In order to stay alive, all persons need to have an open airway – a clear passage where air can move in through the mouth or nose through the pharynx and down in to the lungs, without obstruction. Conscious people will maintain their own airway automatically, but those who are unconscious may be unable to maintain a patent airway, as the part of the brain which automatically controls breathing in normal situations may not be functioning.
If the patient was breathing, a first aider would normally then place them in the recovery position, with the patient leant over on their side, which also has the effect of clearing the tongue from the pharynx. It also avoids a common cause of death in unconscious patients, which is choking on regurgitated stomach contents.
The airway can also become blocked through a foreign object becoming lodged in the pharynx or larynx, commonly called choking. The first aider will be taught to deal with through a combination of back slaps and abdominal thrusts.
Once the airway has been opened, the first aider would assess to see if the patient is breathing. If there is no breathing, or the patient is not breathing normally, such as agonal breathing, the first aider will undertake what is probably the most recognised first aid procedure – cardiopulmonary resuscitation or CPR which involves breathing for the patient, and manually massaging the heart to promote blood flow around the body.