Continuous Cardiac Compressions Come Under Scrutiny

Several years ago studies out of Arizona and Wisconsin trumpeted continuous cardiac compressions, known as CCC or sometimes known as CCR (cardiocerebral resuscitation), as offering increased survival for out of hospital cardiac arrest. Neurologically intact survival from witnessed vfib arrests increased by 250-300%. For the first several cycles of CPR stop compressions only to shock, insert an oral airway and apply a nonrebreather, ventilate passively. It made sense. You had to keep the heart perfused and avoid hyperventilation. CCR has spread across the country like wildfire. Here in Connecticut, we have made it our statewide standard for all arrests of suspected cardiac origin. The AHA ignored CCR in 2010 and in the just released 2015 Guidelines offered tepid support for it, giving it a IIb recommendation. (A IIb recommendation means the evidence is WEAK, but it may be reasonable to practice the method. A IIa recommendation means MODERATE evidence, is reasonable to do. A Level I recommendation is STRONG evidence, is recommended.)

2015 (New): For witnessed OHCA with a shockable rhythm, it may be reasonable for EMS systems with priority based, multitiered response to delay positive-pressure ventilation (PPV) by using a strategy of up to 3 cycles of 200 continuous compressions with passive oxygen insufflation and airway adjuncts.

Yesterday, the New England Journal of Medicine published a major study, Trial of Continuous or Interrupted Chest Compressions during CPR, the result of a major randomized controlled study comparing CCC with standard CPR. The results not only showed continuous chest compressions without pause for ventilations did not improve outcome, these patients did slightly worse. Now, it is important to note they did not compare true CCR, with passive ventilation, with standard CPR. They compared continuous cardiac compressions with positive ventilation with standard CPR, compressions with pauses for ventilation. Are perhaps the positive pressure ventilations the villian?

12,653 patient received continuous compressions versus 11,0587 getting tradition CPR. 9% of the patients survived to discharge in the continuous compression group versus 9.7% in the standard group, a difference considered not statistically significant. No small study here. Both groups had very high chest compression rates . The new AHA guidelines recommend a compression fraction of .60. Here the CCC group was .83 and the traditional group was .77. The fraction means amount of time per minute compressions are being performed.

An accompany editorial Continuous or Interrupted Chest Compressions for Cardiac Arrest, concludes: “The new 2015 AHA resuscitation guidelines were published only recently. 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. Should the AHA reconsider their recommendation?

The AHA has put an end to its five year cycle of updates so they can update the recommendations more rapidly to take into account the best and latest scientific evidence. It will be curious to see what happens here. I think we also need to allow some time for other people to review this study for any methodological errors. Give it the closest scrutiny.

A final thought. We must applaud this study and the rigorous debate that should surround it. We have to believe first in science, not in anecdote, theory or wishful thinking. Over the years how many next best things have bitten the dust when finally studied properly? How many things are we doing now that may be harmful? That if only properly studied we would end their practice? So hats off to science, and evidenced based debate. We in EMS should welcome them to town.

References:

Trial of Continuous or Interrupted Chest Compressions during CPR

Minimally interrupted cardiac resuscitation by emergency medical services for out-of-hospital cardiac arrest.

Highlights of the 2015 American Heart Association Guidelines Update for CPR and ECG

Continuous or Interrupted Chest Compressions for Cardiac Arrest

9 Comments

  • Christopher says:

    “…these patients did slightly worse.”

    No. Per the study, when you adjusted for witnessed VF/VT arrest, they did just as well as the “standard” group.

  • medicscribe says:

    From the study:

    In the per-protocol analyses, patients who received continuous chest compressions had significantly lower survival rates than those who received compressions with interruptions.

    From the accompanying editorial:

    A prespecified per-protocol analysis that was based on strict adherence to the treatment algorithm showed significantly lower rates of survival among patients in the intervention group than among those in the control group (7.6% vs. 9.6%).

    In the final analysis, the difference was not considered statictically significant, which I noted in my post:

    2,653 patient received continuous compressions versus 11,0587 getting tradition CPR. 9% of the patients survived to discharge in the continuous compression group versus 9.7% in the standard group, a difference considered not statistically significant.

  • Christopher says:

    They also had significantly fewer witnessed VF/VT arrests…which is a known cause of lower survival to discharge. I’m befuddled by this confounder not being placed in the abstract.

    “In this per-protocol population, the characteristics of the patients and characteristics of the EMS providers after treatment were imbalanced, with significantly higher rates of a shockable rhythm and prehospital intubation in the control group than in the intervention group (Table S2 in the Supplementary Appendix).”

    Nobody can take a confounder that significant and expect to evaluate such a small difference in outcomes to be “significant”.

  • medicscribe says:

    Thanks as always for your thoughful comments, Christopher. Best, Peter

  • Kit says:

    The initial studies on CCR that did reflect markedly increased survival rates allowed only for passive ventilation.
    So – I’m confused on two points.
    Why were the changes in procedure altered to include pressure ventilation??
    Why are we still asking whether pressure ventilation ‘might’ be the villain after all?!?

  • medicscribe says:

    Good questions. It will be interesting to see more learned commentaries from EMS experts after they have reviewed this study. I would hope that more studies looking just at passive ventilation could be done. The original studies consluded randomized controlled studies were needed to test the early results. Hopefully they will be forthcoming.

  • mpatk says:

    “Now, it is important to note they did not compare true CCR, with passive ventilation, with standard CPR. They compared continuous cardiac compressions with positive ventilation with standard CPR, compressions with pauses for ventilation. Are perhaps the positive pressure ventilations the villian?”

    That is the key question; and thank you for pointing it out. Though it is significant to note that the benefit from “uninterrupted CPR” does have limits.

  • Jake says:

    Well, now that we have good evidence that continuous chest compressions (CCC) with positive pressure ventilations (PPV) are no better or worse than traditional CPR, we need a good large study of CCR (CCC w/ passive ventilation) vs CPR.

  • Mr. Ambulance Driver says:

    PC,
    I’m a high schooler, and I’m doing a research report on BLS v. ALS for cardiac arrest survival, and I was wondering if I could get your opinion on the matter, as well as some other related questions. If you’re not too busy and would like to, I can be contacted at brpate@student.linnmar.org

    Thanks,
    Ambulance Driver