What body temperature is used as a reference for the isothermic saturation boundary?

The isothermic saturation boundary (ISB) refers to the temperature at which inspired gas reaches the temperature of the body and becomes fully saturated with water vapor. The standard body temperature used as a reference for this boundary is 37 degrees Celsius, which is considered the average core temperature of a healthy human.

At this temperature, the airways in the respiratory system are typically assumed to achieve saturation at a relative humidity of 100%. This is crucial for effective gas exchange in the lungs, as adequately warmed and humidified air helps prevent damage to the respiratory mucosa and facilitates optimal oxygen absorption.

Other temperatures mentioned, such as 35, 39, and 40 degrees Celsius, do not represent the standard physiological reference for the ISB, which is anchored at 37 degrees Celsius due to its relevance to human body function and the normal conditions under which gas exchange occurs.