AED Placement and Effectiveness
AED Placement and Effectiveness
Abstract & Commentary
By John P. DiMarco, MD, PhD
Source: Folke F, et al. Location of cardiac arrest in a city center. Strategic placement of automated external defibrillators in public locations. Circulation. 2009;120:510-517
Folke et al from Copenhagen, Denmark, studied the consequences of automatic external defibrillator (AED) placement in a large metropolitan area. The study involved the placement and use of AEDs in Copenhagen, a city with a population of 600,000 and an area of 97 km2. The central part of the city is served by a single emergency medical services (EMS) system with physician-staffed ambulances. The survey covers data from January 1994 through December 2005. During this period, there were 1,274 cardiac arrests in public areas, 26% of the total number of cardiac arrests to which EMS responded. During 2005, the final year of the study, 104 AEDS were placed in municipal or public buildings throughout the city. No data were used to guide the initial placements. A plot of AED location vs. cardiac arrest location within a 100-meter radius was then generated. Cost-effectiveness also was estimated. Each AED was assigned a cost of $2,000 and assumed to have an expected useful life of 10 years. Prior to AED placement, the cardiac arrest survival rate in Copenhagen had been 13.9%. Cost-effectiveness was estimated based on a projected increase in survival to 25%.
During the study period, there were 1,274 cardiac arrests in public places. The highest density of cardiac arrests was in the city center and along major traffic routes. There were 73 cardiac arrests in grids containing a major train station, 175 in grids containing a high-density public area, 118 in grids containing a supermarket, 164 in grids containing a large industrial business, and 54 in grids containing a high school or primary school. The observed annual rate for cardiac arrest was highest in train stations, high-density public areas, shopping malls, bus terminals, and sport centers. High-incidence grids, designated by a probability of one arrest every five years within a 100-meter radius, included 10.6% of the total study area but 66.8% of all the public cardiac arrests. The results of unguided AED placement were disappointing. Not one of the 104 unguided AEDs had been used during the year they were in place and would potentially cover only 29 of the cardiac arrests in the entire study period. Calculated cost estimates of AED placement showed that cost per quality of life increased from $41,000 to $51,200 to $68,300, respectively, as the probability of AED use every five years fell from 100% to 80% to 60%, respectively.
Folke et al conclude that their data show that a high proportion of public cardiac arrests can be covered by strategic placement of AEDs within a limited portion of a city center with acceptable cost. Most arrests will be covered if AEDs are placed in a 100-meter radius of areas expected to have a cardiac arrest every five years. Strategic EMS initiatives focusing on selective placement of AEDs in areas with high incidence of cardiac arrests are needed.
For the effectiveness of public access AEDs to be optimal, the devices will need to be placed in areas where cardiac arrests occur with some reasonable frequency and where the arrests are witnessed by willing bystanders. They have been shown to be highly effective in casinos, airports, and on planes. This paper analyzes optimal placement on a citywide basis. Areas with dense pedestrian traffic were shown to be the best sites for AED placement, and an intelligent analysis of cardiac arrest incidence data would allow the most efficient use if only a limited number of AEDs were available. However, as more AEDs are used, costs per unit should drop and many private businesses or individuals may consider purchasing one. A network of AEDs purchased by public agencies, commercial firms, and private individuals will likely provide much better coverage in the future than we have now.Folke et al from Copenhagen, Denmark, studied the consequences of automatic external defibrillator (AED) placement in a large metropolitan area.
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