CPR stands for cardiopulmonary resuscitation, a lifesaving technique that can help someone whose heart has stopped beating or is not breathing properly. CPR can be done on adults, children, and infants, and can be done with one or two rescuers.

CPR requires a basic understanding of anatomy and physiology including heart, lung and airway anatomy. The procedure involves checking for any signs of life, calling for emergency help, inspecting airway and checking for cardiac activity. If necessary, rescue breaths are provided and chest compressions are delivered.

There exists multiple methods to perform CPR, although the basic protocol remains the same. It’s recommended to take a CPR class or online course to learn the proper technique. After becoming certified in CPR, it's important to recertify every two years.

When performing CPR, the rescuer must be aware of how the patient might respond and should take the necessary precautions to protect themselves. The rescuer should take the patient’s temperature and check for pulse or signs of a heart beat, in addition to assessing the patient’s breathing.

When delivering chest compressions, the rescuer should push hard and fast in the center of the chest, pushing back and forth continuously while counting out loud, providing between 100 and 120 compressions per minute. It’s important not to stop compressions unless absolutely necessary.

When providing rescue breaths, the rescuer should tilt the head back, pinch the nose, and give two quick breaths. This should be repeated until the patient resumes breathing on their own.

Using an AED (automated external defibrillator) can be necessary in certain cases of cardiac arrest. AEDs are small portable devices that can deliver a shock to the heart, which can restore a normal rhythm in some cases.

In conclusion, CPR is a lifesaving technique and it is important to learn the proper technique and practice regularly in order to be prepared in a medical emergency. Knowing how to perform CPR can be the difference between life and death.