More evidence of the primacy of chest compressions over ventilation in cardiopulmonary resuscitation

November 14, 2007 By Benjamin A. Olenchock, M.D. Ph.D. [mailto:bolenchock@partners.org]

Arizona

The 2005 AHA guidelines for cardiopulmonary resuscitation (CPR) changed the recommended ratio of chest compressions to ventilations from 15:2 to 30:2, based mostly on expert opinion that circulatory support is more critical than ventilatory support. Researchers at the University of Arizona have performed CPR on 64 domestic pigs which were randomized to receive either the recommended 30:2 CPR or continuous chest compression without ventilations. Their findings, published in the journal Circulation, suggest that continuous chest compressions might lead to improved outcomes.

The investigators used a temporary pacing wire to initiate ventricular fibrillation in anesthetized, intubated pigs. They allowed the non-perfusing rhythm to continue between 3 to 6 minutes and then initiated either continuous chest compressions or 30:2 compressions to breaths. At 12 minutes after initiation of ventricular fibrillation, a first 150 J biphasic shock was delivered, and then resuscitation was continued via advanced cardiac life support guidelines. The primary outcome measure was neurologically normal survival at 24-hours.

Although it was impossible to blind the providers, chest compressions were similarly effective between the two groups as measured by mean arterial pressure. The integrated coronary perfusion pressure, which is known to predict survival following cardiac arrest, was significantly increased in the continuous chest compression group (23 mm vs. 10 mm, p =0.001). Neurologically normal survival was also significantly increased in the continuous chest compression group (70% vs 42%, p=0.025). The benefit of continuous chest compression was greater for those pigs that had non-perfusing rhythms for 6 minutes than for those not perfusing for 2 minutes.

These findings stress the primacy of adequate chest compressions during CPR to maintain a perfusing blood pressure. They also bring to attention the problem of long breaks in chest compressions that occurs when rescuers deliver breaths. Whether this technique would translate into improved outcome in humans will be much more difficult to demonstrate. Perhaps future recommendations from the AHA will continue to move away from rescue breaths towards continuous chest compressions.


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