A cardiac arrest can happen suddenly, and knowing what to do could make a vital difference. From recognising the signs to starting CPR and using a defibrillator, refresh your knowledge so you feel ready to act.
If someone suddenly collapses in front of you, would you know what to do?
A cardiac arrest is a medical emergency that requires immediate action. It happens when someone's heart stops, meaning blood is no longer being pumped effectively around the body.
Someone experiencing a cardiac arrest will be unresponsive and won't be breathing normally. They may take slow, irregular or noisy gasps, but this isn't normal breathing.
Recognising what's happening, calling for emergency help, starting CPR and using an automated external defibrillator (AED) as soon as one is available can give someone their best chance of survival.
Cardiac arrest and heart attack aren't the same thing
The terms cardiac arrest and heart attack are sometimes used interchangeably, but they're not the same.
A cardiac arrest happens when the heart stops pumping blood around the body. The person becomes unresponsive and won't be breathing normally.
A heart attack happens when the blood supply to the heart muscle is suddenly blocked. Someone having a heart attack will usually still be responsive and breathing, although a heart attack can lead to cardiac arrest.
Being able to recognise the difference is important because someone in cardiac arrest needs CPR and a defibrillator immediately.
Would you recognise a cardiac arrest?
If someone has collapsed, start by checking whether they respond.
Someone in cardiac arrest may:
- be unresponsive
- not be breathing normally
- take occasional slow, noisy or irregular gasps
- show no movement or signs of life
If someone is unresponsive, call 999 or 112 for emergency help and start CPR.
If another person is with you, ask them to call for an ambulance and bring a defibrillator if one is available nearby. If you're alone, put your phone on speaker so you can speak to the ambulance call handler while beginning CPR. Do not leave the person to look for a defibrillator yourself. If someone else is available, ask them to fetch one while you continue CPR.
CPR: keeping blood moving
CPR stands for cardiopulmonary resuscitation. Chest compressions help keep blood circulating around the body until emergency help arrives or a defibrillator is ready to use.
For an adult, place the heel of one hand in the middle of their chest, put your other hand on top and interlock your fingers if you can. Keeping your arms straight, press down approximately 5–6cm and allow the chest to come back up after each compression.
Aim for 100–120 chest compressions per minute. That's roughly the same tempo as the song Stayin' Alive by the Bee Gees, which can help you remember the rhythm.
If you're able to give rescue breaths, give 30 chest compressions followed by two rescue breaths. If you're unable or unwilling to give rescue breaths, continue with chest compressions at a rate of 30 compressions to 2 rescue breaths.
Continue CPR until emergency help takes over, the person starts showing signs of life and begins breathing normally, you're too exhausted to continue, or a defibrillator is ready to use.
What is an AED?
An automated external defibrillator, or AED, is a device designed to help someone experiencing sudden cardiac arrest.
It analyses the person's heart rhythm and, if appropriate, delivers a controlled electric shock. Depending on the device, it may deliver the shock automatically or tell the person using it when to press a button.
You don't need to be a healthcare professional or to have received training to use an AED. Defibrillators are designed to guide the user through what to do using visual and/or spoken instructions.
You'll find them in many workplaces and public places, including schools, gyms and community spaces.
Don't be afraid to use a defibrillator
Seeing an AED during an emergency might feel daunting, particularly if you've never used one outside a training environment.
But don't let uncertainty stop you from acting.
Once the AED arrives, switch it on and follow its instructions. The person's chest will need to be exposed so the pads can be attached to bare skin in the positions shown on the pads.
Continue CPR while someone else prepares the AED where possible. Once the pads are attached, the device will analyse the person's heart rhythm and tell you when to stop CPR and make sure nobody is touching them.
The AED will only advise or deliver a shock when its analysis determines one is needed. After a shock – or if no shock is advised – follow the device's instructions and continue CPR when told to do so.
Do you know where your nearest AED is?
Knowing how to use a defibrillator is valuable, but knowing where to find one matters too. If an AED is registered on The Circuit, the call handler will know if it is available for use and tell you where it is.
If there's an AED in your workplace, take a moment to find out:
- where it's located
- how you access it
- whether colleagues know where it is
- who is responsible for checking and maintaining it
If you're responsible for an AED, make sure you follow the manufacturer's instructions for routine checks and maintenance. This may include checking the device's status indicator, battery and electrode pad expiry dates.
In an emergency, if you don't know where the nearest public access defibrillator is, the ambulance call handler can help direct someone to one.
Why acting quickly matters
Out-of-hospital cardiac arrest has a low survival rate. Data published by Resuscitation Council UK has previously shown that fewer than one in 12 people in England survived to 30 days following an out-of-hospital cardiac arrest.
But there are actions people nearby can take while an ambulance is on its way.
Early CPR helps keep blood circulating, delivering oxygen to vital organs, while using an AED as soon as possible can help restore a normal heart rhythm in someone whose cardiac arrest has a shockable rhythm.
Remember Phone, Push, Press:
Phone – call 999 or 112 for an ambulance.
Push – start CPR.
Press – use a defibrillator as soon as one is available, following its instructions.
These are simple actions to remember in a situation where every moment matters.
Keep your confidence as well as your skills
If you're already a trained first aider, you may have practised CPR and using an AED during your course. But it's worth asking yourself: if someone collapsed today, how confident would you feel putting those skills into practice?
Take opportunities to refresh your knowledge. Familiarise yourself with the AED in your workplace, revisit CPR guidance and make sure you know how to summon emergency help.
You don't have to know everything before you act. The ambulance call handler and AED can both guide you through what to do.
What matters is recognising the emergency and taking action.
Be ready to act
A cardiac arrest can happen without warning.
Knowing how to recognise it, calling 999 or 112, starting CPR and using an AED can give someone the best possible chance while emergency help is on its way.
So, next time you see a defibrillator in your workplace or community, don't simply walk past it.
Take a moment to notice where it is.
One day, knowing could make all the difference.
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