Development and validation of an environmental heat strain risk assessment (EHSRA) index using structural equation modeling based on empirical relations

BACKGROUND@#Need to a simple, available, accurate, comprehensive, and valid indicator is felt to assess thermal effects. Therefore, the present study was aimed to develop and validate the environmental heat strain risk assessment (EHSRA) index using structural equation modeling (SEM) based on empirical relations.@*METHODS@#This cross-sectional study was performed on 201 male workers in environments with various climatic conditions. The heart rate and tympanic temperature of the individuals were monitored at times of 30, 60, and 90 min after beginning the work. At these times, values of dry temperature, wet temperature, globe temperature, and air velocity were also measured and metabolism rate and clothing thermal insulation value were estimated. At the end, a theoretical model was depicted in AMOS software and obtained coefficients were applied to develop a novel index. The scores of this indicator were categorized into four risk levels via ROC curves and validate using linear regression analysis.@*RESULTS@#Indirect effect coefficients of the globe temperature, dry temperature, wet temperature, air velocity, metabolism, and clothing thermal insulation variables on the tympanic temperature were computed by 0.77, 0.75, 0.69, 0.24, 0.49, and 0.39, respectively. These coefficients were applied to develop the index. Optimal cut-off points of boundaries between risk levels included 12.02, 15.88, and 17.56. The results showed that the EHSRA index justified 75% of the variations of the tympanic temperature (R@*CONCLUSIONS@#The novel index possesses appropriate validity. It was suggested that this indicator is applied and validated in various environments in the next studies.

Comparison of the Impact of an Optimized Ice Cooling Vest and a Paraffin Cooling Vest on Physiological and Perceptual Strain

BACKGROUND: Ice cooling vests can cause tissue damage and have no flexibility. Therefore, these two undesirable properties of ice cooling vest were optimized, and the present study was aimed to compare the impact of the optimized ice cooling vest and a commercial paraffin cooling vest on physiological and perceptual strain under controlled conditions. METHODS: For optimizing, hydrogel was used to increase the flexibility and a layer of the ethylene vinyl acetate foam was placed into the inside layer of packs to prevent tissue damage. Then, 15 men with an optimized ice cooling vest, with a commercial paraffin cooling vest, and without a cooling vest performed tests including exercise on a treadmill (speed of 2.8 km/hr and slope of %0) under hot (40℃) and dry (40 %) condition for 60 min. The physiological strain index and skin temperature were measured every 5 and 15 minutes, respectively. The heat strain score index and perceptual strain index were also assessed every 15 minutes. RESULTS: The mean values of the physiological and perceptual indices differed significantly between exercise with and without cooling vests (P 0.05). CONCLUSIONS: The optimized ice cooling vest was as effective as the commercial paraffin cooling vest to control the thermal strain. However, ice has a greater latent heat and less production cost.

Development and validation of a questionnaire for preliminary assessment of heat stress at workplace

Background: Current heat stress indices are not completely suitable for heat strain screening in developing countries due to their inherent and applied limitations. The aim of this study was development of a questionnaire method entitled "Heat Strain Score Index" [HSSI] in order to perform a preliminary assessment of heat stress at work

Methods: This research included six phases [i] Item generation [ii] Content validity [iii] Reliability analysis [iv]Structure validity [v] Concurrent validity and [vi] Classification of thermal risk level. In item generation phase, 40 items were identified to have impact on the heat strain. Content validity was evaluated by occupational health specialists

Results: In consistency assessment, Cronbach's coefficient [alpha] of items was 0.91. Exploratory factor analysis on items HSSI draft identified four subscales which explained 71.6% of the variance. Correlation between the HSSI score with aural temperature was 0.73. Cut-off point; sensitivity and specificity for upper no thermal strain zone were 13.5, 91% and 50%, respectively. Whereas Cut-off point, sensitivity and specificity for lower thermal strain zone were 18, 86% and 73%

Conclusions: The results showed that 18 variables that were measurable through subjective judgment and observation in the HSSI scale covered heat stress key factors. This scale demonstrated reliability and initial validity in scale were suitable. Therefore HSSI scale for primary evaluation heat stress is appropriate

Design and validate visual fatigue questionnaire in video display terminals operator

Background: Along with the rapid growth of technology its related tools such as computer, monitors and video display terminals [VDTs] grow as well. Based on the studies, the most common complaint reported is of the VDT users

Methods: This study attempts to design a proper tool to assess the visual fatigue of the VDT users. First draft of the questionnaire was prepared after a thorough study on the books, papers and similar questionnaires. The validity and reliability of the questionnaire was confirmed using the content validity index [CVI] beside that of the Cronbach's Coefficient Alpha. Then, a cross-sectional study was carried out on 248 of the VDT users in different professions. A theoretical model with four categories of symptoms of visual fatigue was derived from the previous studies and questionnaires. Having used the AMOS16 software, the construct validity of the questionnaire was evaluated using the confirmatory factor analysis. The correlation co-efficiency of the internal domains was calculated using the SPSS 11.5 software. To assess the quality check index and determining the visual fatigue levels, visual fatigue of the VDT users was measured by the questionnaire and visual fatigue meter [VFM] device. Cut-off points were identified by receiver operating characteristic curves

