A Model-Based Self-Adjusting Two-Phase Controller for Vecuronium-Induced Muscle Relaxation Durng Anesthesia

A two-phase controller was developed to induce and maintain muscle relaxation with vecuronium. A transient controller administers drug boluses according to a two-compartment pharmacokinetic, nonlinear pharmacodynamic model. Once relaxation is within ±10 percent of the setpoint, a self-adjusting PID controller maintains relaxation. The controller gain is initially identified during the transient phase by weighted recursive least squares. Thereafter, it is automatically adjusted to compensate for background noise and varying patient gain.