Gaseous Diffusion & Transport I #1

Question 1

What is FO2 + PO2?

Answer 1

• FO2: franctional conc/% of O2 = 0.21/21%

- PO2 = partial P of O2

Question 2

What is PB?

Answer 2

Barometric (atmospheric) P

Question 3

What is PIO2 + FIO2?

Answer 3

• PIO2: PO2 in inspired gas (usually in trachea)

- FIO2: FO2 in inspired gas

Question 4

What is PAO2 + FAO2?

Answer 4

• PAO2: PO2 in alveoli

- FAO2: FO2 in alveoli

Question 5

What is PaO2 + FaO2?

Answer 5

• PaO2: PO2 in arteries

- FaO2: FO2 in arteries

Question 6

List the common P + SI units

Answer 6

• common P: mmHg

- SI: kPa

Question 7

What is dead space?

Answer 7

airway vol with no gas exchange

Question 8

What is anatomic dead space?

Answer 8

all resp tract except alveoli + resp bronchioles

Question 9

What is physiologic dead space?

Answer 9

all anatomical areas + areas where gas exchange dysfunctional

Question 10

What is Dalton’s law?

Answer 10

PP of gas in mix is P it would exert if occupied the vol alone

Question 11

What is the total P of air?

Answer 11

• is gas mix

- total P of all gases in it = PB

Question 12

What is PB made up of?

Answer 12

PO2 + PCO2 + PN2 (includes all inert gases) + PH2O

Question 13

How can calc PP of a gas?

Answer 13

fractional conc x PB

Question 14

What is PB at sea level?

Answer 14

101 kPa (760mmHg)

Question 15

What is FO2 (in dry air)?

Answer 15

• all H2O vapour removed

- 0.209 / 21%

Question 16

How do you calc dry PO2?

Answer 16

FO2 = 0.209 x PB = 101

= 21kPa (159mmHg)

Question 17

How does PB change at altitude?

Answer 17

red e.g. to 33kPa on top of Everest

Question 18

How does FO2 change at altitude?

Answer 18

unchanged but P it exerts changes

Question 19

How does PIO2 change at altitude + consequence?

Answer 19

• PIO2 (= FIO2 X PB) falls progressively with inc altitude when breathing air
• need supplemental O2 to inc FIO2 to compensate for dec PB

Question 20

What happens as PP of gas e.g. CO2 above liquid is increased?

Answer 20

• the more the gas will dissolve in the liquid

- so need to inc PP of gas to get it to dissolve

Question 21

What happens when P released from liquid?

Answer 21

• less gas held in sol

- bubbles of gas will rise from liquid bc they’re no longer dissolved

Question 22

What does the amount if gas dissolved in liquid depend on when given PP applied?

Answer 22

sol of gas in liquid

Question 23

What happens to gas in a flask filled partially with liquid?

Answer 23

• if gas dissolved in liquid - exerts PP + so leave surface of liquid until PP of gas in liquid = P of gas in gas phase
• if gas was already in gas phase, move into liquid in same way until both P are equal + reach P equ

Question 24

What is the PP of X gas in gas equal to in the flask?

Answer 24

PP of X gas in liquid

Question 25

At equ, how much gas is in liquid in the flask?

Answer 25

- depends on sol of gas in liquid - gas with low sol dissolve poorly in liquid even at high PP - content of gas in liquid low even though PP might be high

Question 26

How can you inc content of gas in liquid?

Answer 26

- need to inc sol (can't bc its constant) so need to inc PP

Question 27

What is gas transfer between diff phases e.g. gas + liquid, blood + fat, alv + cap etc determined by?

Answer 27

PP gradient not conc gradient

Question 28

What does the PP of gas in liquid depend on?

Answer 28

- conc of gas mol in liquid (ml/ml or mmol/l) | - sol of gas in liquid

Question 29

What is Henry's law?

Answer 29

content of gas (ml/l) in liquid = sol (ml/l/kPa) x PP (kPa)

Question 30

What is difference between high + low sol gas in liquid?

Answer 30

- high sol: not going to exert much PP - low sol: need high PP as its fighting to escape - less sol gas has high PP, more sol gas has low PP

Question 31

What does H2O vapour P (PH2O) depend on?

Answer 31

- temp | - sat

Question 32

How does sat H2O vapour P change?

Answer 32

rises with inc temp

Question 33

What does % sat H2O vapour depend on?

Answer 33

how much H2O air has been in contact with

Question 34

What happens to air as it enters the lungs?

Answer 34

passes over moist surfaces + becomes 100% sat

Question 35

Why is H2O vapour P in lungs constant?

Answer 35

Alveolar temp constant bc body temp constant (37 degrees) + H2O vapour P depends on temp

Question 36

What is PIO2 + how is it calc?

Answer 36

= PO2 of moistened inspired air at end of trachea | = (PB - 6.3) x 0.209 kPa or (PB - 47) x 0.209 mmHg

Question 37

Why can't measure PAO2 directly?

Answer 37

- CO2 diffuses into alveolus to replace O2 diffusing into pul cap - if 1 mol of CO2 prod for each mol of CO2 used then PAO2 = PIO2 - PACO2

Question 38

What is the alveolar gas equation?

Answer 38

PAO2 approx PIO2 - PACO2/R bc more O2 used than CO2 prod

Question 39

What is resp quotient?

Answer 39

- CO2 prod/O2 consumption | - usually 0.8

Question 40

What inc diff between alveolar + inspired O2?

Answer 40

inc CO2

Question 41

Why does PO2 inc when overbreathe?

Answer 41

PACO2 dec