What Is CPR and Why Does Circulation Matter?

Cardiopulmonary resuscitation (CPR) is an emergency life-saving procedure performed when a person's heart has stopped beating or they have ceased to breathe. When the heart stops, oxygen-rich blood can no longer reach the brain and vital organs. Irreversible brain damage begins within just 4–6 minutes of cardiac arrest — making rapid CPR intervention one of the most critical actions a bystander can take.

CPR works by manually compressing the chest to circulate blood and deliver rescue breaths to maintain oxygen flow until the heart can be restarted — either spontaneously or through defibrillation. Every minute without CPR reduces the chance of survival by approximately 7–10%; bystander CPR can more than double survival rates.

Understanding the physiology of circulation is the foundation of effective CPR. Learn more in our article: Why CPR Training Saves Lives →

Three Physiological Principles Behind Effective CPR

How to Perform Adult CPR: Step-by-Step

Difficulty Level: Moderate — requires composure and correct technique
Critical Time Window: Begin CPR within 4 minutes of cardiac arrest. Every second counts.

1. Confirm Scene Safety

   Before approaching the victim, ensure the environment is safe for both you and the patient. Hazards such as live electrical sources, traffic, or structural instability must be addressed or the patient must be moved to safety before you begin. Do not become a second casualty.

2. Check for Responsiveness

   Tap the victim's shoulders firmly and call out loudly: "Are you okay? Can you hear me?" If there is no response, shout for help immediately and proceed without delay. Note the time you discovered the patient — this is important information for emergency responders.

3. Call 112 — Or Instruct Someone to Call

   Activate the emergency medical services (EMS) system immediately. If others are present, point to a specific individual and give a clear instruction: "You — call 112 now and report back to me." If alone, call 112 yourself and put the phone on speaker before beginning CPR. Request an AED (automated external defibrillator) if one may be available nearby.

4. Open and Assess the Airway

   Place one hand on the victim's forehead and use two fingers of the other hand to gently lift the chin upward. This head-tilt/chin-lift manoeuvre opens the airway by preventing the tongue from blocking the throat. Look, listen, and feel for normal breathing for no more than 10 seconds. Occasional gasping (agonal breathing) is not normal breathing — proceed with CPR.

   See also: Complete Guide to Adult CPR Technique →

5. Begin Chest Compressions

   Position yourself beside the victim. Place the heel of one hand on the centre of the chest (lower half of the sternum) and interlace the fingers of your other hand on top. With arms straight and shoulders directly over your hands, compress the chest at least 5 cm (2 inches) at a rate of 100–120 per minute. Allow full chest recoil between each compression — do not lean on the chest. Minimise interruptions to compressions.

6. Deliver Rescue Breaths (if Trained)

   After every 30 compressions, deliver 2 rescue breaths. Maintain the head-tilt/chin-lift, pinch the nose closed, and create a complete seal over the mouth. Breathe in slowly over 1 second — enough to see the chest rise visibly. If the chest does not rise, re-check the airway position before attempting a second breath. If rescue breaths are not possible, continue with compression-only CPR at 100–120 per minute.

7. Continue the 30:2 CPR Cycle

   Continue cycles of 30 compressions : 2 rescue breaths without interruption. Rescuer fatigue degrades compression quality rapidly — if a second trained rescuer is available, switch every 2 minutes. Maintain consistent rate and depth throughout. Do not stop to check for a pulse during ongoing CPR unless clear signs of life appear.

8. Use an AED as Soon as Available

   Defibrillation is the most effective intervention for shockable cardiac rhythms such as ventricular fibrillation. When an AED arrives, switch it on and follow the spoken instructions immediately. Continue CPR while the AED is being set up and resume compressions as soon as the AED has delivered its shock (or advised no shock). Do not delay defibrillation — each minute without it reduces survival by 7–10%.

9. Continue Until Professional Help Arrives

   Do not stop CPR until: (a) the victim shows clear signs of life (breathing normally, moving, responding), (b) a qualified medical professional takes over, (c) an AED instructs you to stop, or (d) you are physically unable to continue. Recovery position: If the victim resumes breathing but remains unconscious, place them in the lateral recovery position and continue to monitor airway, breathing, and circulation until paramedics arrive.

Expert CPR Tips: What Most Guides Miss

Critical Mistakes to Avoid During CPR

• Do not compress too shallowly — compressions under 5 cm generate insufficient blood flow to sustain organ perfusion.
• Do not pause compressions to check for a pulse unless clear signs of life emerge — unnecessary interruptions dramatically reduce survival rates.
• Do not tilt the head back excessively — over-extension can close the airway rather than open it. Aim for neutral-to-slight extension.
• Do not blow forcefully into the victim's mouth — slow, controlled rescue breaths (1 second each) prevent gastric inflation and aspiration.
• Do not lean on the chest between compressions — the thorax must fully recoil to allow the heart to refill with blood.
• Do not delay defibrillation — when an AED is available, applying it immediately takes priority even if CPR must be briefly paused.
• Do not stop CPR prematurely — survival is possible even after prolonged resuscitation, particularly in hypothermia cases. Continue until professional help arrives.

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