Methods and apparatus for monitoring consciousness

• US 7,774,052 B2
• Filed: 12/09/2003
• Issued: 08/10/2010
• Est. Priority Date: 06/13/2001
• Status: Active Grant

• Current Assignee: Compumedics Limited
• Original Assignee: Compumedics Limited
• Inventors: Burton, David, Zilberg, Eugene
• Primary Examiner(s): Mallari; Patricia C
• Assistant Examiner(s): Toth; Karen E
• Application Number:
  US10/731,816
• Publication Number:
  US 20040193068A1
• Time in Patent Office: 2,436 Days
• Field of Search: 600544-546
• US Class Current: 600/544
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/16 Devices for psychotechnics using teaching or educational appliances G09B1/00 - G09B7/00; Testing reaction times ; Devices for evaluating the psychological state
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/372 Analysis of electroencephalograms
• CPC Class Codes: A61B 5/374 Detecting the frequency distribution of signals, e.g. detecting delta, theta, alpha, beta or gamma waves
• CPC Class Codes: A61B 5/398 Electrooculography [EOG], e.g. detecting nystagmus; Electroretinography [ERG]
• CPC Class Codes: A61B 5/411 Detecting or monitoring allergy or intolerance reactions to an allergenic agent or substance
• CPC Class Codes: A61B 5/4809 Sleep detection, i.e. determining whether a subject is asleep or not
• CPC Class Codes: A61B 5/4812 Detecting sleep stages or cycles
• CPC Class Codes: A61B 5/6821 Eye
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

The systems of the present invention provide improved accuracy in monitoring, analysing, detecting, predicting and/or providing alerts and alarms associated with depth of anaesthesia, depth of consciousness, hypnotic state, sedation depth, fatigue or vigilance of a subject, with as few as 3 surface electrodes. The systems incorporate real-time phase, amplitude and frequency analysis of a subject'"'"'s electro-encephalogram. The systems weight outputs of various types of analyses to produce an integrated analysis or display for precise indication or alert to users of the systems including anaesthetists, nurses and other medical personnel, transport drivers and machine workers. The systems weight the outputs of one or more analysis algorithms including combinations of simultaneous, real-time R&K analysis, AEP spectral analysis-SEF-MF, Bi-coherence analysis, initial wave analysis, auditory response, arousal analysis, body movement analysis, 95% spectral edge analysis and anaesthetic phase and spectral energy variance measurement in association with a subject'"'"'s state of consciousness.

Claims

1. A method for acquiring, characterising and classifying biosignals from a living being for determining the state of consciousness of said being comprising:

acquiring at least one continuous biosignal;

stimulating an evoked potential response signal in said being;

deriving at least one evoked potential response signal from said at least continuous biosignal using a processor;

deriving a first index of consciousness from said continuous biosignal;

deriving a second index of consciousness from said evoked potential response signal; and

classifying said indices as being representative of entering or leaving consciousness according to a weighting process.

2. The method of claim 1 wherein the continuous biosignal is an EEG (electroencephalogram) signal or a muscular activation signal or both.

3. The method of claim 2 wherein the muscular activation signal is a measure of eyelid movement.

4. The method of claim 2 wherein the EEG signal is a continuous signal.

5. The method of claim 1 further comprising monitoring signals for signal quality.

6. The method of claim 1 wherein said acquiring said at least one continuous biosignal includes using at least one disposable or semi-disposable sensor.

7. The method of claim 6 wherein said at least one disposable or semi-disposable sensor includes means for activating an electrical energy source.

8. The method of claim 7 wherein the means for activating said energy source includes the packaging of said electrical energy source.

9. The a method of claim 1 wherein said evoked potential response signal comprises any one or a combination of somatosensory, auditory, or visual evoked response.

10. The method of claim 1 whereby said stimulating induces a steady state response signal or any combination of signals inducing associated auditory evoked response or responses classified as the following either singly or in combination greater than:

60 Hz ASSR (auditory steady state response), 40 Hz ASSR, or less than 20 Hz ASSR.

11. The method of claim 1 further comprising displaying a functional or operational status of a sensor.

12. The method of claim 1 wherein said stimulating includes producing any one of or a combination of evoked response paradigms including:

at least one type of click stimulus;

at least one response at spaced intervals within a click stimulus

sounds of white noise or speech

oddball sound characteristics

unusual sound characteristics

masked noise sounds

unanticipated noise sounds

composite sounds

familiar sounds

recognizable sounds in reference to said being

wherein a combination of any sound stimulus is generated according to a predetermined sequence.

13. The method of claim 12 wherein the predetermined sequence is determined by determination means.

14. The method of claim 13 including alerting an operator of a status of at least one sensor.

15. The method of claim 1 wherein said at least one evoked potential response signal includes one or more of:

a first latency signal acquired from any of a cochlear, eighth nerve or eighth nerve compound action potential, said signal having a duration substantially of 0 to 5 ms (milliseconds);

a second fast latency signal acquired from any of an auditory brainstem response, wave I, wave 11, wave 111, wave IVY or wave V, said signal having a duration substantially of 2 to 20 ms;

a third early cortical or middle latency signal said signal including any of MLAEP (middle latency audio evoked potential), Na, Pa, TP41, Pb, or Nb, said signal having a duration substantially of 10 to 100 m sec;

a fourth slow latency vertex audio evoked potential signal including any of P1, N1, P2, or N2 having a duration substantially of 50 to 300 ms; and

a fifth contingent potential processing signal (PCP), including any one of or a combination of mismatched negativity, Nd, N2b, P3a, P3b, N400, or P600.