Population movement and sudden cardiac arrest location.

BACKGROUND: Although the benefits of automatic external defibrillators are undeniable, their effectiveness could be dramatically improved. One of the key issues is the disparity between the locations of automatic external defibrillators and sudden cardiac arrests (SCAs). METHODS AND RESULTS: From emergency medical services and other Parisian agencies, data on all SCAs occurring in public places in Paris, France, were prospectively collected between 2000 and 2010 and recorded using 2020 grid areas. For each area, population density, population movements, and landmarks were analyzed. Of the 4176 SCAs, 1255 (30%) occurred in public areas, with a highly clustered distribution of SCAs, especially in areas containing major train stations (12% of SCAs in 0.75% of the Paris area). The association with population density was poor, with a nonsignificant increase in SCAs with population density (P=0.4). Occurrence of public SCAs was, in contrast, highly associated with population movements (P<0.001). In multivariate analysis including other landmarks in each grid cell in the model and demographic characteristics, population movement remained significantly associated with the occurrence of SCA (odds ratio, 1.48; 95% confidence interval, 1.34-1.63; P<0.0001), as well as grid cells containing train stations (odds ratio, 3.80; 95% confidence interval, 2.66-5.36; P<0.0001). CONCLUSIONS: Using a systematic analysis of determinants of SCA in public places, we demonstrated the extent to which population movements influence SCA distribution. Our findings also suggested that beyond this key risk factor, some areas are dramatically associated with a higher risk of SCA.

Optimization of automated external defibrillator deployment outdoors: An evidence-based approach.

BACKGROUND: The benefits of available automatic external defibrillators (AEDs) for out-of-hospital cardiac arrests (OHCAs) are well known, but strategies for their deployment outdoors remain somewhat arbitrary. Our study sought to assess different strategies for AED deployment. METHODS: All OHCAs in Paris between 2000 and 2010 were prospectively recorded and geocoded. A guidelines-based strategy of placing an AED in locations where more than one OHCA had occurred within the past five years was compared to two novel strategies: a grid-based strategy with a regular distance between AEDs and a landmark-based strategy. The expected number of AEDs necessary and their median (IQR) distance to the nearest OHCA were assessed for each strategy. RESULTS: Of 4176 OHCAs, 1372 (33%) occurred in public settings. The first strategy would result in the placement of 170 AEDs, with a distance to OHCA of 416 (180-614) m and a continuous increase in the number of AEDS. In the second strategy, the number of AEDs and their distance to the closest OHCA would change with the grid size, with a number of AEDs between 200 and 400 seeming optimal. In the third strategy, median distances between OHCAs and AEDs would be 324m if placed at post offices (n=195), 239 at subway stations (n=302), 137 at bike-sharing stations (n=957), and 142 at pharmacies (n=1466). CONCLUSION: This study presents an original evidence-based approach to strategies of AED deployment to optimize their number and location. This rational approach can estimate the optimal number of AEDs for any city.