Estimation of the anesthetic depth based on instantaneous frequency of electroencephalogram

Estimating an accurate and fast-to-compute index to measure depth of anesthesia (DoA) is still a challenge. Although Bispectral Index Scale (BIS) is a reliable and FDA approved measure of DoA, it is a lazy index that can only be computed every 10 seconds. In this paper, to find a reliable and much faster index, the frequency components of EEG signals of four patients during orthopedic surgery are investigated in order to detect a connection between DoA and the frequency components. By simultaneous observation of STFT and Wigner-Ville distribution EEGs along with their BIS values, we found such a frequency component in the EEG signals. This feature is elicited using several Instantaneous Frequency (IF) methods. The simulation results confirmed a significant statistical positive correlation between the proposed IF of the EEG signal and the corresponding BIS for all four patients.