Overview
Asphyxia is a lack of oxygen or an excess of carbon dioxide in the body usually caused by interruption of breathing or insufficient oxygen supply. It stems from the greek word ‘Asphyxua’ which means ‘a lack of pulsation’. In its broadest sense, asphyxia refers to a state where the body becomes deprived of oxygen while in excess of carbon dioxide (hypoxia and hypercapnoea).
Classification of asphyxia
| Classification | Description |
|---|---|
| Mechanical (Violent) asphyxia | Mechanical interference of the passage of air to the respiratory tract e.g. smothering, hanging, strangulation, throttling, gagging, drowning etc. |
| Pathological asphyxia | A disease of the upper respiratory tract prevents entry of oxygen into the lungs e.g. laryngeal edema, spams, tumors |
| Toxic (Chemical) asphyxia | Respiratory centres are depressed by a chemical or drug e.g. opioid overdose |
| Environmental asphyxia | Caused by breathing in vitiated atmosphere e.g. carbon monoxide poisoning |
| Traumatic asphyxia | Blunt trauma to the thorax interferes with respiration by causing pneumothorax, hemothorax, or pulmonary emphysema |
| Positional asphyxia | Asphyxia is caused by peculiar body position which prevents adequate gas exchange e.g. forced flexion of the neck on the chest, hogtying |
- The sequence of events in asphyxia
- Dyspnea: expiratory dyspnea with raised respiratory rate, cyanosis and tachycardia
- Convulsive phase: loss of consciousness, reduced respiratory movement, facial congestion, bradycardia, hypertension
- Pre-terminal respiratory phase: no respiratory action, failure of respiratory and circulatory centers, tachycardia, hypertension
- Gasping for breath due to respiratory reflexes
- Terminal phase: loss of movement, areflexia, pupillary dilatation
- Non-specific signs of asphyxia
- Congestion and cyanosis of the face (or organs): due to venous congestion and excess deoxygenated hemoglobin
- Petechial hemorrhages (Tardieu’s spots): due to impaired integrity of capillary walls. Vary in size from pinpoint to pinhead
- Fracture of the larynx, hyoid bone, and associated cartilage
- Incontinence of feces, urine, and semen
- Specific signs of asphyxia
- Ligature marks: on the neck in hanging or ligature strangulation
- Fingernail abrasions and discoid bruises (six penny bruises): can be seen on the neck in manual strangulation
- Fluid in air passages and stomach: in case of drowning
- Foreign body in the larynx
Compression of the Neck
- Cause of death in compression of the neck
- Asphyxia: due to compression of the larynx and trachea, and elevation of the larynx and tongue closing the airway at the pharyngeal level
- Cerebral anoxia: due to venous congestion caused by compression of jugular veins, which stops cerebral circulation
- Reflex vagal inhibition: caused by pressure on the carotid bodies
- Cerebral anemia: pressure on the arteries of the neck produces cerebral anemia and immediate coma
- Fracture dislocation of cervical vertebrae (rare)
- Internal signs of neck compression
- Injury to the larynx: strangulation
- Laryngeal bleeding: strangulation and hanging
- Intramuscular bleeding: strangulation and hanging
- Intimal carotid artery laceration (Amussat’s sign): due to stretching which is seen in hanging
- Stripe-like hemorrhages on the ventral survace of IV disks (Simon’s bleeding): due stretching which is seen in hanging
Difference between hanging and strangulation
| Hanging | Strangulation by ligature | |
|---|---|---|
| Position of the mark | Oblique | Transverse |
| Amussat’s sign | Present | Absent |
| Simon’s bleeding | Present | Absent |
| Hangman’s fracture | Present | Absent |
Hanging
Hanging AKA self-suspension is a form of asphyxia caused by the suspension of the body by a ligature that encircles the neck. The constricting force in hanging is formed in part by the weight of the body.
