Method and apparatus for determining the cerebral state of a patient with fast response
First Claim
1. Apparatus for ascertaining the cerebral state of a patient, including a state resulting from the administration of a drug, said apparatus comprising:
- (a) means for obtaining biopotential signals from the patient, the biopotential signals containing EEG signal data and EMG signal data, the EMG signal data being primarily of a higher frequency than the EEG signal data which is primarily of a lower frequency;
(b) means for analyzing a sample of sequential signal data over a frequency range that is sufficiently wide to include both the EEG and EMG signal data to obtain a measure of the complexity of the signal data, said analyzing means using a length of EEG signal data and effectively using a EMG signal data sample of shorter length than the EEG signal data sample; and
(c) means providing the complexity measure as an indicator of the cerebral state of the patient, said providing means updating said indicator at a repetition rate allowed by a shorter sample length of the EMG signal data to indicate changes in the cerebral state of the patient.
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Abstract
A method and apparatus for ascertaining the cerebral state of a patient. The method/apparatus may find use in ascertaining the depth of anesthesia of the patient. In one embodiment, the entropy of the patient'"'"'s EEG signal data is determined as an indication of the cerebral state. A frequency domain power spectrum quantity is obtained from the patient'"'"'s EMG signal data. The latter quantity can be updated more frequently than the EEG entropy due to its higher frequency. The EEG entropy indication and the EMG power spectrum indication can be combined into a composite indicator that provides an immediate indication of changes in the cerebral state of the patient. In another embodiment, the frequency range over which the entropy of the biopotential signal from the patient is determined is broadened to encompass both EEG signal data and EMG signal data and the entropy so determined used as an indication of the patient'"'"'s cerebral state.
65 Citations
46 Claims
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1. Apparatus for ascertaining the cerebral state of a patient, including a state resulting from the administration of a drug, said apparatus comprising:
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(a) means for obtaining biopotential signals from the patient, the biopotential signals containing EEG signal data and EMG signal data, the EMG signal data being primarily of a higher frequency than the EEG signal data which is primarily of a lower frequency;
(b) means for analyzing a sample of sequential signal data over a frequency range that is sufficiently wide to include both the EEG and EMG signal data to obtain a measure of the complexity of the signal data, said analyzing means using a length of EEG signal data and effectively using a EMG signal data sample of shorter length than the EEG signal data sample; and
(c) means providing the complexity measure as an indicator of the cerebral state of the patient, said providing means updating said indicator at a repetition rate allowed by a shorter sample length of the EMG signal data to indicate changes in the cerebral state of the patient. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for ascertaining the depth of anesthesia of a patient, said method rapidly indicating changes in the hypnotic state of the patient and comprising the steps of:
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(a) obtaining biopotential signals from the patient, the biopotential signals containing EEG signal data and EMG signal data, the EMG signal data being primarily of a higher frequency than the EEG signal data which is primarily of lower frequency;
(b) analyzing a sample of sequential signal data existing in a frequency range extending from a frequency of about 0.5 Hz to a frequency which is above 32 Hz to obtain a measure of the complexity of the signal data, the analysis of the EMG signal data effectively using a sample of shorter length than that of the EEG signal data sample due to the higher frequency of the EMG signal data;
(c) providing the complexity measure as a first indication of the cerebral state of the patient, which indication is suitable for being updated at a repetition rate allowed by a shorter sample length of the EMG signal data to rapidly indicate changes in the cerebral state of the patient;
(d) analyzing a sample of EEG signal data to obtain a complexity measure of the EEG signal data;
(e) providing the complexity measure of the EEG signal data as a second indication of the cerebral state of the patient; and
(f) normalizing the first indication and second indication so that the first indication and second indication are equal in the absence of EMG signal data.
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13. A method for ascertaining the cerebral state of a patient, including a state resulting from the administration of a drug, said method rapidly indicating changes in such state and comprising the steps of:
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(a) obtaining biopotential signals from the patient, the biopotential signals containing EEG signal data and EMG signal data, the EMG signal data being primarily of a higher frequency than the EEG signal data which is primarily of lower frequency;
(b) analyzing a sample of sequential signal data over a frequency range that is sufficiently wide to include both the EEG and EMG signal data to obtain a measure of the complexity of the signal data, the analysis of the EMG signal data effectively using a sample of shorter length than that of the EEG signal data sample due to the higher frequency of the EMG signal data; and
(c) providing the measure as an indication of the cerebral state of the patient, which indication is suitable for being updated at a repetition rate allowed by a shorter sample length of the EMG signal data to rapidly indicate changes in the cerebral state of the patient. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
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Specification