Patho - 4th Asessment - Environmental Diseases Ii - 2007

Environmental Diseases II Dr Issam Francis

Physical Environment • Motor vehicles are a major cause of injury • 40% of deaths resulting from motor vehicle accidents involve ethanol

UNINTENTIONAL DEATHS, HOMICIDES, AND SUICIDES IN THE UNITED STATES IN 1994 Cause

Unintentional Deaths

Motor vehicle Occupant Pedestrian Motorcyclist

42,000 34,000 6,000 1,800

Bicycle

800

Fall Fire or scalding Drowning Poisoning Firearm Other

14,000 4,000 4,000 9,000 1,400 16,000

Homicides

Suicid 390 110 280

25 200 52 48 18,000 6,800

720 170 380 5,300 19,000 5,000

Physical Environment Injuries caused by physical environment result from: 3. 4.

Human activities External forces, can be

These can be divided into four categories: 7. Mechanical force 8. Heat and cold 9. Electrical injuries 10. High altitudes

Physical Environment Mechanical force may inflict • Soft tissue injuries • Bone injuries • Head injuries Soft tissue injuries can be: 7. Superficial (involving mainly the skin) 8. Deep (associated with visceral damage)

Physical Environment The skin injuries: I- Abrasion: • Represents basically a scrape • Superficial epidermis is torn off • Regeneration without scarring unless infection complicates the process.

The skin injuries: II- Laceration • • • • •

An irregular tear in the skin produced by overstretching May be linear or stellate, depending on the tearing force bridging strands of tissue Margins are frequently hemorrhagic and traumatized Cannot be neatly approximated by sutures, leaving excessive scar

• Deep tissues and organs may sustain lacerations from an external blow with or without apparent superficial injury (e.g. liver /spleen)

Physical Environment The skin injuries: III- Incision • A cut made by a sharp object# • Margins of the incision are usually relatively clean, • No bridging strands of tissue • Can be neatly approximated by sutures, leaving little or no scar

Physical Environment The skin injuries: IV- Contusion • An injury caused by a blunt force that damages small blood vessels and causes interstitial bleeding, usually without disruption of the continuity of the tissue

Physical Environment THERMAL INJURIES •

Both excess heat and excess cold are important causes of injury.

Thermal Burns The clinical significance of burns depends on the following important factors: 9. Depth of the burn 10. Percentage of body surface involved 11. Presence of internal injuries from inhalation of hot and toxic fumes 12. Promptness and efficacy of therapy 13. Prevention or control of wound infections

Physical Environment Thermal Burns: Partial-thickness burns At least the deeper portions of dermal appendages spared a- first-degree burns (epithelial involvement only) b- second-degree burns (both epidermis and superficial dermis) A full-thickness burn (third- and fourth-degree burns): • Total destruction of epidermis and dermis • Loss of the dermal appendages

Physical Environment Hyperthermia Prolonged exposure to elevated ambient temperatures can result in: 5. Heat cramps 6. Heat exhaustion 7. Heat stroke.

Physical Environment Heat cramps • Result from loss of electrolytes through sweating • Cramping of voluntary muscles with vigorous exercise, is the hallmark. • Heat-dissipating mechanisms maintain normal core body temperature.

Physical Environment Heat exhaustion • • • •

Most common heat syndrome Onset is sudden Prostration and collapse Results from a failure of the CVS to compensate for hypovolemia, secondary to water depletion • After brief a period of collapse, equilibrium is spontaneously re-established.

Physical Environment Heat stroke Associated with • High ambient temperatures • High humidity – – –

Thermoregulatory mechanisms fail sweating ceases core body temperature rises

The underlying mechanism is marked generalized peripheral vasodilation with peripheral pooling of blood and a decreased effective circulating blood volume

Candidates • • •

Elderly persons, individuals Physical stress (athletes and military recruits) Persons with cardiovascula

Physical Environment Hypothermia Prolonged exposure to low ambient temperature leads to hypothermia This is commoner with: • Homeless persons • High humidity • Wet clothing • Dilation of superficial blood vessels as a result of the ingestion of alcohol. At about 32°C (90°F) there is: • Loss of consciousness • Bradycardia • Atrial fibrillation

Physical Environment Chilling or freezing of cells and tissues causes injury in two ways:

Direct effects •

Physical damage of cells high salt concentrations due to crystallization of the intracellular and extracellular water.

