A conscious sheep model for the examination of arterial and cardiopulmonary baroreceptors in the dynamic closed-loop control of Total Peripheral Resistance.

In this study we designed and employed a novel experimental animal model for the examination of arterial and cardiopulmonary baroreceptors in the dynamic closed-loop short-term cardiovascular control of total peripheral resistance, and applied system identification to the analysis of fluctuations in mean arterial pressure, right atrial transmural pressure, and Total Peripheral Resistance to characterize quantitatively the physiologic mechanisms responsible for the couplings between these variables. For this purpose, conscious sheep were used; where both types of baroreceptors were exposed simultaneously to random independent beat pressure variations over a small range around their operating points (via atrial pacing and occlusion of the inferior vena cava), while total peripheral resistance was measured. Subsequently, system identification was applied to the analysis of beat-to-beat fluctuations in the measured signals.