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Forensic Medicine > Asphyxia > Flashcards

Asphyxia Flashcards

1
Q

Where did the word asphyxia come from

A

Greek derivation:

“absence of pulsation”

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2
Q

What is the forensic definition of asphyxia

A

Interference with oxygenation

This is the one we use

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3
Q

Describe the structure of the cricoid cartilage

A

Signet ring shaped cartilage

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4
Q

Describe the structures of the hard and soft palate

A

Hard is a bone structure
Transitions into the soft palate
This is a softer tissue - responsible for snoring

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5
Q

Where would a tracheostomy be placed

A

Gap in between thyroid and cricoid cartilages

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6
Q

List caused of oxygenation interference

A

Environmental
Obstruction of external respiratory passages - mouth & nose
Obstruction of Internal respiratory passages - pharynx, larynx, trachea, bronchi
Restriction of resp. movements
Lung disease
Heart disease
Oxygen transport issues

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7
Q

List some medical conditions that can lead to asphyxia

A

Pneumonia
Fluid on the lungs
Basically anything that interferes with gas transfer
Can also increase risk from asphyxia if chronic as less reserve/ tolerance to damage

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8
Q

How can direct force to the neck affect the spine

A

Direct force can compress neck cartilage/bone and compress/fracture into the spine at the back
Superior horns of thyroid cartilage prone to fracture
Hyoid bone also a risk

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9
Q

List the types of mechanical asphyxia

A 
Environmental - e.g. CO 
Suffocation
Traumatic (Crush) Asphyxia
Choking
Hanging
Strangulation
Inhalation
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10
Q

List the 4 stages of asphyxia

A

Struggle
Quiescence
Convulsions
Apnoea

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11
Q

What occurs during the struggle phase of asphyxia

A

Forceful respiratory effort
Associated signs may not be as enhanced in suicide (compared to homicide)
The longer you are conscious the more struggle signs

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12
Q

What occurs during the quiescence phase of asphyxia

A

The victim will fall unconscious

Can occur very quickly with some types of asphyxia

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13
Q

What occurs during the convulsion phase of asphyxia

A

Disturbance
Incontinence
Often agonal events

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14
Q

What occurs during the apnoea phase of asphyxia

A

Victim becomes lifeless and pulse is weak

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15
Q

What are the mechanisms of death in asphyxia

A

It is a complex process
O2 deprivation and CO2 accumulation
The neck pressure reduces the blood flow to the brain
Vagal inhibition can lead to reflex cardiac arrest

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16
Q

How does carbon monoxide poisoning cause asphyxia

A

CO takes the place of oxygen and interrupts its transport

There is no normal O2 circulating

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17
Q

What would happen if you covered the nose and mouth of someone with a tracheostomy

A

It would not have an effect on their breathing - e.g. they will not asphyxiate
They breathe from the trach lower down

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18
Q

Is death always due to a single type of asphyxia

A

No

Different causes can overlap and contribute to death

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19
Q

What is meant by overlying children

A

When you roll onto them or sleep on top of them

Causes asphyxia but little struggle

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20
Q

Longer you are conscious the more signs of asphyxia are produced - true or false

A

True

This is because you struggle for longer

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21
Q

What effect does jugular venous occlusion have

A

Causes venous stagnation
Blood cannot leave the head/neck
This can lead to swelling in the brain and loss of oxygen

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22
Q

What effect does carotid artery occlusion have

A

Leads to cerebral hypoxia

Oxygenated blood cannot enter the head/neck

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23
Q

List the general pathological signs of asphyxia

A

Petechial haemorrhages
Congestion
Cyanosis
Oedema

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24
Q

Petechial haemorrhages, congestion, cyanosis and oedema are all specific to asphyxia deaths - true or false

A

False
These are non specific signs - especially c,c and o
They are present in some non-asphyxia deaths and absent from some asphyxia cases
Can add weight to conclusions though

