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ATPL Theory - Module 1 > Human Performance - Hypoxia, Hyperventilation, Acceleration > Flashcards

Human Performance - Hypoxia, Hyperventilation, Acceleration Flashcards

1
Q

What is hypoxia?

A

Hypoxia is a shortage of oxygen.

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2
Q

What is anoxia?

A

Anoxia is a total absence of oxygen supply to an organ’s tissues.

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3
Q

What is hypoxic hypoxia?

A

Hypoxic hypoxia is a reduction in oxygen supply related to aviation and altitude.

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4
Q

What determines the amount of oxyhaemoglobin in the blood?

A

The amount of oxyhaemoglobin in the blood depends on the amount of oxygen in the lungs.

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5
Q

How can the amount of oxygen in the air be described?

A

The amount of oxygen in the air can be described as its partial pressure in mm Hg (millimetres of mercury).

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6
Q

What is the standard atmospheric pressure at sea level?

A

The standard atmospheric pressure at sea level is 760 mm Hg.

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7
Q

What is the partial pressure of oxygen at sea level?

A

The partial pressure of oxygen at sea level is 160 mm Hg.

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8
Q

How does altitude affect the partial pressure of oxygen in the atmosphere?

A

As altitude increases, the partial pressure of oxygen in the atmosphere falls.

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9
Q

What gases make up the atmosphere and their percentages?

A

The atmosphere is made up of 78% nitrogen, 21% oxygen, 0.9% argon, 0.1% carbon dioxide, moisture, solid particles, and traces of other gases.

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10
Q

What is the partial pressure of oxygen in the lungs at sea level?

A

At sea level, the partial pressure of oxygen in the lungs is 103 mm Hg.

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11
Q

What happens to the partial pressure of oxygen in the atmosphere as altitude increases?

A

It falls, but the proportion of oxygen in the atmosphere remains the same.

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12
Q

How does altitude affect the partial pressure of water vapour and carbon dioxide in the lungs?

A

The partial pressure of water vapour and carbon dioxide remains the same

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13
Q

What is the reaction threshold for hypoxia and its effects?

A

The reaction threshold is at 7000 ft, where night vision adaptation is affected, and a reaction to lower oxygen saturation is detected.

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14
Q

What is the disturbance threshold for hypoxia and its effects?

A

The disturbance threshold is at 10-12000 ft, where significantly lower oxygen levels impair judgement, memory, and alertness.

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15
Q

What is the critical threshold for hypoxia and its effects?

A

The critical threshold is at 22000 ft, where oxygen saturation falls to 65-60%, causing extreme dizziness, confusion, and total loss of consciousness.

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16
Q

What should you not do above 10,000 ft cabin height?

A

Do not operate above 10,000 ft cabin height without oxygen.

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17
Q

What is necessary to keep the partial pressure of oxygen in the lungs adequate above 10,000 ft?

A

It is necessary to increase the proportion of oxygen supplied to the lungs gradually up to 100% oxygen at 33,700-40,000 ft.

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18
Q

What must be done above 40,000 ft when 100% oxygen alone is insufficient?

A

Oxygen must be supplied under pressure to the oxygen mask, involving pressure breathing.

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19
Q

How is normal breathing reversed during pressure breathing?

A

Oxygen rushes into the lungs under pressure when the mouth is opened, and it must be exhaled by force.

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20
Q

What does the oxygen dissociation curve show?

A

It shows that as altitude increases, alveolar partial pressure is reduced, and oxygen saturations decrease.

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21
Q

What are ‘equivalent altitudes’?

A

Equivalent altitudes refer to the differences between breathing air compared to 100% oxygen at various altitudes.

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22
Q

What happens if the oxygen supply system fails?

A

The normal reaction to lack of oxygen, panting, does not appear because there is no excess of carbon dioxide.

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23
Q

Why is hypoxia insidious?

A

It can be recognized only by being very aware of the symptoms, similar to carbon monoxide poisoning.

