What is Hypocapnia?

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  • Written By: C.B. Fox
  • Edited By: Susan Barwick
  • Last Modified Date: 21 December 2018
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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.


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Post 3

I did it as a teen and only used my hands. Hyperventilating then palms on my carotid. I had bruises on my elbows when I would accidentally fall forward instead of backward onto the bed. Look for them on your kids.

Post 2

@aviva - I think it's wonderful that you and your daughter have such an open relationship. It's important to be open and honest with our children in order to gain their trust with such sensitive subjects.

I work in the emergency room of a very large hospital and I can't tell you how many cases of self-induced hypocapnia I've seen among children, some as young as six years old.

The Center for Disease Control recommends that health care providers as well as parents and teachers become familiar with signs of the games evidence.

Physical signs on the body are markings on the neck and bloodshot eyes. The child may have severe headaches and a sense of disorientation after being alone for awhile.

Listen for any discussions about the game and watch for any unusual conditions in their room like ropes, belts or scarves tied to furniture or doorknobs or knotted up on the floor.

Post 1

I was completely shocked when my daughter first told me about the fainting game. She's sixteen and we're very close, at least I like to think so. Apparently she was at a party with some friends when a group of kids were taking turns strangulating each other for a temporary rush.

I couldn't believe they would even attempt such a dangerous activity. It makes me wonder if so many of the teen suicides weren't actually an accident from a game that had gone too far.

For the safety of our children, are there any signs for us parents and educators to be on the lookout for?

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