What is an Automated Defibrillator (AED)?

Why is an AED important?

Automated External Defibrillation

While CPR can help prevent brain damage and death by keeping oxygenated blood moving throughout the body, an automated external defibrillator (AED) can correct the underlying problem for some people who go into sudden cardiac arrest.

Two abnormal heart rhythms in particular, ventricular fibrillation (V-fib) and ventricular tachycardia (V-tach), can lead to sudden cardiac arrest. In V-fib, the heart muscle quivers weakly (“fibrillates”) instead of contracting strongly. In V-tach, the heart muscle contracts too rapidly (“tachy-” means “fast”). Both of these rhythms impair the heart’s ability to pump and circulate blood throughout the body and both are life-threatening.

In many cases, an electrical shock delivered by an AED can correct (insert abnormal heart rhythms instead of V-fib and V-tach)V-fib and V-tach rhythms. The shock disrupts the heart’s electrical activity long enough for it to spontaneously develop an effective rhythm on its own. Using an AED as soon as possible (along with starting CPR immediately) gives the person the best chance of surviving cardiac arrest.

Different types of AEDs are available, but all are similar to operate and guide you using visual displays, voice prompts, or both. If your place of employment has an AED on site, know where it is located, how to operate it, and what the procedures around it are (e.g., for reporting its use or replacing its batteries). Also take note of the location of AEDs in public places that you frequent, such as shopping centres, airports, recreation centres, and sports arenas.

In more than 80% of all sudden cardiac deaths, the person’s heart rhythm is “shockable” (ventricular tachycardia or ventricular fibrillation). In other words, defibrillation could have helped. If the person’s heart has no electrical activity (asystole or flatline), defibrillation won’t help. For each minute that the person has to wait for defibrillation, the chance of survival drops between 7 and 10%.

What is Cardiac arrest? 

Cardiac arrest occurs when the heart stops beating or beats too ineffectively to circulate blood to the brain and other vital organs. Under normal circumstances, a network of special cells in the heart muscle conducts electrical impulses that coordinate contractions, causing the heart to beat rhythmically. In cardiac arrest, the electrical impulses become abnormal and chaotic. This causes the heart to lose the ability to beat rhythmically, or to stop beating altogether.

The respiratory and circulatory systems are very closely linked. After breathing stops, it is not long before the heart stops. This is especially true in children: pediatric cardiac arrests are often the result of airway or breathing emergencies.

Sudden Cardiac Arrest

Cardiac arrest can happen suddenly and without any warning signs; this is called sudden cardiac arrest. People who have a history of cardiovascular disease or a congenital heart disorder are at higher risk for sudden cardiac arrest. However, sudden cardiac arrest can happen in people who appear healthy and have no known heart disease or other risk factors for the condition. A person who experiences sudden cardiac arrest is unlikely to survive without immediate care.

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