Firefighters as first-responders in out-of-hospital cardiac arrest - A retrospective study of a time-gain selective dispatch system in the Skåne Region, Sweden

To analyze the impact of a time-gain selective, first-responder dispatch system on the presence of a shockable initial rhythm (SIR), return of spontaneous circulation (ROSC) and 30-day survival after out-of-hospital cardiac arrest (OHCA).A retrospective observational study comprising OHCA registry data and dispatch data in the Skåne Region, Sweden (2010-2018). Data were categorized according to dispatch procedures, two ambulances (AMB-only) versus two ambulances and firefighter first-responders (DUAL-dispatch), based on the dispatcher's estimation of a time-gain. Dual dispatch was sub-categorized by arrival of first vehicle (first-responder or ambulance). Logistic regressions were used, additionally with groups matched (1:1) for age, sex, location, witnessed event, bystander cardiopulmonary resuscitation and ambulance response time. Adjusted and conditional odds-ratios (aOR, cOR) with 95% confidence intervals (CI) are presented.Of 3,245 eligible cases, 43% were DUAL-dispatches with first-responders first on scene (FR-first) in 72%. Despite a five-minute median reduction in response time in the FR-first group, no association with SIR was found (aOR 0.83, 95%CI 0.64-1.07) nor improved 30-day survival (aOR 1.03, 95%CI 0.72-1.47). A positive association between ROSC and the FR-first group (aOR 1.25, 95%CI 1.02-1.54) disappeared in the matched analysis (cOR 1.12, 95%CI 0.87-1.43). Time to first monitored rhythm was 7:06 minutes in the FR-first group versus 3:01 in the combined AMB-only/AMB-first groups.In this time-gain selective first-responder dispatch system, a shorter response time was not associated with increased SIR, improved ROSC rate or survival. Process measures differed between the study groups which could account for the observed findings and requires further investigation.