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Canadian Journal of Cardiology

Responding to Cardiac Arrest in the Community in the Digital Age

  • Author Footnotes
    ‡ These authors are co-first authors.
    Katherine S. Allan
    Correspondence
    Corresponding author: Dr Katherine S. Allan, St. Michael’s Hospital, 193 Yonge St, Suite 3-007, Toronto, Ontario M5B 1M8, Canada. Tel.: +1-289-242-2112.
    Footnotes
    ‡ These authors are co-first authors.
    Affiliations
    Division of Cardiology, Unity Health Toronto - St Michael’s Hospital, Toronto, Ontario, Canada
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  • Author Footnotes
    ‡ These authors are co-first authors.
    Emma O’Neil
    Footnotes
    ‡ These authors are co-first authors.
    Affiliations
    Department of Emergency Medicine, Unity Health Toronto - St Michael’s Hospital, Toronto, Ontario, Canada
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  • Margaret M. Currie
    Affiliations
    Faculty of Science, Dalhousie University, Halifax, Nova Scotia, Canada
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  • Steve Lin
    Affiliations
    Department of Emergency Medicine, Unity Health Toronto - St Michael’s Hospital, Toronto, Ontario, Canada

    Keenan Research Centre, Li Ka Shing Knowledge Institute, St Michael’s Hospital, Toronto, Ontario Canada

    Department of Medicine, University of Toronto, Toronto, Ontario, Canada

    Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada
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  • John L. Sapp
    Affiliations
    Department of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada

    Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada
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  • Paul Dorian
    Affiliations
    Division of Cardiology, Unity Health Toronto - St Michael’s Hospital, Toronto, Ontario, Canada

    Keenan Research Centre, Li Ka Shing Knowledge Institute, St Michael’s Hospital, Toronto, Ontario Canada

    Department of Medicine, University of Toronto, Toronto, Ontario, Canada
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  • Author Footnotes
    ‡ These authors are co-first authors.
Published:December 21, 2021DOI:https://doi.org/10.1016/j.cjca.2021.12.005

      Abstract

      Sudden cardiac arrest (SCA) is a common event, affecting almost 400,000 individuals annually in North America. Initiation of cardiopulmonary resuscitation (CPR) and early defibrillation using an automated external defibrillator (AED) are critical for survival, yet many bystanders are reluctant to intervene. Digital technologies, including mobile devices, social media, and crowdsourcing might help play a role to improve survival from SCA. In this article we review the current digital tools and strategies available to increase rates of bystander recognition of SCA, prompt immediate activation of emergency medical services (EMS), initiate high-quality CPR, and to locate, retrieve, and operate AEDs. Smartphones can help to educate and connect bystanders with EMS dispatchers, through text messaging or video calling, to encourage the initiation of CPR and retrieval of the closest AED. Wearable devices and household smart speakers could play a future role in continuous vital signs monitoring in individuals at risk of lethal arrhythmias and send an alert to either chosen contacts or EMS. Machine learning algorithms and mathematical modelling might aid EMS dispatchers with better recognition of SCA as well as policymakers with where to best place AEDs for optimal accessibility. There are challenges with the use of digital tech, including the need for government regulation and issues with data ownership, accessibility, and interoperability. Future research will include smart cities, e-linkages, new technologies, and using social media for mass education. Together or in combination, these emerging digital technologies might represent the next leap forward in SCA survival.

      Résumé

      L'arrêt cardiaque soudain (ACS) est un événement courant, qui touche près de 400 000 personnes chaque année en Amérique du Nord. La mise en place de la réanimation cardiorespiratoire (RCR) et de la défibrillation précoce à l'aide d'un défibrillateur externe automatisé (DEA) sont essentielles à la survie, mais de nombreux passants hésitent à intervenir. Les technologies numériques, notamment les appareils mobiles, les médias sociaux et la création participative pourraient contribuer à améliorer la survie après un ACS. Dans cet article, nous passons en revue les outils numériques actuels et les stratégies disponibles pour augmenter les taux d'identification d'un ACS par les passants, l'activation immédiate des services médicaux d'urgence (SMU), le déclenchement d'une RCR de qualité et la localisation, la récupération et le fonctionnement des DEA. Les téléphones intelligents peuvent contribuer à éduquer les témoins d'un ACS et à les mettre en relation avec les répartiteurs des SMU, par le biais de messages texte ou d'appels vidéo, afin d'encourager le déclenchement de la RCR et la récupération du DEA le plus proche. Les dispositifs portables et les haut-parleurs domestiques intelligents pourraient à l'avenir jouer un rôle dans la surveillance continue des signes vitaux chez les personnes présentant un risque d'arythmies mortelles et envoyer une alerte à des contacts prédéfinis ou aux SMU. Les algorithmes d'apprentissage automatique et la modélisation mathématique pourraient aider les répartiteurs des SMU à mieux reconnaître les ACS et les décideurs à déterminer où placer les DEA pour une accessibilité optimale. L'utilisation des technologies numériques présente des défis, notamment la nécessité d'une réglementation gouvernementale et des questions de propriété, d'accessibilité et d'interopérabilité des données. Les futures recherches porteront sur les villes intelligentes, les liens électroniques, les nouvelles technologies et l'utilisation des médias sociaux pour l'éducation de masse. Ensemble ou en combinaison, ces technologies numériques émergentes pourraient représenter le prochain bond en avant quant à la survie à un ACS.
      There are an estimated 400,000 sudden cardiac arrests (SCAs) that occur annually outside the hospital across North America, and fewer than 10% of victims survive.
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      Improving temporal trends in survival and neurological outcomes after out-of-hospital cardiac arrest.
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      A critical component to increasing survival from SCA is rapid identification and initiation of treatment; the first link in the “chain of survival” for emergency cardiovascular care is immediate identification of SCA and early activation of emergency medical services (EMS; Fig. 1).
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      Part 3: adult basic and advanced life support: 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care.
      Figure thumbnail gr1
      Figure 1Adult out-of-hospital cardiac arrest (OHCA) chain of survival. CPR, cardiopulmonary resuscitation. Reprinted from Panchal et al.
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      with permission from the American Heart Association, Inc. ©2020 American Heart Association, Inc.
      However, in most communities, even in urban settings, average EMS response times range from 6 to 7 minutes,
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      thus intervention by bystanders is critical for SCA survival. With each passing minute, the probability of survival declines 7%-10%.
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      Predicting survival from out-of-hospital cardiac arrest: a graphic model.
      With rapid initiation of bystander cardiopulmonary resuscitation (CPR) and early defibrillation with an automated external defibrillator (AED), survival rates can reach as high as 70%.
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      Despite public educational initiatives and clinical practice guideline recommendations from major resuscitation organizations,
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      rates of bystander CPR have plateaued at 35%-40% across North America for more than a decade, and even fewer bystanders know what an AED is or where to find one.
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      One emerging area to improve the recognition of SCA and response by bystanders is the use of digital technologies, including mobile devices, social media, and crowdsourcing.
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      Digital technologies are an ideal solution for emergency care, because they can provide the general public with information that is accessible and context-specific, personalized, tailored to the local language and geography, and most importantly, “just in time.”
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      Mobile devices, social media, and smart wearable devices offer innovative ways of helping facilitate the recognition and earlier intervention for SCAs, witnessed and unwitnessed, by the general public.
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      Use of mobile devices, social media, and crowdsourcing as digital strategies to improve emergency cardiovascular care.

