Turnout time in smartphone alerting systems: underestimated entity in the development of smartphone-related dispatch algorithms.

Introduction: Smartphone alerting systems (SAS) for out-of-hospital cardiac arrest (OHCA) are requiring continuous further development. One important element herein is the algorithm, dispatching only those community first responders (CFR) capable of reaching the scene within the shortest possible time. Currently, no data exist regarding the interval between the initial alert and departure to the scene (=turnout time, ToT), despite the critical importance of this information for optimizing dispatch algorithms.

Methods: In this retrospective observational study, 4138 operations of CFR who participated in the SAS "Region of Lifesavers" between 01 August 2023 and 15 March 2024 were analysed. Upon receiving an alert, a CFR smartphone was tracked via Global Positioning System (GPS). Turnout was recorded when the device left a fenced area of 20 m from the alert acceptance point. Ethical approval was obtained (DRKS00032957).

Results: The median ToT was 1:45 min, which corresponds to one third of the response time (1:45 of 5:22 min). Nighttime had the strongest influence, with significantly longer ToT (2:22 min) compared to daytime (1:42 min, p < 0.001). The day of the week, mode of transport, and assigned task had a minimal impact.

Conclusion: The ToT has a relevant proportion of the response time until CFR arrive at the scene. Relevant factors influencing the ToT were identified and should be taken into account when developing smart alerting algorithms to ensure the efficient dispatch of CFR.