Unconscious and not breathing: CPR

If the casualty is not breathing, you should immediately call an ambulance and commence cardio-pulmonary resuscitation (CPR). In this unit we explain how to perform CPR.

How does CPR work?CPR Training

All the cells in your body require oxygen to survive. They also require a good supply of nutrients and the rapid removal of waste products. Oxygen and nutrients are carried around the body in your blood, which is pumped by your heart.

In your lungs, oxygen enters your blood stream and carbon dioxide (a waste product) is removed in a process known as gas exchange.

A “cardiac arrest” is when your heart stops beating. This is not the same as a “heart attack”, although a heart attack may lead to a cardiac arrest. There are numerous causes of cardiac arrests, including:

  • A disturbance in the heart rhythm
  • Drugs/poisoning
  • Heart disease / a heart attack
  • Traumatic injury/blood loss
  • Anaphylaxis

If a cardiac arrest occurs, blood will stop circulating around the body. Breathing will also cease as well though it may not stop completely for several minutes.

Without a supply of oxygen, the cells in the body start to die. Brain cells are incredibly sensitive, after about 4 – 5 minutes of no oxygen brain cells will begin dying leading to brain damage and death.

The purpose of CPR is to keep oxygenated blood flowing around the body to keep the vital organs alive. CPR itself will not restart someone’s heart, it just keeps them alive until a defibrillator arrives. A defibrillator is a device which delivers an electrical shock to the heart to restart it.

How to perform CPR on an adult

You do not need to check for a pulse, as this often wastes valuable time. If a public defibrillator (AED) is available, then it should be sent for immediately.

Once you’ve found someone isn’t breathing, you should start CPR by administering 30 chest compressions. Interlock your hands and place them in the middle of the person’s chest (over the sternum / breastbone) and push down 30 times. You should aim for a depth equal to a third the depth of their chest.

After 30 chest compressions, you should give 2 rescue breaths. Tilt the casualty’s head backwards, make a seal over their mouth and breath in twice. Each breath should only last about one second so as not to over inflate their lungs.

You should aim for a rate of 100 – 120 chest compressions a minute.

Young Woman Performing Cardiopulmonary Resuscitation

If you wish, you can attempt two ‘rescue breaths’ after every 30 chest compressions. Tilt the casualty’s head backwards, make a seal over their mouth and blow in for approximately one second. However these are optional and chest compressions are the most important component of CPR.

Only stop CPR if:

  • The casualty shows signs of life: coughing, breathing etc.
  • You are asked to stop by a healthcare professional (ambulance crew etc.)
  • You become too exhausted to continue
  • The situation suddenly becomes too dangerous

Ideally, you should only carry out CPR for a couple of minutes before swapping with someone else. This is to ensure that the chest compressions remain effective

CPR video

Watch the following video which demonstrates CPR on an adult patient.



John Furst

JOHN FURST is an experienced emergency medical technician and qualified first aid & CPR instructor. John is passionate about first aid and believes everyone should have the skills and confidence to take action in an emergency situation.

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