What is a Defibrillator?

Have you ever passed a box marked ‘AED’ or ‘life-saving device’ and wondered: “What is a defibrillator?” They’re appearing in public places all over the UK, with the intention of making it easier to prevent deaths from cardiac arrests. As defibrillators become more commonplace, it’s useful to know how they work and how to go about using one.

There are various types of defibrillator. The AED, or automated external defibrillator, is the version you’re most likely to encounter, as it’s these that are appearing on streets and in busy venues such as sports centres and railway stations.

What is an AED?

A defibrillator is a device that delivers an electric shock into a patient’s chest, in order to start their heart pumping normally. You’ve probably seen them being used in a television programme or film, although that would have been simulated, not real.

AED defibrillator

It’s called a defibrillator because the shock is intended to snap the heart out of a state called fibrillation, where it’s not functioning correctly as a blood pump.

As its name suggests, the AED (automated external defibrillator) works without its operator requiring even minimal medical knowledge. Being automatic, they contain sensors that identify the condition of the heart and control the delivery of electric shocks.

Perhaps confusingly, there are two types of AED: automatic and semi-automatic. The difference comes down to whether the operator presses the button that delivers an electric shock (semi-automatic), or whether the device makes the shock happen.

While an AED could be used by someone with no training, it’s recommended that they’re operated by someone who’s received a basic level of instruction.

How does an AED work?

An AED comprises a control box, from which wires lead to pads containing electrodes. Instructions on the AED unit show how these pads are placed against the chest of the patient. Once the pads are in place, the device senses the condition of the patient’s heart rhythms.

If the AED determines that an electric shock is necessary, it will tell the AED operator what to do using either visual or audible instructions.

Fundamentally, an AED is a battery attached to a computer that performs the analysis, and a set of electrodes that monitor the patient and deliver the electric shocks.

AED defibrillator

When to use an AED

Signs that someone is suffering from cardiac arrest are that they’re unresponsive to speech and touch, and they appear not to be breathing.

A cardiac arrest can be caused by:

  • A heart attack.
  • Being unable to breathe due to choking.
  • Sudden trauma, such as electrocution or a serious accident.

If you’re not sure whether to use an AED on someone, it’s sensible to assume you should. Once applied to the patient’s body, the sensors in the AED will determine whether electric shocks are necessary.

Organisations such as the British Red Cross offer short courses in how to use an AED. However, even if you don’t have any training in using an AED, or even in first aid, it’s recommended that should you find yourself in an emergency situation, you should have a go at using the device. You could save someone’s life.

The Resuscitation Council (UK) has formally stated that use of AEDs should not be limited to people that have been trained in how to use them. While training is desirable, the potential benefits of using an AED, even by someone with absolutely no medical experience, outweighs the potential risks.