How do you use an automated external defibrillator (AED)?

An AED looks like a first aid box or a small toolbox. The box has two cables attached to it, each with a postcard-sized sticker on the end of it (the electrodes). The electrode pads connect the device to the unconscious person.

Defibrillators are easy to use in an emergency: The box gives spoken instructions, telling you what to do and in which order. Depending on the model, there may also be a small screen or diagrams to help you understand what to do.

When used properly, AEDs recognize two typical conditions of the heart that can make people lose consciousness and stop breathing, and can react accordingly:

• Ventricular fibrillation: Here the heart muscle still contracts, but far too fast and in a chaotic way. As a result, the heart “twitches” rather than pumping, so it is no longer able to pump blood around the body. By exposing the heart to a controlled electric shock, defibrillators can restore a normal heartbeat, making the heart pump effectively again.
• Lack of heart activity (asystole): Here the heart muscles stop contracting completely, and the heart stops pumping. Applying an electric shock won’t help in this case. Cardiac compressions are needed instead. The defibrillator then helps by giving spoken instructions.

You should use a defibrillator if you are resuscitating an unconscious person with the help of others. You can then share the different tasks: One person can start doing chest compressions, while the other person (or people) call for an ambulance and get the defibrillator.

If you are alone, call for an ambulance first and then immediately start doing chest compressions.

As soon as you get hold of a defibrillator, you have to turn it on and connect it. It’s important to continue doing chest compressions until the device tells you to stop. Work together: One person can continue with the chest compressions, while another person sticks the two electrodes on the naked chest of the unconscious person. One of the electrodes should be placed under the right collarbone, and the other should be placed on the left side of the chest – under the armpit. Then follow the spoken instructions given by the device.

If the defibrillator recognizes that someone’s heart is fibrillating, it will ask you to press the shock button to produce an electric shock. The shock button often has a “lightning” symbol on it. Follow the spoken instructions given by the device. It's important to make sure that neither you nor anyone else is touching the unconscious person when the shock button is pressed. Continue to follow the instructions given by the defibrillator afterwards – for instance, the device may tell you to do chest compressions again.