      Early Recognition and Activation of EMS

      Despite recent advances over 3 decades in our ability to treat cardiovascular disease, acute events, including SCA, remain a leading cause of morbidity and mortality.
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      Heart disease and stroke statistics-2021 update a report from the American Heart Association.
      An important strategy to increasing survival is to increase the recognition of SCA as well as rates of bystander CPR; the American Heart Association (AHA) described 4 key steps for bystanders to first recognize that an SCA event is occurring and then respond as part of a coordinated community emergency response (Fig. 2).
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      Increasing cardiopulmonary resuscitation provision in communities with low bystander cardiopulmonary resuscitation rates: a science advisory from the American Heart Association for healthcare providers, policymakers, public health departments, and community leaders.
      Figure thumbnail gr2
      Figure 2Four critical steps to the performance of cardiopulmonary resuscitation (CPR) by a bystander. AED, automated external defibrillator; SCA, sudden cardiac arrest. Source: Sasson et al.
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      American Heart Association, Inc.
      First the bystander needs to recognize that a person is having an SCA event or that the person needs medical assistance. The bystander must then call 9-1-1 (or equivalent) to notify EMS. This call is then sent to an EMS dispatcher, who must also recognize that the victim is having an SCA event, dispatch EMS and if needed, coach the bystander to provide CPR. With the more frequent placement of AEDs in communities since the release of these guidelines, there is an additional vital fifth step: the EMS dispatcher must tell the bystander to fetch the closest AED and use it before EMS arrival.
      Unfortunately, there are significant barriers associated with each of these steps: bystanders might not always recognize that a person is suffering from an SCA and thus delay activating EMS and bystanders might experience uncertainty about how to perform CPR, be fearful of disease transmission or legal repercussions and therefore not initiate CPR.
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      An exploration of attitudes toward bystander cardiopulmonary resuscitation in university students in Tianjin, China: a survey.
      When contacted, EMS dispatchers might not identify that the victim is having an SCA event and thus not encourage the bystander to start chest compressions or fetch an AED. Digital strategies might help mitigate some of these limitations; because of the transferable nature of social and mobile data, information can be instantly updated to help facilitate discussion, such as through text messaging or even visual exchange through video calling between bystanders and health care providers in real-time about identifying an SCA and quickly responding before EMS arrival.
      • Rumsfeld J.S.
      • Brooks S.C.
      • Aufderheide T.P.
      • et al.
      Use of mobile devices, social media, and crowdsourcing as digital strategies to improve emergency cardiovascular care.
      Smartphones and wearable devices can help to educate and connect bystanders with EMS dispatchers to encourage the initiation of high-quality CPR and retrieval of the closest AED. Machine learning (ML) algorithms and mathematical modelling might aid EMS dispatchers with better recognition of an SCA as well as policymakers with where to best place AEDs for optimal accessibility.

      Public awareness and education

      Social media provide a new means for raising awareness about SCA and educating the general public on a large scale. A good example of this is “World Restart a Heart Day” on October 16th each year. Started in 2018 by the European Resuscitation Council and the International Liaison Committee on Resuscitation, this event is a worldwide initiative to increase awareness of SCA and rates of bystander CPR through social media campaigns and mass CPR training events.
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      In 2018, the campaign successfully reached 12.7 million people via social media and 675,000 were trained on how to perform CPR.
      European Society of Anaesthesiology and Intensive Care. World Restart A Heart Day 2020.
      In 2019, 5.4 million people globally were trained in CPR and 206 million people were reached via social media using the #worldrestartaheart initiative.
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      Up to 206 million people reached and over 5.4 million trained in cardiopulmonary resuscitation worldwide: the 2019 international liaison committee on resuscitation World Restart A Heart initiative.
      In 2021, the focus is on survivors using the hashtag #CPRSavedMyLife and aims to create awareness that everyone can learn CPR and promote training courses in schools and public locations around the world (see https://www.ilcor.org/wrah for more details).

      Diagnosing SCA using wearable devices or smartphones

      More than 70% of SCAs occur at home and although family members might be close by, more than half are unwitnessed.
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      • Drennan I.R.
      • Scales D.C.
      • et al.
      Improving temporal trends in survival and neurological outcomes after out-of-hospital cardiac arrest.
      Furthermore, witnesses might not recognize sudden collapse as an immediate emergency. Digital technologies, such as wearable sensors or smart speakers, could detect such events earlier and automatically activate EMS and warn bystanders.
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      Automated cardiac arrest detection and alerting system using a smartphone and a standard bluetooth chest strap heart rate monitor during exercise: the “Parachute” app.
      ,
      • Chan J.
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      Contactless cardiac arrest detection using smart devices.
      Smart wearable devices are consumer-grade, electronic devices that can be worn on the body or embedded into clothing to measure multiple vital signs simultaneously and gather health insights about the wearer.
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      They generally have high processing power and send data wirelessly to a mobile device that displays vital sign trends to the user. Wrist and chest strap-based devices have been shown to be a reliable way of detecting cardiac arrest in users.
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      Automated cardiac arrest detection and alerting system using a smartphone and a standard bluetooth chest strap heart rate monitor during exercise: the “Parachute” app.
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      Utility of a novel watch-based pulse detection system to detect pulselessness in human subjects.
      Rickard and colleagues used an early version of a wearable wrist device (Wriskwatch, Emergency Medical Technologies) to detect pulselessness in a cohort of hospitalized patients and patients undergoing implantable cardioverter defibrillator (ICD) testing.
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      Utility of a novel watch-based pulse detection system to detect pulselessness in human subjects.
      The watch had a sensitivity of 99.9% to detect pulse status and a specificity of 90.3%. Wearable devices have evolved to be able to detect the presence of ventricular fibrillation (VF) and send out a corresponding alert to activate EMS, which could significantly shorten the rescue process.
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      Automated cardiac arrest detection and alerting system using a smartphone and a standard bluetooth chest strap heart rate monitor during exercise: the “Parachute” app.
      ,

      VCU tech. Massok M, Walters J, Artis J, et al. Wearable Cardiac Arrest Detection Device (WCADD) (US Patent No. 20180310847). 2018. Available at: https://patents.google.com/patent/US20180310847A1/en?oq=20180310847.

      Gaibazzi and Reverberi tested the reliability of a smartphone app combined with 2 types of Bluetooth-connected chest heart rate monitors in 10 athletes running and cycling to see if it could reliably detect simulated VF and send an automatic text alert to EMS and chosen contacts.
      • Gaibazzi N.
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      Automated cardiac arrest detection and alerting system using a smartphone and a standard bluetooth chest strap heart rate monitor during exercise: the “Parachute” app.
      Of 100 simulations, the app correctly detected simulated VF and appropriately sent an alert when the subject was lying still for at least 25 seconds and did not send any false alerts while the athletes were running or cycling. These devices could play a future role in continuous vital signs monitoring in individuals at risk of lethal arrhythmias and send an alert if they detect VF or loss of pulse to either chosen contacts or even EMS.
      Another promising approach to detecting unwitnessed arrests at home involves the use of smart speakers (Amazon Echo and Apple iPhone) to detect agonal breathing
      • Chan J.
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      ; agonal breathing is an audible event that arises from a brainstem reflex in the setting of severe hypoxia caused by SCA.
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      Chan et al. used a type of ML known as a support vector machine (SVM) to classify agonal breathing events from real-world labelled 9-1-1 audio of SCAs within a bedroom environment, and reported an overall sensitivity of 97.2% and specificity of 99.5%.
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      Contactless cardiac arrest detection using smart devices.
      When they further tested the SVM with sleep lab data that included snoring, hypopnea, obstructive and central sleep apnea events, which mimic agonal breathing sounds, they achieved a false positive event rate between 0 to 0.14%. When tested on the Echo and iPhone, the SVM had > 96.6% accuracy at distances up to 3 m. Although the sensitivity and specificity of the SVM for detecting agonal breathing in simulated situations is impressive, even a false positive rate of 0.14% could result in substantial costs to municipalities if EMS are dispatched for false events. More research is needed before this technology can be deployed in a real-world setting.
      A group in Korea recently tested a new method for detecting a loss of pulse using seismocardiography, which measures the vibrations produced by a beating heart using an accelerometer sensor placed on the chest.
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      • Jung Y.H.
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      Discrimination between the presence and absence of spontaneous circulation using smartphone seismocardiography: a preliminary investigation.
      A smartphone equipped with an accelerometer was placed on the sternum of 30 comatose adult patients and 30 deceased adult patients, to obtain seismocardiography signals, which were then viewed by 156 blinded observers for presence or absence of pulse. The observers were able to accurately distinguish the seismocardiography signals from patients without a pulse, with a sensitivity of 97.6% (95% confidence interval [CI], 97.0%-98.2%) and a specificity of 98.4% (95% CI, 97.8%-99.0%), thus showing the potential of this smartphone technology to aid in the recognition of SCA.

