Diffusion

Question 1

Diffusion rate of a gas is proportional to

Answer 1

Area/thickness x Diff constant x (P1-P2)

Question 2

Diffusion constant =

Answer 2

Solubility / sqrt(MW)

CO2 diffuses 20x faster than O2

Thus patients develop problems in O2 diffusion before CO2 retention

Question 3

Uptake rates of NO2, O2, and CO under normal conditions

Answer 3

NO2 > O2&raquo_space;» CO

Question 4

CO is ? Limited

Answer 4

Diffusion limited

Not all the CO from the alveoli gets into the blood in time

Question 5

N2O is ? Limited

Answer 5

Perfusion limited

Does not combine with Hg

So immediately equilbriates with the blod and Pressures in alveolar and artery are about the same

Question 6

What is P-O2 entering the capillary

Answer 6

40mmHg

Question 7

Blood and alveolar P-O2 are about the same until

Answer 7

0.25 seconds

Question 8

O2 uptake in normal vs. disease patients with exercise

Answer 8

Normal = no fall in end capillary P-O2

Disease = O2 uptake becomes diffusion-limited (usually perfusion-limited)

Question 9

Normal diffusing capacity of the lungs

Answer 9

About

25mL/min-mmHg

Question 10

The two components of diffusion

Answer 10

Crossing the membrane

Reaction with Hgb

1/D-l = 1/D-m + 1/(theta*V-c)

Theta = rate of CO and O2 combination with 1mL of blood per mmHg

V-c = volume of capillary blood

Theta*V-c = diffusing capacity of the rate of gas binding to Hgb

1/above = resistance of reaction