Hypercapnia effect on core cooling and shivering threshold during snow burial

Area of Science:

• Environmental Physiology
• Hypothermia Research

Background:

• Avalanche burial can lead to hypercapnia (elevated carbon dioxide levels).
• Hypercapnia may influence core body temperature regulation during cold exposure.

Purpose of the Study:

• To investigate the impact of hypercapnia on core temperature cooling rate.
• To assess respiratory heat loss and shivering threshold during simulated avalanche burial.

Main Methods:

• 11 subjects underwent simulated snow burial under both hypercapnic and normocapnic conditions.
• Rectal core temperature (T(re)), respiratory heat loss, and metabolic rate were measured.
• T(re) afterdrop was assessed during passive rewarming post-burial.

Main Results:

• Hypercapnia significantly increased the rate of T(re) cooling compared to normocapnia (1.28°C vs 0.97°C over 1 hour).
• Increased minute ventilation and respiratory heat loss were observed during hypercapnic burial.
• No significant difference in shivering threshold or post-extrication T(re) afterdrop was found between conditions.

Conclusions:

• Hypercapnia accelerates core body cooling in avalanche burial primarily through increased respiratory heat loss.
• Shivering suppression was not a mechanism for increased cooling under hypercapnia.
• Post-rescue T(re) afterdrop is a significant factor contributing to hypothermia in avalanche victims.