Anaesthesia control system
First Claim
1. A method of calculating an index indicative of anaesthetic depth, the method comprising:
- subjecting a patient to a repetitive audio stimulus;
monitoring auditory evoked potentials (AEP) produced by the patient;
providing a signal corresponding to the coarseness of the monitored AEP signal, the coarseness of the signal being a single measure increasing and decreasing with both amplitude and frequency of variations in the signal AEP signal; and
using said signal as said index indicative of anaesthetic depth.
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Abstract
An anaesthesia control system and a method of calculating an index representative of the depth of anaesthesia is disclosed. The method comprises subjecting a patient to a repetitive audio stimulus and monitoring and auditory evoked potentials (AEP) produced by the patient and then recording these auditory evoked potentials using EEG recording means and providing a signal corresponding to the coarseness of the monitored AEP signal and using this signal as an index indicative of anaesthetic depth. The raw AEP signal is divided into a series of sweeps and each sweep is synchronized with the repetitive audio stimulus and sweeps are recorded in sequence to produce a time averaged sweep from which the anaesthetic index is calculated. The anaesthetic index is constantly updated by repeatedly conducting a successive series of sweeps. The system and index signal can be used as part of an anaesthesia control system for regulating the supply of anaesthetic to the patient to maintain the anaesthetic index at a predetermined level.
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Citations
30 Claims
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1. A method of calculating an index indicative of anaesthetic depth, the method comprising:
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subjecting a patient to a repetitive audio stimulus;
monitoring auditory evoked potentials (AEP) produced by the patient;
providing a signal corresponding to the coarseness of the monitored AEP signal, the coarseness of the signal being a single measure increasing and decreasing with both amplitude and frequency of variations in the signal AEP signal; and
using said signal as said index indicative of anaesthetic depth. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A system for calculating an index of anaesthetic depth, the system comprising:
- a signal generator for subjecting patient to a repetitive audio stimulus, electroencephalographic (EEG) recording means for coupling to said patient for recording auditory evoked potential (AEP) signal from the patient, and computer means for receiving said AEP signal, and for processing said AP signals and generating an index signal indicative of the coarseness of the recorded AEP signal, the coarseness of the signal being a single measure increasing and decreasing with both amplitude and frequency variations of the AEP signal, said index signal being representative of the depth of anaesthesia.
- View Dependent Claims (20, 21, 22, 23, 24, 25, 26)
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27. A method of calculating an index indicative of anaesthetic depth, comprising:
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subjecting a patient to a repetitive audio stimulus;
monitoring audio evoked potential (AEP) signals produced by the patient; and
providing a signal corresponding to the coarseness of the monitored AEP signal, and using said signal as an index indicative of anaesthetic depth, the coarseness of the signal being a measure of curvature in the AEP signal.
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28. A method of calculating an index indicative of anaesthetic depth, comprising:
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subjecting a patient to a repetitive audio stimulus;
monitoring audio evoked potential (AEP) signals produced by the patient; and
providing a signal corresponding to the coarseness of the monitored AEP signal, and using said signal as an index indicative of anaesthetic depth, the coarseness of the signal being obtained as a mathematical derivative with respect to time of the AEP signal.
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29. A system for calculating an index of anaesthetic depth, the system comprising:
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a signal generator for subjecting a patient to repetitive audio stimulus;
electroencephalographic (EEG) recording means for coupling to said patient for recording an auditory evoked potential (AEP) signal; and
a processor for processing successive AEP signals to generate and index signal by measuring the coarseness of the recorded AEP signal, the coarseness of the signal being obtained as a mathematical derivative with respect to time of the AEP signal, said index being indicative of the depth of anaesthesia of the patient.
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30. A system for calculating an index of anaesthetic depth, the system comprising:
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a signal generator for subjecting a patient to repetitive audio stimulus;
electroencephalographic (EEG) recording means for coupling to said patient for recording an auditory evoked potential (AEP) signal; and
a processor for processing successive AEP signals to generate and index signal by measuring the coarseness of the recorded AEP signal;
the coarseness of the signal being obtained by differentiating the AEP signal with respect to time, said index being indicative of the depth of anaesthesia of the patient.
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Specification