Classification based on the positioning of the knot
| Classification | Description |
|---|---|
| Typical hanging | Knot or ligature is placed centrally over the occiput (nape of the back) |
| Atypical hanging | Knot or ligature is placed anywhere other than on the occiput |
Classification on the basis of degree of suspension
| Classification | Description |
|---|---|
| Complete hanging | Body is fully suspended. Constricting force is the weight of the body |
| Incomplete hanging | Lower part of the body is touching the ground or in sitting, kneeling, lying down or prone position. Constricting force is the weight of the head |
Cause of death in hanging
| Cause of death | Description |
|---|---|
| Asphyxia | Constricting forces cause compressive narrowing of laryngeal and tracheal lumen causing asphyxia |
| Venous congestion | Jugular veins are blocked by ligature which stops cerebral circulation. Caused by broad and soft ligature. |
| Combined asphyxia and venous congestion | Commonest cause |
| Cerebral anemia | Reduced blood flow to the brain. Caused by thin ligature. |
| Reflex vagal inhibition | This leads to sudden cardiac arrest |
| Fracture/dislocation of cervical vertebrae | Seen in judicial hanging (Hangman’s fracture). The knot is submental and the drop is at least the height of the victim. Fracture dislocation of C2/C3 or C3/C4 stretches and tears the cervical spinal cord. The odontoid process is usually not fractured in judicial hanging. |
- External findings in hanging
- Swollen, cyanosed face
- Prominent eyeballs
- Dilated pupils
- Sub-conjunctival hemorrhage
- Protrusion of the tongue (due to pressure on the floor of the mouth by ligature, may have bite marks with ‘marginal hemorrhages)
- Bleeding from nose/ears (due to impaired venous return)
- Cyanosis of the lips and mucous membranes
- Dribbling of saliva (surest sign of ante-mortem hanging, occurs from the angle opposite the knot)
- Ligature marks on the neck (Furrow -usually above the hyoid, runs obliquely, backward, non-continuous)
- Depressed, pale skin at the site of ligature (furrow and rope burns- may have post-mortem blisters on adjacent skin, and neck veins above the furrow may be distended)
- Slender and lengthened neck
- Neck flexed to the side opposite the knot
- Tardieu spots (on forehead, over eyelids, under the conjunctiva)
- Cyanosis of fingernails
- Glove and stocking post-mortem staining of the upper and lower limbs
- Clenched hands
- Penile turgidity and involuntary discharge of semen
- Involuntary discharge of fecal matter and urine
- Internal findings in hanging
- Dry, white, firm, and glistening subcutaneous tissue underneath ligature marks (platysma and SCM may have hemorrhaging or may be ruptured)
- Fractured hyoid bone (common in individuals more than 40 years old)
- Transverse carotid intimal tears (seen in obese individuals)
- Vertebral artery rupture, intimal tear and sub-intimal hemorrhage
- Congested larynx and trachea
- Fracture of the superior horn of the larynx
- Congested, distended and emphysematous lungs with Tardieu’s spots subpleurally
- Congested brain with Tardieu’s spots
- Congested abdominal organs
- Fluid blood which is purplish in colour
Strangulation
Strangulation is a form of violent asphyxia caused by constriction of air passage at the neck by means of ligature or by means other than suspension of the body
Classification of strangulation
| Classiciation | Description |
|---|---|
| Ligature strangulation | When ligature is used to compress the neck |
| Manual strangulation (throttling) | When human hands are used to compress the neck |
| Mugging | When the bend of an elbow/knee of an assailant is used to strangle a victim. Usually from behind, May leave no external or internal injury marks |
| Bansdola | When the neck is squeezed between two pieces of tied bamboo/stick |
| Garroting (Spanish windlass) | When the neck is compressed by a ligature which is quickly tightened by twisting with a lever (stick, ruler, or rod). Results in sudden loss of consciousness and collapse |
- External findings in strangulation
- Congested, swollen and cyanosed face
- Tardieu’s spots in the forehead, temples, eyelids and conjunctiva (more abundant than hanging)
- Prominent eyes with conjested conjunctiva, sub-conjunctival hemorrhage and dilated pupils
- Cyanosed lips, fingernails, and ear lobules
- Post-mortem lividity marked on the skin above th eligature
- Swollen, dark coloured tongue protruding out of the mouth with bite marks
- Blood-stained frothy fluid and mucus escaping from the mouth and nostrils
- Ligature marks (Furrow)
- Deep and prominent post-mortem staining
- Involuntary discharge of urine and fecal matter (seminal ejaculation is less common)
- Clenched hands and turgid genitals
- Abrasions, fingernal scratch marks, contusions in case of struggle (scratches are usually found on the skin of the neck near the ligature)
- Internal findings in strangulation
- Bruising of subcutaneous tissue and neck muscles
- Rarely injury to the hyoid bone (the level of constriction is below the hyoid with minimal traction on the thyrohyoid ligament)
- Fractured thyroid cartilage (one or both superior horns)
- Sub-capsular and interstitial thyroid hemorrhage
- Fracture of cricoid cartilage
- Fracture of tracheal rings
- Bruising at the root of the tongue and floor of the mouth
- Congested palatine lymphoid follicles
- Hemorrhagic infiltration of the mucosa of the pharynx, pyriform sinus, epiglottis and larynx
- Frothy bloodstained mucus at the larynx, trachea and bronchi
- Fracture dislocation of cervical vertebrae (uncommon, associated with twisting of the neck)
- Congested lungs with sub-pleural petechial hemorrhage
- Congested brain with petechiae in white matter
