<s>
An	O
automated	B-Algorithm
external	I-Algorithm
defibrillator	I-Algorithm
(	O
AED	O
)	O
is	O
a	O
portable	O
electronic	O
device	O
that	O
automatically	O
diagnoses	O
the	O
life-threatening	O
cardiac	B-Application
arrhythmias	I-Application
of	O
ventricular	O
fibrillation	O
(	O
VF	O
)	O
and	O
pulseless	B-Application
ventricular	I-Application
tachycardia	I-Application
,	O
and	O
is	O
able	O
to	O
treat	O
them	O
through	O
defibrillation	O
,	O
the	O
application	O
of	O
electricity	O
which	O
stops	O
the	O
arrhythmia	B-Application
,	O
allowing	O
the	O
heart	O
to	O
re-establish	O
an	O
effective	O
rhythm	O
.	O
</s>
<s>
With	O
simple	O
audio	O
and	O
visual	O
commands	O
,	O
AEDs	O
are	O
designed	O
to	O
be	O
simple	O
to	O
use	O
for	O
the	O
layperson	O
,	O
and	O
the	O
use	O
of	O
AEDs	O
is	O
taught	O
in	O
many	O
first	B-Application
aid	I-Application
,	O
certified	O
first	O
responder	O
,	O
and	O
basic	O
life	O
support	O
(	O
BLS	O
)	O
level	O
cardiopulmonary	O
resuscitation	O
(	O
CPR	O
)	O
classes	O
.	O
</s>
<s>
An	O
automated	B-Algorithm
external	I-Algorithm
defibrillator	I-Algorithm
is	O
used	O
in	O
cases	O
of	O
life-threatening	O
cardiac	B-Application
arrhythmias	I-Application
which	O
lead	O
to	O
sudden	O
cardiac	O
arrest	O
,	O
which	O
is	O
not	O
the	O
same	O
as	O
a	O
heart	O
attack	O
.	O
</s>
<s>
In	O
each	O
of	O
these	O
two	O
types	O
of	O
shockable	O
cardiac	B-Application
arrhythmia	I-Application
,	O
the	O
heart	O
is	O
electrically	O
active	O
,	O
but	O
in	O
a	O
dysfunctional	O
pattern	O
that	O
does	O
not	O
allow	O
it	O
to	O
pump	O
and	O
circulate	O
blood	O
.	O
</s>
<s>
In	O
ventricular	B-Application
tachycardia	I-Application
,	O
the	O
heart	O
beats	O
too	O
fast	O
to	O
effectively	O
pump	O
blood	O
.	O
</s>
<s>
Ultimately	O
,	O
ventricular	B-Application
tachycardia	I-Application
leads	O
to	O
ventricular	O
fibrillation	O
.	O
</s>
<s>
Uncorrected	O
,	O
these	O
cardiac	O
conditions	O
(	O
ventricular	B-Application
tachycardia	I-Application
,	O
ventricular	O
fibrillation	O
,	O
asystole	O
)	O
rapidly	O
lead	O
to	O
irreversible	O
brain	O
damage	O
and	O
death	O
,	O
once	O
cardiac	O
arrest	O
takes	O
place	O
.	O
</s>
<s>
This	O
is	O
in	O
contrast	O
to	O
more	O
sophisticated	O
manual	O
and	O
semi-automatic	O
defibrillators	O
used	O
by	O
health	O
professionals	O
,	O
which	O
can	O
act	O
as	O
a	O
pacemaker	B-Device
if	O
the	O
heart	O
rate	O
is	O
too	O
slow	O
(	O
bradycardia	B-Algorithm
)	O
and	O
perform	O
other	O
functions	O
which	O
require	O
a	O
skilled	O
operator	O
able	O
to	O
read	O
electrocardiograms	B-Application
.	O
</s>
<s>
In	O
a	O
study	O
analyzing	O
the	O
effects	O
of	O
having	O
AEDs	O
immediately	O
present	O
during	O
Chicago	O
's	O
Heart	O
Start	O
program	O
over	O
a	O
two-year	O
period	O
,	O
of	O
22	O
individuals	O
,	O
18	O
were	O
in	O
a	O
cardiac	B-Application
arrhythmia	I-Application
which	O
AEDs	O
can	O
treat	O
.	O
</s>
<s>
Automated	B-Algorithm
external	I-Algorithm
defibrillators	I-Algorithm
are	O
generally	O
either	O
kept	O
where	O
health	O
professionals	O
and	O
first	O
responders	O
can	O
use	O
them	O
(	O
health	O
facilities	O
and	O
ambulances	O
)	O
as	O
well	O
as	O
public	O
access	O
units	O
which	O
can	O
be	O
found	O
in	O
public	O
places	O
including	O
corporate	O
and	O
government	O
offices	O
,	O
shopping	O
centres	O
,	O
restaurants	O
,	O
