ASPHYXIA

Definition

It is any condition that leads to: - reduction of the oxygen supply to

the blood and the tissues below the the normal physiological level (hypoxia).

- elevation of CO2 in the blood (hypercapnia).

**Hypoxia means (low oxygen) while anoxia means (without oxygen).

Types of anoxia:

(1) Anoxic anoxia:

- Ambient.

- Central.

- Paralytic.

- Mechanical (violent asphyxia).

- Obstruction of the blood flow to the lungs.

(2) Anemic anoxia:

- Chemically combined hemoglobin.

- Hemolysis.

- Hemorrhage.

(3) Stagnant anoxia.

(4) Histotoxic anoxia.

Stages of mechanical anoxia or violent asphyxia:

Three stages: (1) Stage of forced respiration:

- It is due to stimulation of the respiratory center.

- Clinical picture: DYSPNEA (2) Stage of convulsions:

- It is due to cerebral irritation.

- Clinical picture: CONVULSIONS, CYANOSIS, HYPERTENSION, LOSS OF CONSCIOUSNESS, CONSTRICTED PUPILS.

(3) Stage of paralysis:

- Clinical picture: LOSS OF CONSCIOUSNESS, FLACCID MUSCLES & LOST REFLEXES, DEEP CYANOSIS, DILATED PUPILS, IRREGULAR BREATHING (Cheyne-Stokes respiration).

**Death occurs in about 5 minutes..

General postmortem picture of mechanical anoxia:

- Deep cyanosis. - Proptosis of the eye balls. - Bloody froth from the nose and mouth. - Congested face with petechial

hemorrhage all over. - Dark violet or blue extensive hypostasis. ** All these are external signs N.B: Blood is dark and fluid in consistancy

due to increased CO2 and fibrinolysis respectively.

Hanging

Definition: It is the mechanical anoxic death due to

suspension of the body from the neck by a ligature.

Causes of death: - Cerebral ischemia. - Vagal cardiac inhibition. - Mechanical anoxia. - Transection of the spinal cord (judicial

hanging).

Post-mortem picture:

(1) General (2) Special features - Protrusion of the tongue. - Dribbling of saliva. - Hypostasis of the lower half of the body. - Neck signs: .Elongated and the head is tilted to the opposite

side of suspension point. .Ligature marks (HIGH UP in the neck, OBLIQUE,

INCOMPLETE, has an IMPRINT of the ligature).

** Homicidal, suicidal or accidental

Types of hangingPoint of comparison COMPLETE HANGING INCOMPLETE

HANGING

Other name High point hanging Low point hanging

Touching the ground Negative Positive

Circumstances Presence of a near-by table or chair

Negative

Main cause of death Cerebral ischemia Asphyxia

Face Less congested, sometimes pale

Markedly congested

Hypostasis Lower half of the body According to the part touching the ground

Type of knot Fixed knot or running noose

Always running noose

Rope marks -Incomplete with fixed knot-Above thyroid cartilage-Oblique-Deep and fades gradually towards suspension point

-Complete-Below thyroid cartilage-Transverse-Deep all through

Dribbling of saliva Positive Negative

Tear in carotid intima Positive Negative

Hyoid bone If fractured: outwards If fractured: inwards

Strangulation

Definition: It is the mechanical anoxic death caused

by constriction of the neck by a ligature occluding the air passages from outside.

Causes of death: - Mechanical anoxia. - Reflex cardiac inhibition. - Delayed edema of the glottis and

choking.

Postmortem picture of strangulation:

(1) General (2) Special features All are neck signs:

- Ligature marks:

. Low in the neck below the thyroid cartilage.

. Transverse.

. Complete.

. Deep all through.

. Abrasions and contusions taking the shape of the ligating material.

- Inward fracture of the hyoid bone and the thyroid cartilage may be fractured.

- Contusions and lacerations of the neck muscles.

**Homicidal, suicidal or accidental

Throttling «Manual strangulation»

Definition: It is the mechanical anoxic death caused

by constriction of the neck by the hand occluding the air passages from outside.

Causes of death: - Mechanical anoxia.

- Reflex cardiac inhibition.

- Cerebral anoxia.

- Delayed glottic edema and choking.

Postmortem picture:

(1) General (2) Special features All are neck signs

- Multiple contusions and fingernail abrasions.

- Inward fracture of the hyoid bone (it is the most common cause of hyoid bone fracture) and fracture of the thyroid cartilage.

- Contusions of the deep tissues of the neck.

** Homicidal, suicidal or accidental

Smothering

Definition: It is the mechanical anoxic death caused by occlusion of

the external respiratory openings by the hand or soft objects.

Causes of death: Mechanical anoxia

Postmortem picture of smothering: (1) General

(2) Special features - Multiple contusions and fingernail abrasions.

- Contusions in the buccal mucosa.

- Ventral hypostasis in cot death.

** Homicidal, suicidal or accidental

Traumatic asphyxia: Overlaying

Definition: It is the mechanical anoxic death

due to mechanical pressure by a heavy object on the chest with or without abdominal compression leading to prevention of respiratory movements.

Causes of death: - Mechanical anoxia. - Injury to vital organs.

Postmortem picture

(1) General (2) Special features - Contusions and abrasions of the chest and

abdomen.

- Fracture ribs.

- Rupture of internal organs.

- Line of demarcation between the discolored upper part of the body and the lower part.

** Homicidal, suicidal or accidental

Choking

Definition: It is the mechanical anoxic death caused by

occlusion of the respiratory passages from inside.

Causes of death: - Reflex cardiac inhibition

- Mechanical anoxia

Types: - Pathological

- Non-pathological

**Homicidal, suicidal or accidental

Drowning

Definition: It is the mechanical anoxic death due to

submersion of the respiratory openings under water.

Causes of death: - Direct causes: mechanical anoxia

- Indirect causes:

. Reflex cardiac inhibition due to vagal stimulation

. Head injury or other fatal injuries.

Posrmortem picture of drowning

- Sure external signs:

. Froth

. Cadaveric spasm - Probable external signs:

. Related to anoxic anoxia: cyanosis

. Related to presence of the body in water:

skin is pale&wet

Goose skin

Washerwoman skin

Postmortem injuries

. Affection of postmortem changes due to presence in water:

Cooling, hypostasis, adipocere, putrefaction

**Homicidal, suicidal or accidental