PSC1002/L16 Gas Exchange

Question 1

Define ventilation.

Answer 1

The exchange of air between the atmosphere and lungs

Question 2

Define alveolar ventilation.

Answer 2

The movement of air in and out of alveoli

Question 3

Define anatomic dead space.

Answer 3

Volume of the conducting airways

Question 4

Define physiologic dead space.

Answer 4

Anatomic dead space & alveolar dead space

Question 5

Define alveolar dead space.

Answer 5

In unhealthy or elderly people, not all alveoli function properly
I.e., they are insufficiently perfused and not all O2 and CO2 is exchanged

Question 6

Define pulmonary ventilation with an equation.

Answer 6

TPV = ventilation rate x tidal volume

Question 7

What is movement of gas directly proportional to? (3)

Answer 7

Pressure gradient of gas
Solubility of gas in liquid
Temperature

Question 8

Define Dalton’s Law.

Answer 8

The total pressure exerted by a mixture of gases is equal to the sum of the pressure exerted by the individual gases

Question 9

How does the composition of alveolar air compare to air at sea level? (4)

Answer 9

Little change in N2
Decreased O2
Increased CO2
Increased H2O

Question 10

Define Henry’s Law.

Answer 10

At constant temperature, the amount of a gas that dissolves in a liquid depends on the solubility of the gas in the liquid and the partial pressure of the gas.

Question 11

At identical partial pressures, how much more CO2 would be dissolved than O2?

Answer 11

20x

Question 12

Give 2 characteristics of pulmonary circulation.

Answer 12

Low pressure system
High flow

Question 13

What is the equation for flux?

Answer 13

Flux = (P x DeltaC)/X

Question 14

How does hyperventilation affect PPO2 and PPCO2?

Answer 14

PPO2 increased
PPCO2 decreased

Question 15

How does hypoventilation affect PPO2 and PPCO2?

Answer 15

Decreased PPO2
Increased PPCO2

Question 16

Describe hyperbaric oxygen therapy. (2)

Answer 16

Person placed in chamber with high PO2
Leads to increased PAO2 levels and O2 exchange

Question 17

Give a condition that can be treated using hyperbaric oxygen therapy.

Answer 17

Severe blood loss
Crush injuries
Anemia
Chronic wounds
Certain infections
Burns
Recovery

Question 18

Describe decompression sickness and how it is alleviated with hyperbaric oxygen therapy. (2)

Answer 18

Caused by dissolved gases in blood coming out of solution and forming bubbles in bloodstream
Therapy forces gases back into solution, eliminating bubbles

Question 19

Give 3 pathological changes which adversely affect gas exchange.

Answer 19

Decrease in SA
Increased thickness of alveolar membrane
Increased diffusion distance

Question 20

What factors can influence alveolar ventilation? (3)

Answer 20

Posture
Rate of inspiration
Amount of air inspired

Question 21

Give 3 factors that influence lung perfusion.

Answer 21

Hydrostatic pressure in pulmonary arteries
Pressure in pulmonary veins
Alveolar air pressure

Question 22

What is V/Q mismatch? (2)

Answer 22

When alveolar ventilation (VA) does not match Q (lung perfusion)
Blood is shunted from right to left side of heart without adequate oxygenation