Knowing how to use an AED could help you save someone’s life during a cardiac arrest.

An Automated External Defibrillator, usually shortened to AED, is designed to analyse a person’s heart rhythm and deliver an electrical shock when one is required.

You do not need to be a healthcare professional to use one.

You do not even need to have received previous AED training.

Modern AEDs give clear spoken and visual instructions that guide the rescuer through what to do.

If someone is unresponsive and not breathing normally, the priorities are to call 999, start CPR and use an AED as soon as one becomes available.

This guide explains what to do step by step.

How to Use an AED in an Emergency

If you find someone who appears to be unresponsive:

Make sure it is safe to approach.
Check whether the person responds.
If they are unresponsive, call 999 immediately.
Assess their breathing while waiting for the call to be answered.
If they are not breathing normally, start CPR.
Send someone to get an AED if one is available.
As soon as the AED arrives, switch it on and follow its instructions.
Attach the electrode pads to the person’s bare chest.
Make sure nobody touches the person while the AED analyses the heart rhythm.
If the AED advises a shock, make sure everybody is clear and allow the shock to be delivered.
Immediately restart CPR.
Continue following the AED prompts until professional help takes over or the person shows clear signs of life.

Let’s look at each stage in more detail.

Step 1: Check That It Is Safe to Approach

Before helping somebody, quickly check for danger.

Potential hazards might include:

traffic
electricity
fire
machinery
chemicals
water
other environmental dangers

Do not put yourself in serious danger.

If the area is safe, approach the casualty.

Step 2: Check for a Response

Speak loudly to the person.

Ask something simple such as:

“Are you alright?”

Gently shake their shoulders if appropriate.

If they respond, assess what is wrong and get appropriate help.

If they do not respond, treat them as unresponsive.

Step 3: Call 999 Immediately

Current Resuscitation Council UK guidance advises calling 999 as soon as you identify that someone is unresponsive.

This is an important change from older sequences that taught rescuers to complete the breathing assessment before making the emergency call.

If you have a mobile phone, put it on speaker so you can continue helping the casualty while speaking to the ambulance service.

If other people are present, ask somebody to make the call and another person to locate an AED if one is available.

The ambulance service call handler can help you assess whether the casualty is breathing normally and provide CPR instructions if needed.

Step 4: Check Whether They Are Breathing Normally

Assess the person’s breathing while waiting for the 999 call to be answered.

An unresponsive person who is not breathing normally should be treated as being in cardiac arrest.

Do not mistake occasional gasps for normal breathing.

Cardiac arrest can cause:

slow, laboured breathing
irregular gasps
panting
other abnormal breathing patterns

These are sometimes called agonal breaths.

A person may also display a short period of seizure-like activity when cardiac arrest occurs.

If the person is unresponsive and you are unsure whether their breathing is normal, assume cardiac arrest and start CPR.

The ambulance service call handler can help you make this decision.

Step 5: Start CPR

If the casualty is unresponsive and not breathing normally, start CPR immediately.

For an adult:

place the heel of one hand in the centre of the chest, on the lower half of the breastbone
place your other hand on top
interlock your fingers
keep your arms straight
compress the chest by 5 to 6 cm
compress at 100 to 120 times per minute
allow the chest to fully recoil after each compression

If you are trained and willing to give rescue breaths, provide:

30 chest compressions followed by 2 rescue breaths.

If you are not trained to give rescue breaths, provide continuous chest compressions.

Try to minimise interruptions.

CPR helps circulate oxygenated blood, but it does not replace defibrillation when a shockable heart rhythm is present.

That is why getting an AED to the casualty quickly is so important.

Step 6: Get an AED as Quickly as Possible

If somebody else is present, ask them to find the nearest AED while you continue CPR.

The 999 call handler may be able to direct somebody to a nearby registered defibrillator.

Public access AEDs can be found in places such as:

workplaces
shopping centres
railway stations
leisure facilities
community buildings
schools
sports facilities
public spaces

AEDs registered with The Circuit, the UK’s national defibrillator network, can be identified by ambulance services during an emergency.

Do not stop CPR and simply wait for the AED to arrive.

If there are several rescuers, one person should continue CPR while another retrieves and prepares the AED.

Step 7: Switch on the AED

As soon as the AED arrives, open it.

Some AEDs switch on automatically when the lid is opened.

Others have a clearly marked power button.

Switch the AED on and listen to it.

From this point, the device will guide you through the process using spoken and/or visual instructions.

Different AED models look slightly different, but the basic process is very similar.

Step 8: Expose the Casualty’s Chest

AED electrode pads need to be attached directly to bare skin.

Expose the person’s chest sufficiently to position the pads correctly.

Clothing may need to be cut or removed.

