Both studies found that automated external defibrillators (AEDs) used on airplanes and in casinos in the United States were able to provide prompt attention to victims of cardiac arrest and improve their chances of survival.
Defibrillators were installed at some casinos in Nevada and Mississippi, and security officers were trained to use them.
"The security officers saved 56 lives in the 30 months of the study," said Dr. Terence D. Valenzuela, a professor of emergency medicine at the University of Arizona College of Medicine and lead author of the casino study.
The quick responses of security officers helped researchers learn just how quickly defibrillation needs to be applied.
"It appears, to get the best possible survival, it's required to shock a patient within three minutes of their collapse," Valenzuela said.
Valenzuela said the group found that individuals without previous medical training could be easily instructed to use the AEDs and that the study results were currently the best reported for cardiac arrest program not within a hospital.
Another group made similar findings. Cardiologist Dr. Richard L. Page, an associate professor of internal medicine at the University of Texas Southwestern Medical Center in Dallas, led a group that investigated the results of American Airlines' 1997 decision to install defibrillators on some airplanes.
Of 15 patients found to have ventricular fibrillation - the abnormal heart rhythm that prevents the heart from pumping blood - all 15 were successfully treated on the first shock and six patients were eventually discharged from the hospital with full functional capacity, Page said.
"Forty percent survival from sudden cardiac death - ventricular fibrillation - is higher than you can expect in most cities with ground-based transportation for emergency medical technicians," Page said.
In Chicago, about 1.8 percent of patients in cardiac arrest survive.
The group also found that the devices were safe and generally fool-proof. Frequently, Page said, the devices were set up to be used on people who had not actually suffered cardiac arrest and hadn't lost consciousness. In those cases, the AEDs detected that a shock would be inappropriate and did not discharge.
These findings may influence the future of access to AEDs, Page said.
"I can envision these AED devices being almost everywhere you go, such as in the case of a fire extinguisher," Page said.
Bystanders could operate the AEDs when a person goes into cardiac arrest, returning the heart to normal rhythm within minutes, he said.
"The chance of surviving ventricular fibrillation goes down 7 to 10 percent every minute after arrest takes place," Page said. "So, if you go 10 or 15 inutes, even with CPR your chance of survival is small, especially meaningful survival."
Valenzuela's casino study shows that when defibrillation begins within three minutes, the chance of survival is almost three out of four.
"So the bottom line is, you need to apply a defibrillator shock as soon as possible, and public access to defibrillation may well be the answer to the problem," Page said.
Dr. Rose Marie Robertson, of Vanderbilt University Medical Center in Nashville, Tenn., authored an editorial that appears in the Oct. 26 issue of the New England Journal of Medicine, where Valenzuela's and Page's studies appear.
Robertson noted that the four-step "chain of survival" for people having cardiovascular problems requires fast action. Early access to emergency medical services via 911 is the first step, followed by early cardiopulmonary resuscitation (CPR), early defibrillation and early advanced resuscitative care en route to the hospital.
The time needed to get defibrillators to the victims, when on-site units aren't available, was "a critical flaw in the system," Robertson wrote, so smaller, easy-to-operate devices were developed. The two new studies show that the technology is effective, easy to use and should be implemented in communities nationwide, she wrote in he paper.
In fact, Robertson and Page both cite a 1999 study on the ease of operating AEDs. Untrained sixth graders were able to follow the instructions and effectively operate defibrillators in a mock episode of cardiac arrest, taking only 27 seconds longer than emergency medical personnel.
By CBSHealthWatch Reporter Erin R. King
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