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Asphyxia - It is a condition caused by interference with respiration or due to lack of oxygen, which may cause unconsciousness & Death.

Classification of Asphyxia

1. Pathological
2. Toxic
3. Environmental
4. Traumatic
5. Positional
6. Iatrogenic
7. Mechanical

Mechanical Asphyxia

• In this type, Air-passage is blocked mechanically

It is divided into 2 periods

1. Pre-asphyxial period
1. It is a delay in breath
2. A person without any harm can delay breath for 10–15 seconds.
3. If the obstacle is not removed between 10–15 seconds, the next period develops.
2. Asphyxial period (It has 4 stages)
1. Stage of Dyspnea with convulsions
1. It is expressed by enhanced deep inspiration at which organism tries to compensate lack of oxygen.
2. Stage of Relative Rest
1. Short respiratory stand-still due to depression of functions of Respiratory center.
3. Stage of Terminal breath
1. Appears at 4th or 5th minute, when deep breath and pauses develops.
4. Terminal stage
1. It is complete respiratory standstill. Heart can function within 5–30 minutes.

Classification of Mechanical Asphyxia

1. Strangulation (external pressure on neck)
1. Hanging
2. Ligature strangulation
3. Strangulation by hands
2. Obstruction of external respiratory airways
1. Closure of external respiratory orifices (Ex : Smothering)
2. Closure of airways by impactation of foreign bodies (Ex : Chocking)
3. Closure of airways by fluid (Ex : Drowning)
3. External compression of chest/abdomen
4. Insufficiency of oxygen in inspired air.

Pathology of Asphyxia

1. Asphyxia
2. Capillary dilation
3. Stasis
4. Reduced venous return to heart
5. Reduced pulmonary blood flow
6. Deficient oxygenation
7. Further Asphyxia

Hanging

• It is a form of Asphyxia which is caused by suspension of body by a ligature (loop), which encircles the neck, the constricting force being weight of the body.

Classification of Ligatures (Loops)

1. According to material
1. Hard (Metallic chains & Wires)
2. Semi hard (Leather, belt)
3. Soft (Saree, bed-sheet)
2. According to device of knot
1. Running
2. Fixed
3. Depending upon number of turns of the ligature around the neck
1. Single
2. Double
3. Multiple

Causes of death at Hanging

1. Asphyxia
1. The constricting force of ligature causes compression, narrowing of lumens of larynx and trachea
2. It forces up the root of tongue against the posterior wall of Pharynx
3. And folds the epiglottis over the entrance of larynx to block the airway
2. Venous Congestion
1. The jugular veins are blocked by compression of ligature
2. It results in stoppage of cerebral circulation
3. Combined asphyxia and venous congestion
4. Cerebral anemia
1. Pressure on large arteries on the neck produces cerebral anemia and coma
5. Reflux vagal inhibition
1. From pressure on vagal sheath or caratoid bodies
6. Fracture of cervical vertebrae.

Post-Mortem Appearances in Hanging

1. External apperances
1. Neck is stretched due to upward pull of ligature
2. Head is always inclined to the side opposite to the knot due to gravitational forces.
3. Face is pale
4. Eyeballs appear prominent due to congestion
5. Tongue is protrude due to pressure by ligature at its base
6. Bloody mucus can escape from mouth and nostrils.
2. Ligature Mark
1. It is imprint of loop on skin of neck
2. It is pale in color, later becomes yellowish
3. Ligature mark usually encircles the entire neck, except for place, where knot was located.
4. Mark is located above the level of thyroid cartilage.
5. Character of ligature mark depends on :
1. Nature of ligature (Thin rope or saree)
2. Tightness of encircling ligature
3. Number of turns of ligature around the neck
4. weight of the body
5. Length of time body has been suspended.