Results: CVI and reliability co efficiency were both equal to 0.75. Model fit indices including root mean of squared error approximation, goodness of fit index and adjusted goodness of fit index were obtained 0.026, 0.96 and 0.92 respectfully. The correlation between the results measured with the questionnaire and VFM-90.1 device was-0.87. Cut-off points of the questionnaire were 0.65, 2.36 and 3.88. The confirmed questionnaire consists of four main areas: Eye strain [4 questions], visual impairment [5 questions] and the surface impairment of the eye [3 questions] and the out of eye problems [3 questions]

Conclusions: The visual fatigue questionnaire contains 15 questions and has a very remarkable validity and reliability. Using this questionnaire and its findings, one will be able to identify, assess and finally prevent the effective factors of VDT users' visual fatigue

Validation of a questionnaire for heat strain evaluation in women workers

Physiological, anthropometrical and thermal perceptual are the most important factors affecting thermoregulation of men and women in workplaces. The purpose of this study was determining the validity of a questionnaire method for assessing women's heat strain in workplaces. This cross-sectional study was carried out on 96 healthy women. Data were continuously collected over a period of 3 months [July-September] in 2012. Mean +/- [SD] of age was found to be 31.5 +/- 7.48 years, of height 1.61 +/- 0.05 m, of weight 61.55 +/- 10.35 kg, and of body mass index 23.52 +/- 3.75 kg/m[2] in different workplaces. Heart rate and oral temperature were measured by heart rate monitoring and a medical digital thermometer, respectively. Subjects completed a draft questionnaire about the effective factors in the onset of heat strain. After collecting the questionnaires, the data were analyzed by applying Cronbach's a calculation, factor analysis method, Pearson correlation and receiver operator characteristic curves using the SPSS 18 software. The value for Cronbach's alpha was found to be 0.68. The factor analysis method on items of draft questionnaire extracted three subscale [16 variables] which they explained 63.6% of the variance. According to the results of receiver operator characteristic curve analysis, the cut-off questionnaire score for separating people with heat strain from people with no heat strain was obtained to be 17. The results of this research indicated that this quantitative questionnaire has an acceptable reliability and validity, and a cut-off point. Therefore it could be used in the preliminary screening of heat strain in women in warm workplaces, when other heat stress evaluation methods are not available

Evaluation of the effect of noise on the rate of errors and speed of work by the ergonomic test of two-hand co-ordination

Among the most important and effective factors affecting the efficiency of the human workforce are accuracy, promptness, and ability. In the context of promoting levels and quality of productivity, the aim of this study was to investigate the effects of exposure to noise on the rate of errors, speed of work, and capability in performing manual activities. This experimental study was conducted on 96 students [52 female and 44 male] of the Isfahan Medical Science University with the average and standard deviations of age, height, and weight of 22.81 [3.04] years, 171.67 [8.51] cm, and 65.05 [13.13] kg, respectively. Sampling was conducted with a randomized block design. Along with controlling for intervening factors, a combination of sound pressure levels [65 dB [A], 85 dB [A], and 95 dB [A]] and exposure times [0, 20, and 40] were used for evaluation of precision and speed of action of the participants, in the ergonomic test of two hand coordination. Data was analyzed by SPSS18 software using a descriptive and analytical statistical method by analysis of covariance [ANCOVA] repeated measures. The results of this study showed that increasing sound pressure level from 65 to 95 dB in network 'A' increased the speed of work [P < 0.05]. Increase in the exposure time [0 to 40 min of exposure] and gender showed no significant differences statistically in speed of work [P > 0.05]. Male participants got annoyed from the noise more than females. Also, increase in sound pressure level increased the rate of error [P < 0.05]. According to the results of this research, increasing the sound pressure level decreased efficiency and increased the errors and in exposure to sounds less than 85 dB in the beginning, the efficiency decreased initially and then increased in a mild slope

study on work ability index and physical work capacity on the base of fax equation vo[2] max in male nursing hospital staff in Isfahan, Iran

The purpose of this research is to establish the ability of employees by work ability index [WAI], physical work capacity [PWC], and finding the correlation between them. Establishing the PWC index with attention to WAI values for the purpose of saving in costs and time of PWC measurements is another aim of this project. The present research is an analytic cross-sectional and one-trail study. The study population consists of 228 randomly selected registered nurses from hospitals in Isfahan [Iran]. The WAI and PWC were established through WAI questionnaire and Fax equation and by using ergometer bicycle, respectively. The resulting data were analyzed using SPSS 16 software. Average WAI and PWC among the study population were 38.25 +/- 4.4 and 4.45 +/- 0.7, respectively. Pearson test results showed no significant correlation between PWC and WAI in different age groups [r=0.3 and P>0.05]. Multiple linear regression analysis showed that the variables of age and diagnosed diseases were the most effective factors of WAI [beta=0.18 and P>0.05]. Pearson test revealed a significant correlation between the number of diagnosed diseases and PWC index in age groups of 40-49 years. Average WAI in this research, like other studies on similar jobs is in the acceptable level of >36. Work ability index and PWC index in different age groups did not show a significant correlation and this suggests that there are essential discrepancies in work ability evaluations made by each index and it is not possible to predict PWC index using WAI values. Given the PWC results and the level of nursing staff's activity [low, medium] the WAI is a suitable instrument to establish the professionals' abilities. This study revealed that 27.6% of individuals were subject to medium-low work ability risk [WAI<37], which was 1.8 times that of Finland's professional health Institute, which could be caused by shift working and increased working hours