ABC of first aid is a mnemonic acronym referring to the treatment of life-threatening damage. Is based on the demand for oxygen, without which life is impossible. "A" stands for "airway" - the respiratory system. Other activities have to wait, if you can not breathe due to airway blockage. Inhalation is the nose and mouth, throat and trachea, and lungs. If these places are blocked, choking victim, not getting the oxygen needed for life. Not survive more than a few minutes. Therefore need to check for in the airway are not any obstacles, such as pieces of food or vomit. Children can choke on small locked in the mouth toys, and adults with artificial teeth. For blocked airways indicates wheezing or nozzles, or foam on the outside paragraph or nose. In some cases, must necessarily put the victim on the back and tilt the head back to straighten the most inhalation, and remove the obstacle with his fingers.