The Stockholm Workshop scale for the classification of cold-induced Raynaud's phenomenon in the hand-arm vibration syndrome (revision of the Taylor-Pelmear scale)

A longitudinal study of finger systolic blood pressure and exposure to hand-transmitted vibration

OBJECTIVES

To investigate prospectively the relation between vibration-induced white finger (VWF), exposure to hand-transmitted vibration (HTV) and the cold response of digital arteries in users of vibrating tools.

METHODS

Two-hundred and sixteen HTV workers and 133 control men of the same companies underwent initially a medical examination and a standardised cold test with measurement of the change in finger systolic blood pressure (FSBP) after finger cooling from 30 to 10 degrees C. They were re-examined 1 year later. Tool vibration magnitudes were expressed as frequency-weighted and unweighted r.m.s. accelerations. From the vibration magnitudes and exposure durations, alternative measures of cumulative vibration dose were calculated for each HTV worker, according to the expression: Sigma(alpha)(m)(i)(t)(i), where a ( i ) is the acceleration magnitude on tool i, t ( i ) is the lifetime exposure duration for tool i, and m = 0, 1, 2 or 4.

RESULTS

Among the HTV workers, the initial prevalence and the 1-year incidence of VWF were 18.1 and 1.7%, respectively. At the first examination, the HTV workers with moderate or severe score for VWF showed a significantly increased cold reaction in the fingers when compared with the controls and the HTV workers with no vascular symptoms. At the follow-up, the controls, the asymptomatic HTV workers, and the prevalent cases of VWF did not show significant changes in the cold response of digital arteries. A deterioration of cold-induced digital vasoconstriction was found in the incident cases of VWF. In the HTV workers, vibration doses with high powers of acceleration (i.e., Sigma(alpha)(m)(i)(t)(i) with m > 1) were major predictors of the vasoconstrictor response to cold at the follow-up examination.

CONCLUSIONS

The measurement of FSBP after local cooling may be a helpful objective test to monitor prospectively the change in vibration-induced vascular symptoms. The findings of this longitudinal study suggest a dose-effect relationship between cold-induced digital arterial hyperresponsiveness over time and measures of cumulative vibration exposure. In the controls, the cold response of the digital arteries was stable over 1-year follow-up period.

Diagnosis of vascular injuries caused by hand-transmitted vibration

OBJECTIVE

For a reliable objective diagnosis of vascular injuries in hand-arm vibration syndrome (HAVS), the standardized cold provocation tests--finger skin temperature measurement during hand(s) immersion in cold water (FST test) and finger systolic blood pressure measurement during local cold exposure (FSBP test)--are widely used. In recent years there is a growing controversy regarding the diagnostic value of these tests. The aim of this study was to describe particularly the diagnostic performance of FST and FSBP tests, and also to focus on the problems and uncertainties regarding the test conditions and results, in the laboratory diagnosis of vascular injuries caused by hand-transmitted vibration.

METHOD

A review of pertinent published English- and Japanese-language articles and conference proceedings (between 1976 and 2006) was conducted.

RESULTS

From the reports with regard to diagnostic significance of the FSBP test, it seems to be an important laboratory test for diagnosing vibration-induced white finger (VWF). On the other hand, despite a large number of research studies with the FST test, there is a lack of data for the standardized FST test, which can confirm the value of it in diagnosing VWF. Moreover, there is no agreement on effective parameter/s to quantify and compare the responses in FST induced by immersion in cold water. While assessing and staging vascular injuries in HAVS, inquiry regarding finger coldness appears to be useful.

CONCLUSIONS

As there is no single test with satisfactory diagnostic ability for VWF, at present it is reasonable to use the cold provocation tests as a part of the comprehensive approach to evaluate HAVS patients. In addition to the objective methods, the index of finger coldness may be useful while diagnosing the vascular component of HAVS.

Use of color charts for the diagnosis of finger whiteness in vibration-exposed workers

OBJECTIVES

To assess the usefulness of color charts for the diagnosis of finger whiteness in vibration-exposed workers.

METHODS

A group of 146 forestry and stone workers exposed to hand-transmitted vibration (HTV) were examined twice over 1 year follow up period. The anamnestic diagnosis of finger whiteness was made on the basis of (a) a medical history alone, and (b) the administration color charts which showed changes in the skin color of fingers and hands. The cold response of digital arteries was assessed by measuring the change in finger systolic blood pressure (FSBP) after local cooling from 30 to 10 degrees C (FSBP%(10 degrees )).

RESULTS

Assuming the administration of color charts as the gold standard, the sensitivity and specificity of the medical history alone to diagnose finger whiteness was 88.2 and 93.8%, respectively, at the initial cross-sectional study and 94.4 and 97.7% at the end of the follow-up. Random-intercept linear regression analysis of follow up data showed that after adjustment for several covariates, FSBP%(10 degrees )was significantly associated with finger whiteness assessed by either medical history alone (P < 0.005) or the color charts (P < 0.001). However, a statistical measure of overall fit of regression models (Bayesian Information Criterion) suggested that the color chart method performed better than medical history alone for the prediction of the cold response of digital arteries.

CONCLUSION

The administration of color charts seems to reduce the proportion of false positive responses for finger whiteness in a population of vibration-exposed workers. The color chart method was a more significant predictor of digital arterial hyperresponsiveness to cold than medical history alone. These findings suggest that the use of color charts in clinical and epidemiological studies may be of help to assist in the diagnosis of finger whiteness in vibration-exposed workers.

Interethnic differences at the thermometric response to cold test: functional disorders of blood circulation in hand fingers and exposure to hand–arm vibration

OBJECTIVES

To report some notable aspects regarding thermometric response to cold test in black African subjects compared with Caucasians: both groups comprised persons exposed to hand-arm vibration and controls.

METHODS

An overall sample of 48 workers was examined in order to study their blood circulation in hand fingers: a control group of 12 healthy Caucasian workers never exposed before to hand-arm vibration; 12 Caucasian workers exposed for several years to vibrating tools and affected by occupational Raynaud's phenomenon; 12 healthy black African workers exposed to hand-arm vibration for almost 3 years; and 12 healthy black African workers never exposed to hand-arm vibration. Computerized skin thermometry was performed and thermometric curves were analyzed according to thermometric interpretation criteria such as the area-over-curve (AOC), the fifth minute of recovery/baseline temperature ratio (5REC/BT) and the temperature at the tenth minute of recovery (10REC) after cold test.

RESULTS

Thermometric parameters in Caucasian subjects confirmed the basis of the existing literature in controls (basal finger temperature higher than 32 degrees C and complete recovery to the initial temperature after the cold test) and also in patients with Raynaud's phenomenon (basal temperature often lower than control subjects and slow recovery of finger temperature after cold test). Statistically significant difference was found between healthy Caucasians and healthy black subjects in all the parameters tested: healthy black subjects showed values of AOC and 10REC suggesting almost constantly lower finger temperatures during the thermometry test. Black people, both exposed and non-exposed to hand-arm vibration showed thermometric parameters suggesting poor blood microcirculation, which seems even poorer than in Caucasian people complaining Raynaud's phenomenon.

