Hypoxia

Question 1

An aviator is going to be exposed to an altitude of 42,000 feet. As the flight surgeon, which appropriate oxygen system should you recommend?

a) High flow oxygen at 50% franction of inspired oxygen by rebreather mask
b) full pressure suit
c) 100% oxygen without positive pressure breathing
d) 100% oxygen with positive pressure breathing
e) 50% oxygen with positive pressure breathing

Answer 1

d) 100% oxygen with positive pressure breathing.

Question 2

Hypoxia cna cause significant hyperventilation; subsequent hypocapnia will result in which of the following?

a) Improved tissue oxygen delivery and cerebral vasodilation
b) No effect on tissue oxygen delivery and cerebral vasodilation
c) Decrease in tissue oxygenation and cerebral vasoconstriction
d) Decrease in tissue in tissue oxygenation and cerebral vasodilation
e) improved tissue oxygenation and cerebral vasodilation

Answer 2

d) Decrease in tissue oxygenation and cerebral vasodilatation

Question 3

The alveolar oxygen tension produced by breathing air at a given altitude is determined by:

a) the alveolar carbon dioxide ratio
b) the respiratory exchange ratio
c) the intensity of the ventilatory response to hypoxia
d) all the above

Answer 3

d) all the above

Question 4

Side effects of acute hypobaric hypoxia, or of the compensatory changes which may accompany it, include:

a) decreased pulmonary vascular resistance
b) hypocapnic cerebral vasoconstriction
c) decreased blood viscosity
d) increased bicarbonate absorption in the kidneys

Answer 4

b) hypocapnic cerebral vascular resistance

Question 5

What is the etiology of the oxygen paradox?

Answer 5

may be related to arterial hypotension and persistent hypocapnia.

Question 6

The most striking circulatory effect of hypoxia during pressure breathing is:

a) tachycardia
b) increased arterial blood pressure
c) reduction in cardiac output
d) increased incidence of syncope
e) reduction of the effective blood volume

Answer 6

Tachycardia occurs yes, but the most striking incidence is the potential for syncope.

Question 7

A reduced oxygen pressure differential across the alveolar capillary barrier is associated with:

a) hypoxic hypoxia
b) hypemic hypoxia
c) stagnant hypoxia
d) histotoxic hypoxia

Answer 7

a) hypoxic hypoxia caused by a reduction in the partial pressure of alveolar oxygen as with altitude exposure.

Question 8

Oxidative phosphorylation is not limited until cellular oxygen tension falls to:

a) 149 mmHg
b) 103 mmHg
c) 62 mmHg
d) 1-3 mmHg

Answer 8

d) 1-3 mmHg

Question 9

The consideration of the composition of the alveolar air indicates that the physiologic dividing line between the atmospheric hypoxia and anoxia occurs at an altitude of:

a) 61K
b) 59K
c) 46K
d) 35K

Answer 9

c) 46K. This means that the atmosphere no longer contributes to respiration as the oxygen simply can’t get in due to too little pressure. So wearing oxygen at this level without pressure, does little good.

Question 10

In terms of the alveolar oxygen tension (PaO2), breathing 100% oxygen at 40K is essentially the equivalent of breathing air at:

a) sea level
b) 8K
c) 10K
d) 12K

Answer 10

c) 10,000 feet.

Question 11

A very commonly used maneaver to stop hyperventilation is prolonged breath holding in maximum inspiration. Aviators should be educated to___________.

Answer 11

avoid doing this due to the possibility to increase vagal tone, cause bradycardia, and then have syncope.

Question 12

At which altitude is the alveolar oxygen tension breathing 100% oxygen equal to the alveolar tension breathing air at sea level?

a) 10K
b) 18K
c) 33K
d) 43K

Answer 12

c) 33K.

Question 13

After prolonged exposure to low grade hypoxia, as in breathing ambient air at 15,000 feet to 18,000 feet for several minutes, administration of oxygen sometimes leads to further deterioration for a short time before improvement begins. This phenomenon is called what?

Answer 13

Oxygen Paradox

Question 14

The first response to prolonged hypoxia that is characteristically seen at 25,000 feet altitude is:

a) unconsciousness
b) circulatory failure
c) vasovagal syncope
d) respiratory failure

Answer 14

d) Respiratory failure

Question 15

2,3 DPG is found in increasing concentrations in erythrocytes during hypoxic states. This serves as a protective mechanism by:

a) stimulating the cardioacceleratory center of the CNS
b) stimulating the medullary respiratory center causing an increased respiratory rate.
c) stimulating both the cardioacceleratory and respiratory centers
d) shifting the oxygen dissociation curve to the right.
e) shifting the oxygen dissociation curve to the left.

Answer 15

d) 2,3 DPG shifts the oxygen dissociation curve to the right.

Question 16

The apparent target organ showing the most significant symptoms secondary to hypoxia caused by altitude exposure appears to be the:

a) skeletal muscle
b) smooth muscle
c) brain
d) bone
e) skin

Answer 16

c) brain. The brain has a high demand for oxygen.

Question 17

All of the following cause a shift to the right of the oxygen hemoglobin dissociation curve EXCEPT:

a) an increase in temperature
b) an increase in pH
c) a decrease in pH
d) a increase in 2, 3, DPG
e) an increase in H+ ion concentration

Answer 17

b) an increase in pH.

Things that shift to the right: 
Increase in temperature
Increase in CO2 
Increase in H+ (decrease in pH)
Increase in 2,3, DPG

Question 18

Which of the following is an effect of altitude exposure?

a) vasodilation of extremities
b) decrease in arterial oxygen tension
c) decrease in respiratory frequency and tidal volume
d) bradycardia
e) all of the above

Answer 18

b) decrease in arterial oxygen tension

Question 19

Smoking is a hazard to flying because it increases the chances of an episode of hypoxia by:

a) vasodilation of cerebral blood vessels
b) constriction of bronchioles
c) Increasing carboxyhemoglobin levels
d) decreasing heart rate
e) b and c

Answer 19

e) b and c