KATRETTER

KATRETTER is a Berlin-based smart city project that deploys a smartphone-based volunteer alert system to improve emergency response times for cardiac arrest and other life-threatening medical emergencies. The system works by notifying registered, trained volunteers who are in the vicinity of an emergency when the professional ambulance service is dispatched, enabling them to reach the patient and begin life-saving first aid — particularly cardiopulmonary resuscitation (CPR) and automated external defibrillator (AED) use — before the ambulance arrives. In cardiac arrest cases, every minute without intervention reduces survival chances by approximately ten per cent, making the gap between emergency call and ambulance arrival critically important. KATRETTER bridges this gap by leveraging the ubiquity of smartphones and the willingness of trained citizens to help. Volunteers register through the KATRETTER app, verify their first aid qualifications, and receive GPS-based alerts when an emergency occurs within a defined radius. The app guides volunteers to the patient's location and to the nearest AED device, providing real-time navigation and instructions. The system integrates with Berlin's official emergency dispatch centre (Leitstelle), ensuring that volunteer activation complements rather than replaces professional emergency medical services. Data from each activation is anonymised and analysed to improve response patterns, optimise AED placement across the city, and identify areas where additional volunteer recruitment would be beneficial. The project aligns with Berlin's smart city strategy of using digital technology to enhance public safety and community resilience. It demonstrates how relatively simple mobile technology, combined with civic engagement and professional emergency service integration, can save lives in dense urban environments. KATRETTER has been recognised as a model for community-based emergency response systems across Germany and Europe.