Defibrillator is a device used to deliver high voltage direct current (DC) shock to the chest through a pair of electrode patches or paddles to restart the heart which has suffered a cardiac arrest. Usually the voltage is above 2000 volts. A high voltage capacitor is used in the device to store the energy at high voltage just before delivery. The energy used in a biphasic device is 150 – 200 Joules while that in a monophasic device could be as high as 360 Joules. Biphasic devices are more efficient than monophasic devices, which are being phased out.

What are the other special types of defibrillators?

One special type of defibrillator used in public places (public access defibrillation) is known as automatic external defibrillator (AED). If the AED patches are attached to the chest, it analyzes the heart rhythm and advises whether a shock should be given or not. The user can manually deliver the shock to save the victim.

Another special type of defibrillator is the implantable cardioverter defibrillator (ICD), also known as automatic implantable cardioverter defibrillator (AICD). This device is physically much smaller, but has a long battery life and is expensive. The device is implanted under the skin by a minor surgical procedure. It has advanced electronic circuitry which automatically analyzes heart rhythm and delivers appropriate electrical treatment automatically. The device is usually implanted below the left collar bone and its electrical leads are introduced into the heart through the nearby blood vessel known as subclavian vein.

What precautions are to be taken while using a defibrillator?

A conventional defibrillator is NOT for use by a lay person. It is to be used only by a trained medical personnel. But AEDs can be used by lay persons with minimal training as it has automatic analysis and prompt programming.

Most important precaution during the use of a defibrillator is to keep out of contact with the victim or else you may receive a shock. This may occur even if there is water connecting you and the victim. So ‘all clear’ announcement is commonly used by the operator prior to delivering the shock.

In conventional defibrillator, as automatic rhythm analysis is not available, the trained operator has to decide whether shock is advisable or not. But most modern defibrillators also have an AED mode for emergency use.

Proper application of patches or paddles are necessary. If paddles are being used, adequate amount of conducting gel has to be applied over them for proper delivery of shock. Paddles should be firmly applied for the same purpose as well as to prevent/minimize skin burns.