Generalised predictive control of evoked potentials for general anaesthesia

Changes in onset latency and relative amplitudes of somatosensory evoked potentials (SEP) have been demonstrated to be a reliable neurophysiological indicator of anaesthetic effects. Previous studies have indicated that it is feasible to use SEPs for automatic drug delivery control in propofol anaesthesia on rats premedicated with urethane. This study provides further insight into how well the control performance can be improved using the generalised predictive control (GPC) algorithm. A multi-mode controller was developed with proportional-integral (PI) control for inducing GPC learning at the beginning of drug administration, and GPC for subsequent control. Manual adjustment of salient control tuning factors allowed for operator intervention in real-time. Various GPC tuning factors were validated in trials with six rats. Each experiment began with 50 min of baseline control, then a long period of drug delivery control, and termination after a complete recovery to the baseline. Experimental results show that the GPC system provided a superior performance to the previous PI system in terms of steady-state error, and output oscillation.