Posture-Responsive Neurostimulation With ECAP Feedback Control
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Solution Overview
Problem
Existing neuromodulation systems face challenges in maintaining effective neural recruitment while minimizing energy expenditure and avoiding uncomfortable side effects due to electrode migration and postural changes, which alter neural recruitment and require frequent battery charging.
Innovation Solution
An implantable device with electrodes and measurement circuitry to record neural compound action potentials, using a control unit to estimate patient posture and implement a feedback loop to maintain a constant neural recruitment by adjusting stimulus parameters based on measured ECAP characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stimuli amplitude is increased to maintain neural recruitment, then therapeutic effect is improved, but energy consumption increases and uncomfortable sensations occur
Solution Approach 1:
The system employs a feedback mechanism where the measured ECAP characteristic is compared to a reference value, and the stimulus parameter is adjusted based on the difference. This closed-loop control maintains consistent neural recruitment while minimizing energy expenditure by only applying the necessary stimulus amplitude.
Solution Approach 2:
The system dynamically changes the stimulus parameter (amplitude, pulse width, or frequency) based on measured ECAP characteristics. By adjusting these parameters in response to postural changes and electrode migration, the system maintains therapeutic effect while optimizing energy consumption.
2Reliability
If stimuli amplitude is increased to compensate for electrode migration, then neural recruitment is maintained, but uncomfortable or painful sensations occur
Solution Approach 1:
The feedback loop continuously monitors ECAP characteristics and adjusts stimulus parameters to maintain consistent neural recruitment. This prevents over-stimulation that would cause uncomfortable sensations while compensating for electrode migration and postural changes.
Solution Approach 2:
The system dynamically adjusts stimulus parameters in real-time based on measured ECAP characteristics. This dynamic adaptation allows the system to maintain therapeutic effect while avoiding uncomfortable sensations caused by static high-amplitude stimulation.
3Reliability
If stimuli are applied continuously at high frequency, then pain relief is sustained, but battery lifetime is reduced
Solution Approach 1:
The feedback mechanism optimizes stimulus delivery by adjusting parameters based on measured ECAP characteristics. This ensures sustained pain relief while minimizing energy consumption, thereby extending battery lifetime without compromising therapeutic effect.
Solution Approach 2:
The system changes stimulus parameters (amplitude, pulse width, frequency) based on measured ECAP characteristics and postural information. By optimizing these parameters in real-time, the system maintains effective pain relief while reducing overall energy consumption to extend battery lifetime.
4Reliability
If feedback control is implemented to maintain constant ECAP amplitude, then neural recruitment consistency is improved, but data storage requirements exceed device capacity
Solution Approach 1:
The system extracts only the essential feedback information (ECAP characteristic measurements and computed posture estimates) rather than storing complete raw data. This selective extraction maintains neural recruitment consistency while minimizing data storage requirements to fit within device constraints.
Solution Approach 2:
Instead of using raw ECAP waveforms for feedback control, the system computes simplified characteristic values (amplitude, area, or peak time) from the raw data. This inversion approach maintains control accuracy while dramatically reducing the storage burden by working with derived parameters rather than complete waveforms.
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 system effectively maintains therapeutic neural recruitment levels while reducing energy consumption and minimizing discomfort by dynamically adjusting stimuli in response to postural changes, extending device lifetime and improving user comfort.
Implementation Method 1
measurement circuitry for recording a neural compound action potential signal sensed at the one or more sense electrodes
Data Source
AI summary
An implantable device is configured to control application of a neural stimulus as defined by a stimulus parameter; measure via the measurement circuitry a characteristic of a neural compound action potential response evoked by the stimulus; and compute, using the stimulus parameter and the measured characteristic of the evoked neural compound action potential response, a characteristic of an evoked response that would be obtained from the neural stimulus if the patient were in a reference posture. A posture of the patient can be estimated from the computed characteristic and/or the computed characteristic can be used as a feedback variable of a feedback loop. Multidimensional histograms of datasets comprising at least one of the stimulus parameter and a feedback variable can be stored.