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Dr. Joseph Ornato presented the Public Access Defibrillation (PAD) study, which evaluated the efficacy of out-of-hospital cardiac arrest treatment by cardiopulmonary resuscitation (CPR) alone vs CPR plus use of an automatic external defibrillator (AED) performed by trained laypersons. Most of the study sites were nonresidential such as airports, casinos, and shopping centers, but 15% were large, multiunit residential buildings with common areas where the AEDs were placed. Instead of randomizing patients to one treatment or the other, the various centers were randomly assigned one therapy or the other. There were 20-70 AED units in each of 24 communities with a total volume of about 20,000 cardiac arrests over 20 months. In order to qualify for the study each unit had to have a time to defibrillation (AED arm) of < 15 min 90% of the time. Each presumed cardiac arrest was reviewed by a blinded committee to be sure ventricular fibrillation, ventricular tachycardia, or asystole with no pulse was present. The primary end point was the number of survivors to hospital discharge. The secondary analysis included a comparison of efficacy at public vs residential places. The patient demographics were similar between the 2 treatment strategies. CPR alone resulted in 15 survivors vs 29 with CPR plus AED (P = .04). Also, the results were much better in public places as compared to residential units.
No adverse effects of defibrillation were observed. The investigators concluded that 1) trained laypeople can safely use AEDs; 2) survival is twice as good when AED is added to CPR; and 3) survival in multiunit residential areas is very low. The implication of the study is that community AED stations with trained volunteers should be developed.
Comment by Michael H. Crawford, MD
This is an interesting study in that survival rates were not calculated because the investigators believed that the denominator could not be accurately determined. They knew how many patients were treated, but believed that they had inadequate data to classify them appropriately. For example, if a patient was found in a pool and successfully resuscitated it might be classified as a cardiac arrest, but if the resuscitation effort was unsuccessful it might be classified as a drowning. Thus, only the number of survivors was counted between centers that had roughly the same number of arrests in aggregate. Also, instead of randomizing cases, they believed that it would be more acceptable to the volunteer workers to randomize units, so each unit could strive to do the best job with their strategy. In addition, these were all trained laypeople; all public employees with any medical training (eg, police officers) were excluded from participating. One limitation of the study was a lack of knowledge of the cause of cardiac arrest in the non-AED unit patients since ECGs were not done in these units. Studies from emergency medical units show that about 50% of cardiac arrest patients are not in VT or VF and presumably would not benefit from an AED. Also, other studies have shown that the incidence of VT/VF in cardiac arrest victims is declining for reasons that are not completely clear but may have to do with current therapy of heart disease patients. Despite these limitations, this is a landmark study that clearly demonstrates that trained laypersons can effectively operate an AED and make a difference in survival.
Dr. Crawford, Professor of Medicine and Associate Chief of Cardiology for Clinical Programs at the University of California, San Francisco, is Editor of Clinical Cardiology Alert.