[Automatic quantification of SEP for continuous patient monitoring]

Parameters presently used to analyse evoked potentials such as amplitude and latency are based on well defined single components, the recognition of which may become arbitrary in severely altered responses. Furthermore, they ignore changes also present in the remainder of an evoked potential wave form. Hence, they are ill suited for monitoring comatose patients or patients during high risk surgery. Alternatively, crosscorrelation analysis may be employed yielding two parameters by comparing the SEP of the patient with a reference response: R, the correlation coefficient, a numerical measure of similarity of the two responses in terms of overall configuration and tau, indicating the time displacement of the main common components of the two signals. A "grand average" evoked potential (SEP) composed of the responses of age and sex matched healthy subjects or in perioperative monitoring the patient's own preoperative response might be used as a reference. By help of continuous averaging of the SEP these two parameters may be determined in real time allowing a more dynamic way of monitoring than by sequential averaging individual responses.