Should EMS abandon continuous chest compression CPR?

A Resuscitation Outcomes Consortium study comparing two CPR methods of out-of-hospital cardiac arrest found little difference in neurologically intact survival

By Christopher T. Boyer

A Resuscitation Outcomes Consurtium (ROC) study published in the New England Journal of Medicine is rapidly circulating in EMS social networks, with some readers pointing to the article as proof that continuous CPR with no pauses for ventilation is not the best way for EMS providers to perform CPR.

While the study authors did state in their conclusion that "a strategy of continuous chest compressions with positive-pressure ventilation did not result in significantly higher rates of survival or favorable neurologic status than the rates with a strategy of chest compressions interrupted for ventilation" a thorough examination of the article is required to validate the conclusion of some EMS providers that a return to standard CPR is necessary.

Study design: Continuous chest compression versus standard CPR
This is an incredibly well-designed study. The researchers organized 114 EMS agencies into 47 clusters and randomly assigned each cluster to either the control (traditional CPR) or the experimental (non-interrupted CPR) groups.

The groups where then swapped during the study to ensure the sample for each group included participants from each survey site. To ensure compliance with the protocol, each site was initially enrolled in a trial phase before contributing data to the study.

The study utilized CPR feedback devices to record CPR quality data. The data collection tools were audited for accuracy by an internal study monitoring committee.

Patient population
At the conclusion of the study the authors had enrolled 35,904 patients. The authors excluded 9,756 patients for not meeting the study requirements, which were EMS witnessed arrest, CPR prior to the arrival of the participating agency, DNR orders, and patients in protected populations.

Of the remaining 26,148 patients 2,500 did not have available data for inclusion in the study, resulting in a total of 23,648 patients actually enrolled. After exclusions 12,613 patients were in the continuous chest compression (experimental) group and 11,035 patients were in the standard CPR (control) group. 

Survival to hospital discharge
The researchers analyzed the patients for survival to hospital discharge. Nine percent of the patients in the continuous chest compression group survived to hospital discharge while 9.7 percent of those who received standard CPR had the same outcome.

The authors concluded they could find no benefit in continuous CPR.

Is this the end of continuous compression CPR?
A single study does not necessarily prove anything. More studies, modeled after the ROC study, are necessary to validate the findings of the authors. 

The researchers did not find continuous chest compressions harmful, but rather that there is no benefit of continuous compressions compared to standard CPR. Like the research on mechanical CPR studies, we might reframe the findings to state that it shows that continuous compressions CPR is at least as good as standard CPR.

Limitations of the study
Like any study we need to examine the limitations of the study before making rash decisions about changing standing orders or treatment protocols. Pauses between compressions for the standard CPR group were very short in this study, leading us to consider a potential Hawthorne effect, which is when participants in a study change or model their behavior to fit what the examiner is expecting of them in the study. 

We do not know how long the time between compressions would have been had the participants been unaware they were participating in a study. The study did not control for other factors that contribute to cardiac arrest outcomes, such as in-hospital care and the amount of pressure introduced into the thoracic cavity due to positive pressure ventilation. The algorithm utilized to examine the data excluded more participants in the interrupted chest compression group than in the continuous compression group, potentially skewing the results.  

Opportunities for further research
Additional studies are needed to further investigate the efficacy of continuous compression CPR. Perhaps a follow-up study should incorporate the use of a manometer to measure ventilation rates. Previous studies demonstrated a benefit by integrating passive oxygenation via a non-rebreathing mask during continuous compressions. This treatment was not included in this study.

About the author
Chris Boyer, NRP, FP-C., M.P.A. is a lead paramedic instructor at Delaware Technical Community College. He has been involved in EMS since 1999, and has worked in the prehospital and Air Medical Environments. He is a 2003 graduate of the Pennsylvania College of Technology’s Paramedic Program and is currently pursuing the Doctor of Business Administration degree at Wilmington University.   

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