Spatiotemporal parameters for energy efficient kilohertz-frequency nerve block with low onset response

Area of Science:

• Biomedical Engineering
• Neuroscience
• Medical Devices

Background:

• Electrical nerve conduction block offers reversible nerve inactivation for disease treatment.
• High energy requirements and undesired nerve excitation limit kilohertz-frequency (KHF) nerve block efficacy.
• Limited understanding of parameter optimization (frequency, electrode geometry, waveform) hinders KHF nerve block translation.

Purpose of the Study:

• To evaluate kilohertz-frequency (KHF) nerve block in rat tibial nerve.
• To investigate the impact of varying frequencies, electrode geometries, and waveform shapes on nerve block parameters.
• To develop and assess a novel method for constructing composite KHF signals to optimize nerve block.

Main Methods:

• Tested KHF nerve block in rat tibial nerve across frequencies (5-60 kHz), electrode geometries (monopolar, bipolar, tripolar), and waveform shapes.
• Utilized a novel Fourier-based method to construct composite signals systematically exploring KHF waveform design.
• Analyzed block threshold and onset response in relation to signal parameters and electrode configurations.

Main Results:

• Lowest effective blocking frequencies (5-16 kHz) were not the most energy-efficient.
• Monopolar and tripolar electrodes demonstrated the lowest power requirements for nerve block, with monopolar requiring the least current.
• Composite signals, specifically those with a fundamental and second harmonic sinusoid, reduced block threshold and onset response, dependent on phase and amplitude, particularly with monopolar and tripolar electrodes.

Conclusions:

• Novel insights into block threshold and onset response at the frequency boundary of KHF nerve block were obtained.
• Demonstrated an interaction between spatial (electrode geometry) and temporal (frequency, waveform) parameters in KHF nerve block.
• Optimized waveform shapes can reduce both energy consumption and undesirable onset responses, overcoming previous trade-offs.