Alertness and drowsiness detection and tracking system
First Claim
1. A system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia comprising:
- means for acquiring a brain-wave signal having rhythmic components from the subject;
means for selecting components of said brain-wave signal lying in a predetermined range of frequencies including frequencies above 30 Hz;
means responsive to said selecting means for determining a contribution to said brain-wave signal due to said components lying in said range; and
means responsive to said contribution-determining means for producing an output-measure signal indicative of said state of the subject.
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Accused Products
Abstract
A drowsiness detection system constructed according to the invention provides improved performance by preserving and analyzing newly discovered information contained in rhythmic signal components above 30 Hz which the prior art has universally ignored or discarded as "noise." In the first and second embodiments of the invention, one or more analog EEG signals are collected from a subject, appropriately filtered, converted into digital form, and subjected to frequency analysis. Selected signal components from the frequencies above 30 Hz (such as the frequency range 80-420 Hz), which have a high correlation with subject drowsiness, are isolated, and their amplitude, energy, or power contribution to the EEG signal is used to produce a continuous output measure reflecting the subject'"'"'s alertness or drowsiness. The output measure may be compared with a threshold to provide an indication of whether the subject is excessively drowsy. In a third embodiment, the analog EEG signal is supplied to a plurality of analog signal processing channels corresponding to respective predefined frequency ranges. Selected signal components in frequencies above 30 Hz are isolated (in a manner analogous to that of the first and second embodiments), and their amplitude, energy, or power contribution to the EEG signal is used to produce a continuous output measure reflecting the subject'"'"'s alertness or drowsiness.
307 Citations
67 Claims
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1. A system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia comprising:
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means for acquiring a brain-wave signal having rhythmic components from the subject; means for selecting components of said brain-wave signal lying in a predetermined range of frequencies including frequencies above 30 Hz; means responsive to said selecting means for determining a contribution to said brain-wave signal due to said components lying in said range; and means responsive to said contribution-determining means for producing an output-measure signal indicative of said state of the subject.
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2. A system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia comprising:
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means for acquiring a brain-wave signal having rhythmic components from the subject; means for defining a range of frequencies including frequencies above 30 Hz; means for analyzing frequency content of said acquired brain-wave signal responsive to said defined range of frequencies for defining a plurality of frequencies or frequency bands within said range, and for determining for each of said defined frequencies or frequency bands a contribution due to a component of said acquired brain-wave signal at such frequency or within such frequency band; and output-measure-determining means responsive to said frequency analysis means for producing an output signal indicative of said state of the subject.
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3. A system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia comprising:
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means for acquiring a brain-wave signal having rhythmic components from the subject; means for defining a range of frequencies including frequencies above 30 Hz; means for analyzing frequency content of said acquired brain-wave signal responsive to said defined range of frequencies for defining a plurality of frequencies or frequency bands within said range, and for determining for each of said defined frequencies or frequency bands an amplitude or distribution of amplitudes corresponding to a component or components of said acquired brain-wave signal at such frequency or within such frequency band; power determination means for determining for each of said defined frequencies the power contained in said corresponding component or for each of said defined frequency bands the distribution of power contained in said corresponding components; and spectral-grouping means for defining a limited number of spectral groups, each of said spectral groups defining a subrange of said range and including at least one of said defined frequencies or frequency bands; group-energy-determining means responsive to said power determination means and said spectral-grouping means for determining for each of said spectral groups an aggregate energy represented in a plurality of said components corresponding to the defined frequencies or frequency bands included in such group; and output-measure-determining means responsive to said group-energy-determining means for producing an output signal indicative of said state of the subject.
