Objective

2

To compare the difference of autonomic responses to transcutaneous auricular vagus nerve stimulation (taVNS) between high-altitude and low-altitude populations

explore the characteristics of neural response under the background of high altitude hypoxia.

Methods

2

A total of 30 border guards stationed in high altitude areas for an extended period were included as the high altitude group. At the same time

30 healthy subjects were recruited in Beijing as the low altitude group. In both groups

taVNS was applied bilaterally to the auricular branches of the vagus nerve distribution areas (auricular points corresponding to shen[CO

10

]

and xin[CO

15

]

). Using a multimodal wristband

photoplethysmography (PPG) signals were collected during the baseline period

stimulation period

and recovery period. Heart rate (HR) and time-domain and frequency-domain indexes of heart rate variability (HRV) were compared between the two groups. The time-domain indexes included the standard deviation of normal-to-normal intervals (SDNN)

the root mean square of successive differences (RMSSD)

and the percentage of adjacent normal RR intervals differing by more than 50 ms (pNN50). The frequency-domain indexes included low-frequency power (LF)

high-frequency power (HF)

and low-frequency/high- frequency (LF/HF).

Results

2

In the high altitude group

HR during the stimulation period was lower than that during the baseline period (

P

<

0.05)

and RMSSD was lower than that during the recovery period (

P

<

0.05). In the low altitude group

all indexes showed no statistically significant differences among the baseline

stimulation

and recovery periods (

P

>

0.05). The high altitude group exhibited higher HR

SDNN

RMSSD

pNN50

LF

and HF across all three periods compared to the low altitude group (

P

<

0.05)

and lower LF/HF compared to the low altitude group (

P

<

0.05).

Conclusion

2

Under taVNS intervention

the vagal responses in high-altitude populations exhibit a characteristic pattern of delayed activation. This finding suggests that taVNS interventions for high-altitude populations should appropriately extend post-stimulation observation time and optimize stimulation patterns.