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24
Q

What are the symptoms of hypoxia?

A

Difficulty in concentrating, degradation of reasoning and perceptive functions, impaired judgement, mood changes, euphoria, drowsiness, lightheadedness, dizziness, nausea, lethargy, loss of muscular coordination, pallor, cyanosis, failure of basic senses, unconsciousness, coma, and death.

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25
Q

Which senses are affected above 5,000 ft due to hypoxia?

A

Colour vision and other basic senses.

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26
Q

What feelings induced by hypoxia are dangerous for pilots flying solo?

A

Euphoria.

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27
Q

What factors can hasten the onset of hypoxia?

A

Exercise, cold, illness, fatigue, use of drugs (including alcohol), and smoking.

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28
Q

How does smoking affect hypoxia?

A

Smoking leads to inhalation of carbon monoxide, which binds to haemoglobin blocking oxygen transfer, raising physiological altitude by 4-5 thousand feet.

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29
Q

At what altitude can a heavy smoker become hypoxic?

A

6,000 ft.

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30
Q

How does cold affect the body’s demand for oxygen?

A

Cold increases the body’s demand for oxygen to generate heat by burning carbohydrates.

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31
Q

Why does hypoxia not lead to a shortage of breath?

A

Because the body may be short of oxygen, but there is no excess of carbon dioxide.

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32
Q

At what altitude may euphoria be experienced due to hypoxia?

A

Above 10,000 ft.

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33
Q

At what altitude is night vision affected due to hypoxia?

A

Above 5,000 ft.

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34
Q

What is the Time of Useful Consciousness (TUC)?

A

TUC is the length of time during which an individual can act with both mental and physical efficiency and alertness.

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35
Q

How is TUC measured?

A

TUC is measured from the moment an individual is exposed to hypoxia.

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36
Q

How does TUC vary with altitude?

A

TUC decreases as altitude increases.

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37
Q

What is the TUC for a person seated at 20,000 ft?

A

30 minutes.

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38
Q

What is the TUC for a person moderately active at 20,000 ft?

A

5 minutes.

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39
Q

What is the TUC for a person seated at 30,000 ft?

A

1-2 minutes.

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40
Q

What is Effective Performance Time (EPT)?

A

EPT refers to the pilot’s ability to function effectively regardless of consciousness.

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41
Q

How does EPT compare to TUC?

A

EPT is always within and shorter than TUC.

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42
Q

What is the approximate EPT at 40,000 ft?

A

Around 5-6 seconds.

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43
Q

How does cabin altitude between 7,000 and 8,000 ft affect TUC?

A

It halves the tabulated values of TUC.

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44
Q

Why should aircrew avoid giving blood before duty?

A

Because blood donors increase their susceptibility to hypoxia.

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45
Q

What can trigger hyperventilation?

A

Psychological reasons such as stress and anxiety, or physiological reasons like a reaction to vibration, heat, and high acceleration.

46
Q

What are the symptoms of hyperventilation?

A

Dizziness, tingling of the extremities, visual disturbances, hot and cold flushes, anxiety, impaired performance, loss of consciousness.

47
Q

What can severe hyperventilation lead to?

A

Severe muscle contractions known as carpopedal spasms, which can become fixed contractions (tetany) if unconsciousness occurs.

48
Q

How is hyperventilation largely self-correcting?

A

The ultimate symptom is to lose consciousness, at which point the body’s automatic controls take over to restore normality.

49
Q

What should be done if there is doubt about whether a person is experiencing hypoxia or hyperventilation?

A

Treat for hypoxia.

50
Q

What happens if hypoxia is untreated?

A

It can kill.

51
Q

What happens if hyperventilation is untreated?

A

It leads to a short period of unconsciousness.

52
Q

How can symptoms of hyperventilation be controlled?

A

By reducing the rate and depth of breathing.

53
Q

What is a recommended treatment for hyperventilation?

A

Breathing into and inhaling from a paper bag to increase carbon dioxide in the lungs.

54
Q

What additional measures can help with hyperventilation?

