An interventional study of Transcutaneous auricular vagus nerve stimulation in Autonomic Nervous System (ANS) Functioning and Mood State, Heart Rate Variability (HRV) and Blood Pressure Monitoring, sponsored by SEFA HAKTAN HATIK. Enrolling by invitation at 1 site in Turkey (Türkiye). Open to participants aged 18 Years to 40 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-04-23.
Sponsored by SEFA HAKTAN HATIK · Not applicable, Interventional, and Other
This study examines the reliability and agreement of autonomic nervous system measurements obtained from different anatomical sites during transcutaneous auricular vagus nerve stimulation (taVNS). taVNS is a non-invasive electrical stimulation delivered to the ear using a small stimulator. Healthy volunteers aged 18-40 years will participate in one laboratory session. Heart rate and heart rate variability will be recorded from the chest (reference), finger, and arm. Blood pressure and pulse will also be measured. Data will be collected in three standardized periods: T0 (5-minute resting baseline), T1 (10 minutes during taVNS), and T2 (5-minute recovery). The main goal is to determine how closely finger- and arm-based measurements match the chest reference and how consistent these measurements are across the study periods. Participation is voluntary, and participants may withdraw at any time. Expected risks are minimal and may include temporary tingling or mild discomfort at the ear and, rarely, lightheadedness. No direct medical benefit is expected, but the findings may help improve how autonomic responses are monitored during taVNS in future research.
Heart rate variability (HRV) is widely used to quantify autonomic regulation, and non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) may acutely influence cardiac autonomic activity. In both clinical and research settings, autonomic measures can be recorded from different sites using different sensor technologies. However, it is not always clear whether HRV-related indices derived from peripheral recordings (e.g., finger or arm photoplethysmography-based signals) provide comparable results to chest-based reference recordings. This study is designed as a methodological reliability and agreement investigation to determine the consistency of autonomic measures across anatomical sites during a standardized taVNS session.
Participants will attend a single laboratory visit with standardized pre-test instructions (e.g., avoidance of heavy exercise and stimulants before measurement, as applicable). Autonomic measures will be recorded from multiple sites in parallel, using the chest recording as the reference for beat-to-beat intervals. Finger and arm recordings will be obtained simultaneously to allow direct, time-aligned comparisons across sites within the same physiological state. Blood pressure and pulse will be measured during the session to provide complementary hemodynamic context.
The session consists of consecutive measurement periods representing baseline, stimulation, and recovery. Data will be processed using standard HRV pipelines (including artifact inspection and correction when needed) to derive time-domain and frequency-domain indices. The primary analyses will focus on (1) inter-site agreement (bias and limits of agreement) and (2) reliability/consistency metrics across the measurement periods. Agreement will be evaluated using Bland-Altman approaches and related indices, while reliability will be quantified using intraclass correlation coefficients (ICCs) with appropriate model specification. Secondary analyses may explore the association between HRV indices and hemodynamic parameters across periods.
This study involves minimal risk. Expected adverse effects, if any, are transient (e.g., mild ear discomfort or tingling, and rarely lightheadedness). Participant safety will be monitored by the study team throughout the session, and the procedure will be stopped if a participant requests discontinuation or if concerning symptoms occur. Data will be recorded and stored in a de-identified format, and results will be reported at the group level.
SEFA HAKTAN HATIK is the lead sponsor of 14 studies on the registry; 8 are open to participants now.
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Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
All participants receive a single session of transcutaneous auricular vagus nerve stimulation (taVNS). Autonomic measures are recorded simultaneously from chest (reference), finger, and arm during baseline (T0, 5 min), stimulation (T1, 10 min), and recovery (T2, 5 min). Blood pressure and pulse are also measured during the session. No separate arms or randomization are used.
Device: Transcutaneous auricular vagus nerve stimulation
Transcutaneous auricular vagus nerve stimulation will be delivered to the cymba conchae region of the auricle using an external stimulator. Stimulation will be set to 25 Hz with a pulse width of 200-300 microseconds. Current intensity will be individually adjusted to a clearly perceptible but non-painful level (typically 0.5-5 mA). Stimulation will be applied for 10 minutes.