CONCLUSIONS

Our chronothermometric tests suggest some significant interethnic differences in peripheral microcirculation, which seems rather poor in black African subjects in comparison with Caucasians.

Relationship between self-reported upper limb disability and quantitative tests in hand-arm vibration syndrome

PURPOSE

To establish the relationship between quantitative tests of hand function and upper limb disability, as measured by the Disability of the Arm, Shoulder and Hand (DASH) questionnaire, in hand-arm vibration syndrome (HAVS).

METHOD

A total of 228 individuals with HAVS were included in this study. Each had undergone a full HAVS assessment by an experienced physician, including quantitative tests of vibrotactile and thermal perception thresholds, maximal hand-grip strength (HG) and the Purdue pegboard (PP) test. Individuals were also asked to complete a DASH questionnaire.

RESULTS

PP and HG of the quantitative tests gave the best and statistically significant individual correlations with the DASH disability score (r2 = 0.168 and 0.096). Stepwise linear regression analysis revealed that only PP and HG measurements were statistically significant predictors of upper limb disability (r2 = 0.178). Overall a combination of the PP and HG measurements, rather than each alone, gave slightly better discrimination, although not statistically significant, between normal and abnormal DASH scores with a sensitivity of 73.1% and specificity of 64.3%.

CONCLUSIONS

Measurements of manual dexterity and hand-grip strength using PP and HG may be useful in helping to confirm lack of upper limb function and 'perceived' disability in HAVS.

Laser Doppler imaging of skin blood flow for assessing peripheral vascular impairment in hand-arm vibration syndrome

The objective of this study was to evaluate the usefulness of laser Doppler imaging (LDPI) of the skin blood flow for assessing peripheral vascular impairment in the hand-arm vibration syndrome (HAVS). The subjects were 46 male patients with HAVS, aged 50 to 69 yr, and 31 healthy male volunteers of similar age as controls. A cold provocation test was carried out by immersing a subject's hand on his more severely affected side into cold water at a temperature of 10 degrees C for 10 min. Repeated image scanning of skin blood flow of the index, middle, and ring fingers was performed every 2 min before, during, and after the cold water immersion using a PMI-II laser Doppler perfusion imager. The mean blood perfusion values in the distal phalanx area of the fingers were calculated on each image. The patients suffering from vibration-induced white finger (VWF, n=20) demonstrated significantly lower skin blood perfusion at each interval of the test as compared with those without VWF (n=26) and the controls (p<0.01, ANOVA). The blood perfusions in the HAVS patients were associated with the severity of the symptoms as classified by the Stockholm Workshop scale for vascular staging. When a subject was considered to be positive if any of the tested fingers showing a decreased blood perfusion and/or a delayed recovery pattern, the sensitivity was 80.0%, and the specificity was 84.6% and 93.5% for patients without VWF and the controls, respectively. These results suggest that the LDPI technique could provide detailed and accurate information that may help detect the existence of impaired vascular regulation to cold exposure in the fingers of workers exposed to hand-transmitted vibration.

The Hand-Arm Vibration International Consortium (HAVIC): Prospective Studies on the Relationship Between Power Tool Exposure and Health Effects

OBJECTIVES

The Hand-Arm Vibration International Consortium (HAVIC) is a collaboration of investigators from Europe and North America studying health effects from hand-arm vibration (HAV). Features include prospective design, cross-cohort exposure, and health assessment methods.

METHODS

Two new cohorts (dental hygienists and dental hygiene students), two existing cohorts (Finnish forest workers, and Swedish truck cab assemblers), and a previous population (US shipyard workers) are included. Instruments include surveys, quantitative medical tests, physical examination, and work simulation and data logging to assess exposure. New methods were developed for nerve conduction and data logging.

RESULTS

Findings on the relationship between nerve conduction and skin temperature in HAV-exposed subjects resulted in a new approach to subject warming.

CONCLUSIONS

Integrating established cohorts has advantages over de novo cohort construction. Complex laboratory tests can be successfully adapted for field use.

Quality of life in Swedish workers exposed to hand–arm vibration

The objective of the present study was to analyse whether differences existed among workers exposed to hand-arm vibration (HAV) with regard to quality of life (QoL) issues. One hundred and eight male workers from a heavy manufacturing plant, with and without HAV symptoms, and workers referred to a hand surgery department with severe HAV symptoms participated in the study. The participants attended a clinical interview, were given a physical examination of the hands and administered the Göteborg Quality of Life instrument and the Evaluation of Daily Activity Questionnaire (EDAQ). Results indicated that workers referred to a hand surgery department with more severe HAV symptoms described a lower quality of life, defined here as lower subjective well-being, more symptoms of ill-health and difficulties with activities of daily living (ADL), than workers with no HAV symptoms. Workers from a heavy manufacturing plant with HAV symptoms experienced more difficulties with ADL, especially while working outdoors in cold weather, than workers with no HAV symptoms. Limitations of the present study include the use of a subjective scale to describe HAV symptoms. Further research is recommended on a larger sample of workers at risk for HAV symptoms to develop preventative ergonomic strategies.

Sensory nerve conduction velocities of median, ulnar and radial nerves in patients with vibration syndrome

OBJECTIVE

The present study aimed to clarify the range of involvement for hand-arm vibration syndrome (VS) in the median, ulnar and radial nerves of the hand.

METHODS

Sensory nerve conduction velocities (SCVs) for 3 nerves in the hands and arms were examined for 34 patients with VS and 23 age-matched controls. Neuropathy types were classified by possible carpal tunnel syndrome (CTS), Guyon's syndrome and digital neuropathy in three nerves.

RESULTS

SCV in the median nerve (middle finger, wrist-elbow) and ulnar nerve (little finger, wrist-elbow), and amplitudes of the median nerve (wrist-proximal and distal parts of the middle finger), ulnar nerve (wrist-proximal and distal parts of the little finger; forearm-proximal part of the little finger; upper arm-proximal part of the little finger) and radial nerve (dorsal side of the hand-thumb) were significantly reduced in VS patients compared with controls. According to subject classifications based on the results of SCV and amplitude of nerve action potential, 52.9% of VS patients displayed multi-focal neuropathy including digital neuropathy, possible CTS and/or Guyon's syndrome.

CONCLUSION

These findings suggest that VS affects all three nerves in the hand. According to classification results, the main disorders of peripheral nerves comprise digital neuropathy.

Reduced Epidermal Nerve Density Among Hand-Transmitted Vibration-Exposed Workers

OBJECTIVE

The objective of this study was to evaluate ultrastructural changes of epidermal nerve density (END) in workers exposed to hand-transmitted vibration.

