Within two minutes of cardiac arrest, approximately two thirds of patients develop ventricular fibrillation, but the rhythm becomes increasingly refractory to defibrillation over time. The provision of automated defibrillators in public places is increasingly advocated as a means of improving survival after cardiac arrest, but the relative benefit of this strategy is unclear. Pell and colleagues used Scottish data concerning all nonhospital cardiac arrests to estimate the potential increase in overall survival that could be achieved with public access to defibrillators.

They studied all nonhospital cardiac arrests occurring in Scotland during 1991 through 1998. Patients were excluded if cardiac arrest occurred in a medical facility or ambulance. For each incident, the location and time for emergency personnel to arrive was recorded, as well as information about any attempted defibrillation and survival. Locations were classified as suitable for a public access defibrillator (e.g., sports stadium or shopping mall), possibly suitable (e.g., train), and unsuitable (e.g., private homes).

Of the 15,189 arrests occurring during the study period, 12,004 (79 percent) occurred in sites unsuitable for public access defibrillators. Most of them occurred in private homes. Only 2,732 (18 percent) happened at sites, such as airports, businesses, or shopping centers, that were suitable for defibrillator placement. The remaining 453 (3 percent) occurred at possible sites, such as buses or parking lots. Patients who went into cardiac arrest at suitable sites had a higher baseline survival rate (8.7 percent compared with 4.5 percent for possible sites and 4.2 percent for unsuitable sites). Regardless of the site, patients who received attention within three minutes were more likely to receive defibrillation (70 percent compared with 58 percent of those with longer delay). Applying statistical models to the data, the researchers estimate that public access defibrillators at suitable sites would increase the number of survivors from 744 to 942 (6.2 percent of total arrests). Increasing the availability of defibrillators to all possible sites would only increase the number of survivors to 959 (6.3 percent).

The authors conclude that because most cardiac arrests occur in private homes, widespread use of public access defibrillators is likely to improve only modestly survival, from about 5 to 6.3 percent. They argue that strategies such as enhanced response by professionals and public education about cardiopulmonary resuscitation are more likely to improve survival.

editor's note: To optimize your chances of surviving cardiac arrest, do it in the midst of a crowd containing at least a couple of people who are proficient in cardiopulmonary resuscitation and someone with the presence of mind to summon professional help. Defibrillators operated by trained personnel have been beneficial in certain public locations, including sports facilities and casinos, but the outcome in open public areas is much less certain. This study concludes that the machines will benefit only a lucky few, and we have no concept yet of relative harms and costs. Realistically, this debate has already moved beyond the reach of evidence-based medicine and is becoming a crusade. The drama of saving those few lives and a sense of community duty (or pride?) has led to demands and fund-raising campaigns. At one extreme, we should be joyful about every life saved, but this effort seems bizarre when an increasing number of persons lack even basic health care and untold others find medical care compromised by increasing costs or inaccessible services.—a.d.w.