Maintenance of normothermia in the out-of-hospital setting: A pilot comparative crossover study of a foil blanket versus self-warming blanket

Introduction: Hypothermia can increase mortality in certain patients. Paramedics apply cotton and foil "space" blankets for warming, yet their effectiveness remains uncertain. This pilot study aimed to evaluate combining cotton blankets with a self-warming blanket versus a combination of cotton blankets and a foil blanket in an out-of-hospital simulation.

Methods: Eight participants were allocated to warming with either two cotton blankets and one foil blanket, or two cotton blankets and one self-warming blanket, with the alternate method applied in a subsequent session. Participants were cooled using an ice-vest and fan until shivering onset, after which the warming method was applied. Simulation involved transitioning through three environments: baseline (22 °C), cooling/warming (16 °C), and "ambulance" (27 °C). Core temperature was monitored via oesophageal probe, skin temperature via thermistors (recorded every minute), and tympanic temperature and thermal sensation and comfort were recorded five minutely.

Results: There were minor differences in thermal sensation. For the primary outcome there was no significant difference between blanket methods (core: foil 36.98 ± 0.08 °C vs. self-warming 36.95 ± 0.10 °C, P > 0.05).

Conclusion: The combination of cotton and self-warming blankets did not exhibit superiority compared to cotton and foil blankets in out-of-hospital simulation. Future research should explore alternative warming methodologies to optimise normothermia maintenance.