METHODS

Ten male subjects with occupational exposure to hand-transmitted tools for 46.9 hours weekly for an average of 6.5 years were included in this study. We performed a skin biopsy from the forearms and compared the END with 10 age- and gender-matched healthy control subjects.

RESULTS

Nine of the 10 subjects had abnormally low END. The END of the exposed workers was significantly lower than the control group (4.1 +/- 2.8 vs 9.0 +/- 4.3 fibers/mm, P = 0.005). The difference remained even after one subject with possible undiagnosed diabetes was not included (4.3 +/- 2.9 vs 9.6 +/- 4.2 fibers/mm, P = 0.005). The reduction of END did not correlate with the abnormality of nerve conduction studies or quantitative sensory testing.

CONCLUSIONS

The reduction of END suggested the involvement of small-diameter nerve fibers among this population, and such a histologic change might either be independent or precede changes of large myelinated nerve fibers.

Nerve conduction and sensorineural function in dental hygienists using high frequency ultrasound handpieces

BACKGROUND

Oscillatory vibration from industrial power tools poses a well-recognized risk of peripheral nerve injury. There have been reports of elevated vibrotactile perception thresholds (VPT) among dentists, dental technicians, and dental hygienists, using rotary devices and ultrasonics. Elevated VPTs are an indicator of small fiber nerve or mechanoreceptor injury, but the high frequencies associated with dental instruments are presumed by the ISO to exceed physiological response upper thresholds. This study examines nerve conduction and sensorineural deficits in dental hygienists.

METHODS

A cross-sectional study of 94 experienced dental hygienists was conducted to assess peripheral nerve function and clinical signs and symptoms. Specialized testing included measurement of VPTs for three different categories of mechanoreceptors, sensory nerve conduction tests with fractionated digit and palmar segments, and measurement of calibrated pinch force with force sensitive resistors (FSRs) during a simulated procedure.

RESULTS

Chronic hand paresthesias were described by 44.7% of experienced dental hygienists. Sensory nerve conduction velocity (SNCV) across the wrist-palm segment of the median nerve. VPTs were particularly elevated at the FAII mechanoreceptor among experienced dental hygienists. Compared to participants without carpal tunnel syndrome (CTS), as defined by study criteria, 14 experienced hygienists with diagnosed CTS had almost twice the average weekly use of vibratory instruments -8.3 hr versus 4.5 hr, and had SNCV deficits along the digit -47.11 m/sec (+8.70) versus 42.57 m/sec (+8.25), and across the wrist -44.04 m/sec (+7.15) versus 41.36 m/sec (+9.27). There was a distinct subset of dental hygienists (27%) with a combination of low calibrated pinch force in simulations, subjective loss of strength and elevated VPTs, especially in the FAII mechanoreceptor population -110.82 db (+8.57) versus 104.84 db (+6.80) in the rest of the cohort. This subset also had a higher prevalence of paresthesias (67% vs. 39%) and greater cumulative vibration exposure (OR = 1.206 [CI 1.005-1.448]), than other hygienists.

CONCLUSIONS

The high levels of paresthesias observed among dental hygienists appear to be attributable to several pathophysiological mechanisms, including, sensory nerve demyelination at the carpal tunnel and intrinsic to the digits, and dysfunction of fingertip mechanoreceptors. A distinct sub-population appears to exhibit a high level of accumulated abnormality.

The European vibration directive – how will it affect the dental profession?

On 6 July 2005, the EU Physical Agents (Vibration) Directive (2002) came into force across all member states. This will mean that legally enforceable limits on hand-arm vibration exposures will be introduced and that risk management must be set in place at work. This article briefly describes the content of the Directive, how this will affect the dental profession and what measures will be required to ensure compliance.

Standardization of finger systolic blood pressure (FSBP) cooling tests

A finger systolic blood pressure (FSBP) cooling test was introduced in 1977 and standardized during the following years for the optimal provocation and best characterization of an attack of vasospastic Raynaud's phenomenon (RP). The purpose of the present review is to compare and analyse some different techniques used in FSBP cooling tests from different countries and described in the final draft of the international standard, ISO/DIS 14835-2 (2004). The selected FSBP test results indicate to some extent that the tests are reliable and have acceptable diagnostic values despite the use of different techniques to obtain them. However, only a few studies used a zero-pressure FSBP%(0) to verify an ongoing attack of vasospastic RP. Most studies used an abnormal cold reaction FSBP%(A) located below the lower limit of controls, to make the anamnestic diagnosis of RP probable. According to the ISO draft, different types of finger cooling and body thermostating can be used together in the seated or supine position, and FSBP%(A) is indicated to be used for diagnostic purposes. Further studies are recommended to solve future standardization problems not included in the upcoming ISO standard. An international agreement on the presentation and comparison of test results is needed as a supplement to ISO/DIS 14835-2.

Preliminary study on the assessment of peripheral vascular response to cold provocation in workers exposed to hand-arm vibration using laser Doppler perfusion imager

Measurements of changes in finger skin blood flow with laser Doppler perfusion imaging (LDPI) in response to cold provocation test (10 degrees 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 a&curate information that may help detect the peripheral circulatory impairment in the fingers of vibration-exposed workers.

Diagnostic criteria and staging of hand-arm vibration syndrome in the United Kingdom

In the United Kingdom the diagnosis of Hand-arm Vibration Syndrome varies depending on the purpose of that diagnosis. The criteria differ in three situations. More than 100,000 miners and ex-miners with claims for HAVS have been examined using a Medical Assessment Process which included the use of standardised tests. This contract is unique but it has had significant effects on the two other processes. The Industrial Injuries Disablement Benefit Scheme provides a benefit that can be paid to an employed earner because of an accident or Prescribed Disease. New recommendations have been published to remove the anomalies in the present format for assessing HAVS. If implemented the new scheme will recognise the Stockholm Workshop Scales and workers with neurological problems will also be compensated. The Health and Safety Executive will issue new guidance in the near future on the hazards of hand-arm vibration. Health surveillance in the workplace will be fundamental and the HSE propose a tiered approach with levels 1 to 5. Specialist occupational nurses and doctors with training in the diagnosis and assessment of HAVS will be needed for levels 3 and 4. Only at this level may a diagnosis of HAVS be made. The Medical Assessment Process has demonstrated that it is possible to examine a large number of claimants in a standardised manner. The IIAC and HSE recommendations contain very important improvements on the existing positions in the UK and it must be hoped that they will be implemented in the near future.

