AHF 2203 AVIATION HUMAN FACTORS Presentation 6: Decompression Sickness and Trapped Gas 1Presented by Mohd Amirul for AMC

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.


Presentation Outline

• Part 1: Decompression Sickness

• Part 2: Trapped Gas


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


Part 1: Decompression Sickness (DCS)

Presented by Mohd Amirul for AMC 5

• 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


Henry’s Law IllustrationHenry’s Law Illustration

Low pressure equilibriumLow concentration

Double the pressure equilibriumDouble the concentration


• 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:


• 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.


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.


• 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.


Cont.

Types of DCS

• FOUR types of DCS:• Type I (Non-Serious)– Bends– Skin Manifestations

• Type II (Serious)– Chokes– Neurological Manisfestations


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)


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


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).


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.


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


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.


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.


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


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


Prevention of DCS

• Protective measures include: – Cabin pressurization. – Limitation of time at high altitude.


Part 2: Trapped Gas


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.


*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.


Cont.

• Boyle’s law application to human body:


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.


• Our body cavities that often experienced trapped gas are:1. Middle ear2. Sinuses3. Teeth4. Stomach & Intestines (Gastrointestinal tract)


Cont.

1. Middle Ear

FRONTALS

ETHMOIDS

SPHENOID

MAXILLARY

2. Sinus

4. Stomach and Intestines

3. Teeth

Cont.


1. The Middle Ear


Anatomy of EarCont.


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.

Presented by Mohd Amirul for AMC

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.


• 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.


Middle Ear BlockCont.


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


*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


Factors/Cause of Middle Ear Block


• 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



Middle Ear Block Prevention

• Prevention– DO NOT FLY WITH A HEAD COLD


2. Sinus


Sinus

• Sinus is the cavity within a bone, especially in the bones of the face.

FRONTALS

ETHMOIDS

SPHENOID

MAXILLARY


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.


Cause of Sinus Blockage

• Commonly caused by cold (flu) / allergies.


Symptoms of Sinus Blockage

– Severe pain– Possible referred pain to teeth


Treatment of Sinus Blockage.


• 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.


3. Teeth


The Teeth• Air trapped within teeth expands with ascent.• Rarely occur since we’ve modern dentistry nowadays.• Pain often increases with altitude.


• 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


Cont.

Treatment and Prevention

• Treatment– Descent– Pain medications

• Prevention– Good dental hygiene


4. Gastrointestinal Tract


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


Gastrointestinal System


Cont.


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)


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


Prevention

• Avoid consume the food/beverage that can cause access gas formation.

• Drink from the bottle.


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.


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


End of Presentation #65 Minutes for Q/A session


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=)


Documents

AHF 2203 AVIATION HUMAN FACTORS Presentation 6: Decompression Sickness and Trapped Gas 1Presented by Mohd Amirul for AMC