Frequency-Dependent Effects of Exhalatory-Gated Transcutaneous Vagus Nerve Stimulation on Cardiac Autonomic Regulation in Hypertension

The objective of this study was to determine potential effects of respiratory-gated auricular vagal afferent nerve stimulation (RAVANS) on cardiovagal activity in hypertensive patients. Twenty hypertensive subjects (54.55±6.23 years; 12 females) underwent five randomized sessions of RAVANS at frequencies of 0, 2, 10, 25, and 100 Hz. Continuous electrocardiogram (ECG) and pulse rate signals were collected during 10-minute baseline, 30-minute stimulation, and 10-minute recovery periods using a Grass LP511 AC amplifier and piezo device. LabChart was used to acquire ECG and pulse signals and to process heart rate variability (HRV) indices. A significant increase in high frequency (HF) power (%) was observed during the RAVANS-100 Hz session from baseline to recovery ln=0.039) when compared to sham, adjusting for sex and baseline values. HRV evaluation for other frequencies did not yield significant results. These results suggest that RAVANS has a frequency-dependent effect on the modulation of cardiovagal activity (HF-HRV) in hypertension.