Impaired manual dexterity and neuromuscular dysfunction in patients with hand-arm vibration syndrome

Manual dexterity and hand functional difficulties in daily life in hand-arm vibration syndrome (HAVS) were investigated in 29 male patients with HAVS and 30 male controls without occupational exposure to hand-arm vibration. Manual dexterity was assessed by measuring the performance time of picking up and transferring 30 red beans, one by one, from one plate to another. Vibrotactile perception thresholds at 125 Hz and grip strength were also examined. Hand functional difficulties in daily life were surveyed with a questionnaire. The HAVS patients had an increased vibrotactile threshold, decreased grip strength, and low performance in transferring beans. Low performances with transfer times over 53 s (2SD from the mean in the controls) were found in 66% of the HAVS patients and 3% of the controls. Bean transfer times in the patients were correlated with an increasing vibrotactile threshold and decreasing grip strength. The transfer times of the patients were also associated with hand functional difficulties such as picking up coins, turning the pages of a newspaper, buttoning clothes, and pouring from a teapot. The patients with a prolonged transfer time over 60 s (3SD from the mean in the controls) were most likely to have hand functional difficulties. The present findings suggest that measurement of the bean transfer time will serve to assess manual dexterity among HAVS patients, and that impaired manual dexterity in patients may be associated with impaired sensory feedback and muscular dysfunction in the fingers and hands.

Occupational hand–arm vibration syndrome in Korea

OBJECTIVES

It is suspected that there is a large number of patients suffering from hand-arm vibration syndrome (HAVS) in Korea. However, no cases have been reported since 1992. This study was conducted to identify HAVS cases and determine the characteristics of the syndrome.

METHODS

In April 2001, the Busan, Ulsan, and Gyeong-Nam Province Occupational Disease Surveillance System (BUGODSS) was established to identify work-related HAVS and other occupational diseases. In the 2 years of this project, occupational physicians from five hospitals in these provinces collected information by way of interviews and questionnaires during mandatory occupational medical examinations. Among the initial 189 suspected HAVS cases, 58 volunteers were given cold-water provocation tests in order to diagnose the vascular component of the disorder.

RESULTS

One hundred fifty-four approximately occupational HAVS cases were identified from ca. 21,000 workers. One hundred fifty about of these cases were male. The cases were most often found in workers from the shipbuilding industry, and the grinder was the most common source of vibration exposure. Cases of sensorineural disorder (SD) were more common than cases of vascular disorder (VD). The mean values of the finger skin temperature and its recovery rate at 5 min and 10 min after cold-water provocation were significantly lower in the group with the VD than in the group with the SD.

CONCLUSIONS

We identified 154 occupational HAVS cases, although no cases have been reported during the occupational medical examinations mandated by the state. The majority of the cases were in workers that used grinders in the shipbuilding industry. We determined that peripheral VD and peripheral SD can progress independently of each other. We conclude that exposure to hand-transmitted vibration (HTV) and HAVS cases are common in shipbuilding industry in Korea. The recovery rate of finger skin temperature after cold-water provocation is one of the useful methods for diagnosing the vascular component of HAVS.

A follow up study of vibration induced white finger in compensation claimants

AIMS

To follow up vibration induced white finger (VWF) in a selected group of 73 vibration exposed workers who claimed unsuccessfully for VWF compensation at a first examination.

METHODS

The VWF claimants were sent to our unit by the National Insurance Institute. The basic compensatory criteria included a positive history of VWF and abnormal cold response of the digital arteries. Following the first unsuccessful examination, over a mean time period of 4.1 (range 1-11) years the National Insurance Institute requested a second examination for all 73 claimants and a third examination for 29. During the follow up period, all subjects continued to work with vibratory tools.

RESULTS

There were 14 new cases who reported white finger during the follow up period. In the new VWF cases, finger blanching attacks became visible after about 3.5 years since the first examination. All incident cases of anamnestic VWF showed an abnormal cold response in the digital arteries and obtained compensation according to the basic compensatory criteria. In the entire sample of VWF claimants, there was a discrepancy between positive history of VWF symptoms at medical interview (55%) and abnormal cold provocation outcomes (19%). Digital arterial hyperresponsiveness to cold was associated with both VWF symptoms and the duration of vibration exposure since the first examination. Over the follow up period, a significant increase in the vasoconstrictor response to cold was observed in the vibration exposed workers with no symptoms of finger whiteness. Abnormal cold response was not associated with either age or smoking habit.

CONCLUSIONS

Cold test measuring finger systolic blood pressure may be considered a useful laboratory method to confirm objectively VWF symptoms and to disclose abnormal cold induced vasoconstrictor response in vibration exposed workers with a negative history of VWF. Medical interview outcomes should be interpreted with caution in medicolegal situations involving VWF claimants.

Vascular and nerve damage in workers exposed to vibrating tools. The importance of objective measurements of exposure time

The aim of the present study was to compare the development of vibration white fingers (VWF) in workers in relation to different ways of exposure estimation, and their relationship to the standard ISO 5349, annex A. Nineteen vibration exposed (grinding machines) male workers completed a questionnaire followed by a structured interview including questions regarding their estimated hand-held vibration exposure. Neurophysiological tests such as fractionated nerve conduction velocity in hands and arms, vibrotactile perception thresholds and temperature thresholds were determined. The subjective estimation of the mean daily exposure-time to vibrating tools was 192 min (range 18-480 min) among the workers. The estimated mean exposure time calculated from the consumption of grinding wheels was 42 min (range 18-60 min), approximately a four-fold overestimation (Wilcoxon's signed ranks test, p<0.001). Thus, objective measurements of the exposure time, related to the standard ISO 5349, which in this case were based on the consumption of grinding wheels, will in most cases give a better basis for adequate risk assessment than self-exposure assessment.

Laser Doppler anemometry distinguishes primary Raynaud phenomenon from VWF syndrome

OBJECTIVES

We evaluated two microcirculatory function-tests, the Laser Doppler (LD)-Anemometry and the Laser Doppler Imager (LDI)-Flowmetry in their value to further elucidate functional behavior of the "Vibration-induced white finger syndrome" (VWF) and to distinguish between Raynaud's phenomenon (RP) of idiopathic or vibration origin.

PARTICIPANTS AND METHODS

Ninety-four patients, suffering from RP were studied (78 patients with primary RP and 16 patients with VWF). Measurement of blood cell velocity (BCV) before and after provocation was obtained by nailfold capillary microscopy and an included Laser detector ("Anemometry"). Digital blood flux was recorded by LDI-Flowmetry during a standardized cooling and rewarming thermal challenge.

RESULTS

"Time to peak" of BCV, a measure of maximal reactive hyperemia was longer in VWF in comparison to primary RP (30.37 versus 19.29 sec P < 0.02), respectively.

CONCLUSION

Based on the fact, that prolongation of reactive hyperemia, an indicator of impaired endothelium-dependent vasodilation is also frequently found in peripheral arterial occlusive disease, it is hypothesized that VWF is not only a microcirculatory vasospastic disorder, but may also be related to atherosclerosis. Anemometry, in association with an appropriate provocation-test, could represent a useful non-invasive method for objectifying diagnosis of VWF in patients with RP.

