Introduction: Despite the benefits of existing blood pressure lowering drugs, approximately 50% of hypertensive patients are inadequately controlled while taking medications. Autonomic nervous system dysfunction is associated with the development and progression of hypertension, and neurostimulation devices that target sympathetic or vagal modulation have been suggested as potential novel treatments for this disorder.
Hypothesis: In this study, we assessed the hypothesis that respiratory gated transcutaneous vagus nerve stimulation (RAVANS tVNS) reduces blood pressure in hypertensive patients.
Methods: Twelve hypertensive subjects (53.2 ± 5.8 years, 7 males) with persistent high blood pressure levels despite current antihypertensive treatment were enrolled in the study. Participants underwent two experimental sessions on non-consecutive days. In each session subjects were evaluated during an initial rest period followed by RAVANS or sham tVNS stimulation. Electrodes were placed over vagal innervated regions in the ear (cymba concha). RAVANS tVNS was delivered for 15 minutes at 25 Hz (pulse width: 15 ms), and gated in real time to exhalation. Sham stimulation was delivered with the current generator shut off, without the subjects’ knowledge. Measurement of blood pressure levels by continuous beat-to-beat recordings were performed with a Finometer device (Finapress Medical System, the Netherlands). Mean arterial pressure (MAP) levels were computed over the rest and stimulation periods and were compared between groups.
Results: No significant baseline differences in MAP levels were found between groups (104.9 ± 7.6 mmHg vs 103.6 ± 6.1 mmHg, p=0.6). Administration of exhalatory-gated RAVANS tVNS resulted in a significant reduction of MAP values compared to Sham tVNS (-4.1 ± 7.0 mmHG vs 2.6 ± 5.6 mmHg, p=0.02), whereas no significant effects in heart rate or respiratory frequency were observed.
Conclusions: Our findings reveal that exhalatory-gated RAVANS tVNS has a significant effect in the acute reduction of blood pressure levels in hypertensive patients. These promising results support a potential role of this intervention in the treatment of hypertension, however further longitudinal studies will be required to test this hypothesis.