Fuzzy logic monitoring and control of depth of anaesthesia

The article describes the structure of a real time measuring system based on fuzzy logic. The system uses neuro fuzzy and multiresolution wavelet analysis for monitoring the depth of anaesthesia based on the auditory evoked response signals, heart rate, and blood pressure. The AER measuring system is based on recording the brain signals using a DSP signal processing chip hosted in a PC, providing averaging and analysis using multiresolution wavelet analysis. The analysed signal is fed to a neuro fuzzy system (ANFIS) where the inference takes place to obtain a measure for the DOA. Another measure for DOA is based on the cardiovascular system (HR, BP) status using a rule based fuzzy logic classifier. The two measures are combined together using another rule based fuzzy logic classifier to decide the final DOA. Based on the classified DOA, a target concentration is decided by a rule based fuzzy logic controller which feeds the target to a target controller infusion algorithm (TCI). The system forms a closed loop controller for monitoring the depth of anaesthesia for patients undergoing surgical operation