Effects of Cold and Hot Stimuli on Peripheral Vascular System of Workers in Hot Environments

The static conditions of peripheral vascular systems were observed on the workers in hot environments and dynamic changes to cold and hot stimuli were also examined.Six men 22 to 27 years old engaged in hot environments for about three years were originally selected for this study, and simultaneously six clerks of the same ages were examined as a control group. They were measured before and after working in summer and winter respectively on the changes of capillary figures and pulse waves in the left fingertip skin at the room temperature, than on the changes to cold and hot stimuli (7±2°C, 49±2°C) for every ten seconds applied on the back of the same hand. The results obtained were as follows: 1) The effects of working in hot environments were not found in the width of skin capillary figures, but a tendency toward lowering after working was seen in the visible height of capillaries, especially in summer. 2) Ordinary redustions in the amplitude of pulse waves were observed after working in both seasons, but these changes were not shown as characterisitic of the hot environmental group. It is considered that the tension of peripheral blood vessels may be changed by working. 3) The chnges to cold stimuli before working were observed to be more insensitive (prolongation of the reaction time) in summer, more sensitive in winter in the hot environmental group, than that of the control group, and no significant changes were found between the both groups after working. The changes to hot stimuli before working were also observed to be more sensitive in the hot envitonmental group than that of the control group, especially in summer, but no significant difference after working was shown between the both groups. In winter, a tendency of sensitive reaction was seen in the hot environmental group after working compared with the control group, in spite of no significant difference was recognized in both groups before working. The workers engaged in hot environments are relatively stable for cold stimuli and labile for hot stimuli after working and it suggests that the acclimatized workers have been prepared to escape the heat stress in the body. 4) As a rule, the crest time shortens in winter compared with summer. The ratio of the time necessary for constriction of blood vessels to the duration of pulse waves (t/d) was lower in the hot environmental group than the control group before working, especially in summmer, but this difference was not significant between the both groups after working.