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25
Q

Describe the appearance of petechial haemorrhages

A

Pinpoint size (<1 mm)
Red colour
Can coalesce

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26
Q

What can distribution of petechial haemorrhages tell you

A

They occur upstream of the venous occlusion so tell you where this was

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27
Q

On which tissues will you commonly see petechial haemorrhages

A 
Tarsal plates - eyelids
Conjunctivae - usually florid 
Inner aspects of lip - mucosa
Behind ears
Facial skin - skin lax and thin
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28
Q

What causes congestion, cyanosis and oedema

A

All due to obstruction of venous return

The signs will be seen upstream of the occlusion as a result (e.g. above the ligature)

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29
Q

In which tissues do you often see congestion post asphyxia

A

Face
Tongue
Pharynx
Lungs

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30
Q

In which tissues do you often see oedema post asphyxia

A

Face
Lungs
Brain

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31
Q

In which part of the body are you most likely to see congestion, cyanosis and oedema

A

Most often apparent in the face
Above ligature around neck or due to chest compression
Occurs above the occlusion due to backpressure

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32
Q

What causes environmental asphyxia

A

This occurs when atmospheric O2 is low or absent

e.g. CO poisoning, anaesthesia, scuba, ship holds

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33
Q

Which structures in the neck are vulnerable to trauma

A 
Hyoid bone
Thyroid cartilage
Cricoid cartilage
Carotid artery
Carotid bodies - may cause arrhythmia 
Jugular vein
Vagus nerve - cardiac arrest
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34
Q

List causes of environmental asphyxia

A

Ships hold
Scuba diving (recreational or work) - equipment failure or just running out of O2
Enclosed breathing apparatus and enclosed spaces
Industrial chemicals - steal space from O2 in room and body
CO from faulty household goods like fridges

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35
Q

What causes petechial haemorrhages

A

Vein occlusion during asphyxia causes blood to back up in the venules (path of least resistance)
Venules get disrupted due to backpressure
As these are weak vessels they can rupture
They are pushed up to the skin in thin areas which causes the visible haemorrhage

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36
Q

The more prolonged the struggle the more petechial haemorrhage will be seen - true or false

A

True - in theory
The more prolonged the struggle the more prolonged the pressure to the vein which leads to more haemorrhages
Struggle also increases the stress response = higher BP = more haemorrhage

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37
Q

How long does it take petechial haemorrhages to form

A

Can take between 8-10 seconds for them to be produced

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38
Q

What process is essential for the formation of petechial haemorrhage

A

Must have some occlusion to the veins during life

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39
Q

What does bleeding in the middle ear suggest

A

Prolonged struggle

Not necessarily against assailant - maybe just fight to stay alive

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40
Q

During asphyxia the carotid bodies can get damaged, what effect can this have

A

They contribute to normal heart rhythm so irritating them may cause death via arrhythmia

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41
Q

During asphyxia the vagus nerve can get damaged, what effect can this have

A

It can cause arrhythmia as it innervates the heart

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42
Q

Typical signs of asphyxia are usually absent in environmental asphyxia - true or false

A

True
This is because death is often rapid - less struggle
More likely to just lose consciousness
Therefore the scene and circumstances are important in these cases

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43
Q

The term suffocation is often used to describe what

A

Often used as a general term for deprivation of O2, due to lack in environment or external obstruction of airways
More emotive term associated with struggle/homicide - best not to use if possible

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44
Q

What is homicidal soft smothering

A

Obstruction of the nose and mouth

Common in infants and elderly by a hand or a pillow - easier to overcome

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45
Q

List potential methods of suffocation

A

Soft smothering - hand or pillow
Plastic bag asphyxia
Overlaying of infants
Gagging

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46
Q

Why is CO poisoning less common these days

A

Gas used is now ‘cleaner’

CO monitors are now more common in homes

47
Q

Which injuries can be caused by smothering

A

May get some bruising or laceration on lips/gums - pressed against teeth by compression or due to work of breathing creating suction effect
Can be confused with CPR artefacts

48
Q

Which types of asphyxia are caused by plastic bag asphyxia

A

suffocation + environmental asphyxia
Bag means there is limited O2 supply and CO2 builds up- environmental
The bag can also form a seal over airway and suffocate

49
Q

Which types of asphyxia are caused by overlaying of infants

A

suffocation + crush asphyxia
The weight of the adult crushes their chest so it cannot expand for breathing
Also a suffocation element due to smothering with bedclothes/adults clothing/ falling between mattress etc.

