Medicine - asphyxia

Question 1

Definition of asphyxia

Answer 1

• Lack of oxygen (absence of pulsation)

Question 2

Medicolegal issues with asphyxia

Answer 2

• Proving cause of death
• Was life endangered?
• Time needed
  o Longer time needed have more intention to kill
• Amount of force needed
  o Larger amount of force, larger intention to kill

Question 3

Signs of asphyxia

Answer 3

• Classical Signs
  o Facial congestion and oedema
  o Petechial Haemorrhages
  o Signs of raised intravascular pressure
• CLINICAL STAGES
  o Increased effort to Breath
  o Laboured respiration
  o Loss of consciousness, convulsions incontinence, vomiting
  o Death

Question 4

Asphyxia - suffocation

Answer 4

• Decreased O2 content in air
  o Agriculture; industry e.g. unknown escape of nitrogen in air
   Nitrogen absorbed into blood and causes you to lose consciousness with no signs at all
  o Death often rapid
  o Few signs – usually no signs at all
• Obstruction to external respiratory orifices (Smothering)
  o Smothering
   Most common is suicide attempt with plastic bag over head
   Old people
   Death often rapid
   Few signs
  o Plastic bags
   Usually rapid
   No signs
   Some signs may be: Lips pushed onto back on teeth and causes bruising on lips
• Usually goes no where legally as so difficult to prove

Question 5

Asphyxia - choking

Answer 5

• Internal obstruction of upper air passages
  o Death may be rapid or can get classical signs
  o Object
   Dentures; toys; blood; food; vomit; gagging
  o Usually no positive signs on post-mortem other than obstruction in airway
  o Those with Parkinson disease often develop problems swallowing so more susceptible to choke
  o Aspiration of food
   Food in larynx – choking symptoms or could be sudden silent death
   Could just keel straight over if airway is fully blocked
  o Aspiration of vomit
   Alcohol, anaesthetic, illness
   Autopsy finding
• Inconsistent
• Regurgitation – agonal, post-mortem (after death the contents of stomach often regurgitate back up into mouth and then into airway)
• Pressure on the neck
  o Manual Strangulation
   Could be fingernail marks/finger marks on neck if strangled by hand
   Bruises from fingertips
   Could leave no marks if it is a headlock used by arms – would only be bruising inside airway
  o Ligature strangulation
   Typical horizontal mark on neck by ligature around neck
  o Hanging
   Marks on neck in almost all cases
   Nearly always a rise up to point of suspension – usually mark is on back of head as the body is raised up
   Usually found touching the ground – weight of the body is enough to produce enough pressure on the neck rather than jumping off something high with ligature around neck – hanging does not always break the neck
• Structures Affected by Pressure on the Neck
  o Larynx (trachea)
   Fatal if closed
  o Jugular Veins
   Reduced venous return
   No kore new blood can get in and no knew oxygen body
   Do not need to squeeze as hard to block vein
  o Carotid Arteries
   Reduced blood supply
   No oxygen able to get to head and body
   Have to squeeze hard to block arteries
  o Baroreceptors in carotid bodies
   Sudden death
   Sensitive to pressure as they respond to blood pressure by decreasing and increasing heartrate however also respond to direct pressure – if squeezed will decrease heart rate
  o Can occur quickly put do need to squeeze relatively hard for a substantial amount of time

Question 6

Traumatic asphyxia

Answer 6

• External pressure on thorax
• Stadium disasters
  o People in large numbers in small space – crush each other
• Overturned vehicles
  o Npo seatbelt and car goes over – crushed between car and ground
• Industrial accidents
• Postural asphyxia
  o Alcohol – may end up upside down without getting back up – lungs crushed by other organs
• External signs
  o Injuries from compressing agent
  o Congestion; cyanosis; petechiae

Question 7

Drowning

Answer 7

• 150,000 deaths/year worldwide
• Accident – males, children, alcohol
• Suicide – elderly
  o Fluid getting onto airway blocking airways, replacing air which prevents breathing
  o Water may be absorbed into bloodstream (osmosis) from lungs – blood becomes dilute and causes cardiac arrest
• Survival
  o Salt water – 80%
  o Fresh water – 50%
  o Depends on initial resuscitation
  o Morbidity (damage to organs)
   Chronic brain damage
• Signs of drowning
  o Froth in the airways
   Limitation: Transient – does not last for very long and is destroyed by resuscitation. Those with heart failure can get froth
  o Waterlogging of lungs
   Limitation: ‘dry’ drowning - Water may enter lungs after death – does not show cause of death. Those with heart failure may have fluid in lungs anyway
  o Overinflation of lungs
   Limitation: Other causes e.g. asthma
  o General
   Decomposition – body often not found for a while and so decomposition destroys these positive signs of drowning
   Resuscitation
• Cause of death
  o Natural disease
   Before immersion – may die naturally and then fall in water for example
   During immersion
  o Injury
   Before immersion - homicide
   During immersion – body may get bashed against things when body is put into water – lots of grazes on body
  o Immersion