Constant Compressions Are Critical for Successful CPR

A new study shows that interrupting chest compressions during resuscitation reduces the chances of heartbeat return after defibrillation, and that for every second of a pause in compressions there is a 1% reduction in the likelihood of success.

Researchers from the University of Stavanger (Norway) used an electrocardiogram (ECG) database to analyze data from 911 interruptions and quantify the effect of compression interruptions on the probability of a return of spontaneous circulation (ROSC). The researchers identified 5,138 analysis windows without chest compressions that followed an interval with compressions, and noted where the patients had ventricular fibrillation or tachycardia. By calculating the mean-slope (a predictor of the return of spontaneous circulation) of the ECG for each 2-second window, and using a linear mixed-effects statistical model, the researchers quantified the decline of mean-slope over time.

The results showed that the probability of ROSC as estimated from the ECG decreases in a steady manner with increasing pre-shock pauses in chest compressions. Regardless of initial level, there is a relative decrease in the estimated probability of ROSC of about 23% from 3 to 27 seconds, or a 1% relative decrease for every second into such a pause. The study was published on February 6, 2009, in the open access journal BMC Medicine, a publication of BioMed Central.

"Every second without the blood perfusion generated by chest compressions has a negative impact on the estimated probability of ROSC,” said lead author Kenneth Gundersen, Ph.D., of the department of electrical and computing engineering. "The first priority when witnessing a cardiac arrest is to make an emergency call. Beyond this our results show that performing powerful chest compressions with minimal interruptions is of utmost importance. The quality of CPR matters and everyone should practice their CPR skills at regular intervals.”

The American Heart Association (AHA) first aid guidelines were updated in 2008, suggesting that the "mouth-to-mouth” component of CPR was unnecessary. This new research supports that position, in that the pause in compressions required to perform artificial respiration may reduce the patient's chances of recovering their heartbeat.

Related Links:
University of Stavanger
BioMed Central