Walking Route-Based Calculation is Recommended for Optimizing Deployment of Publicly Accessible Defibrillators in Urban Cities

Background A straight line-based model is often used to calculate the distance between an out-of-hospital cardiac arrest (OHCA) and the location of an automated external defibrillator (AED). This model may be inaccurate as it overlooks any obstacles between the OHCA and AED. This study aimed to elucidate the effect of the straight line-based and walking route-based calculation on the average distance between an historical OHCA and the closest AED and the coverage rate of AEDs, ie, the proportion of historical OHCAs that were within 100 meters of an AED. It is hoped that the findings will help policy makers in deploying AEDs in optimal urban settings. Methods and Results This was an observational study conducted in Hong Kong. The average distance between an historical OHCA and its closest AED and the coverage rate of AEDs were calculated with both the straight line-based and walking route-based model. A total of 1637 AEDs and 5119 cases of OHCA were included for analysis. The average distances calculated by the straight line-based and walking route-based model were 230.8 and 545.3 meters, respectively. The coverage rate calculated by the straight line-based model was 30.04%, while that by the walking route-based model was 11.17%. Conclusions The straight line-based model may underestimate the average distances and overestimate the coverage rate in an urban setting. The walking route-based model may be more useful for studies of AED deployment in urban cities.