Facts on Defibrillators

Defibrillators are used to detect heart rates that are too slow or too fast and correct them using an electrical current. The defibrillator, which can be as small as the size of a pager, saves or improves thousands of lives every year by maintaining or correcting the rhythm of the heart.

How They Work

Normal blood flow is guided by electrical pulses given off by the nervous system. The defibrillator monitors this system and notices any arrhythmias (abnormal rhythms in the heartbeat), emitting a small electrical shock or a strong current each time one occurs to put the heart back into a normal pace.


There are three types of defibrillators, which are available for use in different settings. The most well known and most powerful of the defibrillators is the variety used in hospitals. To use this type, electrodes are placed on the chest of the patient, and a very strong electric current goes through the person, violent enough to cause the muscles surrounding the heart to contract. The second form, called an automated external defibrillator (AED), can be operated by someone with very little medical knowledge. This variety is portable and is often kept on hand by school athletic departments, in case their athletes succumb to cardiac emergencies during practices or games. The third variety is implanted inside the body for people suffering from persistent heart conditions. This type, called an internal cardioverter defibrillator (ICD), can activate a pacemaker, emit a small shock or produce a strong shock, depending on the situation's severity.

Defibrillator Statistics

Statistics on external defibrillators show that the faster a defibrillator machine is used on victims of cardiac arrest, the better the chances of survival. The survival rate dwindles by 10 per cent each minute after cardiac arrest begins when the patient does not receive defibrillation. However, cardiac arrest patients have a survival rate up to 49 per cent when a defibrillator is used within the first five to seven minutes after the attack.

Use of Automated External Defibrillators (AEDs)

Because it is so essential that defibrillation of a cardiac arrest patient occur as quickly as possible, AEDs are designed to be fairly easy to use. After the defibrillator is turned on, voice commands guide the user in the steps to quickly administer defibrillation to the patient. The user then places two electrodes on the patient's chest. If the machine indicates that the heartbeat is dangerously erratic, it instructs the user to move away from the patient and press the button to shock the person.

Guidelines for Using an AED

Even though AEDs are designed to be easy to use, it is important that people who may have to administer defibrillation be trained in how to use the machine and in CPR. The operator of an AED must be trained to recognise the signs of cardiac arrest, understand the safety requirements of using the AED and be comfortable using a specific model of AED, as machines may have slight variations. Because survival is still not guaranteed with an AED, an AED operator must also be able to do CPR, a crucial part of the life-saving arsenal for cardiac arrest victims.