partial pressure of oxygen in mm Hg in inspired air =
= (per cent concentration of oxygen in the inspired air) * ((barometric pressure) - (water vapor pressure)) / 100
= (fractional concentration of oxygen in the inspired air) * ((barometric pressure) - (water vapor pressure))
where:
• The barometric pressure is normally 760 mm Hg at sea level.
• Water vapor pressure is normally 47 mm Hg at 37 °C.
• The per cent concentration of oxygen in room air is about 21%.
Equations for Water Vapor Pressure and Temperature
water vapor pressure in mm Hg =
= 47.07 * (10 ^ ((6.36 * ((temperature in °C) - 37)) / (232 + (temperature in °C))))
where:
• temperature is in Centigrade from 0 to 40 °C
water vapor pressure in mm Hg =
= (10 ^ ((0.0244 * (temperature in °C)) + 0.7655)) + 0.4
Equations for Barometric Pressure and Altitude
barometric pressure in mm Hg =
= 760 * ((1 - (6.873 * (10 ^ (-6)) * (altitude in feet))) ^ 5.256)
where:
• altitude is in feet above sea level
