Hysteresis Compensation for ECAP Detection in Neural Stimulation
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Solution Overview
Problem
Medical devices delivering electrical stimulation face challenges in maintaining effective therapy due to changes in the distance between implanted electrodes and target nerves caused by patient movement, leading to variations in neural recruitment and sensitivity to stimulation intensity, resulting in potential overstimulation or understimulation.
Innovation Solution
A system that adjusts stimulation parameter values based on evoked compound action potential (ECAP) signals, using different gain values for increasing and decreasing stimulation intensity, and accounting for specific posture states to maintain optimal neural recruitment and reduce discomfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the stimulation parameter value is increased to maintain effective therapy when electrode-nerve distance decreases, then neural recruitment is improved, but patient discomfort and overstimulation increase
Solution Approach 1:
The system uses ECAP signal characteristic values as feedback to dynamically adjust stimulation parameter values. When the characteristic value indicates decreased electrode-nerve distance, the system automatically reduces stimulation intensity to prevent overstimulation and discomfort while maintaining therapeutic efficacy.
Solution Approach 2:
The stimulation parameter values are made dynamic rather than fixed, allowing real-time adjustment based on detected ECAP characteristic values. This enables the system to adapt to changing electrode-nerve distances caused by patient movement, posture changes, or tissue settling.
2Object-affected harmful factors
If the stimulation parameter value is decreased to reduce discomfort when electrode-nerve distance decreases, then patient comfort is improved, but therapeutic efficacy is reduced
Solution Approach 1:
The system continuously monitors ECAP characteristic values and adjusts stimulation parameters in real-time. When the characteristic value indicates increased electrode-nerve distance, the system automatically increases stimulation intensity to maintain therapeutic efficacy while avoiding unnecessary discomfort from excessive stimulation.
Solution Approach 2:
The system dynamically adjusts stimulation parameters based on real-time ECAP feedback, allowing it to optimize the balance between comfort and efficacy for each moment rather than using fixed conservative settings that would compromise therapeutic effectiveness.
3Measurement precision
If different gain values are used for increasing and decreasing stimulation intensity, then adjustment precision is improved, but system complexity increases
Solution Approach 1:
The system applies different gain values (local properties) depending on whether the ECAP characteristic value is above or below the target threshold. This local differentiation allows precise control in each direction while keeping the overall control logic relatively simple through clear conditional branching.
Data Source
AI summary
Systems, devices, and techniques are described for adjusting electrical stimulation based on detected ECAPs. In one example, a medical device includes processing circuitry configured to control stimulation circuitry to deliver a first electrical stimulation pulse and sensing circuitry to detect, after delivery of the first electrical stimulation pulse, an ECAP signal. The processing circuitry may be configured to determine a characteristic value of the ECAP signal, determine an ECAP differential value that indicates whether the characteristic value of the ECAP signal is one of greater than a selected ECAP characteristic value or less than the selected ECAP characteristic value, determine, based on the ECAP differential value, a gain value, determine, based on the gain value, a parameter value that at least partially defines a second electrical stimulation pulse, and control the stimulation circuitry to deliver the second electrical stimulation pulse according to the parameter value.