Some pathophysiological aspects of vibration-induced white finger

Effects on blood parameters from hand-arm vibrations exposure

Vibration exposure from handheld tools can affect the hands with neurological symptoms and vibration-induced Raynaud's phenomenon (VRP). The underlying pathophysiological mechanisms are not fully known, however, changes in the composition of blood parameters may contribute to VRP with an increase in blood viscosity and inflammatory response. The aim of this study was to examine the effect on blood parameters in capillary blood from fingers that had been exposed to a vibrating hand-held tool. This study involved nine healthy participants who had been exposed to vibration and an unexposed control group of six participants. Capillary blood samples were collected before and after vibration exposure for the exposed group, and repeated samples also from the control group. The exposed groups were exposed to vibration for a 15-min period or until they reached a 5.0 m/s² vibration dose. Analysis of blood status and differential counting of leucocytes was performed on the capillary blood samples. The results of the blood samples showed an increase in mean value for erythrocyte volume fraction (EVF), hemoglobin, red blood cell count, white blood cell count and neutrophils, as well as a decrease of mean cell volume, mean cell hemoglobin, and mean cell hemoglobin concentration. The increase of EVF and neutrophils was statistically significant for samples taken from the index finger but not the little finger. Even though the study was small it showed that an acute vibration exposure to the hands might increase EVF and neutrophilic granulocytes levels in the capillary blood taken from index fingers.

Health effects associated with occupational exposure to hand-arm or whole body vibration

Workers in a number of different occupational sectors are exposed to workplace vibration on a daily basis. This exposure may arise through the use of powered-hand tools or hand-transmitted vibration (HTV). Workers might also be exposed to whole body vibration (WBV) by driving delivery vehicles, earth moving equipment, or through use of tools that generate vibration at low dominant frequencies and high amplitudes, such as jackhammers. Occupational exposure to vibration has been associated with an increased risk of musculoskeletal pain in the back, neck, hands, shoulders, and hips. Occupational exposure may also contribute to the development of peripheral and cardiovascular disorders and gastrointestinal problems. In addition, there are more recent data suggesting that occupational exposure to vibration may enhance the risk of developing certain cancers. The aim of this review is to provide an assessment of the occupations where exposure to vibration is most prevalent, and a description of the adverse health effects associated with occupational exposure to vibration. This review will examine (1) various experimental methods used to measure and describe the characteristics of vibration generated by various tools and vehicles, (2) the etiology of vibration-induced disorders, and (3) how these data were employed to assess and improve intervention strategies and equipment that reduces the transmission of vibration to the body. Finally, there is a discussion of the research gaps that need to be investigated to further reduction in the incidence of vibration-induced illnesses and injuries.

Acute vibration increases alpha2C-adrenergic smooth muscle constriction and alters thermosensitivity of cutaneous arteries

The vascular symptoms of hand-arm vibration syndrome, including cold-induced vasospasm, are in part mediated by increased sensitivity of cutaneous arteries to sympathetic stimulation. The goal of the present study was to use a rat tail model to analyze the effects of vibration on vascular function and alpha-adrenoceptor (AR) responsiveness. Rats were exposed to a single period of vibration (4 h, 125 Hz, constant acceleration 49 m/s2 root mean square). The physical or biodynamic response of the tail demonstrated increased transmissibility or resonance at this frequency, similar to that observed during vibration of human fingers. Morphological analysis demonstrated that vibration did not appear to cause structural injury to vascular cells. In vitro analysis of vascular function demonstrated that constriction to the alpha1-AR agonist phenylephrine was similar in vibrated and control arteries. In contrast, constriction to the alpha2-AR agonist UK14304 was increased in vibrated compared with control arteries, both in endothelium-containing or endothelium-denuded arteries. The alpha2C-AR antagonist MK912 (3 x 10(-10) M) inhibited constriction to UK14304 in vibrated but not control arteries, reversing the vibration-induced increase in alpha2-AR activity. Moderate cooling (to 28 degrees C) increased constriction to the alpha2-AR agonist in control and vibrated arteries, but the magnitude of the amplification was less in vibrated compared with control arteries. Endothelium-dependent relaxation to acetylcholine was similar in control and vibrated arteries. Based on these results, we conclude that a single exposure to vibration caused a persistent increase in alpha2C-AR-mediated vasoconstriction, which may contribute to the pathogenesis of vibration-induced vascular disease.

The role of leukocytes in the pathogenesis of vibration-induced white finger

Vibration white finger (VWF) is an occupational disorder associated with long-term exposure to hand-transmitted vibration. The condition exhibits features of secondary Raynaud's phenomenon. The etiology is unknown. The aim of this study was to examine the role of leukocyte rheology in the pathogenesis of VWF. Fifty-two male subjects divided into two groups were exposed to controlled acute hand-transmitted vibration. One group consisted of 29 workers who have all had occupational exposure to handheld vibration and all suffered from VWF (mean age 46.9 years, range 22-66). The second group consisted of 23 controls. Venous blood was analyzed from the dorsum of the hand before and after vibration to determine granulocyte deformability, granulocyte morphology, and white blood cell count with differential. There was a subpopulation of hard and poorly deformable granulocytes in the VWF group when compared with controls (p < 0.05). Acute hand-transmitted vibration had no in vitro effect on leukocyte rheology in either group. Leukocyte rheology may play a role in the pathogenesis of microvascular disease and tissue ischemia in VWF, although whether this is a cause or an effect of the disorder is not clear.

