Concept for an intelligent anaesthesia EEG monitor

Considering the fundamental difficulties to define the term 'depth of anaes thesia', a more feasible concept for assessment of 'adequacy of anaesthesia ' will be explained. The basic requirements for a monitoring index are defi nite response, gradual scaling and independence from the anaesthetic techni que used. Additionally the index should be predictive for appearance of cli nical signs of an inadequate anaesthesia. Different signal-processing metho ds will be discussed to extract the relevant information from both the spon taneous and the evoked brain electrical activity. In this context well esta blished methods like spectral analysis are investigated in combination with new and more sophisticated methods like bispectral analysis or wavelet dec omposition. Since no single-parameter index has been defined for monitoring depth of anaesthesia, a set of EEG parameters may be more useful to take i nto account intra- and interindividual variability. In parallel to the desc ription of the monitor concept, the investigation of neural nets and fuzzy techniques, in addition to or in substitution of conventional statistical m ethods, will be introduced. Examples are given for data quality assessment, parameter extraction and re-classification.