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Forensics

Asphyxia

Author: Lindsey Harle, M.D. (see Reviewers page)
Revised: 3 June 2012, last major update June 2012
Copyright: (c) 2012, PathologyOutlines.com, Inc.

General
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● Asphyxia is the lack of oxygen supply to tissues/organs
● Types of asphyxia include suffocation, strangulation / hanging, positional / mechanical / traumatic

Suffocation
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● Definition: failure of oxygen to reach the blood

● Smothering: obstruction of nose and mouth
       ● Accidental: infant wedged between mattress and wall
       ● Suicidal: placing plastic bag over one's head and tightening around neck
       ● Homicidal: duct tape across nose and mouth, covering face with pillow, closing off nose and mouth of young child with hand
       ● Overlay: infant death due to parent onto child in bed; involves smothering and mechanical asphyxia
       ● No specific autopsy findings; may see signs of struggle (contusions/abrasions on face and mouth) in adult victims

● Choking: blockage of internal airways
       ● Accidental: large food bolus in airway, usually intoxicated adults, elderly with neurodegenerative disorders, young children
       ● Homicidal: gag placed in oropharynx
       ● Must find food bolus or other item in airway, or have report of its prior removal, to confirm choking

● Environmental: inadequate oxygen in atmosphere; also called entrapment
       ● Due to oxygen displacement by other gases (in silo), lack of oxygen in small enclosed space (child trapped in refrigerator)
       ● No specific autopsy findings

Strangulation / hanging
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● Definition: external pressure on neck resulting in compression of blood vessels and occasionally airway

● Strangulation: neck compression due to something other than the victim’s body weight, such as manual compression or ligature tightened by assailant; usually homicidal
       ● Ligature strangulation: the ligature mark on the neck is usually horizontal
       ● If homicidal (most common), may be signs of struggle (abrasions / lacerations and fingernail marks on neck)
       ● Suicidal strangulations can occur if individual ties cord or other ligature around neck with some sort of locking device
       ● Accidental strangulations can occur if scarf or necktie becomes trapped in doorway or other mechanical device

● Hanging: neck compression due to ligature around neck, with at least a portion of body weight being used to tighten ligature
       ● Usually suicidal; can be accidental (child trapped in cord) or homicidal
       ● Ligature mark on neck is oblique, with highest point usually at back of head, where ligature knot is tied
       ● This is in contrast to strangulation (usually homicide), where ligature mark is usually horizontal around neck
       ● Ligature mark may be absent if soft fabric (i.e. bed sheet) used as ligature
       ● May see pattern markings in ligature mark that correspond to patterns on ligature (i.e. weaved fabric, metal chain)

  ● 4 pounds of pressure required to occlude jugular veins (preventing venous drainage of head) and 5-11 pounds to occlude carotid arteries
  ● Loss of consciousness occurs in 10-15 seconds; death within 3-5 minutes
  ● May see facial and conjunctival petechiae at autopsy
  ● Fractures of hyoid bone, tracheal cartilage, cervical vertebrae are rare; hemorrhage in neck muscles also rare
  ● Hyoid fractures are more common in older victims, because hyoid bone is cartilaginous and incompletely ossified in children and young adults
  ● Injuries are more common if struggle between decedent and assailant
  ● In hanging, where body is completely suspended, autopsy may show congestion and petechiae of lower legs due to blood pooling
  ● May have no specific findings at autopsy

Positional / mechanical / traumatic asphyxia
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● Definition: position of body or external pressure on chest prevent respiration

● Positional asphyxia: body is positioned in a way that restricts airflow
       ● Twisting or compression of neck resulting in occlusion of oropharynx or trachea
       ● Seen in intoxicated individuals or elderly persons who become trapped

● Mechanical / traumatic asphyxia: external compression of chest, preventing normal respiration
       ● Example: vehicle collapsing on individual working under car
       ● May have petechiae, face and upper chest congestion at autopsy

● Chemical asphyxia: gases that prevent oxygen utilization at cellular level
       ● Carbon monoxide, hydrogen sulfide, cyanide

End of Forensics > Asphyxia

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