What is the chain of survival?

During cardiac arrest, a person’s heart stops beating. When this happens, every second counts in what you do to help them survive.

Their best chance of making a good recovery is a series of four actions known as the chain of survival. 

What are the four links in the chain of survival?

As its name suggests, the chain of survival is a critical series of four linked actions designed to help save someone’s life.  

It involves first calling for expert help, then providing CPR followed by early defibrillation to restart the heart, and subsequent post resuscitation care to restore quality of life. These actions are all vital links in the chain.

The four links in more detail

Link 1: Recognising what has happened

The first link in the chain of survival is about recognising that someone has suffered a cardiac arrest, and immediately calling for help.

When someone suffers a cardiac arrest they will collapse. They may make some jerking movements and take gasping breaths as the body attempts to get oxygen into the lungs. They may also start to turn blue from lack of oxygen.

Link 2: Early CPR

Once someone recognises a cardiac arrest and calls 999, the next priority is to start CPR as quickly as possible.

CPR (cardiopulmonary resuscitation) involves chest compressions and, where possible, rescue breaths. Chest compressions help keep blood flowing to the brain and other vital organs while waiting for emergency services.

If you have been trained to give rescue breaths, the recommended approach is 30 chest compressions followed by two rescue breaths.

If you have not been trained, or do not feel able to give rescue breaths, continuous chest compressions are still much better than doing nothing. The 999 call handler can talk you through what to do.

For adults, aim to deliver compressions at a rate of 100–120 per minute, pushing down 5–6cm in the centre of the chest and allowing the chest to rise fully between compressions.

Keep going until help arrives, the person shows signs of recovery, or you are physically unable to continue.

Link 3: Defibrillation

As soon as a defibrillator (AED) is available, switch it on and follow the voice instructions.

The AED will guide you through attaching the pads to the person’s bare chest. It will then analyse the heart’s rhythm and determine whether a shock is needed.

If the AED advises that a shock is needed, make sure nobody is touching the person. Follow the instructions to deliver the shock. Some defibrillators deliver the shock automatically, while others require you to press a button.

After the shock, or if the AED advises that no shock is needed, immediately restart CPR when instructed. Continue following the AED’s prompts until the ambulance service takes over.

A defibrillator does not restart every stopped heart. It delivers an electrical shock when it detects a rhythm that can respond to defibrillation. This is why early CPR and rapid access to an AED are so important.

Link 4: Post resuscitation care

When the ambulance service arrives, they will be able to take over the care of the patient from those who have helped in those vital first few minutes. They may ask you to continue for a minute or so whilst they get their equipment ready. 

Thereafter subsequent post resuscitation care will be administered to restore quality of life.

Why early defibrillation is important

Early defibrillation is crucial in sudden cardiac arrest, as it delivers a life-saving shock to restore the heart’s rhythm. When administered quickly, ideally within the first few minutes, it can dramatically increase survival rates. Combined with effective CPR, it also helps maintain blood flow to the brain, improving the chances of a good recovery.

A defibrillator can directly stop the chaotic electrical activity (ventricular fibrillation) that causes the heart to quiver instead of pump, making rapid treatment essential.