Evaluating the implementation and effectiveness of dispatching EMS volunteers via "interconnected first-aid app" on the outcome of out-of-hospital cardiac arrest patients: protocol for a type II hybrid implementation-effectiveness study.

INTRODUCTION: Out-of-hospital cardiac arrest (OHCA) poses a critical public health challenge globally, with survival rates in China being significantly lower than that in high-income countries. Delayed emergency response, low bystander Cardio Pulmonary Resuscitation (CPR) rates, and limited AED accessibility contribute to poor outcomes. Leveraging smart technology to mobilize trained volunteers via mobile applications has emerged as a promising strategy to bridge these gaps. However, in urban contexts within China, there remains a scarcity of implementation evidence encompassing aspects such as adoption, contextual barriers, and sustainability. This shortage of evidence hinders the integration of policies and systems at the policy and system levels. This study aims to improve the survival rates of OHCA patients in China, by designing, implementing and evaluating the effectiveness of an optimized "Interconnected First-Aid App" dispatching EMS volunteers through a stepped-wedge cluster randomized trial. METHODS AND ANALYSIS: A stepped-wedge cluster randomized controlled trial will be conducted in 24 streets/townships across three districts in Shaoguan, China. The 24 streets/townships will be randomly assigned to four clusters, and each cluster will receive staggered interventions over 18 months, including volunteer recruitment/training, app-AED-EMS integration, and community education step by step. The trial adopts the PEDALS framework (Problem, Evidence-based Practice, Determinants, Action, Long-term, Scale) to assess both implementation processes and clinical outcomes. Primary outcomes include survival rates, bystander CPR/AED utilization, and response times. Implementation outcomes will evaluate adoption, feasibility, and sustainability through surveys, interviews, and health system data analysis. Findings will inform scalable, context-adapted implementation strategies for community-based OHCA response, particularly leveraging digital health innovations to address inequities in emergency care access in low- and middle-income settings. ETHICS AND DISSEMINATION: This protocol was approved by the Biomedical Research Ethics Committee of Peking University First Hospital (2025R0017-0001). Findings will be disseminated through traditional academic pathways, including peer-reviewed publications and conference presentations, with policy briefings prepared for stakeholders and leaders at the local, provincial and national levels. TRIAL REGISTRATION: The study is registered with the Chinese Clinical Trial Registry under the ID ChiCTR2500101187, registered on April 21, 2025.