An interventional study of Transcutaneous auricular vagus nerve stimulation and Sham transcutaneous auricular stimulation in Vagus Nerve Stimulations, Spirometry and Autonomic Nervous System (ANS) Functioning and Mood State, sponsored by SEFA HAKTAN HATIK. Recruiting at 1 site in Turkey (Türkiye). Open to participants aged 18 Years to 40 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-03-19.
Sponsored by SEFA HAKTAN HATIK · Not applicable, Interventional, and Other
This study will examine the short-term effects of transcutaneous auricular vagus nerve stimulation (a non-invasive electrical stimulation delivered through the outer ear) on lung function measured by spirometry in healthy adults. The vagus nerve is involved in many automatic body functions, and ear-based stimulation has been used in research to explore its possible effects on different physiological systems. However, it is not clear whether a brief stimulation session can acutely influence breathing test results in people without respiratory disease.
Healthy volunteers aged 18-40 will take part in one laboratory visit. Participants will be randomly assigned to one of two groups: (1) active bilateral stimulation applied to specific ear regions that are known to be innervated by the vagus nerve, or (2) sham stimulation using the same device setup but designed to minimize vagal activation. The stimulation session will last approximately 10 minutes. Before and after the stimulation, participants will perform standard spirometry (breathing) tests. Primary spirometric outcomes will include common measures of lung function such as forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and peak expiratory flow (PEF). Heart rate, heart rate variability, and blood pressure may also be recorded to monitor physiological responses and safety during the visit.
Participation is voluntary and participants may withdraw at any time. The procedure is considered minimal risk. Possible side effects are usually mild and temporary, such as tingling, warmth, or mild discomfort at the ear. Rarely, participants may feel lightheaded; if this occurs, the procedure will be stopped and the participant will be monitored until symptoms resolve. There is no guaranteed direct benefit to participants. The results may help clarify whether short-term ear-based vagus nerve stimulation can influence spirometric parameters and may inform future studies on autonomic and respiratory interactions.
Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neuromodulation approach delivered through the external ear. The auricular branch of the vagus nerve provides an accessible peripheral route that may influence autonomic regulation and, through autonomic-respiratory interactions, potentially affect respiratory function. Although taVNS has been investigated across several physiological domains, evidence regarding its acute effects on spirometric outcomes in healthy individuals remains limited. This study is designed to evaluate whether a single, brief session of bilateral taVNS produces measurable short-term changes in standard spirometric parameters compared with a sham procedure.
This is a sham-controlled, randomized, single-blind, parallel-group trial conducted in healthy volunteers. Participants are allocated to either active bilateral taVNS or sham stimulation using a predefined randomization procedure and concealed assignment. To minimize expectancy effects, participants are blinded to group allocation, and active and sham procedures use the same device appearance and session structure. Active stimulation is delivered via electrodes positioned on auricular regions targeted for vagal innervation, whereas sham stimulation uses an alternative placement intended to minimize vagal activation while maintaining a similar sensory experience. Stimulation parameters are standardized across participants, with intensity individually titrated to a clearly perceptible but non-painful level.
The primary outcomes are acute pre-to-post changes in spirometric measures obtained using standardized spirometry procedures. Key spirometric endpoints include forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and peak expiratory flow (PEF). Secondary physiological measures may include heart rate, heart rate variability indices, and blood pressure to characterize autonomic and hemodynamic responses and to support safety monitoring during the session. All measurements are collected within the same visit, with spirometry performed immediately before and after the stimulation procedure following consistent instructions and quality criteria.
Data analysis will focus on between-group comparisons of change scores (post minus pre) for spirometric outcomes. Depending on distributional assumptions, analyses will use appropriate parametric or non-parametric methods; when relevant, models adjusting for baseline values will be applied (e.g., ANCOVA with baseline spirometry as a covariate). Effect sizes and confidence intervals will be reported to support interpretability. Safety will be monitored throughout the visit; stimulation will be discontinued if a participant experiences significant discomfort or requests stopping.
The study involves minimal risk. Expected adverse effects are transient and mild (e.g., localized tingling or mild discomfort at the ear). Rarely, lightheadedness may occur; participants will be monitored and the procedure stopped if necessary. Data will be stored in a coded/de-identified format and 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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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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.
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
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.
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.
COPD
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
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.
Participants receive active bilateral transcutaneous auricular vagus nerve stimulation using an external stimulator. Electrodes are placed on auricular regions targeted for vagal innervation (bilaterally). Stimulation is applied for approximately 10 minutes with standardized parameters and individually adjusted intensity to a clearly perceptible but non-painful level. Spirometry (e.g., FVC, FEV1, PEF) is performed before and after the session; heart rate, heart rate variability, and blood pressure may also be recorded.
Device: Transcutaneous auricular vagus nerve stimulation
Participants receive sham stimulation using the same device appearance and session structure. Electrodes are placed on an ear location intended to minimize vagal activation (e.g., ear lobule), and stimulation is delivered at a minimal/low level to mimic sensation without therapeutic stimulation. The same pre- and post-session spirometry and physiological measurements are collected as in the active arm.
Device: Sham transcutaneous auricular stimulation
Transcutaneous auricular vagus nerve stimulation is delivered bilaterally using an external stimulator with electrodes placed on auricular regions targeted for vagal innervation (e.g., cymba conchae). Stimulation is applied for approximately 10 minutes. Parameters are standardized (e.g., 25 Hz; pulse width 200-300 microseconds), and current intensity is individually adjusted to a clearly perceptible but non-painful level. The procedure is performed in a single visit with pre- and post-intervention spirometry and physiological monitoring as specified in the protocol.
