How to perform CPR correctly

Emily Osborne Emily Osborne Regional Health and Safety Trainer at Nuffield Health
Knowing CPR is a skill that can save someone’s life until the emergency services arrive. Unfortunately, most of us don’t know how to perform this essential skill confidently.

In this article, Nuffield Health’s Regional Health and Safety Instructor Emily Osborne gives step-by-step instructions on how to stay calm and perform CPR correctly in the event of an emergency.

What is CPR?

CPR is an acronym that stands for ‘cardiopulmonary resuscitation’. In practice, this refers to the manual resuscitation of the heart when it has stopped beating effectively (cardiac arrest).

CPR involves performing a combination of chest compressions and rescue breaths to get blood and oxygen pumping in and out of the heart again.

Unfortunately, NHS data suggests that under 3 in 10 people know how to, or feel confident delivering CPR. Knowing how to perform CPR can be the difference between saving someone’s life and them passing away before medical assistance arrives.

When should you give CPR?

You should perform CPR on someone if:

  • They are unresponsive
  • They have no pulse
  • They aren’t breathing at all
  • They aren’t breathing properly

When should you not give CPR?

You should cease or not attempt CPR if:

  • Doing so would put you in immediate danger
  • A healthcare professional tells you to stop
  • You become exhausted and cannot effectively continue
  • The casualty shows signs of life, wakes up, communicates with you, opens their eyes, or starts moving again

What to check for before you start CPR

Always start by checking the casualty and assessing whether they require CPR. You can do this by following the following steps and keeping the acronym ‘DRAB’ in your head:


Before you start, quickly check the immediate area to make sure you, the casualty, and any bystanders are free from danger.


Gently shake the casualty around the upper chest area to check for a response. You can also ask them a simple question like “are you okay?”.

If they respond, keep them still and try to work out what has happened before help arrives.


If they do not respond, gently tilt their head back and lift their chin to open their airway. 


Before you attempt CPR, you should assess whether or not the casualty is breathing normally. 

Never avoid CPR because the casualty is breathing. Instead, assess the quality of their breathing.

If you’re not sure whether they’re breathing properly, consider the following:

  • Are they barely breathing?
  • Is their breathing very shallow?
  • Are they taking infrequent, gasping breaths?

If you are in any doubt about any of the above, you should prepare to start CPR.

How to perform CPR on an adult

1. Send for a defibrillator and call 999

Before performing CPR, make sure you have been sent for a defibrillator and someone has called 999 and requested an ambulance.

Defibrillators are incredibly effective. If used within the first minute of recognising a cardiac arrest, success rates can be as high as 90%. For every minute that is lost between the onset of the cardiac event and using the defibrillator, survival rates drop by up to 10%.

Unfortunately, data suggests that they are used in just 10% of out of hospital cardiac arrests.

2. Start chest compressions

To start chest compressions:

  • Place the heel of one hand in the centre of the chest (lower half of the sternum), place your other hand on top and interlock fingers
  • Keep your arms straight and position yourself vertically above the casualty's chest
  • Press down on the chest, aiming to reach a depth of 5 to 6cm 
  • After each compression. release all the pressure on the chest, without losing contact between your hands and the breastbone (chest compression)
  • Repeat chest compressions at a rate of 100—120 per minute with as few interruptions as possible.

3. Give rescue breaths (if trained and confident)

If you are trained to do so, after 30 compressions, open the airway again and give 2 rescue breaths before returning to chest compressions.

See below for more information on how to correctly give rescue breath CPR:

  • Pinch the soft part of the nose closed. Allow the mouth to open, but maintain chin lift
  • Take a normal breath and seal your lips around the casualty's mouth
  • Blow steadily into the mouth while watching for the chest to rise. Remember that you are trying to mimic a normal breath
  • Keeping the airway open, take your mouth away from the casualty and watch for the chest to fall as air comes out
  • Take another normal breath and blow into the casualty's mouth once more to achieve a total of 2 rescue breaths. Do not interrupt compressions by more than 10 seconds to give 2 breaths
  • Return your hands without delay to the centre of the chest and give another 30 chest compressions
  • Continue with chest compressions and rescue breaths at a ratio of 30:2.

4. If a defibrillator arrives

  • Switch on the AED immediately and follow the voice prompts:
  • Attach the leads to the AED if necessary and attach the pads to the casualty bare chest (do this while your helper performs CPR)
  • You may need to towel dry or shave the chest so the pads stick properly to the surface of the skin. Only shave excessive hair and don't delay defibrillation if a razor is not immediately available
  • Peel the backing from one pad at a time and place firmly in position, following the instructions on the pads
  • Place one pad below the casualty's right collarbone. Place the other pad around the casualty's left side, over the lower ribs
  • DO NOT remove the pads if you have placed them the wrong way around — the AED will still work
  • While the AED analyses the rhythm — stop CPR and make sure no one touches the casualty.

