BACKGROUND: Analysis of the bispectrum of EEG waveforms is a component of the proprietary BIS index-a commonly used commercial monitor of depth of anaesthesia. Does the use of the bispectrum give more information about depth of anaesthesia than the power spectrum? METHODS: We collected and analysed EEG waveforms during induction of general anaesthesia in 39 patients, comparing the changes in bispectral parameter (SynchFastSlow), with an analogous power spectrum-based parameter (PowerFastSlow). Both compare the logarithmic ratio of high frequency components (40-47 Hz) with the total (1-47 Hz). Because the changes in bispectrum are affected by signal amplitude, we also calculated a third parameter (SFSbicoh) from the bicoherence, which is an amplitude-independent statistic. RESULTS: The SynchFastSlow and PowerFastSlow were correlated (r=0.84) and neither was superior in predicting the awake or anaesthetized state (area under receiver operating characteristic curves = 0.85 vs 0.93). There was no change in the SFSbicoh over the induction period, and it did not correlate with SynchFastSlow (r=0.07). CONCLUSIONS: We could not show that bispectral analysis gave more information than power spectral-based analysis. Most of the changes in the bispectral values result from decreases in the relative high frequency content of the EEG caused by anaesthesia.
BACKGROUND: Analysis of the bispectrum of EEG waveforms is a component of the proprietary BIS index-a commonly used commercial monitor of depth of anaesthesia. Does the use of the bispectrum give more information about depth of anaesthesia than the power spectrum? METHODS: We collected and analysed EEG waveforms during induction of general anaesthesia in 39 patients, comparing the changes in bispectral parameter (SynchFastSlow), with an analogous power spectrum-based parameter (PowerFastSlow). Both compare the logarithmic ratio of high frequency components (40-47 Hz) with the total (1-47 Hz). Because the changes in bispectrum are affected by signal amplitude, we also calculated a third parameter (SFSbicoh) from the bicoherence, which is an amplitude-independent statistic. RESULTS: The SynchFastSlow and PowerFastSlow were correlated (r=0.84) and neither was superior in predicting the awake or anaesthetized state (area under receiver operating characteristic curves = 0.85 vs 0.93). There was no change in the SFSbicoh over the induction period, and it did not correlate with SynchFastSlow (r=0.07). CONCLUSIONS: We could not show that bispectral analysis gave more information than power spectral-based analysis. Most of the changes in the bispectral values result from decreases in the relative high frequency content of the EEG caused by anaesthesia.
Authors: E Wodey; O Tirel; J Y Bansard; A Terrier; C Chanavaz; R Harris; C Ecoffey; L Senhadji Journal: Br J Anaesth Date: 2005-04-15 Impact factor: 9.166
Authors: Christopher P Pawela; Bharat B Biswal; Anthony G Hudetz; Marie L Schulte; Rupeng Li; Seth R Jones; Younghoon R Cho; Hani S Matloub; James S Hyde Journal: Neuroimage Date: 2009-03-12 Impact factor: 6.556
Authors: Patrick L Purdon; Eric T Pierce; Eran A Mukamel; Michael J Prerau; John L Walsh; Kin Foon K Wong; Andres F Salazar-Gomez; Priscilla G Harrell; Aaron L Sampson; Aylin Cimenser; ShiNung Ching; Nancy J Kopell; Casie Tavares-Stoeckel; Kathleen Habeeb; Rebecca Merhar; Emery N Brown Journal: Proc Natl Acad Sci U S A Date: 2013-03-04 Impact factor: 11.205