Not Just Where but When: Public Access to Defibrillators Isn’t Round the Clock

Having fast access to an automated external defibrillator (AED) raises the odds of someone surviving an out-of-hospital cardiac arrest, but many AEDs may not be available 24 hours a day. Results of a new study show that considering not only where the lifesaving tools are available but when they can be used may improve access.

Traditionally, defibrillators have been placed in locations where a cardiac arrest was known to have occurred in the past, explained senior author Timothy C.Y. Chan, PhD (University of Toronto, Canada), to TCTMD. But those decisions most likely did not take into account the time that the arrest occurred, he said.

For their retrospective study, published online ahead of the August 23, 2016, issue of the Journal of the American College of Cardiology, Chan along with lead author Christopher L.F. Sun, BASc (University of Toronto), and colleagues identified 2,440 nontraumatic public out-of-hospital cardiac arrests that occurred in Toronto, Canada, over a 9-year period ending in 2014. As of March 2015, the city had 737 registered AEDs.

When coverage was assumed to be 24 hours per day and 7 days per week, 451 of those events occurred within range of an AED. But because some buildings were closed at night or on weekends, only 354 arrests (21% less) actually took place near an AED that could be accessed.

Sun et al developed two models to determine where AEDs should be placed. Entering data on time as well as on location increased coverage by 25.3% compared with considering only location.

Public vs Private

Asked about the study’s real-world implications, Chan said he “would be over the moon if this type of research and these sorts of models could help inform decision makers going forward.”

But at the moment, he acknowledged, such decisions can be haphazard. In some regions, placement is coordinated by someone in the city planning office or emergency medical services (EMS) seeking to optimize resources. Sometimes there is no centralized planning at all, he said. Nor do EMS personnel necessarily know where to find the AEDs that are out there, given that there is no mandatory registry tracking where they’re located.

In an accompanying editorial, Robert J. Myerburg, MD (University of Miami Miller School of Medicine, Miami, FL), suggests that these findings, though “intriguing,” may have a “relatively small” impact on public health.

“Approximately 70% to 80% of all [out-of-hospital cardiac arrests] occur in the home, not public locations, and survival after in-home cardiac arrest is far lower than observed in public locations,” he writes.

Chan agreed that it is important to look at the big picture. And while the current study is focused on the minority of cardiac arrests that occur in public, these are the cases where there is the potential to make the most difference, he stressed.

“If a cardiac arrest happens in a private location, there might not be a bystander. There might not be anything to do,” Chan said. “But in a public domain—if you’re in a shopping mall or if you’re walking down the street—chances are there could be a bystander who will come across you or even witness you collapsing. By putting AEDs in their hands, we can actually have a big impact.”





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  • Sun CLF, Demirtas D, Brooks SC, et al. Overcoming spatial and temporal barriers to public access defibrillators via optimization. J Am Coll Cardiol. 2016;68:836-845.

  • Myerburg RJ. Optimizing out-of-hospital cardiac arrest responses: an exercise in time, distance, and communication. J Am Coll Cardiol. 2016;68:846-848.

  • The study was funded by the ZOLL Foundation.
  • Sun reports receiving an Ontario Graduate Scholarship.
  • Chan reports no relevant conflicts of interest.
  • Myerburg reports being supported in part by the AHA Chair in Cardiovascular Research at the University of Miami Miller School of Medicine and by a research grant from the Miami Heart Research Foundation.

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