Methods and apparatus for monitoring consciousness

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.

1 . An apparatus for acquiring physiological data from a living being for determining the state of consciousness of said living being, comprising:
 means for acquiring at least one continuous biosignal;   means for stimulating at least one evoked potential signal in said being;   means for acquiring said at least one evoked potential biosignal;   means for calculating at least two indices from each acquired biosignal and selecting an index from the calculated indices to represent the state of consciousness from the living being wherein a first of said indices is derived from a transformation of raw signal data according to a first transformation method and the second and subsequent of said indices is derived from a transformation of raw signal data according to a different transformation method or methods from said first transformation method;   wherein said first means for acquiring said first biosignal and said means for acquiring at least one evoked signal includes a single means.   
     
     
         2 . The apparatus according to  claim 1 , wherein the at least one biosignal is any one of, or a combination of, at least one EEG signal or at least one muscular activation signal. 
     
     
         3 . The apparatus according to  claim 2 , wherein the at least one muscular activation signal is a measure of eyelid movement. 
     
     
         4 . The apparatus according to  claim 2 , wherein the EEG signal is a continuous signal. 
     
     
         5 . The apparatus according to  claim 2 , including means for deriving said evoked potential signal from the EEG signal. 
     
     
         6 . The apparatus according to  claim 1 , wherein the means for a acquiring the at least one continuous biosignal or means for acquiring the at least one evoked potential signal includes at least one electrode sensor. 
     
     
         7 . The apparatus according to  claim 1 , including means for monitoring the at least one sensor for signal integrity. 
     
     
         8 . The apparatus according to  claim 1 , including means for monitoring the at least one sensor for signal quality. 
     
     
         9 . The apparatus according to  claim 1 , wherein the means for acquiring the at least one continuous biosignal or means for acquiring the at least one evoked potential signal includes at least one disposable or semi-disposable sensor. 
     
     
         10 . The apparatus according to  claim 9 , wherein said at least one disposable or semi-disposable sensor includes means for activating an electrical energy source. 
     
     
         11 . The apparatus according to  claim 10 , wherein the means for activating said energy source includes the packaging of said electrical energy source. 
     
     
         12 . The apparatus according to  claim 1 , wherein the means to acquire the at least one biosignal is an electrode sensor activatable in response to pressure from an operator or user of said apparatus. 
     
     
         13 . The apparatus according to  claim 1 , wherein the means for stimulating the evoked potential signal stimulates any one or a combination of somatosensory, auditory, or visual evoked response. 
     
     
         14 . The apparatus according to  claim 13 , wherein the means for stimulating said auditory evoked response signal is a cochlear microphone. 
     
     
         15 . The apparatus according to  claim 13 , whereby said auditory means 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, 40 Hz ASSR, or less than 20 Hz ASSR. 
     
     
         16 . The apparatus according to  claim 1 , including means for displaying the functional or operational status of any sensor. 
     
     
         17 . The apparatus according to  claim 1 , wherein the means for inducing an auditory evoked potential response signal includes means for producing any one of or a combination of evoked response paradigms including:
 at least one type of click stimulus according to an individual patient;   at least one response at spaced intervals within the at least one type of click stimulus;   sounds with characteristics corresponding to white noise or speech;   oddball sound characteristics;   unusual sound characteristics;   masked noise sounds;   unanticipated noise sounds;   composite sounds;   familiar sounds; and   recognisable sounds in reference to said patient;   wherein a combination of any sound stimulus is generated according to a predetermined sequence.   
     
     
         18 . The apparatus according to  claim 17 , wherein the predetermined sequence is determined by determination means incorporated within the apparatus. 
     
     
         19 . The apparatus according to  claim 1 , including means for alerting an operator or user of the status of at least one sensor.