Bystanders play a vital role in public access defibrillation (PAD) in out-of-hospital cardiac arrest (OHCA). Dual dispatch of first responders (FR) alongside emergency medical services (EMS) can reduce time to first defibrillation. The aim of this study was to describe the use of automated external defibrillators (AEDs) in OHCAs before EMS arrival.

All OHCA cases with a shockable rhythm in which an AED was used prior to the arrival of EMS between 2008 and 2015 in western Sweden were eligible for inclusion. Data from the Swedish Register for Cardiopulmonary Resuscitation (SRCR) were used for analysis, on-site bystander and FR defibrillation were compared with EMS defibrillation in the final analysis.

Of the reported 6675 cases, 24% suffered ventricular fibrillation (VF), 162 patients (15%) of all VF cases were defibrillated before EMS arrival, 46% with a public AED on site. The proportion of cases defibrillated before EMS arrival increased from 5% in 2008 to 20% in 2015 (p<0.001). During this period, 30-day survival increased in patients with VF from 22% to 28% (p=0.04) and was highest when an AED was used on site (68%), with a median delay of 6.5min from collapse to defibrillation. Adjusted odds ratio for on-site defibrillation versus dispatched defibrillation for 30-day survival was 2.45 (95% CI: 1.02–5.95).

The use of AEDs before the arrival of EMS increased over time. This was associated with an increased 30-day survival among patients with VF. Thirty-day survival was highest when an AED was used on site before EMS arrival.