Asphyxial Deaths
1. What this chapter covers, and how NEET PG actually tests it
Asphyxia questions are almost always given as an autopsy description and a request to name the mechanism or the manner of death.
The organising principle is to ask what was obstructed, and by what force.
Oxygen delivery can fail at four points, and each produces a recognisable pattern.
| Point of failure | Mechanism | Examples |
|---|---|---|
| The air itself | Insufficient oxygen in the atmosphere | Confined space, irrespirable gas |
| The airway | Mechanical blockage | Smothering, gagging, choking |
| The neck | External pressure on vessels or airway | Hanging, strangulation |
| The chest | Prevention of respiratory movement | Traumatic asphyxia, overlaying |
The second question, and the one that decides the medicolegal answer, is what supplied the force. In hanging the force is the body's own weight; in strangulation it is applied by another person. Almost everything that distinguishes the two on the autopsy table follows from that difference.
2. Fundamentals
2.1 The classical signs and why they mislead
The traditional signs of asphyxia are cyanosis, congestion, petechial haemorrhages, fluidity of the blood and right ventricular dilatation.
Petechial haemorrhages in serous membranes are called Tardieu spots, classically described on the pleura and pericardium.
Every one of these signs is non-specific. Congestion and fluidity occur in many deaths, and petechiae appear whenever venous pressure rises abruptly.
The safe examination position is that these signs raise the possibility of asphyxia but never establish it. The diagnosis rests on the local findings at the point of obstruction and on the circumstances.
2.2 How much pressure is needed
The neck structures occlude at very different pressures, and the order explains why death can occur without airway obstruction at all.
| Structure | Approximate force to occlude |
|---|---|
| Jugular veins | 2 kg |
| Carotid arteries | 5 kg |
| Trachea | 15 kg |
| Vertebral arteries | 30 kg |
The jugular veins close first, which is why partial suspension and incomplete constriction produce intense facial congestion and petechiae: blood enters through patent arteries but cannot leave.
Complete suspension occludes arteries as well, so the face may instead be pale. This apparent contradiction resolves entirely by asking whether arterial inflow was also stopped.
2.3 The sequence and how long it takes
Classical descriptions divide mechanical asphyxia into three stages: dyspnoea, convulsions, then apnoea and death.
The stages are useful only as a rough frame, because the timing depends entirely on the mechanism.
Neck compression that occludes the carotids causes unconsciousness within seconds, since cerebral blood flow stops immediately, whereas pure airway obstruction takes minutes because the blood remains oxygenated for a while.
That difference has a direct medicolegal consequence. A victim of manual strangulation loses consciousness fast but must be held for several minutes to die, which is why sustained deliberate pressure is required and why the finding is regarded as homicidal.
It also explains why defence injuries and fingernail marks made by the victim on their own neck are often present, and why their absence in a supposedly conscious victim needs explaining.
3. Hanging
3.1 Types and mechanism
Hanging is constriction of the neck by a ligature tightened by the weight of the body itself.
Complete hanging means the body is entirely suspended; incomplete or partial hanging means some part touches the ground, and this is common and entirely compatible with suicide.
Typical hanging has the knot at the nape of the neck; atypical hanging has it anywhere else.
Death is usually cerebral ischaemia from vascular occlusion rather than airway obstruction, which is why hanging can be rapid and why very little weight is required.
Judicial hanging is different. A calculated long drop produces fracture-dislocation of the upper cervical spine, classically the hangman's fracture through the pedicles of the axis, with immediate cord transection.
3.2 The ligature mark
The mark is the single most examined feature in the subject.
In hanging the mark is oblique, non-continuous and situated high on the neck, above the thyroid cartilage.
It runs upward towards the knot and there is a gap at the knot site, because the ligature lifts away from the skin there.
The mark is typically dry, hard and parchment-like, because the ligature abrades the epidermis and the exposed dermis dries after death.
The base of the mark shows no vital reaction if the hanging was postmortem suspension, which is the discrimination the exam expects.
