In humans, breathing is a largely automatic function (although it can be controlled voluntarily for short periods of time), where the muscles of the chest and diaphragm expand in order to allow air to enter the lungs, and then contract to force air out of the lungs. During this process, about 20% of the oxygen in the inhaled air is taken into the bloodstream, and replaced with carbon dioxide. A human being at rest respirates (breaths in and out) about fifteen times a minute.
There are several reasons why a person may not be able to breathe. All of the conditions are life threatening:
- Choking - the airway is blocked by a foreign object. This can be treated by removing the object or performing a tracheotomy if the object cannot be dislodged.
- Anaphylactic shock - this conditions swells the airways and the throat making it more difficult for air to pass. Persons with this condition are given adrenaline, which will reverse the inflammation that caused the swelling.
- Pulmonary edema - this is when the air space surrounding the lungs fill with fluid, preventing the lungs from filling the space. Treatment is to suction the fluid from the space with a syringe.
- Paralysis - there are several conditions that affect the muscles surrounding the lung. Patients can be kept alive with a respirator.