Save a Life: Using a Defibrillator

How to recognise the signs of a sudden cardiac arrest and how to help sufferers

What is sudden cardiac arrest (SCA)?
Sudden cardiac arrest (SCA) is an ‘electrical’ problem. Sudden cardiac arrest occurs when the heart malfunctions and suddenly and unexpectedly stops beating normally. If this happens, blood stops flowing to the brain and other vital organs. This results in the victim becoming unresponsive and not breathing or not breathing normally (gasping). If it’s not treated, sudden cardiac arrest usually causes death within minutes.

Is SCA the same as a heart attack?
Often, a sudden cardiac arrest and heart attack are thought to be the same thing. However they are very different. A heart attack is a ‘plumbing’ problem and is caused when the blood supply to the heart is blocked but the heart keeps beating. Usually the patient will remain conscious and can be talking but has symptoms such as pains in the chest, which may radiate down the arm and up to the jaw. There are other possible symptoms such as sweating, nausea and feeling lightheaded. In some cases a heart attack can lead on to a sudden cardiac arrest if left untreated.

Who is at risk of SCA?
Sudden cardiac arrest can happen to anyone regardless of age, fitness, diet. However your chances may be increased if you have a family history of coronary artery disease. A cardiac arrest can also occur following electrocution, a drug overdose, severe haemorrhage (losing a large amount of blood), a sudden blow to the chest and drowning.

How do I know if someone is in SCA and what should I do?
If you find someone unconscious, unresponsive, not breathing or not breathing normally (gasping), then they are in sudden cardiac arrest. When someone is in sudden cardiac arrest, every minute counts. Every minute without effective treatment reduces that person’s chance of survival by 10 percent. If you find someone in sudden cardiac arrest, call 999 immediately and start CPR. If an automated external defibrillator is available, use this straight away. The AED will talk you through the rescue.

If I try to help can I make the situation worse?
Less than one in 10 people survive an out-of-hospital sudden cardiac arrest in the UK (British Heart Foundation—2015 report). This is partly because bystanders don’t have the skills or confidence to perform CPR. The concern maybe that further harm could be done but the irony is without intervention that person has no chance of survival.

What does an AED do?
 Automated external defibrillators (AEDs) are used to treat sudden cardiac arrest (SCA). The AED is a portable device that checks the heart rhythm and can send an electric shock to the heart to try to restore a normal rhythm. AEDs are the effective treatment for sudden cardiac arrest (SCA). AEDs are intelligent devices, designed to guide anyone through a rescue. You do not need to have a medical background or training to use an AED.

What is the difference between a defibrillator and an AED?
They are the same thing. Both are the name given to an automated external defibrillator, a device that delivers an electrical shock to someone in cardiac arrest. AED is the acronym for this device, however, it is more commonly known as a defibrillator in the UK.

Can I harm myself or others with a defibrillator?
All defibrillators are simple enough for anyone to use as they talk the user through the entire process should an emergency occur. Defibrillators will only deliver a shock to someone in a shockable rhythm. If a normal heart rate is detected, the defibrillator will recognise this and say ‘no shock required’. This also means that you can’t shock someone accidentally.

Can I be prosecuted/sued for helping someone?
To date, there have been no cases of a person being prosecuted/sued for helping someone in medical need.

Cardiac Science is a global industry leader and manufacturer of Powerheart® AEDs. Their Powerheart® G5 AED has been designed with the rescuer in mind, with real-time CPR feedback, user-paced instruction, intuitive pad design and automatic shock delivery.

For more information on SCA and Powerheart® AEDs go to


Yorkshire Ambulance Service ‘Supporting a nation of Lifesavers Campaign Information Guide’.

NHS choices –

British Heart Foundation –

American Heart Association

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