Erotic asphyxiation or breath control play is the intentional restriction of oxygen to the brain for the purposes of sexual arousal.
This sexual practice is variously called asphyxiophilia, autoerotic asphyxia, hypoxyphilia. The term autoerotic asphyxiation is used when the act is done by a person to themselves. Colloquially, a person engaging in the activity is sometimes called a gasper.
The erotic interest in asphyxiation is classified as a paraphilia in the Diagnostic and Statistical Manual of the American Psychiatric Association.
Author John Curra wrote, "The carotid arteries (on either side of the neck) carry oxygen-rich blood from the heart to the brain. When these are compressed, as in strangulation or hanging, the sudden loss of oxygen to the brain and the accumulation of carbon dioxide can increase feelings of giddiness, lightheadedness, and pleasure, all of which will heighten masturbatory sensations."
Author George Shuman describes the effect as such, "When the brain is deprived of oxygen, it induces a lucid, semi-hallucinogenic state called hypoxia. Combined with orgasm, the rush is said to be no less powerful than cocaine, and highly addictive."
Concerning hallucinogenic states brought about by chronic hypoxia, Dr. E L Lloyd notes that they may be similar to the hallucinations experienced by climbers at altitude. He further notes that no such state occurs in hypoxia brought about by sudden aircraft decompression at altitude. These findings suggest to him that they do not arrive purely from a lack of oxygen. Upon examining the studies on hypoxia he found that "abnormalities in the cerebral neurochemistry involving one or more of the interconnected neurotransmitters, dopamine, 5-hydroxytryptamine, and β-endorphin had been reported in all the conditions associated with hallucinations."