Biomedical subjects

Yutaka Tochihara

Publications and source records attributed to Yutaka Tochihara.

15 recordsLinked to original sources

PubMed2006

Physiological and subjective responses to low relative humidity in young and elderly men.

In order to compare the physiological and the subjective responses to low relative humidity of elderly and young men, we measured saccharin clearance time (SCT), frequency of blinking, hydration state of the skin, transepidermal water loss (TEWL), sebum level recovery and skin temperatures as physiological responses. We asked subjects to evaluate thermal, dryness and comfort sensations as subjective responses using a rating scale. Eight non-smoking healthy male students (21.7+/-0.8 yr) and eight non-smoking healthy elderly men (71.1+/-4.1 yr) were selected. The pre-room conditions were maintained at an air temperature (Ta) of 25 degrees C and a relative humidity (RH) of 50%. The test-room conditions were adjusted to provide 25 degrees C Ta and RH levels of 10%, 30% and 50%. RH had no effect on the activity of the sebaceous gland or change of mean skin temperature. SCT of the elderly group under 10% RH was significantly longer than that of the young group. In particular, considering the SCT change, the nasal mucous membrane seems to be affected more in the elderly than in the young in low RH. Under 30% RH, the eyes and skin become dry, and under 10% RH the nasal mucous membrane becomes dry as well as the eyes and skin. These findings suggested that to avoid dryness of the eyes and skin, it is necessary to maintain greater than 30% RH, and to avoid dryness of the nasal mucous membrane, it is necessary to maintain greater than 10% RH. On the thermal sensation of the legs, at the lower humidity level, the elderly group felt cooler than the young group. On the dry sensation of the eyes and throat, the young group felt drier than the elderly group at the lower humidity levels. From the above results, the elderly group had difficulty in feeling dryness in the nasal mucous membrane despite being easily affected by low humidity. On the other hand, the young group felt the change of humidity sensitively despite not being severely affected by low humidity. Ocular mucosa and physiology of skin by dryness showed no difference by age. In the effect of longer exposure (180 min.) to low RH, only TEWL showed a slight decrease after 120 minutes in 30% RH, and all the measured results showed no noticeable differences compared with the result at 120 minutes.

Acclimatization↗

PubMed2006

Physiological and subjective responses to low relative humidity.

In order to investigate the influence of low relative humidity, we measured saccharin clearance time (SCT), frequency of blinking, heart rate (HR), blood pressure, hydration state of skin, transepidermal water loss (TEWL), recovery sebum level and skin temperature as physiological responses. We asked subjects to judge thermal, dryness and comfort sensations as subjective responses using a rating scale. Sixteen non-smoking healthy male students were selected. The pre-room conditions were maintained at an air temperature (Ta) of 25 degrees C and a relative humidity (RH) of 50%. The test room conditions were adjusted to provide a Ta of 25 degrees C and RH levels of 10%, 30% and 50%.RH had no effect on the activity of the sebaceous gland and on cardiovascular reactions like blood pressure and HR. However, it was obvious that low RH affects SCT, the dryness of the ocular mucosa and the stratum corneum of the skin and causes a decrease in mean skin temperature. Under 30% RH, the eyes and skin become dry, and under 10% RH the nasal mucous membrane becomes dry as well as the eyes and skin, and the mean skin temperature decreases. These findings suggested that to avoid dryness of the eyes and skin, it is necessary to maintain an RH greater than 30%, and to avoid dryness of the nasal mucous membrane, it is necessary to maintain an RH greater than 10%. Subjects felt cold immediately after a change in RH while they had only a slight perception of dryness at the change of humidity.

Adult↗

PubMed2005

Effects of ambient temperature steps on thermal comfort requirements.

The purpose of this study was to determine the thermal comfort requirements for steps in temperature. Thirty male subjects were exposed for 50 min to a 34 or 37 degrees C condition, and then quickly transferred to a cooler environment of 31, 28, 25, and 22 degrees C for 50 min. Mean skin temperature was continuously measured, and the subjects reported their thermal sensation and comfort sensation every 2 min. Just after the step changes, the mean skin temperature immediately decreased, while the thermal sensation overshot and gradually rose again. Both the skin temperature and the thermal sensation seemed to reach a constant level within about 20 min. However, there were differences in the mean skin temperature and the neutral temperature derived from the correlation between the ambient temperature and the thermal sensation even 50 min after the steps, due to the thermal environmental condition before the changes of temperature. The change in the neutral temperature with time was expressed as two attenuating equations. These equations indicate that there is an obvious difference between the neutral temperatures due to the thermal condition before step changes, and that it takes >50 min after the step changes to reach the steady state. It is expected that these equations predict in quantitative terms the thermal comfort requirements within a given experimental condition.

