B4.055 Hypoxia

Question 1

how can hemoglobin help distinguish acute form chronic hypoxia?

Answer 1

if normal levels : acute

if greater than 15 : chronic

Question 2

how can CaO2 help distinguish acute form chronic hypoxia?

Answer 2

is O2 content what would be predicted at the given PO2 if Hg is 15?
aka, PO2 = 40, Ca = 15
PO2 = 95 Ca = 20
PO2= 40 Ca should not = 20 unless Hgb is elevated

Question 3

change in bicarb per pH unit

Answer 3

10 mM HCO3- / pH unit

Question 4

change in pH per 10 mmHg CO2

Answer 4

0.08

Question 5

what measurement gives hints about the level of alveolar ventilation

Answer 5

PaCO2

NOT PaO2

Question 6

2 major types of situations in which someone might have decreased arterial PO2

Answer 6

1. normal lung function (A-a) normal

2. abnormal lung function (A-a) larger than 10 mmHg

Question 7

normal mixed expired PCO2

Answer 7

2/3 of arterial CO2

Question 8

normal VD/VT

Answer 8

1/3

Question 9

does Hg level affect arterial PO2?

Answer 9

no

only alveolar O2 determines arterial PO2

Question 10

in cases of mild to moderate anemia, what happens to alveolar ventilation?

Answer 10

nothing

PaO2 doesn’t change so chemoreceptors not stimulated

Question 11

what happens in cases of severe anemia

Answer 11

poor O2 delivery causes a switch to anaerobic respiration in tissues
lactic acid increased, decreasing pH and activating chemoreceptors

Question 12

what compensation could help improve O2 delivery to systemic organs when Hg is reduced?

Answer 12

compensatory increase in CO (Q)

VO2 = Q * (CaO2-CvO2)

Question 13

what is the effect of hyperventilation of the ODC

Answer 13

lower PaCO2 and higher pH tend to increase O2 affinity of Hb

CO2 usually inhibits binding

Question 14

once you establish hypoventilation, what should you do next?

Answer 14

calculate (A-a) gradient to see if other factors are at work in the lung that are impairing functioning

Question 15

VD/VT=

Answer 15

(PaCo2-PECO2)/PaCO2