Bodies From Fire Flashcards
Key features of fire dynamics
Started with spark Needs to burn - oxygen - heat - fuel
Phases of fire dynamics
Incipient - fuel supply heated and ready to burn Emergent smouldering - inefficient combustion -> smoke Growth of flames - efficient burning - intensity doubles for each 10°C rise in temperature - flashover ignition temperature of nearby combustible material is reached
Bodies from fire manner of death
Natural - cause - inability to escape Accident - most common - alcohol, drugs, cigarettes - clothing - electrical Suicide - rare in west - accelerant on clothes, car Homicide - rare as method except arson - concealment of homicide - often fails
Key investigation points for investigation of fire related deaths
Was the victim alive at start of the fire
What was the cause of death
- fire - CO, smoke, burns, heat shock
- other - natural, alcohol, drugs, homicide
Why was the victim in the fire
Why was the victim unable to escape
Features of identify a body
Circumstances Personal effects Fingerprints DNA Dental X-rays Operations - presence/absence of ovaries, womb and appendix
Investigation of fire related deaths
Medical hx Circumstances Fire investigators examination of the scene - origin, development, nature of f Autopsy Toxicology and laboratory investigations
Fire artefacts
Occur in any body from fire irrespective of cause of death Pugilistic posture - arms flexed at elbow and fist clenched - boxer position - flexion of hips and knees - flexors more powerful when all muscles shortened Post mortem burning - thin reddened margin - leathery brown from smouldering heat - charred by high temp or direct flame Hair singed and turns reddish-brown Skin becomes blistered or may shrink, tighten and split Heat fractures Heat haematoma - extradural - crumbly layer of altered blood Falling masonry Recovery of body - easily damaged during moving
Features of severe PM burning
Skin splits Skin loss Muscle loss Amputation of limbs Exposure of body cavities - chest - abdomen - cranial cavity
Features if deceased was alive at the start of the fire
Signs that victim was breathing - not necessarily conscious
- soot in airways below the level of the vocal folds
- thermal injury to larynx
- blood CO > 10%n
Absence of signs does not necessarily indicate already dead
Mechanisms in death in fire related deaths
Smoke inhalation - thermal injury to URT - CO - particulates - smoke poisoning - toxic gas Burns - depth - extent - ante mortem vs post mortem - burning continues post mortem - singing, carbonisation, charring
Features of thermal injury in smoke inhalation
- common
- URT very efficient heat exchange - LRT protected
- dry air > 150°C or moist air causes laryngeal injury
- breathing hot air may cause reflex vagal inhibition
- laryngeal spasm
- laryngeal oedema
- tracheobronchial necrosis seen microscopically
Features of carbon monoxide poisoning
Colourless and odourless
From incomplete combustion of fuel
Binds to Hb with 200x more affinity than 02
- diminishes o2 carrying capacity and dissociation
- toxicity depends on
- rate of inhalation - concentration of CO and duration of exposure
- physical activity
- individual susceptibility - heart, lung disease
- blood levels expressed as a % of Hb
Clinical effects are dose related
- 50% = fatal - varies by health and fire factors
- 30-40% = impaired judgement, failure to escape, LOC
- 20-30% = dizziness, SOB, headache, nausea, fatigue
- 10%+ indicates victim alive during fire
- level below 10 does not mean already dead
- little or no CO produced due to abundant O2 leading to CO2 production
- rapid death due to cardiac arrest
Signs of CO poisoning
Pink discolouration of conjunctiva
Bright cherry pink prominent lividity
Features of direct particulate injury
Superheated soot and other particulate debris passes deeper into URT than other gases Depth of penetration depends on size - >10um = to nares - 5-7um = to trachea and bronchi - 1-3um = reach alveoli Seen histologically
Features of smoke poisoning
Effect of CO and noxious gases - incapacitation and death - not routinely measured CO and cyanide commonly measure Other gases include - HCl - NO2 - aldehydes - benxene - ammonia - SO2 - phenol - acrolein
Causes of toxic gases
CO2 - all combustibles containing carbon NO2 - cellulose - polyurethanes - acrylonitrile HCl - PVC HCN - hydrogen cyanide - wool - silk - nylons - polyurethanes Aldehydes - wool - cotton - paper - plasters - wood - nylon - polyester resin Benzene - petroleum - plastics - polystyrene Ammonia - melamine - nylon Effects may be additive so that non-fatal levels of each in combination may kill
Burn depth
First degree = superficial
Second degree = partial skin thickness
Third degree = full skin thickness
Fourth degree = through fat, down to muscle/tendon
Features of first degree burns
Involves epidermis only
Redness, swelling and pain (48-72 hours)
Brief exposure to high intensity heat or long exposure to low intensity heat (sunburn)
Peeling and healing in 5-10 days without scarring
Features of second degree burns
Involves epidermis and a variable proportion of the underlying dermis
- superficial - painful, blistered heals in 7-14 days
- deeper - painless, healing is slow with scar
Blister formation
Fluid loss and metabolic imbalance
May require grafting
