top of page

What does a defibrillator actually do for your heart?

Some people call them defibrillators. Some call them “defib” machines. Others call them by their proper name – an AED – which simply means an Automated External Defibrillator.

But whatever you call them, what do they actually do to your heart and how do they work? The truth is quite simple but like many things to do with first aid, a lot of myths surround them, leading some people to be unsure about using them.

The best analogy for what a defib machine does is this. Have you ever seen a room full of noisy children? (Like in a classroom before the teacher comes in.) There can be lots of talking, laughing, yelling, mucking around etc. It’s all a bit chaotic.

If the teacher comes in and simply says “excuse me class, could you all settle down please?”, they might not get much compliance. It could all still be a bit crazy. But if the teacher slams a big fat ruler suddenly down on the desk, the noise and sudden shock can bring the entire class to attention and back to normal behaviour.

This is what a defibrillator does. Technically it doesn’t “restart” a stopped heart, rather it actually “resets” it. Before the machine fires off its shock, the patient’s heart can be behaving like those crazy kids in the class. Beating irregularly and going a bit wild and crazy. (This is called “fibrillation”.) The defibrillator’s shock acts like the teacher’s ruler slamming down on the desk. Suddenly the heart starts behaving itself and goes back into a regular rhythm.

Now the key thing to remember about a defibrillator is that they are AUTOMATIC! So, they are very smart machines. And you almost can’t do anything wrong with them.

For a start did you know that if you try to use a defibrillator on a person who doesn’t need it, it won’t work? Yes, the machine automatically assesses the heart rhythm of the patient and if defibrillation is not needed, it won’t fire off a shock. So, if you think a person might need a defibrillator, don’t think, just act! Try it and if it’s not needed the machine won’t do a thing.

Also, they are so smart how, they tell you how to use them. Just switch the defibrillator on and follow the voice prompts and it TELLS you what to do. There is also no fear of the defibrillator accidentally giving you a shock or “electrocuting” the patients. They can’t do either of that.

The bottom line is, when it comes to using a defibrillator, trust the machine. You have almost no chance of doing harm and are only likely to do good. Of course, if you really want to be fully and properly trained in how to use an AED, book in for training now at


bottom of page