Frequently Asked Questions

Pre-hospital Interventions in Cardiac Arrest

Note: This study was completed on November 6, 2009
For more information about the completion of the study,
please read the official OHSU press release
and the NIH press release here 

ROC PRIMED Questions and Answers

  1. What is the ROC PRIMED study?
  2. Where was ROC PRIMED conducted?
  3. Why was the ROC PRIMED study enrollment stopped?
  4. When did the study stop enrollment?
  5. How many patients were enrolled?
  6. What does neurologically intact survival mean?
  7. Were there any deaths as a result of study participation?
  8. What do the results of the study mean?
  9. When will the final study results be available?
  10. What is an ITD?
  11. What have other studies of ITD shown?
  12. What have other studies of Analyze Late versus Analyze Early shown?
  13. How did patients indicate they would participate in this study?
  14. What is an exception from informed consent?
  15. Would you let a family member be enrolled in a future study like this?
  16. Should public bystanders be performing full CPR, with breathing and chest compressions, or using the "Hands Only" method that was introduced last year?

What is the ROC PRIMED study?

ROC PRIMED stands for the Resuscitation Outcomes Consortium Prehospital Resuscitation using an IMpedance valve and Early versus Delayed (ROC PRIMED) study. This clinical trial examined the usefulness of two resuscitation strategies for patients who suffer cardiac arrest, when the heart abruptly stops, outside of a hospital setting. The study involved emergency medical services (EMS) providers at locations across the United States and Canada. The goal of the study was to increase the number of neurologically intact patients, who can still function independently, that survive cardiac arrest outside of a hospital setting. ROC is the largest clinical research network to study prehospital treatments for cardiac arrest in the United States and Canada and is composed of 10 clinical centers and a data coordinating center.

One strategy looked at when to analyze the patient's heart rhythm to determine whether defibrillation is needed, methods known as Analyze Early and Analyze Later. Some EMS providers perform cardiopulmonary resuscitation (CPR) for 30-90 seconds before analyzing the heart's rhythm, and, if necessary, defibrillate to restore the heart to its normal rhythm (Analyze Early). Other EMS providers perform CPR for three minutes before analyzing the heart rhythm (Analyze Later) and defibrillate if necessary. There is evidence that the longer CPR duration helps oxygenated blood circulate more, which may prime the heart to receive the most benefit from defibrillation. Other studies suggest that delivering defibrillation sooner might be more helpful. The ROC PRIMED study found both to be equally beneficial, with no improvement or decline in patient survival rates.

The other strategy in ROC PRIMED looked at the use of an impedance threshold device (ITD), to help improve blood flow during CPR given by EMS providers. An ITD, also known as an impedance valve, is a small, hard plastic device about the size of a fist that is attached to the face mask or breathing tube during CPR administered by EMS providers. Although the device is attached to the face mask or breathing tube during CPR, it is not intended to help with breathing. Instead, it is designed to increase the degree of negative intrathoracic pressure during decompression of the chest. Some previous smaller studies on humans and in animal models showed short-term improvement in blood flow in patients who went into cardiac arrest. However, in this study, the use of the device did not appear to improve or decrease patient survival rates.

ROC PRIMED FAQ - Page 1    |    Page 2    |    Page 3

More information:

Study Results

Results were published in the New England Journal of Medicine on September 1, 2011.

Cardiac Arrest and the Limitations of Clinical Trials
Read the Editorial

A Trial of an Impedance Threshold Device in Out-of-Hospital Cardiac Arrest
Read the Article

Early versus Later Rhythm Analysis in Patients with Out-of-Hospital Cardiac Arrest
Read the Article