Healthy Volunteers
Conditions
Brief summary
This randomized, participant-blinded, sham-controlled crossover study aims to investigate the acute effects of different frequency applications of transcutaneous auricular vagus nerve stimulation (taVNS) on autonomic physiological responses in healthy adults. Participants will receive sham (0 Hz), 10 Hz, 25 Hz, 50 Hz, and 100 Hz taVNS in separate sessions with washout periods between visits. Heart rate variability, blood pressure, pulse rate, respiratory rate, and subjective discomfort will be assessed before and after each intervention session.
Detailed description
The vagus nerve is a major regulator of the parasympathetic branch of the autonomic nervous system. Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neuromodulation technique applied to auricular regions innervated by the auricular branch of the vagus nerve. Although taVNS has been reported to modulate autonomic function, the acute physiological effects of different stimulation frequencies remain insufficiently characterized. This study is designed as a randomized, participant-blinded, sham-controlled crossover trial in healthy adults aged 18 to 40 years. Each participant will undergo five intervention conditions in randomized order: sham (0 Hz), 10 Hz, 25 Hz, 50 Hz, and 100 Hz taVNS. Sessions will be separated by 48 to 72 hours to minimize carryover effects. Each stimulation session will last 10 minutes. Primary autonomic outcomes will be derived from heart rate variability parameters obtained using a Polar H10 chest strap and analyzed with Kubios HRV software. Secondary physiological outcomes will include systolic and diastolic blood pressure, pulse rate, respiratory rate, and subjective discomfort measured using a visual analog scale. The study aims to identify frequency-specific autonomic response profiles and to evaluate whether respiratory rate influences heart rate variability changes associated with taVNS.
Interventions
DEVICESham taVNS
Sham stimulation is delivered under conditions similar to active taVNS without meaningful vagal stimulation.
DEVICEtaVNS 10 Hz
Active transcutaneous auricular vagus nerve stimulation applied for 10 minutes at 10 Hz.
DEVICEtaVNS 25 Hz
Active transcutaneous auricular vagus nerve stimulation applied for 10 minutes at 25 Hz.
DEVICEtaVNS 50 Hz
Active transcutaneous auricular vagus nerve stimulation applied for 10 minutes at 50 Hz.
DEVICEtaVNS 100 Hz
Active transcutaneous auricular vagus nerve stimulation applied for 10 minutes at 100 Hz.
Sponsors
Sinop University
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
SINGLE (Subject)
Masking description
Participants will be blinded to whether the intervention session involves active taVNS or sham stimulation. The care provider/investigator cannot be blinded because of the technical requirements of device application and condition setup.
Intervention model description
Each participant will receive all five intervention conditions (sham, 10 Hz, 25 Hz, 50 Hz, and 100 Hz taVNS) in randomized order across separate visits, with a 48- to 72-hour washout period between sessions.
Eligibility
Sex/Gender
ALL
Age
18 Years to 40 Years
Healthy volunteers
Yes
Inclusion criteria
* Healthy adults aged 18 to 40 years * No known neurological, cardiovascular, respiratory, or metabolic disease * Able to understand study procedures and provide written informed consent * No active infection, open wound, or dermatological lesion in the ear region that would interfere with taVNS application * Willing and able to attend all study visits
Exclusion criteria
* History of cardiac arrhythmia, pacemaker, or any implanted electronic medical device History of hypertension, diabetes, chronic pulmonary disease, epilepsy, or systemic disease affecting autonomic nervous system function * Regular use of medications that may affect autonomic function (e.g., beta-blockers, antidepressants, antiarrhythmics) * Intense physical exercise within the previous 24 hours * High caffeine or alcohol intake within 12 hours prior to assessment * Active smoking on the assessment day * Pregnancy or suspected pregnancy * Severe discomfort during stimulation (VAS \>= 7), dizziness, nausea, or unwillingness to continue * Any condition judged by the investigators to make participation unsuitable'
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in Root Mean Square of Successive Differences (RMSSD) | Immediately before and immediately after each 10-minute intervention session | Change in the root mean square of successive differences (RMSSD) from pre-intervention to post-intervention under each stimulation condition. |
| Change in High-Frequency Heart Rate Variability (HF-HRV) | Immediately before and immediately after each 10-minute intervention session | Change in high-frequency heart rate variability (HF-HRV) from pre-intervention to post-intervention under each stimulation condition. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in Standard Deviation of Normal-to-Normal RR Intervals (SDNN) | Immediately before and immediately after each 10-minute intervention session | Change in the standard deviation of normal-to-normal RR intervals (SDNN) from pre-intervention to post-intervention under each stimulation condition. |
| Change in Low-Frequency (LF) Power | Immediately before and immediately after each 10-minute intervention session | Change in low-frequency (LF) power of heart rate variability from pre-intervention to post-intervention under each stimulation condition. |
| Change in LF/HF Ratio | Immediately before and immediately after each 10-minute intervention session | Change in the ratio of low-frequency to high-frequency heart rate variability (LF/HF ratio) from pre-intervention to post-intervention under each stimulation condition. |
| Change in Systolic Blood Pressure | Immediately before and immediately after each 10-minute intervention session | Change in systolic blood pressure from pre-intervention to post-intervention under each stimulation condition. |
| Change in Diastolic Blood Pressure | Immediately before and immediately after each 10-minute intervention session | Change in diastolic blood pressure from pre-intervention to post-intervention under each stimulation condition. |
| Change in Pulse Rate | Immediately before and immediately after each 10-minute intervention session | Change in pulse rate from pre-intervention to post-intervention under each stimulation condition. |
| Change in Respiratory Rate | Immediately before and immediately after each 10-minute intervention session | Change in respiratory rate from pre-intervention to post-intervention under each stimulation condition. |
| Change in Subjective Discomfort Assessed by Visual Analog Scale (VAS) | Immediately before and immediately after each 10-minute intervention session | Subjective discomfort will be assessed using a Visual Analog Scale (VAS) ranging from 0 to 10, where 0 indicates no discomfort and 10 indicates the worst possible discomfort. Higher scores indicate greater discomfort. Change in VAS score from pre-intervention to post-intervention will be evaluated under each stimulation condition. |
Countries
Turkey (Türkiye)
Contacts
CONTACTSefa Haktan Hatık, MSc, PhD
Outcome results
None listed