A

Closing one opening of the nose and speaking loudly.

55
Q

How can hypoxia and hyperventilation be distinguished?

A

Hypoxia and hyperventilation are difficult to distinguish.

56
Q

What is an early symptom of hyperventilation?

A

Dizziness.

57
Q

What is a symptom of hypoxia but not of hyperventilation?

A

Cyanosis.

58
Q

What is the recommended treatment if there is any doubt about the diagnosis between hypoxia and hyperventilation?

A

Select 100% oxygen and descend below 10,000 ft.

59
Q

What causes anaemic hypoxia?

A

Anaemic hypoxia is caused by a lack of oxygen-carrying capacity due to blood loss, decreased haemoglobin, or altered haemoglobin.

60
Q

Why should a pilot not fly immediately after donating blood?

A

Because there will be less haemoglobin in their system, leading to less oxygen available to the brain.

61
Q

How can smoking cause anaemic hypoxia?

A

Smoking causes carbon monoxide to bind to haemoglobin much stronger than oxygen, approximately 200 times stronger.

62
Q

What is circulatory shock?

A

Circulatory shock is a failure of the blood supply, such as from a heart attack.

63
Q

What is histotoxic hypoxia?

A

Histotoxic hypoxia occurs at a cellular level where the cell is impaired and cannot use oxygen, often caused by narcotics or drugs.

64
Q

What causes decompression sickness?

A

Decompression sickness is caused by dissolved gases, particularly nitrogen, forming bubbles in the blood at high altitudes.

65
Q

When can decompression sickness occur?

A

It can occur even when the oxygen supply is adequate and may appear some time after the flight is complete.

66
Q

What are the symptoms of decompression sickness?

A

Symptoms include the bends (joint pain), the creeps (skin itching and rash), the chokes (chest pain and cough), partial loss of vision, paralysis of limbs, and the staggers (collapse and unconsciousness).

67
Q

What law applies to decompression sickness?

A

Henry’s law applies to decompression sickness.

68
Q

Can decompression sickness occur if the oxygen supply is adequate?

A

Yes, it can occur even if the oxygen supply is adequate.

69
Q

At what cabin altitudes is decompression sickness unlikely?

A

Below 18,000 ft.

70
Q

At what cabin altitudes is decompression sickness rare?

A

Below 25,000 ft.

71
Q

What altitude can a fit and healthy non-smoker comfortably exist at?

A

Up to 10,000 ft.

72
Q

Why do most airliners fly with a cabin pressurized to give an equivalent of 6000-8000 ft?

A

To cater for the less fit, smokers, elderly passengers, or those with respiratory illnesses.

73
Q

What exacerbates decompression sickness?

A

High altitudes, duration of exposure, age, excess body weight, and recent diving activity.

74
Q

How long are pilots prohibited from flying after scuba diving?

A

24 hours.

75
Q

What should be done when symptoms of decompression sickness occur in flight?

A

Descend to the lowest possible level and land as soon as possible.

76
Q

What is the treatment for decompression sickness?

A

Place the casualty in a compression chamber on 100% oxygen and keep warm.

77
Q

What should you do if you suffer rapid decompression without symptoms of decompression sickness?

A

Seek prompt aeromedical advice before flying again.

78
Q

What causes the bends?

A

Gas bubbles in the joints.

79
Q

What should be done first if pressurization is lost?

A

Don oxygen masks and select 100% oxygen.

80
Q

What should the aircraft do after pressurization is lost?

A

Rapid and controlled descent to at least 10,000 ft cabin altitude.

81
Q

What additional precautions should be taken if it’s impossible to descend to a lower altitude?

A

Be alert for symptoms of decompression sickness.

82
Q

How can rapid decompression affect cabin altitude compared to actual altitude?

A

It may lead to a cabin altitude as much as 5000 ft higher than the actual altitude.

83
Q

What can occasionally cause lung damage during rapid depressurization?

A

Rapid depressurization itself, which can be avoided by breathing out during the process.

