1. بسم الله الرحمن الرحيم

2. Asphyxia

3. Objectives
To know the definition of asphyxia. To know the types of asphyxia. To know the different types ,mechanism of death and postmortem picture of mechanical asphyxia. To know the definition of drowning. To know the postmortem picture of drowning.

4. Asphyxia :- The literal translation of the word ‘asphyxia’ from the Greek means ‘absence or lack of pulsation’;quite how this word has came to denote the effects of ‘the lack of oxygen’ is not clear, but it is now a word commonly used to describe a range of conditions for which the lack of oxygen, whether it is partial (hypoxia) or complete (anoxia), is considered to be the cause In forensic medicine, asphyxia often describes a situation where there has been a physical

5. obstruction between the mouth and nose to the alveoli, although other ‘asphyxial mechanisms’exist, in which there is an inability to utilize oxygen at the cellular level without there being a physical airway obstruction. The term asphyxia is not a term frequently used in clinical medicine and, given the incomplete understanding of the pathophysiology of many deaths occurring following the application of pressure to the chest and neck, for example, its use as a useful descriptive term in such scenarios is perhaps questionable.

6. Types of anoxia
I- Anoxic anoxia II- Anemic anoxia III-Stagnant anoxia IV- Histotoxic anoxia

7. 1- anoxic anoxia
A- ambient: decrease oxygen in atmosphere as in high altitude or presence of irrespirable gas (CO 2 or N2). B- Central :- depression of the respiratory center as in overdose of central depressant drug( eg :- morphine) , medullary herniation ,electrocution.

8. C- Paralytic :- Paralysis of the respiratory muscles as in overdose of succinylcholine or curare , botulism D- Mechanical (violent asphyxia):- 1-Occlusion of the respiratory openings(smothering) 2- Occlusion of the respiratory passages in the neck(hanging ,strangulation and throttling). 3-Prevention of the respiratory movement as in convulsion or overlying

9. 4- Internal obstruction of the airway by:- A) foreign body causing chocking B)water as in drowning C)glottic edema 5- acute pulmonary edema E- Obstruction of the blood stream to the lungs as pulmonary embolism.

10. II –Anemic Anoxia
It occurs due to decrease in the oxygen carrying capacity of blood e.g:Hemorrhage ,hemolysis of the blood or chemically combined hemoglobin as in CO poisoning or methemoglobinemia

11. III- Stagnant Anoxia
It is the interference with the blood flow to tissues as in advanced heart failure, vagal or histamine shock.

12. IV-Histotoxic anoxia
It occurs due to decrease the ability of cells to utilize oxygen as in cyanide poisoning or exposure to extreme cold.

13. Stages of mechanical asphyxia
1- Forced respiration. 2- Convulsions 3-Paralysis 4- Gasping

14. Dyspnea phase – expiratory dyspnea with raised respiratory rate,cyanosis and tachycardia (may last for a minute or more) ● Convulsive phase – loss of consciousness, reduced respiratory movements, facial congestion, bradycardia, hypertension, fits (may last for a couple of minutes) ● Pre-terminal respiratory phase – no respiratory action, failure of respiratory and circulatory centres, tachycardia, hypertension (may last a couple of minutes)

15. Gasping for breath – respiratory reflexes Terminal – loss of movement, areflexial, pupillary dilatation

16. Classical external signs of mechanical asphyxia
1- Deep cyanosis 2- Petechial hemorrhage 3-Dark violet or blue hypostasis

19. Types of violent asphyxia
1- Hanging 2- Strangulation 3- Throttling 4- Smothering 5- Choking

20. 1- Hanging
Definition:- It is a type of violent asphyxia and death occurs due to suspension of the body from the neck by ligature tightened by the weight of the body.

21. Types :- 1- Complete :-all body weight is applied to constrict the neck. 2-Incomplete:- partial body weight is applied to constrict the neck as a body part is touching the ground(eg knee ,foot). Ligature applied :- Either fixed knot or slipknot(the end of the rope passes through a loop).

22. Mechanism of death:- 1- Cerebral ischemia 2- Anoxic anoxia 3- Reflex cardiac inhibition 4- Spinal cord – brainstem disruption

23. External postmortem picture:- 1- facial signs:- The face may be congested or pale according to the applied force in the neck. In cases of complete hanging there is pallor due to complete occlusion of both carotid and vertebral circulations ,while in case of incomplete hanging the face is congested due to occlusion of jagular veins artery but the vertebral vessels not occluded.

26. 2-The tongue is protruded , 3-Dribbling of saliva 4-The head is tilted to the opposite side of the point of suspension. 5- The ligature mark :- in the form of abrasions and contusions , it takes the shape of the suspended articles

27. In case of hanging with fixed knot the ligature marks is high up in the neck above the thyroid cartilage, running obliquely upwards and deepest opposite the point of suspension and fades upwards gradually to be absent at the site of the knot.

