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

Abstract

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.

Calculating real-world travel routes instead of straight-line distance in the community response to out-of-hospital cardiac arrest

“… 6 Researchers in Hong Kong demonstrated substantially increased travel distances between 5119 historical OHCAs and 1637 public-access AEDs using real-world estimates rather than straight-line estimates. The average increased from 231 m to 543 m. 7 …”

“… 6 In Hong Kong, calculating actual walking distance increased the average distance from an OHCA to the nearest AED from 231 m to 545 m, and reduced the proportion of AEDs within 100 m from 30% to 11%. 7 In Italy, the geographical area that an AED covered was similar comparing a 200 m walking distance with a 100 m radius. 8 Travel modality and speed will also affect an AED’s effective coverage area.…”

Risk of Physical Injury for Dispatched Citizen Responders to Out‐of‐Hospital Cardiac Arrest

“…However, we calculated distances as straight line, which most likely have underestimated the distances compared with real‐world route distances. Previous studies have shown that route distances are ≈1.3 to 2.4 times longer than straight‐line distances, 13 , 14 and routes for citizen responders might be unwalkable because of water or terrain. 15 Traveling a longer distance could increase the risk of getting injured.…”

Strategic placement of automated external defibrillators (AEDs) for cardiac arrests in public locations and private residences

“…For simplicity, we modelled circular coverage areas around AEDs, whereas it is possible to model more realistic walking-routes based on road/path networks. 39 We did not distinguish cardiac arrests based on demographic and arrest characteristics, other than stratifying by arrests in public locations versus private residences. We treated proximity as a binary variable – whereby an OHCA case was considered to have AED coverage if one or more AEDs were within a threshold distance of the arrest, regardless of the distance within or beyond that threshold.…”