Lack of peripheral modulation of cardiovascular central oscillatory
autonomic activity seen during apnea in man.
Passino, Claudio, Peter Sleight, Felice Valle, Giammario Spadacini,
Stefano Leuzzi, Luciano Bernardi.
Department of Internal Medicine, University of Pavia, 27100 Pavia,
Italy, Department of Cardiovascular Medicine, John Radcliffe
Hospital, Oxford, U.K.
APStracts 3:0259H, 1996.
Respiratory sinus arrhythmia (RSA-HF) and slow fluctuations in heart
rate (LF) are thought to result either from entrainment of a
medullary oscillator or from the baroreflex or from a combination of
both central and baroreflex mechanisms. We sought to distinguish
between the alternatives by examining, with spectral analysis, the
behaviour of heart rate (RR) and blood pressure in ten healthy
subjects (mean age 27+/-1 yrs) during apnea, altering the rate of pre
apnea entrainment stimuli by either changing the frequency of
respiration (controlled at 0.1 or 0.25 Hz) or of baroreceptor
stimulation by sinusoidal neck suction (0 to -30 mmHg, 0.1 or 0.2
Hz). During apnea the RSA-HF power decreased (from 6.73+/-0.15 to
3.67+/-0.10 ln-ms2; p<0.0001), whatever the pre-apnea
conditions, whereas LF power was reduced only if preceded by 0.1 Hz
respiration or neck suction (from 8.71+/-0.18 to 6.52+/-0.11,
p<0.001 and from 8.31+/-0.23 to 6.90+/-0.38 ln-ms2, p<0.01,
respectively). The LF frequency seen in the RR during apnea was
slower than the spontaneous LF during 0.25 Hz breathing (0.082+/-0.01
Hz vs 0.112+/-0.001 Hz, p<0.001) but the maneuvers during pre
-apnea had no influence on the observed frequency or other
characteristics of the slow oscillations during apnea. Moreover we
found no evidence of a progressive decrease in the power of the
oscillation during apnea. The same behaviour was observed on the mean
blood pressure signal. In conclusion, a slow rhythm is present during
apnea: in healthy subjects at rest the characteristics of this
oscillation indicate that it could be generated by a central
oscillator; this may thus contribute to the origin of the LF present
during normal respiration, in addition to the baroreflex.
Received 26 January 1996; accepted in final form 29 May 1996.
APS Manuscript Number H4-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 July 96