Comparison of three different prehospital wrapping methods for preventing hypothermia - a crossover study in humans

Abstract

BackgroundAccidental hypothermia increases mortality and morbidity in trauma patients. Various methods for insulating and wrapping hypothermic patients are used worldwide. The aim of this study was to compare the thermal insulating effects and comfort of bubble wrap, ambulance blankets / quilts, and Hibler's method, a low-cost method combining a plastic outer layer with an insulating layer.MethodsEight volunteers were dressed in moistened clothing, exposed to a cold and windy environment then wrapped using one of the three different insulation methods in random order on three different days. They were rested quietly on their back for 60 minutes in a cold climatic chamber. Skin temperature, rectal temperature, oxygen consumption were measured, and metabolic heat production was calculated. A questionnaire was used for a subjective evaluation of comfort, thermal sensation, and shivering.ResultsSkin temperature was significantly higher 15 minutes after wrapping using Hibler's method compared with wrapping with ambulance blankets / quilts or bubble wrap. There were no differences in core temperature between the three insulating methods. The subjects reported more shivering, they felt colder, were more uncomfortable, and had an increased heat production when using bubble wrap compared with the other two methods. Hibler's method was the volunteers preferred method for preventing hypothermia. Bubble wrap was the least effective insulating method, and seemed to require significantly higher heat production to compensate for increased heat loss.ConclusionsThis study demonstrated that a combination of vapour tight layer and an additional dry insulating layer (Hibler's method) is the most efficient wrapping method to prevent heat loss, as shown by increased skin temperatures, lower metabolic rate and better thermal comfort. This should then be the method of choice when wrapping a wet patient at risk of developing hypothermia in prehospital environments.

A torso model comparison of temperature preservation devices for use in the prehospital environment

“…As per Allen et al study,8 findings may not be extrapolated to human beings, as the model did not reproduce human metabolic basal activity and hypothermic physiological responses. The specific heat capacity of the human body is around 3470 J/kgK while that of water is around 4186 J/kgK, thus the torso models would cool more slowly than a human body, which may offset this issue to some degree.…”

“…Finally, Thomassen et al 8 compared three different passive systems (ambulance blanket, bubble wrap and Hibler's method—a combination of tight layer and dry insulating layer) on healthy volunteers. The study population was dressed in wet clothes, and placed in a cold climatic chamber at 3°C and 3 m/s wind.…”

Evaluating Cold, Wind, and Moisture Protection of Different Coverings for Prehospital Maritime Transportation–A Thermal Manikin and Human Study

“…There were significant differences between the systems in skin temperature, metabolic heat production, and thermal sensations, but not in rectal temperature. 10 This study showed that rescue bag 3 on top of LWC provided sufficient protection in the studied conditions (air temperature approximately 1 8C). Core temperature remained on average between 37.1 8C and 37.4 8C in both tested ensembles, which is within Lotens' ''comfort'' limits.…”

The prehospital management of avalanche victims

“…Instead, evaporative heat loss may be minimised by adding an airtight vapour barrier immediately outside the wet clothing 52. Recent studies have suggested that the optimal packaging method for wet conditions is a combination of a vapour-tight inner layer followed by a dry insulating middle layer covered in a wind-resistant and water-resistant outer wrapping 53 54. Obtaining vascular access may be difficult due to hypothermic and/or hypovolaemic vasoconstriction.…”