Conference Paper

NREL/CP-540-45888

July 2009

Assessment of Hypothermia 

Blankets Using an Advanced 

Thermal Manikin 

Preprint

J.P. Rugh

National Renewable Energy Laboratory

K. Barazanji

U.S. Army Aeromedical Research Laboratory

To be presented at the International Conference on Environmental 

Ergonomics 2009 (ICEE 2009)

Boston, Massachusetts

August 2–7, 2009
NOTICE

The submitted manuscript has been offered by an employee of the Alliance for Sustainable Energy, LLC 

(ASE), a contractor of the US Government under Contract No. DE-AC36-08-GO28308. Accordingly, the US 

Government and ASE retain a nonexclusive royalty-free license to publish or reproduce the published form of 

this contribution, or allow others to do so, for US Government purposes.

This report was prepared as an account of work sponsored by an agency of the United States government. 

Neither the United States government nor any agency thereof, nor any of their employees, makes any 

warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or 

usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not 

infringe privately owned rights. Reference herein to any specific commercial product, process, or service by 

trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, 

recommendation, or favoring by the United States government or any agency thereof. The views and 

opinions of authors expressed herein do not necessarily state or reflect those of the United States 

government or any agency thereof.

Available electronically at http://www.osti.gov/bridge

Available for a processing fee to U.S. Department of Energy

and its contractors, in paper, from:

U.S. Department of Energy

Office of Scientific and Technical Information 

P.O. Box 62

Oak Ridge, TN 37831-0062

phone: 865.576.8401

fax: 865.576.5728

email: mailto:reports@adonis.osti.gov

Available for sale to the public, in paper, from:

U.S. Department of Commerce

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

phone: 800.553.6847

fax: 703.605.6900

email: orders@ntis.fedworld.gov

online ordering: http://www.ntis.gov/ordering.htm

Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste
1 

Assessment of Hypothermia Blankets Using an Advanced Thermal Manikin 

John P. Rugh1* and Khalid Barazanji2

1

U.S. Department of Energy National Renewable Energy Laboratory, Golden, Colorado, USA 

2

U.S. Army Aeromedical Research Laboratory, Fort Rucker, Alabama, USA 

Contact person: john.rugh@nrel.gov 

INTRODUCTION

The U.S. Army Aeromedical Research Laboratory (USAARL) and the U.S. Department of 

Energy’s National Renewable Energy Laboratory (NREL) used NREL’s thermal manikin,

controlled by a human thermal physiological model, to assess various hypothermia blankets. 

These blankets are important during medical transport because environmental conditions, 

coupled with a patient’s traumatic injury, can often lead to physiological thermal imbalance. 

High wind and low air temperatures during a medical evacuation can lead to excessive heat loss 

from the patient, resulting in hypothermia. This condition can complicate the treatment of the 

patient upon arrival at the hospital. 

NREL’s thermal comfort tools consist of the thermal comfort manikin (ADAM, for ADvanced 

Automotive Manikin), a physiological model, and a psychological model linked together to 

assess comfort in a transient, nonhomogeneous environment (1, 2). In the integrated human 

thermal comfort system, ADAM is controlled by a finite-element physiological model of the 

human body. 

The thermal manikin is a surface sensor that measures the rate of heat loss at 120 independently 

controlled zones. The skin heat transfer rates are sent to the physiological model, which 

computes the skin and internal temperature distribution and surface sweat rates. This 

information is then sent back to the manikin, which generates the prescribed skin temperatures, 

surface sweat rates, and breathing rates. As the model steps forward in time, this loop provides a 

transient measurement tool. The psychological comfort model uses temperature data from the 

physiological model to predict local and global thermal comfort as a function of local skin and 

core temperatures and their rates of change. 

METHODS

Testing was conducted in NREL’s Manikin Environmental Chamber in Golden, Colorado. The 

test conditions were 15oC air temperature and 50% to 60% relative humidity. Three portable 

fans provided 7 mph airflow over the manikin. 

Four hypothermia blanket configurations were tested in conjunction with a stretcher: (1) wool 

army blanket (heat retention), (2) electric heating blanket, (3) radiant heating blanket, and (4) 

chemical heating blanket. The Army blanket was a standard-issue brown rectangular blanket. 

