A Study on the Impact of a New Canton-Wide First Responder System in Zug, Switzerland, on Survival After Adult Cardiac Arrest-Examining Early Life-Saving Organized Help, Fast Defibrillation, and Improved Outcomes for Out of Hospital Cardiac Arrest

REVIVE Zug: Improving Emergency Response for Out-of-Hospital Cardiac Arrest Out-of-hospital cardiac arrest (OHCA) represents one of the most time-critical medical emergencies, where rapid recognition and immediate intervention are decisive for survival and neurological outcome. Early activation of emergency services, prompt initiation of cardiopulmonary resuscitation, and rapid defibrillation using automated external defibrillators (AEDs) are key components of the chain of survival. In many regions, organized First Responder systems-such as fire services, police forces, and trained lay responders supported by dispatcher-assisted instructions-arrive at the scene before emergency medical services (EMS) and initiate life-saving measures. Evidence from multiple EMS systems indicates that the early involvement of First Responders is associated with higher rates of return of spontaneous circulation (ROSC) and improved survival to hospital discharge with favorable neurological outcomes. Regions with well-established First Responder networks consistently report better OHCA outcomes compared with regions without such systems. In the canton of Zug, a comprehensive First Responder system has recently been implemented alongside an established hybrid EMS response model. In this system, resuscitation efforts are led either by an Emergency Physician (EP) or by a highly trained Critical Care Paramedic (CCP), depending on operational availability. Both roles operate within clearly defined competencies and provide the full scope of advanced prehospital care. This hybrid leadership model offers a unique opportunity to examine whether the professional background of the team leader influences resuscitation outcomes in real-world clinical practice. The REVIVE Zug study aims to evaluate the impact of the canton-wide First Responder system on outcomes following OHCA. Key outcomes of interest include ROSC rates, hospital admission after cardiac arrest, the occurrence of shockable rhythm