Figure 2. Experimental design.

In system identification studies, open-loop (protocol 1, CSP was perturbed according to a binary random sequence) and closed-loop-spontaneous (protocol 2, CSP was matched with systemic AP) baroreflex transfer functions were identified from experimental data. In predictability studies, the predictive power of the above transfer functions was tested using independent data (protocols 3, 4 and 5). Protocol 3 and 4 were open-loop and closed-loop-spontaneous baroreflex conditions, respectively. Protocol 5 was pharmacological pressure intervention by phenylephrine and nitroprusside infusions in closed-loop condition. TF, transfer function; CSP, carotid sinus pressure; SNA, sympathetic nerve activity; AP, arterial pressure.