Acclimatization↗

PubMed2005

Thermal environment and subjective responses of patients and staff in a hospital during winter.

The purpose of this study was to ascertain the actual conditions of the thermal environment and the symptoms of patient and staff (nurses and nurses' aides) during winter in a hospital. We measured the ambient temperature and humidity in sickrooms, nurse stations, and corridors. The subjects included 36 patients and 45 staff members. The existence of low humidity environments (relative humidity was less than 40%) in a hospital during winter was confirmed, and the levels of low humidity reached those known to promote the spread of influenza viruses. Thermal comfort of patients was not directly connected to the low humidity in sickrooms. However, 54.9% and 73.4% of patients were conscious of itchy skin and thirst, respectively. The majority of the staff members were working with itchy skin and thirst. These results suggested that extreme low humidity in a hospital during winter presents problem that should be solved quickly.

Adult↗

PubMed2005

Effects of exercise in the heat on thermoregulation of Japanese and Malaysian males.

The effect of low-intensity exercise in the heat on thermoregulation and certain biochemical changes in temperate and tropical subjects under poorly and well-hydrated states was examined. Two VO2max matched groups of subjects consisting of 8 Japanese (JS) and 8 Malaysians (MS) participated in this study under two conditions: poorly-hydrated (no water was given) and well-hydrated (3 mL x Kg(-1) body weight of water was provided at onset of exercise, and the 15th, 35th and 55th min of exercise). The experimental room in both countries was adjusted to a constant level (Ta: 31.6+/-0.03 degrees C, rh: 72.3+/-0.13%). Subjects spent an initial 10 min rest, 60 min of cycling at 40% VO2max and then 40 min recovery in the experimental room. Rectal temperatures (Tre) skin temperatures (Tsk), heart rate (HR), heat-activated sweat glands density (HASG), local sweat rate (M sw-back) and percent dehydration were recorded during the test. Blood samples were analysed for plasma glucose and lactate levels.The extent of dehydration was significantly higher in the combined groups of JS (1.43+/-0.08%) compared to MS (1.15+/-0.05%). During exercise M sw-back was significantly higher in JS compared to MS in the well-hydrated condition. The HASG was significantly more in JS compared to MS at rest and recovery. Tre was higher in MS during the test. Tsk was significantly higher starting at the 5th min of exercise until the end of the recovery period in MS compared to JS. In conclusion, tropical natives have lower M sw-back associated with higher Tsk and Tre during the rest, exercise and recovery periods. However, temperate natives have higher M sw-back and lower Tsk and Tre during experiments in a hot environment. This phenomenon occurs in both poorly-hydrated and well-hydrated states with low intensity exercise. The differences in M sw-back, Tsk and Tre are probably due to a setting of the core temperature at a higher level and enhancement of dry heat loss, which occurred during passive heat exposure.

Adaptation, Physiological↗

PubMed2005

Effects of short-term exercise in the heat on thermoregulation, blood parameters, sweat secretion and sweat composition of tropic-dwelling subjects.

This study investigates the effects of a short-term aerobic training program in a hot environment on thermoregulation, blood parameters, sweat secretion and composition in tropic-dwellers who have been exposed to passive heat. Sixteen healthy Malaysian-Malay male volunteers underwent heat acclimation (HA) by exercising on a bicycle ergometer at 60% of VO2max for 60 min each day in a hot environment (Ta: 31.1+/-0.1 degrees C, rh: 70.0+/-4.4%) for 14 days. All parameters mentioned above were recorded on Day 1 and at the end of HA (Day 16). On these two days, subjects rested for 10 min, then cycled at 60% of VO2max for 60 min and rested again for 20 min (recovery) in an improvised heat chamber. Rectal temperature (Tre), mean skin temperature (Tsk) heart rate (HR), ratings of perceived exertion (RPE), thermal sensation (TS), local sweat rate and percent dehydration were recorded during the test. Sweat concentration was analysed for sodium [Na+]sweat and potassium. Blood samples were analysed for biochemical changes, electrolytes and hematologic indices. Urine samples were collected before and after each test and analysed for electrolytes.After the period of acclimation the percent dehydration during exercise significantly increased from 1.77+/-0.09% (Day 1) to 2.14+/-0.07% (Day 16). Resting levels of hemoglobin, hematocrit and red blood cells decreased significantly while [Na+]sweat increased significantly. For Tre and Tsk there were no differences at rest. Tre, HR, RPE, TS, plasma lactate concentration, hemoglobin and hematocrit at the 40th min of exercise were significantly lower after the period of acclimation but mean corpuscular hemoglobin and serum osmolality were significantly higher while no difference was seen in [Na+]sweat and Tsk. It can be concluded that tropic-dwelling subjects, although exposed to prolonged passive heat exposure, were not fully heat acclimatized. To achieve further HA, they should gradually expose themselves to exercise-heat stress in a hot environment.

