Optimizing locations for the installation of automated external defibrillators (AEDs) in urban public streets through the use of spatial and temporal weighting schemes

Objective: Out-of-hospital cardiac arrest (OHCA) occurs when the heart is deprived of oxygen without immediate medical treatment. The use of publicly accessible automated external defibrillators (AEDs) is generally considered to be an effective pre-hospital measure. Although studies have been undertaken to determine the locations of AED installations, the spatial and temporal characteristics of OHCA occurrence have not been considered comprehensively. This study attempts to assess the feasibility of using the 7-Eleven chain of convenience stores as possible locations for the installation of AEDs to capture the spatial and temporal characteristics of OHCA patients. Methods: The methodological framework was divided into two stages. The first stage involved the development of two weighting schemes, a temporally weighted model (TWM) and a spatially weighted model (SWM), to capture the temporal and spatial variations in selecting AED locations. In the second stage, we proposed a stirring genetic algorithm (SGA) to select the limited subset of 7-Elevens covering the most weighted OHCA occurrences from the first stage. Results: We considered two modes of conveyance, human running and vehicle transportation, by setting the service range of the 7-Elevens at 100 and 300 m. Among a total of 323 OHCA cases within 100 m of a 7-Eleven, our results showed that there were 177 cases (54.8%) to be covered in the TWM and 150 cases (46.44%) in the SWM. When the service range was increased to 300 m, the total number of OHCA cases increased to 1271, which included 659 cases (51.85%) to be covered in the TWM and 522 cases (41.07%) in the SWM. We also found that, in public streets in urban settings, the TWM selected more 7-Elevens in commercial areas, while the SWM selected more stores in residential areas. Conclusions: We conclude that each 7-Eleven has a different role for allocating AEDs in an urban setting. The AEDs at 7-Elevens in commercial areas help to compensate for the temporal gap of emergency medical service (EMS) in nighttime occurrences and for a high incidence of OHCA patients. For convenience stores in residential areas, AEDs help to compensate for the spatial gap in areas that are far from fire stations.