The first six minutes when EMTs care for patients who have suffered out-of-hospital cardiac arrest are crucial to survival, but how to provide appropriate cardiopulmonary resuscitation has been debated since the release of a report in the Journal of the American Medical Association in 2010. Its findings appeared to show a greater benefit for continuous compressions with minimal interruption for ventilation versus the more accepted 30 compressions with a pause for two ventilations. (2010;304:1447.)
The Seattle-based Resuscitation Outcomes Consortium, however, conducted the largest trial to date of early CPR by EMS providers in December 2015, and found no statistical difference between the two cardiopulmonary resuscitation methods used in those crucial minutes. (http://1.usa.gov/1RnE5uW.) The study was listed as one of the top 10 research advances of 2015 by the American Heart Association.
The authors of that large randomized trial of adults with out-of-hospital cardiac arrest found “a strategy of continuous manual chest compressions with positive-pressure ventilation was not associated with a significantly higher rate of survival to discharge or favorable neurologic function than a strategy of manual chest compressions with interruptions for ventilation performed by EMS providers.” (N Engl J Med 2015;373:2203.)
The group assigned to receive continuous chest compressions had significantly lower rates of transport and admission to the hospital, as well as shorter hospital-free survival times than the group assigned to receive interrupted chest compressions, the researchers wrote. “Patients who received continuous chest compressions had significantly lower survival rates than those who received compressions with interruptions.”
“The results were in the opposite direction of what we had envisioned with the original hypothesis,” said Susanne May, PhD, an associate professor of biostatistics at the University of Washington in Seattle, a member of the Resuscitation Outcomes Consortium, and an author of the report. “I could not see anything to say that continuous chest compressions were better. We were also not able to show statistically that 30 compressions to two ventilations were better. There was no significant difference overall, but when you looked at the data carefully, it appeared the compressions interrupted for ventilation may be better.”
Surviving to Discharge
The group included 23,711 patients, with 12,653 assigned to the intervention group and 11,058 to the control group. The primary endpoint of the study was survival to discharge. A total of 1,129 (9%) of those in the continuous chest compression group survived to discharge, and 1,072 (9.7%) in the interrupted compression group survived with favorable neurologic function at discharge. Length of survival without rehospitalization was significantly shorter (0.2 days) in the continuous compression group compared with the interrupted compression group.
The research was performed in EMS agencies experienced in performing good CPR, according to Graham Nichol, MD, MPH, a professor of medicine and the director of the Center for Prehospital Emergency Care at the University of Washington-Harborview Medical Center, and an author of the report.
“This might or might not be informative for sites or EMS groups, agencies, or providers where the quality of CPR might not be as good. This is the best evidence for answering the question [of which CPR is better],” he said.
The trials took place in 114 emergency medical service agencies and was cluster-randomized with crossover, which means each EMS service was randomly assigned to use one of the two CPR methods and then switched to the other twice each year. Informed consent was waived because of the emergency nature of the intervention. “Keep in mind that, on average, each provider might see only one or two of these cases each year,” Dr. Nichol said.
Testing the 2010 Study
The trial was designed to put the 2010 JAMA findings to the test, said Henry Wang, MD, MPH, an associate professor and the vice chair for research in emergency medicine at the University of Alabama at Birmingham and an author of the Resuscitation Outcomes Consortium study. “It's an important question. The American Heart Association, in its most recent guidelines, said that while the preference is for interrupted chest compressions, it's reasonable for bystanders and trained providers to use continuous compressions,” he said.
Patients receiving continuous chest compressions were less likely to be taken to the hospital, meaning they were more likely to die at the scene, said Clifton Callaway, MD, PhD, a Consortium investigator and the chair of the committee that wrote the AHA guidelines, in a news release from the group. “And if you look at people who died in the hospital and people who got discharged from the hospital, the group with 30 compressions and two breaths were spending more time surviving outside the hospital than the group who got continuous compressions,” he said.
Bentley Bobrow, MD, a professor of emergency medicine at the University of Arizona College of Medicine and a lead author of the 2010 JAMA study, called the large new work an amazing feat. He said some people may have misinterpreted the results of the earlier study.
“We compared continuous chest compression with positive pressure ventilation,” he said. “We tried to do 10 breaths per minute and compare that with 30 compressions and pause for two ventilations. We compared basic life support of resuscitation for just the first six minutes. The rest of the care was the same in both groups.
“It is really important that when people look at the work we did before, there was no randomization. Our study was more observational. We tried to minimize the interruptions in chest compressions and delayed the transition from basic life support to advanced life support,” Dr. Bobrow said. “We delayed the insertion of the advanced airway to prioritize chest compressions as much as possible. The new study is very different from what we did.”
He added that he was not surprised that the authors of the Consortium study found no statistical difference in survival. “I'm not surprised at all that they found no statistical difference in survival,” Dr. Bobrow said. “When you looked at both groups, they both got really high-quality CPR. The chest compression CPR fraction was really high in both groups, much higher than what you find in most real-world situations. I think that's wonderful and what we all want.
“In a lot of places outside of structured research setting, the CPR quality is not what we hoped it would be. In real life, people pause CPR for long periods of time. That's one of the reasons that survival is low a lot of time. Readers should not misinterpret these results. You should minimize all the pauses in the CPR,” he said.
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