Invariance of the resistance to venous return to carotid sinus
baroreflex control.
Hatanaka, Tetsuo, Jeffrey T. Potts, and Artin A. Shoukas.
Department of Biomedical Engineering, The Johns Hopkins University
School of Medicine, 720 Rutland Ave., Baltimore, Maryland 21205
APStracts 3:0188H, 1996.
Despite the well established fact that the carotid sinus baroreflex
system has profound control over the physical properties of the
systemic circulation, the resistance to venous return (RVR) seems to
be invariant of such control. We hypothesized that this apparent
paradox may be explained from the baroreflexive changes in systemic
arterial compliance. In 12 pentobarbital-anesthetized mongrel dogs,
RVR was measured at controlled carotid sinus pressures (CSP) of 50
and 200 mmHg with normal and artificially increased arterial
compliance. Arterial compliance was determined from the arterial
pressure decay when systemic blood flow was stopped with total vena
caval occlusion. Changing CSP between 50 and 200 mmHg changed RVR
significantly only under the condition of artificially increased
arterial compliance. A 4-parameter lumped model of the systemic
circulation revealed that the baroreflexive changes in arterial
compliance and arterial resistance, which occurred in opposite
directions, prevented RVR from changing when CSP was changed. The
data also suggested that 75 % of RVR was attributed to large and
conduit veins, the resistances along which were insensitive to
baroreflex control. We concluded that the invariance of RVR results
from a combination of 1) baroreflexive change in the arterial
compliance, 2) baroreflex-insensitivity of the resistance along large
and conduit veins, and 3) spatially distinct location between the
major site of reflexive change in capacitance and the major site of
compliance.
Received 25 May 1995; accepted in final form 25 March 1996.
APS Manuscript Number H488-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96