Smart Alerting in Smartphone‐Based First Responder Systems and Arrival Before Emergency Medical Services:The ALARM Randomized Clinical Trial

BACKGROUND: Smartphone alerting systems (SAS) aim to increase the proportion of out-of-hospital cardiac arrest (OHCA) cases in which a community first responder (CFR) arrives before emergency medical services (EMS). Many use fixed-radius alerts and ignore estimated arrival times. We compared different alerting strategies to maximize CFR arrival before EMS. METHODS: In a prospective, randomized three-arm trial, smart alerting (SMA) was compared with fixed-radius strategies (600 m and 2500 m). The primary endpoint was the rate of CFR arrival before EMS. In the SMA arm, responders were dispatched based on individually estimated travel times versus expected ambulance time. Binary endpoints were analyzed using chi-square tests, reporting risk differences and 95% confidence intervals; continuous endpoints used non-parametric tests. RESULTS: Across 823 activations, 1482 CFR were dispatched. CFR arrived before EMS in 31%, 57%, and 58% of missions in the 600 m, 2500 m, and SMA groups, respectively. Compared with the 600 m strategy, SMA increased pre-EMS arrival (risk difference +26.8%, 95% CI 18.6-34.4; p < 0.001), whereas no significant difference was observed compared with the 2500 m strategy (risk difference +1.2%, 95% CI -7.0-+9.3; p = 0.80). Response rates were 56%, 83%, and 87%, respectively. In the SMA group, 31% of accepting CFR were excluded because predicted arrival exceeded EMS arrival. Response times were longer with smart alerting reflecting greater dispatch distances. CONCLUSIONS: Smart alerting increased the likelihood of CFR arriving before EMS while reducing dispatches unlikely to achieve pre-EMS arrival. Further research should evaluate its impact on patient outcomes.