Postural asphyxia, also known as positional asphyxia, is a form of asphyxia which occurs when someone's position prevents them from breathing adequately. A small but significant number of people die suddenly and without apparent reason during restraint by police, prison (corrections) officers and health care staff. Positional asphyxia may be a factor in many of these deaths.
- Postural asphyxia is a potential danger of many physical restraint techniques, and of some bondage techniques.
- People may die from positional asphyxia by simply getting themselves into a breathing-restricted position they cannot get out of, either through carelessness or as a consequence of another accident.
It has been hypothesized that historical crucifixion killed its victims by slow positional asphyxia as they became exhausted.
Research has suggested that restraining a person in a face down position is likely to cause greater restriction of breathing than restraining a person face up. Many law enforcement and health personnel are now taught to avoid restraining people face down or to do so only for a very short period of time. Risk factors which may increase the chance of death include obesity, prior cardiac or respiratory problems, and the use of illicit drugs such as cocaine.
Some researchers report that the effects of restraint on oxygen levels is limited, and that other factors must be present to explain sudden deaths during restraint.