Alert system-supported lay defibrillation and basic life-support for cardiac arrest at home

Abstract

Aims: Automated external defibrillators (AEDs) are placed in public, but the majority of out-of-hospital cardiac arrests (OHCA) occur at home.

Methods and results: In residential areas, 785 AEDs were placed and 5735 volunteer responders were recruited. For suspected OHCA, dispatchers activated nearby volunteer responders with text messages, directing two-thirds to an AED first and one-third directly to the patient. We analysed survival (primary outcome) and neurologically favourable survival to discharge, time to first defibrillation shock, and cardiopulmonary resuscitation (CPR) before Emergency Medical Service (EMS) arrival of patients in residences found with ventricular fibrillation (VF), before and after introduction of this text-message alert system. Survival from OHCAs in residences increased from 26% to 39% {adjusted relative risk (RR) 1.5 [95% confidence interval (CI): 1.03-2.0]}. RR for neurologically favourable survival was 1.4 (95% CI: 0.99-2.0). No CPR before ambulance arrival decreased from 22% to 9% (RR: 0.5, 95% CI: 0.3-0.7). Text-message-responders with AED administered shocks to 16% of all patients in VF in residences, while defibrillation by EMS decreased from 73% to 39% in residences (P < 0.001). Defibrillation by first responders in residences increased from 22 to 40% (P < 0.001). Use of public AEDs in residences remained unchanged (6% and 5%) (P = 0.81). Time from emergency call to defibrillation decreased from median 11.7 to 9.3 min; mean difference -2.6 (95% CI: -3.5 to -1.6).

Conclusion: Introducing volunteer responders directed to AEDs, dispatched by text-message was associated with significantly reduced time to first defibrillation, increased bystander CPR and increased overall survival for OHCA patients in residences found with VF.

Keywords: Automated external defibrillator; Cardiopulmonary resuscitation; Defibrillation; Dispatch; Heart arrest; Ventricular fibrillation; Volunteer responder.

Structured Graphical Abstract

A summary of the key design features and outcomes of introduction of volunteer responders to the EMS response for OHCA in residences. In the left panel (pre-introduction, blue) only EMS and first responders were dispatched to the residence of the suspected OHCA. In the right panel (post-introduction, orange) nearby volunteer responders (red) with access to nearby AEDs were alerted with a text-message in addition to the conventional responders. The time interval between 112 call and the first delivered defibrillation shock is indicated with the patient, survival and absence of CPR before EMS arrival is shown in the lower part, both as percentage and as Relative Risk with the associated 95% CI. CI, Confidence Interval; CPR, cardio-pulmonary resuscitation; EMS, Emergency Medical Services; OHCA, Out-of-hospital cardiac arrest; ref, reference group.

Figure 1

Stepped wedge cluster design. The text-message alert system was introduced stepwise in 26 municipalities between July 2009 and March 2013, followed by a 6-month transition period, indicated by the dark grey bar. The white bar is the pre-introduction period, the light grey bar the post-introduction period used in the analysis. The number in each bar represents the number of cases (ventricular fibrillation, residential and public). The observation period started 1 January 2008 and ended 28 February 2015.

Figure 2

Flow of patients before and after introduction of the text-message alert system, excluding the run-in period. EMS, emergency medical service.

Figure 3

Cumulative time interval between emergency medical service call and the first defibrillation shock. The numbers between brackets in the legend indicate the number of patients of which this time interval was known and contributed to the figure. (A) The cumulative time interval for the first defibrillation shock in residencies and (B) the first defibrillation shock in public. The cumulative percentage was >0% at 0 min, if an onsite automated external defibrillators provided a defibrillation shock before the dispatch centre was called. Shortening of the time to first shock in residences started to occur after ∼7 min, coinciding with the observed arrival of first responders and text-message responders. In public, the earliest defibrillation of onsite automated external defibrillators already was done before the dispatch centre was alerted.