      Dispatcher recognition of SCA

      EMS dispatchers play an important role in improving SCA survival. In 2015 the AHA and European Resuscitation Council guidelines
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      emphasized how the role of dispatchers has expanded to include recognizing that a victim is suffering an SCA event, coaching bystanders to perform CPR, fetch and deploy public AEDs, and accurately guide EMS to the SCA victim. The best practice to recognize SCA over the phone is to ask the caller 2 questions: “Is the patient unconscious?” and “Is the patient breathing normally or abnormally?”
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      This evidence stems from 23 observational studies in > 17,000 patients and has been reported to have a sensitivity ranging from 38% to 97% and a specificity exceeding 97%.
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      Recent efforts to improve EMS dispatcher recognition of SCA over the phone have involved the use of ML. Multiple investigators have studied the effect of ML on EMS dispatcher recognition of SCA
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      and observed that ML was more sensitive (84.1% ML vs 72.5% EMS dispatchers; P < 0.001) and faster at recognizing SCA compared with EMS dispatchers without ML (median 44 seconds ML vs 54 seconds EMS dispatchers; P < 0.001).
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      Machine learning as a supportive tool to recognize cardiac arrest in emergency calls.
      Despite having higher sensitivity, the use of ML resulted in a lower positive predictive value compared with EMS dispatchers (20.9% ML vs 33.0% EMS dispatchers; P < 0.001), and lower specificity (97.3% ML vs 98.8% EMS dispatchers; P < 0.001).
      • Blomberg S.N.
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      Machine learning as a supportive tool to recognize cardiac arrest in emergency calls.

      Increasing the Rate of High-Quality CPR

      If a bystander performs CPR before EMS arrival, SCA victims are almost twice as likely to survive compared with those who do not receive it.
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      Globally, CPR rates range between 6% and 70%.
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      Bystander resuscitation: the impact of first aid on survival.
      ,
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      Since 2008, the AHA and International Liaison Committee on Resuscitation have shifted away from the traditional paradigm of conventional CPR training, emphasizing the increased use of hands-only CPR for bystanders
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      via self training or online videos, using community awareness programs through widespread social media campaigns,
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      and advocating for effective dispatcher-assisted CPR (DA-CPR).
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      Mobile technology has the ability to assist with all of these endeavours, acting as a source of “just-in-time” CPR awareness and education, connecting bystanders in real-time with EMS dispatchers, who can provide instructions on how to perform CPR and fetch the closest AED and even dispatch lay people to act as first responders until EMS arrives on scene.

      CPR education via smartphone applications, virtual reality, and wearable technology

      A new and growing market of smartphone applications have been shown to help bystanders perform and improve their CPR skills. Bystanders commonly hesitate to initiate CPR because of fear or lack of knowledge. The introduction of smartphone applications might help to alleviate these pressures, resulting in more laypeople willing to perform CPR.
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      A variety of applications are currently freely available for download, such as PulsePoint, Heart Hero, GoodSAM, PocketCPR, and Heart Runner. PocketCPR for example, walks a bystander through performing adult CPR with pictures and voice prompts and guides the individual to hold their smartphone in their hand so it can ensure they’re getting the proper depth during compressions. This application was shown to increase compression depth and achieve compression rates of > 100 beats per minute.
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      New era of CPR: application of i-technology in resuscitation.
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      Using a smartphone application (PocketCPR) to determine CPR quality in a bystander CPR scenario — a manikin trial.
      New technology such as a credit-card size “CPRcard” provides visual feedback of compression depth and rate in real time, resulting in better-quality compressions.
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      Quality of bystander CPR by lay first responders: training versus real-world use of a novel CPR feedback device in Singapore.
      Mobile phones might also be useful as a more accessible and cost-efficient refresher method for CPR training in lay responders.
      • Ahn J.Y.
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      Effect of a reminder video using a mobile phone on the retention of CPR and AED skills in lay responders.
      Repeated reminder videos sent to user’s smartphone via text in combination with regular training preserved participants willingness and confidence to perform CPR and provided support for the retention of CPR and AED skills.
      • Ahn J.Y.
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      • Park S.M.
      • Kang K.H.
      Effect of a reminder video using a mobile phone on the retention of CPR and AED skills in lay responders.
      Traditional CPR training courses occur in controlled environments, using simulated scenarios that do not mimic the high stress reality of real medical emergencies. Virtual reality wearable devices allow for the creation of high stress, highly realistic scenarios that could allow bystanders to respond to an SCA event.
      • Leary M.
      • Almodovar A.
      • Buckler D.G.
      • Bhardwaj A.
      • Blewer A.L.
      • Abella B.S.
      Using an immersive virtual reality system to assess lay provider response to an unannounced simulated sudden cardiac arrest in the out-of-hospital setting.
      Leary et al. tested 119 lay responders wearing a virtual reality wearable device in a 3-minute multisensory SCA scenario.
      • Leary M.
      • Almodovar A.
      • Buckler D.G.
      • Bhardwaj A.
      • Blewer A.L.
      • Abella B.S.
      Using an immersive virtual reality system to assess lay provider response to an unannounced simulated sudden cardiac arrest in the out-of-hospital setting.
      Most of the participants stated that they felt as if they were at a real SCA event, with 90% calling 9-1-1 and most attempting to perform CPR. However, only 13% requested an AED and even fewer (6%) used it.
      Smartwatches can be used in a similar fashion to a smartphone to guide a layperson to perform CPR and can be an effective method for achieving high-quality CPR.
      • Song Y.
      • Chee Y.
      • Oh J.
      • Ahn C.
      • Lim T.H.
      Smartwatches as chest compression feedback devices: a feasibility study.
      Choi et al. observed that smartwatches used as a CPR guidance system through their vibration function in a noisy setting can help participants achieve a mean compression rate more accurately than metronome-guided CPR.
      • Choi S.
      • Han S.
      • Chae M.K.
      • Lee Y.H.
      Effects of vibration-guided cardiopulmonary resuscitation with a smartwatch versus metronome guidance cardiopulmonary resuscitation during adult cardiac arrest: a randomized controlled simulation study.
      Another study showed that smartwatch chest compression feedback was actually more accurate than that provided by smartphones.
      • Song Y.
      • Chee Y.
      • Oh J.
      • Ahn C.
      • Lim T.H.
      Smartwatches as chest compression feedback devices: a feasibility study.
      Moreover, smartwatch users actually prefer receiving interactive real-time feedback on the frequency and depth of CPR; in one such study it was observed that more than 90% of participants felt positive that a live feedback system like the CPR Watch could help to save more lives, and 89% of all study participants stated that they felt much safer while performing CPR with the assistance of the watch than without it.
      • Gruenerbl A.
      • Pirkl G.
      • Monger E.
      • Gobbi M.
      • Lukowicz P.
      Smart-Watch life saver: Smart-Watch interactive-feedback system for improving bystander CPR.

