Automated external defibrillator
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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 basic life support (BLS) classes.
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When an AED is indicated
An automated external defibrillator is used in cases of cardiac arrest. However, the device is not designed to shock a victim experiencing full cardiac arrest, where the heart has no electrical activity. An AED is only designed to shock a victim experiencing:
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 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. 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.
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.
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.
Simplicity of AED use
Unlike regular defibrillators, an automated external defibrillator requires very little training to use. It automatically diagnoses the heart rhythm, determines if a shock is indicated, and automatically selects and delivers the appropriate energy level. 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.
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 [1] (http://circ.ahajournals.org/cgi/content/full/102/suppl_1/I-1?ijkey=0ea84b1fa73ef72b72aef923e0f1adc6d4fd6ba5&keytype2=tf_ipsecsha).
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.
External links
- American Red Cross: Saving a Life is as Easy as A-E-D (http://www.redcross.org/services/hss/courses/aed.html)
- FDA Heart Health Online: Automated External Defibrillator (AED) (http://www.fda.gov/hearthealth/treatments/medicaldevices/aed.html)
de:Automatisierter Externer Defibrillator fr:Défibrillateur semi-automatique it:Defibrillatore semi-automatico