More evidence points to the benefit of chest compression-only cardiopulmonary resuscitation (CPR) performed by bystanders being advised by emergency medical services' (EMS) dispatchers, rather than including rescue breathing as well, according to a study published online Oct. 14 in the Lancet.
Michael Hüpfl, MD, Medical University of Vienna in Austria, and colleagues conducted a primary meta-analysis of three trials in which more than 3,000 patients suffering an out-of-hospital cardiac arrest were randomly allocated to receive one of the two CPR techniques, according to dispatcher instructions.
A secondary meta-analysis included observational cohort studies of CPR.
The results of the primary meta-analysis showed that chest compression-only CPR was associated with improved chance of survival compared with standard CPR, which includes rescue breathing (14 vs. 12 percent, with the relative chances of survival increasing by 22 percent with chest-compression only CPR). The absolute increase in survival was 2 to 4 percent, or one life would be saved for every 41 patients treated with the chest compression-only method.
In the secondary meta-analysis of seven observational cohort studies, no difference was recorded between the two CPR techniques, with both groups recording survival rates of 8 percent. However, this second group of studies did not cover dispatcher-assisted CPR; rather they were based on bystanders who had decided on their own whether to do chest compression-only CPR or chest compression plus mouth-to-mouth.
The authors noted that in the primary meta-analysis, none of the three trials involved on its own showed a statistically significant difference in the two techniques, probably due to insufficient statistical power. The three had to be combined for the results to gain statistical significance.
"The fact that only three randomized trials have been done is testament to the difficulties associated with well designed prospective studies in this setting, such as obtaining of informed consent, the little time available to randomize patients, adherence to the study protocol, tracking of patients and outcomes, and masking of investigators, study personnel, and patients from the allocated intervention. Because survival rates after out-of-hospital cardiac arrest are low and large treatment effects are unlikely, very large sample sizes are needed to show a significant survival benefit."
The authors said that continuous, uninterrupted chest compressions are vital for successful CPR. "By avoidance of rescue ventilations during CPR, which are often fairly time-consuming for lay bystanders, a continuous uninterrupted coronary perfusion pressure is maintained, which increases the probability of a successful outcome."
They concluded that further research is needed into whether unassisted and dispatcher-assisted bystander chest compression-only CPR provide similar survival benefits.
"How should the results of these meta-analyses affect practice?" asked Jerry P. Nolan, MD, from the Royal United Hospital NHS Trust in Bath, England, and Jasmeet Soar, MD, from Southmead Hospital in Bristol, England, in an accompanying Lancet editorial.
"Compression-only CPR has an important role in increasing the rate of bystander CPR by those who are untrained, who have only a minimum time for training, or who are unwilling or unable to provide rescue breathing," Nolan and Soar concluded.