title: Overcoming Spatial and Temporal Barriers to Public Access Defibrillators Via Optimization.
abstract: Immediate access to an automated external defibrillator (AED) increases the chance of survival for out-of-hospital cardiac arrest (OHCA). Current deployment usually considers spatial AED access, assuming AEDs are available 24 h a day.
  
  
  
  The goal of this study was to develop an optimization model for AED deployment, accounting for spatial and temporal accessibility, to evaluate if OHCA coverage would improve compared with deployment based on spatial accessibility alone.
  
  
  
  This study was a retrospective population-based cohort trial using data from the Toronto Regional RescuNET Epistry cardiac arrest database. We identified all nontraumatic public location OHCAs in Toronto, Ontario, Canada (January 2006 through August 2014) and obtained a list of registered AEDs (March 2015) from Toronto Paramedic Services. Coverage loss due to limited temporal access was quantified by comparing the number of OHCAs that occurred within 100 meters of a registered AED (assumed coverage 24 h per day, 7 days per week) with the number that occurred both within 100 meters of a registered AED and when the AED was available (actual coverage). A spatiotemporal optimization model was then developed that determined AED locations to maximize OHCA actual coverage and overcome the reported coverage loss. The coverage gain between the spatiotemporal model and a spatial-only model was computed by using 10-fold cross-validation.
  
  
  
  A total of 2,440 nontraumatic public OHCAs and 737 registered AED locations were identified. A total of 451 OHCAs were covered by registered AEDs under assumed coverage 24 h per day, 7 days per week, and 354 OHCAs under actual coverage, representing a coverage loss of 21.5% (p < 0.001). Using the spatiotemporal model to optimize AED deployment, a 25.3% relative increase in actual coverage was achieved compared with the spatial-only approach (p < 0.001).
  
  
  
  One in 5 OHCAs occurred near an inaccessible AED at the time of the OHCA. Potential AED use was significantly improved with a spatiotemporal optimization model guiding deployment.
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Christopher L F
authors.initials: CL
authors.lastname: Sun
authors.affiliation: Department of Industrial Engineering and Business Information Systems, University of Twente, Enschede, the Netherlands.
authors.forename: Derya
authors.initials: D
authors.lastname: Demirtas
authors.affiliation: Department of Emergency Medicine, Queen's University at Kingston, Kingston, Ontario, Canada; Rescu, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Brooks
authors.affiliation: Rescu, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada; Division of Emergency Medicine, Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Laurie J
authors.initials: LJ
authors.lastname: Morrison
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada; Rescu, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada. Electronic address: tcychan@mie.utoronto.ca.
authors.forename: Timothy C Y
authors.initials: TC
authors.lastname: Chan
mesh_terms: D022126:Access to Information; D016887:Cardiopulmonary Resuscitation / Q000592:standards*; D047548:Defibrillators / Q000706:statistics & numerical data*; D004632:Emergency Medical Services / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D058687:Out-of-Hospital Cardiac Arrest / Q000401:mortality / Q000628:therapy*; D011159:Population Surveillance / Q000379:methods*; D011634:Public Health; D012189:Retrospective Studies; D015996:Survival Rate / Q000639:trends
keywords: automated external defibrillator; cardiac arrest; emergency cardiac care; resuscitation