Impedance-Based Stimulation Adjustment for Spinal Cord Devices
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Solution Overview
Problem
Medical devices delivering electrical stimulation, such as spinal cord stimulation, face challenges in maintaining consistent efficacy due to electrode movement relative to target neurons, leading to varying stimulation intensity with patient movement, especially in cervical levels of the spinal cord.
Innovation Solution
A medical device that measures impedance associated with electrodes and adjusts stimulation parameters, like amplitude, based on patient-specific relationships determined through impedance measurement and feedback, to maintain constant perceived stimulation intensity despite electrode movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrodes are implanted epidurally to treat spinal cord stimulation, then the device can deliver stimulation to target neurons, but electrode movement relative to target neurons occurs during patient movement, causing varying stimulation intensity
Solution Approach 1:
The system measures impedance values from the electrodes and uses this feedback to automatically adjust stimulation parameters. The impedance measurements provide real-time information about electrode-tissue interface conditions, enabling the system to compensate for electrode movement and maintain consistent stimulation efficacy despite position changes.
Solution Approach 2:
The system dynamically changes stimulation parameters (amplitude, pulse width, frequency) based on measured impedance values. When impedance changes indicate electrode movement or tissue condition changes, the system adjusts parameters to maintain optimal stimulation, resolving the contradiction between reliable efficacy and position stability.
2Ease of operation
If stimulation parameters are adjusted to maintain constant intensity, then patient comfort improves, but device complexity increases due to impedance measurement and parameter adjustment mechanisms
Solution Approach 1:
The system performs self-adjustment by automatically measuring impedance and modifying stimulation parameters without requiring external intervention. The device monitors its own performance through impedance measurements and autonomously optimizes stimulation, improving patient comfort while keeping the control system relatively simple.
Solution Approach 2:
The impedance measurement system provides continuous feedback about electrode-tissue interface conditions, enabling automatic parameter adjustment. This feedback loop allows the device to maintain optimal stimulation and patient comfort through self-regulation rather than complex external control systems.
3Reliability
If impedance measurement is used to adjust stimulation parameters, then stimulation intensity remains constant despite electrode movement, but measurement precision requirements increase
Solution Approach 1:
The system uses impedance parameter changes as indicators of electrode-tissue interface conditions and adjusts stimulation parameters accordingly. By monitoring impedance variations and responding with appropriate parameter changes, the system maintains consistent stimulation intensity without requiring ultra-precise impedance measurements, as long as the measurements are sufficient to detect meaningful changes.
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 device ensures substantially constant stimulation intensity across various activities and postures, particularly beneficial for cervical spinal cord stimulation by using patient-specific impedance relationships to adjust parameters, thereby enhancing treatment efficacy and patient comfort.
Implementation Method 1
measures impedances associated with the electrodes
Implementation Method 2
deliver electrical stimulation in order treat a variety of ailments or symptoms
Data Source
AI summary
Techniques for adjusting stimulation are disclosed. A medical device measures an impedance associated with one or more electrodes, e.g., the impedance presented to the medical device by a total electrical circuit that includes the one or more electrodes, the conductors associated with the electrodes, and tissue proximate to the electrodes. The medical device stores at least one patient-specific relationship between impedance and a stimulation parameter, and adjusts the value of the stimulation parameter based on the measured impedance according to the relationship. The medical device may store multiple relationships, and select one the relationships based on, for example, an activity level of the patient, posture of the patient, or a current stimulation program or electrode combination used to deliver stimulation. By adjusting a stimulation parameter, such as amplitude, according to such a relationship, the stimulation intensity as perceived by the patient may be kept substantially constant.