Short-term regulation of arterial pressure and the calculation of open-loop gain in the intact anesthetized dog.
Open-loop gain of the short-term systemic pressure regulation was determined under closed-loop conditions in the closed chest anesthetized dog (n = 5). For this purpose, cardiac output and mean systemic pressure were varied by ventricular pacing after the production of complete heart block. From the pressure-flow data resistance gain (the ratio of peripheral resistance change to pressure change in the steady state) was obtained by means of a simple model. The value of this gain was automatically estimated by fitting the pressure-flow relation described by the model to the experimental data. The model allows the pressure-flow relation to be straight or curved with or without a zero-flow pressure intercept. The best fit was obtained when the pressure-flow curve was convex to the pressure axis and had no intercept. When the model was linearized about the control values of pressure and flow (operating point), open-loop gain could be calculated from resistance gain. Its averaged value in the control condition, 1.63 +/- 0.45, is in agreement with values found by other investigators in open-loop conditions. During vasoconstriction open-loop gain, at the (new) operating point, increased to 2.51 +/- 0.51; during vasodilation it decreased to 1.17 +/- 0.27. Open-loop gain about an operating point thus can be determined in the intact animal from measurements of mean pressure and mean flow in the steady state.
Department of Electronics and Automatica, University of Ancona, Italy.
R
R
Burattini
P
P
Borgdorff
N
N
Westerhof
D000818:Animals; D001775:Blood Circulation; D001794:Blood Pressure; D004285:Dogs; D008954:Models, Biological; D011311:Pressoreceptors / Q000502:physiology; D012018:Reflex / Q000502:physiology; D013997:Time Factors; D014655:Vascular Resistance; D014661:Vasoconstriction; D014664:Vasodilation