PATHOPHYS

Question 1

what is the most common predisposing factor to ALI/ARDS?

Answer 1

sepsis

Question 2

what is alveolar dead space?

Answer 2

alveoli ventilated but no perfused, so cannot participate in gas exchange

Question 3

can increasing alveolar dead space be normal?

Answer 3

NO, increased alveolar dead space is ALWAYS PATHOLOGIC

Question 4

what is the normal value of tissue O2 consumption ?

Answer 4

250 mL/min

Question 5

What is the normal value for PAO2?

Answer 5

100 mmHg

Question 6

How do you define hyperventilation?

Answer 6

ventilating more than your metabolic needs defined by low arterial CO2

Question 7

How do you calculate the A-a gradient?

Answer 7

PAO2-PaO2

Question 8

what can a widened A-a gradient tell you?

Answer 8

signifies the presence of lung disease (in other words if its normal then the problem is not due to parenchymal lung disease)

Question 9

define hypoxemia

Answer 9

decreased oxygen tension in the circulating blood compared to normal

Question 10

what are the 5 causes of hypoxemia?

Answer 10

Normal A-a difference: decreased, PIO2, Hypoventilation

Widened A-a difference: diffusion limitation, R to L shunt, V/Q mismatch

Question 11

What can a diffusion capacity test tell you?

Answer 11

only that there is a diffusion problem, won’t tell you exactly why

Question 12

normal transit time of rbc in pulmonary capillary

Answer 12

0.75 seconds

Question 13

with normal diffusion capacity how long does it take for a rbc to reach equilibrium with PAO2?

Answer 13

0.25s

Question 14

what are the 2 ways hypoxemia can occur with a diffusion limitation?

Answer 14

1. diffusion capacity severely decreased to <0.25s

Question 15

does abnormal diffusion normally cause hypoxemia at rest?

Answer 15

NO, but can contribute lower PaO2 during exercise

Question 16

How can you treat a suspected diffusion limitation problem?

Answer 16

give 100% FiO2, reverses hypoxemia and normalizes A-a gradient

Question 17

what happens when you give supplemental oxygen to a person with R to L shunt?

Answer 17

hypoxemia does not correct with increased FiO2

Question 18

what is the most common cause of hypoxemia?

Answer 18

V/Q mismatch

Question 19

Does V/Q mismatch correct with supplemental O2?

Answer 19

yes

Question 20

what is the major risk you are taking if you prescribe a long acting beta agonist?

Answer 20

associated w/ increased mortality

Question 21

what are the major mediators of airway inflammation in asthma?

Answer 21

eosinophils
basophils, mast cells
TH2 cells
major basic protein
eosinophilic cationic protein
histamine
LTs, prostaglandins
IgE
vagal affarent, efferent
IL-5, PAF