Cardiopulmonary resuscitation (CPR) is used in a range of emergencies, including heart attack, choking, and drowning. In these situations, the person is unconscious and has stopped breathing. Before you begin CPR on anyone, however, you should call for immediate medical assistance.

The goal of CPR is to restore circulation. If you are unable to find a pulse in an unconscious person, heart compression is necessary to restore circulation. These compressions must be coordinated with mouth-to-mouth resuscitation: the breathing delivers air to the lungs; heart massage pumps the oxygenated blood to the brain and other parts of the body.

To begin CPR, place yourself at right angles to the person's chest. Find the base of the breastbone at the center of the chest where the ribs form a V. Position the heel of one hand on the chest immediately above the V; with the other hand, grasp the first hand from above, intertwining the fingers. Shift your weight forward and upward so that your shoulders are over your hands; straighten your arms and lock your elbows.

To begin pumping the heart, shift your weight onto your hands to depress the person's chest 1 and 1/2 to 2 inches. Compress the chest 15 times in a slow, even rhythm. After 15 compressions, breathe for the person twice. Establish a regular rhythm of compressing and breathing, counting aloud. If help does not arrive in 1 minute and a phone is readily available, call for an ambulance immediately then resume CPR.