Choking occurs when the respiratory passage in the throat or windpipe is blocked. This situation requires emergency treatment to prevent unconsciousness or death. Choking, heart disease, or other conditions may also cause the heart and breathing to stop. To save the life of the person, breathing and blood circulation must be restored immediately. Mouth-to-mouth resuscitation supplies oxygen to the blood in the lungs; cardiopulmonary resuscitation keeps oxygenated blood flowing to the brain and other vital organs.