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In The Name of The GOD
Specialized English
Occupational Health
Hyperthermia
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Hyperthermia
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An analog medical thermometer showing a temperature of 38.7 °C (101.7 °F)
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Hyperthermia is elevated body temperature due to failed thermoregulation that occurs when a body produces
or absorbs more heat than it dissipates. Extreme temperature elevation then becomes a medical emergency
requiring immediate treatment to prevent disability or death.
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Common causes include heat stroke and adverse reactions to drugs.
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The former is an acute hyperthermia caused by exposure to excessive heat, or combination of heat and
humidity, that overwhelms the heat-regulating mechanisms of the body causing uncontrolled elevation of body
temperature. metabolism.
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Hyperthermia
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The latter is a relatively rare side effect of many drugs, particularly those that affect the central nervous system.
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Malignant hyperthermia is a rare complication of some types of general anesthesia.
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Hyperthermia can be deliberately induced using drugs or medical devices and may be used in the treatment of
some kinds of cancer and other conditions, most commonly in conjunction with radiotherapy.[1]
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Hyperthermia differs from fever in that the body's temperature set point remains unchanged.
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The opposite is hypothermia, which occurs when an organism's temperature drops below that required to
maintain normal metabolism.
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Temperature Set Point
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There is accepted scientific support for the concept of a temperature set point - that is, maintenance of an
optimal temperature for the metabolic processes that life depends on.
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Nervous activity in the preoptic-anterior hypothalamus of the brain triggers heat losing (sweating, etc.) or heat
generating activities (shivering and muscle contraction, etc.) through stimulation of the autonomic nervous
system.
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The pre-optic anterior hypothalamus has been shown to contain warm sensitive, cool sensitive, and
temperature insensitive neurons, to determine the body's temperature setpoint.
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As the temperature that these neurons are exposed to rises above 37C. degrees, the rate of electrical discharge
of the warm-sensitive neurons increases progressively.
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Cold-sensitive neurons increase their rate of electrical discharge progressively below 37C. degrees.
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Temperature Set Point
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Hyperthermia is defined as a temperature greater than 37.5–38.3 °C (100–101 °F), depending on the reference
used, that occurs without a change in the body's temperature set point.
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The normal human body temperature in health can be as high as 37.7 °C (99.9 °F) in the late afternoon.
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Hyperthermia requires an elevation from the temperature that would otherwise be expected.
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Such elevations range from mild to extreme; body temperatures above 40 °C (104 °F) can be life threatening.
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Hyperthermia
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Signs and symptoms
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Hot, dry, skin is typical [9] as blood vessels dilate in an attempt to increase heat dissipation, sometimes leading to
swollen lips. An inability to cool the body through perspiration may cause the skin to feel dry.
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Other signs and symptoms vary. Accompanying dehydration can produce nausea, vomiting, headaches, and low
blood pressure and the latter can lead to fainting or dizziness, especially if the standing position is assumed
quickly.
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Hyperthermia
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Signs and symptoms
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In severe heat stroke, there may be confused, hostile, or seemingly intoxicated behavior. Heart rate and
respiration rate will increase (tachycardia and tachypnea) as blood pressure drops and the heart attempts to
maintain adequate circulation.
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The decrease in blood pressure can then cause blood vessels to contract reflexly, resulting in a pale or bluish skin
color in advanced cases. Young children, in particular, may have seizures.
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Eventually, organ failure, unconsciousness and death will result.
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Hyperthermia
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Causes
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Heat stroke
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Heat stroke occurs when thermoregulatory mechanisms are overwhelmed by a combination of excessive
metabolic production of heat (exertion), excessive environmental heat, and insufficient or impaired heat loss,
resulting in an abnormally high body temperature.[9]
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In severe cases, temperatures can exceed 40 °C (104 °F).[10] Heat stroke may be non-exertional (classic) or
exertional.
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Significant physical exertion in hot conditions can generate heat beyond a body's ability to cool, because the
heat and humidity of the environment reduce the efficiency of the body's normal cooling mechanisms.[9]
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Hyperthermia
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Causes
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Heat stroke
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The mechanisms available for heat loss are limited to vasodilation of skin vessels and increased rate of sweating.
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The vasodilation dissipates heat by convection while sweating dissipates it by evaporation. However,
thermoregulation
can be assisted with shade or fans.
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Other factors, such as insufficient water intake, consuming alcohol, or lack of air conditioning, can worsen the
problem.
