Ventilation Perfusion Matching Flashcards Preview

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Flashcards in Ventilation Perfusion Matching Deck (17)
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1
Q

is ventilation greater at the base or the apex? what accounts for this?

A

it’s greater at the base than the apex b/c:

  1. pleural pressure is less negative at the base of the lung b/c of gravity, thus the base has lower transmural pressure
  2. compliance is higher in the base than the apex
2
Q

what is the effect of gravity on blood flow and ventilation?

A

effect on gravity on Q (6 fold) is much bigger than on V (50%)
-basis for V:Q ratio

3
Q

effect of gravity on V/Q ratio

A

V/Q ratio greater at the top of the lung, b/c even though V and Q are lower, V is greater than Q, thus making the ratio larger

4
Q

what is regional ventilation or perfusion?

A

the quantity of ventilation or perfusion which reaches a given region (Qr or Vr)
-both affect gas composition in alveolus, PCO2, and PO2

5
Q

shunt VS alveolar dead space

A
shunt = perfusion w/o ventilation (low PO2, PCO2, and V/Q)
ADS = ventilation w/o perfusion (high PO2, PCO2, and V/Q)
6
Q

does low V/Q (w/ low PAO2) cause vasoconstriction or vasodilation?

A

vasoconstriction, thus increases resistance to Q, diverting blood to better ventilated regions

  • diminishes Qr, increasing V/Q, increasing PO2, decreasing PCO2
  • very powerful mechanism to improve gas exchange
7
Q

do low PACO2 in alveoli with high V/Q cause bronchoconstriction or bronchodilation?

A

bronchoconstriction, thus increasing resistance of air flow, and diverting flow to better perfused regions to decrease Vr and return PO2 to normal values
-not very strong mechanism

8
Q

what does inhaling NO do?

A

causes vasodilation in better ventilated areas

-increases blood flow to these areas, and improves V/Q matching

9
Q

what does inhaling histamine do?

A

causes bronchoconstriction, pulmonary vasoconstriction, and systemic vasodilation

10
Q

does N2 wash out faster or slower in constricted vessels?

A

they wash out slowly in constricted vessels, and faster if dilated

11
Q

what is MIGET?

A

multiple inert gas elimination technique where lung is modeled as 50 compartments
-elimination and retention of 6 different gases, and derive V/Q from the 50 compartments

12
Q

how is PAO2, PaO2, CaO2, PVO2, CVO2, and FIO2 in low alveolar PO2? can O2 therapy help?

A
PAO2: low
PaO2: low (normal A-a gradient)
CaO2: low
PVO2: low
CVO2: low
FIO2: increased
O2 therapy helps
13
Q

how is PAO2, PaO2, CaO2, PVO2, CVO2, and FIO2 in diffusion impairment? can O2 therapy help?

A
PAO2: normal
PaO2: (A-a gradient is increased)
CaO2: low
PVO2: low
CVO2: low
FIO2: increased
O2 therapy helps
14
Q

how is PAO2, PaO2, CaO2, PVO2, CVO2, and FIO2 in right to left shunt? can O2 therapy help?

A
PAO2: normal; PcO2 = PAO2
PaO2: low (A-a gradient is increased at level of shunt admixture)
CaO2: low
PVO2: low
CVO2: low
FIO2: normal
O2 therapy can't help
15
Q

how is PAO2, PaO2, CaO2, PVO2, CVO2, and FIO2 in alveolar dead space V/Q mismatch? can O2 therapy help?

A
PAO2: normal (functionally lower if using end-tidal PO2)
PaO2: low
CaO2: low
PVO2: low
CVO2: low
FIO2: increased
O2 therapy can help
16
Q

why is PaO2 slightly less than PcO2?

A

due to normal shunt

17
Q

what kind of shunt is asthma?

A

a false shunt

-with restricted airways, O2 therapy can help

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