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Respiratory Week 2 > Ventilation/Perfusion Hypoxia > Flashcards

Ventilation/Perfusion Hypoxia Flashcards

1
Q

what vessel causes shunting at the level of the alveoli capillaries?

A

bronchial arteries enter on the distal end of oxygen exchange in the alveoli and therefore mix their deoxy blood with the oxy blood

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2
Q

name the five major causes of hypoxemia?

A 
diffusion impairment
low PiO2
hypoventilation
shunt
V/Q mismatch
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3
Q

what is the best way to increase alveolar partial pressure of oxygen when increasing in altitude and decreasing pressure?

A

hyperventilation to blow off the CO2 and yield higher percentage of oxygen partial pressure

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4
Q

what are two ways other than hyperventilation that we adapt to high altitude changes in oxygen content?

A

polycythemia-RBC increase

DPG increase to make dissociation of Hb and O2 easier

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5
Q

at what PaO2 is Hb almost entirely saturated?

A

70-75

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6
Q

when there is a thickened diffusion barrier, what allows the blood to still get equilibrated with alveolar oxygen?

A

the reserve time that is normally there…remember how blood is in alveoli for 0.75 seconds and in normal conditions equilibrates in 0.25 seconds so you still have the last 0.5 seconds when there is a diffusion issue

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7
Q

what usually causes diffusion impairment leading to hypoxemia?

A

pulmonary edema or fibrosis

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8
Q

how do you treat hypoxemia from diffusion impairment?

A

give Oxygen…it will increase the driving force or gradient

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9
Q

what is the most common cause of an anatomic shunt leading to hypoxemia?

A

aspiration of something that blocks a bronchus or something

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10
Q

can you treat hypoxemia from anatomic shunt with oxygen?

A

NO

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11
Q

what is pulmonary venous admixture?

A

non shunted blood plus shunted blood

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12
Q

in hypoventilation, what actually causes the decrease in PO2?

A

the increase in CO2 as you cut ventilation lower

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13
Q

in hypoventilation how will the A-a gradient change?

A

it will not change!!…both values will be lower but difference will not change

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14
Q

what are the two most common causes of diffusion impairment in lungs? where is the pathophys taking place?

A

fibrosis and edema occurring in the interstitial space

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15
Q

in an anatomic shunt, what is the pathophysiology?

A

there is blockage of the airways that impedes ventilation to actually occur, so blood goes there and cannot exchange CO2 for O2 due to the accumulation in the alveoli, so it continues on as low O2 blood

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16
Q

can you treat an anatomic shunt with oxygen?

A

NO…because no matter how high the O2 it aint getting in there to exchange

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17
Q

if you have airway blockage…what is V/Q close to?

A

0

18
Q

if you have PE what is your V/Q close to?

A

infinity

19
Q

does the V/Q increase or decrease in exercise? what does this lead to?

A

the V/Q increases throughout the lung…leads to more dissolved oxygen

20
Q

does a V/Q mismatch lead to an increased A-a?

A

yes

21
Q

does a physiologic shunt lead to an increased A-a?

A

yes

22
Q

does diffusion impairment lead to an increased A-a?

A

yes

23
Q

does hypoventilation lead to an increased A-a?

A

no

24
Q

name three common diseases that cause V/Q mismatch

A

bronchitis
asthma
CF

25
Q

does V/Q mismatch respond to O2 therapy?

A

yes

26
Q

what four diseases commonly cause physiologic shunts? what is an accident that can cause it?

A

COPD
CF
ARDS
Pneumonia

27
Q

do physiologic shunts respond to O2 therapy?

A

no usually they do not…because the O2 aint go no where to go

28
Q

does diffusion impairment respond to O2 therapy?

A

yes it will…created bigger gradient that can go through the increased interstitium

29
Q

with anemia, how will A-a gradient be affected? will it respond to O2 therapy?

A

the A-a gradient will be the same because dissolved partial pressures will not change…
it will not respond to O2 because the O2 aint got no where to bind

30
Q

what are the two common anatomical shunts?

A

bronchial arteries and coronaries

31
Q

what is the cutoff for hypoxic respiratory failure?

A

PO2 less than 60 mmHg

32
Q

what is the cutoff for hypercarbic respiratory failure?

A

PCO2 over 50

33
Q

what do impaired mental status/headache mean related to what type of respiratory failure?

A

means it is hypercapnia

34
Q

what is atelectasis? does it lead to a shunt or dead space?

A

collapsed alveoli, shunt

35
Q

does mechanical ventilation help a shunt? why or why not?

A

yes it will…because the PEEP can keep the airways open a bit more to allow for ventilation

36
Q

in dead space ventilation, why does the patient not get hypercapnia?

A

even though there is dead space, the ventilation and specifically the tachypnic response leads to blowing off the CO2

37
Q

with what type of hypoxia does an individual get really tachypnic when exercising? why?

A

commonly from diffusion limited like pulmonary fibrosis

during exercise you have increased CO that must fly through the respiratory system and it does not have enough time to pick up adequate oxygen when there is a diffusion barrier

38
Q

explain why the A-a gradient in hypoventilation does not increase?

A

this is because of the increase in CO2 during hypoventilation taking space away from the alveolar area to accumulate more oxygen, so even though arterial oxygen is low alveolar is too

39
Q

what are two causes of hypercapnia?

A

decreased alveolar ventilation from dead space ventilation

higher CO2 production due to work of breathing

40
Q

does emphysema lead to decreased perfusion or ventilation?

A

perfusion…recall the grapes turning to grapefruit and loss of the capillaries

41
Q

does emphysema lead to a shunt, dead space, or diffusion limit?

A

physiologic dead space

Respiratory Week 2 (12 decks)

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