Minor Decrease of Core Temperature in Shivering Volunteers Over a 3-Hour Exposure to Cold, Wet, and Windy Conditions

ObjectiveHypothermia increases mortality among trauma patients. It is difficult to identify hypothermia in conscious patients due to the limited availability of diagnostic equipment yielding accurate measurements. Shivering is a symptom associated with hypothermia, and it serves as a parameter for clinical staging of hypothermia. Because shivering is part of the body's response to counteract hypothermia, the resulting thermogenic effect and expected cooling rates in shivering individuals warrant further investigation. This study aimed to describe core temperature trajectories in a setting of cold air, mild wind, and wet clothing, simulating a clinically relevant prehospital scenario.MethodsFifteen healthy volunteers were dressed in wet clothing and placed in a windy climate chamber set at 5.0°C for 3 h. Core temperature was measured using an esophageal probe (<i>T_eso</i>) and an ingestible capsule (<i>T_cap</i>). Shivering was estimated based on oxygen consumption (VO₂) and by objective observations of the participants.ResultsThe temperature reductions from baseline were 0.25°C for <i>T_eso</i> (95% CI, 0.06-0.44°C, <i>P</i>=0.014) and 0.11°C for <i>T_cap</i> (95% CI, -0.13-0.34°C, <i>P</i>=0.36). Initially, participants exhibited a significant increase in temperature. The cooling rate in the climate chamber was 0.17°C·h^-1 (<i>T_eso</i>). VO₂ corresponded with objective observations of shivering and was inversely related to <i>T_eso</i>.ConclusionsHealthy individuals exposed to the described windy, wet, and cold conditions with only light clothing retained a normal core temperature for 3 h. The heat-producing mechanism of shivering is considered to be a significant contributing factor; therefore, a lack of shivering in patients in cold environments should be considered a warning sign for hypothermia.