Breathing & Vagus Nerve Stimulation: Ancient Medicine Made Modern w/Neuromodulation

[Randy Eady]

Respiratory-Gated Vagal Afferent Nerve Stimulation (RAVANS) @Mass Gen Hospital (MGH) is showing promise in the investigation of non-invasive therapies.  This is significant as nerve stimulation is often pitted as an alternative to more disruptive pain management therapies — particularly opioids. 

“There is a great need to offer effective therapies not based on drugs or invasive implants,” said MGH research lab director Vitaly Napadow. “Non-invasive neuromodulation may help address that need.”

An ongoing trial is investigating the effects of different intensities of RAVANS in hypertensive people showing mid-intensity RAVANS stimulation (rated as a 5 on a 0-10 scale) increases the cardiovagal tone & reduces the sympathetic tone during paced-breathing tasks.

https://www.sciencedirect.com/science/article/abs/pii/S1935861X1930...

Highlights

- Respiration influences the brainstem activity, which is facilitated much more during exhalation

- The effects of auricular (ear) vagus nerve stimulation can be optimized with respiratory-gating (timing vagus nerve stim during breathing)        

- fMRI and heart rate variability were used to investigate central and peripheral responses to vagus nerve stimulation

- Exhalation-gated tVNS enhances engagement of key neuromodulator brainstem nuclei

- Exhalation-gated tVNS increases stimulus-evoked cardiovagal outflow

Furthermore, exhalation (eRAVANS), but not inhalation (iRAVANS) was shown to enhance cardiovagal modulation, confirming enhanced eRAVANS response on both central & peripheral neurophysiological levels can be optimized with respiratory gating.  Conclusive fMRIs localized on the  brainstem response of transcutaneous auricular VNS (taVNS) linked responses w/autonomic outflow, and demonstrated taVNS applied during exhalation enhanced locus coeruleus (LC, noradrenergic) and both dorsal and median raphe (serotonergic) nuclei.  A positive, binding association between the LC and serotonergic contributions of this brain region have been observed to support resting-state signals in the autonomic nervous system.