AED and text message responders density in residential areas for rapid response in out-of-hospital cardiac arrest

Background: For out-of-hospital cardiac arrest (OHCA) in residential areas, a dispatcher driven alert-system using text messages (TM-system) directing local rescuers (TM-responders) to OHCA patients was implemented and the desired density of automated external defibrillators (AEDs) or TM-responders investigated. Methods: We included OHCA cases with the TM-system activated in residential areas between 2010–2017. For each case, densities/km2 of activated AEDs and TM-responders within a 1000 m circle were calculated. Time intervals between 112-call and first defibrillation were calculated. Results: In total, 813 patients (45%) had a shockable initial rhythm. In 17% a TM-system AED delivered the first shock. With increasing AED density, the median time to shock decreased from 10:59 to 08:17 min. (p 2 AEDs/km2 did not result in further decrease of time to first shock but >10 TM-responders/km2 resulted in more defibrillations 10 TM-responders/km2