Acclimatization↗

PubMed2005

Thermal sensation and comfort during exposure to local airflow to face or legs.

The present study examined the contribution of local airflow temperature to thermal sensation and comfort in humans. Eight healthy male students were exposed to local airflow to their faces (summer condition) or legs (winter condition) for 30 minutes. Local airflow temperature (Tf) was maintained at 18 degrees C to 36 degrees C, and ambient temperature (Ta) was maintained at 17.4 degrees C to 31.4 degrees C. Each subject was exposed to 16 conditions chosen from the combination of Tf and Ta. Based on the results of multiple regression analysis, the standardized partial regression coefficient of Tf and Ta were determined to be 0.93 and 0.13 in the summer condition, and 0.71 and 0.36 in the winter condition at the end of the exposure. Also, thermal comfort was observed to depend closely on the interrelation between Tf and Ta. The present data suggested that local airflow temperature is an important thermal factor regarding thermal sensation and comfort.

Adult↗

PubMed2005

Hematological change in venous blood of the lower leg during prolonged sitting in a low humidity and hypobaric environment.

The present study examined the effects of low humidity and hypobaric conditions on hematological change in venous blood of the lower leg during quiet prolonged sitting. Ten healthy male students participated as the subjects after singing a consent form to participate in this study. Their diet and water intake were controlled from 19:00 on the day before the experiments. The subjects sat for 130 min in a climatic chamber. Four experimental conditions in the chamber were designed from a combination of relative humidity (20% or 60%) and air pressure (sea level or equivalent to an altitude of 2,000 m). Ambient temperature was maintained at 24 degrees C in every condition. Venous blood was sampled from the lower leg before and after exposure to the experimental conditions, and was analyzed for blood viscosity and hematological indices. Also, body weight and leg circumference were measured as indices of total water loss and edema, respectively. Regarding the results of ANOVA, significant interactions between humidity and time were observed in blood viscosity, red blood cell count and hematocrit (each p<0.05). However, there were no significant differences in these indices among the conditions. Significant increases were observed in leg circumference (p<0.01), platelet count (p<0.05) and total protein (p<0.05) after the exposure compared with those before the exposure. There were no noticeable effects of hypobaric conditions in every measurement. In conclusion, prolonged sitting seems to be a more hazardous factor for thrombogenesis low humidity and hypobaric conditions during a long-distance flight.

Adult↗

PubMed2005

Work in artificial cold environments.

The physiological characteristics of work in cold stores, as a typical artificial cold environment, are reviewed mainly from our various field and experimental studies. There are about 4,000 cold stores in Japan, and 85% of them are kept at temperatures below -20 degrees C. Although the duration of cold exposure per stay in a cold store was very short, forklift workers entered the cold stores very frequently. Cold stress and the decrease in workers' performance were the same as for continuous exposure to cold. Since the peripheral skin temperature of subjects at night is higher than that in the afternoon, they are less likely to feel cold or pain sensation at night. However, there was a marked decrease in rectal temperature and in manual performance. There is an increased risk of both hypothermia and accidents for those who work at night. The cold store workers, however, had adapted to cold through daily repeated cold exposures.

Adult↗

PubMed2004

Comparison of thermal manikins of different body shapes and size.

