Monophasic Pulse Waveforms with Passive Charge Recovery for SCS
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Solution Overview
Problem
Spinal Cord Stimulation (SCS) therapy often causes paresthesia, a sensation that can be uncomfortable for patients, and achieving sub-perception therapy without paresthesia is challenging, especially when using higher-frequency stimulation which drains the implantable pulse generator's battery quickly.
Innovation Solution
The use of new waveforms in the implantable pulse generator (IPG) or external trial stimulator (ETS) that mimic the functionality of actively-driven biphasic pulses by interleaving monophasic pulses with passive charge recovery periods, allowing for effective stimulation at lower frequencies and reducing battery drain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher-frequency stimulation is used to achieve sub-perception therapy without paresthesia, then pain relief effectiveness is improved, but battery drain increases
Solution Approach 1:
The patent employs periodic monophasic pulses with alternating polarities delivered at lower frequencies (e.g., 1-100 Hz) combined with passive charge recovery periods. This periodic action allows the tissue capacitance to charge during the monophasic pulse and discharge during the passive recovery period, achieving sub-perception therapy without requiring continuous high-frequency stimulation, thereby reducing battery consumption while maintaining pain relief effectiveness.
2Duration of action of stationary object
If monophasic pulses with passive charge recovery are used, then battery life is extended, but waveform complexity increases
Solution Approach 1:
The patent utilizes the inherent capacitance of the tissue and electrode interface to perform charge recovery automatically without requiring active circuitry. The monophasic pulse charges the tissue capacitance, and the subsequent passive recovery period allows the capacitance to discharge naturally through the tissue impedance. This self-service mechanism extends battery life while avoiding the need for complex active charge recovery circuits, thus limiting waveform complexity to simple monophasic pulses with timing control.
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 effective pain relief without paresthesia and extends the battery life of the IPG by allowing for sub-perception therapy at lower frequencies, reducing the need for frequent battery replacement or recharging.
Implementation Method 1
monophasic pulse portion 132 is followed by a passive charge recovery period 134 which produces a passive charge recovery pulse portion 134
Implementation Method 2
a passive charge recovery period 134 which produces a passive charge recovery pulse portion 134
Data Source
AI summary
New waveforms for use in an implantable pulse generator or external trial stimulator are disclosed which mimic actively-driven biphasic pulses, and which are particularly useful for issuing low frequencies pulses. The waveforms comprise at each electrode interleaved first and second pulses. Each first pulse comprises a first monophasic pulse and a first passive charge recovery period. Each second pulse comprises a second monophasic pulse with a polarity opposite the first monophasic pulse and a second passive charge recovery period. Preferably, the amplitudes and pulse widths of the first and second monophasic pulses are equal, or at least charge balanced at each electrode. The first and second monophasic pulses mimic the functionality of a symmetric biphasic pulse, with the first monophasic pulse mimicking the functionality of the biphasic pulse's first phase, and the with the second monophasic pulse mimicking the functionality of the biphasic pulse's second phase.