IEEE Spectrum November, 2008 - 30

passing minute, which doesn't bode
well for your coworker. You remember seeing an AED hanging on a wall
nearby, and you dash off to retrieve
it. Defibrillator in hand, you struggle
to keep cool as you try to recall how
this strange device works. You're
under immense time pressure in an
unfamiliar situation where every second counts.
Luckily for your colleague, the
rest of your actions couldn't be more
straightforward. From the moment
you open the AED's brightly colored
box, audio instructions prompt you
with simple commands. First, they tell
you to place two adhesive electrode
pads on your coworker's bare chest,
following the diagrams on the pad
wrappers. The defibrillator's built-in
electrocardiograph automatically
detects and analyzes the state of the
patient's heartbeat, and its software
judges whether to administer a shock.
Your colleague's heart is indeed in
ventricular fibrillation, so the AED
asks you to approve the delivery of
simply saved: the automated external defibrillator, which shocks hearts out of cardiac
a tailored burst of electric current.
arrest, hides its sophisticated engineering behind a simple and cheery exterior. photo: CaRDIaC sCIenCe
"Push the button," announces a firm
voice emanating from the box. There's
of a lunch box [see "Simply Saved"], can now be found in hun- only one button, so you press it. Your coworker's body jumps
dreds of thousands of public places, including office buildings, a little, and that may be all that's needed to restore a normal
transportation hubs, and gyms; they've also been installed in rhythm to his heart. If not, the box prompts you to push the
police cars, in schools, and even on the International Space button again after some time. Thanks to your quick actions,
Station. As the price continues to drop-units can sell for as your colleague is saved.
little as US $1000-some experts are urging people at high risk
Meanwhile, what's happening inside the AED is a technical
for cardiac arrest to keep an AED in their homes, just in case.
marvel. The device performs two main functions. First, it needs
The AED's widespread dissemination represents one of the to recognize the lethal haywire rhythm of ventricular fibrillagreatest engineering success stories of the last few decades. In tion. Second, it needs to deliver a 100-kilowatt shock to the heart.
just 20 years, improvements in defibrillator design-in the effi- This jolt allows the heart to restart its normal rhythm, sort of
cacy of the waveform that delivers the electric shock, the way like a Ctrl-Alt-Del for the organ. If the shock is delivered in the
that the unit's energy is stored and
first minute of ventricular fibrillation,
delivered, and the AED's overall ease
in more than 90 percent of cases the
of use-have made it so that a layman
heart will regain a normal sequence
can operate it with little more than a
of electric signals, and the steady conquick tutorial.
tractions will return. It took decades of
careful engineering to develop a device
ou're meeting with a middlethat could perform those two functions
aged coworker who suddenly
reliably, have a long shelf life, and be
slumps over. You have no idea
both safe and easy to use.
what's wrong with him, but cardiac
arrest seems likely. Fortunately, you've
he inherent violence of
had basic training in how to respond to
an electric shock stands in stark
an emergency, so you snap out of your
contrast to its potential therapeuinitial state of shock and call for emertic effect. In fact, the origin of electrigency medical assistance.
cal defibrillation can be traced to both
On average, the wait for an ambuelectrocution and efforts to electrify
lance in populated areas of the United
the United States in the early 1900s.
States is about 11 minutes. From your
Engineers and medically inclined
first-aid training you know that a carexperimenters
had long observed and
saved by a spOON: the first defibrillator
diac-arrest victim's chance of survival
tinkered with the potential of restorused spoons as electrodes. photo: DIttRICK
drops about 10 percent with every
MeDICal hIstoRY CenteR/ Case WesteRn ReseRVe UnIVeRsItY
ing life with electricity. Some of the

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Table of Contents for the Digital Edition of IEEE Spectrum November, 2008