Portable microcontroller-based electrostimulation system for nerve conduction studies

Abstract

Despite nerve conduction study (NCS) being an established procedure in the evaluation of neuromuscular disorders, its utility has been restrained by commercially available products or approaches presented in the literature that are either costly, physically large, dependent on specialised medical personnel to operate or targeted to specific conditions, evaluating only one or two nerves. Therefore, the objective of this work was to develop a point-of-care device for NCS that can be used to evaluate several nerves, yet is still portable, low-cost and easy to operate. The developed device is composed of three modules: (i) controller module and graphical user interface, responsible for system synchronisation and configuration, data management, graphical visualisation of the evoked action potential and stimulus voltage feedback (maximum error of 3.92%); (ii) stimulation module, which operates in a constant voltage mode and delivers a monophasic stimulus pulse with amplitudes between 0.84 and 230 V, with a discrete increment of 2.32 ± 0.64 V (mean ± SD) and duration of 100 or 200 µs; and (iii) data acquisition module, based on the ADS1298 front-end that records the evoked action potentials after the stimulus, with a sample rate of 16 or 32 kHz, 24-bit resolution and selectable voltage gain of 1 up to 12. Results demonstrated that the system could reliably deliver stimulation pulses through different loads (100 Ω, 1 kΩ and 10 kΩ) and accurately record data through frequencies of 10 Hz up to 10 kHz. Additionally, NCS of the ulnar motor nerve in a sample of healthy individuals showed that the device could effectively activate a peripheral nerve and record compound action potentials within normal limits established by the literature.