Asphyxia

Question 1

What are the 4 stages of asphyxia?

Answer 1

1. Struggle - forceful respiratory effort.
2. Quiescence - unconscious
3. convulsions - disturbance, incontinence
4. Apnoea - lifeless, weak pulse

Question 2

Describe the complex mechanism of death in asphyxia.

Answer 2

Oxygen deprivation
CO2 accumulation
Reduce blood flow to brain (neck pressure) - jugular venous or carotid arterial occlusion
Vagal inhibition (reflex cardiac arrest)

Question 3

neck pressure in asphyxia can occlude the jugular vein and cause ?

Answer 3

jugular venous occlusion -> venous stagnation

Question 4

neck pressure in asphyxia can occlude the carotid arteries and cause ?

Answer 4

carotid arterial occlusion -> cerebral hypoxia

Question 5

What are the general pathological signs common to many types of asphyxia?

Answer 5

petechial haemorrhages
congestion
cyanosis
oedema

These are non-specific and will be absent in some asphyxia deaths and present in others.

Question 6

Where might you see petechial haemorrhages?

Answer 6

seen in lax facial tissues - tarsal plates, conjunctivae, inner aspects of lip, behind ears, facial skin.

Question 7

Distribution of petechial haemorrhages is important - true or false

Answer 7

true

petechial haemorrhages occur UPSTREAM of venous occlusion

Question 8

congestion, cyanosis and oedema are all due to … ?

Answer 8

obstruction of venous return
seen upstream of venous obstruction - most often apparent in the face e.g. above ligature around neck or chest compression

Question 9

Internal neck trauma from asphyxia might effect which structures?

Answer 9

hyoid bone
thyroid or cricoid cartilage
carotid artery
jugular vein
vagus nerve

Question 10

List the 7 types of “mechanical asphyxia”.

Answer 10

1. environmental
2. suffocation
3. traumatic (crush) asphyxia
4. choking
5. hanging
6. strangulation
7. inhalational

Question 11

A person found dead in a ship hold will have suffered which form of mechanical asphyxia?

Answer 11

environmental - e.g. ship hold, scuba diving (tight mask), anaesthesia, old fridge.

Question 12

What is the mechanisms behind environmental asphyxia?

Answer 12

atmospheric oxygen is low or absent resulting in an often rapid death
signs often absent so scene and circumstances are important

Question 13

A general term for deprivation of O2, due to lack in environment or external obstruction of airways = ?

Answer 13

suffocation

Question 14

List the potential mechanisms of death in suffocation asphyxia.

Answer 14

Homicidal soft smothering (obstruction of nose & mouth)
Plastic bag asphyxia
Overlaying of infants
Gagging

Question 15

plastic bag asphyxia is a mixture of which 2 mechanical asphyxias?

Answer 15

plastic bag asphyxia = suffocation + environmental

death often rapid with no pathological signs

Question 16

An example of suffocation + crush asphyxia = ?

Answer 16

overlaying of infants = suffocation + crush asphyxia

Question 17

What is the mechanism of death in gagging?

Answer 17

gagging is a form of suffocation asphyxia where secretions (oral/resp.) obstruct the nasopharynx.

Question 18

Restraint and positional asphyxia are 2 subtypes of which mechanical type of asphyxia?

Answer 18

traumatic (crush) asphyxia

Question 19

What is traumatic asphyxia and list some situational examples of this.

Answer 19

pressure fixation of chest wall and abdomen = traumatic (crush) asphyxia
e.g. burial, crowds, under vehicle

Question 20

florid general signs are seen both externally and internally in crush asphyxia - true or false

Answer 20

TRUE

florid: petechiae, congestion, cyanosis, oedema

Question 21

Person found buried under sand dune with visible cyanosis, oedema and petechiae. On autopsy, sand is also seen within oral cavity and larynx - explain

Answer 21

this is an example of traumatic (crush) asphyxia

There are florid general signs and specific internal sign of sand within respiratory passage

Question 22

What is ‘burking’?

Answer 22

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

Question 23

Describe positional asphyxia and its typical associations.

Answer 23

Body position which obstructs the airway or imparts the act of breathing
Typically assoc. with sedative intoxication; usually accidental deaths.

Question 24

Describe restraint asphyxia and its typical associations.

Answer 24

A variant in which chest, diaphragm and accessory muscles are impaired.
Typically associated with stimulant intoxication - common in psychiatric and custody situations.

Question 25

A drunk person falling asleep at an awkward angle and not waking up …?

Answer 25

Positional asphyxia e.g. if neck was at right angle to chest, severely restricted air entry/exit

Question 26

Obstruction of upper airway, between pharynx and tracheal bifurcation = ?

Answer 26

choking

Question 27

“cafe coronary”

Answer 27

choking on unchewed food - obstruction of upper airway - rapid death due to vagal inhibition

Question 28

oblique ligature mark on neck suggests suicide

Answer 28

true - mark rises to the point of suspension

horizontal mark suggests strangulation by killer

Question 29

Describe the mechanism of death in hanging.

Answer 29

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

Question 30

Most hanging deaths have florid general signs and specific sign is cervical fracture - true or false

Answer 30

FALSE

general signs usually absent and cervical fracture is rare since judicial hangings no longer occur

Question 31

Sexual asphyxia is a common homicidal manner of death - true or false

Answer 31

false

sexual asphyxia is usually an accidental hanging due to failure of safety mechanisms

Question 32

Victim died of strangulation with florid general signs and a horizontal ligature mark - manner of death?

Answer 32

homicide

ligatures are usually horizontal mark of uniform depth (often at low level) is typical of homicide

Question 33

What additional injuries might be seen in a homicidal strangulation?

Answer 33

Skin bruises, scratch abrasions
deep neck muscle bruising
hyoid and thyroid fractures

Question 34

Person found dead with finger pad bruises, scratch and crescent abrasions on neck and face - manner and cause of death?

Answer 34

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

Question 35

How long must a grip be in place to manually strangle someone?

Answer 35

typically >30s

Question 36

obstruction of lower airway, below trachea = ?

Answer 36

inhalation asphyxia

Question 37

A person that died following an obstruction below their trachea is seen to have vomitus on their shirt, is this sign diagnostic?

Answer 37

vomitus is a contentious diagnostic issue in inhalation asphyxia
the vomitus is often agonal or a PM artefact (not diagnostic)