Improvement in Arterial Oxygen Control using Multiple Model Adaptive Control Procedures

A computer-based proportional-integral (PI) controller has been developed to control arterial oxygen levels in mechanically-ventilated animals. Arterial oxygen saturation is monitored using a non-invasive oximeter and control is effected by adjusting inspired oxygen fraction. The performance of the feedback system is sensitive to the open-loop gain so that the desired transient specifications can only be achieved by empirical adjustment of a PI controller. Because the open-loop gain includes the animal´s response, it may vary with time and with the administration of positive end-expiratory pressure. Multiple model adaptive control procedures were therefore used to desensitize the system to these gain variables. Computer simulations demonstrated the effectiveness of the algorithm over a wide variation of plant parameters. A comparison with a fixed well-tuned proportional-integral controller showed an improvement in the regulatory response to a step disturbance. Animal experiments reiterated the feasibility of using multiple model adaptive control procedures in arterial oxygen saturation regulation.