Holding one's breath

Apnea
A 32 s breathing pause in a sleep apnea patient
Classification and external resources
Specialty	Pulmonology, pediatrics
ICD-9-CM	786.03
MeSH	D001049
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Apnea or apnoea is suspension of breathing. During apnea, there is no movement of the muscles of inhalation, and the volume of the lungs initially remains unchanged. Depending on how blocked the airways are (), there may or may not be a flow of gas between the lungs and the environment; gas exchange within the lungs and cellular respiration is not affected. Voluntarily doing this is called holding one's breath.

Apnea can be voluntarily achieved, drug-induced (such as opiate toxicity or tryptamine toxicity), mechanically induced (for example, by strangulation or choking), or it can occur as a consequence of neurological disease or trauma. During sleep in patients who are suffering from sleep apnea, these events can occur up to 20–30 times per hour, every night.

Apnea can also be observed during periods of heightened emotion, such as during crying or accompanied by the Valsalva maneuver when a person laughs.

Voluntary apnea can be achieved by closing the vocal cords, simultaneously keeping the mouth closed and blocking the nasal vestibule, or constantly activating expiratory muscles.

Under normal conditions, humans cannot store much oxygen in the body. Prolonged apnea leads to severe lack of oxygen in the blood circulation. Permanent brain damage can occur after as little as three minutes and death will inevitably ensue after a few more minutes unless ventilation is restored. However, under special circumstances such as hypothermia, hyperbaric oxygenation, apneic oxygenation (see below), or extracorporeal membrane oxygenation, much longer periods of apnea may be tolerated without severe consequences.

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