The electric heating blanket consisted of a lightweight inner wrap and an outer shell blanket 

containing heating elements. The radiant heating blanket used resistive carbon fiber technology 

* An employee of the Alliance for Sustainable Energy, LLC under Contract No. DE-AC36-08GO28308 with the U.S. Department of 

Energy has authored this work. The United States Government retains and the publisher, by accepting the article for publication, 

acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce 

the published form of this work, or allow others to do so, for United States Government purposes.
2 

with a microprocessor-controlled temperature regulation system. The radiant blanket contained 

five woven carbon fiber warming panels, each measuring 9 by 14 inches, designed to distribute 

heat evenly from the shoulders to below the feet. The chemical heating blanket system consisted 

of a sheet next to the patient, a thin blanket containing the chemical, and an outer radiation 

shield. The sheet was a regular bed sheet placed between the manikin and the chemical blanket 

to protect the skin from excessive temperature. The chemical blanket layer had six pouches 

measuring 7 by 10 inches containing the chemical material that generated heat when exposed to 

air. The outer shield was 88 by 93 inches and had a reflective inner surface to reflect body heat 

back to the patient. Thermocouples were secured to the chemical blanket layer to assess 

potential hot spots. 

The manikin was placed on an actual medical evacuation stretcher made of a mesh material and a 

frame that allowed air flow under the patient. The manikin was unclothed under the thermal 

blankets, and the manikin’s uncovered head extended beyond the edge of the blanket. Figure 1 

shows ADAM testing the wool Army blanket. Figure 2 shows the electric and radiant heating 

blankets, and Figure 3 shows the chemical blanket. 

Figure 1. Test of a Wool Army Blanket Using the Thermal Manikin 

Figure 2. Electric and Radiant Heating Blankets 
3 

Figure 3. IR Image of the Chemical Blanket and Photo of the Outer Radiation Shield 

During the first part of the test, the steady-state heat loss from the manikin was measured at 

constant skin temperatures of 34oC and 40oC for each blanket configuration. We found that a 

skin temperature of 34oC was not hot enough for active blanket configurations. When the zone 

skin temperature exceeded 34oC, the heater turned off and there was no longer active control for 

that zone. Therefore, we had to increase to a skin control temperature of 40oC for the steadystate tests to increase the number of segments with active control.

Immediately after the steady-state constant skin temperature test, the manikin was controlled 

with the physiological model, and the metabolic rate was set at 95 W. The test was run until a 

steady-state core temperature was attained. Key outputs of skin and core temperature were 

compared for each blanket configuration. The core temperature was defined as a volume 

average temperature of the brain. This was useful for a run-to-run comparison, but it should not 

be used to define the onset of hypothermia. A different definition of core temperature would 

produce a different result. The average skin temperature was defined as an average of 16 skin 

temperatures distributed around the body. 

RESULTS

The constant skin temperature steady-state results are shown in Figure 4. When wrapped in a 

wool blanket, the manikin measured a 205.5 W/m2 heat loss. The test of the electric blanket

resulted in a higher heat loss, and that of the radiant blanket produced a lower heat loss. The 

heat loss result for the chemical blanket was significantly lower, at 79.5 W/m2

. This finding was 

mainly due to the outer radiation shield of the chemical heating blanket system. Tests performed 

without having the radiation shield well wrapped and without the radiation shield altogether 

yielded higher heat losses. 
4 

 

205.5

263.3

182.0

79.5

0

50

100

150

200

250

300

Wool Blanket Electric Blanket Radiant Blanket Chemical/radiation shield

with double sheet

Heat Loss from ADAM (W/m2

) Figure 4. Steady-State Heat Loss with 40°C Skin Temperature 

Controlling the manikin with the physiological model yielded results that were similar to those of 

the constant skin temperature tests. Figure 5 shows that the wool blanket produced a manikin 

core temperature of 33.9°C. The test of the electric blanket resulted in the lowest core 

temperature, and that of the chemical blanket produced the highest core temperature of 35.4°C.

The skin temperatures were consistent with the core temperature results, except for the electric 

blanket. In that case, the average skin temperature was warmer than the wool blanket, while the 

core temperature was cooler. The chest and leg temperatures were warmer, but there was greater 

heat loss and lower skin temperatures on the manikin’s sides and back. The average skin 

temperature calculation was constrained to 16 points and missed these cool spots. The manikin 

with physiological model control responded to the environment with higher fidelity and

measured a lower core temperature. The chemical blanket test resulted in the warmest skin 

temperatures, although this blanket produced hot spots up to 70oC on the surface of the blanket. 

