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Protection against cold in prehospital trauma care
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
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 [en]
Hypothermia, prehospital trauma care, emergency medical services, passive warming, thermal insulation, heat loss, body temperature regulation
National Category
Surgery
Research subject
Surgery
Identifiers
URN: urn:nbn:se:umu:diva-54372ISBN: 978-91-7459-422-5 (print)OAI: oai:DiVA.org:umu-54372DiVA: diva2:523467
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
List of papers
1. Insulated spine boards for prehospital trauma care in a cold environment
Open this publication in new window or tab >>Insulated spine boards for prehospital trauma care in a cold environment
2004 (English)In: International Journal of Disaster Medicine, ISSN 1503-1438, E-ISSN 1755-4713, Vol. 2, no 1-2, 33-37 p.Article in journal (Refereed) Published
Abstract [en]

Objectives: The aim of this study was to examine, during field conditions, what impact additional insulation on a spine board would have on thermoregulation.

Method: The study was conducted outdoors, under field conditions in February in the north of Sweden. The subjects, all wearing standardised clothing, were immobilised on uninsulated (n=10) or insulated spine boards (n=9). Tympanic temperature as well as the subjects’ estimated sensation of cold and their estimated level of shivering were measured at five minute intervals during the trial. Statistical analysis of the data gathered for the first 55 minutes was performed.

Results: There were no differences between the two groups regarding reduction in body core temperature or cold discomfort. There was, however, a statistically significant increase in estimated shivering for the subjects placed on uninsulated spine boards.

Conclusion: Additional insulation on a spine board by the means of an insulation mat rendered a significantly reduced need for shivering in a cold environment. This is an effect that could be of great importance during protracted evacuations of injured, ill or otherwise compromised patients. In the light of these results we conclude that spine boards, as well as other materials used for prehospital transportation of patients in cold environments, should be well insulated. This is a measure that could be accomplished by such simple means as using an additional insulation mat.

Keyword
hypothermia
National Category
Surgery
Research subject
Surgery
Identifiers
urn:nbn:se:umu:diva-54367 (URN)10.1080/15031430410023913 (DOI)
Available from: 2012-04-25 Created: 2012-04-24 Last updated: 2017-12-07Bibliographically approved
2. Protection against cold in prehospital care: thermal insulation properties of blankets and rescue bags in different wind conditions
Open this publication in new window or tab >>Protection against cold in prehospital care: thermal insulation properties of blankets and rescue bags in different wind conditions
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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.

Keyword
Hypothermia, body temperature regulation; cold; emergency medical services; thermal insulation; thermal manikin; wind
National Category
Surgery
Research subject
Surgery
Identifiers
urn:nbn:se:umu:diva-34148 (URN)20066643 (PubMedID)
Available from: 2012-04-25 Created: 2010-05-14 Last updated: 2012-05-09Bibliographically approved
3. 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
Open this publication in new window or tab >>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
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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.

Keyword
Hypothermia
National Category
Surgery
Research subject
Surgery
Identifiers
urn:nbn:se:umu:diva-54369 (URN)10.1017/S1049023X12000210 (DOI)
Available from: 2012-04-25 Created: 2012-04-24 Last updated: 2017-12-07Bibliographically approved
4. Protection against cold - the effect on thermoregulation by wet clothing removal or addition of a vapour barrier in shivering subjects
Open this publication in new window or tab >>Protection against cold - the effect on thermoregulation by wet clothing removal or addition of a vapour barrier in shivering subjects
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(English)Manuscript (preprint) (Other academic)
Keyword
Hypothermia
National Category
Surgery
Research subject
Surgery
Identifiers
urn:nbn:se:umu:diva-54370 (URN)
Available from: 2012-04-24 Created: 2012-04-24 Last updated: 2012-04-25

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