Volunteer first-responder activation in out-of-hospital cardiac arrest—a lot of potential and a lot of unknowns

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This editorial refers to ‘The effect of the GoodSAMvolunteer firstresponder app on survival to hospital discharge following out-of-hospital cardiac arrest’ by Christopher M. Smith et al., pp. 20–31.

Immediate initiation of cardiopulmonary resuscitation (CPR) and early defibrillation is pivotal for successful resuscitation with good neurological outcomes following out-of-hospital cardiac arrest (OHCA).^1,2 Over the past years, there has been wide dissemination of automated external defibrillators (AEDs) for public access defibrillation to facilitate bystander defibrillation. Despite these efforts, bystander defibrillation remains low, especially in private homes, where the vast majority of OHCAs occur.³

Evolving mobile phone technology has introduced the opportunity to activate registered volunteer responders who can potentially arrive at the OHCA scene, provide CPR, and use an AED prior to the arrival of the Emergency Medical Services (EMS). Despite very low certainty of the evidence, volunteer responder systems are now strongly recommended by the European Resuscitation Council and American Heart Association, due to the potential impact on patient care and outcomes.^4,5 There is great heterogeneity across volunteer responder systems, likely due to variations in geography, infrastructure, and available software.⁶ Thus, there is large variability between programs regarding characteristics such as the number of activated volunteers per alarm, radius of activation, integration with AED networks, and so forth. Very few of the existing systems have been described in detail in terms of set-up, logistics, and especially interaction with volunteer responders. In addition to the effectiveness of such programs, aspects such as the functionality, practicality, and volunteer responder safety should be studied, described, and disseminated across countries and regions to improve systems.⁷

Smith et al. report data from a large volunteer program in the UK.⁸  The authors are to be congratulated for extracting granular data and reporting findings from one of the most widespread volunteer responder systems in the world, the GoodSAM app, implemented in the UK, Australia, and New Zealand.⁹ In this retrospective, observational study, the authors aimed to examine the association between GoodSAM alert acceptance and chance of survival to hospital discharge in a population of approximately 14.7 million inhabitants served by the London (April 2016–17) and East Midlands Ambulance Services (2018). In London, GoodSAM alerted up to 3 responders within a 200 m radius of suspected OHCA and in East Midlands up to 5 responders within an 800 m radius. The main results were presented as adjusted odds ratios for survival to discharge for cases where volunteer responders accepted an alarm vs. cases where no alert was sent. The main finding was an increased adjusted odds ratio of 3.15 [95% confidence interval (CI) 1.19–8.36] in London and 3.19 (95% CI 1.17–8.73) in East Midlands for survival to hospital discharge if a GoodSAM alert was accepted compared to cases where no alert was sent. Though these results seem very promising, several factors should be carefully considered in the interpretation of the data presented. First, the GoodSam app was very infrequently used in the two study settings, London and East Midlands, respectively. A GoodSAM responder was only alerted in only 6.7% and 22% of confirmed OHCAs. Of these alerts, only 16% and 15% were accepted by a GoodSAM responder corresponding to 1.3% and 4.9% of all confirmed OHCAs, respectively. Secondly, as correctly noted by the authors, one of the chief limitations of the study is related to the low absolute numbers on outcome data with only 9 and 7 cases of survival to discharge in the ‘accepted’ groups in the respective regions, meaning that the observed survival benefit could be due to chance or confounding factors not accounted for in the multivariate model.

