Asphyxia Lecture Notes

What is it? 

• Asphyxia: Interference with the uptake or utilization of oxygen.

• The brain utilizes 20% of the available oxygen.

• The brain is the most sensitive organ to oxygen deprivation.

Categories of Asphyxiation

• Compression of the neck:

  • Hanging

  • Strangulation

• Obstruction of the airway:

  • Smothering

  • Aspiration of foreign material

  • Swelling of the throat

    • Caused by allergic reactions or the inhalation of superheated air.

  • Postural/Positional asphyxiation.

  • Compression of the chest:

    • Interferes with respiratory movement.

  • Exclusion of Oxygen:

    • Due to gas depletion or replacement by another gas.

    • Chemical interference with O2 uptake and utilization

      • Includes carbon dioxide, carbon monoxide, and cyanide poisoning.

Hanging

• Death usually results from the lack of arterial blood flow to the brain or obstruction of venous return or both.

• Hanging can be performed in various body positions.

Petechiae and its Indicators

• Petechiae: Increased venous pressure ruptures capillaries.

• Commonly found in:

  • Conjunctivae

  • Eyelids

  • Forehead

• Petchial hemorrhages are found in over 50% of suicidal hangings.

Knot Placement Effects

• Knot behind the ears:

  • Interferes with blood flow to/from the brain.

  • More lateral pressure

• Knot under the chin:

  • Obstructs venous outflow.

Loss of Consciousness

• Resulting from brain depletion of oxygen:

• Requires 4-6 lbs. pressure to occlude carotid arteries and jugular veins.

• Average adult head weighs 10 lbs.

• 32 lbs. of pressure required to block the airway.

• Loss of consciousness leads to increased pressure from the added weight of body thereby cutting off all blood flow.

Compression in Hanging Cases

• Compression of the airway is uncommon in hanging cases.

• Fractures of cervical vertebrae are rarely observed.

Evidence of Hanging

• Hanging can be easily accomplished; various nooses can suffice.

  • Examples include belts, dog chains, etc.

• Ligatures often leave distinctive evidence, recognizbale evidence

• A groove or furrow in soft tissue can indicate the type of ligature used.

• An indented or abraded area often provides the location of the knot

Effects of a Noose

• Multiple wraps of the noose around the neck can pinch skin, altering its appearance.

• Friction or squeezing from tight nooses can cause serum-filled blisters.

• Tongue may protrude due to upward pressure from the ligature.

Strangulation

• Manual self-strangulation is generally infeasible.

• Preserve the knot 

• Manual strangulation is a homicide indication

  • May show fingertip bruises and fingernail marks.

  • Can have sexual motives, may include DNA evidence.

• May lack obvious external indicators of trauma.

Autopsy Considerations

• During autopsy, removal and assessment of neck organs is essential and required:

• Must look for fractures of the larynx:

  • Hyoid bone

  • Thyroid cartilage

  • Cricoid cartilage

Obstruction Types

• Smothering

  • Blockage of the nose and mouth

    • by pillows, plastic bags, bedding

    • Often are accidental

    • Infants are more prone to this

• Aspiration

  • Can occur due to intoxication/impairment, food, or vomitus.

• Swelling of the larynx lining:

  • Caused by insect bites, anaphylactic shock, epiglottitis, or diphtheria.

Positional/Compression Asphyxiation

• Occurs when the position of a person physically obstructs their ability to breathe.

• Other objects may also prevent breathing.