### Description

The air in the alveoli is at body temperature and saturated with water. Air in the environment is usually at a different temperature and has a lower water saturation. Thus as a person breaths there is a loss of water from the body which is termed the humidity deficit.

water content in mg/L at °C outside the body =

= (relative humidity in percent) * (absolute humidity at °C when saturated) / 100%

water content in mg/L at °C in the alveoli =

= (absolute humidity at °C when saturated)

humidity deficit in mg/L =

= (water content in mg/L in alveoli) - (water content in mg/L in environment)

water loss in mg per minute of quiet breathing =

= (tidal volume in liters per breath) * (breaths per minute) * (humidity deficit in mg/L)

water loss in mL per day =

= (water loss in mg per minute) * 1440 / 1000

The higher the humidity of the inspired air, the lower the humidity deficit.

 Temperature in °C Absolute Humidity in mg/L Air When Saturated 19 16.3 20 17.3 21 18.4 22 19.4 23 20.6 24 21.8 25 23.0 26 24.4 27 25.8 28 27.2 29 28.8 30 30.4 31 32.0 32 33.8 33 35.6 34 37.6 35 39.6 36 41.7 37 43.9 38 46.2 39 48.6 40 51.1 41 53.7

If the data in the first 2 columns is analyzed with JMP:

absolute humidity of air when saturated at a given temperature =

= (0.03838 * ((temperature in °C)^2)) - (0.62339 * (temperature in °C)) + 14.521

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