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AHF 2203AVIATION HUMAN FACTORS
Presentation 6: Decompression Sickness and Trapped Gas
1Presented by Mohd Amirul for AMC
Recapitulate• Lets recap what we have done last session:
– Definition of Hyperventilation– Hyperventilation process– Causes of Hyperventilation– Symptoms of Hyperventilation– Preventions of Hyperventilation– Treatments of Hyperventilation– What is Cabin Pressurization?– Purpose of Cabin Pressurization– How Cabin Pressurization Works?– Advantage of Pressurized Flight– Definition of Decompression– Types of Decompression– Factors affecting Decompression’s time and severity.– Effects of Decompression.
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Presentation Outline
• Part 1: Decompression Sickness
• Part 2: Trapped Gas
3Presented by Mohd Amirul for AMC
Learning Outcomes• At the end of this session, student should be
able to:– Relate gas law to trapped gas and decompression sickness
syndromes.– Recognize the causes, symptoms, treatment, and
prevention steps of decompression sickness.– Recognize the difficulties of affected body area occur by
trapped gas during ascent and descent.– Identify causes, symptoms, treatment, and prevention
steps of each trapped gas affected body areas
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Part 1: Decompression Sickness (DCS)
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• The amount of gas in solution is proportional to the pressure of that gas over the solution
• As the pressure of the gas above a solution increases, the amount of that gas dissolved in the solution increases
• Reverse is also true, as the pressure of the gas above a solution decreases, the amount of gas dissolved in the solution decreases and forms a “bubble” of gas within the solution
Cont.Henry’s Law
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Henry’s Law IllustrationHenry’s Law Illustration
Low pressure equilibriumLow concentration
Double the pressure equilibriumDouble the concentration
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• Nitrogen dissolved in the blood responds in same way.
• Carbonated drink: Once the seal is opened, You will hear the gas that has been under pressure escaping and see the bubble are forming.
• The bubbles are CO2 gas coming out of the solution as a result of sudden exposure to lower barometric pressure (atmospheric pressure).
Cont.Example:
8Presented by Mohd Amirul for AMC
• It ambiguous to human body:– The body stores nitrogen in tissue and the fluid.– When body exposed to DECREASE barometric
pressure or rapid decompression, nitrogen dissolve on the body come out as solution.
– If nitrogen leave solution faster than the body can compensate to respiratory or circulatory systems, the nitrogen bubble will form and enlarge at different area of the bodies.
– This can cause variety of symptoms/sign: DECOMPRESSION SICKNESS.
Presented by Mohd Amirul for AMC 9
Cont.
Decompression Sickness (DCS) • Exposure to change in barometric pressure
can cause inert gasses mainly nitrogen to come out as solution and form the bubbles.
• Decompression sickness is caused by nitrogen forming as bubbles in the blood.
• As pressure decreases, gases (nitrogen) dissolved in body fluids are released as bubbles.
10Presented by Mohd Amirul for AMC
• Can occur in the blood, other fluids, or in the tissues
• This is related to the inefficient removal and transport of the expanded nitrogen gas volume from the tissues to the lungs.
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Cont.
Types of DCS
• FOUR types of DCS:• Type I (Non-Serious)– Bends– Skin Manifestations
• Type II (Serious)– Chokes– Neurological Manisfestations
Presented by Mohd Amirul for AMC 12
The Bends• Bend: Pain in the large joints (e.g. knee, elbow etc)
• Common type of DCS in aviation.
• Pain from mild to unbearable.
• If one experience may occur in other location during subsequent (following in time or order) exposure. (If reappearing at ground level during descent, can be serious condition if left untreated)
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Cont.
Skin Manifestation*manifestation: clear appearance/indication
• Symptoms: Tingling, itching, cold/warm sensation.
• Cause by form of bubble localize under the skin.– Red spot pattern appear under the skin– Usually around shoulder and upper chest.
• Continued exposure may lead to more serious forms of decompression sickness
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Cont.
The Chokes
*Chokes: Breath with great difficulties like the neck being wringed.
• Related to chest and lung.
• Bubble intrude in pulmonary vessel (blood vessel in lung).
Presented by Mohd Amirul for AMC 15
Cont.
• Symptoms– Deep and sharp pain or burning sensation under
the sternum– Shortness of breath– Feeling of suffocation with decreasing ability to
take a breath
• Might lead to feel of suffocation (poor of oxygen(Hypoxia)) and result of unconsciousness.
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Cont.