The hemorheologic effects of hand-transmitted vibration

Vibration white finger (VWF) is an ischemic condition of the hands that is associated with long-term exposure to hand-held vibration tools. The pathophysiology of VWF remains unknown. The aim of this study was to assess the hemorheologic effect of acute hand-transmitted vibration. This study investigated 52 men divided into two groups: VWF = 29, mean age 46.9 years (range twenty-two to sixty-six); Controls = 23, mean age 42.8 years (range twenty to sixty-four). Each subject gripped a vibrating handle for seven minutes thirty seconds at a vibration frequency of 120 Hz with an amplitude of displacement of 0.25 mm. Venous blood was analyzed before and after acute vibration to determine the hematocrit, the plasma hemoglobin concentration, plasma viscosity, and red cell deformability, expressed as red cell transit time (RCTT). At rest, there was no significant difference in RCTT, plasma viscosity, hematocrit, and plasma hemoglobin concentration between the VWF group and controls. Acute vibration did, however, significantly increase the red cell transit time in the VWF group but not in the control group. In both groups vibration resulted in a significant increase in plasma viscosity, hematocrit, and plasma hemoglobin concentration in hand venous blood. Moreover, in each group there was a highly significant correlation between the change in plasma viscosity and the change in the hemoglobin concentration and the hematocrit. The authors conclude that hand-transmitted vibration is associated with hemoconcentration.

Vibration white finger

Vibration white finger (VWF) occurs in workers who use vibrating tools. On exposure to vibration or cold, patients experience blanching, numbness and pain in the fingers due to exaggerated vasoconstriction. This may involve both central sympathetic hyper-reactivity and local vasoactive factors. In advanced cases, hypertrophy of vascular smooth muscle causes arterial occlusion and ulceration. Diagnostic tests for VWF are unreliable. In early cases, cessation of vibration exposure arrests the progression of disease and may cause symptom remission. Patients with VWF should keep themselves warm, especially their hands, which they should place in warm water at intervals during the day; they should not smoke. Vasoactive drugs may be beneficial in some patients. In the UK, Industrial Injuries Disablement Benefit and compensation are sometimes available. Improved design of tools and restrictions on their operating time have been the main factors leading to a worldwide decline in the incidence of VWF since the early 1970s.

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.

Vibration disease

Today, in this age of technology, vibration caused by machinery is an almost universal hazard. Vibration transferred from a machine to the human body may cause discomfort, a reduction of performance, and even injury. Vibratory manual tools may cause damage to the circulatory system of the upper extremities (Raynaud's syndrome), to the peripheral nerves (peripheral neuropathy), and to the bones and joints (aseptic necrosis, fatigue fractures, degenerative joint disease). Vehicles and machines causing floor vibration cause degenerative disc disease of the lumbar spine. The pathogenesis of vibration injuries is still not completely clear and there is no effective treatment. Some of the abnormalities are irreversible and may cause permanent decrease of working ability, and even unemployment. This is why prevention is so important. Prevention is complex, including technical and organizational measures, use of individual protective clothing and footwear, and medical supervision both before and during employment. Workers who are exposed to vibration should be protected against other aggravating factors such as cold and noise, etc. Vibration-induced injuries are recognized in law in many countries as grounds for financial compensation. Their cost to industry is rising and, unless a means of prevention or cure is found, will continue to do so in the foreseeable future.

Vibration white finger, digital blood pressure, and some biochemical findings on workers operating vibrating tools in the engine manufacturing industry

A clinical and laboratory investigation was carried out on 76 operators using pneumatic hand grinders and impact wrenches in the engine manufacturing industry. Twenty-two vibration-exposed workers (28.9%) had no symptoms in the hands (stage 0 of the Stockholm Workshop scale), 34 (44.7%) were affected with sensorineural disturbances in the fingers (stage SN), and 20 (26.3%) suffered from vibration white finger (VWF stages 1-2-3). In the vibration-exposed operators and in 30 comparable referents not exposed to vibration, finger systolic blood pressure (FSP) was measured on a test finger and on a control finger after digit cooling to 30 degrees C and 10 degrees C. The results of the cold provocation test were expressed as percent change of FSP by cooling the test finger from 30 degrees C to 10 degrees C (FSP%t, 10 degrees) and as digital/brachial pressure index during local cooling at 10 degrees C (DPIt, 10 degrees). After cold provocation the mean values of FSP%t, 10 degrees and DPIt 10 degrees were more significantly reduced in the vibration-exposed workers with VWF than in those without VWF and the referents (p less than 0.001). The cold provocation test was found to differentiate between VWF subjects with stages 1-2 and stage 3 (p less than 0.02). It is concluded that the measurement of FSP combined with finger cooling is a useful laboratory test to diagnose objectively Raynaud's phenomenon of occupational origin. The vibration-exposed workers and the referents were also tested for serum levels of immunoglobulins and complement and for daily excretion of urinary free catecholamines. Between the reference and vibration groups no differences in the mean values of the immunologic parameters and urinary catecholamines were found. The meaning of these findings is discussed.