Differences between manikins may be present due to manikin body shapes (male versus female). In order to examine such differences a study was designed. Comparisons were carried out based on: (1) tight versus loose clothing; (2) serial versus parallel calculation models; (3) even versus uneven clothing (insulation) distribution; and (4) the effect of donning clothes. Differences were observed between female and male manikins depending on body shape. However, these differences were within the range that was observed in the Subzero project, and were comparable with differences between manikins of male body shapes. Manikins behaved differently according to clothing adjustments. Tight-fitting clothes resulted in smaller differences. The effects of donning clothes were more pronounced with the serial calculation model, while the results generated by the serial and parallel calculation models differed more if the insulation was unevenly distributed (24% and 12% respectively). In order to examine the effect of body size, two baby manikins were compared to an adult manikin. The experimental conditions involved air layer insulation measurements (AL), lying on the back on an insulating surface (OB), and lying on the back on an insulating surface, covered with a sheet (OBS, baby manikins only). The acquired AL insulation for all manikins were very similar. The insulation value of adult manikin tested under condition OB differed from the others. This was related to flexible joints allowing the arms and legs to be in contact with the insulating surface, while baby manikins retained their arms and legs in the air. The baby manikins performed similarly in OBS tests.

Adult↗

PubMed2004

Heat and water vapour transfer of protective clothing systems in a cold environment, measured with a newly developed sweating thermal manikin.

A moveable sweating thermal manikin has recently been developed. Thermal and water-vapour resistances of three kinds of cold-protective clothing ensembles, laminated with polytetrafluoroethylene, polyurethane and without a laminate were measured, with the aid of the manikin in a cold environment of 5 degrees C with a relative humidity of 70% and an air velocity of around 1.5 m s(-1). Two sweating rates of 65 and 130 g m(-2) h(-1) were employed. Supplied heat fluxes in both of the sweat rates ranged from 350 W m(-2) to 400 W m(-2). To maintain a comfortable condition, the skin wettedness (w) (mean weighted value) had to be kept at < or = 0.6. The measurements obtained from the manikin when testing the three ensembles were w=0.3 (approximately) for the low sweat rate and w > or = 0.6 for the high sweat rate, irrespective of the property differences among the ensembles. In addition, the condensation in the ensembles in comparison with those calculated from an analytical equation is discussed. Condensation mass fluxes in the ensembles obtained by experiment and those from the calculation agreed sufficiently well. Thus, distribution of the condensation in the ensembles was estimated using the equation.

Cold Temperature↗

PubMed2004

Physiological and subjective responses in the elderly when using floor heating and air conditioning systems.

The purpose of this study was to investigate the effects of a floor heating and air conditioning system on thermal responses of the elderly. Eight elderly men and eight university students sat for 90 minutes in a chair under the following 3 conditions: air conditioning system (A), floor heating system (F) and no heating system (C). The air temperature of sitting head height for condition A was 25 degrees C, and the maximum difference in vertical air temperature was 4 degrees C. The air and floor temperature for condition F were 21 and 29 degrees C, respectively. The air temperature for condition C was 15 degrees C. There were no significant differences in rectal temperature and mean skin temperature between condition A and F. Systolic blood pressure of the elderly men in condition C significantly increased compared to those in condition A and F. No significant differences in systolic blood pressure between condition A and F were found. The percentage of subjects who felt comfortable under condition F was higher than that of those under condition A in both age groups, though the differences between condition F and A was not significant. Relationships between thermal comfort and peripheral (e.g., instep, calf, hand) skin temperature, and the relationship between thermal comfort and leg thermal sensation were significant for both age groups. However, the back and chest skin temperature and back thermal sensation for the elderly, in contrast to that for the young, was not significantly related to thermal comfort. These findings suggested that thermal responses and physiological strain using the floor heating system did not significantly differ from that using the air conditioning system, regardless of the subject age and despite the fact that the air temperature with the floor heating system was lower. An increase in BP for elderly was observed under the condition in which the air temperature was 15 degrees C, and it was suggested that it was necessary for the elderly people to heat the room somehow in winter. Moreover, it is particularly important for elderly people to avoid a decrease in peripheral skin temperature, and maintain awareness of the warmth of peripheral areas, such as the leg, in order to ensure thermal comfort.

Adult↗

PubMed2003

Effects of hyperoxia on thermoregulatory responses during feet immersion to hot water in humans.

