In major cities, optimal distribution of automatic external defibrillators (AED) has long been debated. International guidelines recommended placing AED where at least an out-of-hospital cardiac arrest (OHCA) occurs every 2 years. However, bystander awareness of AED location is often limited. The aim of the study was to determine a potential strategic AED placement policy.

We included all OHCA managed in Paris by Emergency Medical Services between 2000 and 2010. First, we worked on different scenarios of regular AED placement according to several deployment distances (from 200 meters to 2000 meters), then we analyzed median distance between these AED potential placements and included OHCA. Second, we identified different types of public facilities in Paris and we calculated the median distance according to each type of public facilities. We evaluated the number needed of AED in each case.

Among the 4176 OHCA of presumed cardiac etiology, 1415 (34%) occurred out-of-home and 1355 were eventually geocoded (Figure). Median distances between OHCA and district councils (n=20), post offices (n=195), subway stations (n=302), bike sharing stations (n=957) and pharmacies (n=1466) were 1052, 324, 239, 137 and 142 meters respectively.

Increasing number of AED following a regular distribution on the territory decreases drastically the median distance between AED potential placement and OHCA until a certain number (350 AED for Paris). Additional AED placement benefit becomes less apparent. AED public facilities coverage strategy may help to optimize AED placement. The choice of the best public facility should be based on its number and repartition on the territory and its proximity to OHCA.