Frequency-Dependent Effects of Auricular Vagus Nerve Stimulation on Autonomic and Cardiovascular Parameters

N/ANot Yet RecruitingNCT07274332

SEFA HAKTAN HATIK36 enrolled

Overview

This randomized, sham-controlled, crossover study investigates the acute autonomic effects of transcutaneous cervical vagus nerve stimulation (tcVNS) applied at five different frequencies (0 Hz/sham, 10 Hz, 25 Hz, 50 Hz, 100 Hz) in healthy adults. The primary objective is to determine how stimulation frequency modulates heart rate variability (HRV), blood pressure, and respiratory rate. The study aims to establish a frequency-specific dose-response model using validated physiological measurements.

Transcutaneous cervical vagus nerve stimulation (tcVNS) is a non-invasive neuromodulation technique capable of activating afferent vagal pathways projecting to autonomic brainstem nuclei. Although previous studies demonstrate tcVNS-related modulation of autonomic functions, the frequency-response relationship remains insufficiently explored. This crossover trial randomizes participants to receive five stimulation conditions (sham, 10 Hz, 25 Hz, 50 Hz, 100 Hz) in counterbalanced order. HRV (Polar H10), blood pressure (Omron), and respiratory rate (Kinovea-based thoracoabdominal video tracking) are collected pre- and post-stimulation. Washout between sessions is ≥48 hours. The study provides one of the first systematic evaluations of frequency-dependent tcVNS effects in healthy adults.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

SINGLE

Enrollment

Conditions

Vagus Nerve Stimulation

Interventions

Pulsetto FIT™ - Sham tcVNSDEVICE

The Pulsetto FIT™ device is placed bilaterally on the cervical region (posterior margin of the sternocleidomastoid muscle). In the sham condition, the device displays normal operational lights but delivers no electrical stimulation (0 Hz; inactive mode). This condition is used for blinding and as the control comparator. Dose: 10 minutes

Pulsetto FIT™ - tcVNS 10 HzDEVICE

Bilateral transcutaneous cervical vagus nerve stimulation delivered via the Pulsetto FIT™ device at 10 Hz, 250 µs pulse width. Current intensity adjusted to a mild, non-painful tingling sensation, individualized for each participant. Dose: 10 minutes

Pulsetto FIT™ - tcVNS 25 HzDEVICE

Bilateral tcVNS using the Pulsetto FIT™ device at 25 Hz, 250 µs pulse width. Stimulation intensity set at a comfortable sensory level. Dose: 10 minutes

Pulsetto FIT™ - tcVNS 50 HzDEVICE

Bilateral cervical vagus nerve stimulation via Pulsetto FIT™ at 50 Hz, 250 µs pulse width. Intensity adjusted to a tolerable sensory level without discomfort. Dose: 10 minutes

Pulsetto FIT™ - tcVNS 100 HzDEVICE

Bilateral tcVNS delivered with the Pulsetto FIT™ device at 100 Hz, 250 µs pulse width. Highest stimulation frequency used in this protocol; current intensity individualized per participant comfort. Dose: 10 minutes

Eligibility

Sex: ALLMin age: 18 YearsMax age: 30 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * 18-30 years * Healthy (self-reported) * No cardiovascular, neurological, metabolic or psychiatric disorders * No regular medication affecting autonomic function * Non-smoker * BMI 18-29.9 Exclusion Criteria: * Pregnancy * Cardiac arrhythmia * Hypertension or hypotension * Chronic respiratory disorders * Active infection * Metal implants in cervical area * Epilepsy * Syncope history * Prior vagus stimulation experience

Outcomes

Primary Outcomes

Heart Rate Variability (HRV) Changes (ΔRMSSD, ΔHF, ΔLF/HF)

HRV is recorded using a validated high-resolution heart rate monitor (Polar H10) during a 5-minute resting baseline (T0) and a 5-minute post-stimulation period (T2). The following time- and frequency-domain parameters are analyzed: RMSSD, HF (ms²), and LF/HF ratio. Artefact correction is performed using standard HRV processing methods. Acute autonomic response is quantified by calculating change scores (Δ = post-pre) for each stimulation frequency.

Time frame: Pre- vs Post-stimulation (5-min segments)(5-minute baseline, 5-minute stimulation, 5-minute post period)

Secondary Outcomes

Blood Pressure (SBP, DBP, MAP)

Two readings are taken at each time point from the right arm with a validated automatic sphygmomanometer, and the average systolic, diastolic, and mean arterial pressure values are used for analysis. Changes are calculated as post-pre (Δ values) to assess the acute physiological effect of each stimulation frequency..

Time frame: Pre- vs Post-stimulation (5-minute baseline, 5-minute stimulation, 5-minute post period)

Respiratory Rate (breaths per minute)

Respiratory rate is assessed by video-based thoracoabdominal motion tracking at baseline (T0) and after stimulation (T2). Videos are analyzed using Kinovea motion-tracking software, and a 1-minute stable segment is used to determine breaths per minute by counting inspiratory peaks. Respiratory changes are expressed as Δ values (post-pre) to account for individual differences and improve HRV interpretability.Respiratory rate is assessed by video-based thoracoabdominal motion tracking at baseline (T0) and after stimulation (T2). Videos are analyzed using Kinovea motion-tracking software, and a 1-minute stable segment is used to determine breaths per minute by counting inspiratory peaks. Respiratory changes are expressed as Δ values (post-pre) to account for individual differences and improve HRV interpretability.

Time frame: Pre- vs Post-stimulation (5-minute video segments) (5-minute baseline, 5-minute stimulation, 5-minute post period)

Discomfort Level (Visual Analog Scale, 0-10)

Participants report their perceived discomfort level at baseline (T0) and immediately after stimulation (T2) using a 0-10 Visual Analog Scale (VAS). The scale captures any sensory discomfort associated with tcVNS. Changes are calculated by subtracting the pre-stimulation score from the post-stimulation score (ΔVAS).