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Environmental Physiology Final > Hypoxia > Flashcards

Hypoxia Flashcards

1
Q

Normoxia

A

Adequate supply of oxygen

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2
Q

Hypoxia

A

Insufficient oxygen to main normal tissue function

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3
Q

Hypoxemia

A

Low levels of oxygen in the arterial blood

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4
Q

Anoxia

A

Absence of oxygen in the blood or tissue

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5
Q

Hypobaric hypoxia

A

Barometric pressure decreases as altitude increases

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6
Q

Normobaric hypoxia

A

Experimentally manipulate fraction of inspired O2 without manipulating barometric pressure

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7
Q

Hypoxic hypoxia

A

Reduction in arterial PO2

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8
Q

Examples of hypoxia hypoxia

A

High altitude
Hyperventilation

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9
Q

Anemic hypoxia

A

Reduction in O2 carrying capacity of the blood

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10
Q

Anemic hypoxia examples

A

Decreased RBC levels (hemorrhage)
Reduced hemoglobin concentration (anemia)
Reduced O2 binding capability of hemoglobin (carbon monoxide inhalation)

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11
Q

Circulatory hypoxia

A

Decreased blood flow to tissues

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12
Q

Circulatory hypoxia examples

A

Heart failure
Local vasoconstriction (cold)

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13
Q

Histotoxic hypoxia

A

Inability of tissues to use distribution of electron transport chain in mitochondira

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14
Q

Histotoxic hypoxia examples

A

Cyanide poisoning

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15
Q

PIO2 equation

A

(PB- 47mmHg) x 0.2093

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16
Q

Alveolar gas equation

A

(PAO2 - (PACO2/R) + F

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17
Q

Alveolar ventilation equation

A

VCO2/ PACO2 x 0.863

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18
Q

Flow equation

A

Pressure x conductance

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19
Q

Cardiac output equation

A

MAP x Vascular conductance
MAP/ vascular resistance

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20
Q

MAP equation

A

Cardiac output x vascular resistance

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21
Q

What causes vasodilation?

A

Hypoxia

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22
Q

What causes vasoconstriction?

A

Increased sympathetic nerve activity

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23
Q

What decreases vascular resistance?

A

Hypoxia-mediated vasodilation stimulated by arterial O2

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24
Q

What increases vascular resistance?

A

Sympathetically mediated vasoconstriction stimulated by arterial PO2

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25
Q

Pulmonary Vascular Physiological Responses

A

Hypoxic pulmonary vasoconstriction
Increase pulmonary artery pressure

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26
Q

High-altitude Pulmonary Edema

A

Pulmonary vasoconstriction
Pressure induced leak
Pulmonary edema
Clinical features of HAPE

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27
Q

What counteracts reduced O2 in hypoxia?

A

Greater ease of O2 offloading from Hb (smaller pressure gradient required to release O2)

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28
Q

Neurological responses to hypoxia

A

Hyperventilation
Brain blood flow is altered
Reduced tissue PO2 and decreased cerebral oxygenation (accelerates supraspinal fatigue)

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29
Q

Hyperventilation and hypocapnia relationship

A

Hyperventilation causes hypocapnia and decreases PACO2

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30
Q

Hypercapnia causes

A

Cerebrovascular vasodilation

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31
Q

Hypocapnia causes

A

Cerebrovascular vasoconstriction

32
Q

Determinants of physiological responses to hypoxia

A

Degree of hypoxia
Individual variability
Physical activity
Temperature
Illness/disease
Drugs

33
Q

Describe the first demonstration of the dangers of rapid high-altitude ascent

A

Zenith balloon ascent
Reached an altitude of 28,000 feet (8600 meters). Two never regained consciousness and died during, one survived to write about it but became deaf.

34
Q

Why study hypoxia?

A

Aviation physiology
Military (airforce, navy)
Tourism
Railway and highway mountain passes
Rescue at high altitude
Shift work (mining, observations/telescopes)

35
Q

How many people live at high altitude?

A

> 1500m - greater than 500 million
2500m - greater than 83 million
3500m - greater than 14 million

36
Q

Where has most high altitude research been done?

A

Climbing
Aviation
Male researchers testing each other
Women deemed “distractions” and high-altitude residents as “unintelligent”

37
Q

Acclimatization

A

Physiological adjustments derived from exposure to a natural environment

38
Q

Decrease in PAO2 causes?

A

Carotid body - increase ventilation - decrease PACO2 - back to beginning

39
Q

What is essential for normal respiratory acclimatization?

A

Peripheral chemoreceptors (Carotid bodies)

Animals who have had their carotid bodies denervated fail to acclimatize properly (similar to humans with unilateral and/or bilateral resection of their carotid bodies)

40
Q

Ventilatory response to exercise

A

Larger ventilatory response causes increase in climbing performance (however, there is a trade off at extreme altitude)

41
Q

The most successful climbers had what response to hypoxia?