Neurological Manifestation
• Very serious type of DCS and can result in DEATH.
• Affect nervous system (brain, spinal cord, other nerves).
• Symptoms:– Headache– Visual disturbances– Unexplained fatigue– Paralysis
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Cont.
Factors or Cause affecting DCS• Altitude– Less risk below 18 000 ft MSL– Below 25,000 feet is rare– Above 25,000 feet may occur.
• Repetitive Exposure – Exposure to altitude above 18,000 ft MSL during short
period.
• Rate of ascent– The faster (short) the rate of ascent, the greater the
risk.Presented by Mohd Amirul for AMC 18
• Time (duration) at altitude– The longer you are at altitude, greater the risk.
• Age– older, greater the risk.
• Previous injury– Recent limb/joint injury, greater the risk.
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Cont.
• Ambient temperature– Exposure to very cold temperature increase the risk
of DCS
• Physical Exercise:– Physically active while flying at 18,000 ft or above,
greater the risk.
• Alcohol Consumption:– Greater the risk.
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Cont.
• Scuba Diving before Flying– During scuba diving, he/she requires breathing air
under increase atmospheric pressure.– Amount of nitrogen stores under the body
increases.– Enough time should be allowed to eliminate
excess nitrogen stored in the body. (approximately: 24 hours before fly)
– Cases of decompression sickness have occurred in individuals who fly in cabins as low at 5,000 feet
Presented by Mohd Amirul for AMC 21
Cont.
Treatments of DCS
• Emergency Treatment– 100% oxygen for everyone onboard– Declare an emergency– Descent as rapidly as possible– Immobilize affected areas– Land as soon as possible– Medical evaluation by a QUALIFIED flight surgeon.– Decompression chamber therapy if required
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Prevention of DCS
• Protective measures include: – Cabin pressurization. – Limitation of time at high altitude.
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Part 2: Trapped Gas
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Boyle’s Law• State that a volume of gas is inversely proportional
to pressure to which is subjected, with the temperature remain constant.
• E.g.: Balloon taken in certain altitude in altitude chamber.– As Pressure decrease, volume in the balloon will
EXPAND– As Pressure increase, volume in the balloon will
DECREASE.
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*Altitude Chamber: used for aerospace/high terrestrial altitude research or training to simulate effects of high altitude of human body.
Illustration of Boyle’s Law
Pressure decrease, Volume increase
Site level
10,000 feet
18,000 feet
25,000 feet
43,000 feet
Cont.
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Cont.
• Boyle’s law application to human body:
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Gases within the body are influenced by pressure and temperature changes outside the body
Ascent – pressure is decreased and gases expand. Descent – pressure is increased and gases contract. The body can withstand changes in total pressure as
long as the air pressure within the body cavities is equalized to ambient pressure
Trapped Gas• Trapped gas means the gas can’t be released
especially by our body cavities part.
• Occur inside natural cavities in human body that contains various amount of gases.
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• Our body cavities that often experienced trapped gas are:1. Middle ear2. Sinuses3. Teeth4. Stomach & Intestines (Gastrointestinal tract)
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Cont.
1. Middle Ear
FRONTALS
ETHMOIDS
SPHENOID
MAXILLARY
2. Sinus
4. Stomach and Intestines
3. Teeth
Cont.
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1. The Middle Ear
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Anatomy of EarCont.
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33
• The ear is not only an organ of hearing but also one of regulating equilibrium.
• When ascending to altitude, flight’s occupants often experience physiological discomfort during changes in atmospheric pressure.
EarCont.
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The Middle Ear
• Ascent to altitude– As ambient pressure decreases with ascent, gas
expands within the middle ear– Air escapes through the Eustachian tubes to
equalize pressure– As pressure increases, the eardrum bulges
outward until a differential pressure is achieved and a small amount of gas is forced out through eustachian tube and the eardrum relaxes.
Cont.
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• Descent to altitude– Equalization of pressure does not occur automatically– Eustachian tube performs as a flap valve and allows gas to
pass outward easily, but resists the reverse.– During descent the ambient pressure increase, the flap
valve can stop the returning air into the middle-ear to equalize the pressure.
– If pressure is not equalized• Ear block may occur and it is extremely difficult to reopen the
eustachian tube• The eardrum may not vibrate normally and decreased hearing
results (minor hearing lost).
Cont.
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Middle Ear BlockCont.
