AHF 2203
AVIATION HUMAN FACTORS
Presentation 5: Hyperventilation and
Cabin Pressurization
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Recapitulate
• Lets recap what we have done last session:
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Atmospheric Layer
Variation of pressure and temperature with altitude
Physiological zone of atmosphere
Definition of Hypoxia
Physiological Process of Hypoxia
Types of Hypoxia
Stage of Hypoxia
Sign and symptoms of Hypoxia
Prevention and Correction of Hypoxia
EPT
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Presentation Outline
• Part 1: Hyperventilation
• Part 2: Cabin Pressurization
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Learning Outcomes
• At the end of this session, student should be
able to:
– Identify and aware of Hyperventilation syndromes
and their causes, effects, preventions and medical
cure needed especially during flight.
– Understand why aircraft cabin need to be
pressurized especially at higher altitude.
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Part 1: Hyperventilation
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• How do you breathing?
• Why do you breathing?
• What gases do you consume during
breathing?
• What happen if you are stopped
breathing?
• Which one comfortable for you: Slow
breathing? Rapid breathing?
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What is Breathing???
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Cont.
• Breathing: Process of taking air (O2)into the
lung and exchanging gas (CO2)to the
environment.
• CO2 is the gas produce by all living things as a
WASTE PRODUCT.
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Cont.
• It is important for maintaining chemical
balance in the body and control our breathing.
• Access CO2 is eliminated by the lung during
isolation (separation).
• However, some amount of CO2 must remain
in the body – to maintain chemical balance in
the body.
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Cont.
• The concentration of gases in the body
controlled by BRAIN.
• Average adult breathing cycle: 12-16 breath
per minute.
• Rate of breathing can be rapid/slow down.
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Cont.
What happen to your breathing
(slow/fast) when your get into
emotional problem
(angry/stress/anxiety/panic)??
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Hyperventilation
• Hyperventilation (overbreathing) can be defineed
as excessive rate and depth of respiration leading
to abnormal loss of CO2 from the blood.
• It causes the excessive loss of CO2 from the
blood.
• This results to degrade the chemical balance in
the blood
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Cont.
• The brain will react by restricting the blood
flow.
• By this restriction, the blood flow to the brain
cause (result of Hyperventilation):
– Poor judgment
– Impaired memory
– Performance impairment
– Late of reaction time
– Muscle coordination.
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Cont.
• If this chemical imbalance continue (not
quickly cured) it might result:
UNCONCIOUSNESS!!!
• With the breath held the carbon dioxide levels
build up once more and the symptoms
disappear in reverse order.
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Hyperventilation Process
Increase in rate and
depth of breathing
Imagine if the
unconsciousness
happens to the
PILOT??
Excessive loss of CO2
Unconsciousness
(if chemical
imbalance continue)
Chemical Imbalance
Brain restrict the
blood flow
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Cont.
• Hyperventilation rarely painful.
• Many symptoms and sign are similar to
hypoxia. So this is the difficulty to recognize
Hyperventilation.
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Difference between Hypoxia and
Hyperventilation
Hyperventilation
– Skin may look pale.
– As we ascend, it can
occur slowly and
gradually over time.
– Muscle activity might
becomes spastic
Hypoxia
– Skin may look blue
(cyanosis).
– Can occur rapidly.
– Muscle soft and limp
with little or no
activity.
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Cont.
• To help differentiate between
Hyperventilation and Hypoxia please monitor
this element:
– Flight attitude
– Cabin altitude (if pressurized)
– Oxygen system (if in use)
– Emotional state
– Awareness of your current flight environment.
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Cont.
• Hyperventilation and Hypoxia can occur
simultaneously. This making it difficult to
diagnose (analyze) the problem.
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Relation between Hypoxia and
Hyperventilation
Hypoxia: lack of oxygen in blood
Body attempt to circulate more
oxygen.
