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. 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 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. 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 was 1. 63 plus or minus 0. 45. 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.