ECAP-Guided Sub-Threshold Stimulation for Consistent Therapy
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Solution Overview
Problem
Existing medical devices struggle to maintain consistent electrical stimulation therapy delivery as the distance between electrodes and target tissue changes due to patient movement or lead migration, leading to inconsistent therapy efficacy and potential side effects.
Innovation Solution
A medical device adjusts stimulation parameters based on evoked compound action potential (ECAP) signals to deliver sub-threshold stimulation therapy, maintaining consistent therapy levels by periodically determining stimulation thresholds and interleaving control and informed pulses to sense ECAPs without patient perception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If supra-threshold stimulation is delivered to ensure therapeutic efficacy, then symptom relief is achieved, but patient perception of uncomfortable sensations and side effects increases
Solution Approach 1:
The patent replaces direct sensory-based stimulation control with a physiological response-based control system. Instead of relying on patient feedback about sensation intensity, the system uses ECAP detection to objectively measure neural activation and automatically adjusts stimulation parameters to maintain therapeutic effect below the perception threshold.
Solution Approach 2:
The system implements a closed-loop feedback mechanism where ECAP signals are continuously monitored and used to adjust stimulation parameters. The processing circuitry compares detected ECAP amplitudes to target thresholds and automatically modifies pulse amplitude, pulse width, or frequency to maintain optimal therapeutic effect while preventing uncomfortable sensations.
2Object-affected harmful factors
If stimulation parameters are adjusted to eliminate patient perception, then uncomfortable sensations are reduced, but therapeutic efficacy may be compromised
Solution Approach 1:
The patent substitutes patient subjective sensation reporting with objective ECAP-based neural activation measurement. This allows the system to maintain therapeutic efficacy through physiological markers rather than relying on patient perception, enabling operation below the awareness threshold while preserving treatment effectiveness.
3Measurement precision
If ECAP sensing is performed after every stimulation pulse, then accurate threshold detection is achieved, but patient perception of stimulation occurs
Solution Approach 1:
The patent divides stimulation into separate functional components: test pulses for ECAP detection and therapy pulses for treatment. By segmenting the pulse train and applying different parameters to each component, the system can accurately detect thresholds using test pulses while delivering comfortable therapy pulses below the perception threshold.
Solution Approach 2:
Different portions of the pulse train are assigned different characteristics. Test pulses use higher amplitude or longer duration to ensure detectable ECAPs for accurate threshold measurement, while therapy pulses use lower intensity parameters to remain imperceptible. This local differentiation allows simultaneous achievement of measurement precision and patient comfort.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures consistent therapy delivery by reducing side effects and maintaining therapeutic efficacy despite changes in electrode-tissue distance, providing relief for symptoms like chronic pain without patient perception of stimulation.
Implementation Method 1
An evoked compound action potential (ECAP) is synchronous firing of a population of neurons which occurs in response to the application of a stimulus including, in some cases, an electrical stimulus by a medical device.
Data Source
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AI summary
Systems, devices, and techniques are described for determining stimulation parameters based on one or more stimulation thresholds (e.g., a perception threshold or a detection threshold). In one example, a medical device includes sensing circuitry configured to sense one or more ECAP signals, wherein the sensing circuitry is configured to sense each ECAP signal of the one or more ECAPs elicited by a respective control pulse of a plurality of control pulses, and the medical device includes processing circuitry configured to determine, based on the one or more ECAP signals, a stimulation level for the plurality of control pulses that achieves a stimulation threshold, determine, based on the stimulation level, a value of a stimulation parameter that at least partially defines a plurality of therapy pulses of electrical stimulation therapy, and control stimulation generation circuitry to deliver the electrical stimulation therapy according to the value of the stimulation parameter.