Fig. 3. Photograph showing the concurrent BISxp trends over a 55-min period from patient 5. The signal quality index was very high, and there was no interference on either device from electromyography. In this patient, there was the most discrepancy between the two Bispectral Index readings over a sustained period of anesthesia. EEG = electroencephalogram; EMG = electromyogram; SQI = signal quality index; SR = suppression ratio.