      Geolocalization

      Global positioning system (GPS) is a radio navigation system that provides location to any software app that requests it, by triangulating radio wave signals from multiple satellites and sending it to a receiver inside a smartphone.
      • Rout A.
      • Nitoslawski S.
      • Ladle A.
      • Galpern P.
      Using smartphone-GPS data to understand pedestrian-scale behavior in urban settings: a review of themes and approaches.
      Location data can be sent to EMS dispatchers, which could lead to faster location of the SCA victim, for the earlier arrival of lay or professional rescue personnel.
      Ecker et al. tested the use of automatic geolocalization using a smartphone app compared with a conventional emergency call with oral description of the location, for simulated EMS calls reporting a person suffering SCA.
      • Ecker H.
      • Lindacher F.
      • Dressen J.
      • et al.
      Accuracy of automatic geolocalization of smartphone location during emergency calls — a pilot study.
      Of 108 simulated SCA calls, using the smartphone app to call EMS resulted in significantly faster geolocation of the SCA victim (37 ± 36.6 seconds faster; P < 0.001), faster dispatch of EMS (41.2 ± 38.2 seconds earlier; P < 0.001), and faster initiation of CPR (39.6 ± 38.8 seconds earlier; P < 0.001) compared with a conventional call. The authors also estimated the difference between the actual location of the SCA victim and the estimated position provided by the EMS dispatcher and the app. The smartphone app proved to be highly precise; the difference between the actual position and the estimated position was 65.5 ± 320.5 m when using the app vs 1173 ± 4343.1 m when provided by EMS dispatch in the conventional calls. Worldwide, the average accuracy of GPS has been observed to have a range of 2 ± 3 m, very close to the actual location of the person.
      • Weinlich M.
      • Kurz P.
      • Blau M.B.
      • Walcher F.
      • Piatek S.
      Significant acceleration of emergency response using smartphone geolocation data and a worldwide emergency call support system.
      A potential limitation is inaccurate GPS geolocation indoors in large buildings with multiple floors.

      Crowdsourcing bystanders and AEDs for CPR

      Rapid communications systems can optimize individuals and groups for specific services, such as crowdsourcing for bystanders to perform CPR and use an AED in a medical emergency.
      • Rumsfeld J.S.
      • Brooks S.C.
      • Aufderheide T.P.
      • et al.
      Use of mobile devices, social media, and crowdsourcing as digital strategies to improve emergency cardiovascular care.
      EMS services around the globe have implemented these types of emergency response programs that use smartphones to activate lay people to act as first responders. These programs use GPS mapping to direct previously registered volunteers to SCA and AED locations via a mobile phone, either by short messaging service (SMS) alerts or through an app, are relatively inexpensive to implement and can increase SCA survival without major increases in costs to the health care system
      • Vercammen S.
      • Moens E.
      Cost-effectiveness of a novel smartphone application to mobilize first responders after witnessed OHCA in Belgium.
      (see Supplemental Table S1 for further details about these apps).
      The Netherlands was one of the first countries to study the use of crowdsourcing laypersons via SMS when a suspected SCA was close by, demonstrating that the system was feasible to use.
      • Scholten A.C.
      • van Manen J.G.
      • van der Worp W.E.
      • IJzerman M.J.
      • Doggen C.J.M.
      Early cardiopulmonary resuscitation and use of automated external defibrillators by laypersons in out-of-hospital cardiac arrest using an SMS alert service.
      Two popular programs that involve a mobile app and integrate trained lay responders with local EMS dispatch systems are PulsePoint (https://www.pulsepoint.org) and GoodSam (https://www.goodsamapp.org).
      • Brooks S.C.
      • Simmons G.
      • Worthington H.
      • Bobrow B.J.
      • Morrison L.J.
      The PulsePoint Respond mobile device application to crowdsource basic life support for patients with out-of-hospital cardiac arrest: challenges for optimal implementation.
      ,
      • Smith C.M.
      • Wilson M.H.
      • Hartley-Sharpe C.
      • Gwinnutt C.
      • Dicker B.
      • Perkins G.D.
      The use of trained volunteers in the response to out-of-hospital cardiac arrest – the GoodSAM experience.
      When EMS dispatch identifies an SCA occurring in a public location, an alert is sent out to all app users within a nearby radius. Potential responders receive an alert on their phone followed by a map displaying the location of the SCA and nearby AEDs. GoodSAM also has integrated live video transmission from the scene to be sent to the EMS dispatch centre, allowing dispatchers to provide real-time CPR instructions and feedback to lay responders.
      • Smith C.M.
      • Wilson M.H.
      • Hartley-Sharpe C.
      • Gwinnutt C.
      • Dicker B.
      • Perkins G.D.
      The use of trained volunteers in the response to out-of-hospital cardiac arrest – the GoodSAM experience.
      As of September 2021, PulsePoint is being used in 4140 communities across North America (753,764 monthly users), it has 115,889 AEDs registered and has dispatched lay responders to 1,167,937 SCA incidents to date.
      PulsePoint. By the numbers - STATS.
      GoodSAM is currently being used in the United Kingdom, Australia, New Zealand, India, United States, Brazil, South Africa, and in parts of Europe.
      • Smith C.M.
      • Wilson M.H.
      • Hartley-Sharpe C.
      • Gwinnutt C.
      • Dicker B.
      • Perkins G.D.
      The use of trained volunteers in the response to out-of-hospital cardiac arrest – the GoodSAM experience.
      There is growing evidence of the clinical effect of these app-based programs on SCA outcomes. The best evidence comes from Denmark and the HeartRunner mobile app. Through a series of prospective observational studies
      • Andelius L.
      • Hansen C.
      • Lippert F.
      • et al.
      Dispatching lay rescuers through a smartphone application is associated with increased bystander defibrillation in out of hospital cardiac arrest.
      • Andelius L.
      • Hansen C.
      • Lippert F.
      • et al.
      68 Risks and benefits using a mobile-phone positioning system to activate lay volunteers to out-of-hospital cardiac arrests.
      • Andelius L.
      • Malta Hansen C.
      • Lippert F.K.
      • et al.
      Smartphone activation of citizen responders to facilitate defibrillation in out-of-hospital cardiac arrest.
      the Danish group have shown that trained citizen responders can arrive before EMS in at least 40% of cases and that when they do, the odds for bystander CPR increased (odds ratio [OR], 1.76; 95% CI, 1.07-2.91; P = 0.027) and the odds for bystander defibrillation using an AED more than tripled (OR, 3.73; 95% CI, 2.04-6.84; P < 0.001) compared with citizens who arrived after EMS arrival.
      • Andelius L.
      • Malta Hansen C.
      • Lippert F.K.
      • et al.
      Smartphone activation of citizen responders to facilitate defibrillation in out-of-hospital cardiac arrest.
      These mobile apps can assist and shorten the time to AED retrieval by highlighting the location of nearby AEDs on a map and displaying the route distance and time estimates to the nearest AED and to the SCA patient.
      • Smith C.M.
      • Griffiths F.
      • Fothergill R.T.
      • Vlaev I.
      • Perkins G.D.
      Identifying and overcoming barriers to automated external defibrillator use by GoodSAM volunteer first responders in out-of-hospital cardiac arrest using the Theoretical Domains Framework and Behaviour Change Wheel: a qualitative study.
      Using these systems can also reduce the time to first shock and improve survival outcomes; lay responders dispatched using an SMS alert system in The Netherlands to the location of the closest AED defibrillated SCA victims on average 2:39 minutes earlier compared with EMS.
      • Zijlstra J.A.
      • Stieglis R.
      • Riedijk F.
      • Smeekes M.
      • van der Worp W.E.
      • Koster R.W.
      Local lay rescuers with AEDs, alerted by text messages, contribute to early defibrillation in a Dutch out-of-hospital cardiac arrest dispatch system.
      In Germany, Stroop et al. observed significant improvements in survival to hospital discharge between SCA victims who were initially resuscitated by lay responders alerted using an app-based system compared with those in whom resuscitation was initiated by EMS alone (18% vs 7%).
      • Stroop R.
      • Hensel M.
      • Strickmann B.
      • Kerner T.
      Mobile-phone based alerting of CPR-trained volunteers simultaneously with ambulance can reduce resuscitation-free interval and improve outcome after out-of-hospital cardiac arrest - a prospective observational study.
      This type of technology might have a major role in improving the “chain of survival” for SCA victims across the world.
      • Valeriano A.
      • van Heer S.
      • de Champlain F.
      • C Brooks S.
      Crowdsourcing to save lives: a scoping review of bystander alert technologies for out-of-hospital cardiac arrest.
      ,
      • McBride R.
      • Ski C.F.
      • Thompson D.R.
      • Quinn T.
      • Wilson M.H.
      Championing survival: connecting the unknown network of responders to address out-of-hospital cardiac arrest.

