Defibrillators for Home Use*

A DEFIBRILLATOR CAN SAVE A LIFE!
An automated external defibrillator (AED) is a portable electronic device that diagnoses and treats cardiac arrest by reestablishing an effective heart rhythm. This treatment is called defibrillation, which applies an electric shock to the entire heart muscle, uniformly clearing the electrical activity of the heart, hopefully allowing it to resynchronize.
The use of AEDs is taught in many basic life support (BLS) classes.
When an AED is indicated
An automated external defibrillator is used in cases of cardiac arrest. However,
the device will not shock a victim in asystole ('flatline') where the heart has
no electrical activity, as it is ineffective in these cases. An AED is designed
to shock a victim experiencing:
Ventricular fibrillation (VF)
Ventricular tachycardia (VT)
In cardiac arrhythmia, the heart is beating, yet in an unusual pattern, which
can be life-threatening if left uncorrected. In ventricular fibrillation, the
electrical activity of the heart becomes chaotic preventing the ventricle from
effectively pumping blood. In ventricular tachycardia, the heart beats too fast
to effectively pump blood. Frequently, ventricular tachycardia leads to
ventricular fibrillation.
Uncorrected, these cardiac conditions rapidly lead to irreversible brain damage
and death. For every minute that a person in cardiac arrest goes without being
defibrillated, the chance of survival decreases by 10 percent.
Unlike some more sophisticated defibrillators used by health professionals, if
the heart rate is too slow (bradycardia), these devices do not typically pace
the heart to make it beat faster.
Where AEDs are found
Automated external defibrillators can be found in corporate and governmental
offices, shopping centers, airports, restaurants, hotels, sports stadiums,
schools and universities, community centers, and other places where large groups
of people gather and the risk of a sudden cardiac arrest incident is likely. In
some cities, all police vehicles carry an AED. In order to make them highly
visible, public AEDs often are bright red, green, or yellow in color, and are
mounted in protective cases near the entrance of a building. When these
protective cases are opened, and the defibrillator removed, most will sound a
buzzer to alert nearby Staff as to their removal. Most of these alarms do not
summon emergency services, so emergency services should be called as soon as an
AED is sent for or used.
Typically, an AED kit will contain a face shield, for providing a barrier
between patient and first aider during rescue breathing; a pair of Nitrile,
non-allergenic gloves; a pair of Tuff Cut scissors, for cutting through a
patients clothing to expose the chest; a small towel for wiping away any
moisture on the chest and a razor for shaving those with very hairy chests.
AEDs can also be kept and used in the home, particularly important for those
with existing heart conditions. The number of devices in the community will
continue to grow as more and more citizens begin to understand their importance
in providing first aid.
Increasingly, many Ambulances are carrying AED or AED-Capable Defibrilators to
allow Basic Life Support personnel such as First Responders and EMT-Bs/IVs to
give electrical therapy to patients when the providers aren't trained in EKG
administration or rhythm analysis. Some states, such as Tennessee and many
others, are beginning to require AEDs to be carried by basic life support
ambulances and first response trucks. Newer, ruggidized AEDs from makers like
Zoll and Physio-Control cater specifically to this market.
How an AED works
An AED is called external because the operator applies the electrode pads to the
bare chest of the victim, unlike internal defibrillators, which have electrodes
surgically implanted inside the body of a patient.
Once the pads are attached to the patient, the AED diagnoses the heart rhythm
and determines if a shock is needed to treat fibrillation. If the device
determines that a shock is necessary, it will charge in preparation to deliver
the shock. When charged, the device instructs the user to ensure no one is
touching the victim and then to press a button to deliver the shock. After the
shock is delivered, the device again monitors the heart rhythm of the victim to
determine if another shock is necessary.
In some cases, after an AED has been used, its 'event memory' is downloaded and
analyzed by the installing organisation. This memory stores the ECG of the
patient and carries details of the time the unit was activated and the number
and strength of any shocks delivered. From the ECG, it is possible to see the
effectiveness of both CPR and defibrillation on the patients heart. A successful
defibrillation, in the UK, is one that causes VF to be converted to another
rhythm, even if this rhythm is unshockable. In other cases, such as in older
AEDs or in models which do not support cards, rhythm strips are printed which
contain the shocked rhythms, a summary of the code, and the status of the
machine.
There are two main types of AEDs on the market today: semi-automatic and
fully-automatic. Semi-automatic AEDs prompt the user to stand clear and then to
push a shock button to defibrillate. Fully-automatic units sound a stand clear
voice prompt and then deliver the shock automatically without the user having to
push a button.
In recent years, two sub-types of AEDs have become available. Monophasic and
Biphasic technologies. Older defibrilators used a monophasic electrical
waveform, which utilized a high joule energy, up to 360 to 400, depending on the
model. This caused increased cardiac injury and in some cases second and third
degree burns around the shock pad sites. Newer AEDs (Manufactured after late
2003) feature what is known as a Biphasic waveform. These are designed to
utilize a lower-energy shock of 120 - 200 joules, and shock twice insted of once
per cycle, once from the chest pad, and once from the rib or back pad. This
lower energy waveform has proven more effective in clinical testing, as well
offers a reduced rate of complications and reduced recovery time.
Simplicity of AED use
Unlike regular defibrillators, an automated external defibrillator requires very
little training to use. It automatically diagnoses the heart rhythm and
determines if a shock is indicated. Automatic models will administer the shock
without the user's command. Semi-automatic models will tell the user that a
shock is indicated, but the user must tell the machine to do so, usually by
pressing a button. In most circumstances, the user cannot override a "no shock"
advisory by an AED. AEDs can even be used on children (those under 55 lbs [25
kg] in weight, or under age 8); all that is required is the use of more
appropriate pads. Some organizations, such as the American Heart Association,
recommends that if pediatric AED pads are not availible, adult pads should be
used to determine if the child is in a shockable rhythm. There is insufficent
evidence to suggest that a child, in a shockable cardiac arrest, can be "hurt"
by an adult defibrillation energy setting.
All AEDs approved for use in the United States use a synthesized voice to prompt
users through each step. Because the user of an AED may be deaf or hard of
hearing, many AEDs now include a screen to provide visual prompts. Most units
today are designed for use by non-medical operators. Their ease of use has given
rise to the notion of public access defibrillation (PAD), which experts agree
has the potential to be the single greatest advance in the treatment of
out-of-hospital cardiac arrest since the invention of CPR.
Liability
Most health professionals agree that automated external defibrillators are so
easy to use that most, if not all, states in the United States now include the
"good faith" use of an AED by any person under the Good Samaritan laws. "Good
faith" protection under a Good Samaritan law means that a first aid responder
cannot be held civilly liable for the harm or death of a victim by providing
improper or inadequate care, given that the harm or death was not intentional
(and other certain circumstances). In most states, Good Samaritan laws provide
protection for the use of AEDs by trained and untrained responders, to a point.
Even for trained providers, AEDs provide little liability if used correctly, in
fact even the NREMT-B and many state EMT and almost all Basic Life
Support/Professional CPR classes offered incorporate AED education as parts of
their program.
The source of this article is
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