50
Q

How does gagging cause asphyxia

A

secretions obstruct nasopharynx

makes it harder to breathe

51
Q

The general signs of asphyxia are often absent in suffocation cases - true or false

A

True
Typically less struggle
Less obstruction of the blood vessels as well - responsible for many signs
Therefore scene and circumstance are important
Presence of signs would be suspicious

52
Q

Which marking is better for determining ligature placement - lividity or congestion

A

Lividity - the line is much clearer than in congestion

53
Q

Plastic bag asphyxia is a common method of suicide - true or false

A

True

death is usually quick

54
Q

Why might someone try to keep the bag away from their face in cases of plastic bag asphyxia suicide

A

It is a more peaceful death if bag not on face
If the bag seals over the airway and causes occlusion it usually generates struggle/panic
However, if death is purely from lack of O2 there is less struggle - tend to fall into unconsciousness

55
Q

What signs may be seen internally in cases of asphyxia due to external compression of nose and mouth (smothering)

A

May see internal haemorrhages at points of compression - seen on dissection
Even if lacking external signs
e.g. under the neck from fingers or on the back of the head due to pressure

56
Q

What is traumatic or crush asphyxia

A

When there is pressure fixation of chest wall and abdomen
External forces prevent the chest moving sufficiently for proper oxygenation
Can’t draw O2 in or blow CO2 out

57
Q

What can cause traumatic or crush asphyxia

A 
Burial 
Trench collapse 
Crowds - e.g. Hillsborough
Under vehicle 
Overlying
58
Q

Which pathological signs are often seen in traumatic or crush asphyxia

A

Florid general signs both externally and internally - petechiae, congestion, cyanosis, oedema
Will occur at points above/below where pressure applied

Specific external & internal injuries often slight, most are quite general

59
Q

Which pattern of congestion and lividity may be seen in a death from traumatic or crush asphyxia

A

Usually shows the point of compression as pale (contact pallor) with congestion surrounding this (e.g. above/below)
Congestion around clavicle/neck caused by chest compression - blood from head cannot drain
May also get entrapment marks - distinct pattern of crushing object

60
Q

What is ‘Burking’

A

Burke & Hare’s method of asphyxia
Sitting on chest (traumatic/crush asphyxia)
Manual occlusion of nose and mouth (smothering)
Leaves little or no signs of trauma for receiving anatomist

61
Q

Can alcohol contribute to asphyxia

A

Yes
As well as other depressant/sedative drugs
It reduces the struggle
Common in positional - too drunk to move out of dangerous position

62
Q

What is positional asphyxia

A

When the body position itself obstructs the airway or impairs the act of breathing
e.g. Neck at right angle will compress the airways and obstruct

Associated with sedative intoxication - alcohol etc.
Some natural disease/disability can contribute too

63
Q

Positional asphyxia is usually accidental - true or false

A

True
e.g. frail person cannot get self out of position unaided
Or too drunk to move

64
Q

What is restraint asphyxia

A

When the chest, diaphragm & accessory muscles are impaired

65
Q

Restraint asphyxia is a variant of which other type of asphyxia

A

Positional

66
Q

What is restraint asphyxia associated with

A

Stimulant intoxication
Common in psychiatric & custody situations
Police restraint - controversial cases

67
Q

What must be established in cases of positional asphyxia

A

Why they were in that position and why they didn’t get out of it
Natural disease, frailty, intoxication etc.?

