10. CP Gas Exchange

Question 1

What is the average value for perfusion?

Answer 1

5L / min

Question 2

What disease can increase the distance factor in the perfusion equation?

What does this do to perfusion?

Answer 2

Interstitial lung disease

Question 3

Is the diffusion coefficient for CO2 higher or lower than O2?

Answer 3

CO2’s diffusion coefficient is much higher (20x) than that of O2

Question 4

What is the pressure difference between alveolar O2 and the O2 in the capillaries?

Answer 4

60 mmHg

Question 5

Why do you see exercise intolerance in lung disease before you see resting hypoxia?

Answer 5

Because a given RBC spends exactly as much time in the lungs during exercise as it needs to pick up its full complement of oxygen and no more. Any damage to the perfusion means that the RBC cannot fully absorb O2 in the lungs before returning to the periphery.

Question 6

What is the average diffusion capacity of the lung for oxygen?

Answer 6

21ml O2 / min / mmHg at rest

Question 7

What is the correction factor for the diffusion constant of O2 vs that of CO?

Answer 7

DL_O2 = 1.23 DL_CO

Question 8

What is the purpose of surfactant?

How does it account for alveoli of different sizes?

Answer 8

Reduces surface tension to prevent collapse of the alveoli

It reduces tension in small alveoli more than in larger alveoli

Question 9

What is surfactant made of?

Answer 9

A phospholipid (Dipalmitoylphosphatidylcholine)

Surfactant proteins (SPA, SPB, SPC, SPD)