Baroreflex open-loop gains estimated in humans by graded Valsalva maneuver

To estimate open-loop baroreflex gains in humans, the authors applied a model-based method to experimental data measured by P.I. Korner et al. (1976) in normal man. These data were average changes of mean arterial pressure, right atrial pressure, and cardiac output from control to the last 10 s of a 30-s Valsalva maneuver, at 20 mmHg expiratory pressure. An overall open-loop gain, G₀₀, equal to 8.1, was obtained. This gain is the sum of the open-loop gain of peripheral resistance regulation (G₀=6.4) and the open-loop gain of cardiac output regulation (K₀=1.7). These results indicate that arterial pressure compensation in these subjects was accomplished via reflex change of peripheral resistance by about 79%, and of cardiac output by 21%