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
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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