28. Manner of death :- 1- Suicidal hanging is the most common type
Manner of death :- 1- Suicidal hanging is the most common type. 2- Accidental may occur(e.g:- in case of children). 3- Homicidal hanging is very rare.

29. Suicidal hanging: the rope rises to a point, leaving a gap in the ligature mark – the suspension point – on the neck

30. Fracture of the left superior horn of the thyroid cartilage following strangulation

31. deep furrowed ligature mark under the chin,and rising to the back of the neck, in hanging. Note the spiral weave pattern visible in the parchmented mark.

33. Judicial The sudden braking of the body by the noose after a drop of several feet leads to fracture and/or dislocation of the cervical spine–either at the atlanto-occipital joint, the atlanto-axial joint, or in the mid-cervical portion of the spine–with high spinal cord or brain stem injury leading to sudden death.

34. (Auto erotic asphyxial deaths may involve elements of strangulation or hanging. They usually involve males and occur in isolated or sites. There may be evidence of transvestitism, mirrors, cameras, etc.)

35. 2- Strangulation
Definition:- It is a type of violent asphyxia and death occurs due to constriction of the neck by a ligature that is tightened by a force rather than y the weight of the body.

36. Mechanism of death:- 1- Anoxic anoxia is the most important mechanism
Mechanism of death:- 1- Anoxic anoxia is the most important mechanism. 2- Reflex cardiac inhibition. 3- Edema of the glottis.

37. External postmortem picture:- 1-General :- the classical signs of violent asphyxia as congested face ,petechiae, proptosis of eye balls, subconjunctival hemorrhage and bloody discharge from mouth ,nose and ears . NB:- the face in strangulation is severly congested All these signs is absent if death occurs due to reflex cardiac inhibition.

38. 2- Special features:- A- ligature marks :-low in the neck ,below thyroid cartilage, transverse,complete and deep all through. B- abrasions and contusions may be absent if the material is soft.

39. Manner of death:- 1- Homicidal is the most common 2- Accidental may occur in children or strangulation of the fetus by the umbilical cord 3- Suicidal is rare by using a plastic lock tie ,or a rope which was turned many times or by a piece of wood which applied between the rope and the neck then twisted.

40. 3- Throttling(manual strangulation)
Definition:- It is a type of violent asphyxia and death occurs due to constriction of the neck by hands. Mechanism of death:- 1- Reflex cardiac inhibition is the most important mechanism and gives postmortem picture of vagal shock 2- anoxic anoxia:-Delayed edema of the glottis.

41. External postmortem picture 1- General 2-Special features :- Fingernail abrasions and contusions in the neck these marks may be absent if there is interfering material between the assailant hands and victim neck. Manner of death:- Homicidal is common

43. IV- Smothering
Definition:- It is a type of violent asphyxia and death occurs due to occlusion of the external respiratory openings by hand or soft objects. Mechanism of death:- Anoxic anoxia.

44. Post mortem picture:- 1- General:- The classical signs of violent asphyxia are rare. 2- Special features:- Multiple contusions of the fingers and nails abrasions on the skin around the external respiratory openings ,these signs may be absent if soft objects (towel or pillow) were used.

45. Postmortem Examination in such cases rarely reveals any of the ‘classic asphyxial signs’.Similarly, smothering – the physical occlusion of the nose and mouth – may leave no ‘asphyxial signs’ in survivors or the deceased. If the individuals are unable to struggle, owing to extremes of age or intoxication, for example, they may have no evidence of injury, including around the mouth or nose.

46. Occasionally, examination will reveal intraoral injury (including bruising or laceration of the insides of the lips or bruising of the gums in individual).

47. Manner of death:- 1- Homicidal is common in infants and unconscious victims. 2- Accidental may occurs as in cases of cot death , accidental placing a plastic bag or sheet over the child head and face or closing the infant mouth and nose by the breast of his mother. 3- Suicidal by using a plastic bag .

48. Suicidal plastic bag asphyxia
Suicidal plastic bag asphyxia. Suffocation by plastic bag often leaves no autopsy asphyxial signs, and removal of the bag by another individual prior to autopsy would cause signifiant interprétations problems.

49. V- Choking
Definition:- It is a type of violent asphyxia and death occurs due to occlusion of the air passages (inside the respiratory passage).

50. Types of choking
1- Pathological :- due to certain diseases as diphtheria, angioneurotic edema or tumors. 2- Accidental:- Inhalation of toxic fumes ,inhalation of dust and sands in falling houses,impaction of foreign bodies as meat , coin ,gauze in operations, teeth ,blood or vomitus.