If a shock is advised, deliver shock:

  • Make sure that nobody is touching the casualty.
  • Push the shock button as directed (fully automatic AEDs will deliver the shock automatically).
  • Immediately restart CPR at a ratio of 30:2.
  • Continue as directed by the voice/visual prompts.

If a shock is NOT advised:

  • Immediately restart CPR at a ratio of 30:2.
  • Continue as directed by the voice/visual prompts.

How to give chest compressions

  1. Place the heel of one hand at the centre of the person's chest, between the nipples.
  2. Place your other hand on top of the first, interlocking your fingers
  3. Keep your arms straight and position your shoulders directly above your hands
  4. Push down hard and fast, aiming for a depth of about 2 inches. Performing CPR is a life saving act, so don’t be afraid of applying ‘too much’ pressure
  5. Perform compressions at a rate of 100 to 120 compressions per minute, or two per second
  6. Allow the chest to recoil fully between compressions
  7. If there is more than one person actively assisting the casualty, take turns giving chest compressions to avoid fatigue.

Are chest compressions enough?

The level of CPR you can provide to an individual will depend on your confidence and training level.

If you are trained to give rescue breath CPR, you should do so in all instances. This method of CPR is particularly important for drowning casualties and children who are found unresponsive.

If you aren’t trained or you are unable or unwilling to give rescue breath CPR, giving chest compression CPR is better than doing nothing.

Common mistakes to avoid

  • Not pressing hard enough: don’t worry about applying ‘too much’ force with chest compressions
  • Incorrect hand positioning: place your hands over the centre of their chest between the nipples at the bottom of the sternum, avoid hand positioning over the stomach as you will compress the stomach causing regurgitation of the stomach content.
  • Compressing too slowly: make sure you are applying between 100 and 120 compressions per minute
  • Avoiding rescue breaths: if you are trained and confident enough to do so, do not avoid incorporating rescue breaths
  • Stopping too soon: CPR is about manually pumping oxygen from the heart. It’s crucial that you continue to administer CPR until emergency help arrives or the casualty shows signs of life.

How to perform CPR on a child or infant

Performing CPR on a child or infant (The UK Resuscitation Council defines a child as anyone between the ages of 1 and 18 and an infant as a baby under the age of 1) is slightly different. There are a few minor adjustments to the adult guidance above that help make performing CPR more tailored to children and infants.

How to perform CPR on a child

  1. Give five initial rescue breaths before starting chest compressions
  2. When you start chest compressions, do not compress the chest by more than 1/3 of its depth. This should not exceed 5cm.
  3. Use one or two hands to apply pressure to the chest as you would do an adult.

How to perform CPR on an infant

  1. Give five initial rescue breaths before starting chest compressions
  2. When you start chest compressions, do not compress the chest by more than 1/3 of its depth. This should not exceed 4cm.
  3. Use one or two fingers to apply pressure to the infant’s chest. Performing CPR on an infant requires a lot less pressure than an older child, so using your fingers should feel adequate.

What are some signs that CPR is working?

You may find that a pulse returns, or the person begins to show signs of breathing again whilst you are performing CPR. They may also begin responding to stimuli. If the casualty starts to show signs of life (regaining consciousness or actively trying to communicate verbally or physically), stop CPR and reassess the casualty to confirm the casualty is now breathing for themselves and conscious.

It’s important to know that there are no definitive signs that CPR has worked or is working.

Your role in administering CPR is to manually keep the flow of oxygen going around the body until the emergency services arrive. Do your best and do not stop until the emergency services arrive or instruct you to cease.

Should I perform CPR if I’m not trained?

To perform CPR, all you need to know are the basics.

Even if you’re not trained, you should be able to administer chest compression CPR. Familiarising yourself with the techniques involved will help build confidence and could save someone’s life.

I’m apprehensive about giving CPR…

Administering CPR is all about knowledge and confidence.

If you are able to, enlisting in a first aid or CPR training course can help give you the confidence.

Build confidence with a first aid course

If you aren’t confident performing CPR and want to learn more, we strongly recommend signing up to a first aid course.

A number of organisations offer short courses that include specific CPR training, including St John’s Ambulance and the British Red Cross.

Last updated Tuesday 28 May 2024

First published on Tuesday 28 May 2024