Comprehensive Study Notes on Explosives, Burns, and Fire-Related Injuries

Explosions

  • Definition of Explosives

    • Energetic materials that can react chemically to produce:
    • Heat
    • Light
    • Gas

  • Nature of Explosives

    • Low Explosives (e.g., gunpowder)
    • Deflagration: Rapid combustion/burning
    • Velocity: less than 3300 FPS
    • High Explosives
    • Detonation: Explosive reaction greater than the speed of sound
    • Velocity: more than 3300 FPS, can reach speeds of up to 32,000 FPS

Blast Wave Properties

  • Positive Phase

    • Short duration
    • High pressure peaks
    • Propagates outward from the seat of blast

  • Negative Phase

    • Long duration
    • Low pressure
    • Acts inward towards the seat of blast

Explosion Injuries

  • Types of Injuries
    • Primary Injuries: Caused by the blast wave itself
    • Secondary Injuries: Resulting from missiles propelled by the blast force
    • Tertiary Injuries: Resulting from impact with another object

Blast Wave Injuries

  • Injuries may not present visible external trauma
    • Examples of injuries without visible signs include:
    • Ruptured ear drum
    • “Blast lung” symptoms can occur up to 48 hours post-explosion
    • Abdominal hemorrhage
    • Concussion

Fire Related Deaths

  • End results signify a dynamic process involving heat
    • Heat distorts and destroys soft tissue and bone
    • Severity of burns depends on:
    • Intensity of heat
    • Duration of exposure
    • Difficult to determine the mode of death based on these factors

Skin Anatomy

  • Layers of Skin:
    • Epidermis: The highest layer
    • Dermis: The middle layer
    • Fatty Tissue: Contains sweat glands, oil glands, and hair follicles

Burn Classification

  • 1st Degree Burns

    • Characteristics:
    • Superficial
    • Red discoloration
    • Increased local skin temperature due to congestion
    • No blisters, possible peeling
    • Example: Mild sunburn

  • 2nd Degree Burns

    • Characteristics:
    • Blisters present
    • Upper layers of skin are destroyed
    • Scarring possible

  • 3rd Degree Burns

    • Characteristics:
    • Entire thickness of skin is involved (both epidermis and dermis damaged)
    • Pain may be absent due to nerve endings destruction
    • Scarring will result
    • Skin grafting typically necessary

  • 4th Degree Burns

    • Characteristics:
    • Complete destruction of skin and underlying tissue, including bone
    • Often characterized by charring

Rule of Nines

  • Body Surface Area Percentage:
    • Front/Back of Head: 4.5%
    • Front/Back of Arms: 4-5%
    • Front/Back of Torso: 18%
    • Groin: 1%
    • Each Leg: 9%

Scalding

  • Most common thermal injury in children
    • Severity dependent on:
    • Temperature of water
    • Length of contact time with the skin
    • Pattern injuries may indicate possible abuse
    • Household water heaters can be set up to 150°F, causing severe burns within 2-5 seconds of exposure

Fire Temperatures

  • Typical Fire Temperatures:
    • House fires generally range from 900°F to 1300°F
    • Cremation: Requires 1.5 to 2 hours at approximately 1800°F to reduce an average adult to ash

Fuel Load Factors

  • Clothing and body fat contribute to fuel load:
    • Body fat can act as a wick for low, smoldering fires
    • Rapid burning can cause charring of the body within 20 minutes
    • Damage consistency to the body should correspond with perceived fuel load
    • Accelerants (e.g., gasoline, kerosene) can cause patchy charring; watch for extensive damage to one area compared to adjacent areas
    • Tissue shrinkage and pulling apart may expose adipose and muscle tissues, contributing to the complexity of injuries during fires

Pugilistic Pose

  • Characteristics:
    • Muscle and tendon shrinkage leading to an altered position known as "Boxer's Pose"
    • Flexor vs. extensor muscle dynamics
    • May result in fractures

Skull Fractures

  • Fractures typically occur:
    • Not along suture lines
    • May be caused by falling debris or structural collapse
    • Can also be a result of pressurized water

Brain and Abdominal Injuries

  • Brain: May be shrunken due to cooking/dehydration
  • Blood under dura mater suggests injury sustained while alive
  • Splitting of Abdominal Wall:
    • Shrinkage of skin combined with abdominal pressure
    • Orientation of splits may correlate with muscle fiber alignment

Determining Cause of Death

  • First, assess if the deceased was alive at the time of the fire:
    • Fire-Related Deaths: About 75% involve inhalation injuries
    • Key indicators include:
      • Soot and carbon present in nose and mouth
      • Carbon monoxide (CO) interacts with hemoglobin to create carboxyhemoglobin (COHb)
      • CO preferentially binds to hemoglobin than oxygen
      • Higher levels of COHb result in lower oxygen availability to brain and muscles

Physiological Effects of Carbon Monoxide

  • Symptoms include:
    • Headache
    • Weakness
    • Dizziness
    • Confusion
    • Nausea and vomiting
    • Collapse
    • Death
    • Presence of cherry red lividity indicates CO saturation

Carbon Monoxide Levels

  • Carbon Monoxide Concentrations:

    • 50-60% saturation in healthy adults can be fatal
    • 8-10% saturation is normal for chain smokers
    • Expect lower saturation levels in the elderly
    • Infants and children accumulate fatal levels more rapidly due to higher metabolic rates
    • Rate of CO saturation is directly related to cardiac output

  • Note on Interpretation:

    • Presence of carbon monoxide in the blood supports that the decedent was alive during the fire, while absence does not imply death prior to the fire

Fire Events and Injuries

  • Flash Fire:

    • Inhalation of superheated gases can lead to airway edema and swift suffocation

  • Steam Exposure:

    • Inhalation of moisture-saturated air results in greater harm compared to dry air at the same temperature
    • Serious injuries from just 1-2 breaths of moist air at 130°F
    • Dry air inhalation is survivable up to 300°F for brief periods

Synthetic Materials in Fire

  • Increasingly common in fire incidents, synthetic materials burn hotter and release toxic gases
    • Burning Polymers: Produce hydrogen cyanide, which disrupts cellular oxygen utilization
    • The effects of carbon monoxide and cyanide can be additive

Identification of Decedents

  • Factors Affecting Identification:

    • Height may decrease by several inches
    • Weight loss can exceed 60% in severe cases
    • Skin shrinkage may distort facial features

  • Hair Change due to Heat:

    • Gray hair may turn blond at 250°F; brown hair may develop a reddish tint at 400°F

  • Methods of Identification:

    • Full body X-rays
    • Dental comparisons
    • Medical appliances (e.g., artificial joints, screws, plates)
    • Fingerprints
    • DNA analysis
    • Circumstantial evidence

  • Critical Questions:

    • Who is the decedent?
    • Why were they at that location?
    • Where were they found in relation to the fire's origin?
    • What was their position when found?