Alveolar Gas Equation (AGE)
Info
Patient Age
pCO(2)
unit mmHg Kpa
FIO2
unit % Fraction
pAtm
unit mmHg Kpa
pH(2)O
unit mmHg Kpa
RespQ
R e s u l t s
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Alveolar Gas in mmHg
 
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Alveolar Gas Equation (AGE)

The alveolar gas equation is usually used to calculate the partial pressure of oxygen in the alveoli. It is frequently used in evaluation of lung disease

Formula used:

Alveolar Gas= [(pAtm-pH2O)xFiO2]-pCO2/RespQ

Where,

  • pAtm = Atmospheric pressure [mmHg] (760mmHg at sea level)
  • pH2O = Partial Pressure of Water [mmHg] (47mmHg at 37 deg C)
  • FiO2 = % of Oxygen inspired (21% with room air)
  • RespQ = Respiratory Quotient (approx 0.8, depends on food intake)
  • pCO2 = Arterial CO2 measured [mmHg]

References:

  1. Mellemgaard, K. The alveolar-arterial oxygen difference: its size and components in normal man. Acta Physiol Scand . 1966;67(1):10-20.
  2. Kanber GJ, King FW, Eshchar YR, et al. The alveolar-arterial oxygen gradient in young and elderly men during air and oxygen breathing. Am Rev Respir Dis . 1968;97(3):376-81.