Hypercapnia increases core temperature cooling rate during snow burial

Area of Science:

• Environmental Physiology
• Hypothermia Research
• Avalanche Medicine

Background:

• Previous studies suggest a core body temperature cooling rate of 3°C/h during avalanche burial.
• The impact of hypercapnia (elevated carbon dioxide) on hypothermia during avalanche burial is not well understood.
• Hypercapnia can occur due to rebreathing expired air in an avalanche burial scenario.

Purpose of the Study:

• To determine the core body temperature cooling rate during snow burial under both normocapnic and hypercapnic conditions.
• To investigate the physiological effects of hypercapnia during simulated avalanche burial.

Main Methods:

• Twelve subjects were buried in compacted snow under controlled conditions.
• Rectal core body temperature (T(re)) was measured during two burial scenarios: one inducing hypercapnia and a control with normocapnia.
• A specialized breathing device (AvaLung 2) was used to induce hypercapnia, while a modified device maintained normocapnia.

Main Results:

• The core body temperature cooling rate was significantly greater under hypercapnic conditions (1.2°C/h) compared to normocapnic conditions (0.7°C/h).
• During hypercapnia, inspired carbon dioxide increased, minute ventilation rose, and oxygen saturation decreased.
• The observed cooling rate in this study was lower than previously reported retrospective findings.

Conclusions:

• Hypercapnia accelerates the rate of core body temperature decrease during snow burial.
• These findings suggest that managing carbon dioxide levels may be crucial in prehospital treatment for avalanche victims.
• Further research is warranted to explore the clinical implications of hypercapnia in avalanche survival and treatment strategies.