Indirect effects ( circulatory changes): 1. Slow drop in temperature: – –

vasoconstriction , increased permeability, edema “Trech Foot”

2. sudden sharp persistent drop in temperature:

–

vasoconstriction and increased viscosity of the blood in local area

– –

ischemic injury and degenerative changes in peripheral nerves hypoxic changes and infarction may develop (e.g., gangrene of toes or feet).

Physical Environment ELECTRICAL INJURIES The passage of an electric current through the body may cause: • No effect • Sudden death by disruption of neural regulatory impulses • Thermal injury to organs in the pathway of the current Many variables are involved, but most important are 9. Resistance of the tissues to electric current 10.Intensity of the current • • •

The greater the resistance of tissues, the greater the heat generated All tissues of the body are conductors of electricity, Resistance to flow varies inversely with tissue water content

Physical Environment ELECTRICAL INJURIES •

The thermal effects of the passage of the electric current depend on its intensity.

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High-intensity current, such as lightning along the skin, produces linear burns known as lightning marks

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Current is conducted around the victim (so-called flashover), blasting and disrupting the clothing but doing little injury

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Lightning is transmitted internally, may produce sufficient heat and steam to explode solid organs, fracture bones, or char areas of organs.

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Less intense voltage may heat, coagulate, or rupture vessels and cause hemorrhages or infarctions.

Physical Environment INJURIES RELATED TO CHANGES IN ATMOSPHERIC PRESSURE Depending on the direction of change (increase or decrease) in atmospheric pressure, its rate of development, and the magnitude of change, four syndromes can be produced: – – – –

High-altitude illness Blast injury Air or gas embolism Decompression disease (caisson disease / barotrauma)

Physical Environment High-Altitude Illness. • Encountered in mountain climbers • At altitudes above 4000 m. • The lowered oxygen tension produces progressive mental confusion • Increased capillary permeability with systemic and, in particular, pulmonary edema

Physical Environment Blast Injury. Violent increase in pressure either in • The atmosphere (air blast) or • In water (immersion blast) With air blast, the compression wave impinges on the side toward the explosion and so may collapse the thorax or violently compress the abdomen, with rupture of internal organs. The pressure wave may enter the airways and damage the alveoli. The following wave of decreased pressure, with sudden expansion of the abdomen and thorax, may rupture the intestines or lungs. In immersion blast, the pressure is supplied to the body from all sides, inducing injuries similar to those of air blast.

Physical Environment Air or Gas Embolism This may occur as a complication of 4. Scuba diving 5. Mechanical positive-pressure ventilatory support 6. Hyperbaric oxygen therapy 7. Rarely as a manifestation of decompression disease Abnormal increase in intra-alveolar air or gas pressure, leading to: • • • • •

Tearing of tissue Entrance of air into the interstitium and small blood vessels. Pulmonary, mediastinal, and subcutaneous emphysema Coalescence of numerous small air or gas emboli in arterial circulation may lead acutely to stroke May cause sudden death.

Physical Environment Decompression (Caisson) Disease. In deep-sea divers and underwater workers who spend long periods in caissons or tunnels, under increased atmospheric pressure. Henry's law: The solubility of a gas in a liquid (e.g., blood) is proportional to the partial pressure of that gas in the environment. As the underwater atmospheric pressure increase, oxygen and accompanying gases (nitrogen or helium) dissolve in the blood and tissue fluids. With decompression , the dissolved gases come out of solution and form minute bubbles in the bloodstream and tissues.

• • • •

Periarticular bubbles produce the bends Bubbles within lung emboli give rise to respiratory produce the chokes. CNS: headache and visual disturbances to behavioral changes Foci of aseptic necrosis, typically of femoral and humeral heads

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Periarticular bubbles produce the bends Bubbles within lung emboli give rise to respiratory produce the chokes. • CNS: headache and visual disturbances to behavioral changes • Foci of aseptic necrosis, typically of femoral and humeral heads