MODELING ESTIMATION AND CONTROL IN THE RELIEF OF POSTOPERATIVE PAIN

The paper arises from collaborative work to explore contributions which the technology of control engineering can make to pain relief. One particular demand analgesia system was studied in which Fentanyl was intravenously infused to relieve pain during the first day after total hip-replacement. A mathematical model is presented in which pain is modelled as the difference between discomfort and comfort and is measured by the frequency at which the patient presses a button. This is inherently nonlinear because there is no button-pressing when comfort exceeds discomfort. A novel nonlinear estimation scheme to handle the nonlinearity is implemented in an on-line microcomputer to provide model-based stochastic control.