68
Q

Which groups are at higher risk of choking

A

Elderly, children, those with mental disabilities and underlying medical conditions (particularly with impaired swallow)

69
Q

Define choking

A

Obstruction of upper airway, between pharynx & tracheal bifurcation by food or foreign object
e.g. food bolus, toy, dentures etc.

70
Q

Which signs are seen in choking deaths

A

The general signs of asphyxia are variable in these cases

May see the obstructing object on dissection of neck/airways

71
Q

How does choking cause death

A

Death is often rapid via vagal inhibition

Airway obstruction

72
Q

Hanging is a common method of suicide - true or false

A

True

It is easily available and often lethal

73
Q

What aspects of hanging put pressure on the body

A

The ligature - fixed or running loop puts pressure on the neck

Body weight - full or partial suspension puts pressure on the neck

74
Q

How does hanging cause death

A

Obstruction of airway - pushes the tongue up into soft palate
Occlusion of the carotid arteries - decreases blood flow to brain
Irritation of carotid bodies - arrhythmia
Occlusion of jugular veins - causes cerebral oedema/hypoxia etc.
Vagal inhibition

75
Q

General signs of asphyxia are usually absent in suicidal hangings - true or false

A

True
There is little struggle - resigned to fate
No defensive wounds (would be seen in homicide)

76
Q

Describe the ligature mark seen if a narrow object is used for hanging

A

Will be a narrow and tight ligature mark

Often deeper as the pressure is more concentrated

77
Q

Describe the ligature mark seen if a wide object is used for hanging

A

Larger and more spread out ligature mark
Will be more superficial are pressure is spread over a greater area
May not have as enhanced physical features

78
Q

Describe the appearance of the ligature mark left in hangings

A

Will have a rising angle - under chin then at oblique angle upwards to the suspension point
Will have a spared patch at the point of suspension - less direct pressure here (usually back of neck)
May have pressure pallor directly under ligature with markings either side

79
Q

You must be completely suspended of the ground in order too hang yourself - true or false

A

False
Can be partial or full
Just need to be suspended enough to prevent you correcting your position - just need to be there long enough to pass out

80
Q

What is happening to rates of hanging

A

They are increasing

May be due to other methods being eradicated - e.g. car exhaust or head in oven (cleaner gas isn’t effective)

81
Q

Which locations are high risk for hangings

A

Psych wards and prisons

Must consider items that can be used such as bedsheets/shoelaces

82
Q

What can determine the choice of ligature in hanging

A

Availability and context are important

83
Q

List features of suicidal hanging

A

Ligature will still be in place - can’t remove it as dead!
Absence of defensive wounds
Use of drugs or alcohol
Suicide notes or messages
Multiple methods - e.g. Plastic bag over head and hanging

84
Q

Which ligature mark patterns suggest homicide

A

Horizontal ligature more in keeping with strangulation

Multiple marks can be suspicious - e.g. Throttled then hung

85
Q

When might a horizontal ligature be seen in genuine hangings (i.e. not homicidal strangulation)

A

Can be seen if the point of suspension is very unusual

86
Q

When can multiple ligature marks be seen in a non-suspicious case (i.e. suicide)

A

Can be due to ligature breaking and moving

or skin abrading through and slipping

87
Q

Hanging may be used to conceal homicide - true or false

A

True

May be strangled and then and strung up to try and cover the true cause of death

88
Q

Which fractures are common in hangings

A

Fracture to the great horn of thyroid cartilage
Will sit at an odd angle
Fracture to hyoid
May have haemorrhage around the fracture

89
Q

Which lividity pattern is seen in hangings

A

Glove and stocking lividity distribution if suspended - blood pools in hands and feet
May be different if the body was moved before fixed

90
Q

Which congestion pattern is seen in hangings

A

Will be congested above the ligature

91
Q

Cervical fractures are common in hanging deaths - true or false

A

False
This requires a large drop (as per judicial hangings of the past)
This is hard to achieve alone
Often severs nerves - quick death

92
Q

How long does death from hanging typically take

A

Loss of consciousness in 15-30 sec
Therefore cannot move themselves
Death in 1-2 mins