This study examined effects of hyperoxia on thermoregulatory responses. Eight healthy male students (23.5+/-1.8 yrs) were involved in this study. They immersed their legs in a hot water bath (42 degrees C) for 60 minutes in a climate chamber. The conditions of oxygen concentration of a chamber were set at 21% (control), 25% (25%O(2)), and 30% (30%O(2)). Ambient temperature and relative humidity was maintained at 25 degrees C and 50% in every condition, respectively. Measurements included rectal temperature (Tre), skin temperature at 7 sites, laser Doppler flowmeter (LDF) on the back and forearm as an index of skin blood flow, heart rate, local sweat rate (Msw) on the back and forearm, and total body weight loss (BWL). Increases of Tre at 25%O(2) and 30%O(2) tended to be lower during the immersion than in the control. Mean skin temperature (Tsk) of the control increased gradually after the onset of sweating, while the Tsks at 25%O(2) and 30%O(2) maintained a constant level during sweating. LDFs on the forearm at 25%O(2) and 30%O(2) showed lower increases compared with the control. No significant differences in Msw on the back and the forearm and BWL were seen among the conditions. These results suggested that hyperoxia could not affect sweating responses but elicit an inhibitory effect on thermoregulatory skin blood flow.

Adult↗

PubMed2003

Seasonal effects of sleep deprivation on thermoregulatory responses in a hot environment.

Effects of sleep deprivation and season on thermoregulation during 60 min. of leg-bathing (water temperature of 42 degrees C, air temperature of 30 degrees C, and relative humidity of 70%) were studied in eight men who completed all 4 experiments for normal sleep and sleep deprivation in summer and winter. Rectal temperature (T(re)), skin temperature, total body sweating rate (M(sw-t)), local sweating rate on the back (M(sw-back)) and forearm (M(sw-forearm)), and skin blood flow on the back (SBF(back)) and forearm (SBF(forearm)) were measured. The changes in T(re) (DeltaT(re)) were smaller (P<0.05) for sleep deprivation than for normal sleep regardless of the season. This decrease in DeltaT(re) was significant only in summer (P<0.05). Mean skin temperature (T(mean of)(sk)) was higher (P<0.05) for sleep deprivation than for normal sleep regardless of the season. M(sw-t) was smaller (P<0.05) for sleep deprivation than for normal sleep regardless of season, although M(sw-back) and M(sw-forearm) were similar. SBF(back) and SBF(forearm) tended to be higher for sleep deprivation than normal sleep. The sensitivity of SBF to T(re) was higher (P<0.05) for sleep deprivation than for normal sleep. These data indicate that seasonal differences in thermoregulation were small because of morning time. Sleep deprivation increased dry heat loss and restrained T(re) rise, in spite of decreased sweating rate.

Acclimatization↗

PubMed2002

Effects of room temperature on physiological and subjective responses during whole-body bathing, half-body bathing and showering.

The effects of bathroom thermal conditions on physiological and subjective responses were evaluated before, during, and after whole-body bath (W-bath), half-body bath (H-bath) and showering. The air temperature of the dressing room and bathroom was controlled at 10 degrees C, 17.5 degrees C, and 25 degrees C. Eight healthy males bathed for 10 min under nine conditions on separate days. The water temperature of the bathtub and shower was controlled at 40 degrees C and 41 degrees C, respectively. Rectal temperature (Tre), mean skin temperature (Tsk), blood pressure (BP), heart rate (HR), body weight loss and blood characteristics (hematocrit: Hct, hemoglobin: Hb) were evaluated. Also, thermal sensation (TS), thermal comfort (TC) and thermal acceptability (TA) were recorded. BP decreased rapidly during W-bath and H-bath compared to showering. HR during W-bath was significantly higher than for H-bath and showering (p < 0.01). The double products due to W-bath during bathing were also greater than for H-bath and showering (p < 0.05). There were no distinct differences in Hct and Hb among the nine conditions. However, significant differences in body weight loss were observed among the bathing methods: W-bath > H-bath > showering (p < 0.001). W-bath showed the largest increase in Tre and Tsk, followed by H-bath, and showering. Significant differences in Tre after bathing among the room temperatures were found only at H-bath. The changes in Tre after bathing for H-bath at 25 degrees C were similar to those for W-bath at 17.5 degrees C and 10 degrees C. TS and TC after bathing significantly differed for the three bathing methods at 17.5 degrees C and 10 degrees C (TS: p < 0.01 TC: p < 0.001). Especially, for showering, the largest number of subjects felt "cold" and "uncomfortable". Even though all of the subjects could accept the 10 degrees C condition after W-bath, such conditions were intolerable to half of them after showering. These results suggested that the physiological strains during H-bath and showering were smaller than during W-bath. However, colder room temperatures made it more difficult to retain body warmth after H-bath and created thermal discomfort after showering. It is particularly important for H-bath and showering to maintain an acceptable temperature in the dressing room and bathroom, in order to bathe comfortably and ensure warmth.

Adaptation, Physiological↗