High Altitude Physiology And Aviation - Dr. Miyake

Question 1

Mountain climbers and deep sea divers know the profound effects of __________ on human physiology.

Answer 1

Barometric pressure

Question 2

Astronauts learn how physically equivalent forces of ________ and _________ affect the body.

Answer 2

Gravity and acceleration

Question 3

As we ascend to higher and higher altitude, it has become more important to understand the effects of _______ and ________ on the human body.

Answer 3

Altitude

Low gas pressures

Question 4

Barometric pressure (mmHg) at sea level 0

Answer 4

760 mmHg

Question 5

As barometric pressure decreases, the atmospheric O2 partial pressure ___________ proportionately remaining at all times slightly <21% of totsl barometric pressure.

Answer 5

Decreases

Question 6

Basic cause of all hypoxia problems in high-altitude physiology

Answer 6

Decrease in barometric pressure

Question 7

CO2 continually excreted from pulmonary blood into alveoli

Answer 7

High altitudes

Question 8

Water vaporizes into inspired air from respiratory surfaces

Answer 8

Altitudes

Question 9

CO2 and water vapor _________ the alveolar oxygen.

Answer 9

Decrease

Question 10

Water vapor pressure in alveoli remains at ______ mmHg at normal body temperature regardless of altitude.

Answer 10

47 mmHg

Question 11

The difference between this 2 alveolar ventilation ________ much more in the acclimitized than in the unacclimatized person.

Answer 11

increases

Question 12

In the acclimatized person, who increases his/her ventilation about fivefold, the PCO2 falls to about ___mmHg because of increased respiration.

Answer 12

7 mmHg

Question 13

Up to an altitude of about 10,000 ft even when the air is breathed, the arterial oxygen saturation remains at least as high as ______%.

Answer 13

90%

Question 14

Above 10,000 ft arterial O2 saturation falls rapidly until it is slightly less than ____% at 20,000 ft and much less at still higher altitudes.

Answer 14

70%

Question 15

Saturation remains ___% until about 39,000 ft then it falls rapidly to about 50% at about 47,000 ft.

Answer 15

> 90%

Question 16

Comparing 2 arterial blood O2 saturation curves breathing _________ in an unpressurized airplane can ascend to far higher altitudes.

Answer 16

Pure O2

Question 17

The arterial saturation at 47,000 ft when breathing O2 is about ____% and equivalent to arterial O2 sat at 23,000 ft when breathing air.

Answer 17

50%

Question 18

An unacclimatized person usually can remain conscious until the arterial O2 saturation falls to ___% for short exposure times.

Answer 18

50%

Question 19

The ceiling for an aviator in unpressurized airplane when breathing air is about ________ and when breathing pure O2 is about _______ provided the O2 supplying equipment operates perfectly.

Answer 19

23,000 ft

47, 000 ft

Question 20

Effects during the first few days at altitude (14,000 ft):

Answer 20

1. Reduction in arterial PO2
2. Stimulates peripheral chemoreceptors
3. Cause increase in ventilation
4. Has 2 effects

Question 21

1st effect of 14,000 ft altitude:

Answer 21

1. Increase in ventilation

2. Brings alveolar PO2 closer to ambient PO2

Question 22

2nd effects at altitude (14,000 ft):

Answer 22

1. Increase in ventilation
2. Blows off CO2
3. Effect is respiratory alkalosis
4. Inhibits peripheral and central chemoreceptors
5. Decrease ventilatory drive

Question 23

To increase ventilatory drive:

Answer 23

1. Increase in heart rate
2. Increase in cardiac output
3. Enhances O2 delivery

Question 24

Effects during the next few days (>14,000 ft)

Answer 24

1. Acclimitization occurs
2. Causes ventilation to increase progressively by same amount as acute response
3. PO2 improves, PCO2 decreases

Question 25

Mechanisms to cause slow increase in ventilation

Answer 25

1. pH of CSF decreases - counteracts respiratory alkalosis due to hyperventilation and offsets inhibition of central chemoreceptors
2. Decreasing rate of acid secretion - done by kidneys due to respiratory alkalosis

Question 26

2 results after kidney responds to respiratory alkalosis:

Answer 26

1. Blood pH decreases toward normal

2. Spillage of HCO3 into the urine that leads to osmotic diuresis and production of alkaline urine

Question 27

Mechanisms to cause slow increase in ventilation:

Answer 27

1. Decrease pH of CSF
2. Decrease plasma of pH

*These two removes part of inhibtion caused by alkaline pH -> allows hypoxia to drive ventilation to higher values.

