It is important in establishing and improving work management and work planning to estimate the arousal level of workers during operation and monitoring tasks. This paper proposes a technique based on experimental results to estimate the arousal level during job execution.
In this experiment, both a monotonous low workload task which degrades the arousal level and a high workload task which has an awakening action were alternately applied to five subjects for three hours. Skin resistance level (SRL) as an index of arousal level of the autonous nervous system was measured with subjective drowsiness and task performance, that is, signal omission probability for low workload task and both reaction time and error probability for high workload task, as indexes of arousal level of the central nervous system. The following results were obtaind.
(1) The results suggested that SRL as an index of arousal level of the autonous nervous system is significantly related and correlated with subjective drowsiness and signal omission probability as indexes of arousal level of the central nervous sytem.
(2) The average reaction time and the error probability tended to increase by the application of high workload when the arousal level was degraded. The influence of degraded arousal continued for a short time and showed an unfavorable effect on task execution. The degree of this influence, however, differed between subjects.
(3) SRL can be used as an index of arousal level of the autonous nervous system because the measurement is comparatively easy and is little influenced by artifacts due to body movements.
(4) Using SRL at initial high workload period as the standard value, it is possible to quantify the SRL value at arbitrary time by estimating how many times the standard value goes into the SRL value. Based on this quantified value as an index of arousal level, comparison with task performance can be made.
The proposed index of arousal level of the autonous nervous system showed a significant correlation with indexes of the central nervous system. This technique can be applied to various kinds of estimation on human characteristics accompanied with changes in arousal level.

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We conducted a cross-sectional study to investigate the relationship between psychological load and blood pressure using white-collar male employees of a company located in an urban area in June, 1991. Excluding those with diseases which might induce hypertension or those under 20 yr and over 60 yr of age, 570 male subjects were eligible for analysis. Logistic regression analysis was applied to 461 subjects excluding 109 who showed unstable blood pressure level; the dependent variable was blood pressure class which contained 386 normotensives and 75 hypertensives. The explanatory variables were age, obesity, alcohol intake, cigarette smoking, habitual physical exercise, all well-known factors affecting blood pressure level, working time, commuting time, paid annual leave, and type of living (with family or alone) as objective workload, and Karasek's job strain as psychological workload.
Odds ratio of job strain was statistically significant after adjusting for the foregoing factors, but in the case of high job strain, the prevalence of hypertension was low. Theorell has pointed out that contrary to the usual recognition those having a family history of hypertension tended to have a non-complaining life attitude and this indication seems to be the reason for the results of this analysis. Blood pressure is one of the most important problems in the field of industrial health and because of our highly industrialized society, it is necessary to consider psychological workload. Longitudinal observations which take into account psychological workloads must be planned, and personal traits represented by a family history of hypertension should be always taken into consideration.

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By using a Holter electrocardiograph (ECG), we calculated the heart rates of ward nurses on day shift which included different activities. Energy expenditure was calculated from the heart rate data and nurse work load was evaluated. The following results were obtained.
1) Average heart rates during working hours were 86 (beats/min) in children ward nurses, 77 in ophthalmology ward nurses, 85 in surgery ward nurses, 85 in mixed ward nurses, 85 in neurosurgery ward nurses, 81 in circulatory organs ward nurses and 83 in ICU ward nurses.
2) The energy expenditures were calculated to be 1, 891 kcal in childen ward nurse on day shift, 1, 866 kcal in ophthalmology ward nurses, 1, 969 kcal in surgery ward nurses, 1, 899 kcal in mixed ward nurses, 1, 976 kcal in neurosurgery ward nurses, 1, 873 kcal in circulatory organs ward nurses and 1, 744 kcal in ICU ward nurses.
3) The highest energy expenditures in direct nursing care were 918 kcal (48.3%) in mixed ward nurses; in assisting medical examination and treatment, 770 kcal (39.1%) in surgery ward nurses and in indirect nursing care, 679 kcal (35.9%) in children ward nurses.
4) The longest working hours in direct nursing care were 217 min (42.5%) in neurosurgery ward nurses; in assisting medical examination and treatment, 193 min (37.8%) in surgical ward nurses and in indirect nursing care, 207 min (40.5%) in children word nurses.
The results indicated that the energy expenditure calculated from the average heart rate of ward nurses on day shift was very high in all wards. The attributable causes are discussed in this report.

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Enriched air nitrox diving has been conducted to shorten decompression time as well as to reduce risks of decompression sickness. Nine volunteer divers served as subjects for nitrox (-a: 60% N₂ and 40% O₂, and -b: 67.5% N₂ and 32.5% O₂) and air chamber dives of 20 m/60 min, 30 m/60 min and 40 m/60 min. Venous gas emboli (VGE) were examined after surfacing in a series of nitrox dives and of air dives to compare the risks of decompression sickness (DCS). Three divers as a group were compressed in a chamber for each dive. Decompression was carried out according to the Norwegian Navy nitrox decompression tables for the nitrox dives, and for the air dives the Japanese Ministry of Labor tables were used. Decompression time was much shorter in nitrox diving than in air dives for the same dive profiles. All of nitrox-a and air divers showed no VGE nor DCS symptoms after surfacing of 20 m dives. In case of 30 m dives, VGE appeared in one diver (33%) without DCS symptoms in nitrox-a dive but no VGE nor DCS in nitrox-b dive, whereas for the same air dives two subjects (66%) had VGE and DCS symptoms. When the depth was increased to 40 m in the nitrox dive, nitrox-b did not show both VGE and DCS, while the air dive showed one VGE and one DCS. These results suggest that the nitrox dive with suitable decompression schedule reduces the risks of DCS as well as shortening decompression obligation.

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Thirty-six pleural plaque (PP) cases were identified from the worker's periodical health examination and were described in terms of its association with occupational exposure to asbestos and radiographic findings. Based on thorough interviews about job histories, 23 (64%) of the cases were classified to have had “definite” and an additional 5 (14%) with “possible” asbestos-exposed job histories. Asbestos-exposed job histories were represented mostly by plumbing and pipe fitting, insulating, and boiler and pipe insulating. The latency period between initial age of asbestos exposure and age at time of initial plaque detection was 31.1±10.3 yr. Calcified plaques were most prevalent in the diaphragm and the most frequent combination of multi-site PPs was found in the diaphragm and lung fields. All cases were either current or ex-smokers. The findings suggest that subjects with a history of asbestos exposure can be identified through the detection of PPs in chest X-ray films obtained in the worker's periodical health examinations.

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[in Japanese]

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