Performance Assessment of a New Electromyography-based Neuromuscular Monitor and Subjective Discomfort in Unmedicated Volunteers

Objective: The aim of this prospective, unblinded, randomized study was to provide performance data of the prototype of new electromyography-based neuromuscular monitor, the NEAT device (Acacia Designs BV, Amsterdam, the Netherlands) and assess the subjective discomfort associated with neurostimulation in unmedicated healthy volunteers. Methods: The study enrolled ten male and ten female volunteers. Based on a priori randomization the ulnar nerve of the left or right arms was stimulated in 1 Hz single twitch and train-of-four modes. Stimulating current intensity was increased from 10 mA to 60 mA in 10 mA steps. Electromyography recordings were performed at the abductor digiti minimi and adductor pollicis muscles via surface electrodes. The volunteers were asked to rate the discomfort in association with neurostimulation on a 0-10 visual analogue scale. Results: The overall train-of-four ratio was 1.02 (0.98-1.06) {median and (interquartile range)}. The abductor digiti minimi muscle required lower stimulating current intensity to evoke maximal stimulation, than the adductor pollicis (30 vs. 50 mA, p<0.001). The overall intracurrent variability of compound muscle action potential amplitudes was 0.42 (0.21-0.87) mV, that was unaffected by the type of muscle or the stimulating current intensity. Women reported moderately higher visual analogue scale scores than men. The largest recorded difference was 5 (3.75-6) vs. 3 (3-4), p<0.05. Conclusion: The Acacia Designs BV NEAT monitoring device was suitable to deliver neurostimulation, record and analyze the elicited muscle action potentials. The precision of stimulations was acceptable. The volunteers reported the discomfort in association with neurostimulation as tolerable. Registered at the Hungarian Office for Health Authorization and Administrative Procedures (December 30th, 2014). Identifier: 028605-010/2014/OTIG. Registered at clinicaltrials.gov (December 15th, 2015). Identifier: NCT02630576.