Steven Allen Bernards and Dr. Kenneth Knight, Physical Education

Cryotherapy (cold therapy) is the use of ice or cold in the immediate care of acute musculoskeletal injuries such as sprains or contusions. When ice or another temperature lowering product is applied soon after an injury, pain, swelling, and secondary hypoxic injury are minimized. Secondary hypoxic injury occurs when swelling and damage to the local vascular system causes healthy cells near the damaged tissue to suffer a lack of oxygen and die (3,4). The key to reducing secondary hypoxic injury is to decrease metabolism (6), which is a function of decreased temperature (1).

Emergency medicine protocols and teaching materials suggest the use of cold, but usually do not teach proper application methods (2, 7, 8). A common practice in emergency medicine and general first aid is to use a barrier (such as a gauze pad, washcloth, or towel) between the skin and cold pack. A barrier reduces the ability of a cold pack to lower temperature (5), thus limiting metabolism-decrease, so the beneficial effects of cold are reduced. There are many different temperature reducing agents (ice, frozen gel packs, chemical packs, etc.), but not all reduce temperature equally (5). Many pre-hospital care providers believe that chemical packs provide adequate cooling, while athletic trainers question this claim (3). There is little available data involving chemical cold packs, which is why this study was needed. This study has the potential of changing emergency medicine protocols, thus allowing for better patient care.

The purpose of this study was to measure the effectiveness of two types of cryotherapy with and without a barrier to reduce surface and intramuscular temperatures in the human thigh. The two types of cryotherapy used were crushed ice packs and chemical cold packs and the barrier used was a washcloth. A skin-fold caliper was used to measure skin-fold (the skin and fat layer). To measure intramuscular temperature, thermocouples were inserted into the muscle using a 20 gauge IV needle. The needle was placed in the thigh, the needle was removed leaving the catheter, the thermocouple was threaded through the catheter and finally the catheter removed. This allowed for placement of one thermocouple at a depth of 1cm and the other at 2cm below the skin-fold in each leg. Four thermocouples were then taped to the skin of the thigh to measure surface temperature. The cold packs were then applied with and without the barrier in a random manner.

My hypothesis was that the chemical cold packs were not as effective as ice in reducing surface and deep temperatures. I also hypothesized that the barrier would dramatically decrease the effectiveness of both types of cold packs. The results were as expected: ice cooled more than chemical packs at all levels and the washcloth decreased the effectiveness of the cold packs.

There is a great range in temperature decreases among different chemical cold pack brands. Before collecting data I did some initial testing with four different brands of chemical cold packs. These experiments were conducted by placing thermocouples between the cold packs and Styrofoam. I chose to use the brand that maintained the lowest temperature for the longest period of time for the research project.

The results of this project included not only data about the effectiveness of ice and chemical cold packs but also an education of the intricacies and challenges of research and the need for proper planning. Inserting the thermocouples went better than expected in part because of my prior experience in starting IV’s. Several problems arose during the data collection. To solve the problem of cold packs sliding off the side of the leg, I would change the method used to locate a midpoint on the thigh. By measuring from the patella rather than the lateral side of the knee, the cold packs would have been centered directly on the top of the muscle while the subject was lying on the table. Another problem was that the surface thermocouples would at times vary in temperature by two or three degrees. I believe this was due to air pockets in the crushed ice packs. I am still unsure of how to correct this problem.

I am continuing to further analyze the data in preparing to submit an abstract for a professional conference. I am also preparing a manuscript for submission to a journal. I hope to be able to use the data from this research project to educate emergency medicine and pre-hospital care personnel because they are the first to treat injuries, and by using proper cryotherapy techniques, they will be able to decrease recovery times, resulting in better patient care.

References

1. Blair E. Clinical Hypothermia. New York, NY: McGraw-Hill Book Co., 1964.
2. Grant HD, et al. Emergency Care. Upper Saddle River, NJ: Prentice-Hall Inc., 1995.
3. Knight KL. Cryotherapy in Sport Injury Management. Champaign, IL: Human Kinetics, 1995.
4. Knight KL. ICE for immediate care of injuries. Phys Sportsmedicine. 1982; 10(2): 137.
5. Knight KL, Rubley M, Brucker JB, Huff JM, Bernards SA. Knee surface temperature changes on uninjured subjects during and following application of tree post-operative crotherapy devices. Presented at the National Athletic Trainers Association Annual Meeting. Los Angeles, Dec 2001.
6. Merrick MA, Ranking JM, Andres FA, Hinman CL. A preliminary examination of crotherapy and secondary injury in skeletal muscle. Med Science Sports Exer. 1999; 31:1516-21.
7. Sanders MJ. Mosby’s Paramedic Textbook. St. Louis, MO: Mosby-Year Book Inc., 1994. 8. US Department of Transportation, National Highway Traffic Safety Administration. Emergency Medical Care: A Manuel for the Paramedic in the Field. 1985.