Automatic Blood Pressure Control in an Animal Model

Accurate and precise control of blood pressure in critical illness is essential for good clinical outcomes. Current clinical practice with manual titration of medications is prone to cycles of overshoot and undershoot, involving both increased clinician burden and more time for patients outside of the target blood pressure range. We implemented a closed-loop, automated, proportional-integral-derivative (PID) control system to manage drug infusion for targeted and precise blood pressure management in a swine model with Institutional Animal Care and Use Committee approval.

A swine was placed under general anesthesia and central venous access and arterial pressure monitoring were obtained. Baseline blood pressure was measured before infusion of clevidipine. Eight trials were performed, in each of which a target mean arterial pressure (MAP) was set and the closed loop system was allowed to alter the clevidipine infusion to reach the target (10 minutes), followed by a washout period until return to baseline blood pressure or a new baseline plateau was achieved (10 minutes). Between trials, refinements to the PID algorithm parameters were made and then tested. In addition, for some cycles, a series of incremental target MAPs was implemented to attempt more gradual reduction to target. System performance was assessed based on the time to reach and maintain MAP within 5 mmHg of the target as well as the magnitude of overshoot past the target pressure.

The average change from starting condition to target was 14.25 ± 3.20 mmHg. All trials settled to target MAP ± 5 mmHg within 3.36 ± 1.49 minutes and maintained the target until the system was deactivated. The average magnitude of overshoot was 3.50 ± 2.51 mmHg.

An automatic closed loop system achieved rapid blood pressure control with minimal overshoot. Further refinement and validation is needed, including testing in animal models of hyper- and hypotension.