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The principles of physics involved include Newton's law of cooling which states that dry heat loss is proportional
to temperature difference between the human body (shell) and surroundings and Stefan-Boltzmann law which
states that the higher the temperature of an object, the more it radiates, and the energy radiating from an object
and received by the human body is proportional to temperature difference between object and skin.
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Hyperthermia
Causes
Heat stroke
Non-exertional heat stroke is predominant in the young and the elderly. In the elderly in particular, it can be
precipitated by medications such as anticholinergic drugs, antihistamines, and diuretics[9] that reduce
vasodilation, sweating, and other heat-loss mechanisms.
In this situation, the body's tolerance for high environmental temperature may be insufficient, even at rest.
Heat waves in the United States are followed by a rise in the death rate and these 'classical hyperthermia'
deaths involve the elderly and infirm.
Hyperthermia
Causes
Heat stroke
This is partly because thermoregulation involves cardiovascular, respiratory and renal systems which may be
inadequate for the additional stress imposed upon aging and pre-existing disease, further compromised by
many of the medications taken by the elderly.
During the July 1995 heat wave in Chicago, there were at least 700 heat-related deaths.
The strongest risk factors were being confined to bed, and living alone, while the risk was reduced for those with
working air conditioners and those with access to transportation.
Even then, reported deaths may be underestimates as diagnosis can be misclassified as stroke or heart attack.[11]
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Specialized English
Occupational Health
Hypothermia
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Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal
metabolism and body functions which is defined as 35.0 °C (95.0 °F).
Body temperature is usually maintained near a constant level of 36.5–37.5 °C (98–100 °F) through biologic
homeostasis or thermoregulation.
If exposed to cold and the internal mechanisms are unable to replenish the heat that is being lost, a drop in core
temperature occurs.
As body temperature decreases, characteristic symptoms occur such as shivering and mental confusion.
Hypothermia is the opposite of hyperthermia which is present in heat exhaustion and heat stroke.
One of the lowest documented body temperature from which anyone has recovered was 13.0 °C (55.4 °F) in a
near-drowning incident involving a 7-year-old girl in Sweden in December 2010.[1]
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Hypothermia
Normal human body temperature in adults is 34.4–37.8 °C (94–100 °F).[8] Sometimes a narrower range is stated,
such as 36.5–37.5 °C (98–100 °F).[9]
Hypothermia is defined as any body temperature below 35.0 °C (95.0 °F).
It is subdivided into four different degrees,
mild 32–35 °C (90–95 °F);
moderate, 28–32 °C (82–90 °F);
severe, 20–28 °C (68–82 °F); and
profound at less than 20 °C (68 °F).[10]
This is in contrast to hyperthermia and fever which are defined as a temperature of greater than 37.5 °C (99.5
°F)-38.3 °C (100.9 °F).[5]
Other cold-related injuries that can either be present alone or in combination with hypothermia include:
Chilblains are superficial ulcers of the skin that occur when a predisposed individual is repeatedly exposed to
cold.[11]
Frostbite involves the freezing and destruction of tissue.[11]
Frostnip is a superficial cooling of tissues without cellular destruction.[12]
Trench foot or immersion foot is due to repetitive exposure to wet, non-freezing temperatures.[11]
Hypothermia
Signs and symptoms
The signs and symptoms vary depending on the degree of hypothermia and may be divided by the three stages
of severity.
Mild
Symptoms of mild hypothermia may be vague[13] with sympathetic nervous system excitation (shivering,
hypertension, tachycardia, tachypnea, and vasoconstriction).
These are all physiological responses to preserve heat.[14] Cold diuresis, mental confusion, as well as hepatic
dysfunction may also be present.[15]
Hyperglycemia may be present, as glucose consumption by cells and insulin secretion both decrease, and tissue
sensitivity to insulin may be blunted.[16]
Sympathetic activation also releases glucose from the liver. In many cases, however, especially in alcoholic
patients, hypoglycemia appears to be a more common presentation.[16]
Hypoglycemia is also found in many hypothermic patients because hypothermia often is a result of
hypoglycemia.
Hypothermia
Signs and symptoms
Moderate
Low body temperature results in shivering becoming more violent. Muscle mis-coordination becomes
apparent.[18][19][20]
Movements are slow and labored, accompanied by a stumbling pace and mild confusion, although the victim
may appear alert.
Surface blood vessels contract further as the body focuses its remaining resources on keeping the vital organs
warm.
The victim becomes pale. Lips, ears, fingers and toes may become blue.