84
Q

How long should the crew avoid flying after experiencing a pressurization loss event?

A

A minimum of 24 hours.

85
Q

What is the immediate action sequence for loss of pressurization?

A

Get on oxygen first, then start an emergency descent and land as soon as possible.

86
Q

How is the direction of action of linear acceleration described?

A

Using a three-axis system based on the alignment of the human spine: x-axis (fore and aft), y-axis (lateral), and z-axis (vertical).

87
Q

What does +Gz represent in terms of acceleration?

A

Acceleration up.

88
Q

What does +Gx represent in terms of acceleration?

A

Acceleration forward.

89
Q

What does +Gy represent in terms of acceleration?

A

Acceleration to the right.

90
Q

What does -Gz represent in terms of acceleration?

A

Acceleration down.

91
Q

What does -Gx represent in terms of acceleration?

A

Acceleration back.

92
Q

What does -Gy represent in terms of acceleration?

A

Acceleration to the left.

93
Q

How much G can the body tolerate in the vertical axis for short term exposure?

A

Up to 25 G in the vertical axis (+25 Gz) and 45 G in the fore/aft axis.

94
Q

What happens when forces exceed +1 Gz?

A

The blood is driven to the lower part of the body, especially the legs.

95
Q

What effects are caused by forces approaching +3.5 Gz?

A

Lack of blood to the eyes and brain, causing ‘greying out’ of vision, tunnel vision, loss of peripheral vision, and ultimately blackout and unconsciousness.

96
Q

How can the effects of high G be delayed?

A

Clamping the leg and stomach muscles can delay the onset of loss of vision and unconsciousness to 7 or 8 G.

97
Q

What equipment helps military pilots tolerate high G forces?

A

Anti-G trousers that are inflated with bleed air to pressurize the legs under G. Some fighter aircraft have a reclined seat position.

98
Q

How does physical stature affect G tolerance?

A

Tall people are more susceptible to G forces than short people.

99
Q

What factors reduce tolerance of high G environments?

A

Hypoxia, hyperventilation, smoking, low blood sugar, heat, and alcohol consumption.

100
Q

How does the body react to negative G forces?

A

Negative G forces increase blood pressure in the head and brain, causing facial pain, bursting small blood vessels in the face, and ‘red out’ of vision.

101
Q

How are accelerations classified for duration?

A

Into ‘long duration’ (more than one second) and ‘short duration’ (less than one second, essentially impact acceleration forces).

102
Q

Who can tolerate more vertical G, short people or tall people?

A

Short people can tolerate more vertical G.

103
Q

How common is negative G in normal flight and how does the body tolerate it?

A

Negative G occurs more rarely and the body is less tolerant to it.

104
Q

How can the onset of loss of vision and unconsciousness from high G be delayed?

A

By clamping the leg and stomach muscles, which can delay the onset to 7 or 8 G.

105
Q

What equipment helps military pilots tolerate high G forces?

A

Anti-G trousers that are inflated with bleed air to pressurize the legs under G. Some fighter aircraft have a reclined seat position.

106
Q

How does physical stature affect G tolerance?

A

Tall people are more susceptible to G forces than short people.

107
Q

What factors reduce tolerance of high G environments?

A

Hypoxia, hyperventilation, smoking, low blood sugar, heat, and alcohol consumption.

108
Q

How does the body react to negative G forces?

A

Negative G forces increase blood pressure in the head and brain, causing facial pain, bursting small blood vessels in the face, and ‘red out’ of vision.

109
Q

How are accelerations classified for duration?

A

Into ‘long duration’ (more than one second) and ‘short duration’ (less than one second, essentially impact acceleration forces).

110
Q

Who can tolerate more vertical G, short people or tall people?

A

Short people can tolerate more vertical G.

111
Q

How common is negative G in normal flight and how does the body tolerate it?

A

Negative G occurs more rarely and the body is less tolerant to it.

ATPL Theory - Module 1 (17 decks)

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