Automated external defibrillators (AEDs)
Automated external defibrillators, or AEDs, save lives by delivering an electric shock to the heart when a person is having a cardiac arrest.
Automatic external defibrillators contain instructions, and some give audible instructions, so that even people without medical or first aid training can give help.
AED image credit: Thinkstock/Baloncici
There are thousands of cardiac arrests in the UK every year that don't take place in hospitals.
The British Heart Foundation says that every minute without defibrillation and CPR reduces survival chances of survival by 10%.
Cardiopulmonary resuscitation, usually known as CPR, is first aid to provide temporary artificial breathing and circulation.
AEDs can increasingly be found in shopping centres, sports centres and football grounds.
The first step for a cardiac arrest, before using an AED, is to call 999 for an ambulance.
Following the AED instructions, sticky electrode pads are attached to the chest of the person having a cardiac arrest.
The person giving first aid then stands back while machine then monitors the heart rhythm before charging ready to deliver the shock.
Some AEDs do this automatically, while other may need a button to be pressed.