Jiangxi Puzhuo Medical Equipment Co., Ltd

Original link: Transcutaneous vagus nerve stimulation and heart rate variability: parameter and target analysis. pdf 

Heart rate variability (HRV) is the golden indicator for measuring the balance of the autonomic nervous system, as well as a barometer for the body's ability to withstand pressure, relax, and repair. The higher the HRV, the more likely it is that the parasympathetic nervous system is dominant, resulting in a calmer state, better sleep, and less fatigue.

Transcutaneous vagus nerve stimulation (taVNS) has been proven to effectively enhance HRV as a non-invasive, safe, and side effect free neural regulatory tool. But for a long time, there has been no standard answer to the three core questions: which position of the ear has the best stimulation effect? How to match current and pulse width effectively and comfortably? Is there a difference in the effect of stimulating the left ear or the right ear?

Recently, the neural regulation team at the University Hospital of T ü bingen in Germany published a heavyweight study in the international journal "Autonomous Neuroscience". The study systematically compared six stimulation sites and 144 parameter combinations, and for the first time provided the scientific optimal solution for taVNS to regulate HRV, providing a solid basis for clinical applications and home device development.

Research background: From "fuzzy stimulation" to "precise regulation"

Traditional invasive vagus nerve stimulation (iVNS) requires surgical implantation and carries certain risks and complications. However, taVNS can regulate both central and peripheral nerves through gentle electrical stimulation of the external ear, demonstrating great potential in areas such as insomnia, anxiety, depression, epilepsy, and cardiovascular regulation.

However, due to the inconsistent stimulation sites and lack of consensus on stimulation parameters, the effect of taVNS has been difficult to reproduce stably.

Therefore, this study proposes the core hypothesis:

The stimulation site and charge amount of taVNS directly determine the HRV enhancement effect, and the optimal solution can be objectively screened through HRV.

Research Design: Rigorous system, covering all dimensional variables

Research Object

Thirteen healthy young participants (with an average age of 24), without neurological, psychiatric, or heart diseases, were prohibited from consuming caffeine or alcohol for 2 hours prior to the test.

Experimental Plan

Side comparison: left ear group (6 people) vs right ear group (7 people)

6 major stimulation sites: ear nail boat, ear nail cavity, external tragus, internal tragus, earlobe foot, triangular fossa

Stimulus parameters: 24 parameter combinations tested at each point, 3 pulse widths combined with equal charge current:

✦ 100 μ s: 0.250-2mA (step size 0.250mA)

260 μ s: 0.096-0.769mA (step size 0.096mA)

500 μ s: 0.050-0.400mA (step size 0.050mA)

Stimulus mode: Each parameter combination applies 30 pulse trains periodically at 1Hz, with each pulse train containing 5 pulses applied at a frequency of 25Hz.

data processing

Collect ECG and analyze time-domain (SDNN, RMSSD, etc.) and non-linear (SD1, SD2, etc.) HRV indicators.

Statistical methods: Mixed model ANOVA, Tukey Kramer post hoc test, P< 0.05 indicates a significant difference.

Core result: Triple key findings

Stimulus parameters: Short pulse width+high charge are more effective and comfortable

The shorter the pulse width, the more significant the HRV improvement: 100 μ s is optimal

The current intensity is positively correlated with HRV, and 2mA (100 μ s) has the best effect and comfort

Under the condition of equal charge, there is no significant difference in the effect of different parameter combinations, but short pulse width tolerance is better

Long pulse width is more likely to cause discomfort, and some subjects cannot tolerate high charge conditions

Stimulus side: The right ear is significantly better than the left ear

Stimulating the right ear: SDNN, RMSSD, SD1, and SD2 are significantly elevated across the board

Stimulating the left ear: HRV showed no significant increase, even decreased

双侧差异具有统计学意义（p<0.001），右耳为提升HRV的优选侧别The bilateral difference is statistically significant (p<0>

Stimulating area: Ear nail boat and triangular fossa have the strongest effect

Effect strength from high to low: Cymba conchae > Fossa triangularis > Inner tragus

HRV improvement in cymba conchae was significantly superior to cavum conchae, outer tragus and crus helicis (p<0.05)

Fossa triangularis is a newly‑discovered high‑efficiency site with effects close to cymba conchae

Cavum conchae, outer tragus and crus helicis show weak effects and can serve as control sites

Safety Results

No serious adverse events, no cardiac adverse reactions such as palpitations, bradycardia or arrhythmia

Mild local redness and discomfort only occurred under high‑charge and long‑pulse‑width conditions

The combination of 100 μs + 2 mA delivered the highest comfort level without obvious discomfort