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How does a defibrillator work?

In an emergency situation, knowing how to use a defibrillator could save someone’s life. You can find defibrillators in numerous public places, from leisure centres to train stations, and knowing how a defibrillator works can help you act more effectively in a stressful situation. To help you feel more confident using a defibrillator, here’s a quick run through of what you need to know.

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What is a defibrillator?

A defibrillator is a machine that sends a high energy electric shock through the heart. This high energy electric shock is called defibrillation. The aim of this shock is to return a heart to its normal working state if it goes into cardiac arrest.

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When should I use a defibrillator?

If an individual is showing signs of a cardiac arrest, a defibrillator can be used to return their heart to its normal rhythm. A cardiac arrest is when the heart suddenly stops pumping blood around the body, usually due to a problem with the heart’s electrical signals. If the heart stops pumping blood around the body, the brain will be starved of oxygen and this will result in a person losing consciousness and stopping breathing.

A cardiac arrest is considered a medical emergency and immediate action needs to be taken, otherwise it could be fatal. If someone is in cardiac arrest, they will be unconscious, unresponsive and they won’t be breathing, or they won’t be breathing normally. If you come across someone in this state, you can improve their chances of survival by calling emergency services and giving CPR as soon as possible.

It’s at this point where you can also use a defibrillator if you have one to hand. If you’re in a public place, this would usually be an automated external defibrillator (AED), as these are designed to be used with little or no training.

Not sure how to perform CPR? Take a look at our blog on performing CPR to get a better idea of what to do in a medical emergency.

How does a defibrillator work?

Defibrillators are usually very easy to use. They have spoken step by step instructions on the machine, and often there are diagrams to guide you through the whole process. To use a defibrillator, you’ll need to place the pads correctly on the patient’s chest. Peel the pads off the plastic and stick them onto the patient’s bare skin as shown on the pictures on the defibrillator. You’ll need to do this while someone continues to administer CPR.


The defibrillator will then need to analyse the patient’s heart rhythm. To do this, you’ll need to stop administering CPR. How an AED works is by then determining whether the patient has a heart rhythm that can be helped by a shock. If it finds that a defibrillator can help, you’ll then need to press the shock button when instructed. Ensure no one is touching the patient at this time.

The defibrillator will then shock the patient. When given the all clear by the defibrillator, you’ll then need to continue to administer CPR. Continue until the patient displays obvious signs of life, or until the defibrillator instructs you to stop so it can reanalyse the patient’s heart rhythm.

If the defibrillator tells you that patient won’t be helped by a shock, don’t press the shock button. Continue with CPR until the emergency services arrive.

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How can I get a defibrillator?

Depending on your place of work or the public place you want to get a defibrillator for, you’ll need to buy a defibrillator that’s tailored to your needs. At Cardiac Science, we offer defibrillator solutions for a range of industries, from schools and athletics to corporations. If you’re already clued up on what kind of defibrillator you’re looking for, take a look at our range of defibrillator products to find the one you need. If you need advice on what type of defibrillator is right for your organisation, get in contact with us today and we’ll be happy to provide guidance on all our products.

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