Oxygen shortage, possibly causing death. Suffocation usually occurs because breathing is obstructed, as in choking. Examples of other causes are drowning, in which water in the lungs prevents breathing, a plastic bag over the head which closes the mouth and nose because it is sucked in, and vomiting in unconscious people without the stimulus to cough. A less obvious cause is carbon monoxide inhalation, which drives the oxygen out of the red blood cells and thus prevents the tissues from being supplied with oxygen. The first symptoms are shortness of breath and fear, followed by unconsciousness; the patient is pale or blue in colour, red in carbon monoxide poisoning. Breathing stops after a while and, finally, death occurs. The brain cannot continue functioning for more than a few minutes without oxygen, and after this it becomes damaged. Help must therefore be given quickly. If suffocation seems likely the first step is to free the respiratory tract by removing objects and by wiping vomit from the mouth. If the patient is not breathing, mouth-to-mouth resuscitation must be applied until breathing starts again or help arrives. Another clinical picture is suffocation or asphyxia in a new-born baby. This occurs because the baby, which is supplied with oxygen via the umbilical cord before being born, receives insufficient oxygen before or during birth. It is then pale or blue in colour when it is born, frequently limp, and does not start breathing spontaneously. The baby’s own breathing is its only oxygen supply after it has been born, and breathing must therefore commence immediately. The child must then be given artificial respiration in addition to other steps which must be taken to improve its condition. All this must be done quickly in order to prevent brain damage.