Medical Studies Focus on CPR Effectiveness

Two new medical studies found that bystanders of a stranger’s cardiac arrest incident are more likely to perform CPR if it’s compressions-only, and doesn’t include rescue breathing. But the years-long U.S. and Sweden studies also concluded that there’s very little difference in the survival rates between the two emergency procedures. Even so, the American Hearth Association (AHA) reports that any CPR provided by bystander can double or triple a victim’s chance of survival, and says it trains 12 million people a year in CPR. The studies were published today in the New England Journal of Medicine, and were based on carefully-crafted study procedures that were performed by dispatchers at the London (UK) Ambulance Service, in Thurston and King Counties (Wash.), and at 18 comm centers in Sweden.

In the first study, 911/999 callers were randomly given emergency medical instructions in 1,941 incidents—provide compressions only or provide compressions and rescue breathing. The study tracked the survival rate of the patients and found that 12.5 percent survived with compressions-only, and 11.0 percent survived with compressions and rescue breathing, which the researchers deemed as not a significant difference. However, this study did find that certain study sub-groups had “a trend toward better outcomes” with the compressions/rescue breathing procedure. In the second study, researchers in Sweden came to the same conclusion—that there was “no significant difference in survival” between the two methods of resuscitation for out-of-hospital victims of cardiac arrest, and before EMS units arrive. Compression-only patient survival was 8.7 percent, the study found, while compression/rescue breathing patient survival was 7.0 percent.

The first study was conducted in Washington and London, and covered 5,525 incidents from April 2004 to April 2009. Callers were questioned by the dispatchers to determine if the patient was eligible for the study, and then opened envelopes with randomized instructions to give to the caller. Because of varying incident conditions and procedures, the study ended up with 981 compression-only patients and 960 compression/rescue breathing patients for the final analysis. In this study, “survive” was defined as hospital discharge.

The second study was conducted in Sweden, and followed a similar procedure. It included 3,809 incidents from February 2005 to January 2009. The final analysis covered 620 compression-only patients and 656 compression/rescue breathing patients, and used 30-days as the “survive” goal.

The new studies cited previous research that bystanders are more likely to assist if the instructions are for compressions-only: 80.5 percent compared to 72.7 percent if rescue breathing was also instructed.

The studies also cited previous research that rescue breathing should optimally take just 1.5 to 2 seconds for each of the two recommended breaths by a bystander, after each cycle of 15 chest compressions. However, studies of untrained, layperson CPR shows that it takes them an average of 16 seconds to provide the two breaths, significantly interrupting the chest compression procedure.

Ironically, the AHA changed its recommendation for CPR during the Sweden study to emphasize chest compressions. The researchers didn’t change their procedures since the European medical council did not immediately adopt the AHA’s new procedures.

The two studies are available for a fee at the Journal’s Web site.