Severe
As the temperature decreases further physiological systems falter and heart rate, respiratory rate, and blood
pressure all decreases.
This results in an expected HR in the 30s with a temperature of 28 °C (82 °F).[15]
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Difficulty in speaking, sluggish thinking, and amnesia start to appear; inability to use hands and stumbling is also
usually present.
Cellular metabolic processes shut down. Below 30 °C (86 °F), the exposed skin becomes blue and puffy, muscle
coordination becomes very poor, walking becomes almost impossible, and the person exhibits
incoherent/irrational behavior including terminal burrowing or even a stupor.
Pulse and respiration rates decrease significantly, but fast heart rates (ventricular tachycardia, atrial fibrillation)
can occur.
Major organs fail. Clinical death occurs.
Because of decreased cellular activity in stage 3 hypothermia, the body will actually take longer to undergo brain
death.[citation needed
Hypothermia
Paradoxical undressing
Twenty to fifty percent of hypothermia deaths are associated with paradoxical undressing.
This typically occurs during moderate to severe hypothermia, as the person becomes disoriented, confused, and
combative.
They may begin discarding their clothing, which, in turn, increases the rate of heat loss.[21][22]
Rescuers who are trained in mountain survival techniques are taught to expect this; however, some may assume
incorrectly that urban victims of hypothermia have been subjected to a sexual assault.[23]
One explanation for the effect is a cold-induced malfunction of the hypothalamus, the part of the brain that
regulates body temperature.
Another explanation is that the muscles contracting peripheral blood vessels become exhausted (known as a
loss of vasomotor tone) and relax, leading to a sudden surge of blood (and heat) to the extremities, fooling the
person into feeling overheated.[23]
Hypothermia
Terminal burrowing
An apparent self-protective behaviour known as terminal burrowing, or hide-and-die syndrome,[24] occurs in the
final stages of hypothermia.
The afflicted will enter small, enclosed spaces, such as underneath beds or behind wardrobes.
It is often associated with paradoxical undressing.[25]
Causes
The rate of hypothermia is strongly related to age in the United States.
Hypothermia usually occurs from exposure to low temperatures, and is frequently complicated by alcohol.
Any condition that decreases heat production, increases heat loss, or impairs thermoregulation, however, may
contribute.[26]
Thus, hypothermia risk factors include: any condition that affects judgment (hypoglycemia), the extremes of
age, poor clothing, chronic medical conditions (such as hypothyroidism and sepsis), substance abuse,
homelessness, and living in a cold environment.[27][28]
Hypothermia also occurs frequently in major trauma. Hypothermia is also observed in severe cases of anorexia
nervosa.
Alcohol
Alcohol consumption increases the risk of hypothermia via its action as a vasodilator. It increases blood flow to
the body's skin and extremities, making a person feel warm, while increasing heat loss.[29]
Between 33 and 73% of cases of hypothermia are complicated by alcohol.
Hypothermia
Water
Hypothermia continues to be a major limitation to diving in cold water.[18]
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The limitation of finger dexterity due to pain or numbness decreases general safety and work capacity, which
consequently increases the risk of other injuries.[18][20]
Due to the use of gas mixtures containing helium at extreme depths, the use of argon inflation for dry suits, or
hot water suits become a necessity for diving deep in colder waters.
Other predisposing factors leading to immersion hypothermia include dehydration, inadequate rewarming with
repetitive diving, starting a dive while wearing cold, wet dry suit undergarments, sweating with work,
inadequate thermal insulation (for example, thin dry suit undergarment), and poor physical conditioning.[18]
Heat is lost more quickly in water[18] than on land. Water temperatures that would be quite reasonable as
outdoor air temperatures can lead to hypothermia.
A water temperature of 10 °C (50 °F) often leads to death in one hour, and water temperatures hovering at
freezing can lead to death in as little as 15 minutes.[32]
A notable example of this occurred during the sinking of the Titanic, in which most people who entered the −2
°C (28 °F) water died within 15–30 minutes.[33]
Water at a temperature of 26 °C (79 °F) will, after prolonged exposure, lead to hypothermia.
Hypothermia
Pathophysiology
Heat is primarily generated in muscle tissue, including the heart, and in the liver, while it is lost through the skin
(90%) and lungs (10%).[13] Heat production may be increased 2 to 4 fold through muscle contractions ( i.e.
exercise and shivering ).[13] Rates of bodily heat loss are determined, as with any object, by convection,
conduction, and radiation.[13] The rates of these can be affected by clothing and other environmental conditions.