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4. A system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia comprising:
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means for acquiring a brain-wave signal having rhythmic components from the subject; anti-aliasing filter means for substantially removing from said brain-wave signal components outside a first predefined frequency range; means responsive to said brain-wave signal-acquiring means for converting said brain-wave signal into a sequential plurality of digital data elements representing amplitude of said brain-wave signal at a corresponding plurality of discrete times; means for selecting for analysis a limited number of said data elements; means for defining a second range of frequencies including frequencies above 30 Hz; means for analyzing frequency content of said acquired brain-wave signal, said means being operative to define a plurality of frequencies or frequency bands within said second range, and said means also being responsive thereto and to said selected data elements to determine for each such defined frequency or frequency bands an amplitude or distribution of amplitudes of a component or components of said acquired brain-wave signal at that frequency or within that frequency band; power determination means for determining for each of said defined frequencies the power contained in said corresponding component or for each of said defined frequency bands the distribution of power contained in said corresponding components; spectral-grouping means for defining a limited number of spectral groups, each of said spectral groups defining a subrange of said second range and including at least one of said defined frequencies or frequency bands; group-energy-determining means responsive to said power determination means for determining for each of said spectral groups an aggregate energy represented in a plurality of said components corresponding to the defined frequencies or frequency bands included in such group; and output-measure-determining means responsive to said group-energy-determining means for producing an output signal indicative of said state of the subject. - View Dependent Claims (5, 6)
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7. A system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia comprising:
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means for obtaining a brain-wave signal from the subject; subject state analysis means responsive to said brain-wave signal obtained from the subject for; (a) selecting components of said brain-wave signal lying in a first predetermined range of frequencies including frequencies above 30 Hz; (b) determining a contribution to said brain-wave signal due to said components lying in said range; and (c) producing, responsive to at least said determined contribution, an output-measure signal indicative of said state of the subject. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia comprising:
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means for obtaining a brain-wave signal having rhythmic components from the subject over at least a first predetermined range of frequencies including a second predefined range of frequencies including frequencies above 30 Hz; brain-wave signal acquisition means including;
(a) filter means for receiving a representation of said brain-wave signal obtained from said subject, and for substantially attenuating signal components outside a third predefined frequency range and substantially preserving signals within said second predefined subrange; and
(b) conversion means responsive to a representation of said brain-wave signal obtained from the subject for producing a digital representation of said brain-wave signal; andsubject state analysis means responsive to said digital representation of said brain-wave signal for; (a) selecting components of said brain-wave signal lying in said first predetermined range of frequencies including said second predefined range; (b) determining a contribution to said brain-wave signal due to said components lying in said second predefined range; and (c) producing, responsive to at least said determined contribution, an output-measure signal indicative of said state of the subject. - View Dependent Claims (33, 34, 35, 36, 37)
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38. For use with a system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia, said system having means for obtaining a brain-wave signal including rhythmic components from the subject, and conversion means responsive to said brain-wave signal for converting the subject'"'"'s brain-wave signal into a sequential plurality of digital data elements representing amplitude of said brain-wave signal at a corresponding plurality of discrete time intervals, and producing therefrom an output-measure signal indicating said state of the subject;
- the method of determining a threshold value which defines a range of output-measure signal values indicating that the subject is not fully alert, comprising the steps of;
(a) obtaining a sequential plurality of digital data elements representing amplitude of said brain-wave signal of the subject over a period of time, said signal including rhythmic components; (b) selecting a threshold-determination segment of said digital data elements obtained in step (a) corresponding to a period during which the subject is in a state of wakefulness; (c) determining a value of said output-measure signal at each of said plurality of discrete time intervals represented in said threshold-determination segment; (d) determining, for each of said plurality of discrete time intervals represented in said threshold-determination segment, whether said output-measure signal is contaminated by artifact during said discrete time interval; (e) discarding from said output-measure-signal values substantially all output-measure-signal values corresponding to said discrete time intervals during which said output-measure-signal value is contaminated by artifact; (f) determining a known-state baseline output-measure value for the subject as a combined value of substantially all undiscarded output-measure-signal values corresponding to said discrete time intervals represented in said threshold-determination segment; and (g) multiplying said known-state baseline output-measure value for the subject by a predetermined threshold factor to obtain a drowsiness-output-measure threshold value for the subject.