      DA-CPR

      Bystanders often delay the start of CPR because they are unsure if a person is suffering an SCA event or because they are not confident to perform CPR. EMS dispatchers can help bystanders to identify that someone is having an SCA, provide CPR instructions, and help them locate public-access AEDs.
      • Ng Y.Y.
      • Leong S.H.B.
      • Ong M.E.H.
      The role of dispatch in resuscitation.
      Instructions are provided via telephone CPR, which includes a group of standardized questions and instructions designed to provide immediate, life-saving interventions before EMS arrival.
      • Rybasack-Smith H.
      • Lauro J.
      A history and overview of telecommunicator cardiopulmonary resuscitation (T-CPR).
      A recent systematic review involving 33 observational studies from around the world showed that DA-CPR was associated with increased odds of survival with good neurological outcome at 1 month (OR, 1.47; 95% CI, 1.03-2.09), however this was on the basis of very low-quality evidence.
      • Nikolaou N.
      • Dainty K.N.
      • Couper K.
      • et al.
      A systematic review and meta-analysis of the effect of dispatcher-assisted CPR on outcomes from sudden cardiac arrest in adults and children.
      To overcome some of the barriers associated with DA-CPR, recent efforts have focused on video-assisted CPR (v-CPR), whereby EMS dispatchers videoconference with bystanders, providing real-time feedback on CPR rate and depth. In simulation studies, participants in the v-CPR groups were more likely to achieve the correct rate and to maintain the correct hand position but there were no significant differences between groups with regard to correct depth.
      • Lin Y.Y.
      • Chiang W.C.
      • Hsieh M.J.
      • Sun J.T.
      • Chang Y.C.
      • Ma M.H.M.
      Quality of audio-assisted versus video-assisted dispatcher-instructed bystander cardiopulmonary resuscitation: a systematic review and meta-analysis.
      V-CPR can also lead to increased self-confidence and a more positive attitude toward performing CPR.
      • Bolle S.R.
      • Johnsen E.
      • Gilbert M.
      Video calls for dispatcher-assisted cardiopulmonary resuscitation can improve the confidence of lay rescuers - surveys after simulated cardiac arrest.
      Preliminary evidence from limited real-life studies indicates that v-CPR is feasible and can improve bystander CPR performance as well as SCA outcomes.
      • Lee H.S.
      • You K.
      • Jeon J.P.
      • Kim C.
      • Kim S.
      The effect of video-instructed versus audio-instructed dispatcher-assisted cardiopulmonary resuscitation on patient outcomes following out of hospital cardiac arrest in Seoul.
      ,
      • Linderoth G.
      • Rosenkrantz O.
      • Lippert F.
      • et al.
      Live video from bystanders’ smartphones to improve cardiopulmonary resuscitation.
      Using the GoodSAM app, EMS dispatchers in Denmark added live video to audio communications with bystanders using a link sent by SMS.
      • Linderoth G.
      • Rosenkrantz O.
      • Lippert F.
      • et al.
      Live video from bystanders’ smartphones to improve cardiopulmonary resuscitation.
      Using the video recordings from 52 SCA calls, they evaluated the CPR performance of 90 bystanders and showed increased odds of improved CPR after v-CPR, including hand position (OR, 5.8; 95% CI, 2.8-12.1), compression rate (OR, 7.7; 95% CI, 3.4-17.3), and compression depth (OR, 7.1; 95% CI, 3.9-12.9).
      • Linderoth G.
      • Rosenkrantz O.
      • Lippert F.
      • et al.
      Live video from bystanders’ smartphones to improve cardiopulmonary resuscitation.
      In a retrospective study conducted with real SCA cases in Seoul, Korea, more favourable neurologic outcomes were observed in patients who received v-CPR vs those who received DA-CPR (19.4% v-CPR vs 6.8% DA-CPR).
      • Lee H.S.
      • You K.
      • Jeon J.P.
      • Kim C.
      • Kim S.
      The effect of video-instructed versus audio-instructed dispatcher-assisted cardiopulmonary resuscitation on patient outcomes following out of hospital cardiac arrest in Seoul.
      The additional use of video also allowed EMS dispatchers to visually check for bystander fatigue and then scan the surrounding area to actively point out people who could assist with CPR.

