An Introduction to Automatic External Defibrillation

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About AEDs

Defibrillation is a process in which an electric shock is administered by a defibrillator to re-establish the heart’s normal heart rhythm and contraction. An automatic external defibrillator or AED for short is an electronic device that examines the heart rate and rhythm and if necessary will initiate an electric shock known to restart the heart when cardiac arrest is evident. The purpose of delivering an electric shock to the heart is to correct the abnormalities in electrical conduction brought about by several irregularities in electrical conductivity of the heart which will result in cardiac arrest if not administered early.

Although active defibrillation is advance skill only paramedics and emergency personnel are permitted to use in emergency situations, individuals with First Aid Training are taught how to use public access defibrillation devices which many countries have already adapted as a law to promulgate its visibility in many public places such as airports, schools, shopping centers and homes.

Automatic External Defibrillator
Automatic External Defibrillator

Since first aid and CPR concepts are constantly being updated and revised, the use of public automatic external defibrillation is now a standard concept in First Aid Courses and lectures. Basically all AEDs regardless of the brand or manufacturer are devised to be as easy and user friendly as possible. AEDs usually have two electrodes and cables attached to adhesive pads which should be placed on the victim’s chest. The pads and the cable system send the electrical signal from the heart into the device to analyze the heart rate and rhythm and if appropriate, will automatically deliver an electric shock.

All AEDs have a built – in rhythm analysis system which is programmed to determine if the victim needs an electric shock depending on the values presented in the monitoring system. This system enables rescuers even without proper First Aid Certification to deliver defibrillation with only minimal training. Moreover, AEDs are equipped with a recorded log of the victim’s ECG (electrocardiogram), shock data and other pertinent data about the device’s performance such as the date, time and number of shocks supplied so that data can be evaluated by advance paramedics upon arrival for the continuity of care.

When the heart’s normal electrical conductivity is disrupted

Ventricular fibrillation (V- fib) is the most common abnormality in heart rhythm which majority often leads to eventual cardiac arrest. The second, potentially life – threatening problem in heart conductivity is ventricular tachycardia (V-tach) in which the heart beats so fast and is inadequately pumping blood to the body which will later wear itself down and cease to function.

Care for cardiac arrest

When the heart is incapacitated or is having difficulty delivering adequate blood supply to the body’s vital organs, the body will later will shut down due to the lack of oxygen unless the heart is restored to its functional capability. In this situation, time is a crucial factor for survivability. For every minute that defibrillation is delayed, the victim’s chances of survival decreases significantly. CPR is the initial care for cardiac arrest until defibrillation is available. Perform the appropriate cycles of chest compressions and rescue breathing until an AED is available.


Alton, T. et al (2012). First Aid, CPR and AED Standard 6th Ed. Jones & Bartlett Learning

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