Comparison of heart rate fluctuation parameters with postural
changes in humans.
Kvas, E., A. R[diaeresis]ossler, Z. L[acute]aszl[acute]o, H. G.
Hinghofer-Szalkay.
Volume Regulation and Space Medicine Research Group, Department of
Physiology, School of Medicine, Karl-Franzens University, Graz,
Austria; and Institute for Adaptive and Spaceflight Physiology,
Austrian Society for Aerospace Medicine (ASM), A-8010 Graz,
Austria
APStracts 3:0363H, 1996.
Purpose of the study was to compare parameters for heart rate
variability (HRV), autodependence, and regularity for their
sensitivity to orthostatic change, and efficiency to discern
sympathetic versus parasympathetic influence. Seven healthy males
were brought to 12, 30, 53, and 70 degrees of head-up position for 30
min to change their vagal-sympathetic activities in a quantitative
fashion. To achieve stationarity the first differences were derived
from beat-to-beat heart rate time-series. Time-series data were
filtered for the low (0.05-0.15 Hz, LF) and high (0.15-0.35 Hz, HF)
frequency band to separate sympathetic and parasympathetic
activities. For heart rate variability, the following parameters were
computed: approximate entropy, fractal dimension, and root mean
square successive difference. For heart rate autodependence and
regularity, autocorrelation coefficients, and frequency of runs with
different length were calculated. Parameters were compared with
regard to sensitivity (supine vs. upright) and efficiency (LF vs.
HF). All measures were significantly altered with tilting to 53 and
70 degrees ; autocorrelation coefficients were sensitive to HUT 30 as
well. Whereas regularity parameters were found to be effective for
LF, HRV parameters were effective for HF. We conclude that
autocorrelation measures as an estimation of autonomic balance reveal
more accurate information on heart rate fluctuations during passive
orthostasis in humans than conventional HRV parameters.
Received 13 August 1996; accepted in final form 14 August 1996.
APS Manuscript Number H741-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996