Implantable Device Stimulation Mode Switching for Energy Efficiency
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Solution Overview
Problem
Implantable medical devices face inefficiencies and reduced service life due to constant current mode operation, which is less efficient than constant voltage mode, and requires costly clinician visits for re-programming to switch between modes based on tissue impedance stability.
Innovation Solution
An implantable medical device that automatically switches from constant current to constant voltage mode based on detected tissue impedance stability, using initial stimulation parameters and measured voltage amplitude to maintain effective charge delivery without requiring clinician intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant current mode is used to address tissue impedance instability, then effective charge delivery is maintained, but device efficiency decreases and service life is reduced
Solution Approach 1:
The device dynamically switches between constant current mode (during fibrosis when impedance is unstable) and constant voltage mode (after fibrosis completes when impedance is stable). This dynamic adaptation allows the system to maintain effective charge delivery during the critical early period while achieving higher efficiency during long-term operation, thus resolving the contradiction between reliability and energy loss.
Solution Approach 2:
The system changes the operational parameter from constant current to constant voltage based on tissue impedance stability detection. By monitoring impedance over time and switching modes accordingly, the device optimizes the balance between ensuring effective charge delivery and minimizing energy loss, thereby extending service life while maintaining therapeutic effectiveness.
2Reliability
If constant current mode is used initially, then tissue impedance instability is managed, but clinician visits for re-programming are required
Solution Approach 1:
The device performs self-diagnosis by monitoring tissue impedance stability and automatically determines when the transition from constant current to constant voltage mode is appropriate. This self-service capability eliminates the need for clinician intervention and manual re-programming, allowing the device to autonomously optimize its operation while maintaining reliable impedance management.
Solution Approach 2:
The system continuously monitors tissue impedance and uses this feedback to automatically determine the optimal switching point between operational modes. This closed-loop feedback mechanism replaces the open-loop approach requiring clinician judgment and manual re-programming, thereby improving ease of operation while maintaining reliable impedance management.
3Reliability
If constant current mode is used long term, then tissue impedance instability is addressed, but service life is significantly reduced
Solution Approach 1:
The device operates in constant current mode during the initial fibrosis period and then transitions to constant voltage mode for long-term operation. This periodic action pattern ensures that the less efficient but more reliable constant current mode is used only when necessary for impedance management, while the efficient constant voltage mode extends service life during the stable long-term phase.
Data Source
AI summary
Implantable medical devices switch from a constant current mode of operation to a constant voltage mode of operation. The switching may be based on the device determining that tissue impedance stability has occurred. The determination may be a measurement of output voltage stability of the constant current source or based on other factors such as an amount of time that has elapsed. The switching may be as the result of an externally generated request such as by a clinician via an external device. The implantable medical device may begin constant voltage mode by utilizing stimulation parameters based on those initially programmed for constant current mode and based upon a measurement of voltage amplitude being output by the constant current source prior to the switch.