Normalized Bispectrum Ratio: Parameter for estimating depth of anesthesia

Electroencephalogram (EEG) is the brain signal containing valuable information about the conscious and unconscious state of the brain, which may provide a useful tool to measure depth of anesthesia. In order to avoid complex and time consuming interpretation of raw EEG signals a common approach is to extract a single univariate value (if possible) that represents the patient´s depth of anesthesia. In this paper, a novel index, Normalized Bispectrum Ratio, R_B is proposed which is based upon the difference between bispectrum values of EEG signals of conscious and unconscious states of human.