Nerve evoked potential measurement system using chaotic sequences for noise rejection
First Claim
1. An evoked potential measurement system in an implantable nerve stimulator apparatus, comprising:
- stimulus generator means for generating and delivering stimulus pulses to a first location on a trunk of nerve fibers, having chaotic sequence means for controlling said generator means to generate said stimulus pulses in a chaotic sequence with random intervals,electrode means for sensing evoked signals in said nerve fibers at a second location on said trunk, and circuit means for processing said sensed evoked signals,sync means for synchronizing the timing of the operation of said circuit means with the timing of generating said stimulus pulses, andmeasure means operative after each said stimulus pulse for obtaining from said processed signals a measure of the sensed evoked signals corresponding to said each stimulus pulse.
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Abstract
There is provided a measurement system for measuring signals evoked in response to stimulus pulses applied to a nerve, muscle or like physiological portion of a patient. The measurement system is characterized by delivering stimulus pulses at randomly generated intervals, and enabling the sense circuitry to track the timing of the stimulus pulse generation so as to aid in discriminating the evoked response pattern from surrounding noise. Specifically, after each stimulus pulse a delay is timed out for a time corresponding to the expected latency between the delivered pulse and the arrival of the evoked response at another location. The delay signal is then used to initiate time out of a window which controls operation of the sensing circuit for a window duration corresponding to when the evoked response pattern is appearing. Limiting the sensing operation to the window duration enables tracking of the response pattern, and minimizes power consumption. The sensed evoked response signals are further processed to provide control signals for adjustment of the delay and window, thereby optimizing the sensing operation. The measurement system is suitably part of a larger implantable stimulus system, which includes the ability to adjust pulse-to-pulse interval, or rate, and also pulse output level as a function of measured evoked response patterns. In a further embodiment, the stimulus system involves steering of stimulus pulses to selected nerve fibers or muscle tissue, and the measurement system provides feedback for adjusting the steering parameters.
150 Citations
24 Claims
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1. An evoked potential measurement system in an implantable nerve stimulator apparatus, comprising:
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stimulus generator means for generating and delivering stimulus pulses to a first location on a trunk of nerve fibers, having chaotic sequence means for controlling said generator means to generate said stimulus pulses in a chaotic sequence with random intervals, electrode means for sensing evoked signals in said nerve fibers at a second location on said trunk, and circuit means for processing said sensed evoked signals, sync means for synchronizing the timing of the operation of said circuit means with the timing of generating said stimulus pulses, and measure means operative after each said stimulus pulse for obtaining from said processed signals a measure of the sensed evoked signals corresponding to said each stimulus pulse. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An implantable system for stimulating patient nerve fibers, comprising:
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controllable stimulus means for generating and delivering nerve stimulus pulses of controllable rate and output level to a first patient nerve location, said generator normally operating at a controllable rate and output level; evoked potential measurement means operative during a test period for obtaining measures of evoked potentials produced by said delivered pulses at a sense location, having chaotic sequence means for controlling said generator to generate said stimulus pulses at substantially random intervals, sense means for sensing and processing potentials evoked by said delivered stimulus pulses at a said sense location, said sense means having circuitry for processing said potentials, window means for controlling said circuitry to process said evoked signals only during a window of time following each said stimulus pulse, said window means having delay means for delaying the start of said window by a delay with respect to each said stimulus pulse, measure means for obtaining a measure of the evoked potentials sensed by said sensing means during each said window; and adjust means for adjusting one or more parameters of said stimulus pulses as a function of said measures. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A system for measuring the responses of a patient body portion to applied stimulus pulses, comprising:
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controllable pulse generator means for generating and delivering stimulus pulses to a first location of said body portion, having random control means for controlling generation of said stimulus pulses at random pulse-to-pulse intervals, delay means for generating a delay signal at a delay following each said stimulus pulse, window means for generating a timing window initiated by each said delay signal, and sense means for sensing, at a second location of said body portion, signals evoked by said stimulus pulses, circuit means for processing said sensed signals, and on-off means for turning said circuit means on only during each said timing window, whereby said processing is time synchronized to said random pulse-to-pulse intervals. - View Dependent Claims (17)
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18. A method of measuring evoked responses to stimulus pulses applied to nerves of a patient, comprising:
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generating stimulus pulses with random pulse-to-pulse intervals, and delivering said pulses to a first patient nerve location, generating a window enable signal in timed relation to the delivery of each said stimulus pulse, sensing signals evoked by said stimulus pulses at a second nerve patient location, and processing said sensed signals only during each said window enable signal. - View Dependent Claims (19, 20, 21, 22, 23)
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24. A system for automatically controlling stimulation of nerve fibers, comprising:
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stimulating means for stimulating nerve fibers, determining means for determining characteristics of evoked responses in said nerve fibers due to said stimulating, selecting means for selecting excitation of certain nerve fibers as a function of said determined characteristics, and controlling means for controlling said stimulus means so as to selectively excite said selected certain nerve fibers.
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Specification