Module 6: Forensic: Asphyxia to end Flashcards
What is asphyxia?
Interference with the uptake or utilization of oxygen
On type of asphyxia is hanging or strangulation which involves compression of the neck, what happens when the airway is occluded?
Arrest of arterial supply to brain and obstruction of venous return from brain
- -generalized cerebral edema (vasogenic edema) due to inflammatory disruption of the BBB with increased vascular permeability
- -cardiac arrhythmia via stimulation of carotid baroreceptors (carotid sinus reflex)
During hanging or strangulation the patient will get petechiae why?
From post cap venules from acute rise in venous pressure
In strangulation there is direct pressure on the neck manually or with ligature, who is the most common victim?
Female and usually sexual motive
The next type of asphyxia is obstruction of airway due to smothering/choking or postural asphyxia, what is postural asphyxia?
Kinking or compression of airway by position of victim and inability to change position
What are the last two types of asphyxia?
Compression of chest: traumatic or mechanical asphyxia
Exclusion of oxygen: local depletion of oxygen
What is the mechanism of hydrogen sulfide?
inhibits cytochrome and reduction of oxyhemoglobin — methemoglobin
detergent suicides: H2S generated by mixing household chemical – hazardous to first responders
What percentage of O2 intake is lethal?
less than 8%
8-10% = LOC
H2S in inspired air, what are the effects?
Low = rotten egg odor and irritation 150ppm = paralysis of olfactory nerves 1000-2000ppm = rapid death
There are asphyxial games, what is the motivation for these/
Euphoria through hypoxia
What are the various methods for asphyxial games?
Manual strangulation
Ligatures
Chest compression
What is the age group for asphyxial games?
Older children and adolescents (7-21 yr old)
–alone or in groups
What are features of asphyxial games?
Headaches, unexplained bruising around neck, blood shot eyes, facial petechiae, disorientation after being alone, ligatures tied in strange knots or unusual places, wear marks on furniture
Move on to electrics, what is electricity, voltage, resistance, and current?
Electricity: produced by stream of electrons flowing through a conductor
- -voltage: electrical pressure that causes current to flow
- –resistance- resistance to flow
- -current= rate of flow
What is the requirements for electrocution?
Charged source, current path through vital organs and ground
What is the mechanism of death in direct electrical effects, thermal burns, and blunt force injuries?
Direct electrical effects: Vfib, asphyxia (paralysis of resp muscles) and direct disruption of brainstem
Thermal burn: heat, ignition of clothing
Blunt force injuries: falls and blast effect
What is the gross appearance of low voltage electrical burns?
May not be present
- -typical crater with central charring, abrasion like, second or third degree thermal burn
- -shape of conductor may be branded into skin
What is high voltage electrocution?
3rd degree electrical burns 2nd degree contact burns Arcing "splash" electrical burns: bright fast traveling sparks with rhythmic cracking sound Skeletal fractures Asphyxia Vascular thromboses Myocardical injury
Compare high and low voltage
Low voltage: less than 600 to 1000 volts, small burns in 50%, less CNS injury, lag time and Vfib
High Voltage: greater than 600 to 1000 volts, extensive burns, more CNS injury, immediate effect, asystole/asphyxia
What is lightening?
Negative charge build up in clouds vs positive charge of earth
- -10,000 to 100,000 amps DC
- -high voltage of short duration
- -high heat
What types of burns do you get with lightening?
Serious burns infrequent b/c of short duration
Contact burns from metal objects
Ignition of clothing
What is the shockwave/blast effect?
Shredded clothing
Tympanic membrane rupture
Secondary trauma
What are Lichtenberg’s figures?
Fern-like aborescent, dendritiform, evergreen tree, keraunographic markings
- -5:30 cm long along BV
- –local hemolysis due to heat generated by current flowing through cutaneous blood vessels
- -may be transient
- -also in high voltage electrocution
