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
