Association Between Number of Volunteer Responders and Interventions Before Ambulance Arrival for Cardiac Arrest

Mads Christian Tofte Gregers*, Linn Andelius, Julie Samsoee Kjoelbye, Anne Juul Grabmayr, Louise Kollander Jakobsen, Nanna Bo Christensen, Astrid Rolin Kragh, Carolina Malta Hansen, Rasmus Meyer Lyngby, Ulla Væggemose, Christian Torp-Pedersen, Annette Kjær Ersbøll, Fredrik Folke

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Background: Volunteer responder (VR) programs for activation of laypersons in out-of-hospital cardiac arrest (OHCA) have been deployed worldwide, but the optimal number of VRs to dispatch is unknown. Objectives: The purpose of this study was to investigate the association between the number of VRs arriving before Emergency Medical Services (EMS) and the proportion of bystander cardiopulmonary resuscitation (CPR) and defibrillation. Methods: We included OHCAs not witnessed by EMS with VR activation from the Capital Region (September 2, 2017, to May 14, 2019) and the Central Region of Denmark (November 5, 2018, to December 31, 2019). We created 4 groups according to the number of VRs arriving before EMS: 0, 1, 2, and 3 or more. Using a logistic regression model adjusted for EMS response time, we examined associations between the number of VRs arriving before EMS and bystander CPR and defibrillation. Results: We included 906 OHCAs. The adjusted ORs for bystander CPR were 2.40 (95% CI: 1.42-4.05), 3.18 (95% CI: 1.39-7.26), and 2.70 (95% CI: 1.32-5.52) when 1, 2, or 3 or more VRs arrived before EMS (reference), respectively. The adjusted OR for bystander defibrillation increased when 1 (1.97 [95% CI: 1.12-3.52]), 2 (2.88 [95% CI: 1.48-5.58]), or 3 or more (3.85 [95% CI: 2.11-7.01]) VRs arrived before EMS (reference). The adjusted OR of bystander defibrillation increased to 1.95 (95% CI: 1.18-3.22) when ≥3 VRs arrived first compared with 1 VR arriving first (reference). Conclusions: We found an association of increased bystander CPR and defibrillation when 1 or more VRs arrived before the EMS with a trend toward increased bystander defibrillation with increasing number of VRs arriving first.

Original languageEnglish
JournalJournal of the American College of Cardiology
Issue number7
Pages (from-to)668-680
Publication statusPublished - 21. Feb 2023


  • AED
  • bystander
  • cardiopulmonary resuscitation
  • defibrillation
  • OHCA
  • out-of-hospital cardiac arrest
  • smartphone app
  • volunteer responders


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