      Defibrillation and AED Use

      Early CPR and defibrillation are 2 of the most important factors for improved survival from SCA.
      • Panchal A.R.
      • Bartos J.A.
      • Cabañas J.G.
      • et al.
      Part 3: adult basic and advanced life support: 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care.
      Although publicly accessible AEDs are frequently deployed in numerous countries and settings worldwide, including sports and community facilities,
      • McKinney J.
      • Johri A.M.
      • Poirier P.
      • et al.
      Canadian Cardiovascular Society cardiovascular screening of competitive athletes: the utility of the screening electrocardiogram to predict sudden cardiac death.
      bystander defibrillation in North America occurs only 2% of the time.
      • Virani S.S.
      • Alonso A.
      • Aparicio H.J.
      • et al.
      Heart disease and stroke statistics-2021 update a report from the American Heart Association.
      Mobile technology and mathematical modelling have led to several avenues to raise awareness and usage of publicly accessible AEDs by bystanders: (1) crowdsourcing to improve AED awareness and location specificity
      • Merchant R.M.
      • Asch D.A.
      • Hershey J.C.
      • et al.
      A crowdsourcing innovation challenge to locate and map automated external defibrillators.
      ,
      • Worme M.
      • Grant K.
      • Allan K.
      • Snobelen P.
      • Korley-Myron J.
      • Dorian P.
      Greater Toronto area heart map challenge: the first crowd-sourced automated external defibrillator registry in Canada.
      ; (2) using mathematical modelling to optimize the location of publicly accessible AEDs
      • Siddiq A.A.
      • Brooks S.C.
      • Chan T.C.Y.
      Modeling the impact of public access defibrillator range on public location cardiac arrest coverage.
      ,
      • Sun C.L.F.
      • Brooks S.C.
      • Morrison L.J.
      • Chan T.C.Y.
      Ranking businesses and municipal locations by spatiotemporal cardiac arrest risk to guide public defibrillator placement.
      ; and (3) drone delivery of AEDs to the scene of an SCA to reduce the time to defibrillation before EMS arrival.
      • Derkenne C.
      • Jost D.
      • Miron De L’Espinay A.
      • et al.
      Automatic external defibrillator provided by unmanned aerial vehicle (drone) in Greater Paris: a real world-based simulation.
      • Claesson A.
      • Bäckman A.
      • Ringh R.N.M.
      • et al.
      Time to delivery of an automated external defibrillator using a drone for simulated out-of-hospital cardiac arrests vs emergency medical services.
      • Sanfridsson J.
      • Sparrevik J.
      • Hollenberg J.
      • et al.
      Drone delivery of an automated external defibrillator - a mixed method simulation study of bystander experience.
      • Cheskes S.
      • McLeod S.L.
      • Nolan M.
      • et al.
      Improving access to automated external defibrillators in rural and remote settings: a drone delivery feasibility study.
      • Bogle B.M.
      • Rosamond W.D.
      • Snyder K.T.
      • Zègre-Hemsey J.K.
      The case for drone-assisted emergency response to cardiac arrest.

      Crowdsourcing AEDs

      The MyHeartMap Challenge was a crowdsourcing contest that ran in Philadelphia in 2012 and focused on improving AED awareness and location specificity using social media and gaming to engage the public to locate and report AEDs.
      • Rumsfeld J.S.
      • Brooks S.C.
      • Aufderheide T.P.
      • et al.
      Use of mobile devices, social media, and crowdsourcing as digital strategies to improve emergency cardiovascular care.
      During the 8-week study, 313 teams and individuals collectively identified > 1400 AEDs, 60% of which were unique, nonoverlapping entries and 44% of which were previously unknown to the study team or device manufacturers.
      • Merchant R.M.
      • Asch D.A.
      • Hershey J.C.
      • et al.
      A crowdsourcing innovation challenge to locate and map automated external defibrillators.
      Since then, numerous challenges have taken place in other US cities, including the first-ever Canadian AED crowdsourced scavenger hunt, the Greater Toronto Area Heart Map Challenge, which ran in March 2020.
      • Worme M.
      • Grant K.
      • Allan K.
      • Snobelen P.
      • Korley-Myron J.
      • Dorian P.
      Greater Toronto area heart map challenge: the first crowd-sourced automated external defibrillator registry in Canada.
      Despite being suspended after 2 weeks because of the COVID-19 pandemic, 302 participants registered (71 individuals and 231 as teams) and they identified a total of 1301 AEDs, of which 92% had complete information.
      • Worme M.
      • Grant K.
      • Allan K.
      • Snobelen P.
      • Korley-Myron J.
      • Dorian P.
      Greater Toronto area heart map challenge: the first crowd-sourced automated external defibrillator registry in Canada.
      Of the AEDs registered, 98% were new additions and previously unknown to the organizers. These studies suggest that crowdsourcing as a means of public engagement is a very effective means of locating and registering publicly accessible AEDs as well as raising awareness about AEDs.

      Mathematical modelling to optimize publicly accessible AED locations

      Using geospatial methods to identify clusters of SCA hotspots and then prioritize public locations for AED placement is an important area of research to help inform EMS and policymakers about where to target resources. Chan and colleagues have published extensively on how to optimize the placement of publicly accessible AEDs to maximize coverage within SCA hotspots, by using geospatial mapping and mathematical modelling techniques.
      • Siddiq A.A.
      • Brooks S.C.
      • Chan T.C.Y.
      Modeling the impact of public access defibrillator range on public location cardiac arrest coverage.
      ,
      • Sun C.L.F.
      • Brooks S.C.
      • Morrison L.J.
      • Chan T.C.Y.
      Ranking businesses and municipal locations by spatiotemporal cardiac arrest risk to guide public defibrillator placement.
      In their 2017 study, Sun et al. mapped all SCAs occurring within 100 m of businesses and municipal locations in the city of Toronto, Canada, and then ranked them according to their spatiotemporal SCA risk.
      • Sun C.L.F.
      • Brooks S.C.
      • Morrison L.J.
      • Chan T.C.Y.
      Ranking businesses and municipal locations by spatiotemporal cardiac arrest risk to guide public defibrillator placement.
      Major coffee shop franchises (Tim Horton’s and Starbucks’s) and ATMs from the 5 largest Canadian banks took up 8 of the top 10 spots across the city and in the downtown core. This technique of optimizing AED locations in relation to SCA hotspots will not only increase the number of AED locations but also lead to increased awareness and ultimately help improve SCA survival.

      Drone delivery of AEDs

      Drone technology has emerged as a novel way to assist with rapid defibrillation for SCA events before the arrival of EMS.
      • Derkenne C.
      • Jost D.
      • Miron De L’Espinay A.
      • et al.
      Automatic external defibrillator provided by unmanned aerial vehicle (drone) in Greater Paris: a real world-based simulation.
      • Claesson A.
      • Bäckman A.
      • Ringh R.N.M.
      • et al.
      Time to delivery of an automated external defibrillator using a drone for simulated out-of-hospital cardiac arrests vs emergency medical services.
      • Sanfridsson J.
      • Sparrevik J.
      • Hollenberg J.
      • et al.
      Drone delivery of an automated external defibrillator - a mixed method simulation study of bystander experience.
      • Cheskes S.
      • McLeod S.L.
      • Nolan M.
      • et al.
      Improving access to automated external defibrillators in rural and remote settings: a drone delivery feasibility study.
      • Bogle B.M.
      • Rosamond W.D.
      • Snyder K.T.
      • Zègre-Hemsey J.K.
      The case for drone-assisted emergency response to cardiac arrest.
      • Wankmüller C.
      • Truden C.
      • Korzen C.
      • Hungerländer P.
      • Kolesnik E.
      • Reiner G.
      Optimal allocation of defibrillator drones in mountainous regions.
      In recent years, there have been efforts to design and implement a system of autonomous, AED-equipped drones.
      • Bogle B.M.
      • Rosamond W.D.
      • Snyder K.T.
      • Zègre-Hemsey J.K.
      The case for drone-assisted emergency response to cardiac arrest.
      These drones could be controlled by a central hub, with the ability to dispatch a drone to the location of an SCA at the touch of a button. Drone technology might significantly reduce the time to defibrillation, while also overcoming physical barriers to EMS intervention; a relatively inaccessible location to EMS, such as one with dangerous terrain, is easily accessible to a drone.
      • Cheskes S.
      • McLeod S.L.
      • Nolan M.
      • et al.
      Improving access to automated external defibrillators in rural and remote settings: a drone delivery feasibility study.
      ,
      • Wankmüller C.
      • Truden C.
      • Korzen C.
      • Hungerländer P.
      • Kolesnik E.
      • Reiner G.
      Optimal allocation of defibrillator drones in mountainous regions.
      SCA victims in rural areas might particularly benefit from drone delivery of AEDs, because survival can be severely decreased because of prolonged EMS response times. Cheskes et al. conducted 6 simulations in 2 rural communities in southern Ontario, Canada, and demonstrated that regardless of whether the drone was dispatched from the same or differing location from EMS, in each case it arrived on the scene more quickly, between 1.8 to 8.0 minutes faster.
      • Cheskes S.
      • McLeod S.L.
      • Nolan M.
      • et al.
      Improving access to automated external defibrillators in rural and remote settings: a drone delivery feasibility study.
      In contrast, a computer simulation study using SCA data from the Paris Fire Brigade & Sudden Death Expertise Centre Registry showed that when using a high-density urban model, only 26% of SCA patients would receive an AED from an AED drone before EMS arrival.
      • Derkenne C.
      • Jost D.
      • Miron De L’Espinay A.
      • et al.
      Automatic external defibrillator provided by unmanned aerial vehicle (drone) in Greater Paris: a real world-based simulation.
      This suggests that drones might be more effective in rural areas, where distance might be a more important barrier, and where there are fewer obstacles to circumvent. In an explorative simulation study Sanfridsson et al. observed that bystanders found AED retrieval after drone delivery safe and feasible and less difficult to interact with than performing CPR or handling their mobile phone during DA-CPR.
      • Sanfridsson J.
      • Sparrevik J.
      • Hollenberg J.
      • et al.
      Drone delivery of an automated external defibrillator - a mixed method simulation study of bystander experience.
      Together these findings suggest a potential role for drone-delivered AEDs to improve bystander AED use and thus outcomes for SCA victims.

