Closed-Loop Neural Stimulation with Out-of-Compliance Current Limit Estimation
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Solution Overview
Problem
Neural stimulation devices face challenges in maintaining optimal stimulus intensity due to electrode migration and postural changes, leading to ineffective or painful therapy, and out-of-compliance events that limit the range of test stimuli during programming and therapy.
Innovation Solution
The method estimates the out-of-compliance current limit for each stimulus electrode configuration using measured electrode resistances and adjusts stimulus parameters to prevent out-of-compliance events by increasing the current limit or reducing the maximum stimulus current, ensuring effective neural stimulation therapy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stimulus intensity is increased to maintain therapeutic effect, then neural recruitment is improved, but discomfort threshold is exceeded causing painful percepts
Solution Approach 1:
The system employs a feedback controller that continuously monitors the neural response and adjusts stimulus intensity to maintain the response within a therapeutic range. The feedback controller receives the measured intensity of the evoked neural response and adjusts the stimulus intensity parameter accordingly, preventing both sub-therapeutic and supra-therapeutic stimulation that would cause discomfort.
2Stability of the object's composition
If electrode array position is fixed to maintain stable neural recruitment, then therapeutic range is preserved, but electrode migration and postural changes cannot be accommodated
Solution Approach 1:
The feedback controller continuously monitors the intensity of the evoked neural response and adjusts stimulus intensity in real-time to compensate for changes in electrode-to-fibre distance caused by electrode migration or postural changes. This maintains stable neural recruitment despite physical displacement of the electrode array.
Solution Approach 2:
The system dynamically adjusts the stimulus intensity parameter based on real-time measurements of neural response intensity. Rather than using a fixed stimulus intensity, the system adapts the stimulation parameters continuously to maintain optimal therapeutic effect despite changing physiological conditions.
3Reliability
If stimulus intensity is maintained above recruitment threshold to ensure therapeutic effect, then neural activation is sufficient, but out-of-compliance events occur limiting test stimulus range
Solution Approach 1:
The system performs preliminary estimation of the out-of-compliance current limit for each stimulus electrode configuration using measured electrode resistances. By knowing this limit in advance, the feedback controller can adjust stimulus parameters to stay within compliant operation while maintaining effective neural activation, preventing out-of-compliance events before they occur.
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
This approach allows for pre-emptive mitigation of out-of-compliance events, maintaining therapeutic stimulus intensity and reducing the risk of ineffective or painful therapy, thereby improving the efficiency and comfort of neural stimulation.
Implementation Method 1
An electrical pulse of sufficient intensity applied to the target neural fibres by a stimulus electrode causes the depolarisation of neurons in the fibres, which in turn generates an action potential in the fibres
Implementation Method 2
A signal representative of the neural response may be sensed by a measurement electrode in electrical communication with the recruited neural fibres
Implementation Method 3
Feedback control seeks to compensate for relative nerve/electrode movement by controlling the intensity of the delivered stimuli so as to maintain a substantially constant neural recruitment
Data Source
AI summary
In some implementations, the device may include a neural stimulation system having: an implantable closed-loop neural stimulation device for controllably delivering neural stimuli via one or more stimulus electrodes, the device having the one or more stimulus electrodes and a feedback controller configured to adjust a stimulus intensity parameter so as to maintain a measured neural response intensity at a target response intensity; and a processor configured to: estimate an out-of-compliance current limit for each of the one or more stimulus electrodes; estimate a closed-loop current requirement for the implantable closed-loop neural stimulation device; compare the out-of-compliance current limit for each of the one or more stimulus electrodes to the closed-loop current requirement; and take a mitigating action based on the comparison.