First Aid procedures: defibrillation

During a cardiac arrest, the heart continues to beat but in an uncoordinated way. This means it no longer pumps blood to the brain and other key organs effectively.

Delivering an electronic shock to the heart can restore a normal rhythm, a machine called an AED (automated external defibrillator) can be used to do this.

AEDs can now be found in many public places; stations, airports, stadiums. Just switch the machine on, it then gives instructions on screen as to what to do next.

The AED is attached to the person's chest using adhesive pads. It analyses the casualty's heart rhythm automatically and advises the operator on whether an electronic shock is required.

The shock is delivered by pressing a button on the AED.

Actions

• Call 999
• Continue with CPR while the AED is prepared and the adhesive pads are attached
• The AED will give a series of visual and verbal prompts as soon as it's switched on
• Follow the prompts until the emergency services arrive and take over

Further actions

If the casualty starts breathing normally, place them in the recovery position.

Leave the AED attached.

The British Red Cross last medically reviewed this article in December 2009.