I'm currently working on finding a replacement for my campus service's Lifepak 500, as Physio-Control won't be providing an update for the 2010 AHA protocols. I know that most AED's are pretty much interchangeable, but I'd like to find some sort of guidelines on how to select an AED for EMS. I've got the list narrowed down to Cardiac Science, Physio-Control, Zoll, and Philips. Any suggestions? A google search turned up mainly resources for layperson AED programs, and the state's website wasn't helpful.