Sept. 16, 2009 — Vigorous cardiopulmonary resuscitation (CPR) with more chest compressions on people with sudden cardiac arrest can improve the survival rate, a new study shows.
“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,” says study researcher Jim Christenson, MD, of the University of British Columbia. “We found that even short pauses in chest compressions were quite detrimental.”
Sudden cardiac arrest kills about 325,000 Americans a year, or 800 per day, and can occur without warning, as in the case of NBC newsman Tim Russert, who died in June 2008.
In sudden cardiac arrest, the heart suddenly stops pumping blood effectively to the brain and body, causing a person to collapse. The most common reason for sudden cardiac arrest is a very chaotic heart rhythm (ventricular fibrillation), which occurs as a result of a heart attack.
Rarely, ventricular fibrillation can occur without a heart attack but in the presence of an underlying structural heart abnormality — as is occasionally the case when a young athlete collapses and dies out of the blue. When sudden cardiac arrest occurs, death comes within a few minutes unless the victims’ heart muscles are successfully jolted back into a normal rhythm with an electrical shock.
CPR traditionally involves providing chest compressions to help circulate blood around the body and breathing support, such as mouth-to-mouth ventilation. Interruptions to chest compressions are common during CPR, with rescuers typically spending only 50% of their time giving chest compressions.
CPR Survival Rates
In the new study, published in Circulation: Journal of the American Heart Association, researchers analyzed data from 78 emergency medical services agencies to determine the effect of chest compressions on patient outcome. They specifically looked at something called the “chest compression fraction” (CCF), which refers to the percentage of time spent performing chest compressions relative to the entire time that CPR is performed.
In the 506 cases studied, a “return to spontaneous circulation” was achieved 58% of the time when the CCF was 0% to 20%, but rose to 79% when CCF was 81% to 100%. Return to spontaneous circulation means that the heart began to beat effectively again on its own.
Survival to hospital discharge occurred in 12% of patients with a CCF between 0% and 20%. Survival more than doubled to 29% when CCF increased to 61% to 81%, the researchers say. Survival rates fell slightly to 25% with CCF ratios greater than 81%.
“There was roughly a 10% increase in the chance of survival for every 10% increase in the chest compression fraction,” Christenson says.
According to the researchers, the slight drop in survival in people with the highest CCFs was likely due to the small sample size of the study. However, the possibility of a plateau effect in CCF exists.
Christenson says in a news release that more study is needed to determine the optimum time compressions are administered and when they are most important, such as just before or after delivery of an electrical shock. “We should continue chest compressions as much as possible, only pausing to do things that are proven to be medically beneficial.”
The main message to bystanders is that cardiac arrest is not necessarily a death sentence, but lives can be saved if more people learn CPR and how to deliver chest compressions.
“The chest compressions you do on a loved one are one of the most important things that can be done,” Christenson says. “If you feel rusty or are not confident giving mouth-to-mouth ventilation along with chest compressions, then just do chest compressions. Even by themselves, chest compressions can make a difference.”
The researchers write that sudden cardiac arrest is a leading cause of premature death around the world. They conclude that the public should be encouraged to learn CPR and to deliver chest compressions effectively.