- the method of determining a threshold value which defines a range of output-measure signal values indicating that the subject is not fully alert, comprising the steps of;
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39. For use with a system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia, said system having means for obtaining a brain-wave signal including rhythmic components from the subject, and conversion means responsive to said brain-wave signal for converting said brain-wave signal into a sequential plurality of digital data elements representing amplitude of said brain-wave signal at a corresponding plurality of discrete time intervals, and producing therefrom an output-measure signal indicating said state of the subject;
- the method of determining a threshold value which defines a range of output-measure-signal values corresponding to a selected physiological state of the subject, comprising the steps of;
(a) obtaining a sequential plurality of digital data elements representing amplitude of said brain-wave signal of the subject over a period of time, said signal including rhythmic components; (b) selecting a threshold-determination segment of said digital data elements obtained in step (a) corresponding to a period during which the subject is in a known state along said continuum; (c) determining a value of said output-measure signal at each of said plurality of discrete time intervals represented in said threshold-determination segment; (d) determining, for each of said plurality of discrete time intervals represented in said threshold-determination segment, whether said output-measure signal is contaminated by artifact during said discrete time interval; (e) discarding from said output-measure-signal values substantially all output-measure-signal values corresponding to said discrete time intervals during which said output-measure-signal value is contaminated by artifact; (f) determining a known-state baseline output-measure value for the subject as a combined value of substantially all undiscarded output-measure-signal values corresponding to said discrete time intervals represented in said threshold-determination segment; (g) multiplying said known-state baseline output-measure value for the subject by a predetermined threshold factor to obtain an output-measure threshold value for the subject corresponding to said selected physiological state.
- the method of determining a threshold value which defines a range of output-measure-signal values corresponding to a selected physiological state of the subject, comprising the steps of;
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40. For use in analyzing brain-wave signal information acquired from a human subject, said brain-wave signal information being presented as a sequential plurality of digital data elements representing amplitude of the subject'"'"'s brain-wave signal at a corresponding plurality of discrete time intervals, and producing therefrom an output-measure signal indicating the subject'"'"'s state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia;
- the method of determining a threshold value which defines a range of output-measure-signal values indicating that the subject is not fully alert, comprising the steps of;
(a) obtaining a sequential plurality of digital data elements representing amplitude of a brain-wave signal of the subject over a period of time, said signal including rhythmic components; (b) selecting a threshold-determination segment of said digital data elements obtained in step (a) corresponding to a period during which the subject is in a state of wakefulness; (c) determining a value of said output-measure signal at each of said plurality of discrete time intervals represented in said threshold-determination segment; (d) determining, for each of said plurality of discrete time intervals represented in said threshold-determination segment, whether said output-measure signal is contaminated by artifact during said discrete time interval; (e) discarding from said output-measure-signal values substantially all output-measure-signal values corresponding to said discrete time intervals during which said output-measure-signal value is contaminated by artifact; (f) determining a known-state baseline output-measure value for the subject as a combined value of substantially all undiscarded output-measure-signal values corresponding to said discrete time intervals represented in said threshold-determination segment; and (g) multiplying said known-state baseline output-measure value for the subject by a predetermined threshold factor to obtain a drowsiness output-measure threshold value for the subject.
- the method of determining a threshold value which defines a range of output-measure-signal values indicating that the subject is not fully alert, comprising the steps of;
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41. For use in analyzing brain-wave signal information acquired from a human subject, said brain-wave signal information being presented as a sequential plurality of digital data elements representing amplitude of the subject'"'"'s brain-wave signal at a corresponding plurality of discrete time intervals, and producing therefrom an output-measure signal indicating the subject'"'"'s state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia;
- the method of determining a threshold value which defines a range of output-measure-signal values corresponding to a selected physiological state of the subject, comprising the steps of;
(a) obtaining a sequential plurality of digital data elements representing amplitude of a brain-wave signal of the subject over a period of time, said signal including rhythmic components; (b) selecting a threshold-determination segment of said digital data elements obtained in step (a) corresponding to a period during which the subject is in a known state along said continuum; (c) determining a value of said output-measure signal at each of said plurality of discrete time intervals represented in said threshold-determination segment; (d) determining, for each of said plurality of discrete time intervals represented in said threshold-determination segment, whether said output-measure signal is contaminated by artifact during said discrete time interval; (e) discarding from said output-measure-signal values substantially all output-measure-signal values corresponding to said discrete time intervals during which said output-measure-signal value is contaminated by artifact; (f) determining a known-state baseline output-measure value for the subject as a combined value of substantially all undiscarded output-measure-signal values corresponding to said discrete time intervals represented in said threshold-determination segment; (g) multiplying said known-state baseline output-measure value for the subject by a predetermined threshold factor to obtain an output-measure threshold value for the subject corresponding to said selected physiological state.
