in OSA the vascular responses to hypoxia in the leg did not differ significantly from those in controls [P=not significant (NS)]. Following regional phentolamine, in both groups the hypoxia-induced increase in brachial blood flow was markedly enhanced (OSA pre vs. post, 84+/-13 vs. 201+/-34 ml/min, P<0.002; controls pre vs. post 62+/-8 vs. 140+/-26 ml/min, P<0.01). At end hypoxia after phentolamine, the increase of brachial blood flow above baseline was similar (OSA vs. controls +61+/-16 vs. +48+/-6%; P=NS). We conclude that despite high sympathetic vasoconstrictor tone and prominent sympathetic responses to acute hypoxia, hypoxia-induced limb vasodilation is preserved in OSA.
Pennsylvania State Heart and Vascular Institute, Department of Anesthesia, H047, Pennsylvania State University College of Medicine, P.O. Box 850, Hershey, PA 17033, USA.
Raman
R
Moradkhan
Brett
B
Spitnale
Patrick
P
McQuillan
Cynthia
C
Hogeman
Kristen S
KS
Gray
Urs A
UA
Leuenberger
D000317:Adrenergic alpha-Antagonists; D000328:Adult; D001340:Autonomic Nerve Block / Q000379:methods*; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D016022:Case-Control Studies; D005260:Female; D005263:Femoral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D000860:Hypoxia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000294:innervation; D010543:Peroneal Nerve / Q000503:physiopathology; D010646:Phentolamine; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply; D020181:Sleep Apnea, Obstructive / Q000000981:diagnostic imaging / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology; D018608:Ultrasonography, Doppler; D014661:Vasoconstriction; D014664:Vasodilation; D014851:Wakefulness
D000317:Adrenergic alpha-Antagonists; D010646:Phentolamine