Gas Laws Flashcards
capacity
the sum of 2 or more volumes
factors influencing total lung capacities
body size
age
gender
race
describe the spirometry curves and name the major measurements of breathing
ideal gas law
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
standart temperature and pressure
1 atm and 0 degrees C
volume of one mole of any gas at standard temperature
22.4 liters
Dalton’s law
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
PB = PN2 + PO2 + PCO2 + PH2O
PB is barometric pressure
PO2 in dry atmospheric air at 760 mmHg barometric pressure
159 mmHg
PO2 in air saturated with water vapor at 37 degrees C and 760 mmHg
149 mmHg
typical values for adult residual volume, functional residual capacity
RV = 1500
FRC = 3000
TLC = 6000
Why do RV and FRC increase with age, but TLC doesn’t?
Decreased lung elastic tissue - increased compliance (i.e. less lung recoil)
Helium dilution
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
Vlung = Vspirx [([He]initial/[He]final) - 1]
fraction gas concentrations in dry room air
1.0 = FN2 + FO2 + FCO2
Fg = Pg/PB
FN2 = 0.78
FO2 = 0.21
FCO2 = 0.0003
oxygen fraction equation
FO2 = PO2/(PB - PH2O)
BTPS
body temperature, ambient pressure, and saturated with water vapor
volumes of ventilated gases are expressed in BTPS conditions
STPD
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)
ATPS
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
Henry’s Law
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
determinants of diffusion of gases across media
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
convection
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
