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Protection against cold in prehospital care: evaporative heat loss reduction by wet clothing removal or the addition of a vapour barrier - a thermal manikin study
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
Lunds universitet, Insitutionen för designvetenskaper.
Lunds universitet, Insitutionen för designvetenskaper.
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2012 (English)In: Prehospital and Disaster Medicine, ISSN 1049-023X, E-ISSN 1945-1938, Vol. 26, no 6, 1-6 p.Article in journal (Refereed) Published
Abstract [en]

Introduction: In the prehospital care of a cold and wet person, early application of adequate insulation is of utmost importance to reduce cold stress, limit body core cooling, and prevent deterioration of the patient’s condition. Most prehospital guidelines on protection against cold recommend the removal of wet clothing prior to insulation, and some also recommend the use of a waterproof vapor barrier to reduce evaporative heat loss. However, there is little scientific evidence of the effectiveness of these measures.

Objective: Using a thermal manikin with wet clothing, this study was conducted to determine the effect of wet clothing removal or the addition of a vapor barrier on thermal insulation and evaporative heat loss using different amounts of insulation in both warm and cold ambient conditions.

Methods: A thermal manikin dressed in wet clothing was set up in accordance with the European Standard for assessing requirements of sleeping bags, modified for wet heat loss determination, and the climatic chamber was set to -15 degrees Celsius (°C) for cold conditions and +10°C for warm conditions. Three different insulation ensembles, one, two or seven woollen blankets, were chosen to provide different levels of insulation. Five different test conditions were evaluated for all three levels of insulation ensembles: (1) dry underwear; (2) dry underwear with a vapor barrier; (3) wet underwear; (4) wet underwear with a vapor barrier; and (5) no underwear. Dry and wet heat loss and thermal resistance were determined from continuous monitoring of ambient air temperature, manikin surface temperature, heat flux and evaporative mass loss rate.

Results: Independent of insulation thickness or ambient temperature, the removal of wet clothing or the addition of a vapor barrier resulted in a reduction in total heat loss of 19-42%. The absolute heat loss reduction was greater, however, and thus clinically more important in cold environments when little insulation is available. A similar reduction in total heat loss was also achieved by increasing the insulation from one to two blankets or from two to seven blankets.

Conclusion: Wet clothing removal or the addition of a vapor barrier effectively reduced evaporative heat loss and might thus be of great importance in prehospital rescue scenarios in cold environments with limited insulation available, such as in mass-casualty situations or during protracted evacuations in harsh conditions.

Place, publisher, year, edition, pages
2012. Vol. 26, no 6, 1-6 p.
Keyword [en]
Hypothermia
National Category
Surgery
Research subject
Surgery
Identifiers
URN: urn:nbn:se:umu:diva-54369DOI: 10.1017/S1049023X12000210OAI: oai:DiVA.org:umu-54369DiVA: diva2:523460
Available from: 2012-04-25 Created: 2012-04-24 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Protection against cold in prehospital trauma care
Open this publication in new window or tab >>Protection against cold in prehospital trauma care
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Protection against cold is vitally important in prehospital trauma care to reduce heat loss and prevent body core cooling.

Objectives: Evaluate the effect on cold stress and thermoregulation in volunteer subjects byutilising additional insulation on a spineboard (I). Determine thermal insulation properties of blankets and rescue bags in different wind conditions (II). Establish the utility of wet clothing removal or the addition of a vapour barrier by determining the effect on heat loss within different levels of insulation in cold and warm ambient temperatures (III) and evaluating the effect on cold stress and thermoregulation in volunteer subjects (IV).

Methods: Aural canal temperature, sensation of shivering and cold discomfort was evaluated in volunteer subjects, immobilised on non-insulated (n=10) or insulated (n=9) spineboards in cold outdoor conditions (I). A thermal manikin was setup inside a climatic chamber and total resultant thermal insulation for the selected ensembles was determined in low, moderate and high wind conditions (II). Dry and wet heat loss and the effect of wet clothing removal or the addition of a vapour barrier was determined with the thermal manikin dressed in either dry, wet or no clothing; with or without a vapour barrier; and with three different levels of insulation in warm and cold ambient conditions (III). The effect on metabolic rate, oesophageal temperature, skin temperature, body heat storage, heart rate, and cold discomfort by wet clothing removal or the addition of a vapour barrier was evaluated in volunteer subjects (n=8), wearing wet clothing in a cold climatic chamber during four different insulation protocols in a cross-over design (IV).

Results: Additional insulation on a spine board rendered a significant reduction of estimated shivering but there was no significant difference in aural canal temperature or cold discomfort (I). In low wind conditions, thermal insulation correlated to thickness of the insulation ensemble. In greater air velocities, thermal insulation was better preserved for ensembles that were windproof and resistant to the compressive effect of the wind (II). Wet clothing removal or the use of a vapour barrier reduced total heat loss by about one fourth in the cold environment and about one third in the warm environment (III). In cold stressed wet subjects, with limited insulation applied, wet clothing removal or the addition of a vapour barrier significantly reduced metabolic rate, increased skin rewarming rate, and improved total body heat storage but there was no significant difference in heart rate or oesophageal temperature cooling rate (IV). Similar effects on heat loss and cold stress was also achieved by increasing the insulation. Cold discomfort was significantly reduced with the addition of a vapour barrier and with an increased insulation but not with wet clothing removal.

Conclusions: Additional insulation on a spine board might aid in reducing cold stress inprolonged transportations in a cold environment. In extended on scene durations, the use of a windproof and compression resistant outer cover is crucial to maintain adequate thermal insulation. In a sustained cold environment in which sufficient insulation is not available, wet clothing removal or the use of a vapour barrier might be considerably important reducing heat loss and relieving cold stress.

Place, publisher, year, edition, pages
Umeå universitet, 2012. 52 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1501
Keyword
Hypothermia, prehospital trauma care, emergency medical services, passive warming, thermal insulation, heat loss, body temperature regulation
National Category
Surgery
Research subject
Surgery
Identifiers
urn:nbn:se:umu:diva-54372 (URN)978-91-7459-422-5 (ISBN)
Public defence
2012-05-16, sal B, 9 tr, Tandläkarhögskolan, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2012-04-25 Created: 2012-04-24 Last updated: 2012-04-25Bibliographically approved

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