Design and Evaluation of a Prototype of Dual Channel Electrical Stimulator: Application in the Assessment of Current Perception Thresholds to Multiple Stimuli

The Current Perception Threshold (CPT) to sinusoidal electrical current stimulus can assess different types of peripheral nervous fibers, 1 Hz can stimulate thin and 3 kHz thick fibers. The behavior of CPT to multiple simultaneous sinusoidal electrical stimuli remains unexplored. This work aims to present a two-channel Electrical Stimulator (ES) design and evaluation to investigate the CPT at multiple stimuli. The ES includes a user interface in LabVIEW (to configure and control the stimulation) and an Electronic Circuit for two independent current sources with arbitrary waveforms. The prototype underwent a functional test with sinusoidal waveforms and showed a Total Harmonic Distortion of less than 1% and a non-linearity factor of less than 1.6%. The output current with a square waveform on loads from 100 Ω to 100 kΩ was constant. The crosstalk between the channels showed values less than 0.1% for sinusoidal frequencies of 1 Hz (channel 1) and 3 kHz (channel 2). Eight healthy subjects participated of the preliminary experiment, which consisted of obtaining the CPT for median nerve to 1 Hz, 3 kHz, and both stimuli simultaneously. The mean CPT to 1 Hz and 3 kHz showed similar values to the literature, 154 ± 17 µA, and 1011 ± 37 µA, respectively. The results with simultaneous stimuli showed a more significant interference of 3 kHz above 1 Hz CPT than 1 Hz above 3 kHz CPT. The results suggest that the system could generate controlled and repeatable stimuli in two independent channels and can be used to investigate the peripheral nerve fibers in scenarios of multiple electrical stimuli.