- All other organs are congested
Difference between hanging and strangulation
| Hanging | Strangulation | |
|---|---|---|
| Age | young, elderly adults | No age limit |
| Face | Pale, petechiae less common | Congested, livid with petechiae |
| Signs of asphyxia | less marked | marked |
| Tongue swelling and protrusion | less common | common |
| Bleeding from nose, ears, mouth | less common | common |
| Neck | stretched, elongated | not so stretched or elongated |
| Ligature mark (furrow) | oblique, non-continuous, above thyroid, pale hard and parchment-like | transverse, continuous, below thyroid, soft and reddish |
| Knot | single, simple, slip knot, on one side of neck | multiple, granny or reef type, tied with force |
| Abrasions and ecchymoses around the mark | less common | common |
| Involuntary discharge of feces and urine | less common | common |
| Involuntary discharge of seminal fluid | common | less common |
| Bruising of neck muscles | less common | common |
| Hyoid bone fracture | may occur | uncommon |
| Thyroid fracture | uncommon | common |
| Larynx and trachea fracture | uncommon | common |
| Emphysematous bullae on lungs | sometimes present | very common |
| Carotid arteries | intimal tears may be seen | rarely damaged |
| History | previous unsuccessful attempt may be present | no such history |
| Suicide note | usually present | not present |
| Place of occurrence | usually own bedroom with door and window bolted from inside, | Any place |
| Signs of struggle | absent | always present unless taken unaware |
Drowning
Drowning is a form of asphyxia caused by aspiration of fluid into the air passages by submersion in water or other fluids. A liquid-air interface is present at the entrance of the victim’s airway which prevents them from breathing oxygen.
Classification of drowning
| Classification | Description |
|---|---|
| Wet drowning | Water is inhaled into the lungs. Death due to cardiac arrest (ventricular fibrillation). Divided into fresh-water and salt-water drowning. |
| Dry drowning | Water does not enter the lungs. Death due to laryngospasm is caused by water rushing into the nasopharynx and larynx. A thick mucus foam plug may form plugging the airway. |
| Post-immersion syndrome (secondary drowning or near drowning) | The victim is resuscitated but dies from complications of drowning e.g. pulmonary oedema, ARDS, pulmonary infection, pneumonia, cerebral edema, DIC. A victim of near-drowning has survived beyond 24 hours after the submersion episode |
| Immersion syndrome (Hydrocution) | Cardiac arrest due to vagal inhibition as a result of contact with cold water or fright |
| Shallow water drowning (submersion of the unconscious) | Alcoholics, drugged, epileptics, infants, children and unconscious persons may die due to drowning in shallow water in a pit or drain |
Mechanism of fresh and sea water drowning
Lungs in Fresh-water drowning vs sea water drowning
| Fresh water drowning | Sea water drowning | |
|---|---|---|
| Size and weight | Ballooned, but light | Ballooned and heavy |
| Color | Pinkish | Purplish or bluish |
| Consistency | Emphysematous | Soft, jelly-like |
| Shape after removal from body | Retained, do not collapse | Not retained, flattens out |
| Cut section | Crepitus heard, little froth, no fluid | No crepitus, copious fluid and froth |
Antemortem drowning vs post-mortem submersion
| Antemortem drowning | Post-mortem submersion | |
|---|---|---|
| Froth over mouth and nostriles | Fine, lathery, appears spontaneously | Absent, if present it is coarse and not spontaneous |
| Cadaveric spasm in hands | Aquatic vegetation or mud may be present | Absent |
| Trachea and bronchioles | Presence of algae, mud along with frothy mucus | Absent |
| Lungs | Ballooned, bulky, edematous, bear indentations of the ribs | Collapsed, decomposed |
| Mud and algae in stomach and small intestine | May be present | Absent |
| Diatom and Gettler tests | Positive | Negative |
| Injuries | Consistent with drowning | Inconsistent with drowning |
| Suggestive signs | Water in middle ear, retracted genitals, cutis anserina, washer-woman’s hands, wet clothing, mud and sand | Water not present in middle ear |
- Cause of death in drowning
- Asphyxia
- Ventricular fibrillation (fresh water drowning)
- Fulminant pulmonary oedema (salt-water drowning)
- Vagal inhibition due to impact with water
- Laryngeal spasm
- Concussion (head injury)
- Apoplexy (cerebral hemorrhage)
- Secondary causes (septic aspiration pneumonia, sudden bursting of aneurysm)
- Exhaustion
- External findings in drowning
- Pale, bloated and discolored face with putrefaction
- Half open/closed eyes, suffused conjunctiva, and dilated pupils
- Swollen and protruded tongue
- Post-mortem lividity over the face, neck, front of upper part of chest, upper and lower limbs
- Fine, copious, white lathery froth at the mouth and nostril (reappears after wiping by itself or by applying pressure on the chest)
- Cutis anserina (due to contraction of erector pilorum muscles)
- Washerwoman’s hand (maceration of skin due to imbibation of water into its outer layers, fingertips occurs at 3-4 hours and whole hand by 24 hours)
- Retracted scrotum and penis
- Cadaveric spasms of the hand may have grass, mud, weeds or aquatic vegetations (materials indicate the place of submersion)
- Rigor mortis (especially after a violent struggle for life)
- Ante-mortem injuries sustained during fall into water
- Internal findings in drowning
- Voluminous and distended lungs (emphysema hydroaerique in case of wet drowning). Cut section exudes copious amounts of frothy blood-stained
- Flooded lungs with airless water (edema aquosum in case of unconscious drowning)
- Empty left side of the heart. Congested right side and venous system.
