Cardiovascular responses to autonomic stimuli in workers with vibration-induced white finger

Cardiovascular responses to autonomic stimulation were assessed in 11 grinding operators affected with vibration-induced white finger (VWF) and in 11 comparable healthy controls by measuring blood pressures, heart rate and systolic time intervals (STI) during a hand-grip test, an arithmetic test and an orthostatic test. Digital circulatory function was also investigated by measurement of finger systolic pressure (FSP) during local cooling with water at 30 degrees C, 15 degrees C and 10 degrees C. The increase in diastolic blood pressure and heart rate during the stress tests was greater in the VWF workers than in the controls. The STI values such as total electromechanical systole and left ventricular ejection time, were found to be shorter in the VWF subjects than in the controls at rest and during both the circulatory stress tests and the recovery periods (0.001 less than p less than 0.05). Multiple regression analysis showed that vibration exposure was the major predictor of STI during the stress tests, while age, smoking and drinking habits did not contribute substantially to the explained variation in STI. The reduction in FSP by local cooling from 30 degrees C to 15 degrees C and 10 degrees C was greater in VWF operators than in controls (p less than 0.001), and total closure of the digital arteries at 10 degrees C was observed in 8 VWF workers (72.7%). In all subjects significant relationships were found between the reduction in FSP at 10 degrees C and the decrease in STI during circulatory stress activities (p less than 0.001). The findings in this study suggest an association between vibration exposure, digital vasospasm and increased cardiac sympathetic tone, the latter being demonstrated by the shortening of STI during the stress tests. It is suggested that excessive sympathetic reflex activity plays the dominant role in the pathogenesis of VWF.