Exercise can increase body temperature by several degrees. (T/F)
True
Heat load:
Heat generated by oxidation of metabolic products and heat acquired from the environment
Daily cyclic variation
Lowest early in the morning, highest in the afternoon
Heat flows from _____ to _____ areas
Hotter to cooler
What are the four mechanisms of heat transfer?
Conduction, convection, radiation and evaporation (insensible and sweat loss)
Conduction is:
The direct transfer of heat from one object to another
Conduction to water is 25X that of air
Radiation is:
Heat transfer by emission of infrared rays (sun, radiator/heaters)
Evaporation is:
Loss of heat when water vaporizes into the atmosphere
The primary means by which an overheated body cools itself is through_______
Evaporation
Two modes of body water loss is ______ and _______
Sweat loss-water lost from skin due to sweat glan activity
(up to 700ml/hr)
Insensible loss-water lost by skin and lungs (600 ml perday)
Convection is:
Movement of air currents around an object with resultant transfer if heat by conduction and evaporation
Increased heat loss is due to…
Decreased environmental temperature
Increasedconvection
Wet skin
Increased blood flow to skin
Riskof hypothernia
Decreased heat loss is due to….
Increased environmental temperature
Increased insulation (body fat, clothing)
High humidity
Risk of hyperthermia
When environmental temperature exceeds body temperature:
Body gains heat by radiation and conduction
Body looses heat only by evaporation
______interferes with evaporation even though sweating continues
High humidity
What happens during hyperthermia?
Core temperature greater that 105F
Occurs when heat load exceeds heat loss
Mild forms of heat illness (body temperature normal or minimally elevated)
Vigorous exercise in hot environment can cause______
Heat cramps
(may be due to salt depletion)
Heat exhaustion is due to….
Exercise in hot environment
Due to loss of salt and water
Headache, n & v, dizziness, weak
Acclimatization causes
Changes in sweat production
Aldosterone increases salt reabsorbtion from sweat
In hot weather the normal max rate of sweat is 700ml per hour (T/F)
True- rate can be increased to 1500ml per hour
Unacclimatized person may lose ___g salt per day at high temperatures
30
What happens when someone suffers from heatstroke?
Normal heat dissipating mechanisms of the body become incapable of compensating for increased environmental heat
A life threatening condition-required immediate treatment
Increased body temp-causes direct themal injury to the cells and tissues
Temp 105F or greater
Mortality up to ___% when body temperature greater that 106F
75
Environmental causes of Hyperthermia
High temperature
High humidity
Non-environmental causes of hyperthermia
Brainhemorrhage
Salicylate(asprin) overdose
Reaction to anesthetics or antipsychotic drugs
Cocaine/amphetimines
Signs and symptoms of hyperthermia
Hot dry skin with absence of sweating
n/v, musclecramps, shortness of breath
central nervous system dysfunction-hallucinations
vasodilatation-decrease in blood volume, circulatory collapse and heart failure
Autopsy findings of deaths due to hyperthermia
Autopsy findings are non specific
Diagnosis of heat stroke can be made if : post mortem core body temp indicates hyperthermia (and environmental temp is lower) and autopsy does not reveal anyother cause of death
Factors that cause Increased risk of hyperthermia:
Alcoholism-dilates skin capillaries
Extremes of age
Obesity
Heartdisease
Physical exertion
Hypothermia is:
Defined as core body temp of less than 95F (35C)
Can occur when heat loss exceeds heat production
What are the body defenses against cold?
Vasoconstructionof skin and muscle blood vessels
Increased heat production
Shivering –increased muscle metabolism
Chemical thermogenesis- brown fat, especially important in infants, production of heat instead of atp
Increased risk of hypothermia
extremes of age- infants have a high surface to volume ratio
immersin in water
wet clothing
alcohol intoxication
preexisting disease-hypothyroid
inadequate nutrition
physioloic effects of hypothermia
decreased repiration and heart rate
menal confusion and deterioration-ending in euphoria
unstable blood sugar
cardiac arrhythmias-atrial and ventricular fibrillation
Scene investigation in hypothermia
Environmental temperature does not always have to be extremely low
Hide and die syndrome
Paradoxical undressing
Hide and die syndrome
Terminal behavior in 20% of hypothermia
Primitive brainstem reflex to hide (body found behind furniture, under bed)
Paradoxical undressing
Terminal behavior in 50% of hypothermia deaths due to hallucinations and “paradoxical” feeling of warmth
External examination autopsy findings in hypothermia deaths:
Pink (cherry red) livor mortis
Brownish-pink discoloration to skin of joint surfaces and perhaps face
Possible frostbite
Internal examination autopsy findings in hypothermia deaths:
Changes are present with a period of survival before death
Acute gastric erosions- wischnewsky ulcers
Acute hemorrhagic pancreatitis
Pulmonary edema
Air blast cases what type of injuries?
Ear and lung injuries
Water blast injuries cause what type of injuries?
Abdominal injuries
What are some of the effects of blast injuries to consider?
Local heat effects
Blast wave striking the body
Flying debris striking the body
Human body in motion striking other objects
Other structures collapsing on the body
High order explosives
Supersonic pressure wave producing all 5 injury types (heat, blast
wave, flying debris, human body in motion, structural collapse
Dynamite
Plastic explosives- C4
Lower order explosives
Subsonic pressure waves-usually no blast wave damage to body
Gunpowder
Goals of death investigation of bombing:
Reconstruct the explosive device-compound, type ofdetonation mechanism
Determine role of the deceased: intended victim, innocent bystander, bomb manufacturer
Name the three bomb types.
Straight bomb
Disguised bomb
Hidden bomb
straight bomb
eplosive device that can be easily recognized as a bomb- ex pipe bomb
disuised bomb
explosive device housed in a non-suspicios container
trigger device- pull, application of pressure, release of pressure, time delay
hidden bomb
explosive device placed in a vehicle or other large complex housing
