Diffusion

Question 1

What is Dalton’s Law?

Answer 1

To find the pressure of a gas, multiply the total amount of gas times the fractional concentration of that gas.

Question 2

What is the PiO2 in the trachea?

Answer 2

149mmHg

Question 3

Why does the PO2 lower in the alveoli?

Answer 3

There is a mixing with other gases such as CO2 and O2 is removed at a greater rate than CO2

Question 4

What is the alveolar PCO2?

Answer 4

40mmHg

Question 5

What is the alveolar gas equation?

Answer 5

PAO2= PiO2- (PaCO2/ R)

R exchange ration (VCO2/VO)

Question 6

What is Henry’s law?

Answer 6

Concentration of gas is proportional to partial pressure and solubility

Question 7

Which gas has a higher solubility?

Answer 7

CO2

Question 8

Which gas has a lower solubility?

Answer 8

O2

Question 9

What is the pulmonary arterial PO2?

Answer 9

0.3mL / 100mL 40mmHg

Question 10

What is the venous PCO2?

Answer 10

3.1mL/ 100mL 46mmHg

Question 11

What is the alveolar PO2?

Answer 11

100mmHg

Question 12

What does Henry’s law say?

Answer 12

The concentration of gas is proportional to partial pressure and solubility

Question 13

What does Boyle’s law state?

Answer 13

P1V1=P2V2 This helps us understand the movement of air during inspiration and expiration

Question 14

What happens during inspiration?

Answer 14

Diaphragm descends and the volume increases, The alveolar pressure is now below atmospheric pressure and this gradient draws breath into the lungs. (negative pressure)

Question 15

What happens during expiration?

Answer 15

The lung recoils (which is passive) and the volume decreases the pressure in the lungs was higher than the atmospheric so air moves out (Positive pressure)

Question 16

Why does O2 require more driving pressure than CO2?

Answer 16

It is less soluble

Question 17

Gas move down what gradient?

Answer 17

Pressure not concentration

Question 18

Describe the diffusion of O2.

Answer 18

The solubility of O2 is low, but the driving pressure or the pressure gradient across the alveolar membrane to the pulmonary artery is very high so diffusion happens fast. It takes about 0.25 secs and at rest blood is in the capillary for about 0.75 s

Question 19

What happens to diffusion in diseased lungs?

Answer 19

The surface area decreases and the thickness increases. Blood is only in the capillaries for long and now it takes longer to diffuse so the blood leaving now has a lower PO2 than the alveoli

Question 20

What happens to diffusion during exercise?

Answer 20

Blood flow and cardiac output increase significantly and the time spent in the capillary goes down. The RBC become the limiting factor

Question 21

Describe the diffusion of CO2.

Answer 21

CO2 has a very high solubility but the pressure gradient is much less than that of PO2. There is less driving force, but it more easily diffuses across the membrane. Equilibration takes about the same amount of time that O2 does.

Question 22

What is the lung diffusing capacity equation?

Answer 22

1/Dl= 1/Dm + 1/ (O x Vc)
Dm- membrane properties
O- Rxn rate with hemoglobin
Vc- volume of capillary blood