This can understandably make rescuers uncomfortable, particularly when treating someone they do not know.

However, during a cardiac arrest, correct pad placement and life-saving treatment take priority.

Does a bra need to be removed?

Not necessarily.

If the AED pads can be positioned correctly on bare skin without the bra interfering, it can remain in place.

If it prevents correct pad placement, it should be removed.

Preserve the person’s dignity as much as reasonably possible, but do not delay essential treatment.

Step 9: Prepare the Chest if Necessary

Most casualties will require very little preparation before applying AED pads.

There are, however, some situations to be aware of.

If the chest is wet

If necessary, quickly dry the areas where the pads need to stick.

Do not delay defibrillation unnecessarily simply because the casualty or surrounding area is wet.

The important thing is that the pads make good contact with the skin and nobody is touching the casualty during shock delivery.

If there is excessive chest hair

AED pads need good contact with the skin.

If excessive chest hair prevents the pads from sticking, quickly remove enough hair from the pad positions if suitable equipment is available.

Do not routinely shave every casualty’s chest.

Do not introduce an unnecessary delay.

Medication patches

If a medication patch is located where an AED pad needs to be placed, remove the patch and wipe the area before applying the AED pad.

Wear gloves if available.

Pacemakers and implanted devices

You may be able to see or feel a small lump under the skin, usually on the upper chest.

Do not place an AED pad directly over an implanted device.

Position the pad slightly away from it while maintaining the general pad position shown by the AED.

Do not withhold AED treatment because someone has a pacemaker or another implanted cardiac device.

Step 10: Attach the AED Pads

Remove the backing from the electrode pads and attach them firmly to the casualty’s bare chest.

Follow the pictures printed on the pads or AED.

For an adult, the usual arrangement is:

one pad on the upper right side of the chest, below the collarbone
the other pad on the left side of the chest, positioned lower and towards the side

Press the pads firmly onto the skin.

Many AEDs use pre-connected pads. If the pads need to be connected to the AED, follow the device instructions.

Continue CPR while pads are being attached

If more than one rescuer is available, CPR should continue while somebody else prepares the chest and attaches the AED pads.

This reduces unnecessary interruptions to chest compressions.

Step 11: Let the AED Analyse the Heart Rhythm

Once the pads are attached, the AED will analyse the casualty’s heart rhythm.

The device will tell you when this is happening.

At this point:

Nobody should touch the casualty.

Clearly tell everyone:

“Stand clear.”

Look around and make sure nobody is touching them.

Movement during rhythm analysis can interfere with the AED’s assessment.

Step 12: Deliver a Shock if the AED Tells You To

The AED will decide whether a shock is required.

You do not make this decision.

If the AED identifies a shockable heart rhythm, it will prepare to deliver a shock.

There are two common types of AED.

Semi-automatic AED

A semi-automatic AED will tell you that a shock is advised and instruct you to press the shock button.

Before pressing it:

make sure nobody is touching the casualty
clearly say “Stand clear”
visually check that everybody is clear

Then press the shock button when instructed.

How to Use an AED Step-by-Step UK Guide — #image_title

Fully automatic AED

A fully automatic AED delivers the shock itself after giving a warning.

Listen carefully to its instructions and make sure nobody is touching the casualty when the shock is delivered.

Can an AED Shock Someone Who Doesn’t Need It?

An AED analyses the casualty’s heart rhythm before deciding whether a shock is appropriate.

If the device does not identify a shockable rhythm, it will not instruct a semi-automatic AED user to deliver a shock, and a fully automatic AED will not deliver one.

You do not need to recognise the heart rhythm yourself.

Follow the AED’s instructions.

Step 13: Immediately Restart CPR

After a shock has been delivered:

Immediately restart CPR.

Do not stop to check for a pulse.

Do not wait to see whether the shock has “worked”.

Resume chest compressions immediately and continue following the AED instructions.

After a period of CPR, the AED will tell you to stop while it analyses the heart rhythm again.

Make sure nobody touches the casualty during each analysis.

What if the AED Says “No Shock Advised”?

A “no shock advised” message does not necessarily mean that the casualty is recovering.

It means the AED has not detected a heart rhythm that should be treated with a shock at that time.

If the casualty remains unresponsive and is not breathing normally:

Immediately resume CPR.

Continue following the AED prompts.

The device will analyse the heart rhythm again at appropriate intervals.

When Should You Stop CPR and AED Treatment?

Continue CPR and follow the AED prompts until:

the ambulance service or another appropriate healthcare professional takes over
the casualty shows clear signs of life and starts breathing normally
you become physically unable to continue
continuing would put you in danger

If the casualty begins breathing normally, follow the instructions provided by the emergency services and continue monitoring them.

