Gas Laws

Question 1

capacity

Answer 1

the sum of 2 or more volumes

Question 2

factors influencing total lung capacities

Answer 2

body size

age

gender

race

Question 3

describe the spirometry curves and name the major measurements of breathing

Answer 3

Question 4

ideal gas law

Answer 4

relates the pressure (P), volume (V), and temperature (T) of a gas to the number (n) of moles of gas by a proportionality factor, the gas constant (R)

PV = nRT

Question 5

standart temperature and pressure

Answer 5

1 atm and 0 degrees C

Question 6

volume of one mole of any gas at standard temperature

Answer 6

22.4 liters

Question 7

Dalton’s law

Answer 7

gas species in a mixture act independentl to exert a partial pressure (P) equal to the pressure this same gas would exert if it occupied the total volume of the gas mixture in the absence of other components

P_B = P_N2 + P_O2 + P_CO2 + P_H2O

P_B is barometric pressure

Question 8

P_O2 in dry atmospheric air at 760 mmHg barometric pressure

Answer 8

159 mmHg

Question 9

P_O2 in air saturated with water vapor at 37 degrees C and 760 mmHg

Answer 9

149 mmHg

Question 10

typical values for adult residual volume, functional residual capacity

Answer 10

RV = 1500

FRC = 3000

TLC = 6000

Question 11

Why do RV and FRC increase with age, but TLC doesn’t?

Answer 11

Decreased lung elastic tissue - increased compliance (i.e. less lung recoil)

Question 12

Helium dilution

Answer 12

helium at a known concentration and volume in the spirometer is brought into equilibrium with the lung

based on concentration measurements, the capacity of the lung can be measured

V_lung = V_spirx [([He]_initial/[He]_final) - 1]

Question 13

fraction gas concentrations in dry room air

Answer 13

1.0 = F_N2 + F_O2 + F_CO2

Fg = Pg/P_B

F_N2 = 0.78

F_O2 = 0.21

F_CO2 = 0.0003

Question 14

oxygen fraction equation

Answer 14

FO2 = P_O2/(P_B - P_H2O)

Question 15

BTPS

Answer 15

body temperature, ambient pressure, and saturated with water vapor

volumes of ventilated gases are expressed in BTPS conditions

Question 16

STPD

Answer 16

standard temperature (0 degrees C or 273 degrees K)

standard pressure (760 mmHg)

dry (no water vapor present)

metabolic rates are expressed by gas volumes in STPD conditions since volumes at STPD are directly related to the number of millimoles of oxygen consumed or carbon dioxide produced (22.4 mL per mmole)

Question 17

ATPS

Answer 17

ambient temperature, ambient pressure and saturated with water vapor

many respiratory variables are measured in ATPS conditions and must be converted to BTPS or STPD conditions as appropriate

Question 18

Henry’s Law

Answer 18

relates the concentration (C) of a gas in solution to its partial pressure

Cg = K*Pg

where Cg = concentration of dissolved gas, K = proportionality constant (termed the solubility coefficient) for the dissolved gas, Pg = partial pressure of the gas

Question 19

determinants of diffusion of gases across media

Answer 19

when diffusion occurs between different media, gas diffuses down the potential graident that is most closely related to its partial pressure gradient, not necessarily down a concentration gradient

Question 20

convection

Answer 20

transmission of energy or mass by a medium involving movement of the medium itself

the circulatory movement that occurs in a fluid at a non-uniform temperature owing to the variation of its density and the action of gravity