• Lena Karlsson, SunChristopher L FCLFMIT Sloan School of Management, Massachusetts Institute of Technology, Cambridge, USA; Healthcare Systems Engineering, Massachusetts General Hospital, Boston, MA, USA., Christian Torp-Pedersen, Kirstine Wodschow, Annette K Ersbøll, Mads Wissenberg, Malta HansenCarolinaCCopenhagen Emergency Medical Services, University of Copenhagen, Denmark; Department of Cardiology, Copenhagen University Hospital Herlev and Gentofte, Denmark., Laurie J Morrison, ChanTimothy C YTCYRescu, Department of Emergency Medicine, St. Michael's Hospital, Division of Emergency Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada; Department of Mechanical and Industrial Engineering, University of Tor, and Fredrik Folke.
• Department of Anaesthesiology, Copenhagen University Hospital Herlev and Gentofte, Denmark; Copenhagen Emergency Medical Services, University of Copenhagen, Denmark. Electronic address: limkarlsson@gmail.com.
• Resuscitation. 2021 Oct 1; 167: 326-335.

AimQuantifying the ratio describing the difference between "true route" and "straight-line" distances from out-of-hospital cardiac arrests (OHCAs) to the closest accessible automated external defibrillator (AED) can help correct likely overestimations in AED coverage. Furthermore, we aimed to examine to what extent the closest AED based on true route distance differed from the closest AED using "straight-line".MethodsOHCAs (1994-2016) and AEDs (2016) in Copenhagen, Denmark and in Toronto, Canada (2007-2015 and 2015, respectively) were identified. Three distances were calculated between OHCA and target AED: 1) the straight-line distance ("straight-line") to the closest AED, 2) the corresponding true route distance to the same AED ("true route"), and 3) the closest AED based only on true route distance ("shortest true route"). The ratio between "true route" and "straight-line" distance was calculated and differences in AED coverage (an OHCA ≤ 100 m of an accessible AED) were examined.ResultsThe "straight-line" AED coverage of 100 m was 24.2% (n = 2008/8295) in Copenhagen and 6.9% (n = 964/13916) in Toronto. The corresponding "true route" distance reduced coverage to 9.5% (n = 786) and 3.8% (n = 529), respectively. The median ratio between "true route" and "straight-line" distance was 1.6 in Copenhagen and 1.4 in Toronto. In 26.1% (n = 2167) and 22.9% (n = 3181) of all Copenhagen and Toronto OHCAs respectively, the closest AED in "shortest true route" was different than the closest AED initially found by "straight-line".ConclusionsStraight-line distance is not an accurate measure of distance and overestimates the actual AED coverage compared to a more realistic true route distance by a factor 1.4-1.6.Copyright © 2021 Elsevier B.V. All rights reserved.

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