Vibration exposure and disease in a shipyard: a 13-year revisit

BACKGROUND

In a 1988 study of shipyard workers, a progressive association was observed between cumulative exposure to vibration and the vascular and neurological symptoms of the hand-arm vibration syndrome (HAVS). In 2001, after a decade of exposure reduction and ageing of the workforce, a second study at the same site was initiated.

METHODS

In 2001, 214 subjects were selected; they represented four current weekly vibration exposure time intervals--0 hr, >0 < 5 hr, > or =5 < 20 hr, > or =20 hr. The 1988 and 2000 cross-sectional populations were compared on the basis of exposure duration and current symptoms.

RESULTS

In 2001, the study population was 9.6 years older than the 1988 group. Current weekly exposure hours were similar in the low and medium exposure groups 2001 and 1988, but exposure was reduced by an average of 9.7 hr per week in the highest exposure group (> or =20 hr) in 2001. Symptom severity was regressed polychotomously on estimated exposure (log cumulative hours); the OR was weaker in 2001 than in 1988 for sensorineural symptoms-1.44 [CI 1.04-1.98] versus 2.35 [CI 1.48-3.73]. This was also true for vascular symptoms-1.70 [CI 1.06-2.71] versus 3.99 [CI 2.27-7.01]. Vascular symptoms were more prevalent in the highest lifetime vibration exposure group in 1988 (68.7 vs. 43.2% in 2001); sensorineural symptoms were more prevalent in the least vibration exposed group in 2001 (52.6 vs. 20.7% in 1988).

CONCLUSIONS

The prevalence of vascular symptoms associated with cumulative vibratory exposure was significantly greater in 1988, but neurological symptoms were more common at lower exposure levels in 2001. The presumption that reducing exposure duration alone is sufficient, in the absence of change in vibration magnitude, is not supported by the results of this study.

Skin temperature recovery from cold provocation in workers exposed to vibration: a longitudinal study

BACKGROUND

Vibration white finger (VWF) is characterised by arterial hyperresponsiveness and vasoconstriction following cold provocation. Several years after of removal from exposure, most subjects show improved finger systolic blood pressure (FSBP) under conditions of cold challenge, but continue to report cold hands and finger blanching.

AIMS

To assess the underlying reasons for the persistence of cold symptoms.

METHODS

A total of 204 former users of pneumatic tools with cold related hand symptoms were evaluated and then re-evaluated a year later. Symptoms were evaluated using the Stockholm Workshop Scale. Finger systolic blood pressure per cent (FSBP%) was assessed by comparing digital blood pressure in a cold provoked and normalised state. Fingertip skin temperature was measured during cooling and occlusion and during rewarming and recovery.

RESULTS

There were dramatic improvements in FSBP% (14.3 mm Hg %), modest improvement in recovered skin temperature (0.86 degrees C), and no change in symptom stage. When the most symptomatic subjects (n = 75) were compared with the less symptomatic subjects (n = 129), there were similar inter-test improvements in FSBP%. Skin temperature recovery improved in the less symptomatic (+1.49 degrees C), but did not change in the most symptomatic group (-0.12 degrees C). However, the more symptomatic group had higher temperatures at the initial test, thus qualifying the result.

CONCLUSIONS

Skin temperature recovery after cold challenge in subjects with VWF remains reduced in the symptomatic subjects several years after exposure removal. This is evident even when blood pressure has increased in the setting of cold provocation. Results suggest that in VWF, the dermal circulation remains impaired, even after the restoration of arterial blood pressure in the digits.

Hand-arm vibration syndrome in Swedish car mechanics

AIMS

To assess the occurrence of hand-arm vibration syndrome (HAVS) in Swedish car mechanics, and the relation between HAVS and duration of exposure.

METHODS

A total of 806 mechanics answered a questionnaire on vascular and neurological symptoms, and exposure to vibrations. Mechanics with symptoms, and some mechanics without symptoms, were invited to a clinical examination, including also a timed Allen test. Vascular and neurological symptoms were classified using the Stockholm Workshop scales. The mean daily exposure (mainly using nut-runners) was 14 minutes and the mean exposure duration, 12 years. Published data have shown vibration levels in nut-runners of about 3.5 m/s(2).

RESULTS

In the questionnaire, 24% reported cold induced white finger (WF), 25% persistent numbness, and 13%, reduced grip force. The clinical examination showed a prevalence of vibration induced white finger (VWF) of about 15%, mainly in stage 2, and after 20 years, of 25%. A survival analysis showed similar results. We found that the International Organisation for Standardisation (ISO) model underestimates the risk of VWF. The incidence after 1975 was 19 cases per 1000 person-years. Slow refill times in the timed Allen test were common (15% had a refill time of >20 seconds), and associated with the presence of VWF. The clinical examination revealed neurological symptoms in the hands in about 25% of subjects, mainly at stage 2. After 20 years, the prevalence was 40%. The questionnaire items on WF and numbness both showed likelihood ratios of 13.

CONCLUSION

HAVS is common among Swedish car mechanics in spite of short daily exposure times. This underlines the need for preventive measures.

Hand function tests and questions on hand symptoms as related to the Stockholm workshop scales for diagnosis of hand-arm vibration syndrome

The severity of hand-arm vibration syndrome (HAVS) is usually graded according to the Stockholm workshop scales. Although the Stockholm workshop scales are regarded the gold standard for assessing the severity of HAVS, they are based primarily on subjective symptoms. The aim of the present study was to explore the agreement between Stockholm workshop scales and the outcome from ten well-defined clinical tests commonly used in hand rehabilitation for assessment of hand function. One hundred and eleven vibration-exposed workers participated in the study. Ten objective tests of hand function and four questions on subjective hand symptoms were included. The results indicated that, out of these tests, perception of vibration, perception of touch/pressure and dexterity showed a moderate agreement with Stockholm workshop scales. Among specific questions on hand symptoms, cold intolerance and pain showed a high agreement with Stockholm workshop scales. It is concluded that defined objective tests combined with directed questions on specific hand symptoms, together with the Stockholm workshop scales, may be helpful for diagnosing HAVS.

Short daily exposure to hand-arm vibrations in Swedish car mechanics

The aim of the study was to examine the daily exposure times to hand-arm vibrations in Swedish car mechanics, to test a method for estimating the exposure time without observing the workers for whole days, and to use the results for predicting the prevalence of vibration-induced white fingers (VWF) by the ISO 5349-model. Six garages were surveyed. In each garage, 5-10 car mechanics were observed in random order every 30 seconds throughout working days. The daily exposure time for each mechanic was estimated from the fraction of the observations that the mechanic was exposed. A total of 51 mechanics were observed, most of them on two different working days, yielding estimates for 95 days. The median effective exposure time was 10 minutes per day (95% confidence interval 5-15 minutes, arithmetic mean 14 minutes, maximum 80 minutes), and most of the exposure time was attributable to fastening and loosening nuts. The within-worker and between-worker variability was high (total sigma2 0.99, geometric standard deviation of 2.7). Using the observed exposure time and data on vibration levels of the main tools in Swedish car mechanics (average weighted acceleration level of 3.5 m/s2), the model in ISO-standard 5349 would predict that only three percent of the car mechanics will suffer from VWF after 20 years of exposure. In contrast, a recent survey of VWF showed the prevalence to be 25 percent. The precision of the observation method was estimated and was found to be good for the group daily mean. On the individual level the precision was only acceptable if the daily exposure time was > or = 40 minutes. In conclusion, the daily exposure time was short and the vibration level was limited. Nevertheless, hand-arm vibrations cause VWF in a significant number of car mechanics. The method of observing workers intermittently seemed to work well.

