A new method to monitor depth of anesthesia based on the autocorrelation EEG signals

To have a safe, noninvasive, reliable and economic anesthetic depth indicator, the change of the a rhythm of electroencephalogram (EEG) signal on autocorrelation property during general intravenous anesthesia is investigated based on the effects of general anesthetics on the a rhythm of EEG in prefrontal cortex area. To synthesize the effects of correlated behavior, the contamination of muscle artifact is not removed from the EEG data. The autocorrelation analysis shows: 1) The EEG signals in prefrontal cortex area on autocorrelation are sensitive to different anesthesia depths during general anesthesia. The difference of autocorrelation trace from awareness to anesthesia is obvious. The change of autocorrelation trace is consistent with the anesthesia process; 2) The changes of autocorrelation in FP1-Cz channel and FP2-Cz channel with time are almost synchronous during general anesthesia. This means that 1-channel- recordings from prefrontal cortex are sufficient to monitor depth of anesthesia; 3) The value of autocorrelation in anesthesia fluctuates within a small range and is small than 20. This means that the value of autocorrelation is stable in anesthesia; 4) The differences of the range that the value of autocorrelation fluctuates in anesthesia present individual differences in a way. Being calculation simple, single channel and the transition of autocorrelation trace from awareness to anesthesia obvious, this technique may be ease to use, low running cost and can be applied in real time. Autocorrelation may provide a new method to monitor depth of anesthesia in clinic.