Features of third degree burns
Involves epidermis, dermis and underlying tissue
Not painful - as nerves destroyed
Heat damage to vessels leaves tissue avascular and waxy
Fluid loss and metabolic imbalance
Will require grafting - if survived
Types of burns in childhood
Accidental - hot water scalds - fires - open fire, electric and gas fire Deliberate - cigarette burns - scalding - hot objects - iron, hair tongs
Rule of Nines
Able to give rough guide to body percentage covered by burns > 50% gives poor prognosis Head = 9% Front of torso = 18% Back of torso = 18% Each arm = 9% Each leg = 18% Victims palm = 1% - useful to calculate burn size
Compications of burns
First 48 hours - fluid loss - hypovolaemia - shock - renal failure 2-6 days - burn oedema - ischaemia - conversion - 1st degree burns become 2nd degree to due ischemia - airway oedema - respiratory failure 7 days + - infection - tourniquet effect - healing constricts blood supply
Features of a flash fire
Very intense brief fire caused by explosive ignition of hydrocarbon vapours - petrol gases Directionality may be seen Very high temperatures - 500-950°C Also produces Soot, CO and toxic gases
Features of sponatneous human combustion
Not true spontaneous combustion May be natural death with PM burning Ignition source usually cigarette Slow, smouldering fire - hours - clothing acts as wick - body fat acts as fuel Fire damage localised to body and surroundings
Features of cremated remains
800-900°C Takes 2-3 hours Cremation is not complete Leaves 1-1.5kg white calcinated bone and ash - ends of long bones - skull fragments - pelvic fragments
Types of burns
Thermal
Electrical
Chemical
Features of scalds
Moist heat - steam - hot liquid Resembles first or second degree burns - red swollen, blistered painful - well demarcated - no singeing, charring or carbonisation Patterns due to splash, tipping, trickling or dipping - areas spared by clothing
Scald patterns
Sparing in areas covered by clothes Flow - gravity and cooling Splash - thrown, often irregular Glove and stocking - dipping of hands and feet Doughnut - sitting in bath - sparing of contact areas - buttocks and knees
Features of electrical burns
Tissue damage depends on - voltage applied - resistance of skin - wet or dry - resistance of tissues - current which flows - duration of contact - deep burning Voltage = current x resistance Duration of flow is also important - 50-80mA across heart for a few secs is usually fatal
Features of fatal electrocution
When body forms part of electrical circuit
Current flows from entry to exit along path of least resistance
Dry skin has a high resistance - high heat on entry/exit
Blood vessels and nerves have low resistance
Vital area
- hand to opposite foot - across chest - heart -> VF
- across chest - respiratory muscle paralysis
- through head - cardiac and respiratory centre in brain stem
Features of domestic electrocution
Accidents are common
Invisible risk - most deaths accidental
Wet hands and surfaces increase risk
- bathroom and kitchen
Suicide is rare
240V, 50Hz alternating current is very dangerous
- likely to cause cardiac arrhythmia and arrest (VF)
- spasm of hand and forearm muscles causes spasm and hold-on
Prolonged contact causes burning - continues PM
Features of electrical injuries
Often no visible mark - broad area of contract - moist or sweaty skin Burn at entry site - often hands - current flow easily through tissues - diffuse current pathway - > no internal injury - muscles and verves readily paralysed Burn at exit site - often feet
Features of firm contact electrical injuries
Collapsed blister
Surrounding zone of erythema
Peripheral ring of pallor
Metallisation of skin
Features of loose contact electrical injuries
Sparks leap gap between source and entry
- distance depends on voltage
- 1000V -> few mm
- 5000V -> 1cm
- 100 000V -> 35cm
Melts epidermal keratin which cools to form a localised hard brown nodule
Multiple spark lesions from HV - crocodile skin
Clothes may igniteFeatures of a lightening strike
Hundreds of deaths worldwide - particularly tropics Charged cloud discharges to earth - direct strike over/through victim - indirect transmission - crane driver - side flash from other objects Gigantic voltages and current flow - kA Always accidental Scene may arouse suspicion Clothing scorched and torn by blast Skin burn near metal objects Arborescent marks
Features of high voltage electrocution
Pylons and sub-stations - accidents at work Spark lesions HV may fling victim clear Prolonged contact causes gross burning
Features of chemical burns
Due to corrosive acids and alkalis Usually accidental Suicidal ingestion of corrosives is rare - pain, vomiting - SOB, difficultly swallowing - perforation of oesophagus or stomach - shock Tissue damage depends on - nature of chemical - quantity applied - strength/concentration - duration of application
Features of acid burns
Acids with pH < 2 produce coagulative necrosis
- nitric acid -> yellow brown scab
- sulphuric acid -> black-brown scab
- hydrochloric acid -> white to grey scab
- carbolic acid -> light grey to light brown scab
Features of alkali burns
Alkalis with pH > 11.5 produce liquefactive necrosis Penetrates more deeply than acid burns Caustic alkalis - caustic soda - NaOH - ammonium hydroxide - AmOH4 Grey white mucoid burn
