Cold towels and other rehab tools
I am writing this letter in response to “Cold Towels Valuable Rehab Tools” by Guy W. Bull (Fire Engineering, April 2008), as I feel that some of the information was not based on adequate science and that it contained several points of information that were the author’s opinions with little to back them up.
I am the chief safety officer of a large metropolitan fire department and a member of the National Fire Protection Association (NFPA) 1500, Standard on Fire Department Occupational Safety and Health Program, committee. I also served on the NFPA 1584, Standard on the Rehabilitation Process for Members During Emergency Operations and Training Exercises, Task Group.
I applaud the author’s focus on core temperature increases and the possible link to heat stress-related line-of-duty deaths. Both the British Navy and Defence Research and Development Canada have demonstrated how active cooling can lower core body temperature in the field.
It makes sense that, depending on the surface area of the skin covered, the temperature of the water, the amount of water retained in the towels, and the length of time they are applied, this method should be an effective means of core cooling for firefighter rehabilitation.
I disagree that the use of the cold towel will work if hundreds of people require rehabilitation. You would require thousands of towels, a large supply of cold water, and people to assist others with these resources. Cooling chairs and misting fans could achieve the same results with similar resource requirements and still be effective. Although the misting fans, as the article suggests, lose effectiveness with increased humidity, hand and forearm immersion does not.
Tympanic temperatures (used in this study) are not a scientifically acceptable means of determining core temperature. They are known not to demonstrate consistent correlations to core temperatureparticularly in working environments generating metabolic heat. They are also too easily affected by many other variables. This one fact alone seriously dilutes the validity of claims made by the author.
Drinking cold water or sports drinks is a method of rehydration with the potential side benefit of promoting core cooling. It is clearly not intended to be used as a primary method of cooling. Hydration is essential to help minimize heat and heart stress associated with a lack of stroke volume (sweat comes from our plasma, essentially changing the viscosity of our blood) associated with emergency work.
When discussing conductive cooling devices, the author suggests that these devices, collectively, are “too cold and uncomfortable for routine cooling.” He goes on to diminish the value of other core-cooling devices regarding their “claims” for a scientific angle and lumps their collective disadvantages together with misting fans, suggesting they are impractical due to cost and on-scene support.
I challenge the author to provide scientific evidence regarding his claim that “ice water and cold towels are the most effective methods of cooling exertional heat illness.” I do not believe this is an accurate and proven scientific finding.
David Ross
Chief Health and Safety Officer
Toronto (Ont.) Fire Services
Canada
Guy W. Bull responds: The purpose of my article was to alert the firefighting community to the risks we face from heat stress, document significant increases in core temperatures that occur during routine training, and describe one method for restoring normal core temperatures during a 15-minute rehab cycle.
That 15-minute rehab cycle was well described: shade, doff jackets and pants, provide cold water and cold towels, and allow personnel to self-regulate how much they drink and how they use the towels. We certainly observed some unusual behaviors as firefighters used the towels to cool off; but in the end, most towels wound up either on heads or necks, no doubt because of individual preference.
Simple, inexpensive, and effective rehab tools and processes are needed in the fire service. This rehab method is simple and inexpensive, but is it effective? With regard to the rehab of hundreds of firefighters, my calculations provided in the article call for 20 towels, not hundreds. Twenty towels would rehab 600 firefighters in a 10-hour day. Twenty cooling chairs and misting fans would seem intuitively to require not only more space and transportation resources but also considerably more expense.
The accuracy of the tympanic membrane method for temperature measurement is a reasonable challenge. In my research, I measured a control group of six firefighters at rest in an air-conditioned station, recording an average temperature of 97.4°F. Using the same devices and technique, firefighters with temperatures of 101°F to 103.3°F were remeasured after 15 minutes of rehab and found to average 98.5°F, with none higher then 99°F. I’ll let the readers judge those numbers for themselves.
Critics of tympanic measurement usually question two components: accuracy and ability to reflect core temperature. Tympanic temperature measurement can be affected by many variables, including operator error. We were careful to use correct technique and not leave the device in direct sunlight to overheat (two common sources of error). The devices used were the same instruments our department uses to deliver 911 care to our citizens. I stand by our data.
Does tympanic temperature measure core temp? Nancy Espinoza, in her Orange County (CA) Fire Authority study on core body temperature and rehab, compared tympanic temperatures to the core body temperatures of 101 firefighters ingesting core body temperature capsules. Her data found expected differences between the two values that varied consistently as temperatures increased. While tympanic temperatures may not reflect true core temperature, for the purposes of firefighter rehab they are effective, cheap, and widely available. When used properly, they likely represent the most practical and least invasive means of assessing the effects of cooling during rehab.
I agree that rehydration promotes core cooling and acknowledge that it clearly contributed to the effects seen in our study. We did not attempt to isolate the effects of cold towels in our study but rather document the contribution of cold towels to our normal procedures of relief from climatic conditionsremoving turnout gear, rest, and hydration.
Science and psychology are inextricably intertwined; rehab is no exception. In our study, cold towels were perceived as superior to other means of cooling by the firefighter participants. Espinoza’s Orange County Fire Authority study, using more rigorous scientific criteria, reached the same findings. The participants deemed cold towels as the most refreshing and effective cooling measure compared to forearm immersion, misting, and ambient air. Researchers also scientifically found that the use of cold towels resulted in the least increase in core body temperature and were more practical, used less space, and cost less than cooling chairs.
The bottom line to my article was to offer a simple, inexpensive, and effective rehab tool for the fire service. Is it the most effective means of cooling? I believe our data and those of other researchers, such as Espinoza, demonstrate it is. Perhaps other methods, such as cooling chairs and misting fans, are as useful. They are not, however, as efficient, cost effective, or portable; neither are they perceived to be as effective and as refreshing as cold towels.
References
Gonzalez-Alonso J, R. Mora-Rodriguez R, PR Below, et al., “Dehydration markedly impairs cardiovascular function in hyperthermic endurance athletes during exercise,” Journal of Applied Physiology. 1997; 82(4):1229-1236.
Espinoza N., “Can we stand the heat?” Journal of Emergency Medical Services. 2008; 33(5):94-105.
