During cardiac arrest, the heart stops beating and cannot pump oxygen throughout the body. The goal of cardiopulmonary resuscitation (CPR) is to temporarily take over the function of the heart and pump blood through the body until further help arrives. Although the exact steps have changed over the years, CPR generally involves a cycle of chest compressions and mouth-to-mouth rescue breaths. To be most effective, CPR needs to be started immediately. Unfortunately, bystanders are often reluctant to start CPR because they are unsure of what to do or are unwilling to place their mouth over a stranger's mouth. In 2008, the American Heart Association introduced chest compression-only CPR without rescue breathing to decrease bystander reluctance to participate. Experts who develop CPR guidelines regularly review outcomes of CPR attempts.
Researchers in Seattle and Sweden compared the effectiveness of compression-only CPR to standard CPR by bystanders. The studies, published in the New England Journal of Medicine, found there was no significant difference in survival rates for people who received compression-only CPR when compared to traditional CPR.
About the studies
Two randomized control trials were completed in Seattle, Washington and in Sweden. There were 1,276 heart attack patients included in the Sweden trial and 1,941 patients included in the Seattle trial. Both trials had CPR instructions delivered through specially trained medical dispatchers. The dispatcher determined if each call qualified as sudden cardiac arrest, then chose a sealed envelope that randomly contained instructions for either standard CPR instructions with cycles of breathing and compression or compression-only instructions. Calls that included severe injury or trauma were not eligible. Qualifying calls also had bystanders with no previous CPR experience who were willing to carry out the instructions. The individual studies both examined survival rates but at different points in recovery:
- Seattle survival rates
- Survival to hospital discharge was 12.5% in compression-only compared to 11% in standard CPR
- Survival to discharge without significant brain damage was 14.4% in compression-only compared to 11.5% in standard CPR
- Sweden survival rates
- 1-day survival rate was 24% in compression-only compared to 20.9% in standard CPR
- 30-day survival rate was 8.7% in compression-only compared to 7% in standard CPR
There was no statistically significant difference between the groups at any survival point. Although more instructions were given out, only 33%-35% of calls qualified for inclusion in these studies. The final numbers in both studies were lower than the study had planned for statistical significance.
How does this affect you?
When studies are designed, there are guidelines set for the number of participants needed to prove the theory of the study. These studies fell short of the numbers needed, which decreases the reliability of these results. However, previous studies and medical theory still support the belief that compression-only CPR may be as effective as traditional CPR. In addition, removing mouth-to-mouth resuscitation from CPR may encourage more people to act quickly, which in itself may increase survival rate.
Interest has been growing on the effects of compression-only CPR. The American Heart Association provides instructions for and has promoted the use of compression-only CPR. Look for CPR classes in your community so that you know how to identify and act if someone has cardiac arrest. Many people are intimidated from doing CPR because they are worried about causing harm, but bystander inaction is more harmful. If you see someone you suspect to be in cardiac arrest, call 911 and be ready to give chest compressions.
Last reviewed August 2010 by Brian P. Randall, MD
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