If you've ever watched a hospital show on TV, you've probably seen cardiopulmonary resuscitation (say: kar-dee-o-pul-muh-nair-ee rih-suh-sih-tay-shun). It's called CPR for short and it saves lives. Let's find out how it works.

What Is CPR?

Cardio means "of the heart" and pulmonary means "of the lungs." Resuscitation is a medical word that means "to revive" — or bring back to life. Sometimes CPR can help a person who has stopped breathing, and whose heart may have stopped beating, to stay alive.

People who handle emergencies — such as police officers, firefighters, paramedics, doctors, and nurses — are all trained to do CPR. Many other teens and adults — like lifeguards, teachers, childcare workers, and maybe even your mom or dad — know how to do CPR, too.

The person giving CPR — called a rescuer — follows 3 main steps, which are known as C-A-B:

1. C: do chest compressions
2. A: check the airway
3. B: do rescue breathing

Chest Compressions

Someone giving CPR (the rescuer) will probably use both hands, one placed over the other, to press on the person's chest many times in a row to move blood out of the heart that has stopped beating.

These are called chest compressions and they help move oxygen-carrying blood to the body's vital organs — especially the all-important brain. A person who goes too long without oxygen reaching the brain will die.

In between each compression the hands are lifted off the chest to let the chest go back to where it was. This allows blood to flow back toward the heart. In this way, the rescuer can keep the person alive by continuing to supply blood and oxygen to the brain and the rest of the body, until emergency help — like the paramedics — arrives to take the person to a hospital.

Checking the Airways

After 30 compressions have been completed, the rescuer checks the airway to see if the person is breathing.

Rescue Breathing

If the person is not breathing, TWO rescue breaths are given. This is called artificial respiration (say: ar-tuh-fih-shul res-puh-ray-shun), mouth-to-mouth rescue breathing, or mouth-to-mouth resuscitation.

To do this, a rescuer puts his or her mouth over the other person's open mouth and blows, forcing air into the lungs. (Ideally the rescuer will use a special mask so that their mouths don't actually have to touch.) Rescue breathing helps to move oxygen, which everyone needs to live, down into the lungs of the person who isn't breathing. Chest compressions should start again right after the two breaths are given.

Instead of doing mouth-to-mouth rescue breathing, professional rescuers — such as paramedics — will provide artificial breathing for someone by using a mask with a special hand pump connected to an oxygen tank. Doctors in the emergency department will put a tube into the person's windpipe to pump oxygen directly through the tube and into the lungs.

When Should Someone Use CPR?

The steps in CPR (compressions, airway, and breathing) should be used whenever someone is not breathing and when the heart is not beating. After two rescue breaths are given, 30 chest compressions should be started right away.

Someone can stop breathing and/or have cardiac arrest from:

• heart attacks
• strokes (when the blood flow to a part of the brain suddenly stops)
• choking on something that blocks the entire airway
• near-drowning incidents (when someone is underwater for too long and stops breathing)
• a very bad neck, head, or back injury
• severe electrical shocks (like from touching a power line)
• being very sick from a serious infection
• too much bleeding
• severe allergic reactions
• swallowing a drug or chemical

If an emergency happens or someone becomes very sick while you're around, do your best to stay calm. First, try to get the person to respond by gently shaking his or her shoulder and asking, "Are you OK?" If there is no response and you are certified in CPR, you can begin CPR. If you're alone, shout for help or call 911 yourself.

Who Should Know CPR?

Certain people need to know how to perform CPR to do their jobs. Medical professionals — from nurses and doctors to paramedics and emergency medicine technicians — must know CPR. Lifeguards, childcare workers, school coaches, and trainers usually have to learn CPR. Many parents know how to perform CPR on kids in case of emergency. Other adults who have family members with medical conditions such as heart disease sometimes know CPR, too.

Many people — maybe you — might want to learn how to do CPR just in case they need to use it someday. You can never tell when a medical emergency will happen and it feels good to know that you could help. The American Red Cross, American Heart Association (AHA), and the National Safety Council all offer CPR courses. You also might find CPR classes at your local hospital, places of worship, the YMCA, or your school. You're usually ready to take a CPR course and get certified if you are in middle school or above.

Talk with your mom or dad if you'd like to learn how to do it. Knowing CPR can be a real lifesaver!

Reviewed by: Kate M. Cronan, MD
Date reviewed: March 2012