Defibrillator Facts

This fact sheet will cover a series of important topics about defibrillators.

  • Cardiac arrest or heart attack? When to use a defibrillator
  • What is defibrillation?
  • What is a defibrillator? 
  • How does a defibrillator work? 
  • What to do in an emergency
  • How to use a defibrillator
  • Defibrillator training
  • Hands-only CPR

Cardiac arrest or heart attack? When to use a defibrillator

They’re not the same thing. A cardiac arrest happens when the heart loses its natural rhythm and therefore its ability to pump blood around the body. Instead of beating normally it just quivers or ‘fibrillates’. What’s happening is called ventricular fibrillation, and is a life-threatening condition requiring fast and decisive action. A person suffering cardiac arrest will be unconscious, and will have stopped breathing normally. A heart attack sufferer will be conscious and breathing, unless the attack leads to cardiac arrest.

What is defibrillation?

Defibrillation is the name given to the process of switching the heart from quivering or ‘fibrillating’ to its normal rhythm, using a controlled electric shock.

What is a defibrillator?

A medical device used to deliver the required electric shock to restore a normal heart rhythm in a cardiac arrest sufferer. They are also called AEDs, which stands for Automated External Defibrillator, and are increasingly common in business premises, schools, colleges and other public buildings. Two types are available. Automatic defibrillators will check the heart rhythm and deliver the electric shock themselves, and semi-automatic defibrillators will check the rhythm and instruct someone else to deliver the shock at the right moment.

How does a defibrillator work?

Defibrillators look for and deliver (or instruct someone else to deliver) an electric shock to the heart through the sufferer’s chest wall. They are battery powered and portable. The battery life, if the machine is not used, can be up to five years. The device will check itself on a daily basis, and use flashing lights or a noise to show it’s not ready to use in an emergency.

What to do in an emergency

Call 999 immediately to summon an ambulance. However, the person suffering cardiac arrest hasn’t got time to wait for the ambulance. Every minute without defibrillation or CPR (see below) reduces their chance of survival by 10%. The operator will also be able to tell you if there’s a portable defibrillator nearby. Go to get it only if someone else is doing CPR. (It’s clearly important to tell the local ambulance trust if you ‘ve installed one, so their records can be kept up to date.)

How to use a defibrillator

The box containing the equipment includes diagrams and instructions showing the user where to put it on the patient, and how to administer the shock, and when to use a defibrillator. Taking a course on using a defibrillator is helpful, but not essential. You could still save someone’s life.

Defibrillator training

Models from all manufacturers look different from each other, but they work in a similar manner, so a Zoll defibrillator will have exactly the same function as one from Heartstart or Lifepak. The box containing the defibrillator will contain all the necessary instructions, but a huge boost to confidence is given by attending a course first. That way, the nerves of using a defibrillator for the first time on a real patient can be controlled. Courses can be offered through a number of specialist companies or St John Ambulance.

Hands-only CPR

If you’ve called 999 the operator will probably be able to tell you if there is a defibrillator nearby. Defibrillators in the workplace are now widespread, and it’s recommended that no-one should be more than two minutes away from one. However, if there isn’t one available, you’ll have to pump the blood manually until help arrives.