Signal Processing, Computer-Assisted

Spectral analysis of beat-to-beat variability in electrocardiography is a simple, noninvasive method to analyze sympatho-vagal interaction. The electrocardiogram is analyzed by means of an automatic, autoregressive modeling algorithm that provides a quantitative estimate of R-R interval variability by the computation of power spectral density. Two major peaks are recognizable in this specter: a low-frequency peak (LF, -0.1 Hz), related to the overall autonomic activity (ortho+parasympathetic) and a high-frequency peak (HF, -0.25 Hz), representative of the vagal activity.

Dynamics of structural changes of coherent relations between electrical activity of sensorimotor and premotor cortical areas of both cerebral hemispheres during and after "animal hypnosis" was studied by spectral-correlative analysis in rabbits. It was shown that "animal hypnosis" had very long-lasting trace processes, i.e., hypnotic structure of coherent relations of electrical activity in the cerebral cortex was maintained during several days.

Hypnotherapeutical technique were often used for control of pain. However, an objective examination of this phenomenon was seldom carried out. The aim of the study was the psychophysiological objectivation of the effect of experimental induced pain and the elimination of pain by means of hypnosis. 22 healthy volunteers (11 female and 11 male) aged between 22 and 35 years participated in the study.

Intercentral relations of electrical activity of sensorimotor and premotor cortical areas of the right and left hemispheres were studied by means of coherence analysis during interaction of "animal hypnosis" and motor polarization dominant created by the action of DC anode on the area of the left hemisphere in rabbits. It was shown that the session of the "animal hypnosis" performed on the background of the optimum of polarization dominant elicited disappearance of asymmetry of coherence in the delta-range frequency of electrical activity of the examined cortical areas.

Higher frequency electroencephalographic (EEG) activity around 40 Hz has been shown to play a role in cognitive functions such as attention. Furthermore, event-related brain potential (ERP) components such as N1 and P1 are sensitive to selective attention. In the present study, 40-Hz EEG measures and early ERP components were employed to relate selective attention to hypnotic response. Participants were 20 low hypnotizable individuals, half assigned as simulators, and 21 high hypnotizable individuals.

OBJECTIVE: Assessment of the usefulness of Bispectral Index of the EEG (BIS) for the management of hypertension during laparoscopic surgery. STUDY DESIGN: Preliminary, non-randomized study. PATIENTS: 15 patients undergoing laparoscopic surgery. METHODS: Anaesthesia by TCI of propofol and boluses of fentanyl in order to maintain fentanyl effect site concentration above 2 ng.mL-1 according to Scott kinetics model. Mean arterial pressure (MAP), heart rate (HR) and BIS were recorded.

A model-based closed-loop control system is presented to regulate hypnosis with the volatile anesthetic isoflurane. Hypnosis is assessed by means of the bispectral index (BIS), a processed parameter derived from the electroencephalogram. Isoflurane is administered through a closed-circuit respiratory system. The model for control was identified on a population of 20 healthy volunteers. It consists of three parts: a model for the respiratory system, a pharmacokinetic model and a pharmacodynamic model to predict BIS at the effect compartment. A cascaded internal model controller is employed.

Individuals differ in hypnotizability. Information on hypnotizability-related EEG characteristics is controversial and incomplete, particularly on intracerebral source localization and EEG dimensionality. 19-channel, eyes-closed resting EEGs from right-handed, healthy, 8 high- and 4 low-hynotizable subjects (age: 26.7 +/- 7.3 years) were analyzed. Hypnotizability was rated after the subjects' ability to attain a deep hypnotic stage (amnesia).

Impacts of hypnotic drugs on brain function are reflected in the EEG. The EEG monitor Narcotrend performs an automatic classification of the EEG using a scale which was proposed by Kugler for visual evaluation of the EEG. In this article the results of a validation study of the automatic classification algorithms implemented in the EEG monitor Narcotrend are presented. Visual and automatic classification of EEG data recorded in routine clinical practice were compared.