Asphyxia is a condition of severely deficient supply of oxygen to the body. In the absence of remedial action it will very rapidly lead to unconsciousness and death Asphyxia is the same as suffocation. Anoxia means the pathological state in which tissues do not get (enough of) oxygen..
Causes of asphyxia can include:
Physical obstruction of the passage of air to or from the lungs:
Crushing or constriction of the chest or abdomen
Choking
Drowning
Strangulation, or external constriction of the neck or throat, e.g. by a rope (as in hanging), hands, or a constrictor snake
Reduction of the airways due to anaphylaxis or asthma
Inhalation of vomit
Positional asphyxia
The extremely dangerous and frequently lethal practice of erotic asphyxiation also called "breath control play"
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There are three forms of strangulation---hanging, ligature and manual. Almost all attempted or actual homicides by strangulation involve either ligature or manual strangulation, according to a manual regarding the investigation and prosecution of strangulation cases written by Gael B. Strack, San Diego assistant city attorney; and Dr. George McClane, emergency physician. The manual was edited by David C. James, deputy city attorney for San Diego and was updated in May, 1999.
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Almost all attempted or actual homicides by strangulation involve either ligature or manual strangulation, according to the manual. Ten percent of violent deaths in the U.S. each year are due to strangulation, six females to every male. Ligature strangulation is strangulation with a cord-like object, also referred to as garroting, and many include anything from a telephone cord to articles of clothing. Manual strangulation, throttling, is usually done with the hands, but notable variants include using the forearms, as when police officers used carotid restraint, to standing or kneeling on the victim's throat.
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A rudimentary knowledge of neck anatomy is critical in order to understand adequately the clinical features of a strangled victim. The hyoid bone is a a small horseshoe-shaped bone in the neck which helps to support the tongue. The larynx, made up of cartilage, not bone, consist of two parts: the thyroid cartilage (so-called because it is next to the thyroid gland) and the tracheal rings. Carotid arteries are the major vessels that transport oxygenated blood from the heart and lungs to the brain. These are the arteries at the side of the neck that persons administering CPR (cardiopulmonary resuscitation) check for pulses. Jugular veins are the major vessels that transport deoxygenated blood from the brain back to the heart.
The general clinical sequence of a victim who is being strangled is one of severe pain, followed by unconsciousness, followed by brain death. The victim will lose consciousness by any one or all of the following: blocking of the carotid arteries (depriving the brain of oxygen), blocking of the jugular veins (preventing deoxygenated blood from exiting the brain) and closing off the airway, causing the victim to be unable to breath. Only 11 pounds of pressure placed on both carotid arteries for 10 seconds is necessary to cause unconsciousness. However, if pressure is released immediately, consciousness will be regained within 10 seconds. After 50 seconds of continuous oxygen deprivation, the victim rarely recovers.
To completely close off the trachea, three times as much pressure (33 lbs) is required. Brain death will occur in 4 to 5 minutes, if strangulation persists.
Breathing changes may be due to the hyperventilating that normally goes hand in hand with a terrifying event, but more significantly may be secondary to an underlying neck injury. The victim may find it difficult to breathe (dyspnea) or may be unable to breathe (apnea). It is critical to appreciate that although breathing changes may initially appear to be mild, underlying injuries may kill the victim up to 36 or more hours later due to decompensation of the injured structures.
The tiny red spots (petechiae) characteristic of many cases of strangulation are due to ruptured capillaries---the smallest blood vessels I the body---and sometimes may be found only under the eyelids. However, sometimes they may be found around the eyes in the periobital region, anywhere on the face and on the neck in and above the area of constriction.
