Topic: Asphyxia and Asphyxial Deaths
Sub topics:
Introduction
Etiology of asphyxia
Pathophysiology of asphyxia
Violent asphyxia classification
Hanging
strangulation
Suffocation
Drowning
Notes: Asphyxia is defined as lack of oxygen in blood and tissues due to impaired or absence of exchange of oxygen and carbon dioxide on a ventilatory basis, leading to death. Serious deprivation of oxygen for 5 to 10 minutes can result in permanent damage to central nervous system and cardiovascular system resulting in death. In hanging, death is usually due to asphyxia or cerebral anoxia or vagal inhibition leading to cardiac arrest or injury to the spinal cord as observed in judicial hanging wherein death is due to fracture-dislocation of the C2C3C4 vertebrae. Hanging could be a postmortem hanging also, in order to conceal and mislead a case of homicide as suicidal hanging. Suicidal hanging is a common mode of committing suicide among men. Age is no bar for suicide by hanging. Homicidal hanging is very rare. Strangulation is a form of violent asphyxia caused by constricting the neck by some means, the force of constriction being other than weight of victim’s body. Drowning is a form of violent asphyxial death, wherein the entry of air into the lungs is prevented by water or other fluids due to the submersion of mouth and nostril.
Introduction: Asphyxia is defined as lack of oxygen in blood and tissues due to impaired or absence of exchange of oxygen and carbon dioxide on a ventilatory basis, leading to death.
ETIOLOGY OF ASPHYXIA: Asphyxia can develop because of several causes such as:
• Physical causes—breathing in high altitudes with rarefied/ vitiated medium, deficient of O2, e.g. mountaineering.
• Inhaling irrespirable gases, such as gases interfering with normal O2 carrying capacity of blood haemoglobin, e.g. CO, CO2, H2S, etc. or gases which prevent cellular oxidation enzymes, e.g. HCN.
• Drugs/poisons—directly depressing the respiratory centres, e.g. narcotics (morphine), anaesthetics, etc.
• Mechanical asphyxia—this is due to mechanical interference to respiration, e.g. hanging, strangulation, throttling, smothering, choking, drowning, etc
• Pathological asphyxia—this is due to diseases, e.g. lung pathology.
• Allergic reactions causing laryngeal oedema.
PATHOPHYSIOLOGY OF ASPHYXIA : Conventionally, the term asphyxia has been applied to all conditions in which oxygen supply to blood and tissue has been reduced appreciably below the normal working level by any interference with respiration. In death from asphyxia, usually it falls below the minimum necessary for continuance of life. Serious deprivation of oxygen for 5 to 10 minutes can result in permanent damage to central nervous system and cardiovascular system resulting in death. It is interesting to note that in a healthy adult body, normally blood that is circulating has about 1 litre of oxygen held in combination. Any interference with this results in asphyxia, which in turn triggers the consequences.
CLASSIFICATION OF MECHANICAL/ VIOLENT ASPHYXIA: Following are the causes;
1. Compression/ constriction of the neck, e.g. hanging, strangulation, throttling, etc.
2. Blocking external orifices of respiration, i.e. mouth and/or nostrils, e.g. smothering, overlying, suffocation, gagging, etc.
3. Impaction of foreign bodies in respiratory tract, e.g. choking
4. Compression and mechanical fixation of the chest and abdomen preventing the respiratory movements, e.g. traumatic asphyxia/crush asphyxia.
5. Inhalation of fluid into the respiratory tract, e.g. drowning
HANGING: Hanging is defined as complete or partial suspension of the body by a ligature tied around the neck and force of constriction on the neck being applied by the weight of the body hanged. In hanging, death is usually due to asphyxia or cerebral anoxia or vagal inhibition leading to cardiac arrest or injury to the spinal cord as observed in judicial hanging wherein death is due to fracture-dislocation of the C2C3C4 vertebrae. Hanging may be classified as complete, incomplete, typical or atypical. It has been scientifically accepted that pressure on the neck can result in occlusion of neck structures for respiratory functioning developing asphyxia.
Autopsy findings in hanging:
Face: Usually in most hangings, the face is pale. However it may be swollen and congested, with petechiae in partially suspended individuals, where the noose is tightened only by the weight of the head or the torso. Lips may show cyanotic tinge. Eyes may show prominent eyeballs or La-facie sympathique (wherein right eye remaining open with dilated pupil and the left eye closed with small pupil). Subconjuctival hemorrhages, protruded tongue bleeding from ear and nose can be seen. Salivary dribbling marks is a constant and important finding in case of death due to hanging. Salivation may not occur, when death is due to vagal inhibition.
Neck: Distended veins , ligature marks is seen.
