Ventilation Perfusion Matching Flashcards Preview

Physiology > Ventilation Perfusion Matching > Flashcards

Flashcards in Ventilation Perfusion Matching Deck (17)
Loading flashcards...
1

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

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

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

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

3

effect of gravity on V/Q ratio

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

what is regional ventilation or perfusion?

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

5

shunt VS alveolar dead space

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

6

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

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

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

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

what does inhaling NO do?

causes vasodilation in better ventilated areas
-increases blood flow to these areas, and improves V/Q matching

9

what does inhaling histamine do?

causes bronchoconstriction, pulmonary vasoconstriction, and systemic vasodilation

10

does N2 wash out faster or slower in constricted vessels?

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

11

what is MIGET?

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

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

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

13

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

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

14

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

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

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

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

16

why is PaO2 slightly less than PcO2?

due to normal shunt

17

what kind of shunt is asthma?

a false shunt
-with restricted airways, O2 therapy can help

Decks in Physiology Class (60):