Tragus based vagus nerve stimulation for stress reduction

Non-invasive vagus nerve stimulation is fast becoming a popular alternative treatment method for various
health disorders. The authors investigated the effects of auricular vagus nerve stimulation at tragus for activating
the parasympathetic nervous system to reduce stress, in light of mixed results from other studies. Stimulation
frequency of 25 Hz with a pulse-width of 200 μs was administered at tragus with ECG data recorded
during pre- and post-stimulation trials to investigate changes in the low-frequency (LF) and high-frequency
(HF) parameters of heart rate variability (HRV). The results from five subjects demonstrate an increase in
the HF component and a decrease in LF when comparing pre- and post- stimulation values, denoting that
VNS stimulated more of the parasympathetic activity. The LF/HF ratio was reduced for all participants after
stimulation, with an average reduction of 64:5% observed. Overall, this study has indicated the feasibility of
using tragus as a stimulation site to stimulate the vagus nerve; tragus being easier to administrate than many
alternative sites while still being effective for stress reduction.