EurekAlert! -- Emergency medical service (EMS) providers in the United States assess an estimated 350,000 cardiac arrests each year. Only 5 to 10 percent of people who have sudden cardiac arrest survive. Better quality cardiopulmonary resuscitation (CPR) provided by prehospital EMS providers may be associated with better patient outcome. The Resuscitation Outcomes Consortium (ROC) is the largest clinical research network to study prehospital treatments for cardiac arrest in the United States and Canada. ROC conducted the first randomized study to assess if real-time audio-feedback, during the EMS prehospital course of care, would improve clinical outcome. Results of the study were presented on November 15th during the Resuscitation Science Symposium 2009 program.