AJP - Regulatory, Integrative and Comparative Physiology, Vol 234, Issue 3 104-R109, Copyright © 1978 by American Physiological Society
Overall characteristics of arterial pressure control system studied by mild hemorrhage
H. Hosomi
The overall, static, open-loop gain of the negative-feedback arterial
pressure control system was determined repeatedly in anesthetized cats
under normal and hypovolumic states. The gain, H, was assessed as
(deltaAPI/deltaAPS)-1, where deltaAPI is the immediate fall and deltaAPS
the steady-state fall in arterial pressure following a stepwise reduction
in blood volume. When the step size was increased from 1.25 to 25% of the
total blood volume, H decreased from 30 to less than unity. Considering
this amplitude dependence of H, a small amount (1.25%) of quick (in less
than 0.3 s) hemorrhage was used to determine H throughout the rest of the
experiments. Time-dependent variation of H was evident after a large amount
(6.25%) of blood loss. During the initial 10 min, H increased to 126% of
the control value, decreased to 43% over the subsequent 20--70 min, and
showed a trend toward recovery. The small signal analysis permits a
quantitative characterization of the time and input size dependent nature
of the arterial pressure control system after various degrees of
hemorrhage.
