title: Investigating Power Density and the Degree of Nonlinearity in Intrinsic Components of Anesthesia EEG by the Hilbert-Huang Transform: An Example Using Ketamine and Alfentanil.
abstract: Empirical mode decomposition (EMD) is an adaptive filter bank for processing nonlinear and non-stationary signals, such as electroencephalographic (EEG) signals. EMD works well to decompose a time series into a set of intrinsic mode functions with specific frequency bands. An IMF therefore represents an intrinsic component on its correspondingly intrinsic frequency band. The word of 'intrinsic' means the frequency is totally adaptive to the nature of a signal. In this study, power density and nonlinearity are two critical parameters for characterizing the amplitude and frequency modulations in IMFs. In this study, a nonlinearity level is quantified using degree of waveform distortion (DWD), which represents the characteristic of waveform distortion as an assessment of the intra-wave modulation of an IMF. In the application of anesthesia EEG analysis, the assessments of power density and DWD for a set of IMFs represent dynamic responses in EEG caused by two different anesthesia agents, Ketamine and Alfentanil, on different frequency bands. Ketamine causes the increase of power density and the decrease of nonlinearity on γ-band neuronal oscillation, which cannot be found EEG responses of group B using Alfentanil. Both agents cause an increase of power density and a decrease of nonlinearity on β-band neuronal oscillation accompany with a loss of consciousness. Moreover, anesthesia agents cause the decreases of power density and nonlinearity (i.e. DWD) for the low-frequency IMFs.
authors.affiliation: Department of Anesthesiology, National Taiwan University Hospital, Taipei, Taiwan.|Department of Anesthesiology, College of Medicine, National Taiwan University, Taipei, Taiwan.|Rey Institute for Nonlinear Dynamics in Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States of America.
authors.forename: Feng-Fang
authors.initials: FF
authors.lastname: Tsai
authors.affiliation: Department of Anesthesiology, National Taiwan University Hospital, Taipei, Taiwan.|Department of Anesthesiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Shou-Zen
authors.initials: SZ
authors.lastname: Fan
authors.affiliation: Department of Anesthesiology, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Yi-Shiuan
authors.initials: YS
authors.lastname: Lin
authors.affiliation: Center for Dynamical Biomarkers and Translational Medicine, National Central University, Taoyuan, Taiwan.|Research Center for Adaptive Data Analysis, National Central University, Taoyuan, Taiwan.
authors.forename: Norden E
authors.initials: NE
authors.lastname: Huang
authors.affiliation: Center for Dynamical Biomarkers and Translational Medicine, National Central University, Taoyuan, Taiwan.|Research Center for Adaptive Data Analysis, National Central University, Taoyuan, Taiwan.
authors.forename: Jia-Rong
authors.initials: JR
authors.lastname: Yeh
mesh_terms: D015760:Alfentanil / Q000008:administration & dosage / Q000737:chemistry*; D000465:Algorithms; D000758:Anesthesia / Q000379:methods*; D000776:Anesthesiology; D016208:Databases, Factual; D004569:Electroencephalography; D006801:Humans; D007649:Ketamine / Q000008:administration & dosage / Q000737:chemistry*; D016343:Monitoring, Intraoperative / Q000379:methods; D009474:Neurons / Q000502:physiology; D017711:Nonlinear Dynamics; D009991:Oscillometry; D010092:Oximetry; D015203:Reproducibility of Results; D012306:Risk; D012815:Signal Processing, Computer-Assisted; D013514:Surgical Procedures, Operative
chemical_list: D015760:Alfentanil; D007649:Ketamine