Sham stimulation uses the same device, setup, and session duration to mimic the active procedure. Electrodes are placed on an ear location intended to minimize vagal activation (e.g., ear lobule), and stimulation is delivered at a minimal/low level to provide a similar sensation without therapeutic vagal stimulation. Pre- and post-session spirometry and other measurements are collected identically to the active arm.
Change in forced expiratory volume in 1 second (FEV1)
Forced expiratory volume in 1 second (FEV1), reported in liters (L), will be measured immediately before and immediately after the intervention. The outcome will be defined as the pre-to-post change (post minus pre), and between-group differences in change between active stimulation and sham control will be evaluated.\[FVC\], and peak expiratory flow \[PEF\]) will be measured immediately before and immediately after the intervention. The primary endpoint is the pre-to-post change (post minus pre) and the between-group difference in change between active stimulation and sham control.
Time frame: Single visit: assessed pre-intervention and immediately post-intervention (within the same session).
Change in forced vital capacity (FVC)
Forced vital capacity (FVC), reported in liters (L), will be measured immediately before and immediately after the intervention. The outcome will be defined as the pre-to-post change (post minus pre), and between-group differences in change between active stimulation and sham control will be evaluated.
Time frame: Single visit: assessed pre-intervention and immediately post-intervention (within the same session).
Change in peak expiratory flow (PEF)
Peak expiratory flow (PEF), reported in liters per minute (L/min), will be measured immediately before and immediately after the intervention. The outcome will be defined as the pre-to-post change (post minus pre), and between-group differences in change between active stimulation and sham control will be evaluated.
Time frame: Single visit: assessed pre-intervention and immediately post-intervention (within the same session).
Change in RMSSD from chest recordings
Heart rate variability will be recorded from chest-based beat-to-beat intervals before and after the intervention in a standardized resting condition. The root mean square of successive differences (RMSSD), reported in milliseconds (ms), will be derived from these recordings. The endpoint is the pre-to-post change (post minus pre) and the between-group difference in change between active bilateral stimulation and sham control.
Time frame: Single visit: assessed pre-intervention and immediately post-intervention (within the same session).
Change in SDNN from chest recordings
Heart rate variability will be recorded from chest-based beat-to-beat intervals before and after the intervention in a standardized resting condition. The standard deviation of normal-to-normal intervals (SDNN), reported in milliseconds (ms), will be derived from these recordings. The endpoint is the pre-to-post change (post minus pre) and the between-group difference in change between active bilateral stimulation and sham control.
Time frame: Single visit: assessed pre-intervention and immediately post-intervention (within the same session).
Change in LF power from chest recordings
Heart rate variability will be recorded from chest-based beat-to-beat intervals before and after the intervention in a standardized resting condition. Low-frequency (LF) power, reported in milliseconds squared (ms²), will be derived from these recordings. The endpoint is the pre-to-post change (post minus pre) and the between-group difference in change between active bilateral stimulation and sham control.
Time frame: Single visit: assessed pre-intervention and immediately post-intervention (within the same session).
Change in HF power from chest recordings
Heart rate variability will be recorded from chest-based beat-to-beat intervals before and after the intervention in a standardized resting condition. High-frequency (HF) power, reported in milliseconds squared (ms²), will be derived from these recordings. The endpoint is the pre-to-post change (post minus pre) and the between-group difference in change between active bilateral stimulation and sham control.
Time frame: Single visit: assessed pre-intervention and immediately post-intervention (within the same session).
Change in LF/HF ratio from chest recordings
Heart rate variability will be recorded from chest-based beat-to-beat intervals before and after the intervention in a standardized resting condition. The low-frequency/high-frequency (LF/HF) ratio, reported as a unitless measure, will be derived from these recordings. The endpoint is the pre-to-post change (post minus pre) and the between-group difference in change between active bilateral stimulation and sham control.
Time frame: Single visit: assessed pre-intervention and immediately post-intervention (within the same session).
Change in systolic blood pressure (SBP)
Systolic blood pressure (SBP), reported in millimeters of mercury (mmHg), will be measured before and after the intervention under standardized conditions. The endpoint is the pre-to-post change (post minus pre) and the between-group difference in change between active stimulation and sham control.
Time frame: Single visit: assessed pre-intervention and immediately post-intervention (within the same session).
Change in diastolic blood pressure (DBP)
Diastolic blood pressure (DBP), reported in millimeters of mercury (mmHg), will be measured before and after the intervention under standardized conditions. The endpoint is the pre-to-post change (post minus pre) and the between-group difference in change between active stimulation and sham control.
Time frame: Single visit: assessed pre-intervention and immediately post-intervention (within the same session).
Change in heart rate
Heart rate, reported in beats per minute (bpm), will be measured before and after the intervention under standardized conditions. The endpoint is the pre-to-post change (post minus pre) and the between-group difference in change between active stimulation and sham control.
Time frame: Single visit: assessed pre-intervention and immediately post-intervention (within the same session).
Plan to share: No — Individual participant data (IPD) will not be publicly shared at this time. Study results will be reported in the manuscript in aggregated form. De-identified IPD may be made available upon reasonable request by contacting the corresponding author, subject to appropriate ethical and institutional approvals and data-use conditions.
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