Longer retrieval distances to the automated external defibrillator reduces survival after out-of-hospital cardiac arrest

Abstract

Aims: To evaluate and compare survival after out-of-hospital (OHCA), where an automated external defibrillator (AED) was used, in densely, moderately and thinly populated areas. Also, to evaluate the association between AED retrieval distance and survival after OHCA.

Methods: From 2014 to 2018, AEDs used during OHCA in the region of Southern Denmark were systematically collected. OHCAs were included if the OHCA address was known. OHCAs at nursing homes were excluded. To evaluate population density, a map with 1000 × 1000 meter grid cells was used with each cell color-graded according to the number of inhabitants. Densely, moderately and thinly populated areas were defined as ≥200 inhabitants, 20-199 inhabitants and 0-19 inhabitants per km², respectively. Primary outcome was 30-day survival.

Results: A total of 423 cases of OHCA were included, of which 207 (49%) occurred in densely populated areas, while 78 (18%) and 138 (33%) occurred in moderately and thinly populated areas, respectively. AED retrieval distances were: densely populated 105 m (IQR 5-450), moderately populated 220 m (IQR 5-450) and thinly populated 350 m (IQR 5-1500) (P < 0.001). Thirty-day survival was 40%, 31% and 34%, respectively (P = 0.3). In a multivariable regression analysis, mortality increased with 10% per 100 m an AED was placed further away from the site of OHCA.

Conclusion: Survival after OHCA, where an AED was used, did not seem to differ in thinly, moderately and densely populated areas. The length of the AED retrieval distance, however, was correlated with reduced survival after adjusting for other potentially explanatory variables.

Keywords: Automated external defibrillator; Bystander defibrillation; Out-of-hospital cardiac arrest; Resuscitation; Volunteer first responders.