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Symptoms of Middle Ear Block
• Symptoms– “Ear congestion” (excessive accumulation of blood)– Ringing in the ears.– Inflammation.– *Discomfort.– Pain.– Temporary impairment of hearing– Bleeding (severe cases)– Eardrum rupture
37Presented by Mohd Amirul for AMC
*Middle Ear Discomfort
• A cold can produce enough congestion around the Eustachian tube to make equalization difficult.
• This causes and ear block causing a build up in pressure that can be very painful.
• Severe ear pain and loss of hearing that can last several hours to several days.
• Can cause rupture of the ear drum• Usually occurs on descent
38Presented by Mohd Amirul for AMC
Factors/Cause of Middle Ear Block
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• Contributing Factors– Flying with head cold– Flying with a sore throat
Middle Ear Block Treatment
– Yawning or swallowing– Performing “Valsalva”– Nasal sprays – best used prior to descent– Pain medications– For infants / children – provide a bottle / straw to
suck– Ascend to safe altitude where symptoms subside
and then slowly descend
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Middle Ear Block Prevention
• Prevention– DO NOT FLY WITH A HEAD COLD
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2. Sinus
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Sinus
• Sinus is the cavity within a bone, especially in the bones of the face.
FRONTALS
ETHMOIDS
SPHENOID
MAXILLARY
44Presented by Mohd Amirul for AMC
The Sinuses Block• Most often involves frontal sinuses (above each
eyebrow) and maxillary sinuses (both cheeks)• Sinus ducts have openings into the nasal passage• Gas escaped with increases upon ascent most often
without problems• With descent, air moves back out through the ducts
if they are open• If the openings are swollen, a blockage may occur.
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Cause of Sinus Blockage
• Commonly caused by cold (flu) / allergies.
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Symptoms of Sinus Blockage
– Severe pain– Possible referred pain to teeth
47Presented by Mohd Amirul for AMC
Treatment of Sinus Blockage.
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• Treatment– Equalize pressure as quickly as possible– Valsalva is sometimes effective– Ascent to safe altitude then slow descent– Nasal sprays may help
Prevention of Sinus Blockage
• Never fly with the cold/ sinus problem like allergy or under medication of upper respiratory problem.
Presented by Mohd Amirul for AMC 49
3. Teeth
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The Teeth• Air trapped within teeth expands with ascent.• Rarely occur since we’ve modern dentistry nowadays.• Pain often increases with altitude.
51Presented by Mohd Amirul for AMC
• Problem includes:– Cavity• Air trapped inside tooth and can’t escape.
– Abscess • Small pocket of trapped gas at the base/root of teeth• Rarely occur• Dull pain during ascent
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Cont.
Treatment and Prevention
• Treatment– Descent– Pain medications
• Prevention– Good dental hygiene
53Presented by Mohd Amirul for AMC
4. Gastrointestinal Tract
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Gastrointestinal Tract
• Gastrointestinal: related to stomach and intestines
• Most frequently experienced with a rapid ascent (decrease in barometric pressure)
• Symptoms result from gas expansion• Above 25,000 feet distention could be large
enough to produce severe pain– May produce interference with breathing
55Presented by Mohd Amirul for AMC
Gastrointestinal System
56Presented by Mohd Amirul for AMC
Cont.
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Cont.
CausesSources of Gas– Swallowed air (including gum chewing)– Food digestion • Food that can cause excess gas formation:
– Onions– Broccoli– Cabbage– Pumpkin
– Carbonated beverages• CO2 will expand at high altitude.
– Drink large amount of water at open air (e.g. water cooler)
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Treatment– Walking or moving– Belching (burp) or passing gas– Massage the affected area– Loosen restrictive clothing– Use of a gas reducing agent– Descent to a higher pressure
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Prevention
• Avoid consume the food/beverage that can cause access gas formation.
• Drink from the bottle.
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Conclusion• Decompression Sickness: Occurs when gases
(nitrogen) dissolved in body fluids are released as bubbles.
• Trapped Gas: Expanding gases within the body cannot escape to allow the equalization of body pressures.
Presented by Mohd Amirul for AMC 61
Key Points• Henry’s Law• Decompression Sickness• Type of DCS• Factors or Cause Affecting DCS• Treatment of DCS• Prevention of DCS• Trapped Gas• Boyle’s Law• Cavities
62Presented by Mohd Amirul for AMC
End of Presentation #65 Minutes for Q/A session
63Presented by Mohd Amirul for AMC
Quote of the Day
• We have TWO choices in life. DO or NOT DO. Both of these will give the consequences in your future. Think about it=)
Presented by Mohd Amirul for AMC 64
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