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Pulmonology > 6 - Abnormal Gas Exchange > Flashcards

6 - Abnormal Gas Exchange Flashcards

1
Q

What is a normal PaO2? What happens to it with age?

A

Normal = 100 mmHg

decreases with age (PaO2 = 109 - (0.41 * age)

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2
Q

When must A-aDO2 be wide?

A

When hypoxemia is present and PaCO2 is reduced

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3
Q

Ventilation brings [O2/CO2] to the alveolus and removes [O2/CO2] from the alveolus.

A

brings O2, removes CO2

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4
Q

Perfusion brings [O2/CO2] to the alveolus and removes [O2/CO2] from the alveolus.

A

brings CO2, removes O2

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5
Q

When giving supplemental oxygen to someone with a low V/Q, PO2 [increases/decreases/stays the same] and PCO2 [increases/decreases/stays the same] . Why?

A

PO2 increases; PCO2 stays the same (elevated)

Supplemental oxygen increases the amount of oxygen inspired and thus amount available in the alveous for equilibration with the capillary. However, it does not increase the rate of ventilation, so there is no increased CO2 removal and PCO2 remains high.

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6
Q

When calculating total oxygen content, [SaO2/PaO2] play a bigger part in the equation.

A

SaO2

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7
Q

Why doesn’t CaO2 change much when giving a healthy individual 100% FiO2?

A

Because PaO2 does not play a big part in the CaO2 equation (hemoglobin saturation matters more).

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8
Q

What is the point of hypoxic vasoconstriction?

A

It minimizes the contribution of a poorly ventilated alveolus to the overall PaO2

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9
Q

Why doesn’t hyperventilation improve hypoxemia due to a low V/Q? What is something that it does do?

A

Low V/Q - not enough ventilation to certain alveoli; the alveoli that are functional already have ha SaO2 of 98%, so an increase to 100% isn’t going to result in much of a change

Hyperventilation does lower PaCO2

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10
Q

What is the most common cause of hypoxemia?

A

V/Q mismatch

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11
Q

V/Q mismatch has a [normal/wide] A-a gradient.

A

Wide

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12
Q

V/Q mismatch [improves/does not improve] with hyperventilation

A

Improves little, but not much

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13
Q

V/Q mismatch [improves/does not improve] with increased FiO2

A

improves (PaO2 > 500 mmHg)

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14
Q

PaCO2 is [low/normal/high/variable] in V/Q mismatch.

A

Variable

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15
Q

A shunt has a [normal/wide] A-a gradient.

A

wide

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16
Q

PaCO2 is [low/normal/high/variable] in a shunt.

A

low

17
Q

The magnitude of hypoxemia due to a shunt depends on ___.

A

where the shunt is anatomically (mainstem bronchus vs. resipratory bronchiole)

18
Q

A shunt [improves/does not improve] with increased FiO2

A

Does not improve, or minimally improves (regardless of the oxygen percentage of the air, the shunt blocks it from getting into the alveoli)

19
Q

When is a diffusion abnormality usually seen? When is it seen if it is very severe?

A

Will be noticeable during exercise; if really bad, will be noticeable at rest

20
Q

In a patient with a diffusion abnormality, PaO2 levels are [low/normal/high] and PaCO2 levels are [low/medium/high]. Why?

A

O2 is low, CO2 is normal. CO2 is normal because it can diffuse much more easily than O2 can. Even though there is a thickened membrane between the capillary and alveolus, it is still able to diffuse normally

21
Q

A diffusion abnormality results in a [normal/wide] A-a gradient.

A

wide

22
Q

PaCO2 is [low/normal/high/variable] in a diffusion abnormality.

A

normal

23
Q

A diffusion abnormality [improves/does not improve] with increased FiO2

A

improves (creates a stronger O2 gradient)

24
Q

Global hypoventilation results in a [normal/wide] A-a gradient.

A

normal

25
Q

Global hypoventilation [improves/does not improve] with increased FiO2

A

improves

26
Q

PaCO2 is [low/normal/high/variable] in global hypoventilation.

A

increased

27
Q

When does hypoxemia result from decreased PiO2? What about FiO2?

A

PiO2 - high altitudes

FiO2 - fires

28
Q

Why does reduced PiO2 result in hypoxemia?

A

Because there is a much lower barometric pressure, there is a decreased driving pressure for oxygen to diffuse. As a result of this, there is not enough time for normal diffusion

29
Q

What is a normal value for PaCO2? What value defines hypercapnia?

A

Normal: 35-45 mmHg

Hypercapnia: PaCO2 > 45 mmHg

30
Q

Excess CO2 production [can/cannot] lead to hypercapnia.

A

Cannot. It is not enough to raise PaCO2 on it’s own. There must also be a problem with ventilation or dead space.

Pulmonology (25 decks)

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