Surges of muscle sympathetic nerve activity during obstructive
apnea are linked to hypoxemia .
Leuenberger, Urs, Elizabeth Jacob, Leon Sweer, Neil Waravdekar,
Clifford Zwillich, Lawrence Sinoway.
Divisions of Cardiology and Pulmonary and Critical Care Medicine,
Department of Medicine, The Milton S. Hershey Medical Center, The
Pennsylvania State University, Hershey, Pennsylvania 17033
APStracts 2:0162A, 1995.
Obstructive sleep apnea (OSA) is associated with oscillations of
arterial blood pressure (BP) that occur in phase with irregularities
of respiration. To explore the role of the sympathetic nervous system
in these responses we studied muscle sympathetic nerve activity
(MSNA, peroneal microneurography), an index of vasoconstrictor nerve
traffic, and BP during awake regular breathing and during spontaneous
apneas in patients with OSA. To determine the role of the arterial
chemoreflex, we also examined the effects of 100% O2 (hyperoxia) on
MSNA and BP. In awake, regularly breathing patients with OSA (n=12),
resting MSNA (mean+/-SD) was markedly higher than in an age-matched
control population (n=15) (41+/-23 vs. 24+/-17 bursts/min; P<0.05)
and was unchanged during hyperoxia (n=9). Apneas during sleep (n=8)
were associated with surges in MSNA followed by transient rises in BP
when breathing resumed. In contrast to room air apneas, hyperoxic
apneas of similar duration were associated with attenuated MSNA
responses (+82+/-84% vs. +5+/-25% compared to awake baseline,
P<0.05; n=6) even though O2 did not affect sleep stage and the
occurrence of arousal. Thus, the BP oscillations that occur with
apnea during sleep may in part be mediated by intermittent surges of
sympathetic activity resulting in vasoconstriction. Because the MSNA
responses to obstructive apnea are blunted during O2 administration,
they appear to be linked to intermittent arterial hypoxemia and
stimulation of arterial chemoreceptors.
Received 29 December 1993; accepted in final form 13 April 1995.
APS Manuscript Number A1246-3.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.