Increasing Chest Compressions During CPR Saves More Lives

The survival rate in cardiac arrest patients undergoing cardiopulmonary resuscitation (CPR) increases when the chest compression fraction (CCF) is higher, according to a new review of studies.

Researchers at the University of British Columbia (Vancouver, Canada) analyzed data from 78 emergency medical services (EMS) agencies in seven locations that were part of the Resuscitation Outcomes Consortium (ROC), a group of 11 regional clinical centers in Canada and the United States that study promising out-of-hospital therapies for cardiac arrest and traumatic injury. The patients included in the study were those that had ventricular fibrillation or pulseless ventricular tachycardia cardiac arrest prior to EMS arrival between December 2005 and March 2007.

The researchers found that in the 506 cases analyzed, a return to spontaneous circulation was achieved 58% of the time when the CCF was 0-20%, and up to 79% when the CCF was 81%-100%. Survival to hospital discharge occurred in 12% of patients when CCF was 0%-20%, but increased to nearly 29% when CCF was 61%-81%, dropping slightly to 25% when CCF was 81%-100% CCF. The researchers speculate that the slight drop in survival in the group with the highest CCF rate was likely due to the small sample size of the study and wide confidence limits, although they acknowledge the possibility of a plateau effect when CCF is above 80%. The study was published in the September 14, 2009, issue of Circulation.

"Chest compressions move blood with oxygen to the heart and the brain to save the brain and prepare the heart to start up its own rhythm when a shock is delivered with a defibrillator,” said lead author Jim Christenson, M.D., a clinical professor of emergency medicine at the UBC. "We found that even short pauses in chest compressions were quite detrimental.”

Prior to 2005, interruptions to chest compressions for mouth-to-mouth breathing resulted in less than 50% of total CPR time being spent on chest compressions. However, the 2005 American Heart Association (AHA) guidelines for CPR and emergency cardiovascular care emphasized the importance of minimizing interruptions in chest compressions. This resulted in some EMS agencies achieving a CCF between 60%-85%.

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