Long-term follow-up study on patients with vibration-induced white finger (VWF)

The prognosis of vibration-induced white finger was investigated with a long follow-up period. From 1975 to 1994, 99 men with hand-arm vibration syndrome who received the annual compulsory examination at San-in Rosai Hospital were followed up for 15 years or longer. Based on the extent of finger-blanching attacks described in the medical records, they were classified according to the vascular stage of the Stockholm workshop scale. In our laboratory, finger systolic blood pressure (FSBP) measurement after finger cooling has been performed since 1989. We compared the stage classification with the results of FSBP measurement after finger cooling in the period 1989-1994. The stage 2 and stage 3 groups showed a significant decrease in FSBP% compared with the stage 0 group. The vascular stage classification based on subjective symptoms in this study was to a certain extent reliable. Although vibration-induced white finger symptoms tended to improve to some extent, 43.2% and 70.4% of patients with stage 2 and stage 3 at first examination, respectively, still suffered from finger blanching attacks after 15 years of observation. Blanching of fingers in advanced stages, especially stage 3, was found to be persistent many years after cessation of vibration exposure.

Hand muscle weakness in long-term vibration exposure

Hand muscle strength was compared between workers regularly exposed to hand-held vibrating tools (n=81) and a non-exposed control group (n=45). Maximal voluntary strengths of hand grip, thumb pinch, thumb palmar abduction and index and little finger abduction were measured. The exposed workers had significantly weaker extrinsic (7%, P<0.01) and intrinsic (19%, P<0.0001) muscles than the controls. Reduced vibration perception was noted in nine vibration-exposed workers who presented with symptoms of hand muscle weakness (P<0.01). Cold intolerance following vibration exposure was found to precede sensorineural and vasospastic symptoms. We therefore postulate that cold intolerance may be a valuable marker for early detection of the adverse effects of vibration. This study emphasizes the need for tests of intrinsic muscle strength in order to evaluate the impairment of hand function observed in vibration-exposed workers.

Hand-arm-vibration syndrome (HAVS): is there a central nervous component? An fMRI study

Hand-held vibrating tools may result in neuromuscular dysfunction and vasospastic problems of the hand. Sensory and motor dysfunction can be explained by injury to peripheral structures, but could also be due to changes in cortical somatotopic mapping of the hand in the brain. The purpose of the present study was to use functional magnetic resonance imaging (fMRI) to assess the somatotopic cortical representation of the hands of workers subjected to occupational vibration. The study included six men with severe vibration exposures who were suffering from hand-arm-vibration syndrome (HAVS) and six controls. The analysis focused on the pattern and degree of activation of contra- and ipsilateral hemispheres of the brain with tactile stimulation and motor activation of the hand. These stimulations resulted in well-defined activation of the contralateral, and to a lesser extent the ipsilateral hemisphere. Statistical analysis of this limited patient material did not indicate any significant somatotopic cortical changes following long-term exposure to vibrating hand-held tools, although there was a tendency to a shift of activation towards the more cranial parts of the cortex in the patient group.

Work-related upper extremity musculoskeletal disorders

Upper extremity musculoskeletal disorders such as DeQuervain's tendonitis, carpal tunnel syndrome, and rotator cuff tendonitis have become increasingly common among working people in the United States. Extensive epidemiological investigation indicates that the adverse ergonomic exposures of force, repetition, vibration and certain postures are risk factors for development of many of these disorders. Assessment of patients with possible work-related upper limb disorders requires eliciting information about the illness, performing an examination about the illness, and obtaining information about adverse ergonomic exposures on and off from work. Treatment can only be successful when exposure to adverse ergonomic risk factors is reduced or eliminated.

Vibration exposure, smoking, and vascular dysfunction

OBJECTIVES

Vibration white finger (VWF), also known as "occupational Raynaud's phenomenon", is marked by arterial hyperresponsiveness and vasoconstriction during cold stimulation. The impact of tobacco use, and by extension stopping smoking, on the long term course of the disease has been inconclusively characterised. The objectives of this study included assessment of the impact of tobacco use on symptoms and on objective tests in shipyard workers exposed to vibration, and in gauging the natural history of the disorder after stopping exposure and changing smoking patterns.

METHODS

In a cross sectional investigation, 601 current and former users of pneumatic tools were evaluated subjectively for cold related vascular symptoms, and tested by cold challenge plethysmography. There was follow up and subsequent testing of 199 members of the severely effected subgroup of smokers and non-smokers, many of whom had stopped smoking in the interval between tests. Effects of smoking and stopping smoking on symptoms and plethsymographic results were assessed.

RESULTS

Symptoms and measured abnormal vascular responses related to cold were more severe in smokers than in non-smokers. Follow up of 199 severely effected members of the cohort, all removed from exposure for 2 years, indicated that smokers were almost twice as likely to have more severe vasospasm (test finger/control finger systolic blood pressure% (FSBP%) <30) than were non-smokers (-32.2% v 17.4%). 53 Subjects who stopped smoking during the interval between tests improved, and were indistinguishable from non-smokers similarly exposed to vibration. Additional physiological benefits of stopping smoking were still apparent at further follow up examination, 1 year later. Improvements evident on plethysmography were not accompanied by improvements in symptoms, which were unaffected by smoking.

CONCLUSIONS

Smoking seems to delay physiological improvement in response to cold challenge in workers with VWF, after the end of exposure to vibration. Symptoms were less likely to improve over time than digital blood pressure, and were less affected by smoking.

Cross sectional study of a workforce exposed to hand-arm vibration: with objective tests and the Stockholm workshop scales

OBJECTIVES

Medical surveillance of workforces exposed to vibration has been recommended with the Stockholm workshop scales. The aims of this study were (a) to evaluate how the results of the objective tests individually and jointly associated with the final Stockholm workshop staging, (b) how this staging related to the history of exposure to vibration, and (c) how different trades were affected by the hazards from vibrating tools.

METHODS

All workers exposed to vibration in a heavy engineering company were examined with a questionnaire and a battery of tests. An assessment of staging by the Stockholm workshop scales was made. Estimates of the daily exposure and lifetime dosage of vibration of the various trades were reached.

