Die invloed van lugdrukbeitel geïnduseerde vibrasie en geraas op die kardiovaskulêre sisteem van die mens

Abstract

The effect of repeated handling of a hand-held pneumatic tool on the cardiovascular system of the operator was studied. The stressors vibration, noise, combination of vibration and noise and muffled noise were evaluated. Experimental procedures allowed isolation of the effects of different stressors. A vibrating and non- vibrating (simulator) chisel were suspended from ropes. Seated subjects were exposed to stressors as follows: Vibration stressor - gripping the activated pneumatic chisel while wearing double hearing protection. Noise stressor - the chisel was in operation next to the subject whilst gripping the simulator. Combination stressor - the activated pneumatic chisel was gripped without wearing hearing protection. Muffled noise stressor - using double hearing protection while gripping the simulator. The systolic and diastolic blood pressure and heart rate were measured continuously during five successive exposures of each stressor. The hypothesis stated that decreasing cardiovascular responses (adaptation) with repeated exposure to stressors can be expected (hypothesis 1), whilst combined stressors will produce higher reactivity compared to single stressors (hypothesis 2) . Cardiovascular results indicated the following: (i) Systolic and diastolic blood pressure activity were significantly higher than baseline values during all exposures to the vibration stressor. (ii) Four out of five exposures to the noise stressor increased the systolic blood pressure reactivity significantly, whereas the diastolic blood pressure reactivity increased twice only. (iii) The greatest increases in cardiovascular reactivity were observed during the combination stressor with all exposures. (iv) Exposure to muffled noise changed systolic blood pressure and heart rate reactivity slightly. Repeated exposure to stressors resulted in complex cardiovascular reactivity patterns. A decrease in systolic and diastolic pressure reactivity following the first exposure of the vibration, noise and combination stressor could be ascribed to anticipation stress. Diastolic blood pressure reactivity decreased with repeated vibration exposure, although a distinct adaptive response with repetition of each stressor was not observed. Hypothesis 1 was therefore accepted under only certain conditions. Due to opposite variations in diastolic pressure in relation to heart rate reactivity during the combination stressor, the presence of an alternating baroreceptor reflex and "higher centre" control mechanism were suggested. The synergistic effect of the combination stressor on most cardiovascular parameters were significantly higher than for single stressors. Hypothesis 2 was therefore accepted.