Cardiopulmonary resuscitation (CPR) is traditionally defined as chest compressions plus ventilations. There has been very little fundamental change in the method or manner of CPR over the past 50 years, since it was first proposed by Kouwenhoven et al. Only relatively recently, however, have the fundamentals of the initial resuscitation been investigated. The need for chest compressions is unquestionable, but the need for mouth-to-mouth ventilations for cardiac arrest has been questioned. Two reports in a recent issue of The New England Journal of Medicine , 1 by Svensson et al from Sweden and the other by Rea et al from Washington, describe the first prospective, randomized trials comparing compression-only CPR to standard CPR for out-of-hospital cardiac arrest (OHCA). These studies took advantage of emergency medical dispatchers’ instructing bystanders to administer CPR to patients with OHCA, who were randomly assigned to undergo 1 of 2 types of CPR.

Svensson et al found no significant difference in outcomes between standard CPR and compression-only CPR for OHCA. Similarly, Rea et al reported no difference in survival or favorable neurologic outcomes. Multiple previous studies have also failed to demonstrate any significant difference, likely because of a lack of statistical power. However, these 2 studies add significant evidence and knowledge to our understanding of differential effects of CPR with and without rescue breathing on outcomes of cause-specific OHCA. Combining the results of these 2 randomized trials, survival to hospital discharge (176 of 1,260 vs 149 of 1,253, p = 0.12), although not reaching conventional significance levels, showed a trend favoring compression-only CPR. This means an absolute difference of 2%, translating into 20 additional survivors per 1,000 OHCA victims. Rea et al also showed similar calculations for favorable neurologic outcomes: 144 survivors per 1,000 patients with compression-only CPR compared to 115 per 1,000 with standard CPR, a difference of 29 per 1,000 patients, suggesting that not only there will be more survivors but also more survivors with favorable neurologic outcomes (29 of 1,000 vs 20 of 1,000). Given that OHCA claims hundreds of thousands of lives each year worldwide, this would have a tremendous clinical impact.

The aim of CPR is not only survival but survival with a favorable neurologic outcome, and the optimal outcome measures in such studies should incorporate heart and brain resuscitation. Although Rea et al focused on their finding of a trend favoring compression-only CPR for survival at hospital discharge (p = 0.09) in OHCA of cardiac origin, it would have been more appropriate to highlight and emphasize the fact that a significantly higher number had favorable neurologic outcomes at discharge (18.9% vs 13.5%, p = 0.03) in the same subgroup. Although this study was underpowered to evaluate any significant difference in survival for all-cause OHCA or even for OHCA of cardiac origin, it did demonstrate this important outcome, strongly favoring compression-only CPR. Rescue breathing has been shown to decrease coronary and cerebral blood flow by excessive interruption of compression-generated blood flow and by decreasing venous return to the chest. Given the higher magnitude of benefit for favorable neurologic outcomes compared to survival alone (5.4 vs 4.3%), it is plausible, as suggested Rea et al, that the brain may derive specific benefit from compression-only CPR.

These studies also demonstrate the important contribution a well-trained, assertive emergency dispatch program can make to increase bystander CPR, and future efforts should concentrate on this to save more lives.