What Is CPR and How Does It Work?

CPR, or cardiopulmonary resuscitation, is a life-saving technique used when someone is not breathing normally. Its purpose is simple but vital: to keep oxygen-rich blood circulating around the body until professional help arrives.

How CPR Keeps the Body Alive

During CPR, you push down firmly on the chest. This action squeezes the heart, forcing blood out of it and around the body. Although CPR does not restart the heart, it helps maintain circulation to the brain and other vital organs.

The heart itself is divided into two sides:

• The right side pumps blood to the lungs, where it picks up oxygen.
• The oxygen-rich blood then returns to the left side, which pumps it around the body through the arteries.

This continuous cycle supplies oxygen to the organs and tissues throughout your life. The heart automatically adjusts its speed, beating faster during exercise and slowing when you rest.

What Happens in Cardiac Arrest

The heart beats because it produces small electrical impulses from its natural pacemakers. These signals cause the heart muscle to contract in a coordinated way.

However, problems can occur. For example:

• A blockage can reduce the supply of oxygen-rich blood.
• The heart can enter cardiac arrest, where it stops beating effectively.

In around 85–90% of cardiac arrests, the heart goes into a rhythm called ventricular fibrillation (VF). In VF, the heart muscle twitches or quivers instead of pumping, meaning no blood is circulated.

Why CPR and Defibrillation Are Essential

When the heart is in VF, CPR is used to manually pump blood by pressing on the breastbone and compressing the heart. This keeps oxygen moving around the body but does not restart the heart.

The only way to restart the heart is with a defibrillator. A defibrillator delivers a controlled electrical shock designed to stop the abnormal rhythm and allow the heart to resume a normal beat. Paramedics may also give medications to support recovery.

When to Start CPR

CPR may sound technical, but the decision to start is very simple.

You do not need to know what the heart is doing.

If a person is:

• Unresponsive, and
• Not breathing normally

Then CPR must be started immediately.

Why Your Actions Matter

Survival rates following cardiac arrest are strongly influenced by what you do:

• No CPR: Survival rate is around 4.3%
• Chest compressions only: Survival increases to around 7.7%
• Full CPR (compressions and breaths): Survival rises to approximately 13.6%

These figures show a clear message: taking action saves lives.

Key Message

You do not need medical knowledge to save a life. If someone is not breathing, start CPR immediately. Chest compressions keep blood flowing, and early defibrillation gives the heart the chance to restart.

Doing something is always better than doing nothing.