Tags | |
This equation is represented by the following expression: PaO2=FInO2(PATM–PWV)–(PaO2R) and computes the partial pressure of alveolar oxygen.
The alveolar gas equation calculates the partial pressure of oxygen in the pulmonary alveoli. The pulmonary alveolar partial pressure is then typically used to calculate the alveolar-arterial gradient of oxygen.
The following are the inputs to the Alveolar Gas Equation:
- PaO2 = alveolar partial pressure of O2
- FInO2= O2in inspired air
- PaCO2= parterial partial pressure of CO2
- RQ = respiratory quotient
- PATM = barometric pressure (normally 760 mmHg)
- PWV = water vapor pressure (normally 47 mmHg)
The alveolar partial pressure is typically given in kPa.
Notes
With a little more information on the input variables, the user can figure out how to either obtain these from data or search for a further explanation of how to ddefine the input values.
EQUATION INPUTS
Respiratory Quotient (RQ): The term in this equation for the respiratory quotient (R) is calculated from the ratio of CO2 removed from the body to the O2 inspired:
R=CO2 eliminated / O2 consumed
In this ratio, the CO2 and O2 are in the same units and expressed in quantities proportional to the number of molecules, such as gas volumes at STP or moles. See the vCalc equations for Respiratory Quotient [STP] and the Respiratory Quotient [moles].
Inspired Oxygen (FInO2): This term represents the fractional percentage of oxygen in the air breathed in.
Partial Pressure of CO2 (PaCO2) : The arterial partial pressure of carbon dioxide
Atmospheric Pressure (PATM): This term is the local air pressure typically recorded in mmHg.
Water Vapor Pressure (PWV): This term is the saturated vapour pressure of water at body temperature and the prevailing atmospheric pressure
