Asphyxia Flashcards
What are the 4 stages of asphyxia?
- Struggle - forceful respiratory effort.
- Quiescence - unconscious
- convulsions - disturbance, incontinence
- Apnoea - lifeless, weak pulse
Describe the complex mechanism of death in asphyxia.
Oxygen deprivation
CO2 accumulation
Reduce blood flow to brain (neck pressure) - jugular venous or carotid arterial occlusion
Vagal inhibition (reflex cardiac arrest)
neck pressure in asphyxia can occlude the jugular vein and cause ?
jugular venous occlusion -> venous stagnation
neck pressure in asphyxia can occlude the carotid arteries and cause ?
carotid arterial occlusion -> cerebral hypoxia
What are the general pathological signs common to many types of asphyxia?
petechial haemorrhages
congestion
cyanosis
oedema
These are non-specific and will be absent in some asphyxia deaths and present in others.
Where might you see petechial haemorrhages?
seen in lax facial tissues - tarsal plates, conjunctivae, inner aspects of lip, behind ears, facial skin.
Distribution of petechial haemorrhages is important - true or false
true
petechial haemorrhages occur UPSTREAM of venous occlusion
congestion, cyanosis and oedema are all due to … ?
obstruction of venous return
seen upstream of venous obstruction - most often apparent in the face e.g. above ligature around neck or chest compression
Internal neck trauma from asphyxia might effect which structures?
hyoid bone thyroid or cricoid cartilage carotid artery jugular vein vagus nerve
List the 7 types of “mechanical asphyxia”.
- environmental
- suffocation
- traumatic (crush) asphyxia
- choking
- hanging
- strangulation
- inhalational
A person found dead in a ship hold will have suffered which form of mechanical asphyxia?
environmental - e.g. ship hold, scuba diving (tight mask), anaesthesia, old fridge.
What is the mechanisms behind environmental asphyxia?
atmospheric oxygen is low or absent resulting in an often rapid death
signs often absent so scene and circumstances are important
A general term for deprivation of O2, due to lack in environment or external obstruction of airways = ?
suffocation
List the potential mechanisms of death in suffocation asphyxia.
Homicidal soft smothering (obstruction of nose & mouth)
Plastic bag asphyxia
Overlaying of infants
Gagging
plastic bag asphyxia is a mixture of which 2 mechanical asphyxias?
plastic bag asphyxia = suffocation + environmental
death often rapid with no pathological signs
An example of suffocation + crush asphyxia = ?
overlaying of infants = suffocation + crush asphyxia
What is the mechanism of death in gagging?
gagging is a form of suffocation asphyxia where secretions (oral/resp.) obstruct the nasopharynx.
Restraint and positional asphyxia are 2 subtypes of which mechanical type of asphyxia?
traumatic (crush) asphyxia
What is traumatic asphyxia and list some situational examples of this.
pressure fixation of chest wall and abdomen = traumatic (crush) asphyxia
e.g. burial, crowds, under vehicle
florid general signs are seen both externally and internally in crush asphyxia - true or false
TRUE
florid: petechiae, congestion, cyanosis, oedema
Person found buried under sand dune with visible cyanosis, oedema and petechiae. On autopsy, sand is also seen within oral cavity and larynx - explain
this is an example of traumatic (crush) asphyxia
There are florid general signs and specific internal sign of sand within respiratory passage
What is ‘burking’?
the way that burke and hare killed their victim’s by sitting on chest (traumatic asphyxia) + manual occlusion of nose and mouth (smothering)
Traumatic (crush) + smothering/suffocation
leaves little or no signs of trauma
Describe positional asphyxia and its typical associations.
Body position which obstructs the airway or imparts the act of breathing
Typically assoc. with sedative intoxication; usually accidental deaths.
Describe restraint asphyxia and its typical associations.
A variant in which chest, diaphragm and accessory muscles are impaired.
Typically associated with stimulant intoxication - common in psychiatric and custody situations.
A drunk person falling asleep at an awkward angle and not waking up …?
Positional asphyxia e.g. if neck was at right angle to chest, severely restricted air entry/exit
Obstruction of upper airway, between pharynx and tracheal bifurcation = ?
choking
“cafe coronary”
choking on unchewed food - obstruction of upper airway - rapid death due to vagal inhibition
oblique ligature mark on neck suggests suicide
true - mark rises to the point of suspension
horizontal mark suggests strangulation by killer
Describe the mechanism of death in hanging.
Vagal inhibition
Airway obstruction by displacement of tongue
Occlusion of jugular veins and carotid arteries
Loss of consciousness in 15-30s
Death in 1-2mins
Most hanging deaths have florid general signs and specific sign is cervical fracture - true or false
FALSE
general signs usually absent and cervical fracture is rare since judicial hangings no longer occur
Sexual asphyxia is a common homicidal manner of death - true or false
false
sexual asphyxia is usually an accidental hanging due to failure of safety mechanisms
Victim died of strangulation with florid general signs and a horizontal ligature mark - manner of death?
homicide
ligatures are usually horizontal mark of uniform depth (often at low level) is typical of homicide
What additional injuries might be seen in a homicidal strangulation?
Skin bruises, scratch abrasions
deep neck muscle bruising
hyoid and thyroid fractures
Person found dead with finger pad bruises, scratch and crescent abrasions on neck and face - manner and cause of death?
homicide
manual (“throttling”) strangulation and asphyxia
finger pad bruises might be consistent with shifting grips / various patterns
scratch abrasions on neck from attacker or victim’s fingernails
How long must a grip be in place to manually strangle someone?
typically >30s
obstruction of lower airway, below trachea = ?
inhalation asphyxia
A person that died following an obstruction below their trachea is seen to have vomitus on their shirt, is this sign diagnostic?
vomitus is a contentious diagnostic issue in inhalation asphyxia
the vomitus is often agonal or a PM artefact (not diagnostic)