93
Q

What is sexual asphyxia

A

Asphyxia that occurs during a sexual act

Usually an accidental hanging

94
Q

What is the most common cause of sexual asphyxia

A

Failure of safety mechanisms
Sex devices usually have some for of safety feature to allow quick release - if these fail can lead to death
Item usually left in place (unless someone moves you)

95
Q

Which groups are associated with sexual asphyxia

A

Young males - often a regular, secret practice

Those into masochism, pornography and transvestism

96
Q

How can sexual asphyxia be differentiated from other causes

A

Scene is usually diagnostic - sex device present, clothing choice
Very different to most ligatures

97
Q

Ligature strangulation is most associated with which manner of death

A

Homicide
Ligature may be held, tied or twisted by an assailant/ third party

Suicide and accident are rare

98
Q

Which signs are commonly seen in ligature strangulation cases

A

Florid general signs - petechiae etc.
Horizontal mark of uniform depth (low level)
May be circumferential - more like a garrote
Skin bruises, scratch abrasions on hands/neck - trying to get ligature off
Deep neck muscle bruising
Hyoid & thyroid fractures

More signs as usually more struggle

99
Q

What is manual strangulation

A

When the hands are used to strangle someone else

Also called throttling

100
Q

Which signs may be seen in cases of manual strangulations

A 
Finger pad bruises on neck 
Scratch or crescent abrasions from attacker's nails or victim's own (trying to get hands off) - may find DNA under nails
Florid general signs - due to struggle 
Lack of ligature mark
Deep neck muscle bruising
Hyoid & thyroid fractures

Lots of struggle = lots of signs

101
Q

What signs may be seen on the attacker following a manual strangulation

A

Scratch or crescent abrasions on their hands/arms from the victim’s nails (as they tried to get the hands off their neck)

As a result their DNA may be found under the victims nails

102
Q

How long does the grip need to last in a manual strangulation case

A

Typically more than 30 secs

103
Q

Describe the grip pattern seen in cases of manual strangulation

A

Shifting grips often lead to varying patterns

Sleeper holds

104
Q

How can you tell that the thyroid cartilage has been fractured

A

If the horns are at a weird angle

Compare sides?

105
Q

What is inhalational asphyxia

A

When there is obstruction of lower airway (below trachea) due to the inhalation of something

106
Q

List common causes of inhalational asphyxia

A

Foreign bodies - toys, nuts, other food
Vomitus
Water - drowning

107
Q

Which groups are at risk of inhalational asphyxia

A 
Children 
The elderly 
Those with dementia 
Those with swallowing issues - muscular/neuro issues
Alcoholics - at risk of inhaling vomit
108
Q

Why is it hard to determine if vomit caused inhalational asphyxia was

A

Often agonal vomiting (e.g. occurred during death, not the cause) - common in drugs deaths
Or can be a PM artefact

109
Q

List the structures of the respiratory system

A 
Nasal passage 
Oral cavity 
Join to form pharynx 
Then larynx 
trachea 
Bronchi 
Bronchioles
Alveoli - site of gas transfer 
Diaphragm
110
Q

How does air enter the lungs

A

Movement of diaphragm causes pressure changes in the chest which draws air in through the mouth or nose (or trach if one in place)

111
Q

Describe the structures in the oral cavity

A

Hard palate on roof of mouth - bone
Transitions to soft palate - may be responsible for snoring
Tongue is one large muscular structure

112
Q

List the bony and cartilaginous structures of the neck

A

Hyoid bone
Thyroid cartilage - has superior and inferior horns
Cricoid cartilage

113
Q

In which places can the airway be obstructed

A

External passages - mouth and nose

Internal passages - pharynx, larynx, trachea, bronchi
- pharynx/larynx obstructed if trach covered

114
Q

How can the tongue appear in hanging victims

A

Often affected by congestion and oedema

Protrusion of the tongue common

Forensic Medicine (13 decks)

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