Phase-change materials (PCM) can be used to reduce thermal stress and improve thermal comfort for workers wearing protective clothing. The aim of this study was to investigate the effect of PCM in protective clothing used in simulated work situations. We hypothesized that it would be possible to optimize cooling performance with a design that focuses on careful positioning of PCM, minimizing total insulation and facilitating moisture transport. Thermal stress and thermal comfort were estimated through measurement of body heat production, body temperatures, sweat production, relative humidity in clothing and subjective ratings of thermal comfort, thermal sensitivity and perception of wetness. Experiments were carried out using 2 types of PCM, the crystalline dehydrate of sodium sulphate and microcapsules in fabrics. The results of 1 field and 2 laboratory experimental series were conclusive in that reduced thermal stress and improved thermal comfort were related to the amount and distribution of PCM, reduced sweat production and adequate transport of moisture.

BackgroundAccidental hypothermia increases mortality and morbidity in trauma patients. Various methods for insulating and wrapping hypothermic patients are used worldwide. The aim of this study was to compare the thermal insulating effects and comfort of bubble wrap, ambulance blankets / quilts, and Hibler's method, a low-cost method combining a plastic outer layer with an insulating layer.MethodsEight volunteers were dressed in moistened clothing, exposed to a cold and windy environment then wrapped using one of the three different insulation methods in random order on three different days. They were rested quietly on their back for 60 minutes in a cold climatic chamber. Skin temperature, rectal temperature, oxygen consumption were measured, and metabolic heat production was calculated. A questionnaire was used for a subjective evaluation of comfort, thermal sensation, and shivering.ResultsSkin temperature was significantly higher 15 minutes after wrapping using Hibler's method compared with wrapping with ambulance blankets / quilts or bubble wrap. There were no differences in core temperature between the three insulating methods. The subjects reported more shivering, they felt colder, were more uncomfortable, and had an increased heat production when using bubble wrap compared with the other two methods. Hibler's method was the volunteers preferred method for preventing hypothermia. Bubble wrap was the least effective insulating method, and seemed to require significantly higher heat production to compensate for increased heat loss.ConclusionsThis study demonstrated that a combination of vapour tight layer and an additional dry insulating layer (Hibler's method) is the most efficient wrapping method to prevent heat loss, as shown by increased skin temperatures, lower metabolic rate and better thermal comfort. This should then be the method of choice when wrapping a wet patient at risk of developing hypothermia in prehospital environments.

This study assessed the effects of exposure to cold (-14 and -9 °C), cool (-4 and 1 °C) and moderate warm (10 and 20 °C) environments on aerobic endurance performance-related variables: maximal oxygen consumption (VO(2max)), running time to exhaustion (TTE), running economy and running speed at lactate threshold (LT). Nine male endurance athletes wearing cross-country ski racing suit performed a standard running test at six ambient temperatures in a climatic chamber with a wind speed of 5 m s(-1). The exercise protocol consisted of a 10-min warm-up period followed by four submaximal periods of 5 min at increasing intensities between 67 and 91 % of VO(2max) and finally a maximal test to exhaustion. During the time course mean skin temperature decreased significantly with reduced ambient temperatures whereas T (re) increased during all conditions. T (re) was lower at -14 °C than at -9 and 20 °C. Running economy was significantly reduced in warm compared to cool environments and was also reduced at 20 °C compared to -9 °C. Running speed at LT was significantly higher at -4 °C than at -9, 10 and 20 °C. TTE was significantly longer at -4 and 1 °C than at -14, 10 and 20 °C. No significant differences in VO(2max) were found between the various ambient conditions. The optimal aerobic endurance performance wearing a cross-country ski racing suit was found to be -4 and 1 °C, while performance was reduced under moderate warm (10 and 20 °C) and cold (-14 and -9 °C) ambient conditions.

Heat stress can be a significant problem for pilots wearing protective clothing during flights, because they provide extra insulation which prevents evaporative heat loss. Heat stress can influence human cognitive activity, which might be critical in the flying situation, requiring efficient and error-free performance. This study investigated the effect of wearing protective clothing under various ambient conditions on physiological and cognitive performance. On several occasions, eight subjects were exposed for 3 h to three different environmental conditions; 0 degrees C at 80% RH, 23 degrees C at 63% RH and 40 degrees C at 19% RH. The subjects were equipped with thermistors, dressed as they normally do for flights (including helmet, two layers of underwear and an uninsulated survival suit). During three separate exposures the subjects carried out two cognitive performance tests (Vigilance test and DG test). Performance was scored as correct, incorrect, missed reaction and reaction time. Skin temperature, deep body temperature, heart rate, oxygen consumption, temperature and humidity inside the clothing, sweat loss, subjective sensation of temperature and thermal comfort were measured. Rises in rectal temperature, skin temperature, heart rate and body water loss indicated a high level of heat stress in the 40 degrees C ambient temperature condition in comparison with 0 degrees C and 23 degrees C. Performance of the DG test was unaffected by ambient temperature. However, the number of incorrect reactions in the Vigilance test was significantly higher at 40 degrees C than at 23 degrees C (p = 0.006) or 0 degrees C (p = 0.03). The effect on Vigilance performance correlated with changes in deep-body temperature, and this is in accordance with earlier studies that have demonstrated that cognitive performance is virtually unaffected unless environmental conditions are sufficient to change deep body temperature.

A laparoscopic surgeon sometimes experiences heat-related discomfort even though the temperature situation is moderate. The aim of this project was to design a cooling vest using a phase change material to increase thermal comfort for the surgeon. The project focused on the design process to reveal the most important parameters for the design of a cooling vest that could be demonstrated in a clinical setting. We performed an entire design process, from problem analysis, situation observations, concept for a prototype, temperature measurements, and a final design based on clinical testing. The project was conducted by a multidisciplinary team consisting of product designers, engineers, physiologists, and surgeons. We carried out four physiological demonstrations of one surgeon's skin temperatures and heart rate during different laparoscopic procedures. A commercially available cooling vest for firemen and two proof-of-concept prototypes were tested alongside a reference operation without cooling. To aid the final design, one person went through a climate chamber test with two different set-ups of cooling elements. The final design was found to improve the conditions of our test subject. It was found that whole trunk cooling was more effective than only upper trunk cooling. A final design was proposed based on the design process and the findings in the operating room and in the laboratory. Although the experiences using the vest seemed positive, further studies on several operators and more surgical procedures are needed to determine the true benefits for the operator.