• Purpose of the study This study aimed to investigate electrocardiogram measurement and subthreshold low-level autonomic nerve stimulation using external auditory canal electrodes among healthy adult participants

• Study design Prospective, single-center, interventional, single-arm design

• Study participants A total of 12 healthy adult participants without cardiovascular diseases will be recruited.

• Study methods

  1. Participant enrollment Study participants will be recruited by advertisement posters announced at the lobby of the hospital
  2. Evaluation of electrocardiogram measurement from external auditory canal electrodes Participants are required to attach specially designed external auditory canal electrodes to their both ears to record electrocardiogram. Both electrocardiogram from the precordium and the ear would be simultaneously recorded and compared.
  3. Evaluation of low-level autonomic nerve stimulation using external auditory canal Using the electrodes described above, Arnold's nerve will be stimulated with low-level electric impulses using TENS device. During and after the stimulation, heart rate variability will be measured to investigate the impact of nerve stimulation on autonomic function modulation on the heart.

Inclusion Criteria:

• Healthy adults without cardiovascular diseases
• Aged 20 years or more with Informed consent

Exclusion Criteria:

• Patients with autonomic disorder, cardiovascular drug prescriptions, cardiovascular diseases, diabetes, or with cardiac implantable electronic devices
• Patients with abnormalities at both external auditory canals and ears

IPD will be available upon appropriateness of the request.