Gas Exchange

Question 1

Boyle’s law

Answer 1

P1V1 = P2V2

Question 2

Dalton’s law of partial pressures
Corrected for humidified gas

Answer 2

The pressure of each individual gas in a mixture is independent of all the others.

Px = barometric pressure x fractional concentration
Po2 = (760mmHg - water vapour pressure (47)) x 0.21

Question 3

Venous, arterial, alveolar, and atmospheric pressures of O2

Answer 3

40; 100; 105;160

Question 4

Venous, arterial, alveolar, and atmospheric pressures of CO2

Answer 4

46; 40; 40; 0.3

Question 5

Henry’s Law

Answer 5

the amount of gas dissolved in liquid is directly proportional to the partial pressure at equilibrium.
More soluble -> greater concentration
Cx = Px solubility

Question 6

Fick’s Law

Answer 6

Volume of gas transferred per unit of time
Vx = Area x Diffusion coefficient x ΔP / Thickness

Question 7

Lung diffusing capacity

Answer 7

Measures diffusion barrier of the alveolar-capillary membrane. Single breath method using CO.
Decreases with emphysema, fibrosis, and anemia. Increases with exercise as more capillaries are recruited.

Question 8

O2 diffusion across different altitudes

Answer 8

PAo2 drops from 100mmHg to 50mmHg

Question 9

O2 diffusion, normal vs fibrosis

Answer 9

Normal has a linear increase in PaO2 along the pulmonary capillary, fibrosis is much slower and cannot reach to the same extent.
Reaches PAo2 as 80 compared to 100 normal.