Diffusion-Scharf

Question 1

What is the diffusion constant in Fick’s law?

Answer 1

D is proportional to the solubility and square root of the molecular weight

Question 2

Which gradient dictates movement of a gas across a membrane?

Answer 2

Partial pressure, not concentration (content) gradient.

Question 3

What is the diffusivity (D) ratio of CO2 and O2

Answer 3

20/1

Question 4

What is the most notable perfusion limited gas?

Answer 4

N2O (poor solubility in blood, PP easily reached)

Question 5

What is the most notable diffusion limited gas?

Answer 5

CO

Question 6

How does PO2 change in high altitude (or any low PP of O2)?

Answer 6

Small PO2 gradient because alveolar pressure will decrease but venous pressure also decreases less so difference not as big.

Question 7

Technique for measuring CO diffusion capacity

Answer 7

Inhale CO+He and hold for 10s, breathe out, throw away dead space, and measure capacity in mL/min.

Question 8

What are the two components of CO diffusion?

Answer 8

Membrane: path from alveolus to Hgb (Dm), 2. Binding to hemoglobin (Theta*Vc)

Question 9

How does DL conductance relate to the two components?

Answer 9

1/DL=1/Dm+1/theta*Vc because 1/conductance is resistance. Linear relationship with slope is 1/theta*Vc and 1/Dm is the y intercept.

Question 10

What is mixed venous and arterial PCO2?

Answer 10

venous-45, arterial and alveolar-40