Though several observational studies imply increased bystander CPR, bystander defibrillation, and survival through activation of volunteer responders,¹⁰ these findings must be interpreted with caution as observational studies report associations and not causality. Specifically, identifying a non-biased control group in observational studies of volunteer responders is a real challenge.¹¹ For volunteer responder systems to improve OHCA outcome, a volunteer responder needs not only to arrive before the EMS or professional first responders (police/firefighters) but also within a timeframe that enables a clinically meaningful difference for patient outcomes. In the study by Smith et al., no reliable data were available to determine if a GoodSAM responder arrived before EMS and whether alerted responders performed CPR or defibrillation before EMS arrival. Accepting an alarm (the exposure of the current study) does not necessarily translate into bystander CPR or defibrillation before EMS arrival. In New Zealand and Australia, 27% of volunteer responders arrived before EMS and 14% provided care to the patient.¹² In a comparable volunteer responder system from Denmark, only cases where volunteer responders accepted an alarm were included. OHCAs, where at least one volunteer responder arrived before EMS (42% of alerted cases), were compared with OHCAs where EMS arrived first.¹³ An increased rate of bystander CPR [odds ratio (OR) 1.76] and bystander defibrillation (OR 3.73) was observed if a volunteer responder arrived before EMS. However, the study did not find a statistically significant increase in 30-day survival (16.1% survival vs. 13.1%, P = 0.38).

A systematic review of mobile phone systems to alert volunteer responders from 2020 including 28 studies from 12 different volunteer responder systems found a positive association between responder activation and increased bystander CPR and survival.¹⁰ However, all the included observational studies had very low certainty of evidence (downgraded for inconsistency and serious risk of bias).⁵ Accordingly, more high-certainty prospective studies and randomized clinical trials are warranted. Currently, only one randomized controlled trial (not powered for survival) has been published assessing the effect of activating volunteer responders in OHCA in addition to standard EMS response. This study found an increase in the proportion of patients receiving bystander CPR when volunteer responders were activated through a text-message system, but no significant increase in 30-day survival.¹⁴ However, the study (published in 2015) had no AED recruitment strategy included.

Randomized clinical trials provide the best framework to evaluate the effectiveness of a new treatment, compared with standard of care. This is also the case for evaluating the effectiveness of volunteer responder programs as an addition to standard EMS response. Several randomized controlled trials are being conducted (the Scandinavian AED and Mobile Bystander Activation Trial; NCT02992873, the HeartRunner Trial from Denmark; NCT03835403, and the PulsePoint Study from North America; NCT04806958) to assess this question. While awaiting these results, access to granular data from observational studies like the GoodSAM app is valuable to understand and improve volunteer responder programs. Ideally, studies should include information on all aspects from the logistic systems used, the activation process (radius and number of alerted responders), information on linkage to AEDs, the capture of OHCAs, acceptance rates, interventions performed by volunteer responders in regard to CPR, and AED use before EMS arrival as well as information on the psychological impact and physical harm among dispatched volunteer responders.

The results presented in the current study using the GoodSAM app add important knowledge to the novel field of volunteer responder activation. The study provides a framework to improve the existing system and found activation to be associated with patient survival. However, several important questions for optimizing volunteer first-responder programs remain: (i) What is the added effect of these systems for 30-day/long-term survival as well as neurological intact survival? (ii) What is the optimal activation radius for alerting volunteer responders, and should the radius be adjustable according to population/AED density? (iii) What is the optimal design for volunteer responder systems ensuring that they capture the majority of OHCAs and not just a few, selected cases? (iv) Should volunteer responders be alerted for both OHCAs in public and private homes? (v) What is the correlation between number of alerted responders and chance of bystander CPR, defibrillation, and survival? (vi) And how does the density of volunteer responders as well as AED density affect chance of early defibrillation and survival?

In conclusion, early intervention is the best weapon available for improving not only short-term but also long-term survival after OHCA.² Implementing and improving volunteer responder systems in addition to the standard EMS response holds the potential to be a real game-changer in increasing bystander CPR and early defibrillation, hopefully translating into improved OHCA survival. Smith et al. contribute with important and encouraging findings to further improve volunteer first-responder programs.

Conflict of interest: Fredrik Folke has received research grant from the NovoNordisk Foundation, TrygFonden, and Laerdal Foundation. Carolina Malta Hansen has received research grant from TrygFonden and Laerdal Foundation. Fredrik Folke and Carolina Malta Hansen are involved inresearch on the Danish volunteer first-responder program, the TrygFonden HeartRunner program.

The opinions expressed in this article are not necessarily those of the Editors of the European Heart Journal: Acute Cardiovascular Care or of the European Society of Cardiology.

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