Differences in the thermal properties and surface temperature of prehospital antihypothermia devices: an in vitro study.

At 20°C, HPMK and Ready-Heat-II increased fluid temperature in the model, while the other devices decreased heat loss. At 8°C, none of the tested devices increased the temperature. However, active heating devices prevented heat loss slightly better than passive methods. A protective insulation layer should be used with all active heating blankets.