CPR & Cardiac Arrest

Every minute that passes after cardiac arrest without CPR reduces the chance of survival by approximately 7–10%. Without CPR, brain death begins within 4–6 minutes. With immediate bystander CPR, survival rates can double or triple compared to waiting for emergency services. Cardiac arrest causes approximately 350,000 out-of-hospital deaths in the United States annually — and the fundamental skill that changes that outcome is one most adults can learn in under an hour.

This guide covers everything you need to recognise cardiac arrest, start CPR immediately, use an automated external defibrillator (AED), and adapt your technique for children and infants.

What Is Cardiac Arrest

Cardiac arrest occurs when the heart stops pumping blood effectively — usually due to a sudden abnormal heart rhythm (typically ventricular fibrillation). It is different from a heart attack, though a heart attack can cause a cardiac arrest.

Heart Attack	Cardiac Arrest
Blocked blood supply to heart muscle	Heart stops pumping effectively
Person is conscious and may be speaking	Person is unresponsive and not breathing normally
Chest pain, shortness of breath, sweating	Sudden collapse, unresponsiveness
Call emergency services; keep person calm and still	Call emergency services; begin CPR immediately

A heart attack can progress to cardiac arrest. A cardiac arrest requires immediate CPR.

Recognising Cardiac Arrest

Act if you see someone who:

1. Suddenly collapses or becomes unresponsive
2. Does not respond to shouting at them or shaking their shoulders
3. Is not breathing normally — no visible chest rise; gasping is not normal breathing

⚠️ Agonal breathing — occasional gasping or snoring-type breaths — often occurs in the first few minutes after cardiac arrest. This is not normal breathing. If the person is unresponsive and you observe agonal gasping, start CPR.

The Chain of Survival

Survival from cardiac arrest depends on a chain of actions. Each link matters:

1. Early recognition — identifying cardiac arrest without delay
2. Early call for help — calling emergency services immediately
3. Early CPR — maintaining blood flow to the brain while waiting for help
4. Early defibrillation — restoring a normal rhythm with an AED
5. Advanced care — paramedics and hospital treatment

You can perform steps 1–4 as a bystander. Your actions in the first few minutes determine whether the later steps are even possible.

Hands-Only CPR — Adult

For an adult who suddenly collapses, hands-only CPR (chest compressions without rescue breaths) is as effective as CPR with breaths during the first few minutes, and it is what the American Heart Association now recommends for untrained bystanders.

Step 1: Check Safety

Ensure the area is safe for both you and the victim before approaching.

Step 2: Check Response

Tap the person firmly on the shoulders and shout "Are you alright?" or "Can you hear me?"

Step 3: Call for Help

If no response, shout for help immediately. Dial emergency services (999 UK / 911 US / 112 EU). If others are present, point to a specific person: "You — call 999 now."

Step 4: Check Breathing

Look for chest rise for no more than 10 seconds. If the person is not breathing or only gasping, begin compressions.

Step 5: Chest Compressions

1. Kneel beside the person at their chest
2. Place the heel of your dominant hand on the centre of the chest (lower half of the breastbone — sternum)
3. Place your other hand on top, fingers interlocked
4. Keep arms straight and shoulders directly above your hands
5. Compress the chest at least 5 cm (2 inches) — firm, hard pushes
6. Allow the chest to fully recoil between compressions — do not lean on the chest
7. Rate: 100–120 compressions per minute — approximately the tempo of "Stayin' Alive" by the Bee Gees

Push hard and push fast. This is the most common failure mode in bystander CPR — compressions that are too shallow do not circulate blood adequately.