3.3 Associated findings
Postmortem lividity in a suspended body settles in the hands, forearms, feet and legs, producing a glove-and-stocking distribution.
Dribbling of saliva from the angle of the mouth is a vital sign, since it requires an active swallowing reflex and gravity acting on a living body.
Simon's sign is haemorrhage in the anterior aspect of the lumbar intervertebral discs, attributed to stretching of the spine.
Hyoid fracture is uncommon in hanging in the young, because the greater horns do not fuse until around the fifth decade and a mobile hyoid resists fracture.
4. Strangulation
4.1 Ligature strangulation
Here the constricting force is applied by a hand or another agency, not by the body weight.
The mark is transverse, continuous and low on the neck, at or below the level of the thyroid cartilage.
Because the force is applied by another person and is usually sustained, congestion, cyanosis and petechiae are typically far more marked than in hanging.
Ligature strangulation is almost always homicidal. Suicide by this route is exceptional and requires a self-tightening arrangement.
4.2 Manual strangulation
Throttling is constriction by the hands, and its findings are quite different because the force is discontinuous and focal.
There is no ligature mark. Instead there are discoid bruises from fingertips and crescentic abrasions from fingernails.
Internal injury is much greater than in ligature strangulation, with bruising of neck muscles and frequent fracture of the hyoid greater cornu or the superior horns of the thyroid cartilage.
Manual strangulation is homicidal by definition, because loss of consciousness releases the grip before death can occur.
4.3 The comparison that decides most questions
| Feature | Hanging | Ligature strangulation |
|---|---|---|
| Force | Body weight | Applied externally |
| Mark direction | Oblique | Transverse |
| Mark continuity | Interrupted at knot | Continuous |
| Mark level | Above thyroid cartilage | At or below it |
| Face | Pale if complete, congested if partial | Congested, marked petechiae |
| Hyoid fracture | Uncommon in the young | More common |
| Usual manner | Suicidal | Homicidal |
4.4 Named variants
Mugging is constriction of the neck by the forearm applied from behind, leaving few external marks but considerable internal injury.
Garrotting is ligature strangulation applied suddenly from behind, historically as an execution method.
Bansdola is an Indian term for neck compression between two bamboo sticks placed on either side, producing two parallel bruise lines.
5. Drowning
5.1 Types and mechanism
Wet drowning is the common form, with aspiration of fluid into the lungs.
Dry drowning accounts for roughly ten to fifteen per cent of cases, in which laryngospasm prevents fluid entry and death is from asphyxia without significant aspiration.
Immersion syndrome, also called hydrocution, is sudden cardiac arrest on entering cold water, mediated by vagal stimulation.
Secondary drowning is delayed death from pulmonary oedema and chemical pneumonitis hours to days after rescue.
5.2 Freshwater and seawater
The classical distinction rests on tonicity relative to plasma.
Freshwater is hypotonic, so aspirated water is absorbed rapidly into the circulation, producing haemodilution, haemolysis, hyperkalaemia and ventricular fibrillation.
Seawater is hypertonic, so fluid is drawn from the circulation into the alveoli, producing pulmonary oedema and haemoconcentration.
This distinction is examined frequently but overstated clinically, since in practice the volume aspirated is usually too small to produce the classical electrolyte pictures, and hypoxia dominates in both.
5.3 Autopsy findings
Fine white leathery froth at the mouth and nostrils, which reforms after being wiped away, is the most reliable external sign.
The froth is generated by mixing of water, air and respiratory mucus, and its formation therefore requires active respiration, making it a vital sign.
Emphysema aquosum describes voluminous waterlogged lungs that retain rib impressions and overlap the mediastinum.
Paltauf haemorrhages are pale bluish subpleural haemorrhages attributed to rupture of alveolar septa.
Water and weed found in the stomach and, more tellingly, beyond the pylorus in the duodenum, indicate active swallowing and therefore support drowning rather than passive entry.
