Yutaka Tochihara

Bathing before sleep in the young and in the elderly.

Abstract In this study we investigated the effects of bathing on the quality of sleep in 30 elderly people (ages 65–83 years) and in 30 young people (ages 17–22 years) in their homes. Room temperature did not vary significantly during the nights that data were acquired, ranging from 8 to 12°C. After bathing and at the beginning of sleep, the mean (SE) rectal temperatures of the young and the elderly were 37.8u2009(0.08) and 37.5u2009(0.07)°C, respectively, and were higher by 0.7u2009(0.13) and 0.6u2009(0.07)°C, respectively, than when the subjects had not bathed. At the beginning of the sleep after bathing in the young subjects, skin temperature was 32.5u2009(0.24) and 1.5u2009(0.34)°C higher than when those subjects had not bathed. In the elderly, however, there were no significant differences in skin temperature with and without prior bathing because they used electric blankets during sleep. After bathing, the young people reported “warmth” in their hands and/or legs, while the elderly more often reported “good sleep” or “quickness of falling asleep”. During the first 3u2009h of sleep, body movements were less frequent after bathing for both the young and the elderly subjects. The results suggest that a bath before sleep enhances the quality of sleep, particularly in the elderly.

Physiological responses and manual performance in humans following repeated exposure to severe cold at night

We evaluated human physiological responses and the performance of manual tasks during exposure to severe cold (–25°C) at night (0300–0500xa0hours) and in the afternoon (1500–1700xa0hours). Thirteen male students wearing standard cold protective clothing occupied a severely cold room (–25°C) for 20xa0min, and were then transferred to a cool room (10°C) for 20xa0min. This pattern of exposure was repeated three times, for a total time of exposure to extreme cold of 60xa0min. The experiments were started either at 1500xa0hours or 0300xa0hours and measurements of rectal temperature, skin temperature, blood pressure, performance in a counting task, hand tremor, and subjective responses were made in each condition. At the end of the experiment at night the mean decrease in rectal temperature [0.68xa0(SEMxa00.04)°C] was significantly greater than that at the end of the experiment in the afternoon [0.55xa0(SEM 0.08)°C, P<0.01]. After the second cold exposure at night the mean increase in diastolic blood pressure [90xa0(SEMxa02.0)xa0mmHg] was significantly greater than that at the end of the second cold exposure in the afternoon [82xa0(SEMxa02.8)xa0mmHg, P<0.01]. At the end of the second cold exposure at night, mean finger skin temperature [11.8xa0(SEMxa00.8)°C] was significantly higher than that at the comparable time in the afternoon [9.0xa0(SEMxa00.7)°C, P<0.01]. Similarly for the toe, mean skin temperature at the start of the second cold exposure at night [25.6xa0(SEMxa01.5)°C] was significantly higher than in the afternoon [20.1xa0(SEMxa00.8)°C, P<0.01]. The increased skin temperatures in the periphery resulted in increased heat loss. Since peripheral skin temperatures were highest at night, the subjects noted diminished sensations of thermal cold and pain at that time. Manual dexterity at the end of the first cold exposure at night [mean 83.7xa0(SEMxa03.6)xa0times·min–1] had decreased significantly more than at the end of the first cold exposure in the afternoon [mean 89.4xa0(SEMxa03.5)xa0times·min–1, P<0.01]. These findings of a lowered rectal temperature and diminished manual dexterity suggest that there is an increased risk of both hypothermia and accidents for those who work at night.

Evaluation of summertime thermal comfort in automobiles

Abstract In the summertime drivers frequently, feel severe discomfort just after entering an automobile that has been parked in the sunshine. Thermal conditions in automobiles are influenced mainly by ambient temperature, passenger seat temperature, and radiation from inner panels. The purpose of this study was to evaluate the contribution of these thermal factors on the thermal acceptance, of drivers. The thermal environment in automobiles was reproduced in a climatic chamber. Radiation from inner panels in an automobile was reproduced using a radiation panel, which circulates water internally, and passenger seat temperature was also controlled by the same method. The thermal conditions of the climatic chamber were altered by the combination of ambient temperature, passenger seat temperature, and the radiation panel. Seven healthy male students were exposed to 22 or 23 conditions. They evaluated their thermal acceptance of these conditions during the exposure. The results of multiple regression analysis show that ambient temperature was the only factor that influenced thermal acceptance throughout the exposure. The contribution of passenger seat temperature was small just after the exposure began, and got higher over time. The radiation panel made little contribution to thermal acceptance. In conclusion, it is suggested that thermal discomfort just after entering an automobile that has been parked in the sunshine is induced exclusively by the severe ambient temperature.

Water vapour permeability resistance through clothing material at combinations of temperature and pressure that simulate elevated altitudes

Abstract Combinations of temperature and pressure at a simulated high altitude upon the water vapour permeability resistance of textile materials was investigated through a series of experiments. We developed a new apparatus in order to measure the water vapour resistance with and without temperature differences either side of the specimens. Although the effect of temperature on the water vapour resistance was found to be small, that of atmospheric pressure was significant. That is, the water vapour resistance decreases with the increasing altitude because the water vapour diffusion coefficient in the air increases with the increasing altitude due to the decrease in the atmospheric pressure. It was found that the condensation flux in the specimens increases with the increase in simulated altitude. Furthermore, the water vapour resistance decreases remarkably as the amount of condensation increases. This means that condensation is enhanced at high altitude because of a decrease in the water vapour resistance and of the reduced saturated water vapour concentration at lower temperatures. This may cause discomfort or coldness and a decrease in body temperature.