      Challenges and opportunities

      Although the opportunities with digital technology to increase rates of bystander awareness and response to recognition of SCA events are undoubtedly growing, they are not without challenges.

      Mobile apps: misinformation and regulation

      Some mobile apps are designed to guide bystanders, whereas others are aimed toward health care providers, however, access is generally open and thus far not regulated. With such open access to the design and broad distribution of apps for health care, the risk for misinformation is significant.
      • Rumsfeld J.S.
      • Brooks S.C.
      • Aufderheide T.P.
      • et al.
      Use of mobile devices, social media, and crowdsourcing as digital strategies to improve emergency cardiovascular care.
      In a systematic review to assess the medical correctness and user friendliness of available apps for CPR, more than 50% of the examined apps did not consider agonal breathing important and did not state that patients who present with agonal breathing needed CPR.
      • Metelmann B.
      • Metelmann C.
      • Schuffert L.
      • Hahnenkamp K.
      • Brinkrolf P.
      Medical correctness and user friendliness of available apps for cardiopulmonary resuscitation: systematic search combined with guideline adherence and usability evaluation.
      Of the 34 apps studied, 18 (53%) recommended the wrong compression depth or had no information on depth and 8 (24%) apps did not show the correct compression rate of 100-120 beats per minute. Only 5 of 34 apps (15%) fulfilled all criteria chosen to determine guideline adherence; all other apps provided incorrect or no information on at least 1 relevant topic.
      Potential inaccessibility of public AEDs was highlighted by Leung et al., who reported that of 5848 AEDs from 4 provincial and 2 municipal online Canadian AED registries, an estimated 69.9% were completely inaccessible because of government closures due to the ongoing COVID-19 pandemic.
      • Leung K.H.B.
      • Alam R.
      • Brooks S.C.
      • Chan T.C.Y.
      Public defibrillator accessibility and mobility trends during the COVID-19 pandemic in Canada.
      A further 18.8% were partially inaccessible and only 11.3% were unaffected. Apps might not consider obstacles that exist between SCA victims and potential responders. A study on the landscape features on the capabilities of the PulsePoint app in Pennsylvania noted that most alert areas analyzed contained significant portions of unwalkable (inaccessible or uncrossable by foot) areas.
      • Smida T.
      • Willson C.
      • Salerno J.
      • Weiss L.
      • Salcido D.D.
      Can you get there from here? An analysis of walkability among PulsePoint CPR alert dispatches.
      This has direct implications on response times, because it might take lay responders longer to reach SCA victims or retrieve AEDs.
      Currently the US Food and Drug Administration does not plan to regulate all mobile apps, only those deemed the highest risk.
      • McCarthy M.
      FDA will not regulate most mobile medical apps.
      In 2015, the US Food and Drug Administration released guidelines on its approach to regulating mobile medical apps
      US Food and Drug Administration
      Guidance Document. Policy for Device Software Functions and Mobile Medical Applications. Guidance for Industry and Food and Drug Administration Staff.
      ; these guidelines prioritize the approval process of mobile apps that directly control medical devices or function as independent devices.
      • Rodriguez-Villa E.
      • Torous J.
      Regulating digital health technologies with transparency: the case for dynamic and multi-stakeholder evaluation.
      However, mobile apps that promote “wellness” or are educational are considered less harmful, and pose a smaller risk to public safety and health thus requiring less or no oversight.
      • Rodriguez-Villa E.
      • Torous J.
      Regulating digital health technologies with transparency: the case for dynamic and multi-stakeholder evaluation.
      For these mobile apps to be beneficial to lay responders and SCA victims, federal regulators might need to implement some sort of quality control to ensure that they provide medically accurate content.

      Privacy and access to data

      Many of the mobile apps used for CPR education or those linked with EMS dispatch centres that alert lay responders to nearby SCAs are third-party owned. A third-party app storing patient data or accessing the camera and microphone of a bystander’s mobile device can pose a severe privacy violation.
      • Ecker H.
      • Lindacher F.
      • Adams N.
      • et al.
      Video-assisted cardiopulmonary resuscitation via smartphone improves quality of resuscitation: a randomised controlled simulation trial.
      This is of particular concern with wearable devices that gather patient’s health information through various sensors worn on the body and then transfer this personal health information to end user applications or cloud infrastructure. Having secure modes of data transmission to safeguard the privacy of sensitive personal health information is essential.
      Third-party owned mobile apps highlight questions about data ownership, access, and interoperability with hospital electronic medical record (EMR) systems. When a publicly accessible AED is used, it is essential that a copy of the electrocardiogram is downloaded from the device and sent to the SCA victim’s health care provider to help with diagnosis and treatment. Because most hospitals lack the necessary software platforms to pull the data from different AED devices, without assistance from third party AED manufacturers, this step is currently insurmountable, which could lead to delays in treatment. Even when the files are downloaded by AED manufacturers, because they use a range of communication methods that are distinct, proprietary, and closed, these differences make it difficult for various AED software platforms and hospital EMR systems to communicate and transfer data streams, leading to a lack of system interoperability.
      • Clarke M.
      • de Folter J.
      • Verma V.
      • Gokalp H.
      Interoperable end-to-end remote patient monitoring platform based on IEEE 11073 PHD and ZigBee Health Care Profile.
      In general, the report ends up as a flat file and has to be scanned before it can be attached to the patient’s medical record and there is no direct integration of these data into the EMR. Similarly, the electronic paramedic care report filled out by EMS, which is also vital for the clinical care of the SCA patient, is not interoperative with hospital EMRs and has to be faxed, then scanned and uploaded as a flat file. Governments will need to be engaged to change public policies to help link digital technologies and address privacy concerns around third party data sharing with private companies. Policies should be developed that incentivize hospitals, third party developers, and other stakeholders to achieve smooth interoperability without compromising patient privacy or data accessibility.
      • Bayoumy K.
      • Gaber M.
      • Elshafeey A.
      • et al.
      Smart wearable devices in cardiovascular care: where we are and how to move forward.