Increase heart and respiratory rate
Tend to breath rapidly caused
Hyperventilation
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Causes of Hyperventilation
• Main cause of Hyperventilation is
EMOTIONAL PROBLEM
What is emotional problem?
Please give the example of emotional problem?
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Cont.
Anger
Fear
Anxiety
Panic
Emotional
Problem
Stress
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Cont.
• Other causes of Hyperventilation that not caused
by emotional problem:
– Pain
– Bleeding
– Cardiac disease, such as congestive heart failure
(abnormal collection of blood) or heart attack
– Drugs (such as an aspirin overdose)
– Respiratory disease: Infection such as pneumonia
(infection of one or both lungs which is usually caused
by bacteria, viruses, or fungi) or sepsis (toxins in the
blood or tissues)
– Lung disease such as asthma,
– Pregnancy
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Symptoms of Hyperventilation
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Dizziness
Lightheadedness
Blurred Vision
Numbness
Tingling
Hot and cold sensations.
Muscle incoordination (cramps).
Shortness of breath
Unconsciousness
*These symptoms also can be symptoms of Hypoxia
* If you have hyperventilation syndrome, you might not be aware you are breathing
fast. You might be aware of those symptoms above.
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Prevention of Hyperventilation
• Monitor your rate and depth of breathing.
• Learn to recognize stressors that would cause
you to over breath.
• Avoid panic.
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Treatment of Hyperventilation
• FAA Checklist (usually when occur
simultaneously with hypoxia):
– Wear Oxygen Mask
– Check the oxygen regulator is turned on
– Check all connection are secure
– Slow down your breathing rate and depth
– Descend to suitable altitude (10000 ft and below)
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Cont.
• Other treatment:
– Best method is to voluntarily reduce rate of
breathing (Normal rate is 12-16 breaths per
minute)
– Go to 100% O2 (if available)
– Talk or sing (to increase CO2 level)
– Breathing into a bag.
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Part 2: Cabin Pressurization
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Cont.
• Pressure is decrease when altitude is increase.
• Outside pressure (atmospheric pressure)
could be harmful in the high altitude to
human body.
• So to maintain pressurization in the cabin at
high altitude is important.
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Cont.
What is Cabin Pressurization?
• Cabin pressurization is the active pumping of
compressed air into an aircraft cabin .
• The purpose of these systems is to provide a
safe and comfortable cabin environment, and
to protect all cabin occupants from the
physiological risks of high altitudes (e.g.
hypoxia, decompression sickness).
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Cont.
• It involves simultaneous control on:
– Temperature
– Humidity
– Air Circulation
– Cabin Pressure
• Pressurization is essential above 10,000 feet
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Cont.
• Most pressurize aircraft today cruise at
altitude of 25000 ft - 51000 ft while keeping
cabin at comfortable pressurize altitude as in
6500 ft - 8000 ft.
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How Cabin Pressurization Works??
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Cont.
Basic Mechanic of Cabin
Pressurization System
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Cont.
• Outside air continuously enters engine.
• Air is compressed by the compressor in the
engine and then passes through cooling packs.
• Cool outside air goes into mixing chamber and
mixed with re-circulated air from the tanks.
• Air from mixing chamber then continuously
supplied to the cabin.
• Outflow valve then control the air flow by open
and close the valve to maintain the suitable
pressure.
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Cont.
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Advantage of Pressurized Flight
• Oxygen mask no need to be worn
• Risk of decompression sickness minimized
– Decompression sickness caused by nitrogen
forming as bubbles in the blood
• Less noise and vibration during flight.
• Better control of temperature and air
ventilation (system supply fresh air) .
• Fewer trapped gas problem.
– The gas can’t be released especially by our body
cavities part.
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Disadvantages of Pressurized flight
• Always a chance of
DECOMPRESSION.
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Cont.
What is Decompression??
• Decompression means aircraft loss of cabin
pressurization.
• It can occur because cabin pressurization
system not functioning well, the damage to
the aircraft that causes a break in the aircraft
structure which enabling cabin air to escape
outside the aircraft
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Cont.