Many changes to physiology occur as body temperature decreases. These occur in the cardiovascular system
leading to the Osborn J wave and other dysrhythmias, decreased CNS electrical activity, cold diuresis, and noncardiogenic pulmonary edema
Hypothermia
Diagnosis
Atrial fibrillation and Osborn J waves in a person with hypothermia. Note what could be mistaken for ST
elevation.
Accurate determination of core temperature often requires a special low temperature thermometer, as most
clinical thermometers do not measure accurately below 34.4 °C (93.9 °F).[14]
A low temperature thermometer can be placed rectally, esophageally, or in the bladder.
The classical ECG finding of hypothermia is the Osborn J wave. Also, ventricular fibrillation frequently occurs at
<28 °C (82 °F) and asystole at <20 °C (68 °F).[13]
The Osborn J may look very similar to those of an acute ST elevation myocardial infarction.[15]
Thrombolysis as a reaction to the presence of Osborn J waves is not indicated, as it would only worsen the
underlying coagulopathy caused by hypothermia.
As a hypothermic person's heart rate may be very slow, prolonged palpation could be required before detecting
a pulse.
In 2005, the American Heart Association recommended at least 30–45 seconds to verify the absence of a pulse
before initiating CPR.[36]
Most physicians are recommended not to declare a patient dead until their body is warmed to a normal body
temperature, since extreme hypothermia can suppress heart and brain function.
Hypothermia
Prevention
Appropriate clothing helps to prevent hypothermia.
Synthetic and wool fabrics are superior to cotton as they provide better insulation when wet and dry.
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Some synthetic fabrics, such as polypropylene and polyester, are used in clothing designed to wick perspiration
away from the body, such as liner socks and moisture-wicking undergarments.
The United States Coast Guard promotes using life vests as a method of protection against hypothermia through
the 50/50/50 rule:
If someone is in 50 °F (10 °C) water for 50 minutes, he/she has a 50 percent better chance of survival if wearing a
life jacket.
A heat escape lessening position can be used to increase survival in cold water.
Specialized English
Occupational Health
Barotrauma
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Barotrauma
Barotrauma, otitic & Barotrauma, sinus
Barotrauma is physical damage to body tissues caused by a difference in pressure between an air space inside or
beside the body and the surrounding fluid.[1][2]
Barotrauma typically occurs to air spaces within a body when that body moves to or from a higher pressure
environment, such as when a SCUBA diver, a free-diving diver or an airplane passenger ascends or descends, or
during uncontrolled decompression of a pressure vessel. Boyle's law defines the relationship between the
volume of the air space and the ambient pressure.
Damage occurs in the tissues around the body's air spaces because gases are compressible and the tissues are
not.
During increases in ambient pressure, the internal air space provides the surrounding tissues with little support
to resist the higher external pressure.
During decreases in ambient pressure, the higher pressure of the gas inside the air spaces causes damage to the
surrounding tissues if that gas becomes trapped.
Types of injury
Examples of organs or tissues easily damaged by barotrauma are:
middle ear (barotitis or aerotitis)[1][2][3][4][5][6]
paranasal sinuses[1][2][4] (causing Aerosinusitis)
lungs[1][2][7][8]
eyes[1][2] (the unsupportive air space is inside the diving mask[9])
skin[1][2] (when wearing a diving suit which creates an air space)
bone (bone necrosis and temporal lobe injury)[10]
Teeth (causing Barodontalgia, i.e. barometric pressure related dental pain,[11][12][13][14][15] or dental
fractures[16][17][18])
Diving barotrauma
Ear barotrauma
Barotrauma can affect the external, middle, or inner ear.
Middle ear barotrauma (MEBT) is the most common being experienced by between 10% and 30% of divers and
is due to insufficient equilibration of the middle ear.
External ear barotrauma may occur on ascent if high pressure air is trapped in the external auditory canal either
by tight fitting SCUBA equipment or ear wax.
Inner ear barotrauma (IEBT) though much less common than MEBT shares a similar mechanism.
Mechanical trauma to the inner ear can lead to varying degrees of conductive and sensorineural hearing loss as
well as vertigo.
Barosinusitis
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The sinuses similar to other air filled cavities are susceptible to barotrauma if their openings become obstructed.
This can result in pain as well as epistaxis.
Diving barotrauma
Mask squeeze
If a diver's mask is not equalized during descent the relative negative pressure can produce petechial
hemorrhages in the area covered by the mask along with subconjunctival hemorrhages.
