What is CPR?

CPR, the kiss of life, resuscitation, heart massage. These are all words used for Cardiopulmonary Resuscitation (CPR) by the media and general public. These terms can lead to confusion around CPR and what it actually is.Young Woman Performing Cardiopulmonary Resuscitation

In this unit we will introduce the basic science behind CPR.

How does CPR work?

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.

You can learn more about how to use a defibrillator by taking our online defibrillator course

Will the casualty wake up?

Unfortunately this is very unlikely to happen. By doing chest compressions, you are taking over the job of the casualty’s heart (which has stopped) by forcibly compressing it. In effect, you are acting as a life-support machine for the person.

In order for the heart to be restarted, it may require an electrical shock from a defibrillator or drugs given by a paramedic/doctor. CPR on its own is very unlikely to restart someone’s heart.

However, good quality chest compressions will significantly increases the chance of the defibrillator being able to restart the heart.Automated External Defibrillator (AED)

You should only stop doing CPR if:

  • A defibrillator arrives and is about to be used
  • 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 of good quality.

If the casualty does start breathing, you should place them on their side. This will prevent the tongue from blocking their airway, and stop any vomit from traveling into their lungs.

Now that we've covered the basic science behind CPR, the next units will focus on how to perform CPR on an adult, child & infant.

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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