public	O
transport	O
,	O
and	O
any	O
other	O
location	O
where	O
people	O
may	O
congregate	O
.	O
</s>
<s>
The	O
pads	O
allow	O
the	O
AED	O
to	O
examine	O
the	O
electrical	O
output	O
from	O
the	O
heart	O
and	O
determine	O
if	O
the	O
patient	O
is	O
in	O
a	O
shockable	O
rhythm	O
(	O
either	O
ventricular	O
fibrillation	O
or	O
ventricular	B-Application
tachycardia	I-Application
)	O
.	O
</s>
<s>
Many	O
AED	O
units	O
have	O
an	O
'	O
event	O
memory	O
 '	O
which	O
store	O
the	O
ECG	B-Application
of	O
the	O
patient	O
along	O
with	O
details	O
of	O
the	O
time	O
the	O
unit	O
was	O
activated	O
and	O
the	O
number	O
and	O
strength	O
of	O
any	O
shocks	O
delivered	O
.	O
</s>
<s>
The	O
first	O
commercially	O
available	O
AEDs	O
were	O
all	O
of	O
a	O
monophasic	O
type	O
,	O
which	O
gave	O
a	O
high-energy	O
shock	O
,	O
up	O
to	O
360	O
to	O
400	O
joules	B-Language
depending	O
on	O
the	O
model	O
.	O
</s>
<s>
Newer	O
AEDs	O
(	O
manufactured	O
after	O
late	O
2003	O
)	O
have	O
tended	O
to	O
utilise	O
biphasic	O
algorithms	O
which	O
give	O
two	O
sequential	O
lower-energy	O
shocks	O
of	O
120	O
–	O
200	O
joules	B-Language
,	O
with	O
each	O
shock	O
moving	O
in	O
an	O
opposite	O
polarity	O
between	O
the	O
pads	O
.	O
</s>
<s>
Others	O
may	O
give	O
a	O
stepped	O
approach	O
to	O
energy	O
delivery	O
,	O
usually	O
in	O
a	O
200J	O
,	O
a	O
second	O
200J	O
,	O
then	O
300J	O
,	O
and	O
finally	O
360J	O
shock	O
,	O
with	O
any	O
further	O
shocks	O
also	O
being	O
360	O
Joules	B-Language
.	O
</s>
<s>
Unlike	O
regular	O
defibrillators	O
,	O
an	O
automated	B-Algorithm
external	I-Algorithm
defibrillator	I-Algorithm
(	O
AED	O
)	O
requires	O
minimal	O
training	O
to	O
be	O
used	O
(	O
or	O
even	O
no	O
training	O
)	O
.	O
</s>
<s>
Their	O
ease	O
of	O
use	O
has	O
given	O
rise	O
to	O
the	O
notion	O
of	O
public	B-Algorithm
access	I-Algorithm
defibrillation	I-Algorithm
(	O
PAD	O
)	O
.	O
</s>
<s>
Observational	O
studies	O
have	O
shown	O
that	O
in	O
out	O
of	O
hospital	O
cardiac	O
arrest	O
,	O
public	B-Algorithm
access	I-Algorithm
defibrillators	I-Algorithm
when	O
used	O
were	O
associated	O
with	O
40%	O
median	O
survival	O
.	O
</s>
<s>
Automated	B-Algorithm
external	I-Algorithm
defibrillators	I-Algorithm
are	O
now	O
easy	O
enough	O
to	O
use	O
that	O
most	O
states	O
in	O
the	O
United	O
States	O
include	O
the	O
"	O
good	O
faith	O
"	O
use	O
of	O
an	O
AED	O
by	O
any	O
person	O
under	O
Good	O
Samaritan	O
laws	O
.	O
</s>
<s>
In	O
New	O
South	O
Wales	O
,	O
the	O
Work	O
Health	O
and	O
Safety	O
Regulation	O
(	O
2011	O
)	O
requires	O
an	O
employer	O
to	O
use	O
a	O
risk	O
assessment	O
to	O
ensure	O
that	O
there	O
is	O
adequate	O
provision	O
for	O
first	B-Application
aid	I-Application
;	O
when	O
there	O
is	O
a	O
sufficient	O
risk	O
it	O
warrants	O
providing	O
a	O
defibrillator	O
.	O
</s>
<s>
In	O
2012	O
,	O
AED	O
's	O
(	O
automated	B-Algorithm
external	I-Algorithm
defibrillators	I-Algorithm
)	O
were	O
under	O
scrutiny	O
by	O
the	O
U.S.	O
Food	O
and	O
Drug	O
Administration	O
(	O
FDA	O
)	O
which	O
considered	O
reclassifying	O
AEDs	O
as	O
class	O
III	O
premarket	O
approval	O
devices	O
.	O
</s>
<s>
In	O
the	O
late	O
1970s	O
the	O
Heart-Aid	O
was	O
developed	O
as	O
the	O
first	O
truly	O
automated	B-Algorithm
external	I-Algorithm
defibrillator	I-Algorithm
that	O
was	O
designed	O
for	O
the	O
public	O
.	O
</s>
