Study Of Mean Skin Temperature And Thermal Comfort Of The Elderly In High Temperature Environment

With the frequent occurrence of hot weather events around the world,high temperature environments have a significant impact on human physical and mental health.As the elderly age,their metabolic function,thermoregulatory response,cardiovascular flexibility,cardiac output and resistance to high temperatures gradually decrease which makes hot weather more harmful to them.The indoor high temperature environment is very likely to affect the physiological indicators and subjective feelings of the elderly.The mean skin temperature is an important physiological index for evaluating heat stress in the elderly,but studies on the mean skin temperature in the elderly are limited.In this study,a new formula for calculating mean skin temperature was established based on the relationship between local skin temperature and environmental parameters.And the relationship between mean skin temperature and local skin temperature and indoor dry bulb temperature was established.The results of this paper can provide methodological support and data support for the rapid estimation of mean skin temperature of elderly people in summer.In this paper,a suitable formula for calculating the mean skin temperature of elderly people was established based on field measurement data.Twenty-four elderly people in nursing homes were selected as subjects.Indoor high temperature environmental parameters,physiological parameters and subjective parameters of subjects were measured for 17 days.Among them,the environmental parameters included: indoor temperature,relative humidity,wind speed,and globe temperature;physiological parameters included: heart rate,eardrum temperature,local skin temperature,and blood pressure;subjective parameters included: thermal sensation and thermal comfort.First,this study used experimental data to establish a formula for calculating the mean skin temperature suitable for the elderly based on the potential relationships between physiological parameters,environmental parameters and the relative area of local skin.The significance of local skin temperature and environmental composite index was analyzed to obtain a statistically significant local skin temperature.The weight of each local skin temperature was determined based on the local skin relative body area and sensitivity to the environment.The new mean skin temperature and existing mean skin temperature were analyzed and compared with PSI(Physiological Strain Index)to verify the adaptability and accuracy of the new skin temperature.The fitting relationshipIVbetween the new skin temperature and local skin temperature was obtained.The results showed that the correlation between the new skin temperature and PSI was 0.719,and the sensitivity R2 was 0.517,which was higher than the existing mean skin temperature.The adaptability and accuracy was also verified.The correlation between the new mean skin temperature and temple temperature and back of hand temperature were 0.824 and 0.787,respectively,and the sensitivity R2 was 0.946 and 0.946,which could quickly estimate the mean skin temperature using the local temperature.Then,a method to evaluate the heat stress status of the elderly by local skin temperature was developed.Eleven local skin temperature characteristics in different environments were analyzed.The typical local skin temperature was determined based on the sensitivity of local skin temperature to the environmental composite index and the correlation between local skin temperatures.And it was estimated based on the fitting relationship between the typical local skin temperature and both the existing mean skin temperature and other local skin temperatures.The predicted mean skin temperature was compared with the true value to verify the accuracy of the prediction,and the typical local skin temperature was also fitted with PSI and graded for the typical local skin temperature.The results showed that the neck temperature and head temperature were higher,followed by the body trunk skin temperature,and the lowest was the extremities;the slopes obtained from the primary fit relationship equations of ET(Effective Temperature),RSI(Relative Strain Index)and dorsal hand skin temperature were 0.125,1.674,and R2 were 0.930,0.918,respectively;the R2 of the fitted relationship equation between the skin temperature of the back of the hand and other local skin temperatures and the six existing mean skin temperatures were greater than 0.84 and 0.93,respectively;the partitions of the skin temperature of the back of the hand were: none or mild [35.2,35.9],moderate(35.9,36.7],and severe(36.7,37.4].Finally,the acceptable limit values and partial surrogate limit values of the dry bulb temperature were calculated based on the subjective parameters including thermal sensation and thermal comfort,and the objective parameters including mean skin temperature and eardrum temperature.The goodness of fit of each fitting formula was judged based on the indoor dry bulb temperature and the R2 of thermal sensation,thermal comfort,mean skin temperature and eardrum temperature.The relationship between the parameters and the trend of change were judged according to each fitting formula and graph.The upper acceptable limit and partial surrogate limit values of dry bulb temperature were calculated from thermal sensation,thermal comfort,mean skin temperature and eardrum temperature using the fitting formula.The results showed that the acceptable limit of dry bulb temperature obtained from thermal sensation was 33.3℃and the partial surrogate limit was 41.0℃.The acceptable limit of dry bulb temperature obtained from thermal comfort was 33.4℃ and the partial surrogate limit was 42.1℃;the results obtained from the objective parameters mean skin temperature and eardrum temperature were as follows: the acceptable limit of dry bulb temperature obtained from mean skin temperature was 34.0℃ and the partial surrogate limit was 39.5℃.The acceptable limit of dry bulb temperature obtained from the eardrum temperature was 31.6℃,and the partial surrogate limit was 39.5℃.In this paper,the method of adapting to calculate the mean skin temperature of the elderly was studied and the relationship between the average skin temperature and the typical skin temperature was analyzed.The above method can determine the mean skin temperature level of the elderly more conveniently and to monitor the physiological state of the elderly indoors,realize the real-time monitoring of the mean skin temperature,provide a simpler method to calculate the mean skin temperature for the study of indoor heat stress of the elderly in a hot environment,and also provide a scientific basis for the health protection of the elderly in a hot weather indoor environment.