Pulmonary barotrauma
Pulmonary (lung) pressure damage in scuba divers is usually caused by breath-holding on ascent.
The compressed gas in the lungs expands as the ambient pressure decreases causing the lungs to over expand
and rupture unless the diver breathes out.
Diving barotrauma
Mask squeeze
The lungs do not sense pain when over-expanded giving the diver little warning to prevent the injury.
This does not affect breath-hold skin divers as they bring a lungfull of air with them from the surface, which
merely re-expands safely to near its original volume on ascent.
The problem only arises if a breath of compressed gas is taken at depth, which will then expand on ascent to
more than the lung volume.
Pulmonary barotrauma may also be caused by explosive decompression of a pressurised aircraft.
Causes
When diving, the pressure differences needed to cause the barotrauma come from two sources:
descending and ascending in water. There are two components to the surrounding pressure acting on the diver:
the atmospheric pressure and the water pressure. A descent of 10 metres (33 feet) in water increases the
ambient pressure by approximately the pressure of the atmosphere at sea level. So, a descent from the surface
to 10 metres (33 feet) underwater results in a doubling of the pressure on the diver.
Causes
breathing gas at depth from SCUBA equipment results in the lungs containing gas at a higher pressure than
atmospheric pressure.
So a free-diving diver can dive to 10 metres (33 feet) and safely ascend without exhaling, because the gas in the
lungs had been inhaled at atmospheric pressure, whereas a SCUBA diver who breathes at 10 metres and ascends
without exhaling has lungs containing gas at twice atmospheric pressure and is very likely to suffer lifethreatening lung damage.
Avoidance and treatment
Diving barotrauma can be avoided by eliminating any pressure differences acting on the tissue or organ by
equalizing the pressure.
There are a variety of techniques:
The air spaces in the ears, and the sinuses. The risk is burst eardrum.
Here, the diver can use a variety of methods, to let air into the middle ears via the Eustachian tubes.
Sometimes swallowing will open the Eustachian tubes and equalise the ears.
The lungs. The risk includes pneumothorax, arterial gas embolism, and mediastinal and subcutanous
emphysemas.
Avoidance and treatment
which are commonly called burst lung or lung overpressure injury by divers.
To equalise, all that is necessary is not to hold the breath during ascent.
This risk does not arise when snorkel diving from the surface, unless the snorkeller breathes from a high
pressure gas source underwater, or from submerged air pockets.
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Some people have pathologies of the lung which prevent rapid flow of excess air though the passages, which can
lead to lung barotrauma even if the breath is not held during rapid depressurisation.
These people should not dive as the risk is unacceptably high. Most commercial or military diving medical
examinations will look specifically for signs of this pathology.
Avoidance and treatment
The air inside the usual eyes-and-nose diving mask (also known as a half mask).
The main risk is bleeding around the eyes from the negative pressure[9] or orbital emphysema from higher
pressures.[21]
Here, let air into the mask through the nose. Do not dive in eyes-only goggles as sometimes seen on land with
industrial breathing sets.
Air spaces inside a dry suit.
The main risk is folds of skin getting pinched inside folds of the drysuit. Most modern drysuits have a tube
connection to feed air in from the cylinder.
Air must be injected on the descent and vented on the ascent.
Following barotrauma of the ears or lungs from diving the diver should not dive again until thoroughly cleared
by a doctor, which can take many months.
• Lighting or illumination
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Lighting or illumination
Lighting or illumination is the deliberate use of light to achieve a practical or aesthetic effect.
Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural
illumination by capturing daylight.
Daylighting (using windows, skylights, or light shelves) is sometimes used as the main source of light during
daytime in buildings.
This can save energy in place of using artificial lighting, which represents a major component of energy
consumption in buildings.
Proper lighting can enhance task performance, improve the appearance of an area, or have positive
psychological effects on occupants.
Indoor lighting is usually accomplished using light fixtures, and is a key part of interior design.
Lighting can also be an intrinsic component of landscape projects.
Lighting or illumination
History
This section requires expansion. (November 2012)
With the discovery of fire, the earliest form of artificial lighting used to illuminate an area were campfires or
torches.
As early as 400,000 BCE, fire was kindled in the caves of Peking Man. Prehistoric people used primitive lamps to
illuminate surroundings.
These lamps were made from naturally occurring materials such as rocks, shells, horns and stones, were filled
with grease, caves in modern day France, dating to about 15,000 years ago.