RESULTS

The average years of tool use was 23.3 years (range 3-47 years) and the mean lifetime exposure was 11,022 (range 1012-46,125) hours. The individual neurological tests were all strongly associated with the Stockholm neurological staging but the cold provocation test was not associated with the Stockholm vascular staging. Neurological staging was significantly associated with age, years of tool use, and total hours of exposure to vibration, but not with trade or smoking. Vascular staging was significantly associated with age, years of tool use, total hours of exposure to vibration, and trade, but not with smoking. The mean neurological latent period was 19.7 (range 2-40) years and for the vascular component 19.1 (range 2-40) years. These means varied significantly by trade. The overall prevalence of neurological findings of 62% was greater than the overall prevalence of vascular findings, which was 33%.

CONCLUSIONS

(1) The neurological objective tests were found to be of use in neurological staging. The cold provocation test was not associated with the vascular staging and therefore was of little value. (2) Years of tool use was the exposure variable most significantly associated with evidence of damage to neurological component while years of tool use and trade were the variables most associated with vascular damage. (3) The prevalence of neurological symptoms (62%) was greater than the prevalence of vascular symptoms (33%). (4) Dressers and welders have shorter latent periods than platers and fitters.

Raynaud's syndrome in workers who use vibrating pneumatic air knives

PURPOSE

The use of vibrating tools has been shown to cause Raynaud's syndrome (RS) in a variety of workers, including those who use chain saws, chippers, and grinders. The diagnosis of RS in workers who use vibrating tools is difficult to document objectively. We studied a patient cohort with RS caused by the use of a vibrating pneumatic air knife (PAK) for removal of automobile windshields and determined our ability to document RS in these workers by means of digital hypothermic challenge testing (DHCT), a vascular laboratory study that evaluates digital blood pressure response to cooling.

METHODS

Sixteen male autoglass workers (mean age, 36 years) with RS were examined by means of history, physical examination, arm blood pressures, digital photoplethysmography, screening serologic studies for underlying connective tissue disorder, and DHCT.

RESULTS

No patient had RS before they used a PAK. The mean onset of RS (color changes, 100%; pain, 93%; parathesias, 75%) with cold exposure was 3 years (range, 1.5 to 5 years) after initial PAK use (mean estimated PAK use, 2450 hours). Fifty-six percent of workers smoked cigarettes. The findings of the physical examination, arm blood pressures, digital photoplethysmography, and serologic testing were normal in all patients. At 10 degrees C cooling with digital cuff and patient cooling blanket, a significant decrease in digital blood pressure was shown by means of DHCT in 100% of test fingers versus normothermic control fingers (mean decrease, 75%; range, 25% to 100%; normal response, less than 17%; P <.001). The mean follow-up period was 18 months (range, 1 to 47 months). No patient continued to use the PAK, but symptoms of RS were unchanged in 69% and worse in 31%.

CONCLUSION

PAK use is a possible cause of vibration-induced RS. The presence of RS in workers who use the PAK was objectively confirmed by means of DHCT. Cessation of PAK use in the short term did not result in symptomatic improvement.

Neurophysiological findings in vibration-exposed male workers

Fractionated nerve conduction, vibrotactile sense, and temperature thresholds were studied in 73 symptomatic vibration-exposed male workers. Three symptomatic groups were distinguished: patients with isolated sensorineural symptoms; with isolated vasospastic problems; and with both. Clinical carpal tunnel syndrome occurred in 14 patients and abnormal cold intolerance (without blanching of the fingers) in 23. In the group as a whole, nerve conduction studies were abnormal in the median nerve but not in the ulnar nerve and vibration perception and temperature thresholds were impaired. Of the three symptomatic groups, patients with isolated sensorineural symptoms differed from controls. No differences were seen between patients with and without clinical carpal tunnel syndrome. With severe sensorineural symptoms the vibration perception thresholds, but not the values of the nerve conduction studies, were further impaired. The results indicated two injuries that are easily confused: one at receptor level in the fingertips and one in the carpal tunnel. Careful clinical assessment, neurophysiological testing, and examination of vibrotactile sense are required before carpal tunnel release should be considered in these patients.

Hand function in workers with hand-arm vibration syndrome

Hand-arm vibration syndrome has been specially addressed in the Scandinavian countries in recent years, but the syndrome is still not sufficiently recognized in many countries. The object of this preliminary study was to describe the nature and character of vibration-induced impairment in the hands of exposed workers. Twenty symptomatic male workers (aged 28 to 65 years) subjected to vibration by hand-held tools were interviewed about subjective symptoms and activities of daily living and were assessed with a battery of objective tests for sensibility, dexterity, grip function, and grip strength. The test results were compared with normative data. The majority of patients complained of cold intolerance, numbness, pain, sensory impairment, and difficulties in handling manual tools and in handwriting. The various objective tests showed considerable variation in indications of pathologic outcome, revealing differences in sensitivity to detect impaired hand function. Semmes-Weinstein monofilament testing for perception of light touch-deep pressure sensation, the small-object shape identification test, and moving two-point discrimination testing for functional sensibility provided the most indications of pathologic outcomes. The authors conclude that vibration-exposed patients present considerable impairment in hand function.

Symptoms of hand-arm vibration syndrome in gas distribution operatives

OBJECTIVES

To survey the prevalence and severity of hand-arm vibration syndrome symptoms (HAVS), and to estimate past and current exposure to hand held vibrating tools in a sample of gas distribution operatives breaking and re-instating road surfaces.

METHODS

153 gas distribution operatives (participation rate 81%) from three company districts were assessed by an administered questionnaire, a clinical examination, and a simple cold challenge test to the hands. Exposure histories were taken aided by a picture album of past and current tools. Information was obtained from several sources on the likely vibratory characteristics of those tools. Estimates were thus obtained of the frequency of blanching and neurological complaints in operatives, and of their lifetime hours of exposure and lifetime dose of vibration.

RESULTS

On average, the sample had spent 16 years in employment involving use of vibratory tools. 24% had symptoms or signs of blanching after use of tools in the industry; 46% had troublesome persistent complaints of paraesthesiae or numbness, and these symptoms extended into the hands or arms in 18% of workers. In 5.9% the distribution of symptoms was suggestive of carpal tunnel syndrome; and of ulnar nerve entrapment in a further 3.9%. The risks of blanching and neurological complaints rose significantly with lifetime hours of use of vibrating tools and lifetime dose of vibration. Symptoms were generally mild and apparent only after a prolonged interval, but there were exceptions, and cases had occurred after lower recent exposures.

CONCLUSIONS

It has been suggested that aspects of the gas distribution operative's work mitigate against the risk normally anticipated from use of pneumatic road breaking tools. By contrast our data suggest that symptoms of HAVS do occur, given sufficient exposure, a finding relevant not only to gas supply workers, but also to workers from other industries who break and repair road surfaces.

Surveillance case definitions for work related upper limb pain syndromes

OBJECTIVES

To establish consensus case definitions for several common work related upper limb pain syndromes for use in surveillance or studies of the aetiology of these conditions.

