Short-term control of cardiovascular function: estimation of
control parameters by adjustment of a mathematical model to
physiological recordings from healthy humans.
Toska, Karin, Morten Eriksen, Lars Walle.
Department of Physiology, Institute of Basic Medical Sciences,
University of Oslo, P.O.Box. 1103-Blindern, N-0317 Oslo, Norway
APStracts 2:0334H, 1995.
In a previous study, we recorded short-term cardiovascular responses
after a steep increase in arterial pressure in healthy humans [K.
Toska, M. Eriksen, L. Wall[phi]e. Am. J. Physiol. 266 (Heart Circ.
Physiol. 35): H199-H211,1994]. The aim of the present study was to
develop a mathematical model of the baroreflex control of arterial
pressure, to use this model together with the previously recorded
data to estimate unknown parameters in the reflex control loop, and
then to analyze the overall open- and closed-loop performance of the
system by model simulations using individual sets of optimal
parameters. The mathematical model consists of a heart, a linear,
elastic arterial reservoir and two parallel, resistive vascular beds.
The arterial baroreflex loop is modeled by two separate time domain
processing objects, each with its own gain, time constant and delay,
in order to simulate the action of a sympathetic signal to the
peripheral vascular bed and a parasympathetic signal to the heart. In
repeated model simulations, the control parameters in the model were
systematically adjusted by an automated algorithm which minimized the
deviations between the time courses of the cardiovascular variables
simulated by the model and the previously recorded responses in each
individual. In all 10 subjects, the short-term cardiovascular
responses were adequately simulated by using individual sets of
parameters in the model. Open-loop transfer functions for arterial
pressure control were obtained by using the individual sets of
optimal model parameters in new simulation runs. Open-loop gain for
arterial pressure control at nearly zero frequency (steady state) was
between 0.9 and 4. Model simulations also indicated an underdampened
response at 0.5-0.7 Hz in the closed-loop situation in 4 subjects,
corresponding to peaks in the mean arterial pressor power spectra
obtained from separate recordings of spontaneous variations in the
resting situation.
Received 23 November 1994; accepted in final form 1 August 1995.
APS Manuscript Number H1042-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.