Question 28

Acute effects of hypoxia

1. _______ person (breathing air)
2. Beginning at altitude of ________ ft.

Answer 28

Unacclimatized person
12,000 ft
 * Drowsiness
 * Lassitude
 *Mental and muscle fatigue
 *Sometimes headache and euphoria
 *Occ nausea

Question 29

Stage of twitchings or seizures above _________ in unacclimatized

Answer 29

18,000 ft

Question 30

Stage of twitchings/seizures above _________ in acclimatized.

Answer 30

23,000 ft

• Coma
• Death

Question 31

A person remaining at high altitudes for days, weeks or years becomes more and more ___________ to low PO2 so it causes fewer deletrious effects on the body,

Answer 31

acclimatized

Question 32

Principal means by which acclimitization comes:

Answer 32

1. Increase in pulmonary ventilation
2. Increased numbers of RBC
3. Increased diffusing capacity of the lungs
4. Increased ability of tissue cells to use O2 despite low PO2

Question 33

Principal stimulus for causing increas in RBC production

Answer 33

Hypoxia

Question 34

Hematocrit rises from 40-45 to an average of about ______

Answer 34

60

Question 35

Whole blood hemoglobin concentration from _________.

Answer 35

15 to 20 g/dL

Question 36

Blood volume increase by _______

Answer 36

20-30%

Question 37

Normal diffusing capacity for O2 thru pulmonary membrane

Answer 37

21 mL/mm Hg/min

Question 38

Increase diffusing capacity:

Answer 38

Exercises and high altitude

Question 39

Reasons why diffusing capacity increases:

Answer 39

1. Increase pulmonary capillary blood volume
2. Increase in lung air volume
3. Increase in pulmonary arterial blood pressure

Question 40

Expands capillaries and increase surface area thru which O2 diffuse into the blood

Answer 40

Increase pulmonary capillary blood volume

Question 41

Expamds the surface area of alveolar - capillary interface

Answer 41

Increase in lung air volume

Question 42

Forces blood into the greater numbers of alveolar capillaries

Answer 42

Increase in pulmonary arterial blood pressure

Question 43

Cardiac output increases _____ immediately after person ascends to high altitude.

Answer 43

30%

Question 44

___________ DECREASES back toward normal over period of weeks as blood hematocrit increases so amount of O2 transported to peripheral body tissues remains about normal.

Answer 44

Cardiac output

Question 45

Growth of increase numbers of systemic circulatory capillaries in non pulmonary tissues called INCREASE TISSUE CAPILLARITY (_____________).

Answer 45

Angiogenesis

Question 46

Active tissus exposed to _________, increased in capillarity is marked.

Answer 46

Chronic hypoxia

Question 47

Natives in the Andes and Himalayas live at altitude above ___________.

Answer 47

13,000 ft

Question 48

Acclimatization of natives begins in _________.

Answer 48

Infancy

• Chest size - increased
• Body size - decreased
• High ratio of ventilatory capacity to body mass

Question 49

At high altitude, work capacity of all skeletal and cardiac muscles ________ in hypoxia.

Answer 49

Decreased

Question 50

At high altitude, work capacity is ________ in direct proportion to decrease in maximum rate of O2 uptake.

Answer 50

Reduced

Question 51

Unacclimatized work capacity

Answer 51

50%

Question 52

Acclimatized for two months

Answer 52

68%

Question 53

Native living at 13,200 ft but working at 17,000 ft.

Answer 53

87%

Question 54

Acute mountain sickness

Answer 54

1. Acute cerebral edema

2. Acute pulmonary edema

Question 55

Acute cerebral edema

Answer 55

1. Hypoxia
2. Local vasodilation of cerebral blood vessels
3. Increase blood flow into capillaries
4. Increase capillary pressure
5. Fluid leak into cerebral tissues
6. Cerebral edema

Question 56

Acute pulmonary edema:

Answer 56

1. Hypoxia
2. Pulmonary arterioles constrict
3. Increase capillary pressure
4. Local edema

Question 57

Chronic mountain sickness

Answer 57

1. Increase red cell mass
2. Increase blood viscosity
3. Decrease tissue blood flow
4. Decrease O2 delivery
5. Vasoconstricted pulmonary arterioles
6. Divert blood flow from low O2 to high O2 alveoli
7. Lung hypoxia