Step 6: Continue Until

• Emergency services take over
• The person shows obvious signs of life (breathing, movement)
• An AED is ready to deliver a shock
• You are physically unable to continue

CPR with Rescue Breaths — Adult (Trained Rescuers)

If you are trained in CPR with rescue breaths, use a 30:2 ratio:

1. 30 chest compressions at the rate above
2. Tilt the head back gently with one hand on the forehead and two fingers lifting the chin
3. Pinch the nose, seal your lips around the mouth, and give 2 rescue breaths — each lasting 1 second, watching for chest rise
4. Return immediately to compressions

If the first breath does not cause chest rise, recheck the head tilt/chin lift before attempting the second breath — do not delay compressions to reposition repeatedly.

Using an AED

An AED (Automated External Defibrillator) delivers an electric shock to reset an abnormal heart rhythm. They are found in airports, shopping centres, sports facilities, and increasingly in public buildings.

⚠️ AEDs are designed to be used by untrained bystanders. They will talk you through every step. Turn it on and follow the voice prompts.

AED Steps

1. Turn on the AED — press the power button or lift the lid
2. Attach the pads as shown in the diagram on the pads:
   • One pad on the upper right chest (below the collarbone)
   • One pad on the lower left side, below the armpit
3. Ensure no one is touching the person — the AED will analyse the rhythm
4. Follow the prompt: If a shock is advised, ensure everyone is clear, then press the shock button
5. Resume CPR immediately after the shock — 30 compressions before rechecking
6. Continue following AED prompts every 2 minutes

AED on hairy chest: If adhesion is poor, a razor (often included with the AED) may be needed. If not available, press the pads firmly and proceed.

AED near a pacemaker: Avoid placing a pad directly over a visible pacemaker lump under the skin — position it at least 8 cm away.

Wet patient: Quickly dry the chest before applying pads.

CPR for Children (1–8 Years)

Use one or two hands rather than two — smaller children need less force:

1. Use one or two hands on the lower half of the breastbone
2. Compress one-third of the chest depth (approximately 5 cm)
3. Ratio: 30:2 with rescue breaths for trained rescuers; hands-only for untrained
4. AED: Use paediatric pads/paediatric mode if available; adult pads can be used if paediatric pads are unavailable — place one on the chest and one on the back

⚠️ Compression depth matters just as much in children as in adults. Compressions that are too shallow do not circulate blood effectively. Do not hesitate to push firmly enough to achieve one-third chest depth.

CPR for Infants (Under 1 Year)

Infant technique is different:

1. Lay the infant on a firm, flat surface
2. Use two fingers (index and middle) on the centre of the chest, just below the nipple line
3. Compress one-third of the chest depth (approximately 4 cm)
4. Rate: 100–120 compressions per minute
5. Rescue breaths: Cover both the mouth and nose with your mouth; give small puffs — watch for chest rise; 2 breaths after every 30 compressions
6. AED: Use paediatric pads and mode if available; if not, one pad on the chest and one on the back

When to Stop CPR

Continue CPR until:

• Qualified medical personnel take over
• The person starts breathing and showing clear signs of life
• You are physically unable to continue (extreme exhaustion)
• A qualified health professional declares that continuation is futile
• A valid "Do Not Resuscitate" (DNR) order is known and confirmed

Starting CPR and then stopping because you are unsure is far better than never starting at all.

Quick Reference

Element	Adult	Child (1–8)	Infant (<1 yr)
Compression site	Centre of chest	Lower sternum	Centre chest, below nipple line
Hand position	Two hands	One or two hands	Two fingers
Compression depth	5–6 cm	~5 cm (1/3 chest)	~4 cm (1/3 chest)
Rate	100–120/min	100–120/min	100–120/min
Hands-only CPR	Yes (untrained)	Yes (untrained)	No (breaths needed)
Breaths:compressions	2:30	2:30	2:30
AED	Yes	Paediatric preferred	Paediatric preferred

This guide provides general CPR information based on current resuscitation guidelines. It does not replace hands-on certified CPR training. Take an accredited CPR course from a recognised organisation such as the Red Cross, American Heart Association, or St John Ambulance. Guidelines are updated periodically — confirm you are using the most current recommendations.