Hilde Færevik

Effects of wearing aircrew protective clothing on physiological and cognitive responses under various 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.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°C at 80% RH, 23°C at 63% RH and 40°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°C ambient temperature condition in comparison with 0°C and 23°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°C than at 23°C (p = 0.006) or 0°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.

Optimizing the performance of phase-change materials in personal protective clothing systems.

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.

Comparison of three different prehospital wrapping methods for preventing hypothermia - a crossover study in humans

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 Hiblers 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 Hiblers 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. Hiblers 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 (Hiblers 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.

Cooling vest for improving surgeons' thermal comfort: a multidisciplinary design project.

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.

The dry-heat loss effect of melt-spun phase change material fibres

Phase change materials (PCM) have the ability to store latent heat when they change phases, a property that gives clothing that incorporates PCM its cooling effect. This study investigated the effect of dry-heat loss (cooling) of a novel melt-spun PCM fibre on the basis of the area covered, mass, the latent heat of fusion and melting temperature, compared to a known PCM clothing product. PCM fibres with melting temperatures of 28.4 and 32.0°C and PCM packs with melting temperatures of 28.0 and 32.0°C were studied. The results showed that the PCM fibres had a larger initial peak cooling effect than that of the PCM packs. The duration of the cooling effect of PCM fibres was primarily dependent on the PCM mass and the latent heat of fusion capacity, and secondly on the covered area and melting temperature of the PCM. Practitioner Summary: This study investigates the cooling effect of PCM fibres on a thermal manikin. The PCM fibres had a high but short-lasting cooling effect. This study contributes to the knowledge of how the bodys temperature regulation may be affected by the cooling properties of clothing that incorporates PCM.

Leg exercise and core cooling in an insulated immersion suit under severe environmental conditions.

INTRODUCTION This study was conducted to examine whether the greater rate of heat production through intermittent leg exercise would offset an elevated rate of heat loss and thereby decrease the rate of core cooling during immersion in severe conditions when wearing an insulated immersion suit. METHODS On two separate days, seven male subjects were immersed in 2 degrees C water with air temperature of -2 degreesC, wind speed of 5 m x s(-1), and waves of 30-40 cm high. Subjects wore wool underwear, flight suits, and neoprene immersion suits. They were immersed for 180 min while remaining passive (NonEx) or performing moderate leg exercise for 5 min every 20 min (LegEx). Metabolism, rectal and skin temperatures, and skin heat flux were measured. Subjective evaluation of thermal and physical comfort was obtained. RESULTS After 180 min core cooling was less in LegEx (0.3 degrees C) compared to NonEx (0.9 degrees C). This was attributed to a 31% increase in total heat production, but there was only a 21% increase in total heat loss when performing leg exercise compared to lying still. Leg exercise also improved thermal and physical comfort. DISCUSSION The results suggest that wearing an insulated immersion suit under extreme environmental conditions and 5 min of leg exercise every 20 min might improve heat balance, resulting in a net heat gain (10%) compared to lying still in the water. As a result, shivering intensity is reduced, core cooling rate, and thermal and physical comfort is improved. This procedure potentially provides a practically significant survival advantage at sea and also under severe conditions.

The effect of melt-spun phase change material fibre garments on skin temperature in humans

Phase change materials (PCM) have the ability to store latent heat, a property that is utilized in the making of thermo regulating clothing [1]. The melt-spun PCM fibre [2] has a polyester sheath and PCM filled core, giving the fibre its cooling properties. By virtue of being a fibre, it enables production of a knitted fabric with high air and moisture permeability as well as high flexibility qualities. The flexible knitted fabric allows for better-fitting clothes [3], and larger area of the body surface to be covered and exposed to the cooling effects of the melt-spun PCM fibre. The aim of this study was to investigate the effects of a melt-spun PCM fibre sweater with PCM melting temperature at 28.4 °C and crystallisation temperature at 25.2 °C, on the skin temperatures of the upper body and perceived thermal sensation and comfort in a hot environment.

Protective jacket enabling decision support for workers in cold climate

The cold and harsh climate in the High North represents a threat to safety and work performance. The aim of this study was to show that sensors integrated in clothing can provide information that can improve decision support for workers in cold climate without disturbing the user. Here, a wireless demonstrator consisting of a working jacket with integrated temperature, humidity and activity sensors has been developed. Preliminary results indicate that the demonstrator can provide easy accessible information about the thermal conditions at the site of the worker and local cooling effects of extremities. The demonstrator has the ability to distinguish between activity and rest, and enables implementation of more sophisticated sensor fusion algorithms to assess work load and pre-defined activities. This information can be used in an enhanced safety perspective as an improved tool to advice outdoor work control for workers in cold climate.

Safety at Sea: Improving Search and Rescue (SAR) Operations in the Barents Sea

In this paper, we select some of the crucial issues for future search and rescue (SAR) operations in the Barents Sea. The different nations that are involved and the resources necessary to build emergency preparedness due to the climatic conditions are thus important factors. This paper summarizes the state of the art within these areas while also indicating future development needs. The special requirements for life saving equipment on vessels due to the climate and requirement on personal protective equipment related to accidental immersion are also essential and thus presented in this paper. In addition, safe haven designs where the vessel itself is designed to provide shelter for personnel in distress is also a topic chosen to be addressed.Copyright

Initial heat stress on subsequent responses to cold water immersion while wearing protective clothing

INTRODUCTION In cold water emergency situations, helicopter aircrew will enter the water with a raised body temperature due to wearing immersion suits. Prewarming has been demonstrated to accelerate core cooling during subsequent cold water immersion (CWI) when wearing swimsuits. For this study we hypothesized that wearing an immersion suit would slow the rate of cooling in subjects who were prewarmed compared to those kept in a normothermic state. METHODS Two different groups of male subjects (age, 24.7 +/- 4.2 yr; height, 183.1 +/- 6.5 cm; weight, 86.7 +/- 15.0 kg; body fat, 16.8 +/- 3.3%) were used to gather data under two conditions: prewarming by exercise (Warm-CWI) and baseline (Base-CWI) when wearing a dry immersion suit (2.97 Clo). In Warm-CWI, seven subjects rested for 20 min and then cycled on an ergometer cycle for 20 min before immersion in water at 5 degrees C for 140 min. In Base-CWI, six subjects were directly immersed in 5 degrees C water after resting. RESULTS Tre and Tsk were significantly higher after Warm-CWI at start of CWI, resulting in faster core cooling rate, and a drop in Tre and Tsk during the first 10 min. In the long term, the overall core cooling did not differ between Warm-CWI (0.34 +/- 0.11 degrees C x h(-1)) and Base-CWI (0.31 +/- 0.05 degrees C x h(-1)). DISCUSSION Wearing a dry immersion suit eliminates long-term differences in core cooling between prewarmed subjects and those kept in a normothermic state. When entering cold water with a raised Tre and Tsk, different thermal responses during the first 10 min are expected, but this does not alter long-term core cooling.