Automated Real-time Feedback on CPR Study

For the first three to six months, participating EMS agencies will have defibrillators with automated, real-time feedback inactivated. During this period, the baseline rate of ROSC (and secondary outcomes) will be collected. At the end of this baseline period, EMS agencies will be randomized to one of two interventions, with randomization stratified within site by agency, station, or device. All clusters will cross-over to the opposite feedback strategy at least once during the intervention phase.