taVNS During Multi-site HRV Measurement: Reliability & Agreement Study (taVNS-HRV)

April 21, 2026 updated by: SEFA HAKTAN HATIK

Assessment of Reliability and Agreement of Autonomic Measures Across Different Anatomical Sites During Transcutaneous Auricular Vagus Nerve Stimulation

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.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Enrolling by invitation

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

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.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
1

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Turkey (Türkiye)
      • Sinop, Turkey (Türkiye), 57900
        • Güzelyurt Neighborhood, Mustafa Bozkurt Street, No: 9, Türkeli, Sinop, Türkiye

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Age 18 to 40 years.
  • Healthy volunteers without known chronic disease or acute illness at the time of participation.
  • Able and willing to comply with study procedures and instructions.
  • Provided written informed consent.

Exclusion Criteria:

  • Any cardiovascular disease, arrhythmia, hypertension, or similar condition. Any neurological disorder (e.g., diabetes mellitus, peripheral neuropathy, epilepsy).
  • Any diagnosed psychiatric disorder.
  • Pregnancy or suspected pregnancy.
  • Ear conditions that prevent stimulation (infection, open wound, pain/tenderness) or the presence of a piercing at/near the stimulation site.
  • Vigorous exercise within 24 hours prior to the measurement.
  • Caffeine intake, smoking, or alcohol consumption within 4-6 hours prior to the measurement.
  • Marked intolerance or hypersensitivity to the devices or the procedure.
  • Inability to follow instructions during measurements or refusal to complete the session.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Other
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Transcutaneous Auricular Vagus Nerve Stimulation - Single Session
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.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
RMSSD inter-site agreement across chest, finger, and arm recordings
Time Frame: During a single session: baseline (T0, 5 minutes), stimulation (T1, 10 minutes), and recovery (T2, 5 minutes).
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
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
Time Frame: During a single session: baseline (T0, 5 minutes), stimulation (T1, 10 minutes), and recovery (T2, 5 minutes).
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
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
Time Frame: During a single session: baseline (T0, 5 minutes), stimulation (T1, 10 minutes), and recovery (T2, 5 minutes).
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
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
Time Frame: During a single session: baseline (T0, 5 minutes), stimulation (T1, 10 minutes), and recovery (T2, 5 minutes).
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
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
Time Frame: During a single session: baseline (T0, 5 minutes), stimulation (T1, 10 minutes), and recovery (T2, 5 minutes).
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
During a single session: baseline (T0, 5 minutes), stimulation (T1, 10 minutes), and recovery (T2, 5 minutes).

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Systolic blood pressure
Time Frame: Single session: baseline (5 minutes), stimulation (10 minutes), and recovery (5 minutes)
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.
Single session: baseline (5 minutes), stimulation (10 minutes), and recovery (5 minutes)
Diastolic blood pressure
Time Frame: Single session: baseline (5 minutes), stimulation (10 minutes), and recovery (5 minutes).
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.
Single session: baseline (5 minutes), stimulation (10 minutes), and recovery (5 minutes).
Heart rate during transcutaneous auricular vagus nerve stimulation
Time Frame: Single session: baseline (5 minutes), stimulation (10 minutes), and recovery (5 minutes).
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).
Single session: baseline (5 minutes), stimulation (10 minutes), and recovery (5 minutes).

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
SEFA HAKTAN HATIK

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
March 20, 2023

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
April 20, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
May 5, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
February 22, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
April 21, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
April 23, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
April 23, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
April 21, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
April 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • taVNS1
  • BEU-ETH 2026/01-11 (Other Identifier: Bitlis Eren University Non-Interventional Clinical Research Ethics Committee)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

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.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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