- the method of determining a threshold value which defines a range of output-measure-signal values corresponding to a selected physiological state of the subject, comprising the steps of;
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42. For use with a system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia, said system having means for obtaining a brain-wave signal including rhythmic components from the subject, and conversion means responsive to said brain-wave signal for converting said brain-wave signal into a sequential plurality of digital data elements representing amplitude of said brain-wave signal at a corresponding plurality of discrete time intervals, and producing therefrom an output-measure signal indicating said state of the subject;
- the method of detecting whether said brain-wave signal is contaminated by artifact during a selected time period, comprising the steps of;
(a) obtaining an artifact determination segment of data comprising a sequential plurality of digital data elements representing amplitude of selected rhythmic components of said brain-wave signal of the subject over a period of time, said signal including rhythmic components; (b) selecting in turn for further processing a plurality of data windows, each comprising a subset of said artifact determination segment corresponding to an adjacent predefined window interval within said period of time; (c) rejecting as saturated and in its entirety any data window containing a digital data element having at least one value equal to the maximum value which may be produced by said conversion means; (d) analyzing frequency content of said brain-wave signal using said data elements of said data window, thereby determining for each of a plurality of defined frequencies or frequency bands an amplitude or distribution of amplitudes corresponding to a component or components of said brain-wave signal at such defined frequency or within such frequency band; (e) determining for each of said defined frequencies power represented in said corresponding components or for each of said defined frequency bands a distribution of power represented in said corresponding components; (f) defining at least one spectral group, each of said spectral groups comprising a group of frequencies which may be present in said brain-wave signal and including at least one of said defined frequencies or frequency bands; (g) determining for each of said spectral groups an aggregate energy represented in a plurality of said components corresponding to the frequencies included in such group; (h) determining a combined value of said aggregate energy present in a plurality of said spectral groups over a plurality of said data windows in said artifact determination segment; (i) multiplying said combined value of said aggregate energy by a predetermined artifact threshold factor to produce an artifact threshold value; and (j) comparing said aggregate energy for each data window to said artifact threshold value, and identifying as contaminated by artifact each window interval in which the corresponding aggregate energy exceeds said artifact threshold value. - View Dependent Claims (43, 44, 45)
- the method of detecting whether said brain-wave signal is contaminated by artifact during a selected time period, comprising the steps of;
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46. For use in analyzing brain-wave signal information acquired from a human subject, said brain-wave signal information being presented as a sequential plurality of digital data elements representing amplitude of the subject'"'"'s brain-wave signal at a corresponding plurality of discrete time intervals, said digital data elements being derived from said brain-wave signal through a conversion process, and producing therefrom an output-measure signal indicating the subject'"'"'s state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia;
- the method of detecting whether said brain-wave signal data corresponding to a selected time period is contaminated by artifact, comprising the steps of;
(a) obtaining an artifact determination segment of data comprising a sequential plurality of digital data elements representing amplitude of said brain-wave signal of the subject over a period of time, said signal including rhythmic components; (b) selecting in turn for further processing a plurality of data windows, each comprising a subset of said artifact determination segment corresponding to an adjacent predefined window interval within said period of time; (c) rejecting as saturated and in its entirety any data window containing a digital data element having at least one value equal to a maximum value which may be produced in said conversion process; (d) analyzing frequency content of said brain-wave signal using said data elements of said data window, thereby determining for each of a plurality of defined frequencies or frequency bands an amplitude or distribution of amplitudes corresponding to a component or components of said brain-wave signal at such defined frequency or within such frequency band; (e) determining for each of said defined frequencies power represented in said corresponding components or for each of said defined frequency bands a distribution of power represented in said corresponding components; (f) defining at least one spectral group, each of said spectral groups comprising a group of frequencies which may be present in said brain-wave signal and including at least one of said defined frequencies or frequency bands; (g) determining for each of said spectral groups an aggregate energy represented in a plurality of said components corresponding to the frequencies included in such group; (h) determining a combined value of said aggregate energy present in a plurality of said spectral groups over a plurality of said data windows in said artifact determination segment; (i) multiplying said combined value of said aggregate energy by a predetermined artifact threshold factor to produce an artifact threshold value; and (j) comparing said aggregate energy for each data window to said artifact threshold value, and identifying as contaminated by artifact each window interval in which the corresponding aggregate energy exceeds said artifact threshold value.
