Hostler D, Everson-Stewart S, Rea TD, et al. Effect of real-time feedback during cardiopulmonary resuscitation outside hospital: Prospective, cluster-randomised trial. BMJ 342: d512, Feb 4, 2011.
The objective was to investigate whether real-time audio and visual feedback during CPR increased the proportion of subjects who achieved prehospital return of spontaneous circulation.
Design—A cluster-randomized trial.
Subjects—1,586 people having cardiac arrest outside the hospital in whom resuscitation was attempted by emergency medical services (771 procedures without feedback, 815 with feedback).
Setting—EMS from three sites within the Resuscitation Outcomes Consortium in the United States and Canada.
Intervention—Real-time audio and visual feedback on CPR provided by the monitor-defibrillator.
Results—Baseline patient and emergency medical service characteristics did not differ between groups. EMS muted the audible feedback in 14% of cases during the period with feedback. Compared with CPR clusters lacking feedback, clusters assigned to feedback were associated with increased proportion of time in which chest compressions were provided (64% v. 66%), increased compression depth (38 v. 40 mm) and decreased proportion of compressions with incomplete release (15% v. 10%). However, frequency of prehospital return of spontaneous circulation did not differ according to feedback status (45% v. 44%), nor did the presence of a pulse at hospital arrival (32% v. 32%), survival to discharge (12% v. 11%) or awake [status] at hospital discharge (10% v 10%).
Conclusions—Real-time visual and audible feedback during CPR altered performance to more closely conform with guidelines. However, these changes in CPR performance were not associated with improvements in return of spontaneous circulation or other clinical outcomes.
The results of this large and well-designed study raise an obvious question: If feedback improves CPR quality and better CPR increases survival, then why didn’t more patients survive? There are at least five reasons:
First, the improvement in CPR here was, at best, minimal. Improving depth by 2 mm (less than 1/8 inch) or increasing the time on the chest by 2% (64% to 66%) may be a statistical “improvement,” but cannot reasonably be expected to improve patient care.
Second, even with feedback the CPR was of marginal quality. The mean compression depth was 40 mm (the lower limit of the AHA-recommended range of 40–50 mm), so half were too shallow.
Third, even with feedback, more than a third of the time, there were no chest compressions at all—long intervals that have been shown to dramatically reduce circulation.
Fourth, no feedback was provided for ventilations, and if they were of similar marginal quality, that would further worsen performance.
And finally, the feedback was only provided to those responders with the device, and only after it was attached and running. Family, bystanders, first responders and EMS personnel before the device was operational—those providing CPR during the critical first few minutes of the resuscitation—had no feedback. Given all these limitations, it is no surprise patient outcomes did not improve.
The place for real-time feedback is during training. We learn how to start IVs and intubate before those skills are needed in an emergency. A better approach here would be to properly train (and retrain at appropriate intervals) all responding personnel (and as many community members as possible) in CPR. Real-time feedback during training will allow individuals the time and repetition to actually acquire the skills needed to perform high quality CPR—immediately, consistently and continuously. The point-of-care devices could then be used to monitor and, perhaps even more important, provide data that could be used to improve subsequent training.