Altitude

Question 0

Barometric pressure at 10,000 ft

Answer 0

523 mmHg

Question 1

Barometric pressure at sea level

Answer 1

760mmHg

Question 2

Barometric pressure @ 50,000 ft

Answer 2

87mmHg

Question 3

The basic cause of all hypoxia problems in high altitude physiology

Answer 3

Decrease in barometric pressure

Question 4

As the barometric pressure decreases, what happens to the atmospheric oxygen partial pressure?

Answer 4

The atm oxygen partial pressure decreases proportionately, remaining at all times slightly less than 21% of the total barometric pressure

Question 5

Two gases that dilute the oxygen in the alveoli

Answer 5

Carbon dioxide and water vapor

Question 6

Water vapor pressure in the alveoli at room temp

Answer 6

47mmHg

Question 7

What happens to alveolar PCO2 during exposure to very high altitudes?

Answer 7

• The alveolar PCO2 falls from sea level value of 40mmHg to lower levels
• the acclimatized person increases his ventilation to five fold - 7mmHg because of increased respiration

Question 8

As the altitude goes higher the alveolar ventilation increases much more in the _________ person. (acclimatized/unaclimatized)

Answer 8

Acclimatized person

Question 9

At about 10,000 ft, even wen air is breathed, the arterial oxygen saturation remains ______

Answer 9

At least as high as 90%

Above 10,000 ft, art oxygen saturation falls rapidly

*when breathing air

Question 10

When breathing pure oxygen, the aviators alvelolar oxygen sat remain 90% at about how many feet?

Answer 10

39,000 ft

Then it fall rapidly to abt 50% at 47,000 ft

Question 11

An unacclimatized person usu can remain conscious until the arterial oxygen saturation falls to what percent?

Answer 11

50%

Question 12

Acute effects of hypoxia at 12,000 ft (unacclimatized person)

Answer 12

Drowsiness
Lassitude
Mental and muscle fatigue
Sometimes headache, euphoria
Occasionally nausea

Question 13

Acute effects of hypoxia at above18,000 ft (unacclimatized person)

Answer 13

Twitchings or seizures

Question 14

Acute effects of hypoxia above 23,000 ft (unacclimatized person)

Answer 14

Coma and death

Question 15

One of the most impt effects of hypoxia

Answer 15

Decreased mental proficiency

- decreased judgement, memory, & performance of discrete motor movements

Question 16

The principal means by which acclimatization comes about

Answer 16

1. Great increase in pulmonary ventilation
2. Increased nummbers of rbc
3. Increased diffusing capacity of the lungs
4. Increased vacularitu of the tissues
5. Increased ability of the tissue cells to use oxygen despite low PO2

Question 17

Immediate exposure to low PO2 stimulates the arterial chemoreceptors leads to…?

Answer 17

Increased alveolar ventilation

to a maximun of abt 1.65 times normal

Question 18

What effect would the immediate increase in pulmonary ventilation on rising altitude have on PCO2 and body fluid pH?

Answer 18

Large quantities of CO2 are blown off,
reducing the PCO2, &
increasing the pH of the body fluids

*these changes inhibit the brain stem respiratory center and thereby oppose the effect of low PO2 to stimulate respiration by way of the peripheral arterial chemoreceptors in the carotid and aortic bodies. Ensuing 2-5 days this inhibition fades away, and ventilation increases to 5x normal

Question 19

The kidneys respond to decreased PCO2 by what mechanism?

Answer 19

Reducing hyrogen ion secretion and increasing bicarbonate excretion

Question 20

The principal stimulus for causing an increase in rbc production

Answer 20

Hypoxia

Question 21

The normal diffusing capacity for oxygen thru the pulmonary membrane

Answer 21

21 mL/mmHg/min

Question 22

What factors increase the diffusing capacity for oxygen (after acclimatization)

Answer 22

Exercise (3x)
At high altitudes
Increased pulmonary capillary blood volume
Increase in lung air volume
Increase in pulmonary arterial blood pressure

Question 23

Peripheral circulatory system changes during acclimatization

Answer 23

• Increased CO to as much as 30% but decreases back to normal in weeks as the blood hct increases
• growth of increased numbers of systemic circulatory capillaries in the nonpulmonary tissues/ increased tissue capillary (angiogenesis) - also in active tissues exposed to chronic hypoxia

Question 24

Acclimatization to Low PO2 ( high altitudes)

Answer 24

> increased pulmonary ventilation
- decreased pH in the fluids
increased RBC and Hgb conc
increased diffusing capacity
- increased pulmonary capillary blood volume,
lung air volume, increase in pulmonary arterial
blood pressure
increased CO
increased tissue capillarity (angiogenesis)
cellular acclimatization - increased # of mitochondria and cellular oxidatie enzyme systems

Question 25

Work capacity is _________ (reduced/increased) in direct proportion to the decrease in maximum rate of oxygen uptake that the body can achieve

Answer 25

Reduced

Question 26

Acute mountain sickness and high altitude pulmonary edema

Two events that happen when some people ascend rapidly to high altitudes ( begins from a few hours up to about 2 days)

Answer 26

1. Acute cerebral edema

2. Acute pulmonary edema

Question 27

Believed to result ffom local vasodilation of the cerebral blood vessels, caused by the hypoxia

Answer 27

Acute cerebral edema

Dilation of the arterioles increases blood flow into the capillaries, thus increasing capillary pressure, which causes leak into the cerebral tissues

Can lead to severe disorientation and other effects related to cerebral dysfunction

Question 28

Cause is still unknown
Suggested answer: severe hypoxia causes the pulmonary arterioles to constrict potently; const is greater in some parts of the lungs; capillary pressure in these areas become especially high and local edema occurs

Answer 28

Acute pulmonary edema

Extension leads to spreading pulmonary edema & severe pulmonary dysfunction can be lethal

Allowing person to breathe oxygen usually reverses the process within hours

Question 29

Chronic mountain sickness

Answer 29

When a person remains at high altitude for too long

1. The red cell mas and hct become exceptionally high
2. The pulmonary arterial pressure becomes elevated (even more than normal during acclimatization)
3. Right side of the heart becomes greatly enlarged
4. Peripheral arterial pressure begins to fall
5. Congestive heart failure ensues
6. Death, unless person is removed to a lower alt