Pathology lecture 8

Asphyxia and Environmental Trauma

1) Asphyxia
- Broadly defined as a failure of cells to receive or utilize oxygen. Loosely grouped into
three categories
o Suffocation
 Failure of oxygen to reach the blood
 Entrapment/environment suffocation
 Individuals find themselves trapped in an airtight or relatively air
tight space
 Initially sufficient oxygen to breathe, but the supply is limited and
oxygen is rapidly depleted
 Usually accidental, but suicide and homicide must also be
considered
 Individual inadvertently enters an area deficient in oxygen
o Normal % of oxygen in atmosphere?
o What should you do at the scene?
 Be extremely careful
o What are potential autopsy findings?
 Most of the time, nothing because it all has to do
with cellular respiration
 Potential terminal collapse injuries
 Smothering
 Obstruction/occlusion of the external airways (nose and mouth)
 Usually homicide or suicide, rarely accidental
 What autopsy findings might you expect?
o Occasional bruising, however may not see anything at all
 What information is essential to have?
o How vulnerable is the person? Are they immobilized? Are
they frail, elderly? State of the person who is found, history
of abuse, are they really ill?
 Choking
 Obstruction WITHIN the air passages (trachea, bronchi)
 Most are accidental
 What questions need answering?
o Intoxication
o Swallowing difficulties
o Infection
 Epiglottitis
o Allergies
o Mental health issues
 Mechanical asphyxia
 Pressure on the chest
 o Restraint asphyxia
 Obstruction of breathing as a result of being
restrained
 Important consideration in deaths in custody, or in
hospital when a person is being restrained for
medical or safety reasons
 Similar to positional, where a person cannot get out
a position that interferes with breathing
 Other people are involved
o Positional
 Individual becomes trapped in a position where they
cannot move out of that position on their own, or
the restricted space
 Almost always accidental
 Always consider WHY someone cannot move
themselves
 Age
 Mobility issues
 intoxication
o Crush
 Occurs when a heavy weight presses down on the
chest or abdomen, restricting the ability to breathe
 What autopsy findings might you expect?
o Petechiae
o Congestion
o Evidence of trauma
 Pressure on the neck
o Aorta, jugular veins, hyoid bone, thyroid, larynx
o Manual strangulation
o Ligature strangulation
o Choke holds
o Hanging
o Autoerotic asphyxia
 Petechial hemorrhages
o Small, pinpoint hemorrhages
o Occur as a result of increased intravascular pressure with
obstructed venous return
o Non-specific
 Sneezing
 Compression of the chest
 Childbirth/straining
 Resuscitation
 Hanging
 Strangulation
 Hanging
 o Compression or constriction of the neck stucutures by a
noose or other constricting band tightened by the weight of
the body
o Usually suicide
o Complete suspension – usually no petechiae
o Incomplete suspension – petechiae may be seen
o Ligature furrow rises to point of suspension
o Important to differentiate from HOMICIDAL HANGING
and POSTMORTEM SUSPENSION
o Usually causes death by obstructing blood flow to or from
the brain
o Exceptions in some cases of very tight ligature, and
judicial-type hanging (with neck fracture)
 Autoerotic asphyxiation
 Suffocating gases

o Strangulation
Autopsy findings may be subtle
1) Petechiae
2) Abrasions/bruises on the skin of the front of the neck
a. Fingernail marks, discoid bruises
3) Bleeding into the neck muscles
a. Strap muscle hemorrhages
4) Fractures of the laryngeal cartilage and/or hyoid bone
5) Bleeding into the thyroid gland or injury to the carotid arteries
 Manual
 Pressure of a hand, forearm or other limb against the neck
 Occlusion of the blood vessels supplying blood to the brain
 Face is congested, petechial hemorrhages
 What marks might you find on the neck?
o Fingerprints, nail marks,
 Ligature
 Pressure on the neck is applied by a CONSTRICTING BAND that
is tightened by a force other than body weight
 Congestion, petechial hemorrhages, marks on the neck
 Pressure applied to the neck using a ligature/tie
 Horizontal ligature mark (not furrow)
 Internal injuries more akin to manual strangulation than hanging
(usually)
 Neck dissection
 Very careful and systematic when dissecting
 Pull back the skin to reveal all mussels. Check for bleeding into the
muscle tissues
 Dissect muscle by muscle going into the facia very carefully
 Dissection and removal of trachea – darkness indicates
hemorrhages and fractures
o Chemical asphyxia
 Inhaled gaseous chemicals prevents utilization of oxygen at the cellular
level
 Carbon monoxide
 Most common
 Colourless, odourless, tasteless, non-irritating
 Competes with oxygen binding sites on oxygen-carrying protein in
the blood (much greater affinity 30-500 times stronger than
oxygen)
 Measured as a percentage of carboxyhemoglobin in the blood
(>20% is toxic)
 Blood is really pink, hemoglobin hasn’t changed. Pink lividity
typically means carbon monoxide poisoning.
 Hydrogen sulfide
 Incredibly dangerous to everyone else around
 Autopsies aren’t performed because of how dangerous it is
 Green colour of face, brain

