Acute normobaric hypoxia reduces body temperature in humans

Area of Science:

• Physiology
• Environmental Medicine

Background:

• Anapyrexia, the regulated decrease in body temperature, is observed in various species during hypoxia.
• Understanding human physiological responses to hypoxia is crucial for safety and performance.

Purpose of the Study:

• To investigate the effect of acute normobaric hypoxia on resting rectal temperature (Trec) in adult humans.
• To determine the relationship between blood oxygen saturation (Spo2) and Trec during hypoxic conditions.

Main Methods:

• Ten adult subjects were exposed to normobaric hypoxia (14% and 12% oxygen) and normoxia (21% oxygen) for 30 minutes each.
• Resting rectal temperature (Trec) and blood oxygen saturation (Spo2) were continuously measured under thermoneutral conditions.

Main Results:

• Blood oxygen saturation (Spo2) significantly decreased with lower oxygen concentrations (14% and 12% oxygen).
• Rectal temperature (Trec) progressively lowered during both 14% and 12% oxygen exposures compared to normoxia.
• A significant inverse relationship was found between Spo2 and Trec, with a 0.15°C decrease in Trec for every 1% drop in Spo2.

Conclusions:

• Adult humans exhibit anapyrexia, a regulated decrease in body temperature, in response to acute hypoxia.
• Hypoxia-induced hypothermia is a conserved physiological response across species, including humans.