Leave the AED pads attached unless instructed otherwise.

Can Anyone Use an AED?

Yes.

Resuscitation Council UK states that anyone can use an Automated External Defibrillator.

You do not need a certificate or formal qualification before using one during a cardiac arrest.

The AED is specifically designed to guide the rescuer through the process.

This is important because people sometimes hesitate when they see a defibrillator because they believe only a trained first aider, paramedic or healthcare professional is allowed to use it.

That hesitation can delay potentially life-saving treatment.

If someone is in cardiac arrest and an AED is available:

Use it.

Do You Need AED Training?

You do not need previous training before using an AED in an emergency.

However, training is still extremely valuable.

Practical training allows you to become familiar with:

recognising cardiac arrest
calling 999
performing effective CPR
operating an AED
positioning electrode pads
safely delivering a shock
working with other rescuers
responding confidently under pressure

Using a training AED in a controlled environment can make the equipment feel much less intimidating.

The aim of training is not to give you permission to use an AED.

It is to give you the skills and confidence to act quickly when somebody needs you.

Can You Use an AED on a Child?

Yes.

AEDs can be used on children.

However, the appropriate pads, child mode and pad positioning depend on the child’s age, size and the AED being used.

Some AEDs have:

paediatric electrode pads
a child key
a child button or switch
another system that reduces the energy delivered

If a child is in cardiac arrest, do not delay essential resuscitation while searching indefinitely for specialist equipment.

We will cover the differences between adults, children and babies in our separate guide to using an AED on a child or baby.

Is It Safe to Use an AED on a Wet Surface?

An AED can generally be used when a casualty is lying on a wet or conductive surface.

Do not unnecessarily delay defibrillation solely because the ground is wet or metallic.

Dry the casualty’s chest where necessary so the electrode pads stick correctly.

As with every AED use, make sure nobody is touching the casualty when the device analyses the rhythm or delivers a shock.

If there is a specific environmental hazard that makes the scene unsafe, address the immediate danger first.

Can You Use an AED on a Pregnant Casualty?

Yes.

Pregnancy is not a reason to withhold CPR or AED treatment from someone in cardiac arrest.

Use the AED and follow its instructions.

Can You Use an AED if the Casualty Has a Pacemaker?

Yes.

Do not withhold defibrillation because somebody has a pacemaker or implanted cardiac device.

Avoid placing the electrode pad directly over the device if you can identify it.

Then continue following the AED prompts.

What if There Is More Than One Rescuer?

Cardiac arrest response is easier when people work together.

If several people are present, allocate tasks.

For example:

Person 1: Call 999 and use speakerphone.

Person 2: Start CPR.

Person 3: Retrieve the AED.

When the AED arrives, one person can continue CPR while another switches it on and prepares the pads.

The aim is to minimise interruptions to chest compressions while getting the AED attached as quickly as possible.

Why Is an AED So Important During Cardiac Arrest?

Cardiac arrest means the heart has stopped pumping blood effectively around the body.

Some cardiac arrests involve an abnormal electrical rhythm that can potentially be corrected by defibrillation.

CPR helps maintain some blood flow to the brain and other vital organs.

An AED can analyse the heart rhythm and, where appropriate, deliver the electrical shock needed to help restore an effective rhythm.

These interventions work together.

Call 999. Start CPR. Use an AED as soon as possible.

Resuscitation Council UK states that bystander CPR and AED use can increase the chances of survival from out-of-hospital cardiac arrest by two to four times.

How to Use an AED: Remember the Essentials

If you remember nothing else from this guide, remember:

Unresponsive? Call 999 immediately.

Not breathing normally? Start CPR.

AED available? Switch it on and follow its instructions.

Nobody touches the casualty during rhythm analysis or shock delivery.

Shock advised? Stand clear and deliver the shock as instructed.

Shock or no shock? Immediately restart CPR.

Keep following the AED prompts until professional help takes over or the casualty shows clear signs of life.

And most importantly:

Anyone can use an AED.

Learn CPR and AED Skills Practically

Reading about how to use an AED is useful, but practical training gives you the opportunity to actually perform CPR, attach AED pads and respond to the device’s instructions.

First Aid and Safety Training includes practical CPR and AED skills within our regulated workplace first aid courses.

Our Emergency First Aid at Work course covers essential emergency first aid skills including CPR and AED use.

For organisations requiring more comprehensive workplace first aid training, our First Aid at Work course develops a broader range of practical skills.

We also provide onsite first aid training across the North East for businesses and organisations that want to train groups at their own premises.

If you are unsure which course is appropriate for your workplace, contact First Aid and Safety Training and we can help.

You can also view our South Shields training location and customer reviews on Google.

Real Skills, Real Confidence.