Measurements of changes in finger skin blood flow with laser Doppler perfusion imaging (LDPI) in response to cold provocation test (10°C, 10 min) were performed in 12 men suffering from vibration induced white finger (VWF) and 13 exposed controls. The mean perfusion values in both groups reduced markedly as a result of immersion of the hand in cold water. In the controls, however, the mean value increased gradually until the end of the cold provocation, while that in the VWF subjects remained at the lowest level. After removal of the hand from the cold water, the skin blood perfusion in the controls recovered rapidly and nearly reached the baseline value. In the VWF subjects, it had a slight increase immediately following the cold immersion but no tendency to rise as the time span increased. Analysis of covariance controlling for possible confounders revealed that the VWF subjects had significantly lower perfusion values compared to the controls in the last several minutes of the cold provocation and the following recovery. These findings suggest that the LDPI technique enables visualizing and quantifying the peripheral vascular effects of cold water immersion on the finger skin blood perfusion and thus has the potential of providing more detailed and accurate information that may help detect the peripheral circulatory impairment in the fingers of vibrationexposed workers.
Abstracts: Clinical data of workers (40-69 yrs) operating chain saws for a ten-year period from 1986 to 1995 were analyzed to assess the evaluation standard of finger skin temperature for a cold provocation test (10°C 10 min). Screening points of finger skin temperature for screening 191 workers with a vibration induced white finger (VWF) were obtained from receiver operating characteristic (ROC) curves. The screening points at 5 min and 10 min after a cold provocation were approximately equal to 50th percentiles of 217 workers with no symptoms (NS group). The screening points of recovery rates at 5 min and 10 min after a cold provocation almost agreed with 50th percentiles in NS group. A new evaluation standard was prepared in reference to these screening points and finger skin temperatures by fraction in NS group. The new one will be useful for the health care of workers operating vibrating tools under present working conditions.
To clarify the incidence of Raynaud's phenomenon among workers exposed to low level hand-arm vibration for a long time, a sample cohort of workers mainly operating a bush cleaner (the vibration level was 2-4 m/s2rms) were followed up for a period of 20 yr. The sample cohort consisted of 331 male workers mainly working at maintaining public roads or afforesting and gardening on a farm. The examination was based on questionnaires used in special medical examinations for vibration syndrome from 1977 to 1996. Raynaud's phenomenon was observed in 11 subjects. The accumulative occurrence rate increased linearly in the case of more than 11 operating years. The mean number of operating years at the occurrence of Raynaud's phenomenon was 11.7 ± 7.1 yr. The mean total operating time at the occurrence of Raynaud's phenomenon was 3,756 h on the geometric average. Stockholm Workshop scale classified 1 subject as Stage 1 (mild), 4 subjects Stage 2 (moderate) and 6 subjects Stage 3 (severe). By the person-year method, the incidence of Raynaud's phenomenon was 4.48 per 1000 person-year. These findings show that the number of operating years for a bush cleaner should be considered to prevent Raynaud's phenomenon, even though the hand-arm vibration level is low.
To clarify the trends in the number and the severity of vibration syndrome in Wakayama for these 23 years, the records of the medical examinations for vibration syndrome were analyzed with 4,652 (a total of 9,920) private forestry workers exposed to hand-arm vibration. The number of the subjects who took the medical examinations reached a maximum of 1,242 in 1978. After that, it decreased year by year, but remained at about 300 or less from 1988. There was a corresponding increase in age and the number of years of operating chain saws among the subjects examined. The compensated cases reached a maximum number of 393 cases in 1977, and then a drastic decrease was noted. Year by year there was an increase in the number of cases whose medical examinations revealed no abnormality. The regional occupational health care system including the surveillance card, which has been active since 1975, has probably contributed to the decrease or prevention of occurrence of vibration syndrome in Wakayama.
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