- the method of detecting whether said brain-wave signal data corresponding to a selected time period is contaminated by artifact, comprising the steps of;
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47. For use with a system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia, said system having means for obtaining a brain-wave signal including rhythmic components from the subject, and conversion means responsive to said brain-wave signal for converting said brain-wave signal into a sequential plurality of digital data elements representing amplitude of said brain-wave signal at a corresponding plurality of discrete time intervals, and producing therefrom an output-measure signal indicating said state of the subject;
- the method of producing said output-measure signal, comprising the steps of;
(a) obtaining selected rhythmic components of said brain-wave signal from the subject, said signal including rhythmic components; (b) defining at least one range of frequencies including frequencies above 30 Hz; (c) for each such defined range, determining a contribution to said brain-wave signal due to components of said signal at frequencies lying within that defined range; and (d) determining said output-measure signal responsive to said contributions to said brain-wave signal determined for a plurality of said defined ranges in combination. - View Dependent Claims (48, 49, 50, 51, 52, 53, 54)
- the method of producing said output-measure signal, comprising the steps of;
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55. For use in analyzing brain-wave signal information acquired from a human subject, said brain-wave signal information being presented as a sequential plurality of digital data elements representing amplitude of said subject'"'"'s brain-wave signal at a corresponding plurality of discrete time intervals, said signal including rhythmic components, said digital data elements being derived from said brain-wave signal through a conversion process, and producing therefrom an output-measure signal indicating the subject'"'"'s state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia;
- the method of producing said output-measure signal, comprising the steps of;
(a) analyzing frequency content of said brain-wave signal including rhythmic components using said digital data elements, thereby determining for each of a plurality of defined frequencies or frequency bands an amplitude or amplitude distribution corresponding to a component or components of said brain-wave signal at such frequency or within such frequency band; (b) defining at least one range of frequencies including frequencies above 30 Hz; (c) for each such defined range, determining a contribution to said brain-wave signal due to components of said signal at frequencies lying within that defined range; and (d) determining said output-measure signal responsive to said contributions to said brain-wave signal determined for a plurality of said defined ranges in combination. - View Dependent Claims (56)
- the method of producing said output-measure signal, comprising the steps of;
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57. A system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia comprising:
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means for acquiring an electrical brain-wave signal including rhythmic components from the subject; at least one signal-processing channel means; each such signal-processing channel means being associated with a respective predefined range of frequencies; at least one of said signal-processing channel means being associated with a range of frequencies including frequencies above 30 Hz; each such signal-processing channel means having;
means for receiving said acquired brain-wave signal;
means for substantially limiting response of said signal-processing channel to its associated predefined range of frequencies; and
means for determining a contribution to said brain-wave signal due to components thereof lying within said associated predefined range of frequencies;and means for receiving from a plurality of such signal-processing channel means respective signals representing said determined contributions and for responsively determining an output-measure signal indicative of said state of the subject. - View Dependent Claims (58, 59, 60, 61, 62, 63, 64)
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65. A system adapted to measure in a human subject a state along a continuum relating to alertness, drowsiness, sleep, unconsciousness, or anesthesia comprising:
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means for acquiring a brain-wave signal including rhythmic components from the subject; means for selecting components of said brain-wave signal lying in a predetermined range of frequencies including frequencies above 30 Hz; and means responsive to components of said signal corresponding to frequencies lying in said range for producing an output-measure signal indicative of said state of the subject; said means for producing said output-measure signal being adapted to modify its response when artifact is present in said brain-wave signal. - View Dependent Claims (66, 67)
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Specification