This simple technique could save a life First Aid is one of the few things that people go to the trouble of learning expecting and hoping NOT to use it. If a casualty is not breathing and showing no signs of life it is vital to at least push on the chest to 1/3 of depth while waiting for the ambulance. D R S A B C D Danger, Response Send for Help if Needed Airway, Breathing, Compressions, Defibrillation First Aid. Read More ...