Posture-Dependent Neurostimulation Using Accelerometer and Impedance Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing implantable stimulators fail to adequately adjust neurostimulation parameters based on subtle changes in patient body positioning, such as differences between standing and seated positions with varying orientations, leading to inadequate pain relief for some patients.
Innovation Solution
The use of a 3-axis accelerometer and lead impedance sensors to provide orientation and impedance data, which are processed into impedance vectors to adjust electrical stimulation parameters, allowing for more precise adaptation to the patient's current body position, including interpolation or lookup table methods for new positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If orientation sensors (accelerometer) are used to automatically adjust stimulation based on patient orientation, then stimulation adjustment is automated and simplified, but the system fails to adequately distinguish between different body positions with the same detected orientation (e.g., standing facing forward vs. seated turned rearwardly)
Solution Approach 1:
The patent combines multiple sensing modalities (accelerometer for orientation detection and impedance sensors for tissue characterization) into a unified stimulation control system. By merging these different measurement approaches, the system achieves both automated operation and improved body position discrimination capability, resolving the contradiction between automation extent and measurement precision.
Solution Approach 2:
The patent introduces impedance measurement as an intermediary parameter that mediates between orientation detection and stimulation control. The impedance data serves as an additional indicator that helps distinguish between different body positions that have identical accelerometer readings, thereby improving measurement precision while maintaining automation.
2Device complexity
If stimulation parameters are adjusted based on orientation data alone, then the control system remains simple, but the stimulation adequacy decreases for patients requiring differentiation between subtle body positioning changes
Solution Approach 1:
The patent implements a dynamic control system that adapts stimulation parameters based on real-time impedance measurements. The system dynamically adjusts stimulation not only based on static orientation data but also on changing impedance values that reflect subtle body position changes, thereby improving reliability without excessive complexity increase.
Solution Approach 2:
The patent adds impedance measurement as an additional dimension to the control space. Instead of relying solely on orientation data (one dimension), the system now considers both orientation and impedance (two dimensions), enabling better discrimination of body positions and improved pain relief effectiveness while managing complexity through systematic integration.
3Measurement precision
If multiple sensors and impedance measurements are added to improve body position detection, then position discrimination accuracy improves, but device complexity and power consumption increase
Solution Approach 1:
The patent makes the impedance measurement system multi-functional: it serves both as a body position indicator and as a means to compensate for lead migration and tissue encapsulation. This universal approach allows the additional sensors to contribute to multiple objectives simultaneously, justifying the increased device complexity through enhanced overall system capability.
Solution Approach 2:
The patent utilizes changes in electrical impedance parameters to detect body position changes. By monitoring impedance magnitude and phase changes across different electrode combinations, the system achieves precise body position detection without requiring an excessive number of dedicated sensors, thereby managing device complexity while improving measurement precision.
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 enables more accurate and comfortable neurostimulation by accounting for changes in body position and tissue impedance, improving pain relief and compensating for factors like lead migration and tissue encapsulation.
Implementation Method 1
an orientation sensor 210, e.g., a 3-axis accelerometer, which provides an orientation output signal indicative of the orientation of the orientation sensor 210
Implementation Method 2
a lead impedance sensor 214 configured to determine the impedance(s) of the electrode(s) 208... These impedances are indicative of the impedance (electrical resistance) of the body tissue between the locations from which impedance is measured
Data Source
AI summary
A therapeutic stimulator, e.g., a spinal neurostimulator for pain relief, adapts stimulation delivered to the patient in dependence on measurements of patient orientation (e.g., from a three-axis accelerometer), and also on impedance measurements from leads situated within or upon the patient's body (e.g., from electrodes on neurostimulation leads extending alongside the spine). Since the impedance measurements can provide additional data regarding body positioning, as well as providing data regarding electrode status (such as lead migration, electrode encapsulation, etc.), use of the impedance measurements can provide more refined (and more appropriate) control of delivered stimulation.