Dispatching trained volunteer responders via smartphones to retrieve automated external defibrillators for patients in out-of-hospital cardiac arrest (OHCA) did not significantly increase bystander AED use in a randomized clinical trial in Sweden.
Most patients in OHCA can be saved if cardiopulmonary resuscitation and defibrillation are initiated within minutes, but despite the “substantial” public availability of AEDs and widespread CPR training among the Swedish public, use rates of both are low, Mattias Ringh, MD, PhD, of Karolinska Institutet in Stockholm, and colleagues wrote.
A previous study by the team showed that dispatching volunteer responders via a smartphone app significantly increased bystander CPR. The current study, called the Swedish AED and Mobile Bystander Activation (SAMBA) trial, aimed to see whether dispatching volunteer responders to collect a nearby AED would increase bystander AED use. A control group of volunteer responders was instructed to go straight to the scene and start CPR.
“The results showed that the volunteer responders were first to provide treatment with both CPR and AEDs in a large proportion of cases in both groups, thereby creating a ‘statistical’ dilutional effect,” Dr. Ringh said in an interview. In effect, the control arm also became an active arm.
“But if we agree that treatment with AEDs and CPR is saving lives, then dispatching volunteer responders is doing just that, although we could not fully measure the effect in our study,” he added.
The study was published online in JAMA Cardiology.
No significant differences
The SAMBA trial assessed outcomes of the smartphone dispatch system (Heartrunner), which is triggered at emergency dispatch centers in response to suspected OHCAs at the same time that an ambulance with advanced life support equipment is dispatched.
The volunteer responder system locates a maximum of 30 volunteer responders within a 1.3-km radius from the suspected out-of-hospital cardiac arrest, the researchers explained in their report. Volunteer responders are requested via their smartphone application to accept or decline the alert. If they accept an alert, the volunteer responders receive map-aided route directions to the location of the suspected arrest.
In patients allocated to intervention in this study, four of five of all volunteer responders who accepted the alert received instructions to collect the nearest available AED and then go directly to the patient with suspected out-of-hospital cardiac arrest, the authors noted. Route directions to the scene of the cardiac arrest and the AED were displayed on their smartphones. One of the 5 volunteer responders, closest to the arrest, was dispatched to go directly to initiate CPR.
In patients allocated to the control group, all volunteer responders who accepted the alert were instructed to go directly to the patient with suspected out-of-hospital cardiac arrest to perform CPR. No route directions to or locations of AEDs were displayed.
The study was conducted in Stockholm and in Västra Götaland from 2018 to 2020. At the start of the study, there were 3,123 AEDs and 24,493 volunteer responders in Stockholm and 3,195 AEDs and 19,117 volunteer responders in Västra Götaland.
Post-randomization exclusions included patients without OHCA, those with OHCAs not treated by emergency medical services, and those with OHCAs witnessed by EMS.
The primary outcome was overall bystander AED attachment before the arrival of EMS, including those attached by the volunteer responders but also by lay volunteers who did not use the smartphone app.
Volunteer responders were activated for 947 individuals with OHCA; 461 patients were randomized to the intervention group and 486 to the control group. In both groups, the patients’ median age was 73 and about 65% were men.
Attachment of the AED before the arrival of EMS or first responders occurred in 61 patients (13.2%) in the intervention group versus 46 (9.5%) in the control group (P = .08). However, the majority of all AEDs were attached by lay volunteers who were not volunteer responders using the smartphone app (37 in the intervention arm vs. 28 in the control arm), the researchers noted.
No significant differences were seen in secondary outcomes, which included bystander CPR (69% vs. 71.6%, respectively) and defibrillation before EMS arrival (3.7% vs. 3.9%) between groups.
Among the volunteer responders using the app, crossover was 11% and compliance to instructions was 31%. Overall, volunteer responders attached 38% of all bystander-attached AEDs and provided 45% of all bystander defibrillations and 43% of all bystander CPR.
Going forward, Dr. Ringh and colleagues will be further analyzing the results to understand how to better optimize the logistical challenges involved with smartphone dispatch to OHCA patients. “In the longer term, investigating the impact on survival is also warranted,” he concluded.