Bodies from water

- Drowning – death caused by submersion in a liquid
o Mechanism is irreversible cerebral anoxia
o Time to irreversible cerebral anoxia depends on the age of the individual and the
temperature of the water
o Consciousness is usually lost within 3 minutes of submersion
- Breath holding
- Involuntary gasping
- Foam cone from pulmonary edema
- Wrinkled hands

Approach to drowning
1) Alive or dead when they entered the water?
a. Human factors
i. Poor swimmer
ii. Natural disease (cardiac disease, seizure)
iii. Incapacitating injury
iv. Drugs/alcohol
b. Environmental factors
i. Water temperatures
ii. Rough water/undertow
- Hyper inflation of the lungs
o Front of the lungs will touch and possibly able to see impression of the ribs on the
lungs
- Foam cone
- Wrinkled hands
Findings at autopsy
- There are no pathognomonic findings for drowning
o Recovered from water
o Wet clothes/body
o Foam cone
o Immersion changes
o Hyperinflation of the lungs
o Must rule out other causes of death

Bodies from fire

- Majority are accidental, rarely suicide or homicide
- A lot of people are needed to investigate these deaths depending on the extremities
- Burns are classified according to the depth of the injury
o First degree: limited to the superficial epidermis (mild sunburn)
o Second degree: partial thickness, involving the epidermis and dermis (blistering
sunburn)
o Third-degree: full thickness, involving the skin and appendages (sweat glands,
sebaceous glands)
o Fourth degree: charring, complete destruction of the skin and tissue, exposing
bone
- Flame burns: direct contact with a flame
- Contact burns: direct contact with a hot surface
- Radiant burns: exposure to heat waves
- Scalding burns: exposure to hot liquid
- Microwave burns: unusual
- Chemical burns: acids and alkalis

Death from fire/thermal injury

Immediate
- Within minutes to hours of the injury
- Neurogenic shock (pain)
- Direct thermal injury
- Inhalation of toxic gases (usually carbon monoxide)
- Inhalation of hot gases

Delayed
- Days to years
- Fluid loss/shock
- Respiratory failure
- Infection
- Pulmonary embolism (immobility)
- Death by suicide (due to pain, healed improperly)

The Scene
 - Residential
- Industrial
- Motor vehicle
- Review of the scene is essential to understanding how someone died
- Forensic anthropologist: vital to scene interpretation, extrication of the body,
identification and documentation of injuries

Approach to bodies from fire

- Identification: fingerprints, dental record comparison, medical implants, DNA
- Alive or dead at the time of fire? : antemortem trauma (accident, suicide, homicide), dead
s result of the fire?
- Documentation of injuries
- Cause/manner of death
- Contributing factors: intoxication, coronary artery disease, lung disease

Alive or dead?
- Soot (trachea, airways, esophagus, stomach)
o Confirms deceased was alive at the time of the fire
- Cherry-red lividity
- Thermal injury to the structures in the upper airways
- Carboxyhemoglobin saturation: measured as a percentage (carbon monoxide toxicity)
- Other competing causes of death (trauma, natural disease)
- Pugilistic attitude
o Skin splitting
o Charring
o Boxers stance

Fire and post-mortem artefacts

- Important to distinguish ante-mortem injury from post-mortem artefacts
o Pugilistic attitude
o Skin splitting
o Heat epidural hematoma
o Heat fractures

Fire and post-mortem imaging

Homicidal injury with post-mortem burning

Other environmental injuries

o Hypothermia
 Hide and die (burrowing)
 Paradoxical undressing
 Stress ulcers in the stomach
o Frostbite
o Heat illness
o Heat stroke
o Electrocution
 Rare COD
 May have no physical evidence of electrocution
 Joule burn
o Lightning strike
 Interesting pattern on peoples skin when they get too close to a lightening
strike.