51. 3- Homicidal :- in infant and unconscious adults (by pushing a piece of cotton or cloth inside the mouth and pharynx). Mechanism of death:- A- reflex cardiac inhibition due to trauma to the larynx B- anoxic anoxia External post mortem picture:- According to the mechanism of death

52. CRUSH (TRAUMATIC) ASPHYXIA
This is caused by compression of the thorax/abdomen by a heavy weight e.g. a collapsed building, overturned vehicle, or stampeding spectators e.g. at a crowded stadium.

53. Respiratory movements are prevented and blood is forced into the head and neck. This produces a characteristic deep engorgement and cyanosis with large petechiae in the head, neck and upper body. Some cases of overlaying (see “Smothering”) may have a component of crush asphyxia.

54. Traumatic asphyxiation in the workplace: (a) there is gross congestion of the head and face, with petechiae following burial, up to the axillae,

55. DROWNING Definition:-
This is defined as asphyxial death due to submersion in water or other fluid.
Complete submersion not necessary,submersion of nose and mouth is enough.

56. Mechanism of Drowning :- Death is primarily due to hypoxia by exclusion of air from the lungs, but is largely due to electrolyte imbalance and/or haemolysis from the effects of inhaled water on the blood. When water is inhaled into the lungs, the respiratory movements mix it with mucus and surfactant producing the fine stable froth that is characteristically seen.

57. Fresh Water Drowning:- The hypotonic water enters the blood via the pulmonary capillary bed leading to hypervolaemia, haemodilution, haemolysis and electrolyte imbalance which serve to hasten death.

58. Salt Water Drowning:- The hypertonic seawater extracts water from the blood in the pulmonary circulation leading to haemoconcentration and electrolyte imbalance. The latter is not as severe because there is neither hemolysis nor hypervolemia and therefore death in salt water drowning may be 4 to 5 times slower than in fresh water drowning.

59. N.B. A person may be said to have died from drowning up to 24 hours after having been immersed in water! Having survived the actual immersion, it is possible to die later from any or a combination of the following: pulmonary (alveolar) damage – adult respiratory distress syndrome (ARDS), electrolyte imbalance, hypoxic brain injury etc.

60. "Dry Drowning" This refers to submersion in water leading to sudden death without the typical features of drowning being seen. The 2 causes postulated for this are: (i)Vagal inhibition – such as might occur in sudden submersion in cold water, or falling unexpectedly into water.

61. (ii)Laryngospasm – sometimes, even in expert swimmers, entry of water into the larynx may lead to sudden, severe laryngeal spasm and an asphyxial death, effectively due to choking! In such a case, one might see signs of asphyxia without typical features of drowning.

62. Postmortem findings External
Signs of submersion e.g. sodden clothing..
The skin of the finger,palms and later the soles of the feet may be wrinkled,bleached and sodden.
Due to osmotic action of water,on thickened epidermis.
This immersion changes known as Hands and Feet of a Washer-Woman.
Goose skin.
Signs suggestive of drowning i.e. indications that the victim was alive when he/she entered the water e.g. objects from the water or shore/river bank clutched in the hand e.g. weeds, gravel, sand etc.

63. Persistent, fine, white froth at nostrils and mouth.
Signs of asphyxia e.g. petechiae are NOT usually seen.
Internal:-
Fine froth lines the trachea, bronchi and distal air passages.
Voluminous, sodden, heavy lungs, which may be indented by the ribs; pressure from a finger will leave an indentation.
Water in the stomach (seen in up to 70% of cases).

64. Confirmation tests for drowning
1) Diatom identification/analysis:- Diatoms are microscopic, unicellular algae with heat and acid resistant shells of silica and are found in most bodies of fresh or seawater. At autopsy, specimens from liver, kidney, brain and bone marrow can be digested with concentrated mineral acids.

65. If diatoms are found, this provides strong evidence of drowning, as in order for these organisms to have reached the aforementioned organs, they would have had to be absorbed from the pulmonary vascular bed and carried to these organs by a dynamic systemic circulation.

66. Note that:-
The lung tissue itself is not used to test for diatoms because these might be present in cases of mere submersion of a previously deceased person due to passive influx of water into the lungs.
A positive diatom test is especially valuable where putrefaction has rendered other methods of diagnosis useless.

67. 2) Middle ear hemorrhages are characteristic (though not specific) of death by drowning. They are thought to be related to barometric pressure. 3) Biochemical tests e.g. in fresh water drowning, blood from the left heart will be more dilute than that from the right; and the reverse will occur in salt water drowning. These tests are relatively non-specific.(due to enterance of water through lungs to pulmonary circulation to the left side directly).

68. Diatoms from lake water.

69. Frothy fluid exuding from the mouth following drowning

72. Thank you