Gas Exchange

Question 1

Dalton’s law of partial gas pressures

Answer 1

pressure of a gas is directly proprotional to the concentration of it’s molecules

Question 2

How do obtain the dry gas pressure

Answer 2

Fractional concentration (barometric pressure - water vapor pressure)

Question 3

how do you calculate partial pressure

Answer 3

concentration of dissolved gas / solubility coefficient

Question 4

What happens if P1 > P2

Answer 4

gas exchange will take place until equilibiurm is achieved

Question 5

How do anesthetic gases work

Answer 5

they diffuse into blood until the partial pressures in alveoli and blood are equal

Question 6

Fick’s law of diffusion

Answer 6

the amount of gas that moves across a tissue sheet is porportional to the area, but inversely proportional to the thickness

Question 7

How do you calculate diffusion

Answer 7

(change in pressure x area x solubility of gas) / (thickness x square root of (molecule water of gas))

Question 8

blood perfusion through capillaries unde rnormal conditions

Answer 8

rapid rise in blood PO2

Question 9

blood perfusion through capillaries during exercise

Answer 9

as much as 20 times O2 is required

no rapid rise

Question 10

how does diffusing capiacity of O2 change during exercise

Answer 10

increases almost 3 fold

Question 11

atelectasis

Answer 11

collapse of lung tissue, damage to membrane. decreases diffusion because increase in thickenss

Question 12

pneumonia

Answer 12

increases thickness, decreases diffusion

Question 13

pulmonary edema

Answer 13

happens in cardiac problems, can be coughing up pink stuff, very severe

Question 14

pumonary fibrosis

Answer 14

increased thickness, decreases diffusion

Question 15

why is systemic blood PO2 less than pulmonary capillary blood

Answer 15

shunt from bronchial circulation

Question 16

what happens to O2 if blood flow through a tissue is increased

Answer 16

more O2 is transported to the tissue, and PO2 becomes higher

Question 17

What happens to O2 if blood flow through a tissue is decreasd

Answer 17

decreased O2 is transported into the tissue, and the tissue PO2 becomes lower

Question 18

How is CO2 diffusion different from O2 diffusion

Answer 18

opposite direction
much greater diffusion coefficent
much smaller change in partial pressure is needed

Question 19

What happens to CO2 if blood flow through a tissue increases

Answer 19

decreases CO2

Question 20

What happens to CO2 if blood flow through a tissue decreases

Answer 20

increases CO2

Question 21

Lung diffusing capacity

Answer 21

common measurement of lung’s ability to transfer cases.

Question 22

How do you calculate lung diffusing capcity

Answer 22

CO uptake / alveolar PCO2

Question 23

What are some reasons why you would have decreased lung diffusing capcity (DLCO)

Answer 23

emphaysema, pulmonary fibrosis, pulmonary hypertension, chronic pulmonary thromboenbolism, anemia

Question 24

What is a reason why you would have increased lung diffusing capacity (DLCO)

Answer 24

polycythemia

Question 25

What does the alveolar gas equation measure

Answer 25

assess the status of gas exchange and quality of respiratory membrane

Question 26

What is the alveolar gas equation

Answer 26

alveolar partial pressure of O2 = 0.21 (760mmHg - 47 mmHg) - (artieal pressure of CO2 / 0.8)