Asphyxia

Asphyxia
Specialty	Emergency medicine

Suffocation redirects here. For the band, see Suffocation (band).

Asphyxia (from Greek a-, "without" and sphuxis, "pulse, heartbeat") is a condition of severely deficient supply of oxygen to the body that arises from being unable to breathe normally. Asphyxia causes generalized hypoxia, which primarily affects the tissues and organs most sensitive to hypoxia first, such as the brain, hence resulting in cerebral hypoxia. Asphyxia is usually characterized by air hunger but this is not always the case; the urge to breathe is triggered by rising carbon dioxide levels in the blood rather than diminishing oxygen levels. Sometimes there is not enough carbon dioxide to cause air hunger, and victims become hypoxic without knowing it. In any case, the absence of effective remedial action will very rapidly lead to unconsciousness, brain damage and death. The constriction of the arteries and/or veins in the neck, such as in certain types of strangulations, do not cause asphyxia but rather cerebral ischemia (local asphyxia). Asphyxiation or suffocation refer to the process of asphyxia, where the body becomes increasingly hypoxic.

Causes of asphyxia

Certain accidents can cause asphyxiation in their victims. Asphyxia may also be deliberately induced via various asphyxiation techniques, in which the aim is to cause asphyxia by partially or fully interfering with normal breathing. Asphyxiation techniques are used to maim or kill in capital punishment, suicide, torture, and warfare. They are also used non-fatally in martial arts, combat sports, BDSM and during sex as erotic asphyxia. Because the need to breathe is triggered by the level of carbon dioxide in the blood, some victims may not experience an urgent need to breathe and may remain unaware of the onset of hypoxia.

Insufficient environmental oxygen

Asphyxia is the eventual result of prolonged exposure to an atmosphere containing too little oxygen to sustain life; many such situations involve the displacement of oxygen-containing air with an asphyxiant gas. Examples of environmentally-induced asphxia include:

• The filling of cryogenic vessels with liquified, oxygen-free gases such as nitrogen in an enclosed space.
• Workers entering a brewery fermentation vat unaware that the space is filled with carbon dioxide.
• Workers descending into a sewer or the hold of a ship containing heavier than air, oxygen-free gases usually methane or carbon dioxide.
• The misuse or failure of closed-circuit diving rebreather sets where the recirculated breathing gas contains insufficient oxygen.
• Breathing a hypoxic breathing gas mixture while diving in shallow water where the partial pressure of oxygen is too low to support consciousness; hypoxic bottom gasses are designed only to be breathed at depth where larger amounts of oxygen become toxic under pressure.
• Inhalation of overwhelming amounts of non-oxygen gases such as helium or CO₂ fire extinguishers for recreational or amusement purposes.
• Loss of aircraft cabin pressure; cabin pressure of commercial aircraft is usually kept at an altitude equivalent of between 5,000-8,000 ft, unconsciousness can occur without awareness if a malfunction allows the cabin altitude equivalent to rise above 20,000 ft.
• Exposure to a vacuum, such as the decompression of a spacecraft or space suit (see Soyuz 11).

Physical obstruction of air flow

• Crushing or constriction of the chest or abdomen (compressive asphyxia)
• Smothering, where the external respiratory orifices are covered.
• Drowning caused by violence or accidents.
• Choking due to food in the airway.
• Strangling where the airway is constricted, especially in certain types of chokeholds called air chokes.
• Hanging or ligature strangulation may lead to asphyxia.
• Reduction of the airways due to anaphylaxis or asthma.
• Inhalation of vomit.
• Positional asphyxia.
• The practice of erotic asphyxiation, also called breath control play.
• Situations where a newborn infant experiences inadequate respiration during childbirth can lead to asphyxia neonatorum.

Chemical or physiological interference with respiration

Various chemical and physiological situations can interfere with the body's ability to absorb and use oxygen or regulate blood oxygen levels:

• Carbon monoxide inhalation, such as from a car exhaust, carbon monoxide has a higher affinity than oxygen to the hemoglobin in the blood's red blood corpuscles bonding with it tenaciously, displacing oxygen and preventing the blood from transporting it around the body.
• Contact with certain chemicals, including pulmonary agents (such as phosgene) and blood agents (such as hydrogen cyanide).
• Self-induced hypocapnia by hyperventilation, as in shallow water or deep water blackout and the choking game.
• A seizure which stops breathing activity.
• Sleep apnea.
• Drug overdose.
• Ondine's curse, central alveolar hypoventilation syndrome, or primary alveolar hypoventilation, a disorder of the autonomic nervous system in which a patient must consciously breathe. Although it is often said that persons with this disease will die if they fall asleep, this is not usually the case.
• Acute respiratory distress syndrome

Smothering

Smothering refers to the mechanical obstruction of the flow of air from the environment into the mouth and/or nostrils, for instance by covering the mouth and nose with a hand or a plastic bag. Smothering can be either partial or complete, where partial indicates that the person being smothered is able to inhale some air, although less than required. Normally, smothering requires at least partial obstruction of both the nasal cavities and the mouth to lead to asphyxia. Smothering with the hands or chest is used in some combat sports to distract the opponent, and create openings for transitions, as the opponent is forced to react to the smothering. It is also used in BDSM as a type of facesitting. Or you can smother somebody with a pillow.

In some cases, smothering is combined with simultaneous compressive asphyxia. One example is overlay, in which an adult accidentally rolls over an infant during co-sleeping; an accident that often goes unnoticed and is mistakenly thought to be sudden infant death syndrome. Other accidents involving a similar mechanism are cave-ins or when an individual is buried in sand or grain. In homicidal cases, the term burking is often ascribed to a killing method that involves simultaneous smothering and compression of the torso.

Compressive asphyxia

The knee-on-belly position compresses the chest, making it difficult for the person on the bottom to breathe.

Compressive asphyxia (also called chest compression) refers to the mechanical limitation of the expansion of the lungs by compressing the torso, hence interfering with breathing. Compressive asphyxia occurs when the chest or abdomen is compressed posteriorly. In accidents, the term traumatic asphyxia or crush asphyxia is usually used to describe compressive asphyxia resulting form being crushed or pinned under a large weight or force. An example of traumatic asphyxia include cases where an individual has been using a car-jack to repair a car from below only to be crushed under the weight of the vehicle when the car-jack slips. In fatal crowd disasters, such as the Heysel Stadium disaster, traumatic asphyxia is called riot-crush. Contrary to popular belief, it is not the blunt trauma from trampling that causes the large part of the deaths in such cases, but rather the compressive asphyxia from being crushed against the crowd. In confined spaces, people push and lean against each other; evidence from bent steel railings in several fatal crowd accidents have shown horizontal forces over 4500 N (comparative weight approximately 460kg). In cases where people have stacked up on each other forming a human pile, estimations have been made of around 380kg of compressive weight in the lowest layer.

Chest compression is also featured in various grappling combat sports, where it is sometimes called wringing. Such techniques are either used to tire the opponent, or as complementary or distractive moves in combination with pinning holds, or sometimes even as a submission holds. Examples of chest compression include the knee-on-stomach position, or techniques such as leg scissors (also referred to as body scissors and in budo referred to as do-jime, 胴絞, "trunk strangle") where you wrap the legs around the opponent's midsection and squeeze them together.

External links

• Cross-side to chest compression choke