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Flashcards in Hypoxia Deck (19):

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

d) 100% oxygen with positive pressure breathing.


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

d) Decrease in tissue oxygenation and cerebral vasodilatation


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

d) all the above


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

b) hypocapnic cerebral vascular resistance


What is the etiology of the oxygen paradox?

may be related to arterial hypotension and persistent hypocapnia.


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

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


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

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


Oxidative phosphorylation is not limited until cellular oxygen tension falls to:
a) 149 mmHg
b) 103 mmHg
c) 62 mmHg
d) 1-3 mmHg

d) 1-3 mmHg


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

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.


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

c) 10,000 feet.


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

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


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

c) 33K.


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?

Oxygen Paradox


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

d) Respiratory failure


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.

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


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

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


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

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


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

b) decrease in arterial oxygen tension


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

e) b and c