A subset of emergency medical services (EMS) agencies that are participating in the Resuscitation Outcomes Consortium (ROC) are adopting new monitor/defibrillators that are capable of monitoring CPR process during attempted resuscitation of patients in cardiac arrest, as well as providing automated real-time feedback about this process to EMS providers so as to improve compliance with recommended guidelines for CPR. Monitoring of CPR process during attempted resuscitation is an important step towards reducing the potential for poorly-performed CPR to modify the effect of the study interventions upon outcome. Clusters formed of rigs, an individual agency or groups of agencies were randomized to turn feedback on or off. After a fixed period of time, each cluster crossed over to the other arm. An unequal number of subjects were enrolled during each period.
