17. V/Q mismatch Flashcards Preview

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Flashcards in 17. V/Q mismatch Deck (28):
1

V/Q means

ventilation/ perfusion

2

V/Q ideally

ideally ventilation is matched to perfusion ( V/Q =) for adequate gas exchange

3

V/Q lung zones and explanation

V/Q at apex = 3 ---> wasted ventilation
V/Q at base = 0.6 ---> wasted perfusion

4

V/Q : P artery (Pa) P venous (Pv) P alveoli (PA)
bigger , samaller in the apex of the lung

PA>Pa>PV

5

V/Q : P artery (Pa) P venous (Pv) P alveoli (PA)
bigger , samaller in the middle of the lung

Pa>PA>PV

6

V/Q : P artery (Pa) P venous (Pv) P alveoli (PA)
bigger , samaller in the base of the lung

Pa> PV > PA

7

V/Q = 0 explanation

airway obstruction ( SHUNT)
100% O2 does not improve alveolar PO2

8

V/Q =o --> 100% O2 ----->alveolar PO2

does not improve alveolar PO2

9

V/Q = infinity

blood flow obstruction ( physiologic dead space)

10

assuming 100% 02?

it improve PaO2

11

V/Q --> response to exercise

increased cardiac output --> vasolidation of apical capillaries --> V/Q ratio approaches 1

12

organism that thrive in High O2 - area un the lungs and example

apex
eg. TB

13

V, Q, V/Q ratio distribution in apex, base and middle of the lung

V/Q as aoex as higher ( 0.6 at base, 3 at apex)
Both V and Q are greater at the base, but increasing of Q from apex to base is greater from th increasing of V and that V/Q is decreased in base (0.6)

14

hypoventilation causes hypoxemia- why

hypoventilation --> increased PaCO2 --> increased PACO2 -> decreased PAO2

15

PaCO2 equation

PaCO2 = K x VCO2/ VA
VA : alveikar ventlation
VCO2 : rate of elimination

16

increased VCO2 - situation

fever
exercise
overconsumption of carbohydrates
chill tetanus

17

• A patient has tuberculosis. This and other microorganisms that thrive in high-oxygen environments flourish in which part of the lungs?

The apex

18

• A woman chokes and aspirates a peanut. What is her ventilation/perfusion ratio likely to be?

Approaching 0, as airway obstruction creates a blood flow shunt which isn't part of gas exchange (0 = "oirway" obstruction)

19

• A child chokes on a peanut. This airway obstruction leads to perfusion with no ventilation within an area of the lungs. What is this called?

A shunt

20

• A man suffers a pulmonary embolus. What is his ventilation/perfusion ratio likely to be?

Approaching ∞, as the pulmonary embolus is a blood flow obstruction, causing physiologic dead space (∞ = blood flow obstruction)

21

• In a hypoxic patient due to ____ (dead space/shunting), 100% oxygen does improve the partial pressure of oxygen in the blood.



Dead space (assuming the dead space is <100%)

22

• What is the ideal ventilation/perfusion ratio for gas exchange?

1:1

23

• Within what part of the lung does ventilation/perfusion equal approximately 3?

The apex of the lung

24

• In the apex of the lung, there is wasted ____ (perfusion/ventilation).

Ventilation

25

• Within what part of the lung does ventilation/perfusion equal approximately 0.6?





The base of the lung

26

• In the base of the lung, there is wasted ____ (perfusion/ventilation).

Perfusion

27

• Is perfusion greater at the base of the lung or the apex of the lung?

The base of the lung

28

• A patient exercises. The vasodilation of the apical capillaries of the lung results in what change to the ventilation/perfusion ratio?

The ventilation/perfusion ratio approaches 1, maximizing gas exchange to meet the metabolic demands of exercise