T2S3: Asphyxia & Deaths due to Neck Pressure

Question 1

Classify asphyxia.

Answer 1

1. Suffocation
2. Smothering
3. Choking
4. Resp Restriction
5. Throttling
6. Ligature strangulation
7. Hanging
8. Drowning
9. CO poisoning
10. Aspiration of stomach contents

Question 2

What are the classical signs of asphyxia?

Answer 2

1. Petechial/Tardieu hemorrhages
2. Congestion & edema
3. Cynosis

Question 3

1. What is suffocation?
2. Where is it found?
3. What is mechanism of death?
4. What classical asphyxial signs are present?

Answer 3

1. A decrease in oxygen tension in inhaled air or mechanical obstruction to entry of air.
2. It is found in decompression with a drop in barometric pressure or with consumption and/or displacement of oxygen by inert gasses.
3. Hypoxia plays a role, but inert gasses may also cause death due to vaso-vagal inhibition.
4. Asphyxial signs are infrequently found, except for congestion.

Question 4

1. What is smothering?
2. When should it be excluded?
3. What can be found post-mortem?

Answer 4

1. Obstruction of the external airways. This can be achieved using an impervious material, mobile solid or the passive weight of the head.
2. In cases of SIDS
3. Local injuries to the face, nose and mouth. Hypostasis and post-mortem color changes should not be over interpreted.

Question 5

1. What is choking?
2. What are the post-mortem findings?
3. Name 2 ways food ends up in the airways during swallowing.

Answer 5

1. Obstruction of the internal airways between the pharynx and the bifurcation of the trachea e.g. foreign body or acute obstructive lesion.
2. Foreign body, with possible edema or inflammation with acute obstructive lesions. Typical signs may be absent.
3. a) Choking in children, elderly and mentally retarded with weak swallow mechanisms. b) Bolus death (Cafe coronary syndrome) - Mimics heart attack with sudden death due to cardiac arrest from vaso-vagal inhibition.

Question 6

1. When can aspiration of stomach contents be diagnosed as a cause of death?
2. How else may stomach contents enter the airway?

Answer 6

1. If the deceased had a decreased level of consciousness. The food must be in the smaller bronchi, or there must be a vital reaction to aspiration at post-mortem or aspiration must have been witnessed by others.
2. It can enter passively when the body is moved after death.

Question 7

1. What are the mechanisms of asphyxia in restriction of respiratory movement?
2. What are the post-mortem findings?

Answer 7

1. Traumatic asphyxia, positional asphyxia and paralysis of resp muscles.
2. Prominent asphyxial signs in face to base of neck, hemorrhage from mouth and ears, congestion and petechiae of lungs, skin wounds from mechanical fixation.

Question 8

1. Describe the victims of throttling and their injuries?
2. What type of testing should be done?
3. Which asphyxial signs are present?
4. How are the internal neck structures affected?

Answer 8

1. They are weaker than the assailant and usually have many injuries due to changing of hand position. Bruises are often discoid, red/purple, asymmetrical and mostly on the sides of the neck. Abrasions are caused by either party.
2. DNA typing of the nails of both parties.
3. They may not be be present esp if cause of death is vaso-vagal inhibition. If present, they could be accentuated due to pressure in veins cycling.
4. Hemorrhage and bruising may be seen with possible fractures.

Question 9

1. How would the skin in the neck look in ligature strangulation?
2. Which asphyxial signs are present?
3. How are the internal neck structures affected?

Answer 9

1. Usually the ligature would be low in the neck, and encircling it. It may appear to be deep due to edema in the surrounding tissue. The friction abrasion is often yellow-brown. Soft material may not cause any skin damage. Scratch marks may be present.
2. Signs are prominent. The face above the ligature is usually very congested, cyanotic and puffy.
3. They are usually less affected that throttling.

Question 10

1. Describe how homicidal hanging can occur?
2. How would the skin in the neck look?
3. What post-mortem signs are found?

Answer 10

1. Victim is much smaller than the assailant, or is incapacitated by drugs. There could be signs of resistance such as bruises or bound arms and legs.
2. Localized friction abrasion, not completely encircling the neck. It will have an apex at the point of suspension which would not be under the chin. The knot could leave a mark. The ligature is usually oblique and high in the neck.
3. Hypostasis in the arms and legs.

Question 11

1. What is sexual asphyxia and auto-erotic deaths?
2. What is the mechanism of death?
3. How can you exclude suicide/homicide?

Answer 11

1. It is to induce hypoxia for production of erotic hallucinations using a ligature or drugs.
2. Death occurs by when ligature fails to release or by accidental drug overdose.
3. Confirm that the deceased could have secured bonds himself and that there is no suicide note.

Question 12

What are the 5 mechanisms of death with pressure on the neck?

Answer 12

1. Airway occlusion - direct or larynx into pharynx.
2. Vein occlusion - produces the classical signs.
3. Arterial occlusion - brain damage
4. Nerve effects - baroreceptors and glossopharyngeal
5. Combination

Question 13

1. What are the causes of death in a body retrieved from water?
2. What are the 4 signs of immersion?
3. How can we estimate the time a body spent in water?

Answer 13

1. Death from natural causes before or while in water (CVA), from injury before (disposal) or while in water, from immersion and from drowning.
2. Maceration of the skin (Washerwoman), cutis anserina, hypostasis of the limbs (or selective loss of rigor mortis) and mud on/in the body.
3. Skin wrinkling in hours to 3 days, early decomposition in 4-10 days and loss of skin and muscle in 1-2 months.

Question 14

1. What kind of post-mortem injuries can occur after drowning?
2. What is the mechanism of death in immersion?
3. What is the mechanism of death in drowning?

Answer 14

1. Flung against rocks, scraping in juries of limb, predation injuries and slicing injuries of propellers.
2. Reflex cardiac arrest (Dx of exclusion)
3. Hypoxia as well as fluid and electrolyte disturbance. Fresh water - hemodilution with relative anemia and hemolysis. Salt water - water withdrawn from plasma into lungs.

Question 15

1. What are the post-mortem findings in drowning?
2. What special investigations can be done?
3. What are the mechanisms of death in drowning with resp apparatus?

Answer 15

1. Froth in the airways (protein and surfactant), lung changes (edema, dry lung, emphysema aquosum and hemorrhages), stomach containing foreign material, cataleptic stiffening and post-mortem trauma.
2. Diatoms - microscopic algae with a silicaceous exoskeleton.
3. Hypoxia, nitrogen or CO2 poisoning and pulmonary barotrauma.

Question 16

1. Name 5 sources of CO.
2. What is the mechanism of CO poisoning?
3. What are the post-mortem findings?
4. Describe blood analysis in CO poisoning.

Answer 16

1. Exhaust fumes, structural fires, industrial processes, domestic appliances and incomplete combustion of a gas flame.
2. CO binds to Hb much stronger than O2. The remaining O2 binds much stronger and is not easily released to tissues. CO also depresses resp centre and is cytotoxic.
3. Hx is important. Cherry red color of tissues and blood (COHb>30%) in areas of postural hypostasis. Necrosis and cavitation of the basal ganglia, damage to the substantia nigra and focal myocardial necrosis can occur.
4. Measure percentage of Hb. Fatal levels in healthy individual 50-60% and elderly 30%. Normally 5% or at risk 10%. Other diseases, toxic states and high alcohol blood levels have an additive effect.