Vent and perfusion

Question 1

most common cause of hypoxemia

Answer 1

V/Q mismatch

Question 2

define vent.

Answer 2

amount of air into lungs, L/min

Question 3

define perf.

Answer 3

amount of blood to lungs, L/min

Question 4

define hypoxemia

Answer 4

low art. O2

Question 5

define hypercapnia

Answer 5

high art. CO2

Question 6

define shunt

Answer 6

blood that passes the lung

Question 7

what is idea V/Q ratio

Answer 7

1

Question 8

what is normal alveolar and arterial pO2

Answer 8

100 and 90 torr

Question 9

define SaO2

Answer 9

% of Hb saturated with O2

Question 10

5 causes of arterial hypoxemia

Answer 10

1. low inspired O2
2. hypoventilation
3. poor diffusion
4. shunt
5. V<Q

Question 11

cause of low inspred O2

Answer 11

altitude and poor anethesia

Question 12

what is regional hypoventilation

Answer 12

part of lung not getting air - like a peanut in the lung

Question 13

how will poor diffusion affect paO2 and paCO2

Answer 13

O2 - low

CO2 - will be normal or even low, because not affected by diffusion

Question 14

what will happen to CO2 and O2 if the is low V/Q in one region

Answer 14

local hypercapnea, but normal global capnea, both local and global hypoxemia

Question 15

what will happen if give more O2 is v/Q is low

Answer 15

will improve if can reach regional area

Question 16

what are 3 causes of shunts?

Answer 16

1. within the lung (pneumonia)
2. intracardiac
3. physiological - bronch arts. and veins

Question 17

3 characteristics of a shunt

Answer 17

1. doesn’t improve with 100% O2
2. does not increase pCO2 - breathe faster
3. global hyperventialtion - to decrease CO2

Question 18

what is it called when V>Q?

Answer 18

dead space - a region with no perfusion

Question 19

what is most important in V/Q

Answer 19

the ratio, not absolute values

Question 20

where in the lung does most ventilation and perfusion occur?

Answer 20

at the base

Question 21

how does the V/Q ratio change as go from bottom to top of lung?

Answer 21

goes up

Question 22

how does the lung improve gas exchnage during excercise

Answer 22

perfuses more apical lung portions

Question 23

what is PAO2 calculation

Answer 23

PA02 = PiO2 - (1.25xPaCO2)

Question 24

what is normal A-a gradient

Answer 24

10-15

Question 25

when do we need to calculate the A-a gradient

Answer 25

only when pCO2 is abnormal - is pCO2 is normal, we know there is a mismatch problem

Question 26

how does the lung react to V<Q?

Answer 26

arteries constrict to decrease perfusion

Question 27

what does pulmonary hypertension cause?

Answer 27

cor pulmonale - heart disease caused by lung