Grass, weed or gravel clenched in the hands is a cadaveric spasm, and because spasm requires a living moment of intense effort it is accepted as strong evidence of drowning at that spot.
Cutis anserina, or goose skin, and washerwoman's hands are signs of immersion, not of drowning, and occur equally in a body placed in water after death.
5.4 The diatom test
Diatoms are algae with silica shells that resist decomposition and putrefaction.
The test depends on circulation, because only a beating heart can carry aspirated diatoms from the lungs into the systemic circulation and into distant organs.
Demonstrating diatoms in the femoral bone marrow, where contamination is least likely, supports antemortem drowning. Finding them only in the lungs proves nothing more than immersion.
The Gettler test compared chloride concentrations in blood from the two sides of the heart, and is now regarded as unreliable and of historical interest.
6. The suffocation group
6.1 Smothering and gagging
Smothering is closure of the external air passages by hand, cloth or plastic, and is frequently homicidal in infants and the incapacitated.
External signs may be minimal, particularly when a soft object is used, so absence of injury does not exclude it.
Gagging is obstruction by material forced into the mouth, often occurring during a robbery where death was not intended.
6.2 Choking
Choking is internal obstruction of the airway by a foreign body.
Café coronary describes sudden collapse during a meal when a bolus of food impacts in the larynx, typically in an intoxicated person, and it is important because it closely mimics a myocardial infarction and is a natural, non-suspicious death.
6.3 Traumatic asphyxia and overlaying
Traumatic asphyxia follows fixation of the chest wall, in crowd crushes, vehicle entrapment or collapse of a structure.
Masque ecchymotique is the resulting deep congestion and petechial haemorrhage of the face, neck and upper chest, with a sharp cut-off at the level of the compression.
Overlaying is accidental smothering of an infant by a sleeping adult, and the differential includes sudden infant death syndrome and deliberate smothering.
Burking, named after the Edinburgh case of Burke and Hare, combines smothering with kneeling on the chest, so it is smothering and traumatic asphyxia together.
6.4 Autoerotic asphyxia
Deliberate partial neck constriction is used to heighten sexual arousal, and death results from miscalculation.
The scene is characteristic, with a protective padding under the ligature, an escape mechanism, mirrors, and often erotic material or partial cross-dressing.
It is classed as accidental, and recognising it matters because the family and the initial investigation almost always suspect suicide or homicide.
7. Deaths from irrespirable atmospheres
This is the first row of the opening table, where the failure is in the air itself rather than in the body.
7.1 Carbon monoxide
Carbon monoxide binds haemoglobin with an affinity more than two hundred times that of oxygen, and it also shifts the dissociation curve leftward.
The shift matters as much as the binding, because it means the oxygen still carried is released less readily to tissues, so hypoxia is worse than the carboxyhaemoglobin figure alone suggests.
Postmortem lividity is cherry-pink, and the same colour appears in the blood and viscera.
A conventional pulse oximeter cannot distinguish carboxyhaemoglobin from oxyhaemoglobin and reads falsely normal, so the diagnosis needs co-oximetry or blood gas measurement.
Treatment is one hundred per cent oxygen, which shortens the elimination half-life substantially, with hyperbaric oxygen considered for severe poisoning or pregnancy.
Common Indian settings are charcoal braziers used for indoor heating, faulty geysers in unventilated bathrooms and generators run in closed rooms.
7.2 Other gases and confined spaces
Hydrogen sulphide is the sewer and septic tank gas, and it inhibits cytochrome oxidase much as cyanide does.
It produces a rotten-egg smell at low concentrations but rapidly paralyses the olfactory nerve, so loss of the smell is a danger sign rather than a reassurance. Lividity may be greenish and the viscera discoloured.
Carbon dioxide accumulates in disused wells, silos and fermentation vats, displacing oxygen, and it is a classic cause of multiple deaths when rescuers enter after the first victim.
