Session 7 Physical Principles of Gas Exchange

Question 1

Room air gasses and percentages

Answer 1

Oxygen 21%

Nitrogen 79%

Question 2

What type of energy provides the source for the diffusion process

Answer 2

Kinetic Energy

Question 3

Movement of gas in one direction is the effect of…

Answer 3

concentration gradient

Question 4

Rate of diffusion is dependent on _________.

Answer 4

pressure

Question 5

total pressure commonly used

Answer 5

1 atmosphere (weight of a column of air a mile high)
760 mmHg

Question 6

The colder the liquid the ________ gas it can absorb.

Answer 6

more

Question 7

Henry’s Law

Answer 7

solubility of a gas in a liquid depends on temperature, the partial pressure of the gas over the liquid, the nature of the solvent, and the nature of the gas.

Question 8

Carbon dioxide is ____________more soluble than oxygen.

Answer 8

20 times

Question 9

Rate of net diffusion os determined by

Answer 9

difference of partial pressures (pp)

Question 10

If pp of gas in alveoli > blood then gas moves into ________.

Answer 10

blood

oxygen

Question 11

If pp of gas in blood > alveoli then gas moves into

Answer 11

alveoli

Carbon Dioxide

Question 12

Partial pressure of water escaping surface into gas phase = vapor pressure. Vapor pressure is _______ when a gas mixture is fully humidified at 37degrees C

Answer 12

47 mmHg

Question 13

With vapor pressure considered, what is the remaining total pressure of gases in the air?

Answer 13

713 mmHg

760 mmHg - 47 mmHg (vapor pressure)

Question 14

What factors affect gas diffusion rates in fluids?

Answer 14

Pressure differences
Gas solubility in fluid
area of fluid
distance which gas must diffuse
molecular weight of gas
Temperature of fluid (constant in body)

Question 15

D is directly proportional to

Answer 15

solubility

Question 16

D is inversely proportional to

Answer 16

the square root of the gas’ molecular weight

Question 17

Rate of gas movement into tissues is limited by diffusion rate of gas through _________.

Answer 17

tissue water

Question 18

How much alveolar air is replaced per breath?

Answer 18

350 ml

Question 19

FRC is roughly how many ml?

Answer 19

2500 ml

(Each breath replaces a seventh of the FRC

Question 20

Normal Alveolar PO2 is

Answer 20

100 mmHg

Question 21

Normal Alveolar PCO2 is

Answer 21

40 mmHg

Question 22

What affects alveolar PO2?

Answer 22

rate of ventilation
oxygen pressure
exercise

Question 23

Expired air is a combination of

Answer 23

Dead space

Alveolar air

Question 24

Alveolar air is expired at _____________.

Answer 24

end exhalation

Question 25

Overall thickness of respiratory membrane?

Answer 25

0.6 micrometers

Question 26

Total surface area of respiratory membrane

Answer 26

70 square meters

Question 27

Fick's Law

Answer 27

Diff. = (A * change pp * D)/T A is cross sectional area of membrane change pp = the driving pressure (partial pressure difference D is the gas coefficient T is the tissue thickness or length through membrane

Question 28

With regard to surface area, Emphysema causes the dissolution of many alveolar walls to coalesce alveoli into larger chambers. This can decrease surface area as much as __________. Does this increase or decrease the diffusion rate?

Answer 28

5 fold | decreases (r/t decreased surface area on which to diffuse)

Question 29

CO2 diffuses _______ than oxygen.

Answer 29

20 times faster

Question 30

Oxygen diffuses __________ as nitrogen

Answer 30

twice as fast

Question 31

Diffusion Coefficient is affected by

Answer 31

Solubility | molecular weight

Question 32

Diffusion capacity deals with

Answer 32

how easily a gas can move across a membrane in quantitative terms.

Question 33

Oxygen diffusion capacity during exercise is increased r/t several factors:

Answer 33

Recruitment of capillary fields | Better ventilation/perfusion (V/Q) match (All Zone 3)

Question 34

CO2 has ___________ concentration differences between blood and alveoli.

Answer 34

``` minimal very soluble difficult to measure CO2 diffusion capacity Alveoli - 40 mmHg Blood - 46 mmHg ```

Question 35

When ventilation = zero but perfusion is present, what is the V/Q

Answer 35

Zero | blockage in airway

Question 36

If ventilation present but no perfusion, then V/Q=

Answer 36

infinity | ex: pulmonary embolism

Question 37

If V/Q is either zero or infinity, there is _______ exchange of gases

Answer 37

no exchange of gases

Question 38

In normal deoxygenated blood, the PO2 is____ and the PCO2 is _____.

Answer 38

``` PO2 = 40 mmHg PCO2 = 45 mmHg ```

Question 39

PP of gases in the Alveoli ___________ the PP of gases in the pulmonary vein

Answer 39

exactly match | 100mmHg PaO2, 40 mmHg PaCO2

Question 40

Shunt

Answer 40

perfusion without ventilation | V/Q is below normal

Question 41

Shunt blood is/is not oxygenated?

Answer 41

is not oxygenated

Question 42

Physiologic shunt is

Answer 42

total amount of shunted blood per minute

Question 43

Physiologic dead space

Answer 43

``` V/Q is greater than normal Ventilation but no perfusion wasted ventilation anatomical dead space (ventilated air does not reach blood) has to do with embolism in pulmonary circulation ```