Exploratory Investigation of the Effects of Tactile Stimulation Using Air Pressure at the Auricular Vagus Nerve on Heart Rate Variability

OBJECTIVE: To explore the effects of tactile stimulation using air pressure at the auricular branch of the vagus nerve on autonomic activity in healthy individuals. METHODS: Three types of tactile stimulation were used in this study: continuous low-amplitude, continuous high-amplitude, and pulsed airflow. The tactile stimulations were provided to the cymba concha to investigate autonomic activity in 22 healthy participants. The mean heart rate (HR) and parameters of HR variability, including the standard deviation of R-R intervals (SDNN) and root mean square of successive R-R interval differences (RMSSD) were compared at baseline, stimulation, and recovery periods. RESULTS: Two-way repeated measures ANOVA indicated a significant main effect of time on HR (p=0.001), SDNN (p=0.003), and RMSSD (p<0.001). These parameters showed significant differences between baseline and stimulation periods and baseline and recovery periods in the post-hoc analyses. There were no significant differences in the changes induced by stimulation type and the interaction between time and stimulation type for all parameters. One-way repeated measures ANOVA showed that HR, SDNN, and RMSSD did not differ significantly among the three time periods during sham stimulation. CONCLUSION: Parasympathetic activity can be enhanced by auricular tactile stimulation using air pressure, targeting the cymba concha. Further studies are warranted to investigate the optimal stimulation parameters for potential clinical significance.