Lecture 24- Pulmonary gas exchange

Question 1

what element is has the highest composition in both atmospheric pressure and at alveoli saturated with 6.18% water vapor

Answer 1

Nitrogen

Question 2

total pressure exerted by the mixture of non-reactive gases is equal to the sum of the partial pressures of individual gases

Answer 2

dalton’s law

Question 3

for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional

Answer 3

boyle’s law

Question 4

at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid

Answer 4

henry’s law

Question 5

what is the ideal gas law

Answer 5

P= nRT/V

Question 6

what is the partial pressure of O2 at alveolar membrane

Answer 6

150 mm Hg

Question 7

what is the partial pressure of CO2 at alveolar membrane

Answer 7

0.12 mm Hg

Question 8

what is the solubility of oxygen and carbon dioxide and what does this mean

Answer 8

oxygen= 0.024
CO2= 0.57
CO2 is more soluble in water than oxygen and therefore will exert a partial pressure for a given concentration that is less than 1/20th that of oxygen

Question 9

define vapor pressure of water

Answer 9

partial pressure exerted to escape form liquid phase to the gas phase

Question 10

what is the value for vapor pressure at normal body temperature

Answer 10

47 mm Hg

Question 11

what factors affect rate of gas diffusion in a fluid

Answer 11

solubility of gas in fluid
cross-sectional area of the fluid
distance through which the gas must diffuse
molecular weight of gas
temperature of fluid

Question 12

what is the value for the functional residual capacity of the lungs in the average man

Answer 12

2300 ml

Question 13

what is oxygen concentration in the alveoli and its partial pressure controlled by

Answer 13

rate of absorption of oxygen in the blood

rate of new oxygen entry into the lungs (alveolar ventilation)

Question 14

what is carbon dioxide concentration in the alveoli and its partial pressure controlled by

Answer 14

rate of CO2 excretion

alveolar ventilation

Question 15

what happens to alveolar PCO2 as alveolar ventilation increase

Answer 15

it decreases

Question 16

what happens to alveolar PCO2 as rate of excretion increases

Answer 16

it increases

Question 17

what factors determine how rapidly gas will pass through the respiratory membrane

Answer 17

membrane thickness
membrane surface area
diffusion coefficient of gas in the substance of the membrane
partial pressure difference of gas between the 2 sides of the membrane

Question 18

define ventilation-perfusion ratio

Answer 18

alveolar ventilation/blood flow

Question 19

what is the normal Va/Q

Answer 19

0.8

Question 20

where is gas exchange completed during normal ventilation

Answer 20

initial 1/3 of capillary

Question 21

what happens to blood gas composition when there is an airway obstruction

Answer 21

it remains unchanged

Question 22

what happens to alveolar gas composition when there is a vascular obstruction and why

Answer 22

it does not change because there is no blood contact (creating a physiologic shunt)

Question 23

what is the normal alveolar perfusion for PO2 and PCO2

Answer 23

PO2= 104mm Hg
PCO2= 40 mm Hg

Question 24

what are the alveoli partial pressure of O2 and CO2 when Va/Q is infinity

Answer 24

O2= 149mm Hg
CO2= 0 mm Hg