Cyanide and hydrogen sulphide are histotoxic rather than asphyxiant in the mechanical sense, since oxygen reaches the cell but cannot be used, which is why venous blood stays bright red.
8. Antemortem or postmortem, and how the neck is examined
The central medicolegal question is whether the findings were produced before or after death.
Vital reaction is the general answer: bleeding into tissue, inflammatory cellular response and enzyme changes at the wound margin all require a circulation.
In hanging, the ligature mark of a living victim shows congestion, ecchymosis and vital reaction at its base, while a mark made after death is soft, pale and free of underlying haemorrhage.
The neck must be dissected in a bloodless field, and the technique exists to prevent artefact.
The brain is removed and the thoracic and abdominal organs taken out first, so the neck vessels drain and passive congestion does not mimic bruising.
The neck is then opened in layers, each muscle examined separately, and the hyoid and laryngeal cartilages inspected last.
Postmortem artefacts are common enough to warrant explicit caution: hypostasis in a suspended body can resemble bruising, and rough handling can fracture a decomposed hyoid.
8.1 The body in water
A body normally sinks, then refloats as putrefactive gases accumulate, which takes roughly three to five days in Indian summer conditions and considerably longer in cold water.
Prolonged immersion favours adipocere formation, in which body fat is hydrolysed and hydrogenated into a firm greasy material that preserves facial features and can help identification months later.
9. Worked examples
Example 1. A body is found suspended. The neck mark is transverse, continuous and lies below the thyroid cartilage, and the face is deeply congested. What does this suggest?
Suspension does not establish hanging. The mark's direction, continuity and level are all those of ligature strangulation, so this raises strong suspicion of homicidal strangulation with postmortem suspension staged to resemble suicide.
Example 2. A middle-aged man collapses at a wedding meal after drinking. Autopsy shows a meat bolus at the laryngeal inlet. What is the diagnosis and manner?
This is café coronary. The collapse mimics cardiac death, but the mechanism is choking. The manner is accidental and the death is not suspicious, which is the point of knowing the entity.
Example 3. Diatoms are found in the lung tissue of a body recovered from a river, but not in the femoral marrow. What can be concluded?
Diatoms reach distant organs only if the circulation was still functioning. Their presence in lung alone is consistent with passive entry of water after death, so this supports immersion of a body rather than antemortem drowning.
Summary
Ask what was obstructed and by what force; the level of failure and the source of the force generate almost every finding and every medicolegal conclusion.
The classical signs of asphyxia are all non-specific, so the diagnosis rests on local findings at the point of obstruction plus the circumstances.
Jugular veins occlude at about 2 kg and carotids at about 5 kg, which is why hanging kills by cerebral ischaemia and needs very little weight.
Incomplete constriction congests the face because venous outflow stops while arterial inflow continues; complete suspension may leave the face pale.
The hanging mark is oblique, interrupted at the knot and above the thyroid cartilage; the strangulation mark is transverse, continuous and at or below it.
Hyoid fracture is uncommon in young hanging victims because the greater horns fuse only around the fifth decade.
Manual strangulation leaves discoid bruises and nail abrasions rather than a mark, causes more internal injury, and is homicidal by definition.
In drowning, fine leathery froth is a vital sign because it requires active respiration, while goose skin and washerwoman's hands only prove immersion.
The diatom test depends on circulation, so diatoms in femoral marrow support antemortem drowning while diatoms confined to lung do not.
Café coronary is accidental choking that mimics infarction, and autoerotic asphyxia is accidental death that mimics suicide; both exist as entities to prevent a wrong manner of death being recorded.
Carbon monoxide gives cherry-pink lividity and a falsely normal pulse oximeter reading, and it shifts the dissociation curve leftward as well as occupying binding sites.
Cyanide and hydrogen sulphide leave venous blood bright red because oxygen arrives at the cell but cannot be used.
Vital reaction distinguishes antemortem from postmortem injury, and the neck must be dissected in a bloodless field after removing the brain and body cavity organs so that hypostasis is not mistaken for bruising.
