ORLANDO, FL — The largest randomized trial ever conducted in patients with cardiac arrest has shown that, when conducted by emergency medical services (EMS) personnel, CPR with continuous chest compressions and simultaneous ventilation is not better and may actually be worse than interrupting compressions for rescue breathing[1].

Ironically, these major new data, presented at this week's American Heart Association (AHA) 2015 Scientific Sessions, comes out just days after the AHA updated its resuscitation guidelines (published in Circulation on November 3) which recommend for the first time that continuous chest compressions can be used. This was based on several observational studies with historical controls.

The new randomized data—from a trial in 23,000 patients—is seen as the most definitive information on the issue to date and has led to calls for the new guidelines to be reevaluated as soon as possible.

Lead author of the new trial, Dr Graham Nichol (University of Washington, Seattle), told heartwire from Medscape: "To our surprise, survival and neurologic recovery tended to be worse in the continuous-chest-compression group.

"This is a cue for the new guidelines to be reevaluated. The recommendation in the new guidelines for emergency services to use continuous chest compressions was based on observational studies, some of which looked at changing many different factors at the same time. These studies cannot tell which intervention specifically was associated with benefit. But our data are from a very large randomized trial focusing just on the issue of continuous vs interrupted chest compressions and are much more reliable."

The study, conducted by the Resuscitation Outcomes Consortium (ROC), is published in the New England Journal of Medicine to correspond with its presentation at the AHA meeting.

Reconsider the Guidelines

In an accompanying editorial[2], Dr Rudolph W Koster (Academic Medical Center, Amsterdam, the Netherlands) notes that, based on recent observational studies, the latest 2015 AHA guidelines include a new class IIb recommendation that "it may be reasonable for EMS to initiate resuscitation with three initial periods of 200 continuous chest compressions with passive oxygen insufflations." He adds that this recommendation was not made in the concurrent 2015 guidelines from the European Resuscitation Council.

Koster suggests that "if the results of the current ROC study had been available, the guidelines committee might have decided to retain the previous recommendation to give chest compressions interrupted for ventilations and perhaps even to upgrade that recommendation to a class IIa recommendation for EMS providers." He concludes with the question: "Should the AHA reconsider its recommendation?"

Commenting for heartwire , Dr Clifton W Callaway (University of Pittsburgh, PA) who was a coauthor of the new ROC randomized trial and a member of the AHA guidelines committee, said the new guidelines "do still recommend interrupted CPR with 30 compressions and then pausing for two breaths, but they also included a statement on continuous compressions, saying that this approach is not believed to be harmful and some groups may want to try it."

He added: "We included this statement on continuous chest compressions mainly because of work coming out of Arizona where they have adopted this approach, which has been associated with an impressive improvement in survival." But he pointed out that the Arizona approach is somewhat different from the technique evaluated in the ROC study. "In Arizona they are using continuous chest compressions together with passive ventilation (just covering face with a high-flow oxygen mask and letting the air infuse naturally with the chest compressions), whereas in the ROC study we evaluated continuous chest compressions with synchronous ventilation when the patient is actively given breaths by squeezing a bag."

Even so, Callaway says he thinks the guidelines do need to be updated urgently to incorporate the findings of the ROC trial.

"The problem with guidelines is that they have so far only been updated every 5 years or so. This situation shows that they really need to be updated much more regularly—as soon as significant new data are available—so that the best advice is available to healthcare providers as soon as possible. I really hope that if the new data from the ROC trial stand up to public scrutiny over the next few months the guidelines will be adjusted to include it as quickly as possible. I'm excited, as this is something of a test case."

ROC Study

For the ROC study, which included 114 EMS agencies, 23,711 adults with non–trauma-related cardiac arrest who were treated by EMS providers were randomized to continuous chest compressions (intervention group) or interrupted chest compressions (control group). The primary outcome—the rate of survival to hospital discharge—was 9.0% in the intervention group and 9.7% in the control group (P=0.07).

Survival with a favorable neurological outcome (modified Rankin scale score of ≤3) occurred in 7.0% of the patients in the intervention group and 7.7% of those in the control group (P=0.09).

Hospital-free survival—defined as the number of days alive and out of hospital in the first month after cardiac arrest—was significantly lower in the intervention group than in the control group (mean difference −0.2 days; P=0.004).

Nichol said these results "reinforce the need to continue with the practice of pausing compressions and giving rescue breaths with a bag."

But he cautioned that the present data apply only to the situation where emergency services are administering CPR and are giving oxygen with a bag and a mask. "The results cannot be extrapolated to bystander CPR, where continuous chest compressions are the current recommendation unless the person performing CPR is trained and willing to do ventilation. Our trial cannot inform that debate."

Asked what mechanism might be behind the results, Nichol said: "It might be that ventilation/oxygenation is more important than we thought. Although those given continuous chest compressions were also ventilated, you cannot deliver as much oxygen per breath when the chest is being compressed continuously."

He concluded: "These results are very new. I recommend that providers consider giving chest compressions with pauses for ventilation until we better understand what we have observed here."

The ROC trial was supported by the National Heart, Lung, and Blood Institute; the US Army Medical Research and Materiel Command; the Canadian Institutes of Health Research; Institute of Circulatory and Respiratory Health; Defence Research and Development Canada; the Heart and Stroke Foundation of Canada; and the American Heart Association. The Medic One Foundation provided salary support to Nichol, who also received grants from the National Heart, Lung, and Blood Institute; Food and Drug Administration; Zoll Medical; Cardiac Science; HeartSine Technologies; Philips Care; Physio Control; Neuroprotexeon; and Sotera Wireless and nonfinancial support from Abiomed. Disclosures for the coauthors are listed on the journal website.