Automated External Defibrillator: Definition & Use

Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

An automated external defibrillator (AED) is used in medical emergencies where someone's heart stops beating. Read this lesson to learn what scenarios may warrant its use and how an AED works. AEDs save lives!

What is an Automated External Defibrillator?

You have probably seen TV shows or movies where someone's heart stops beating. Inevitably, a doctor swoops in and delivers a shock, dramatically yelling 'clear!!' right before it's delivered. It turns out that there's a similar way for a person who isn't a doctor in a hospital to help someone in this situation - through the use of an automated external defibrillator (AED). Being familiar with this handy little device could help you save a life someday!

AEDs are lightweight, portable, battery-operated packs that monitor a person's heart beat and rhythm and deliver an electrical shock to restart the heart if necessary. They are used in emergency situations where a person's heart stops beating, known as sudden cardiac arrest. The heart has its own electrical system which controls both the heart rate and rhythm. As electrical signals move throughout the heart (usually top to bottom), they cause the heart to contract and pump blood. The signals repeat in a regular pattern to produce steady heart rates. If the heart stops beating, blood is no longer being circulated throughout the body, so oxygen and nutrients are not being delivered. This will kill someone within a few minutes if the heart isn't restarted. In fact, it's estimated that the chance of survival decreases by 10% for every minute that passes after the heart stops.

Why Does Sudden Cardiac Arrest Occur?

Sudden cardiac arrest is just that - sudden and unexpected. An injury or illness could cause it to happen, but most cases occur due to something called ventricular fibrillation. This is when the heart rate becomes chaotic, usually starting in the lower chambers of the heart. If not corrected, it can cause the heart to stop completely. When this happens, the heart has to be 'defibrillated' to return to normal functioning. Other causes of sudden cardiac arrest include ventricular tachycardia, where the heart beats too fast, and arrhythmia, where the heart beat is irregular. Once the heart stops beating, intervention is necessary, and this is where the AED comes in!

AEDs in public places may be displayed like this.

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