A Comparison Between Walsh and Fourier Analysis of the Electroencephalogram for Tracking the Effects of Anesthesia

The effects that anesthesia has on the surgical patient can be characterized with the electroencephalogram (EEG). These effects are typically quantified through frequency analysis of the EEG signal. The fast Fourier transform (FFT) is usually employed for this purpose. In recent years, the fast Walsh transform (FWT) has been proposed as an alternative to the FFT for signal analysis because it is computationally more efficient, requiring less time to complete on a digital computer. This paper statistically evaluates the quantitative and dynamic differences between the results of Walsh and Fourier analysis of the EEG done for the purpose of characterizing the effects of anesthesia. This paper shows that there are quantitative differences between the results of the two frequency analysis techniques but they are dynamically equivalent, both showing essentially the same changes due to the effects of anesthesia. The efficiency of the FWT has been reconfirmed. These results support the use of the FWT in place of the FFT for tracking the effects of anesthesia on surgical patients with the EEG.