Other body parts: Hands are usually clenched. Purple coloured postmortem hypostasis is usually in a peculiar distribution in the lower limbs and lower regions of upper limbs (hands/forearm). Involuntary voiding of urine and /fecal matter stains of which may be seen on the under garments or on the floor below. Penis may be found turgid and erect. Seminal emission may be noticed at the tip of the glans penis over the thighs or seminal stains may be seen on inner garments, etc. In female apart from the voiding of urine and stools, turgescence of vagina with blood-stained discharge may also be noticed.
MEDICOLEGAL ASPECTS OF HANGING
Hanging could be a postmortem hanging also, in order to conceal and mislead a case of homicide as suicidal hanging. Suicidal hanging is a common mode of committing suicide among men. Age is no bar for suicide by hanging. Homicidal hanging is very rare. It is virtually impossible to hang a healthy adult unless beaten to unconsciousness or rendered helpless by alcohol or drugs. Though the incidence of accidental hanging is not very common; it may be reported among infants, children, adolescent and adults.
STRANGULATION: Strangulation is a form of violent asphyxia caused by constricting the neck by some means, the force of constriction being other than weight of victim’s body. The application of pressure on the neck is either by bare hands, or by a ligature, or by any other material. In this, asphyxia is caused by constriction of the neck without suspending the body. Death may be due to vagus nerve stimulation leading to cardiac arrest, carotid artery blockage leading to unconsciousness, jugular vein blockage leading to congestion and haemorrhage.
Strangulation is usually homicidal, if suicidal struggle marks are often observed, as the victim usually makes all the effort to resent prior to getting strangulated. These could be abrasions, scratches or abraded contusions over face, arms and other parts of the body.
Manual Strangulation (Throttling): When bare hands are used to compress the neck and strangulate it is known as manual strangulation or throttling. The mechanism of death is by occlusion of the blood vessels supplying blood to the brain, i.e. the carotid arteries. Occlusion of the airway probably plays a minor role, Carotid sinus pressure, may result in vagus nerve stimulation resulting in cardiac arrest.
Virtually all strangulations whether ligature or manual are homicidal. There will be marks of violence, on other parts of the body. Though in ligature strangulation, females predominate as victims, it is not as much as reported in case of manual strangulation. The most common motive for manual strangulation was rape, followed by domestic violence. Thus if the victim is female, carefully look for evidence of sexual assault, as it is common for an assailant to molest/ rape a girl and then strangle her. Detailed examination of external and internal genital organs, including vaginal washings for chemical and microscopic examination, is performed preferably.
Suicidal manual strangulation is never reported. Manual self strangulation is impossible, as pressure on the neck depends on voluntary action, which is discontinued when the power of decision is obliterated with loss of consciousness.
SUFFOCATION : Suffocation is a form of asphyxia caused by lack of oxygen in the atmosphere or by mechanical obstruction to the air passages by mechanical means other than constriction of the neck and drowning. There are several forms of suffocation in general and they are entrapment, environmental suffocation ,smothering ,choking , traumatic asphyxia, suffocating gases.
SMOTHERING : Smothering is a form of asphyxia caused by mechanical occlusion of external air passages, viz. the nose and mouth by hand, cloth, plastic bag, duct tape or such other material. These deaths are usually either homicidal or suicidal, but very rarely accidental. Accidental smothering is common in alcoholics, intoxicated or unconscious person lying in prone position. After birth an infant may die from smothering if it is born with cul-de-sac. Children may get suffocated while playing with plastic bags over the face or head or on entire body.
DROWNING: Drowning is a form of violent asphyxial death, wherein the entry of air into the lungs is prevented by water or other fluids due to the submersion of mouth and nostril (complete submersion of whole body is not necessary). The mechanism of death in acute drowning is irreversible cerebral anoxia. Experiments and experiences suggested various causes of death among the drowning victims are: electrolyte imbalance (due to fresh/salt water drowning), cardiac arrhythmias, vagal inhibition, laryngeal spasm, head injury during fall in water, apoplexy, and exhaustion.
With the entry of more water into the body (inhaled and swallowed) there will be increase in body weight and specific gravity than that of water of the victim, consequence of which will be re-sinking of the victim, only to surface again due to all factors mentioned already. This will go on repeatedly till victim sinks finally to the bottom, and dies due to exhaustion, loss of consciousness, and the effects of onset of vicious cycle of asphyxia as a consequence of formation of fine froth, in the respiratory tract. Froth in the respiratory tract is due to churning-like mechanism of air, water and respiratory mucous secretions (surfactants), which prevent entry of air into the respiratory passages resulting in onset of asphyxia. It is claimed that the victim will die within 2 to 5 minutes of complete submersion as asphyxia supervenes within 2 minutes.
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