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How to perform CPR/Defibrillation

Would you know how to use a public access Defibrillator in an emergency? (Or even know where to find one)?

A cardiac arrest is when your heart suddenly stops pumping blood round your body, commonly because of a problem with electrical signals in your heart. When your heart stops pumping blood, your brain is starved of oxygen. This causes you to fall unconscious and stop breathing. 

The most common cause of a cardiac arrest is a life-threatening abnormal heart rhythm called ventricular fibrillation (VF). Ventricular fibrillation happens when the electrical activity of your heart becomes so chaotic that the heart stops pumping and quivers or ‘fibrillates’ instead.

It can sometimes be corrected by giving an electric shock through the chest wall, by using a device called an AED or defibrillator. 

An AED (Automated External Defibrillator) can be used by any member of the public (using a public access defibrillator) and does not require any training as the AED unit will provide self-explanatory voice commands. 

Approximately 30,000 people suffer from cardiac arrests at home or in public places, in the UK each year, not counting cardiac arrests that happen in UK hospitals on a daily basis. This figure equates to around 82 cardiac arrests taking place every single day.

This shocking statistic has led to an increase in the number of lifesaving defibrillators being placed in public locations such as schools, places of work, train stations and airports, but the question is, would you know how to use an AED in an emergency situation?

So what are the signs of someone having a cardiac arrest? 

There are usually no symptoms before a cardiac arrest and, without immediate treatment, it will be fatal. If someone is in cardiac arrest:

  • they won’t be conscious
  • they won’t be responsive
  • they won’t be breathing, or breathing normally (i.e. at least 2 normal breaths every 10 seconds).


This is a medical emergency. Immediately call 999 for an ambulance, start CPR and send someone to locate and bring an AED to you.

Immediate CPR (aka chest compressions) is critical to keep oxygen circulating around the body and must not be delayed while an AED is located and/or until the emergency services arrive.

If you do have access to a defibrillator, the time that it takes to find it and use it correctly on a patient can also have a huge impact on the outcome of the emergency and whether the cardiac arrest has caused significant and life changing damage to their mental and physical health.

Without immediate medical treatment, a shocking 90 – 95% of sudden cardiac arrest victims will sadly die. However, if a defibrillator is used and CPR is performed within 3 to 5 minutes, their chance of survival will dramatically increase from 6% to 74%. Yet, survival does not necessarily mean that the cardiac arrest has not caused lifesaving damage to the patient. A cardiac arrest deprives your brain of oxygen which can lead to problems with basic cognitive functions such as memory and attention not to mention the psychology trauma of the ordeal.

Finding a Defibrillator

Image of a community defibrillator

Many public places in the UK now have an AED as part of their first aid equipment and they are usually wall-mounted within a small portable plastic box stored and marked with a green AED sign above. Public AEDs are often registered with the ambulance service so when you call 999 the ambulance service can direct you or someone else to its location. 

There are also phone apps that can show you the nearest location of an AED. The GoodSAM app is perhaps the best known example and GoodSAM claims to be the world’s largest AED registry so you can use it in many countries. You can also add AEDs to the registry by simply taking a photo on your phone and uploading it. This could provide vital information to someone else at another time. Learn more about GoodSAM and download it from: https://www.goodsamapp.org/patient

Be aware if there is a GoodSAM Responder in the vicinity (i.e. a trained first aider or medical personnel already registered with GoodSAM), they may also be alerted by the ambulance service to come assist you while an ambulance is enroute.

What to do at the scene:

If you’re the first person on the scene of a cardiac arrest, you need to call 999 and start CPR immediately. If more people arrive, ask them to locate a defibrillator while you continue CPR.

Follow these simple steps (DR ABC):

  1. D– Check for any danger to yourself. If the scene is unsafe do not proceed until it is safe to do so. You will not be able to help the patient if you come to harm.
  2. R – Check for response. Call out and gently shake the patient.
  3. A – If no response, place the patient on their back and tilt their head back / lift up their chin to open the airway. Check for any obvious obstructions that can easily be removed but do not insert fingers into patient’s mouth. If appropriate turn the patient onto their side briefly to allow any fluids gravitate away from their mouth. 
  4. B – Place ear over patient’s mouth and watch for chest rise / listen for at least 2 normal breaths every 10 seconds. If absent, call 999 and start CPR. 
  5. C – Start giving 30 compressions by pumping the chest. Put the heel of one hand on the centre of their chest and interlock your fingers. Begin to pump the chest hard and fast. Don’t worry about pressing down too hard as the chest needs to go down by at least 5cm for CPR to be effective. Aim to deliver 100-120 compressions every 60 secs.
  6. Pinch the nose and cover the victim’s mouth with your mouth and give two rescue breaths* after every 30 compressions. Use a protective face shield if available. 

(* If you are unable or unwilling to provide rescue breaths, continue with compression-only CPR until help arrives.)

Using a Defibrillator:

If you’re lucky enough to find a defibrillator, quickly open it, switch it on and listen to the verbal instructions that will explain exactly what you need to do. If possible do not stop CPR and let someone else prepare the AED for use. 

Listen to the voice command instructions carefully. AEDs can be used on anyone over the age of one. The machine will analyse the patient’s condition automatically, providing you with verbal information and instruction on how to use the machine.

Follow these steps:

  1. Take the pads from the sealed pack and remove or cut through any clothing on the patient’s chest. Wipe away any sweat or wetness.
  2. Remove the backing paper and attach the pads to their chest. (You may need to shave a small patch of chest hair if the pad doesn’t stick, using the razor supplied.)
  3. Place one pad on their upper right side, just below their collarbone as shown on the pad and then place the second on their left side, below the armpit. The pads must be positioned lengthways with the long side in line with the length of their body.
  4. As soon as you have done this, the AED will begin to check the patient’s heart rhythm. Make sure that you or anyone else near to the patient is not touching them and continue to follow the verbal instructions until help arrives.
  5. If the patient becomes responsive place them in the recovery position but leave the AED attached in case they deteriorate and CPR needs to be re-started and/or a further shock is required.

The British Heart Foundation has produced a helpful video on CPR and how to use an AED. Please take time to watch it now so you will feel better prepared to deal with a cardiac arrest emergency should you ever encounter one. https://youtu.be/YbjcCjSNvUY