33.9

33.4

34.1

35.4

32.0

32.6

34.4

35.9

29

30

31

32

33

34

35

36

Wool Blanket Electric Blanket Radiant Blanket Chemical/radiation shield 

with double sheet

Temperature (oC)

 

Core Temperature

Skin Temperature (16 point average)

Figure 5. Average Skin and Core Temperatures during Physiological Model Control 
5 

For the wool, electric, and radiant blanket tests, placing a wool blanket between the manikin and 

stretcher significantly reduced heat loss (Figure 6). For the wool blanket case, placing a wool 

blanket under the manikin resulted in a 30% reduction in heat loss, to 144.4 W/m2. This was a 

better result than those for the regular electric and radiant blankets. The chemical blanket was 

not impacted by placing the wool blanket underneath it because it was already well wrapped and 

insulated because of the radiation shield. Placing a radiation shield around a wool blanket with 

wool underneath resulted in an additional 30% drop in heat loss, from 144.4 to 101.8 W/m2 . 

205.5

263.3

182.0

79.5

144.4

125.5

106.4

86.3

0

50

100

150

200

250

300

Wool Blanket Electric Blanket Radiant Blanket Chemical/radiation

shield with double sheet

Heat Loss from ADAM (W/m2

)

Manikin directly on stretcher

Manikin on wool blanket on stretcher

Figure 6. Impact on Heat Loss of Placing a Wool Blanket under the Manikin 

CONCLUSIONS

The thermal manikin was successfully used to assess thermal blankets. The chemical blanket 

showed the best thermal performance, specifically, the lowest heat loss and the highest skin and 

core temperatures. Care providers should not place a chemical heating blanket directly on the 

patient’s skin, however. The electric blanket showed the highest heat loss and coolest core 

temperature. Placing a wool blanket between the manikin and the stretcher significantly reduced 

heat loss when the wool, electric, and radiant blankets were used. Wrapping a radiation shield 

around a conventional wool blanket and using a wool blanket underneath the patient further 

reduced heat loss. 

REFERENCES

1. Rugh, J.; Bharathan, D. "Predicting Human Thermal Comfort in Automobiles." Seventh Vehicle Thermal 

Management Systems Conference Proceedings; May 10-12, 2005, Toronto, Canada. SAE Paper No. 2005-

01-2008.

2. Rugh, J.; Lustbader, J. "Application of a Sweating Manikin Controlled by a Human Physiological Model 

and Lessons Learned." Sixth International Meeting on Thermal Manikins and Modeling (613M) 

Proceedings; October 17-18, 2006.
F1147-E(10/2008) 

REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, 

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this 

collection of information, including suggestions for reducing the burden, to Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents 

should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a 

currently valid OMB control number.

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION.

1. REPORT DATE (DD-MM-YYYY)

July 2009

2. REPORT TYPE

Conference Paper

3. DATES COVERED (From - To)

 

4. TITLE AND SUBTITLE

Assessment of Hypothermia Blankets Using an Advanced Thermal 

Manikin: Preprint

5a. CONTRACT NUMBER

DE-AC36-08-GO28308

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

J.P. Rugh and K. Barazanji

5d. PROJECT NUMBER

NREL/CP-540-45888

5e. TASK NUMBER

2900.8041

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Renewable Energy Laboratory

1617 Cole Blvd.

Golden, CO 80401-3393

8. PERFORMING ORGANIZATION

REPORT NUMBER

NREL/CP-540-45888

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)

NREL

11. SPONSORING/MONITORING

AGENCY REPORT NUMBER

12. DISTRIBUTION AVAILABILITY STATEMENT

National Technical Information Service

U.S. Department of Commerce

5285 Port Royal Road

Springfield, VA 22161

13. SUPPLEMENTARY NOTES

14. ABSTRACT (Maximum 200 Words)

A thermal manikin developed at NREL was used to assess several thermal blankets intended to help treat U.S. Army 

personnel suffering from hypothermia. The chemical blanket showed the best thermal performance, specifically, the 

lowest heat loss and the highest skin and core temperatures. Care providers should not place a chemical heating 

blanket directly on a patient’s skin, however. The electric blanket showed the highest heat loss and coolest core 

temperature. Placing a wool blanket between the manikin and the stretcher significantly reduced heat loss when the 

wool, electric, and radiant blankets were used. Wrapping a radiation shield around a conventional wool blanket and 

using a wool blanket underneath the patient further reduced heat loss. 

15. SUBJECT TERMS

thermal manikin; hypothermia; hypothermia blankets; assessment

16. SECURITY CLASSIFICATION OF: 17. LIMITATION 

OF ABSTRACT

UL

18. NUMBER 

OF PAGES

19a. NAME OF RESPONSIBLE PERSON

a. REPORT

Unclassified

b. ABSTRACT

Unclassified

c. THIS PAGE

Unclassified 19b. TELEPHONE NUMBER (Include area code)

Standard Form 298 (Rev. 8/98)

Prescribed by ANSI Std. Z39.18