A

Smaller responses - because of lowered HVR, their ventilatory efficiency was higher.

42
Q

Describe the trade off of high HVR

A

Useful at moderate altitudes, but at extreme altitudes the metabolic cost of excessive breathing is counterproductive.

43
Q

Describe the ventilation process

A

Ventilation - pulmonary O2 diffusion - circulatory O2 delivery - muscle O2 diffusion - muscle O2 utilization - muscle ATP turnover

44
Q

Alveolar to arterial PO2 causes

A

Thickening of the diffusion barrier, decrease in the surface area, breathing low O2 mix

45
Q

Circulation changes with altitude

A

Cerebral circulation increases CBF on initial exposure
Hypoxic pulmonary vasoconstriction
Increased sympathetic outflow
Increased heart rate
Reduced stroke volume (due to reduced blood volume)

46
Q

How many people does acute mountain sickness affect?

A

Up to 25% travellers to 2500m and 75% with rapid ascent to 5000m

47
Q

When does AMS occur?

A

Within 6-48 hours of ascent

48
Q

Symptoms of AMS

A

Headache and one of:
Malaise
Nausea
Vomitting
Anorexia
Light headedness/dizziness

49
Q

What causes AMS?

A

Increase in intracranial pressure

50
Q

How to minimize risk of AMS?

A

Slow, gradual ascent (let yourself acclimatize); no more than 300m higher/night above 3000m
Acetazolamide (diamox)

51
Q

Acetazolamide effects

A

Produces metabolic acidosis and stimulates ventilation

52
Q

What causes high-altitude cerebral edema?

A

Increased intracranial pressure

53
Q

When does high-atltitude cerebral edema occur?

A

1-2 days after onset of AMS symptoms

54
Q

Symptoms of high-altitude cerebral edema

A

Impaired level of consciousness
Hallucinations
Swelling of optic disk

55
Q

Treatment for high-altitude cerebral edema

A

Medications (dexamethasone)
O2
Descent

56
Q

When does high-altitude pulmonary edema occur?

A

24-72 hours after rapid ascent

57
Q

Symptoms of high-altitude pulmonary edema

A

Breathlessness
Cough
Lung crackles

58
Q

Treatment of high-altitude pulmonary edema

A

O2
Medications
Descent

59
Q

High-altitude pulmonary edema impairs what?

A

Diffusion from alveoli to capillary

60
Q

Function of the gamow bag

A

Generates internall pressure using 10-15 pumps/minute (2-3 with CO2 bladder)

61
Q

How long must gamow bag be used?

A

1-2 hours for minimal treatment for AMS
4 hours for HAPE
6 hours for HACE

62
Q

Aids to acclimatization

A

Climb high, sleep low
High carbohydrate diet
Guides pace - avoid overexertion
Avoid alcohol and sleeping medications
Pre-acclimatization strategies

63
Q

The highest city in the world

A

La Rinconada

64
Q

Arterial O2 content equation

A

Increased [Hb] x O2 saturation + dissolved O2

65
Q

How many people does chronic mountain sickness effect?

A

~5-20% of high-altitude residents (Andean)

66
Q

Chronic mountain sickness causes

A

Excessive erythrocytosis (Hb > 21)
Increased cardio and cerebral vascular risk

67
Q

Outcomes from excessive erythrocytosis and chronic mountain sickness

A

Pulmonary hypertension
Right heart failure
Neurological problems
Increased cardiovascular risk
Mortality

68
Q

Treatment for chronic mountain sickness

A

Descent (not always possible)
Bloodletting
Acetazolamide
Drugs that lower blood viscosity

69
Q

Why is bloodletting not preffered?

A

RBC production can bounce back even worse than before

70
Q

Describe benefits of the tibetan advantage compared to lowlanders

A

More effective breathing pattern
Increased lung diffusion capacity
Some cardiac and brain adaptations
Higher capillary density
Greater mitochondria

71
Q

Describe “unairness” of olympic events

A

Western countries objected to “Training advantages” of Kenyans and Ethiopians (were competing and winning in international distance running)

Most people couldn’t spend >4-6 weeks at altitude

72
Q

Why altitude train?

A

Erogenic benefit of acclimatization
Hypoxic exercise > normoxic exercise
Variety (added stressor to boost ceiling in elite athletes)

73
Q

Correlation and causation relationship

A

Correlation DOES NOT equal causation

74
Q

VO2 max exercise at altitude

A

VO2 max remains reduced at high altitude, as well as reduced max cardiac output (reduced max heart rate and stroke volume)

75
Q

Live high-train high

A

Acclimatization and hypoxic exercise

76
Q

Live high - train low

A

Acclimatization

Environmental Physiology Final (5 decks)

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