Article Text

Download PDFPDF
Differences in the thermal properties and surface temperature of prehospital antihypothermia devices: an in vitro study
  1. Erez Dvir1,2,
  2. Danny Epstein3,4,
  3. Baruch Berzon5,
  4. Aeyal Raz1,2,
  5. Amit Lehavi1,2
  1. 1 Department of Anaesthesiology, Rambam Health Care Campus, Haifa, Israel
  2. 2 The Ruth and Bruce Rappaport Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
  3. 3 Critical Care Division, Rambam Health Care Campus, Haifa, Israel
  4. 4 Medical Corps, IDF, Tel-Hashomer, Israel
  5. 5 Department of Emergency Medicine, Assuta Ashdod Hospital, Ashdod, Israel
  1. Correspondence to Dr Danny Epstein, Critical Care Division, Rambam Health Care Campus, Haifa 3109601, Israel; danyep{at}


Background Preventing and treating hypothermia in prehospital settings is crucial. Several products have been developed to prevent heat loss and actively warm patients in prehospital settings. We compared the efficacy and the surface temperature of different antihypothermia products, using a fluid-based model at two ambient temperatures.

Methods We tested five active (Blizzard Heat with active pads, Ready-Heat, Ready-Heat-II, Hypothermia Prevention and Management Kit (HPMK), Bair Hugger) and five passive (Blizzard Heat, Heat Reflective Shell, sleeping bag, ‘space blanket’, wool blanket) antihypothermia products. A torso model consisting of four 8 L bags of fluid preheated to 36°C±0.5°C (97±0.5°F) was used to compare the devices’ performances at 20°C (68°F) and 8°C (46°F). Inner and surface temperatures were recorded for up to 480 min.

Results We found significant differences in heat loss in fluid bags among the tested devices at both temperatures (p<0.001). At 20°C, only HPMK and Ready-Heat-II increased the inner temperature for 480 min while Blizzard Heat with active pads prevented heat loss. Ready-Heat prevented heat loss for 90 min. All the other devices did not prevent heat loss beyond 30 min. At 8°C, none of the products heated the model. Bair Hugger, HPMK, Ready-Heat II and sleeping bag prevented heat loss for 30 min. At 60, 90 and 120 min HPMK, Ready-Heat II and Bair Hugger were the most effective. Over 480 min, Bair Hugger was most effective, with a heat loss of 2.3°C±0.4°C. The surface temperature exceeded 44°C (111°F) for all the exothermic warming devices when used for a prolonged period of time.

Conclusion At 20°C, HPMK and Ready-Heat-II increased fluid temperature in the model, while the other devices decreased heat loss. At 8°C, none of the tested devices increased the temperature. However, active heating devices prevented heat loss slightly better than passive methods. A protective insulation layer should be used with all active heating blankets.

  • hypothermia
  • prehospital care

Data availability statement

Data are available on reasonable request.

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

Data availability statement

Data are available on reasonable request.

View Full Text


  • ED and DE are joint first authors.

  • Handling editor Ed Benjamin Graham Barnard

  • Contributors ED, AR, DE, BB and AL were involved in the study system design and production, and acquisition of data. All the authors contribute to the study conception, design, analysis and interpretation of data, drafting and critical revision of the manuscript. All the authors approved the final manuscript as submitted. ED and DE contributed equally as first authors. ED is acting as guarantor.

  • Funding The study was funded by the Department of Anaesthesiology and some of the equipment was supplied by the Israeli Defense Forces, Medical corps, with no external grant support.

  • Competing interests AR reports receiving consultant fees from Medtronic and Neuroindex (not related to this work). All the other authors declare no competing interests. This project received non-financial support from Blizzard Protection Systems Limited, Gwynedd, UK, Mölnlycke Health Care, Gothenburg, Sweden, North American Rescue LLC, OR, USA and Techtrade LLC, NJ, USA (providing products for testing), and from the Israeli Defense Forces, Medical Corps (providing temperature sensors).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.