RMSSD inter-site agreement across chest, finger, and arm recordings
Root mean square of successive differences (RMSSD) derived from simultaneous recordings at three sites (chest as reference, finger, and arm) will be compared to determine inter-site agreement and reliability. Agreement will be evaluated using Bland-Altman analysis (bias and limits of agreement), and reliability/consistency will be quantified using intraclass correlation coefficients (ICC). Unit of Measure: ms
Time frame: During a single session: baseline (T0, 5 minutes), stimulation (T1, 10 minutes), and recovery (T2, 5 minutes).
SDNN inter-site agreement across chest, finger, and arm recordings
Standard deviation of normal-to-normal intervals (SDNN) derived from simultaneous recordings at three sites (chest as reference, finger, and arm) will be compared to determine inter-site agreement and reliability. Agreement will be evaluated using Bland-Altman analysis (bias and limits of agreement), and reliability/consistency will be quantified using intraclass correlation coefficients (ICC). Unit of Measure: ms
Time frame: During a single session: baseline (T0, 5 minutes), stimulation (T1, 10 minutes), and recovery (T2, 5 minutes).
LF power inter-site agreement across chest, finger, and arm recordings
Low-frequency (LF) power derived from simultaneous recordings at three sites (chest as reference, finger, and arm) will be compared to determine inter-site agreement and reliability. Agreement will be evaluated using Bland-Altman analysis (bias and limits of agreement), and reliability/consistency will be quantified using intraclass correlation coefficients (ICC). Unit of Measure: ms²
Time frame: During a single session: baseline (T0, 5 minutes), stimulation (T1, 10 minutes), and recovery (T2, 5 minutes).
HF power inter-site agreement across chest, finger, and arm recordings
High-frequency (HF) power derived from simultaneous recordings at three sites (chest as reference, finger, and arm) will be compared to determine inter-site agreement and reliability. Agreement will be evaluated using Bland-Altman analysis (bias and limits of agreement), and reliability/consistency will be quantified using intraclass correlation coefficients (ICC). Unit of Measure: ms²
Time frame: During a single session: baseline (T0, 5 minutes), stimulation (T1, 10 minutes), and recovery (T2, 5 minutes).
LF/HF ratio inter-site agreement across chest, finger, and arm recordings
The low-frequency to high-frequency ratio (LF/HF ratio) derived from simultaneous recordings at three sites (chest as reference, finger, and arm) will be compared to determine inter-site agreement and reliability. Agreement will be evaluated using Bland-Altman analysis (bias and limits of agreement), and reliability/consistency will be quantified using intraclass correlation coefficients (ICC). Unit of Measure: unitless
Time frame: During a single session: baseline (T0, 5 minutes), stimulation (T1, 10 minutes), and recovery (T2, 5 minutes).
Systolic blood pressure
Systolic blood pressure will be measured to characterize hemodynamic responses during the single-session protocol, including baseline, stimulation, and recovery periods. Unit of Measure: mmHg.
Time frame: Single session: baseline (5 minutes), stimulation (10 minutes), and recovery (5 minutes)
Diastolic blood pressure
Diastolic blood pressure will be measured to characterize hemodynamic responses during the single-session protocol, including baseline, stimulation, and recovery periods. Unit of Measure: mmHg.
Time frame: Single session: baseline (5 minutes), stimulation (10 minutes), and recovery (5 minutes).
Heart rate during transcutaneous auricular vagus nerve stimulation
Heart rate will be recorded to characterize cardiovascular responses during the single-session protocol, including baseline, stimulation, and recovery periods. Unit of Measure: beats per minute (bpm).
Time frame: Single session: baseline (5 minutes), stimulation (10 minutes), and recovery (5 minutes).
Plan to share: No — Individual participant data (IPD) will not be shared at this time. Only aggregated, de-identified results will be reported in publications. The dataset includes sensitive physiological measurements, and access will be limited to the research team to protect participant privacy. IPD sharing may be reconsidered in the future upon reasonable request and with appropriate ethical and institutional approvals.
Started Mar 2023 (actual). Primary completion is estimated for Apr 2026, 37 months after the start.
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