When paramedics rush to the aid of an injured person, they check to see if the person is breathing. If the person's chest is not rising and falling and they cannot feel or hear air being exhaled from the mouth or nose, it is likely that the person is not breathing. Paramedics will ignore broken bones or burns to focus on breathing because there is no time to lose! If breathing stops for more than a few minutes, a life may be lost.

Paramedics can do mouth-to-mouth rescue breathing to force air into the lungs. They can do chest compressions to keep the blood circulating. Cardiopulmonary resuscitation, or CPR, is rescue breathing combined with chest compressions.