P211 Development, safety, and parameter optimization of a novel form of noninvasive vagus nerve stimulation: Transcutaneous auricular vagus nerve stimulation (taVNS)

Abstract

Introduction Cervically implanted vagus nerve stimulation (VNS) is FDA-approved for treating epilepsy or major depression. Additionally, interest in VNS has reemerged, showing promise in several translatable animal studies. We have developed a noninvasive device that electrically stimulates the auricular branch of the vagus nerve called transcutaneous auricular vagus nerve stimulation (taVNS). Objectives The aims of this study were to (1) develop a noninvasive transcutaneous auricular vagus nerve stimulator, (2) determine whether it is a safe and feasible form of neuromodulation, and (3) determine optimal taVNS parameters that modulate vagal tone. Patients & methods This single-blind, sham controlled, crossover study consisted of 2 separate visits during which custom-built electrodes were used to deliver electrical stimulation to either the left tragus or earlobe (active or sham respectively) in 15 healthy adult participants. Participants received nine different randomized stimulation sessions (60 s each) of varying pulse width and frequency. Primary outcome measures recorded were heart rate, skin temperature, and skin conductance. Painfulness was also rated on a visual analog scale (VAS) and participants were constantly monitored for major and minor adverse events. Results No adverse events were observed and active stimulation was not more painful than sham. Mean pain VAS scores ranged from 0.2 to 1.94. With respect to condition, there was no significant decrease in heart rate between all active and all sham stimulations in an overall group analysis ( n = 135 sessions, mean HR decrease active = 1.86BPM, Sham = 1.47BPM; p = 0.521). When analyzed based on a parameter basis, two of nine parameters had significant decreases in heart rate (500 μs, 25 Hz; 200 μs, 25 Hz; p Conclusion Short doses of taVNS in healthy young adults is feasible, tolerable, and reasonably safe. Like all forms of brain stimulation, the specific parameters of stimulation are important in modulating vagal tone (current (mA), pulse width (μs), and frequency (Hz). Follow-up studies testing optimized parameters in the fMRI scanner are currently being conducted.