Two independent randomized controlled trials showed no statistically significant difference in survival in patients in cardiac arrest who received standard cardiopulmonary resuscitation (PCR) with chest compressions plus artificial respiration compared with chest compressions alone. Both studies concluded that CPR performed by a layperson is at least as effective with chest compressions alone compared with chest compressions plus artificial respiration, and is also easy to teach and perform. The two studies were published simultaneously in the July 29, 2010, issue of the New England Journal of Medicine. In 2008, the American Heart Association (AHA) introduced the concept of “CPR with chest compressions only” in a revision of CPR guidelines that had been in place for decades. Based on several animal and human studies, the AHA declared that chest compressions alone are an acceptable life-saving modality for people who are not routinely trained in CPR and who are unable or unwilling to perform artificial respiration in addition to chest compressions. The newly published results of the randomized controlled trial confirm and extend the findings of the previous study. Dispatchers from two counties in London and Washington State randomly dispatched either chest compressions alone or standard CPR instructions to 911 operators (999 in London). The study, led by Dr. Thomas D. Rea of the University of Washington in Seattle, ultimately included 1,941 patients, of whom 981 received chest compressions alone and 960 received chest compressions plus artificial respiration. Of these, 12.5% survived in the chest compressions group and 11.0% survived in the chest compressions plus artificial respiration group, with no significant difference between the two groups. Considering the possibility of differences in neurological sequelae between the two techniques, the investigators examined the proportion of surviving patients with better neurological function and found no significant differences in these indicators. Patients in the two groups approached (but did not reach) statistical differences in the following aspects: patients with cardiac arrest of cardiac origin who received chest compressions alone had a slightly higher survival discharge rate (15.5% versus 12.3%, P=0.09). In contrast, survival rates for patients with noncardiac causes of cardiac arrest who received chest compressions alone and those who received chest compressions plus artificial respiration were 5.0% and 7.2%, respectively, but this difference was far from statistically significant (P=0.29). In another new study, Swedish researchers then assigned 1,276 emergency call patients to 18 emergency medical dispatch centers, of whom 620 received chest compressions-only CPR and 656 received standard CPR. Dr. LeifSvensson of the Karolinska Institute in Stockholm and colleagues found that the chest compressions-only and standard CPR groups had 30-day survival rates. Several analyses between subgroups also did not find significant differences. In particular, no significant differences were found in patient survival in terms of age, interval between call for help and emergency medical services response, or interval between call for help and emergency cardioversion. Citing previous studies, Dr. Svensson and colleagues wrote, “Complete airway obstruction does not reduce the chance of survival if moderate circulation is provided by chest compressions.” They also noted that the findings demonstrate the difficulty of providing adequate ventilatory support through artificial ventilation by laypersons. Standard CPR guidelines call for 2 breaths after 15 chest compressions per group, with each breath lasting 1.5 to 2 s. In one study, however, untrained personnel took an average of 16 s to perform 2 artificial breaths during CPR. Dr. Svensson and colleagues write, “Overall, this study further supports the hypothesis that CPR with simple chest compressions, which is easy to learn and perform, should be the preferred method when the rescuer performs CPR on a patient in cardiac arrest.” The American and British study was a Laerdal Emergency Medicine Fund grant project, and both investigators acknowledged receiving funding from Philips Medical Systems and Company for defibrillators, among others, and disclosed that their study received funding from the Medtronic Foundation. The Swedes’ study was funded by the Stockholm County Council, SOSAlarm, and the Swedish Heart and Lung Foundation.