Lifesavers though they are, portable, heart-shocking defibrillators are not fail-safe.
Like any machine, automated external defibrillators, or AEDs, need to be maintained. Batteries run down and need to be replaced. Electrode pads that attach to a patient's chest also deteriorate and have to be replaced every year or so. Circuitry can fail. And maintenance can be spotty.
The U.S. Food and Drug Administration has received more than 45,000 reports of "adverse events" associated with failure of AEDs between 2005 and 2012, although only some of the events involved the fully automated devices put in public areas. The others were defibrillators limited to medical use. Manufacturers also conducted more than 80 recalls during the seven-year period.
The number of AEDs sold in the U.S. has been rising steadily, from around 100,000 a year in 2010 to between 500,000 and 1 million this year, according to the Sudden Cardiac Arrest Foundation and industry officials. There are about 2.5 million deployed.
"Survival from cardiac arrest depends on the reliable operation of AEDs,'' said Dr. Lawrence DeLuca, a professor of emergency medicine at the University of Arizona in Tucson.
He led a 2011 review of more than 40,000 AED malfunctions reported to the FDA between 1993 and 2008. The analysis found that 1,150 deaths occurred during those failures.
No one knows exactly how often someone attempts to use an AED, but with an average survival rate of 2 percent to 4 percent from sudden cardiac arrest outside a hospital, according to studies, the devices help save roughly 3,500 to 7,000 lives each year, although not all of the rescues are performed by untrained bystanders. If AEDs were more widely available, the number of saved lives could triple or more, experts say.
"AEDs can truly be lifesavers, but only if they are in good working order and people are willing to use them,'' said DeLuca, who had a personal experience with batteries failing on a device when he was trying to revive a fellow guest at a resort in 2008. It took nine minutes to retrieve a second AED, which did work. The patient was not revived.
Problems with pads, cables and batteries accounted for nearly half the failures -- mistakes that could have been due to poor maintenance. Forty-five percent of failures linked to fatalities occurred when the device was attempting to charge (power up) and deliver a recommended shock to someone in cardiac arrest, DeLuca said.
For example, in Washington, D.C., there have been at least two sudden-cardiac-arrest deaths -- one in a gym in 2011, one in a Metro subway station in 2012 -- that occurred after AEDs failed to work due to dead batteries.
But there also were incidents reported to the FDA when the devices shut down without analyzing a patient's heart rhythm. Regulators and watchdogs believe some victims were not revived when the machines failed, but it's difficult to say whether any particular patient would have had heartbeat restored.
According to the FDA, in one case, a nurse was trying to hook up a defibrillator to a patient when the screen read "memory full" and shut down. In another, a software defect caused the machine to flash an "equipment disabled" message.
The FDA said the most common malfunction reports involved design flaws and manufacturing of the devices using poor-quality parts such as capacitors and software.
In addition, FDA officials noted several recent studies that found location and ownership of AEDs is so poorly documented in many areas, and machines are often locked away and forgotten, that they may not be maintained properly or repaired in the event of a recall.
Manufacturers insist they work hard to know where the devices are using their own sales records, but government accounting for AEDs at the state or local level is incomplete at best. Many states don’t require the devices to be registered.
AED failures have raised enough concern that the FDA is ending the medium-risk status that AEDs have had since they first became widespread more than 20 years ago. Basically, defibrillators were grandfathered in because similar devices had been around before the FDA changed its rules for medical gear.
Now, they'll be classified high-risk equipment that reflects their use to support and sustain human life -- and their greatly increased sophistication over the years. Manufacturers will have to provide more safety evidence and FDA inspectors will be allowed to inspect plants where parts are made.
The tighter rules don't mean the public should lack confidence in the lifesaving devices. Dr. William Meisel, the FDA's chief scientist for devices, stressed the essential role AEDs play when he announced the new rules in March.
"These devices are critically important and serve a very important public-health need," Meisel said, noting that none were being taken out of service beyond the recalls manufacturers have already issued. "Patients and the public should have confidence in these devices and we encourage people to