Asphyxiation Flashcards
Define asphyxia
Inference with oxygenation
Interference with oxygenation can occur
Environmental
Obstruction of external respiratory passages
- mouth and nose
Obstruction of internal respiratory passages
- pharynx, larynx, trachea, bronchi
Restriction of resp. movements
Lung disease
Heart disease
Oxygen transport - Hb, tissue utilisation
Stages of asphyxia
Struggle - forceful respiratory effort
Quiescence - unconscious
Convulsions - disturbance, incontinence
Apnoea - lifeless, weak pulse
Mechanism of death in asphyxia
Complex
Oxygen deprivaltion
Carbon dioxide accumulation
Reduced blood flow to brain - neck pressure
- jugular venous occlusion - venous stagnation
- carotid arterial occlusion - cerebral hypoxia
Vagal inhibition - reflex cardiac arrest
Pathological signs of asphyxia
General signs - common to many types of asphyxia - petechial haemorrhages - congestion - cyanosis - oedema Non-specific - absent from some asphyxial deaths - present in some non-asphyxial deaths
Features of petechial haemorrhages
Pinpoint size < 1mm Seen in lax facial tissue - tarsal plates - conjunctivae - inner aspects of lip - behind ears - facial skin Distribution is important - occur upstream of venous occlusion Punctate hypostasis coarser and occurs as part of post-mortem changes
Features of congestion, cyanosis and oedema
All due to obstruction of venous return Seen upstream of venous obstruction Most often apparent in face - above ligature around neck - chest compression Congestion - also affects tongue, pharynx and lungs Oedema - also affects lungs and brain
Damage can occur to structure in internal neck trauma
Hyoid bone Thyroid cartilage Cricoid cartilage Carotid artery Jugular vein Vagus nerve
Features of environmental asphyxia
Atmospheric oxygen low or absent - ship hold, scuba diving, anaesthesia, old fridge Death often rapid Signs often absent Scene and circumstances important
Features of methhaemoglobinaemia
Dusky purple hypostasis
Chocolate brown blood - seen in lungs
Features of suffocation
Often used as a general term for deprivation of O2 due to lack environmentally or external obstruction of airways
Homicidal soft smothering is obstruction to nose and mouth
- of infants and elderly by hand or pillow
Other types
- plastic bag asphyxia = suffocation + environmental
- overlaying of infants = suffocation + crush asphyxia
- gagging = secretion obstruction nasopharynx
General signs of asphyxia are often absent
Scene and circumstances are important
Features of plastic bag asphyxia
Suffocation + environmental asphyxia Voluntary euthanasia Death often rapid Pathological signs often absent Scene and circumstances are important - fastening of bag, masks
Features pointing to suicide in plastic bag asphyxia
Hands fastened to prevent backing out
Fully clothed
Suicide note
Often alcohol and drugs involved
Features of traumatic or crush asphyxia
Pressure fixation of chest wall and abdomen
- burial, trench collapse, crowds, under vehicle
External pressure interferes with ability to breath
Florid general signs
- petechiae, congestion, cyanosis, oedema
- seen both externally and internally
Specific external and internal injuries often slight
Features of positional asphyxia
Bodily position which obstructs airway or impairs the act of breathing
- typically associated with sedative intoxication - drugs and alcohol
- usually accidental
Restraint asphyxia is a variant in which chest, diaphragm and accessory muscles are impaired
- typically associated with stimulant intoxication
- common in psychiatric and custody situations
Features of choking
Obstruction of upper airway, between pharynx and tracheal bifurcation General signs variable - frothing at mouth and in airways - finding of object post-mortem Death often rapid - vagal inhibition Commonly - food - foreign body - toys, dentures
Features of hanging
Available, lethal and acceptable suicide method
Ligature pressure to neck
- by fixed or running loop
Pressure due to body weight
- by full or partial suspension of body
Obstruction of airway, arteries and veins
Leathery mark, rises to point of suspension
- link to ligature by hypostasis, pallor, abrasion
- angular upwards
- garrotte mark usually horizontal
General signs usually absent
- glove and stocking pattern of hypostasis if fully suspended
- pallor on pressure points if not fully suspended
- cricoid more commonly fractured in homicide
- fracture of hyoid bone - haemorrhage and angulation
Mechanism of death by hanging
Vagal inhibition Airway obstruction by displacement of tongue Occlusion of jugular veins Occlusion of carotid arteries - general signs usually absent Loss of consciousness in 15-30 secs Death in 1-2 mins Cervical fracture rare - seen in judicial hanging with drop
Features of sexual asphyxia
Accidental hanging
Failure of safety measures
Young males - often regular secret practice
Associated with transvestism, masochism and pornography
Scene is diagnostic
Parts needed for investigation of hanging
History Circumstances Photo of locus External examination Ligature
Features of ligature strangulation
Usually homicidal Ligature may be held, tied or twisted Florid general signs - due to raised HR etc Horizontal marks of uniform depth Skin bruises, scratch abrasions Deep neck muscle bruising Hyoid and thyroid features
Features of manual strangulation
Finger pad bruises, scratch or crescent abrasions
Shifting grips, various patterns, sleeper hold
Grip typically > 30 seconds
Florid general signs
Skin bruises
Scratch abrasions on neck
- attacker’s fingernails
- victim’s fingernails
Deep neck muscle bruising
Hyoid and thyroid fractures
Bruising internal/external on back due to downward pressure to hold perpetrator against neck
Features of inhalational asphyxia
Obstruction of lower airway, below trachea Seen most in children Accidentally Foreign bodies - toys, nuts Vomit - contentious diagnostic tissue - often agonal or PM artefact Drowning
