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Protection against cold in prehospital care: thermal insulation properties of blankets and rescue bags in different wind conditions
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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2009 (English)In: Prehospital and disaster medicine : the official journal of the National Association of EMS Physicians and the World Association for Emergency and Disaster Medicine in association with the Acute Care Foundation, ISSN 1049-023X, Vol. 24, no 5, 408-415 p.Article in journal (Refereed) Published
Abstract [en]

INTRODUCTION: In a cold, wet, or windy environment, cold exposure can be considerable for an injured or ill person. The subsequent autonomous stress response initially will increase circulatory and respiratory demands, and as body core temperature declines, the patient's condition might deteriorate. Therefore, the application of adequate insulation to reduce cold exposure and prevent body core cooling is an important part of prehospital primary care, but recommendations for what should be used in the field mostly depend on tradition and experience, not on scientific evidence.

OBJECTIVE: The objective of this study was to evaluate the thermal insulation properties in different wind conditions of 12 different blankets and rescue bags commonly used by prehospital rescue and ambulance services.

METHODS: The thermal manikin and the selected insulation ensembles were setup inside a climatic chamber in accordance to the modified European Standard for assessing requirements of sleeping bags. Fans were adjusted to provide low (< 0.5 m/s), moderate (2-3 m/s) and high (8-9 m/s) wind conditions. During steady state thermal transfer, the total resultant insulation value, Itr (m2 C/Wclo; where C = degrees Celcius, and W = watts), was calculated from ambient air temperature (C), manikin surface temperature (C), and heat flux (W/m2).

RESULTS: In the low wind condition, thermal insulation of the evaluated ensembles correlated to thickness of the ensembles, ranging from 2.0 to 6.0 clo (1 clo = 0.155 m2 C/W), except for the reflective metallic foil blankets that had higher values than expected. In moderate and high wind conditions, thermal insulation was best preserved for ensembles that were windproof and resistant to the compressive effect of the wind, with insulation reductions down to about 60-80% of the original insulation capacity, whereas wind permeable and/or lighter materials were reduced down to about 30-50% of original insulation capacity.

CONCLUSIONS: The evaluated insulation ensembles might all be used for prehospital protection against cold, either as single blankets or in multiple layer combinations, depending on ambient temperatures. However, with extended outdoor, on-scene durations, such as during prolonged extrications or in multiple casualty situations, the results of this study emphasize the importance of using a windproof and compression resistant outer ensemble to maintain adequate insulation capacity.

Place, publisher, year, edition, pages
2009. Vol. 24, no 5, 408-415 p.
Keyword [en]
Hypothermia, body temperature regulation; cold; emergency medical services; thermal insulation; thermal manikin; wind
National Category
Surgery
Research subject
Surgery
Identifiers
URN: urn:nbn:se:umu:diva-34148PubMedID: 20066643OAI: oai:DiVA.org:umu-34148DiVA: diva2:319171
Available from: 2012-04-25 Created: 2010-05-14 Last updated: 2012-05-09Bibliographically 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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