Experiment research on the method of monitoring the depth of anesthesia

The main methods to monitor the depth of anaesthesia are based on EEG and AEP measurement, and the important parameters are BIS and AEP index. Each of them has its predominance. BIS is formed by the subparameters of EEG in time domain, frequency domain and bispectrum domain by means of a nonlinear function. The process to setup the function is very complicated. This implies that its stability is not very good. AEP index is rather reliable, but the monotone click stimulus would make patients dysphoric. So it´s necessary to study the consistency and complementarity between BIS´s subparameters and AEP index. This is just the goal of this paper. Based on the clinic requirement, we develop a new instrument to do research. The prototype instrument is composed of two parts: SCM module and PC. The SCM module is the heart of the hardware, in charge of stimulation and data acquisition, which evokes the auditory potentials, sampling the EEG and AEP signal and communicating with PC. The operating software on PC is designed by the virtual instrument workbench-Lab VIEW, and the signal processing is completed on Matlab. Experiment method: 10 rabbits, the anaesthetic is 3% pentobarbitol sodium, the dosage is 0.5, 0.25, 0.25, 0.25ml/kg, the interval is 20 minutes, EEG and AEP is recorded 5 minutes after every injection. Then EEG and AEP is recorded with the interval of 10 minutes after the last injection, and total number is 3. Result: After the signal processing, it turns out that the consistency between BIS subparameters and AEP index is rather good.