What is an AED

What is an AED in first aid

This article highlights what AEDs are and how to use them. 

Following the Chain of Survival improves the survival rate from a Sudden Cardiac Arrest dramatically.   To around 50% of patients recovering.

What is an AED in first aid?

AED stands for Automated External Defibrillator (AED).  These are portable devices used to shock the heart back into a proper rhyme.

An AED is used on patients that have suffered a Sudden Cardiac Arrest.  This is when the heart stops pumping blood and oxygen around the body. 

The patient will be unconscious and not breathing. 

Used quickly, an AED can get the heart working again.  The quicker it is used following an incident the better.  This article goes into a little more detail about the role of AEDs in first aid. 



AEDs are also called a ‘Defibrillator’, ‘Defib’ or ‘PAD’ (Public Access Defibrillator).

How to use an AED

Including easy to follow visual & audio instructions, AEDs are designed to be used without training.   The patient will only receive a shock if it is needed.

First Aid training may help to boost confidence.

AEDs deliver an electric shock to the patient’s heart.  This ‘shock’ will hopefully restore the patients’ heart rhythm so blood can start pumping around their body again.  

To achieve this first pads within the AED box need to be attached to the patient’s chest. 

Electrodes in the pads will send information about the person’s heart rhythm to the AED.

The AED then analyses this rhythm and determines automatically if an electric shock is needed.

If a heart rhythm is malfunctioning the AED will deliver an electric shock.  This shock will hopefully allow the heart muscles to function properly again.

When to use AEDs

First Aiders get their name because they are the 'first' person on the scene able to provide aid to the patient.  When a patient is unconscious and not breathing CPR and AEDs should be used as soon as possible.   

If you are first at the scene where someone is unconscious, first check the scene is safe.  If safe proceed to ensure the victims airway is open. 

Hopefully at this point you notice the patient is breathing, has a pulse and that the situation is not life-threatening.  For example, if they’ve fainted. 

However, if the patient isn’t breathing and has no pulse it’s time to follow the chain of survival.  Remember at this point you have already cleared and opened their airways (Use head tilt).

The Chain of Survival is:

  1. Early Access to care >> So call the emergency services.
  2. Early CPR >> so begin CPR until emergency services arrive.
  3. Early Defibrillation >> so get the closest AED and follow instructions.  Hopefully someone nearby can do this for you.
  4. Early advance care >> professional hospital care.

The chain of survival

Call 999 as soon as possible and start CPR.  Hopefully there is help nearby who can retrieve the nearest AED while you begin CPR until the emergency services arrive. 

CPR and AEDs

Following a sudden cardiac arrest CPR helps to keep oxygen following around the body.  So, keep doing CPR until emergency services arrive or the patient revives. 

Evidence shows it is defibrillation from an AED and not CPR that is most likely to get the heart beating correctly again.   

So, commencing CPR as quickly as possible then use an AED soon as possible too.

If CPR and AEDs can be used within a few minutes of a patient suffering a sudden cardiac arrest the chance of survival increases to over 45%.


Public Cases

Tom Lockyer suffered a Sudden Cardiac Arrest while playing football for Luton on the 16th December 2023.  Tom was treated immediately by media pitch side with CPR and shortly after with a defibrillator which got his heart beating to a normal rhythm again.

Christian Eriksen was revived by an AED after suffering a sudden cardiac arrest while playing football for Denmark in the 2020 Euros on January 14th.  CPR and an AED was used very quickly after his collapse.  Christian made a full recovery and is playing football again.

While playing for the NFL team the Buffalo Bills Damar Hamlin suffered a sudden cardiac arrest on the 2nd of January 2023.  Damar received CPR and AED very quickly.  Damar also made a full recovery and resumed playing American Football the next season.

These cases are examples of how patients can recover fully from Sudden Cardiac Arrest if treated quickly and correctly. 

The key to increasing the chance of survival is early CPR and early use of an AED. 

This is why you will see AEDs positioned in many public places.  This is so they can be retrieved quickly in the case of someone suffering a sudden cardiac arrest.   

What causes Sudden Cardiac Arrest (SCA)?

Electrical signals make our heart muscles beat.  This pumps blood around the body distributing oxygen to our organs. 

These electrical signals can stop or malfunction for several different reasons.  This in turn can stop our heart beating or prevent it beating effectively.

Causes include:

  • Ventricular fibrillation, a malfunction in the rhythm of the electrical signal.
  • Electrocution
  • A drug overdose
  • Heart Attack
  • Losing a large amount of blood
  • Suffocation

There is often little or no warning for a sudden cardiac arrest.  A victim will suddenly lose consciousness, have absent or abnormal breathing and no blood circulation.

AEDs deliver an electric shock to the patient’s heart that gets their  electrical signals to the heart going again or back into the correct rhythm.  This is referred to as ‘restarting the heart’.

How Common are SCAs?

Each year, across the UK around 30,000 Sudden Cardiac Arrests occur outside of hospitals.  In Scotland over 3,000 people have resuscitations attempted.  Read Scotland’s strategy to improve survival rates.

The chance of survival is low at around 10%.  This means about 1 in 10 people survive out of hospital cardiac arrests, however this is almost twice the survival rate of a decade ago.

If you follow the Chain of Survival and use a AED quickly, the survival rate dramatically improves, rising to around 1 in 2 patients recovering.


Hopefully this article as highlighted the importance of knowing where your closest AED is. 

If you discover an unconscious patent check you are safe to approach.  After opening their airways, check they are breathing.  If not and they have no circulation immediately follow the ‘chain of survival’.

Contact us today if you have any questions.  Echo3 offer great value online safety training courses for 1000s of happy customers.