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How a heart defibrillator works

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When a person has a heart attack, immediate care is vital. A heart attack victim will only survive for a few minutes without help.

So let’s start at the beginning – What is a heart attack? This video offers a nice explanation:

Where do the fatty deposits come from, and what do they look like? This video is gross, but offers a graphic demonstration:

So, the heart stops pumping blood. Now what? The best way currently available to restart a normal heart rhythm is known as the heart defibrillator. Here is the classic scene (complete with dramatic music) that we see on TV when the defibrillator comes out:

Now there are also smaller, automated defibrillators available in offices, airports, amusement parks, schools, etc. This video shows how a typical unit is used:

The heart of a heart defibrillator is a big capacitor. A battery takes perhaps half a minute to charge this capacitor, in the same way that a camera flash charges a capacitor. In this video you can see a typical capacitor from a defibrillator (it’s the large item on the right with the red wires), rated at 54 microfarads and 4,200 volts.

Once charged up, this capacitor contains a huge amount of energy (in this case 970 joules). The defibrillator delivers that charge in a millisecond through the paddles, and the hope is that the shock resets the heart so it can begin beating normally.

For more info see: How the heart works.


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