Final: Lecture 24

Question 0

Boyle’s Law

Answer 0

•For a fixed amount of an ideal gas kept at fixed temp, pressure and volume are INVERSELY proportional

Question 1

Dalton’s Law

Answer 1

•Total pressure exerted by the mixture of non-reactive gasses is equal to the sum of the partial pressures of individual gasses

Question 2

Henry’s Law

Answer 2

•At constant temp, 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

Question 3

Ideal Gas Law

Answer 3

•P = nRT/V

Question 4

Pressure is ________ proportional to the concentration of the gas molecules.

Answer 4

•Directly

Question 5

Rate of diffusion is _______ proportional to pressure caused by that gas alone.

Answer 5

•Directly

Question 6

Partial pressure of O2 at alveolar membrane is ___. CO2 is ___.

Answer 6

• 150 mm Hg

* .21 mm Hg

Question 7

Vapor Pressure

Answer 7

• Of water is the partial pressure exerted to escape from the liquid phase to the gas phase.f
• At normal body temp (37º C) this vapor pressure is 47 mm Hg
• Vapor pressure of water depends on the temp

Question 8

Factors that affect rate of gas diffusion in a fluid

Answer 8

• Solubility of gas in the fluid
• Cross-sectional area of fluid
• Distance through which the gas must diffuse
• Molecular weight of gas
• Temp of fluid (remains reasonably constant)

Question 9

Alveolar Air Replacement

Answer 9

• Residual capacity of lungs is 2300 ml, only 350 ml of new air brought into alveoli with each normal inspiration
• Same amount of old alveolar air is expired
• Therefore volume of alveolar air replaced by new is only 1/7th, so multiple breaths are required to exchange most of the alveolar air

Question 10

Oxygen concentration in the alveoli, as well as its partial pressure, is controlled by?

Answer 10

• Rate of absorption of oxygen into blood
• Rate of new oxygen entry into the lungs (alveolar ventilation)
• To quadruple oxygen consumption, alveolar ventilation must also quadruple

Question 11

CO2 concentration in the alveoli, as well as its partial pressure, is controlled by?

Answer 11

• Rate of CO2 excretion, alveolar pCO2 increases in direct proportion to rate of excretion
• Alveolar ventilation: alveolar pCO2 decreases in inverse proportion to alveolar ventilation

Question 12

Factors that determine how rapidly a gas will pass through the respiratory membrane:

Answer 12

• Membrane thickness
• Membrane surface area
• Diffusion coefficient of gas in the substance of the membrane
• Partial pressure difference of gas between the two sides of the membrane

Question 13

Any factor that increases membrane thickness (i.e. edema or fibrosis) to more than 2x or 3x normal can interfere with?

Answer 13

•gas exchange*

Question 14

Ventilation-perfusion ratio

Answer 14

• = Va/Q = alveolar ventilation/blood flow

* Va/Q - 0.8

Question 15

Va/Q = 0 when Va = 0 but there is still perfusion:

Answer 15

• Due to airway obstruction (i.e. mucus plug)

* Blood gas composition remains unchanged

Question 16

Va/Q = infinity when Q = 0 but there is still ventilation (no gas exchange):

Answer 16

• Due to vascular obstruction (i.e. pulmonary embolism)

* Alveolar gas composition remains unchanged b/c there is no blood contact. This creates a physiologic shunt.

Question 17

Shunted blood is…

Answer 17

• Whenever Va/Q is below normal a certain fraction of the venous blood passing through the pulmonary capillaries does not become oxygenated
• Greater the physiologic shunt, greater the amount of blood that fails to be oxygenated