Lighting or illumination
History
Oily animals (birds and fish) were also used as lamps after being threaded with a wick.
Fireflies have been used as lighting sources. Candles and glass and pottery lamps were also invented.[1]
Chandeliers were an early form of "light fixture". With the development of electricity and the incandescent light
bulb, the luminosity of artificial lighting improved to be able to used indoors.
They became widely used and extended the time that people could stay up, among other developments.
Lighting or illumination
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Fixtures
Lighting fixtures come in a wide variety of styles for various functions.
The most important functions are as a holder for the light source, to provide directed light and to avoid visual
glare.
Some are very plain and functional, while some are pieces of art in themselves. Nearly any material can be used,
so long as it can tolerate the excess heat and is in keeping with safety codes.
An important property of light fixtures is the luminous efficacy or wall-plug efficiency, meaning the amount of
usable light emanating from the fixture per used energy, usually measured in lumen per watt.
A fixture using replaceable light sources can also have its efficiency quoted as the percentage of light passed
from the "bulb" to the surroundings.
The more transparent the lighting fixture is, the higher efficacy. Shading the light will normally decrease efficacy
but increase the directionality and the visual comfort probability.
Lighting or illumination
Fixtures
Color temperature for white light sources also affects their use for certain applications.
The color temperature of a white light source is the temperature in Kelvin of a theoretical black body emitter
that most closely matches the spectral characteristics of the lamp.
An incandescent bulb has a color temperature around 2800 to 3000 Kelvin; daylight is around 6400 Kelvin.
Lower color temperature lamps have relatively more energy in the yellow and red part of the visible spectrum,
while high color temperatures correspond to lamps with more of a blue-white appearance.
For critical inspection or color matching tasks, or for retail displays of food and clothing, the color temperature
of the lamps will be selected for the best overall lighting effect.
Lighting or illumination
Types
A demonstration of the effects of different kinds of lighting
Lighting is classified by intended use as general, accent, or task lighting, depending largely on the distribution of
the light produced by the fixture.
Task lighting is mainly functional and is usually the most concentrated, for purposes such as reading or
inspection of materials.
For example, reading poor-quality reproductions may require task lighting levels up to 1500 lux (150
footcandles), and some inspection tasks or surgical procedures require even higher levels.
Accent lighting is mainly decorative, intended to highlight pictures, plants, or other elements of interior design
or landscaping.
General lighting (sometimes referred to as ambient light) fills in between the two and is intended for general
illumination of an area.
Indoors, this would be a basic lamp on a table or floor, or a fixture on the ceiling. Outdoors, general lighting for a
parking lot may be as low as 10-20 lux (1-2 footcandles) since pedestrians and motorists already used to the dark
will need little light for crossing the area.
Lighting or illumination
Methods
Downlighting is most common, with fixtures on or recessed in the ceiling casting light downward.
This tends to be the most used method, used in both offices and homes.
Although it is easy to design it has dramatic problems with glare and excess energy consumption due to large
number of fittings.[2]
The introduction of LED lighting has greatly improved this by approx. 90% when compared to a halogen
downlight or spotlight.
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LED lamps or bulbs are now available to retro fit in place of high energy consumption lamps.
Lighting or illumination
Methods
Uplighting is less common, often used to bounce indirect light off the ceiling and back down.
It is commonly used in lighting applications that require minimal glare and uniform general illuminance levels.
Uplighting (indirect) uses a diffuse surface to reflect light in a space and can minimize disabling glare on
computer displays and other dark glossy surfaces.
It gives a more uniform presentation of the light output in operation.
However indirect lighting is completely reliant upon the reflectance value of the surface.
Lighting or illumination
Methods
While indirect lighting can create a diffused and shadow free light effect it can be regarded as an uneconomical
lighting principle.[3][4]
Front lighting is also quite common, but tends to make the subject look flat as its casts almost no visible
shadows.
Lighting from the side is the less common, as it tends to produce glare near eye level.
Backlighting either around or through an object is mainly for accent.
Forms of lighting
Indoor lighting
LED Lighting furniture by Manfred Kielnhofer
Forms of lighting include alcove lighting, which like most other uplighting is indirect.
This is often done with fluorescent lighting (first available at the 1939 World's Fair) or rope light, or occasionally
with neon lighting. It is a form of backlighting.
Soffit or close to wall lighting can be general or a decorative wall-wash, sometimes used to bring out texture
(like stucco or plaster) on a wall, though this may also show its defects as well.
The effect depends heavily on the exact type of lighting source used.