- Congested gray matter, softening and loss of gray-white junction
- Congested organs
- Presence of water and hemorrhage in middle-ear (positive proof of ante-mortem drowning)
- Water in the ethmoid and sphenoid sinuses
- Other conditions where froth is seen In these cases, froth is not as fine and of as large quantity or tenacious in nature as drowning
- Strangulation
- Electric shock
- Putrefaction
- Acute pulmonary edema
- Seizure
- Opium poisoning
- Diagnosis of drowning (summary)
- Froth
- Weeds and gravel/soil in hands
- Voluminous lungs
- Diatoms in tissues
Autoerotic Asphyxia
Autoerotic asphyxia is primarily caused by cerebral hypoxia achieved by neck ligature. The ligature can be voluntarily tightened and loosened. Failure to loosen the ligature, such as when the victim passes out, can lead to accidental ligature death. Other ways hypoxia to the brain is created include anaesthetic agent (”huffing”), positioning, and plastic bag. Sexual arousal is produced through asphyxia as decreased cerebral oxygenation induces a hallucinogenic state and euphoria with subsequent increase in sexual response. Hypoxia also alters central sexual inhibitor areas in the hippocampus and limbic system, and stimulates sympathetic neurons which are involved in penile erection.
Compression of the Chest (Traumatic Asphyxia)
Death is due to pressure and fixation of the chest and/or abdomen. The person is unable to breathe and dies of asphyxia. The non-specific signs of asphyxia are intensely pronounced with the neck and face grossly discoloured and the eyes an sclera engorged with blood.
Positional Asphyxia
Positional asphyxia is seen in individuals who are an inverted or head-down position an extended period of time. Mechanical and gravitation forces exert pressure on the diaphragm. In addition, venous return to the heart is impaired causing severe congestion of the brain and cerebral hypoxia. Hyper-flexion of the neck, jack-knife position and face down position (during inebriation) can also be fatal.
Cafe coronary (Accidental smothering)
Cafe coronary is when a healthy, but intoxicated person suddenly collapses and dies during a meal without signs of distress. Alcohol suppresses the gag reflex, causing the victim to suffer an airway obstruction. Autopsy reveals a large piece of poorly chewed food obstructing the larynx.
Toxic-Anoxic Death (Chemical Asphyxia)
Carbon Monoxide Poisoning
Carbon monoxide binds to hemoglobin 230 times greater than oxygen (anemic hypoxia/anoxia), displaces oxygen from the atmosphere (hypoxic hypoxia/anoxic anoxia), binds cytochromes A3 and P450 (histotoxic anoxia) and shifts the oxygen-dissociation curve to the left (tissue hypoxia/anoxia)
- Findings in carbon monoxide poisoning
- Cherry pink discoloration of the skin, mucous membranes, and viscera
- Pulmonary congestion and oedema
- Frothy fluid around the mouth and nose
- Visceral petechial hemorrhages
- Congestion and swelling of the brian
- Toxicological analysis
- Elevated blood carboxyhemoglobin level
- Alcohol or drugs may be present
Cyanide Poisoning
Cyanide combines with ferric iron of intracellular cytochrome oxidase, inhibiting their participation in intracellular oxidative metabolism (histotoxic anoxic)
- External examination findings in cyanide poisoning
- Cherry pink discolouration of the skin (slightly more blue)
- Excoriation of the face due to cyanide containing vomitus (cyanide is intensely alkaline)
- Internal examination findings in cyanide poisoning
- Smell of bitter almonds perceptible during opening of body cavities
- Corrosive changes in the mouth, pharynx, esophagus, and stomach