      Future directions

      Because of their wide availability and advanced technological capabilities, digital tools have tremendous potential to improve the awareness and timely intervention for SCA victims (Fig. 3) as well as the overall linkage of the chain of survival. One of the areas in which these technologies can have the greatest effect is in the home, where > 70% of all SCAs occur and in many cases are unwitnessed.
      • Buick J.E.
      • Drennan I.R.
      • Scales D.C.
      • et al.
      Improving temporal trends in survival and neurological outcomes after out-of-hospital cardiac arrest.
      Figure thumbnail gr3
      Figure 3Improving outcomes with sudden cardiac arrest (SCA). CPR, cardiopulmonary resuscitation; EMS, emergency medical services. Reprinted from Rajagopalan et al.
      • Rajagopalan B.
      • Shen W.K.
      • Patton K.
      • et al.
      Surviving sudden cardiac arrest-successes, challenges, and opportunities.
      with permission from Springer Nature.
      In an ideal scenario, wearable devices or smart speakers aided by ML will accurately recognize SCA events as they occur, and send an alert to local EMS, the victim’s emergency contacts, and nearby lay responders via their mobile phone. Bystanders will be directed to the nearest AED, or EMS dispatch will in turn send an AED to the scene using a drone and will provide CPR and AED instructions to bystanders using video conferencing capabilities. In a more futuristic scenario, wearable devices, EMS, lay responders, AEDs, drones, and hospitals will all be interconnected through a “smart city” network; as an SCA event occurs, wearable devices or home monitoring technology will send automatic alerts simultaneously to other occupants in the house, EMS, nearby lay responders, and drones. At the hospital, e-linkages (Fig. 3) between data from wearable devices, smartphone apps, EMS, and AEDs will aid clinicians’ understanding of the SCA event, and how best to treat the patient, leading to overall improvements in the chain of survival. Furthermore, data gathered prehospital, from wearable devices, smartphone apps, and AEDs might help with prognostication and could improve our ability to identify patients who are unlikely to survive or have a poor neurological prognosis.
      Some of this technology is close; the current version of the Apple Watch (series 4 or later) can already perform some of these tasks; if it detects a hard fall when worn, it taps you on the wrist, sounds an alarm, and displays an alert, which gives you the choice to call EMS or ignore.
      • Apple
      Use fall detection with Apple Watch.
      The watch can also detect high, low, or irregular heartbeats and provide notifications when these occur,
      • Perez M.
      • Mahaffey K.W.
      • Hedlin H.
      • et al.
      Large-scale assessment of a smartwatch to identify atrial fibrillation.
      although it is not able to detect SCA as of yet.
      Currently there are multiple clinical trials ongoing testing the effectiveness of these various technologies including 4 on crowdsourcing bystanders (The HeartRunner Trial [NCT03835403], The PulsePoint Study [NCT04806958], Cardiac Arrest in Residential Areas With Mobile First-Responder Activation [CARAMBA; NCT04446585], Multifaceted Intervention for Increasing Performance of CPR by Laypersons in Out-of-hospital Cardiac Arrest (DISPATCH; NCT03633370),
      ClinicalTrials.gov
      Cardiac Arrest in Residential Areas With Mobile First-responder Activation (CARAMBA).
      ClinicalTrials.gov
      Multifaceted Intervention for Increasing Performance of CPR by Laypersons in Out-of-hospital Cardiac Arrest (DISPATCH).
      1 on medical dispatcher recognition of SCA (Out of Hospital Cardiac Arrest: Trial Assessing the Survival Impact of Phone Advice [CONTAC; NCT02934867]),
      ClinicalTrials.gov
      Out of Hospital Cardiac Arrest: Trial Assessing the Survival Impact of Phone Advice (CONTAC).
      and 1 on drone delivery of AEDs (AED-Delivery Using Drones in Suspected OHCA; NCT04723368).
      ClinicalTrials.gov
      AED-Delivery Using Drones in Suspected OHCA.
      Other technologies that have been designed but not yet approved could be “smart AEDs,”
      Resuscitation Academy
      Part 5: Out of Hospital Cardiac Arrest: The Future: The Possible.
      pocket-sized AEDs,
      Rapid Response Revival. Early Defibrillation Saves Lives.
      or even using your smartphone as an AED.
      AltrixMedical. Smartphone
      Automatic External Defibrillator.
      Conceptually, when attached to the SCA patient, a “smart AED” combined with biometric data gathered by wearable sensors (blood oxygen saturation, blood pH, blood glucose, heart rate, electrocardiogram, etc) could guide resuscitation therapy and recommend the best sequence of medication and defibrillation shocks.
      Resuscitation Academy
      Part 5: Out of Hospital Cardiac Arrest: The Future: The Possible.
      An Australian medical device start-up company (Rapid Response Revival) has created a portable AED—CellAED—that is small and light enough to carry in a purse or backpack and simple to use: snap, peel and stick.
      Rapid Response Revival. Early Defibrillation Saves Lives.
      Their vision is that every house or business will someday have this AED; they estimate the cost will be one-tenth of current AED prices (approximately $100-$200 USD). As of June 2021, they have received European regulatory approval for the device and are currently seeking approval from other markets.
      Rapid Response Revival. Early Defibrillation Saves Lives.
      Several companies are developing technology to use smartphones as AEDs; Altrix Medical is one such example, that is creating a pocket-sized AED that fits over a smartphone, the same way a traditional case does, however, the case will act as a fully functioning AED capable of telecommunications and videoconferencing when connected to the smartphone.
      AltrixMedical. Smartphone
      Automatic External Defibrillator.
      Access to technology by itself is not enough; users must know how to use them in emergency situations. The other area that can provide tremendous gains for SCA awareness and increasing rates of bystander CPR is using social media to educate the mass public. As of July 2021, there are 4.48 billion social media users around the world, almost 57% of the total global population, and the average user spends approximately 2.5 hours daily using it. The sharing or posting of photos and videos to social media and Web sites, where they can be viewed and shared again is highly popular, and can prove very effective at engaging and educating viewers; public service announcements released by the AHA in 2015 that aimed to increase awareness of SCA and bystander CPR have been viewed > 520 million times.
      • Rumsfeld J.S.
      • Brooks S.C.
      • Aufderheide T.P.
      • et al.
      Use of mobile devices, social media, and crowdsourcing as digital strategies to improve emergency cardiovascular care.
      Views however, do not inform whether or not the viewer learned from the video or ideally, led to improvements in SCA patient care. To achieve the full potential of this technology and others described, more research is needed on whether they have a direct effect on improvements in the recognition and treatment of SCA, including patient outcomes. This will help to inform government and EMS providers how to best direct resources to improve the care and outcomes of SCA patients.

      Conclusions

      Digital technologies hold great promise to improve the recognition of SCA and the response by bystanders in the community. Mobile devices, social media, and smart wearables provide new and effective means for raising awareness about SCA and educating the general public on a large scale. Text or app-based systems integrated with local EMS can crowdsource for bystanders to perform CPR and fetch the closest AED and are often associated with significant gains in SCA survival. However, successful deployment of these technologies will require careful oversight and attention to data ownership, access, and interoperability. Together or in combination, these emerging digital technologies might represent the next leap forward in SCA survival.

      Funding Sources

      None.

      Disclosures

      Dr Allan received an honorarium from Zoll Medical Inc, for a speaking engagement. Dr Sapp reports receiving research grants from Biosense WebsterInc and Abbott Laboratories, speaking honoraria from Medtronic, Biosense Webster Inc, and Abbott Laboratories and a consulting honorarium from Varian Medical Systems, USA. The remaining authors have no conflicts of interest to disclose.

      Supplementary Material

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