AHF 2203AVIATION HUMAN FACTORS

Presentation 5: Hyperventilation and Cabin Pressurization

1

Recapitulate

• Lets recap what we have done last session:– 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

2

Presentation Outline

• Part 1: Hyperventilation

• Part 2: Cabin Pressurization

3

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.

4

Part 1: Hyperventilation

5

• 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?

6

7

What is Breathing???

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.

8

• 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.

9

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.

10

Cont.

What happen to your breathing (slow/fast) when your get into

emotional problem (angry/stress/anxiety/panic)??

11

Cont.

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

12

• 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.

13

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.

14

Cont.

Hyperventilation Process

15

Imagine if the unconsciousnesshappens to the PILOT??

• Hyperventilation rarely painful.

• Many symptoms and sign are similar to hypoxia. So this is the difficulty to recognize Hyperventilation.

16

Cont.

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.

17

• 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.

18

Cont.

• Hyperventilation and Hypoxia can occur simultaneously. This making it difficult to diagnose (analyze) the problem.

19

Cont.

Relation between Hypoxia and Hyperventilation

20

Causes of Hyperventilation

• Main cause of Hyperventilation is

EMOTIONAL PROBLEM

What is emotional problem?Please give the example of emotional problem?

21

22

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

23

Cont.

Symptoms of Hyperventilation • 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.

24

Prevention of Hyperventilation

• Monitor your rate and depth of breathing.

• Learn to recognize stressors that would cause you to over breath.

• Avoid panic.

25

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)

26

• 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.

27

Cont.

Part 2: Cabin Pressurization

28

• 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.

29

Cont.

• Cabin pressurization is the is the active pumping active pumping of of compressed compressed air into an into an aircraft cabin ..

• The The purposepurpose of these systems is to of these systems is to provide a provide a safe and comfortable cabin environment, and safe and comfortable cabin environment, and to protect all cabin occupants from the to protect all cabin occupants from the physiological risks of high altitudes physiological risks of high altitudes (e.g. (e.g. hypoxia, decompression sickness).hypoxia, decompression sickness).

30

Cont.

What is Cabin Pressurization?

• It involves It involves simultaneous control simultaneous control on:on:– TemperatureTemperature– HumidityHumidity– Air CirculationAir Circulation– Cabin PressureCabin Pressure

• Pressurization is essential above 10,000 feetPressurization is essential above 10,000 feet

31

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.

32

Cont.

How Cabin Pressurization Works??

33

Basic Mechanic of Cabin Pressurization System

34

Cont.

• Outside air Outside air continuously continuously enters engineenters engine. . • Air is Air is compressed by the compressor compressed by the compressor in the in the

engine and then engine and then passes through cooling packspasses through cooling packs..• Cool outside air goes into mixing chamberCool outside air goes into mixing chamber and and

mixed with re-circulated air from the tanksmixed with re-circulated air from the tanks..• Air from mixing chamber then continuously Air from mixing chamber then continuously

supplied to the cabinsupplied to the cabin..• Outflow valve Outflow valve then then control the air flow by open control the air flow by open

and close the valve and close the valve to to maintain the suitable maintain the suitable pressure.pressure.

Cont.

35

Cont.

36

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.

37

Disadvantages of Pressurized flight

• Always a chance of

DECOMPRESSION.

38

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

39

Cont.

• THREE major types of decompression:– Slow Decompression– Rapid Decompression– Explosive Decompression

40

Vary with TIME!

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).

41

Cont.

Rapid Decompression

• Total loss of cabin pressurization within 1-10 seconds.

• It happens in case of big air leak.

42

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.

43

Cont.

Qantas Flight Decompression, Big Hole in the Fuselage

Cont.

• 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.

45

Factors AffectingSeverity and Times of Decompression

• 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).

46

Cont.

• 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.

47

Cont.Times of Times of Useful Consciousness Consciousness

48

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

Cont.

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.

• 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.

Cont.

51

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.

52

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.

53

Key Points• 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.

54

End of Presentation #55 Minutes for Q/A session

55

Quiz 1• 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

56