Vagus Nerve Stimulator May Help Relieve Indigestion
Vagus nerve stimulation via non-invasive earbuds may provide indigestion relief.
Posted May 5, 2020 | Reviewed by Abigail Fagan
A vagus nerve stimulation (VNS) device that hooks onto the ear shows promise as a new, non-invasive treatment for indigestion. Researchers at Harvard Medical School recently discovered that patients with a form of indigestion called functional dyspepsia appear to benefit from this device. The initial findings of this study (Sclocco et al., 2020) were published on April 20 in The FASEB Journal.
Technically, this earbud-like gizmo is categorized as a transcutaneous auricular vagus nerve stimulator (taVNS). A recent news release states: "This study is one of the first to assess the potential benefits of auricular taVNS for gastrointestinal problems."
According to the authors, about 15 percent of adults in the U.S. suffer from functional dyspepsia.
This taVNS device modulates the stomach's response to food ingestion in a way that aids digestion. Even after eating a small portion of food, people with functional dyspepsia commonly experience pressure and discomfort because the stomach doesn't expand and contract appropriately. This form of indigestion can cause severe stomach pain after every meal.
"The vagus nerve plays an important role in both sensory and motor aspects of gastric physiology. Both animal and human studies suggest that accommodation reflex consists of a vagovagal reflex pathway," the authors explain. "Transcutaneous vagus nerve stimulation (tVNS) of the auricular branch of the vagus nerve is a promising non‐invasive neuromodulatory therapy for numerous disorders."
Over the years, different forms of VNS have been shown to help patients with epilepsy, chronic inflammation, treatment-resistant depression, rheumatoid arthritis, migraine headaches, and other disorders. (See here, here, here, and here)
Last year, a UK-based study (Bretherton et al., 2019) reported that 15 minutes of daily, self-administered tVNS via the outer ear boosted "rest and digest" parasympathetic activity in a cohort of older adults (55-years-old or above). This study was a follow-up to previous research (Deuchars et al., 2017), which found that tVNS via the external ear improved autonomic nervous system functions in younger participants. (See "Vagus Nerve Stimulation via the Outer Ear Takes Center Stage")
For the recent study (2020) on using an earbud-like device to relieve indigestion, lead author Roberta Sclocco, a postdoctoral fellow at Harvard Medical School's Massachusetts General Hospital, focused on a groundbreaking type of taVNS called Respiratory-gated Auricular Vagal Afferent Nerve Stimulation (RAVANS).
RAVANS delivers painless electrical pulses to the vagus nerve during the exhalation phase of someone's breathing cycle. These bursts of electricity are about one second long. The earbud-like stimulator is respiratory-gated to activate during the exhalation phase of respiration and mimics the modulation of cardiac vagal activity that occurs during diaphragmatic breathing.
"Some people find relief from indigestion with non-technological and non-medical approaches, such as taking slow, deep breaths after eating," Sclocco said. (See my blog post "Longer Exhalations Are an Easy Way to Hack Your Vagus Nerve")
Previous respiratory-gated taVNS research (2017) by Sclocco and colleagues found that a mid-intensity level of RAVANS vagus nerve stimulation (rated as a five on a 0-10 scale) "increases the cardiovagal tone and reduces the sympathetic tone during a paced breathing task."
"Our findings (2020) suggest that RAVANS has the ability to modulate the stomach's response to food ingestion, which may be impaired in functional dyspepsia patients," Sclocco said in an April 27 news release. "RAVANS is a non-invasive, safe peripheral nerve stimulation intervention. [While] our results are encouraging, further research is needed to estimate the optimal dose and timings of this intervention."
Future research by Roberta Sclocco and her colleagues at Mass General will focus on fine-tuning the optimal electrical dosage and timing for respiratory-gated vagus nerve stimulation using an earbud-like device.
"While taVNS is relatively safe and without major side effects, systems currently available on the market are all different and not optimized for gastric applications," Sclocco cautions. "Patients with certain medical conditions may not be good candidates for this therapy, and discussing the taVNS option with a medical doctor in the context of a patient's overall clinical picture is always advisable."
Roberta Sclocco, Christopher Nguyen, Rowan Staley, Harrison P. Fisher, Christopher Velez, April Mendez, Kun-Han Lu, Zhongming Liu, Matthew P. Ward, Terry Powley, Norman W. Kettner, Braden Kuo, Vitaly Napadow. "SPARC: Respiratory‐Gated Transcutaneous Vagus Nerve Stimulation Modulates Gastric Function in Functional Dyspepsia." The FASEB Journal (First published: April 20, 2020) DOI: 10.1096/fasebj.2020.34.s1.02939
Roberta Sclocco, Ronald G. Garcia, Aileen Gabriel, Norman W. Kettner, Vitaly Napadow, Riccardo Barbieri. "Respiratory-Gated Auricular Vagal Afferent Nerve Stimulation (RAVANS) Effects on Autonomic Outflow in Hypertension." 2017 39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (Date of Conference: July 11-15, 2017) DOI: 10.1109/EMBC.2017.8037520