• THREE major types of decompression:
– Slow Decompression
– Rapid Decompression
– Explosive Decompression
Vary with TIME!
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Cont.
Slow Decompression
• When the cabin loss pressure greater than 10
seconds.
• It happens in case of a small air leak.
• Potential to be most dangerous types of
decompression when unaware cabin altitude
is going up (since it happen very slow).
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Cont.
Rapid Decompression
• Total loss of cabin pressurization within 1-10
seconds.
• It happens in case of big air leak.
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Cont.
Explosive Decompression
• When cabin pressurization loss in less than 1
second!!!
• This rapid change can occur faster than our
lungs can decompress. Lung damage possible
to occur.
• It happens in case of big air leak.
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Cont.
Qantas Flight Decompression, Big Hole in
the Fuselage
Factors Affecting
Severity and Times of Decompression
• Size of cabin
– the larger the cabin, the longer the
decompression time (slower decompression)
• Size of the opening (air leak)
– the larger the opening, the faster the
decompression time.
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Cont.
• Differential ratio
– the greater the pressure differential between the
cabin pressure and the external environmental
pressure, the more forceful the decompression.
• Flight altitude
– higher altitudes create greater threats for
physiological consequences (see *Time of useful
Consciousness (TUC))
*TUC also known as Effective Performance Time (EPT).
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Cont.
Times of Useful Consciousness
• TUC or EPT is the period of time that a pilot has from the time
oxygen become less available until the time when he or she
loses the ability to recognize and take action
• If someone goes beyond TUC, then he or she isn’t even aware
of the problem and will not take corrective action
• The keyword is EFFECTIVE or USEFUL (He or she might be
conscious but not making expected useful or effective
decision).
• TUC decrease as altitude increases.
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Cont.
Altitude
Conscious time
20000
5 – 12 minutes
25000
2 – 3 minutes
30000
45 – 75 seconds
35000
30 – 60 seconds
40000
10 – 30 seconds
45000
12 – 15 seconds
50000+
12 or less seconds
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Effects of Decompression
• Physical effects :
– Noise:
• Noise from decompression can increasing to very loud explosive
sound.
• Communication can be disturbed.
– Fog:
• Form when decreasing in temperature and pressure associated with
decompression
• Effect visual problem
– Flying Debris (dust/dirt)
• Dust and dirt cause visual problem.
– Cooler Temperature
• Pressure or air departs the cabin
• Hypothermia (abnormal body temperature) can occur.
Cont.
• Physiological effect:
– Trapped Gas
• The gas can’t be released especially by our body cavities
(hole) part (e.g. middle ear, teeth etc.)
• Certain gases that will expand with decreasing in
pressure
– Decompression sickness
• Occur due to nitrogen in the body coming out as solution
and forming bubble.
– Hypothermia
• Cause by cooler temperature at high altitude
Cont.
– Hypoxia
• Caused by rapid decreasing in partial pressure of
oxygen
• Lead to deficiency of oxygen in blood
– Hyperventilation
• The emergency could increase rate and depth of
breathing causing hyperventilation.
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Oxygen Systems
• Portable Oxygen Cylinders
• Oxygen cylinders are located throughout the
cabin. The number and location of the oxygen
cylinders varies, depending on the aircraft
cabin configuration.
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Conclusion
• Hyperventilation: rapid rate of respiration that
may lead to the excessive loss of carbon
dioxide from the lung.
• Cabin pressurization is a convenience mean in
control the some of the hazard for human
body in high altitude flight.
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Key Points
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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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End of Presentation #5
5 Minutes for Q/A session
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Quiz 1
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Define physiology and flight physiology
Give 3 main component in human body system
State the main function of brain, lung and heart.
What is the variation of pressure and temperature
with altitude?
• Name TWO physiological zones in atmosphere.
• Define Hypoxia
Duration: 30 minutes
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