Direct medical control using video conferencing capabilities of smartphones has never been conducted in out-of-hospital cardiac arrest patients. This study was conducted to investigate its feasibility and treatment effectiveness in out-of-hospital cardiac arrest (OHCA) patients using a real-time smartphone video call.

If cardiac arrest is suspected, the EMS personnel contacted the medical director before arriving at the scene. Upon the arrival at the scene of the two activated paramedic teams, they rapidly switch to ALS under teamwork-based BLS and video medical control. Using this video medical control, high-quality CPR, cardiac arrest rhythm confirmation, defibrillation, proper drug administration instructions, advanced airway insertion, etc. are performed. The medical director then decides on patient transfer if the asystole and pulseless electrical activity findings are persistent even after more than 20-minutes of ALS. After initiating the transfer, the medical director contacts the hospital where the patient is to be transferred to after completing the video medical control. The medical director provides an explanation of the treatment to the caregiver via video. After returning to the fire station, the EMS personnel who had completed the patient's transfer the enters the information by hand on the separate form, takes a picture of the document, and uploads it to SNS within 24 hours. Through this information shared via SNS, the research staff the provides a direct feedback to the EMS personnel, and further discussion performed within the SNS. All the incident cases of OHCA during the before and during interventional periods were registered using an EMS run sheet for basic ambulance operation information, the EMS cardiac arrest registry for the Utstein factors, and the OHCA registry for the hospital care and survival outcomes. The EMS run sheet and EMS cardiac arrest registry were collected by the EMS providers. The medical records for hospital care and outcomes were abstracted by the trained reviewer for this study

Inclusion Criteria:

• all EMS-treated OHCA patients older than 18 years transported to the hospital unless otherwise diagnosed with trauma, poisoning, asphyxia, hanging, or any other non-disease-origin factors.

Exclusion Criteria:

• Patients with do-not-resuscitate (DNR) orders and with obvious signs of irreversible death, including rigor mortis and corruption