B4-055 Hypoxia

Question 1

some inefficiency of gas exchange in a normal healthy lung is due to

2

Answer 1

• heterogeneity of VA/Q distribution
• small veno-arterial shunt

Question 2

units with a VA/Q higher than ideal have a higher […] and lower […]

Answer 2

higher PO2
lower CO2

Question 3

units with a lower VA/Q than ideal have a lower […] and a higher […]

Answer 3

lower PO2
higher PCO2

Question 4

under normal conditions, the V/Q ratio of the lung is

Answer 4

around 1

Question 5

ventilation per unit volume is greatest at the […] of the lung

Answer 5

base

progressively smaller toward apex

Question 6

perfusion is greatest at the […] of the lung

Answer 6

base

Question 7

changes in VA/Q are lowest at the […] of the lung and increase toward the […]

Answer 7

base
apex

Question 8

at the top of the lung
VA/Q:
PCO2:
PO2:

Answer 8

VA/Q: high
PCO2: low
PO2: high

Question 9

at the bottom of the lung
VA/Q:
PCO2:
PO2:

Answer 9

VA/Q: low
PCO2: increased
PO2: decreased

Question 10

alveolar ventilation will be […] in areas of low compliance

Answer 10

low

Question 11

alveolar ventilation will be […] in areas of high compliance

Answer 11

high

Question 12

alveolar ventilation will be […] in areas of low resistance

Answer 12

high

Question 13

alveolar ventilation will be […] in areas of high resistance

Answer 13

low

Question 14

for any given PaCO2, the PECO2 will be

Answer 14

lower

due to volume from dead space

Question 15

the PECO is diluted about 1/3 compared to

Answer 15

PaCO2

Question 16

normal VD/VT

Answer 16

.25-.35

Question 17

when VD/VT > 0.6, patients are

Answer 17

ventilated

cannot maintain ventilation

Question 18

low PaO2
without much increase in CO2

Answer 18

increased dead space

Question 19

VD/VT > 0.3

Answer 19

increased dead space

Question 20

shunt unit produce a […] in arterial PO2

Answer 20

large decrease

venous blood mixed with arterial blood, mixing PO2

Question 21

does increased PIO2 or hyperventiliation increase PaO2 significantly?

Answer 21

no

shunt

Question 22

shunt units produce a […] in PaCO2

Answer 22

small increase

Question 23

ineffective at raising PaO2, but effective in lowering PaCO2

Answer 23

hyperventilation

Question 24

VD/VE >0.35

Answer 24

increased dead space

Question 25

A-aPO2 > 10 mmHG

Answer 25

shunt

Question 26

low PaO2 is sensed by

Answer 26

peripheral chemoreceptors

Question 27

when PAO2-PaO2 is greater than 5-10, you have

Answer 27

diffusion impairment | increased thickness or decreased surface area for gas exchange

Question 28

* produce a large decrease in arterial PO2 * produce relatively small increase in arterial CO2

Answer 28

shunt units

Question 29

normal PAO2, PaO2, CaO2 Low Q

Answer 29

cardiogenic shock

Question 30

PaO2 of 40 mmHg CaO2 is 15 ml/dl | acute or chronic hypoxia

Answer 30

acute hypoxia

Question 31

normal PaO2

Answer 31

90-95

Question 32

normal CaO2

Answer 32

20 ml/dl

Question 33

at a PaO2 of 40, we would expect an O2 content of

Answer 33

15 ml/dl | 75% saturation

Question 34

is PaO2 is 40 mmHg but O2 content is normal, | acute or chronic

Answer 34

chronic | long term compensation (increased Hb)

Question 35

PaCO2 is 60 mmHg pH is 7.36 | acute or chronic hypoxia?

Answer 35

chronic | pH is normal despite high PaCO2 compensated respiratory acidosis

Question 36

each 10 mmHg increase in PaCO2 will decrease pH by [...] in the short term

Answer 36

0.08 units

Question 37

PaO2 is 40 mmHg CaO2 is 19.2 ml/dl | acute or chronic hypoxia

Answer 37

chronic | PaO2 is low, but CaO2 is normal compensation

Question 38

PaCO2 is 20 mmHg pH is 7.56 | acute or chronic

Answer 38

acute | PaCO2 decreased by 20, so expected pH increase is .16 non compensated

Question 39

alveolar ventilation is only defined by a change in

Answer 39

PaCO2

Question 40

:)

Answer 40

.

Question 41

if Hb is greater than 15 g/dL

Answer 41

chronic hypoxia

Question 42

if pH is what would be predicted based on an acute change in PaCO2

Answer 42

non-compensated

Question 43

0.08 change in pH for every

Answer 43

10 mmHg change in PaCO2

Question 44

PaCO2 > 40 mmHg

Answer 44

hypoventilation

Question 45

PaCO2 < 40 mmHg

Answer 45

hyperventilation

Question 46

PAO2 - PaO2 should be

Answer 46

5-10 mmHg

Question 47

normal dead space

Answer 47

.25-.35

Question 48

if PAO2 - PaO2 is greater than 5-10, what does this mean?

Answer 48

something besides a change in ventilation is also happening | could be diffusion issue, shunt unit

Question 49

primarily drive low PaO2

Answer 49

shunt units

Question 50

normal PECO2

Answer 50

30

Question 51

under normal conditions with a normal CO, the difference in systemic arterial and venous O2 content is

Answer 51

5 ml O2/dl

Question 52

* arterial O2 content is normal * venous O2 content is markedly decreased | what does this indicate?

Answer 52

decreased flow to systemic organs | hypovolumic shock

Question 53

* arterial PO2 is 40 mmHg * arterial O2 content is 15 ml/dl | what would this indicate?

Answer 53

acute hypoxia | obstruction of large bronchus

Question 54

how does anemia affect arterial O2 content,PaO2, and arterial blood content?

Answer 54

CaO2: decreased PaO2: normal arterial blood O2: decreased

Question 55

how does hypoventilation affect PaCO2 and PaO2?

Answer 55

PaCO2: increased PaO2: decreased