Real-time CPR feedback effective in EMS systems with well-trained rescuers

CPR performance improved, though return of pulses and survival to discharge did not

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.

Twenty-one EMS agencies from three ROC regions in the US and Canada (King County, WA; Pittsburgh, PA; Thunder Bay, ON) enrolled 1,521 treated non-traumatic cardiac arrest patients over the course of 25 months. The study included all eligible patients who received EMS rescue shocks or chest compressions. Participating agencies were provided by the manufacturer with commercially available devices equipped with visual and audible real-time feedback coaching the quality of CPR. Agencies provided training to their EMS providers in a manner consistent with local policy and standards.

In this prospective randomized trial, EMS agencies were assigned to one of two treatment groups, audible 'feedback on' or 'feedback off.' When feedback was on, real-time audible and visual prompts advised providers to conform CPR to American Heart Association (AHA) guidelines. The assignment changed every two to seven months, depending on the expected number of treated cardiac arrests. When assigned to 'feedback on,' EMS providers muted the audible coaching in 15% of cases. Baseline characteristics of patients randomized to each of the two groups were comparable.

The primary objective of the study was to determine the proportion of patients with a return of spontaneous circulation (ROSC) during the prehospital course of EMS care. ROSC was defined as the presence of a palpable pulse in any blood vessel for any length of time. The difference observed between the two study groups was not statistically significant: return of spontaneous circulation occurred in 48.0% of 'feedback on' and 48.8% with 'feedback off.'

Secondary outcomes of the study were also reported:

• Survival to hospital discharge was not significantly different between the two treated groups, with 10.6% of 'feedback on' and 12.2% of 'feedback off' surviving.
• Compliance with AHA recommendations for quality CPR improved modestly when assigned to 'feedback on', with an observed reduction in compression rate, an increase in the depth of compressions, and an increase in the amount of time spent doing CPR.

Researchers will further analyze and publish the final data in the coming months.

"In this trial, the quality of CPR in the 'feedback off' group was substantially better than has been previously reported for prehospital EMS and may suggest that the potential clinical benefit of real-time CPR feedback is limited in EMS systems with well-trained rescuers," said ROC principal investigator, Clif Callaway, M.D., Ph.D., associate professor and vice chair of emergency medicine at the University of Pittsburgh. Dr. Callaway also noted, "This study's attention to the quality of CPR may well have affected the results of both arms of the study, regardless of whether real-time feedback was turned on or off."

When administered as soon as possible, CPR and, in some cases, rapid treatment with a defibrillator - a device that sends an electric shock to the heart to try to restore its normal rhythm - can be lifesaving. When delivered by EMS professionals, CPR is a combination of chest compressions, to keep oxygen-rich blood circulating until an effective heartbeat is restored, and rescue breathing. Lay bystanders are encouraged to immediately begin CPR using only chest compressions until professional help arrives, according to the American Heart Association.