IEEE Spectrum March, 2012 - 34

NA * iEEE SpEctrum * mArch 2012

phy. William Maisel, deputy director for science at
the FDA, explains: "Fix on fail means identifying and
trending problems on a case-by-case basis, repairing
individual devices rather than communicating the
problem to all users. In one example, a firm tracked
hundreds of complaints tied to a known defect. They
serviced each device when it failed but did not systemically notify other users so that their devices
could proactively be evaluated and repaired."

How did the AED industry get into this state? It
has to do with a quirk in the law regulating medical devices. If you count AEDs as Class III devices-
those intended to support and sustain life-then
manufacturers must produce extensive efficacy,
safety, and reliability data, usually provided by
large-scale clinical trials. This process can cost
upward of US $800 000 and take two years.
Manufacturers can, however, get around those
requirements, thanks to what's called the 510(k) process, which effectively removes AEDs from Class III.
The process requires merely that a new AED be "substantially equivalent" to any Continued on page 57
spectrum.ieee.org

photographer: dan saelinger; prop stylist: ariana salvato

The FDA discovered that manufacturers had evaluated barely a third of the
malfunctions and had identified the problem in only a third of those cases. Some
90 percent of the failures were thus unexplained. Worse, because the manufacturers had declined to reveal their sales
volume to the FDA, the agency couldn't
nail down the rate of malfunction or tell
whether it had risen over time.
"I was stunned to hear this," says
E. Magnus Ohman, a physician on the
FDA's oversight panel for AEDs. "We're
in the era of transparency. If I go to a restaurant, I get the hygiene rating." Another
physician on the panel, Frank LoGerfo,
complains, "If these devices can selfreport after an incident, it's almost inexplicable that we don't have very detailed
data for each device where it failed."
Eventually, the agency set its own engineers to work on the job. "We found some
pretty egregious design errors," says Al
Taylor of the FDA's Office of Science and
Engineering Laboratories. "There were
many situations where deficient product design and-let's put it bluntly-poor
engineering were a cause or a contributory factor to an adverse event."
One AED, the brand name of which
the FDA would not disclose, was found
to occasionally misdiagnose the heart's
electrical rhythm. It delivered some
shocks that weren't needed and failed
to deliver others that were. The culprit was a resistor that could vary in resistance by up to 10 percent of
its stated value. "When our engineer looked at this design, it was an
instant 'uh-oh,' " says Taylor. "We would have to do analysis to decide if
it needed a 1 percent or a 0.1 percent resistor, but this was clearly off the
scale." The reason? Only at that higher tolerance can the noise-canceling
circuitry isolate the cardiac signal from environmental sources of radiation, such as the oscillating electric fields of fluorescent tubes.
In another device, a voltage-monitoring circuit drew power from the
very source that it was checking. Because of this, a momentary drop
in voltage would cause a false signal to shut down the AED, and the
device would be unable to deliver a shock. Still another recalled AED-
made by MRL, of Buffalo Grove, Ill.-would work perfectly until somebody dropped it. The impact could cause a circuit board connector to
perforate an insulation shield, creating a short circuit and generating
RF interference that would prevent analysis of the patient's arrhythmia. Again, the unit would not deliver a shock.
The companies put some of the blame on a manufacturing environment they say has become increasingly globalized in the past
15 years. "Most of the risk today is in the supplied material, the commercial off-the-shelf components; these are the components that go in
your iPhones and your laptops, and we don't control their specification," says Brian Webster, president of Physio-Control, a division of
Medtronic. "We're prisoners of that supply chain."
Beyond failures in design and purchasing control, the FDA found
that many AED manufacturers were practicing a "fix on fail" philoso-

http://spectrum.ieee.org

Table of Contents for the Digital Edition of IEEE Spectrum March, 2012