Hypocapnia, also called hypocarbia, is the condition of having a decreased level of carbon dioxide in the blood. Though generally thought of as a waste product, carbon dioxide is an important part of body chemistry and is necessary for balancing pH and regulating breathing. A number of things can cause hypocapnia, including certain medications and an irregular breathing pattern.
The most common cause is breathing either too quickly or too deeply. This increased rate of respiration, called hyperventilation, can be a temporary condition caused by anxiety or stress, or it can be indicative of a chronic problem. Occasionally, hyperventilation might be purposefully induced in order to create a sensation of being high. With increased respiration, the level of oxygen in the blood stream rises and the level of carbon dioxide decreases.
Hyperventilation, and the state of hypocapnia it leads to, can create problems with brain function. It can cause the blood vessels in the brain to constrict, which can lead to decreased levels of oxygen in the brain. This can create feelings of dizziness, anxiety and difficulty seeing straight. In most cases, the patient is able to recover quickly and easily because the effects quickly reverse when breathing returns to normal.
Occasionally, when breathing does not return to normal, hypocapnia can lead to more serious problems. It can affect the brain stem, which is responsible for monitoring and regulating breathing. If the brain stem senses a severe drop in carbon dioxide and a subsequent rise in oxygen levels, it can suppress a person’s breathing to the point where he loses consciousness. Blacking out can lead to injury because the person affected is likely to fall down and will be unable to catch himself. Breathing generally returns to normal while the affected person is unconscious.
A state of hypocapnia can be induced for a number of reasons, although doing so can be deadly. Free divers will occasionally hyperventilate before diving because this allows them to stay underwater for longer periods of time. This has led to many drownings, as the condition can cause a blackout while a diver is underwater. Preadolescents and adolescents, especially girls, sometimes use self-induced hypocapnia in order to experience the state of dizziness that occurs along with the cerebral hypoxia. Injury due to black out and brain damage are risks of this activity, which is considered extremely dangerous to the health of the participating youths.