Abstract 286: Chance of Bystander Defibrillation According to Number of Nearby Automated External Defibrillators in Out-Of-Hospital Cardiac Arrests

Abstract

Introduction: Use of automated external defibrillators (AEDs) for early defibrillation in out-of-hospital cardiac arrest (OHCA) substantially increases chance of survival. Aim: To examine the relationship between number of nearby accessible AEDs and chance of bystander defibrillation. Methods: All OHCAs (2008-2016), and all publicly available AEDs (2007-2016) in Copenhagen were identified. The route distances between OHCAs and AEDs were calculated to determine the number of accessible AEDs ≤100m of an OHCA (OHCA coverage). Multiple logistic regression was performed to identify the adjusted Odds Ratios (ORs) of OHCA characteristics, including the number of AEDs covering an OHCA, on bystander defibrillation. The regression model was evaluated using receiver operator characteristics (ROC). Multiple logistic regression was also used to determine the predicted probability (through a 2000 iteration bootstrap approach) of bystander defibrillation for public vs. residential OHCAs, according to the number of accessible AEDs covering the OHCA, defined as covered by 0, 1 or >1 AED. Results: There were 1830 AEDs registered in Copenhagen. Of 2500 OHCAs, 75.2% (n=1879) occurred in residential locations of which 98.1% were not covered by an AED, 1.7% were covered by 1 AED only, and 0.2% were covered by >1 AED. The corresponding figures for public OHCAs (n=621, 24.8%) were 87.5%, 9.0%, and 3.5%, respectively. Overall, the number of accessible AEDs covering the OHCA, public location, bystander witnessed arrest and bystander CPR were significantly associated with bystander defibrillation (OR (95%CI): 1.75 (1.24-2.46); 4.25 (2.75-6.57); 3.12 (1.84-5.27); 2.33 (1.44-3.75), respectively. (ROC=82%)). The predicted probability of bystander defibrillation for public OHCAs was 12.2% (95%CI: 9.5-14.9) with no AED covering the OHCA, 24.7% (95%CI: 18.2-31.3) with 1 AED, and 39.8% (95%CI: 23.4-56.7) with >1 AED. The corresponding figures for residential OHCAs were 2.1% (95%CI: 1.5-2.8), 4.3% (95%CI: 2.5-6.8), and 4.0% (95%CI: 0.9-10.8), respectively. Conclusions: Rates of bystander defibrillation significantly improved with increasing number of accessible AEDs covering the OHCA, especially for public OHCAs.