METHODS

A group of healthcare professionals from the disciplines interested in the prevention and management of upper limb disorders were recruited for a Delphi exercise. A questionnaire was used to establish case definitions from the participants, followed by a consensus conference involving the core group of 29 people. The draft conclusions were recirculated for review.

RESULTS

Consensus case definitions were agreed for carpal tunnel syndrome, tenosynovitis of the wrist, de Quervain's disease of the wrist, epicondylitis, shoulder capsulitis (frozen shoulder), and shoulder tendonitis. The consensus group also identified a condition defined as "non-specific diffuse forearm pain" although this is essentially a diagnosis made by exclusion. The group did not have enough experience of the thoracic outlet syndrome to make recommendations.

CONCLUSIONS

There was enough consensus between several health professionals from different disciplines to establish case definitions suitable for use in the studies of several work related upper limb pain syndromes. The use of these criteria should allow comparability between studies and centres and facilitate research in this field. The criteria may also be useful in surveillance programmes and as aids to case management.

Cutaneous responses to endothelin-1 and histamine in patients with vibration white finger

Vibration white finger (VWF) is the episodic blanching of the fingers that occurs in response to cold in those who work with hand-held vibrating tools. Clinically the condition differs from primary Raynaud's phenomenon as persistent pain and paresthesia are common in the hands and arms and occur independently of the "white attacks." We have previously reported a decrease in protein gene product 9.5 and calcitonin gene-related peptide-immunoreactive nerve fibers in the digital skin of individuals with VWF. In this study, we have sought to determine whether this deficit of immunoreactive sensory-motor nerves has a functional counterpart in vivo. Histamine produces a rapid wheal and flare response following intradermal injection, whereas endothelin-1 (ET-1) produces a central area of pallor with a surrounding neurogenic flare. In contrast, calcitonin gene-related peptide produces a non-neurogenic erythema. In this study, histamine and ET-1 were injected into the dorsum of the middle phalanx and the local neurovascular response was assessed by measuring the area of the visible flare or pallor. Basal finger blood flow was also measured by laser Doppler flowmetry in each of the digits prior to intradermal injection. The experiments were performed at 21 degrees C and 4 degrees C. Patients with VWF and asymptomatic vibration-exposed workers had significantly lower resting skin blood flow at both 21 degrees C and 4 degrees C than heavy manual workers with no vibration exposure. The size of the histamine- and ET-1-induced flares at both 21 degrees C and 4 degrees C was significantly smaller in patients with VWF when compared with the asymptomatic vibration-exposed workers and heavy manual workers. The size of the ET-1-induced pallor was smaller in patients with VWF when compared with the heavy manual workers at both 21 degrees C and 4 degrees C. In contrast, the area of erythema induced by intradermal injection of calcitonin gene-related peptide at both 21 degrees C and 4 degrees C was of a similar size in patients with VWF and in heavy manual workers. These results indicate that the neuroneal deficit identified by immunohistochemistry in the digital skin of patients with VWF has a functional counterpart in vivo and is evident as a reduced ability to propagate an axon-reflex vasodilator response when challenged with histamine and ET-1. Furthermore, these results enable patients with VWF to be differentiated from both asymptomatic vibration-exposed workers, in whom the histamine- and ET-1-induced flares are normal, and those with primary Raynaud's disease, in whom the ET-1 flare is reduced and the histamine-induced flare is normal.

Clinical applications of quantitative sensory testing (QST)

Quantitative sensory testing (QST) has been used clinically for the last two decades, yielding a substantial number of publications regarding these applications. In this review we tried to amass together the major findings of these publications into one monograph, excluding those dealing with pain. This was done with the aim of assisting clinicians in the better use of QST techniques for the benefit of their patients.

Vibrotactile sense and hand symptoms in blue collar workers in a manufacturing industry

OBJECTIVES

To study whether vibrotactile sense combined with questionnaires (subjective complaints) and a clinical examination (including scoring of the Stockholm workshop scale (sensorineural staging)) could serve as a screening procedure, in the health care service, for sensorineural symptoms. A group of blue collar workers exposed to vibration in a manufacturing industry (rock crushing plants) was used as the study group. Another group of workers not exposed to vibration but subjected to heavy manual work served as the control group.

METHODS

Vibrotactile sense was determined. The index and the little fingers of both hands were investigated. A clinical examination was performed. Questionnaires were used for exposure data and for assessment of symptoms.

RESULTS

Important findings were that impairment in vibrotactile sense correlated with impairment in grip force, cold sensitivity, and other sensorineural symptoms--such as numbness and tendency to drop items. Clinical findings such as Phalen's test and two point discrimination were related only in those workers with the poorest vibrotactile sense. There was a relation between vibrotactile sense and the Stockholm workshop scale (sensorineural staging) for the sensorineural symptoms. Muscle and joint problems were more often seen in workers with decreased vibrotactile sense.

CONCLUSIONS

Tactilometry for assessment of vibrotactile sense is a useful tool in assessing and evaluating the severity of vibration induced neuromuscular symptoms and verifying the patients' clinical complaints. Heavy manual work without exposure to vibration may contribute to impairment of vibrotactile sense. The relation between impairment in vibrotactile sense and grip strength indicates that impaired sensory feedback may contribute to muscle weakness.

Impact vibration and hand-arm vibration syndrome

The case histories of ten workers with Hand-Arm Vibration Syndrome (HAVS) indicate that their predominant vibration exposure was to impact vibration. This association, recognized previously in pedestal grinders and in multiple hand tool users, should now be identified in spot welders and press operators. This will have important implications for compensation claimants as well as prevention development.

Diagnostics of hand-arm system disorders in workers who use vibrating tools

A hand-arm vibration syndrome occurs in some workers who use hand held vibrating tools. It is recognised to consist of white fingers, diffusely distributed finger neuropathy, pain in the arm and hand, and a small excess risk of osteoarthrosis from percussion to the wrist and elbow. Carpal tunnel syndrome is mainly due to ergonomic factors other than vibration, but certain factors related to vibration may contribute to its development. A decrease in muscle power induced by vibration, and excessive hearing deficit have been postulated. The assessment of a disorder suspected of being induced by vibration includes deciding whether there is a disorder and, if so, whether the symptoms can be caused by vibration. To decide whether the symptoms can be caused by vibration epidemiological documentation and pathogenically reasonable theories must exist. A causal diagnosis finally requires and epidemiological decision whether or not the factual exposure has elicited the patient's symptoms. Epidemiological data on the quantitative association between vibration and excessive risks of white fingers and diffusely distributed neuropathy are incomplete. The symptomatic diagnosis of white fingers is still mainly based on anamnestic information. Available laboratory tests are incapable of grading the severity of individual cases. Recording the finger systolic blood pressure during cold provocation is a method of symptomatic diagnosis with reasonable levels of specificity, sensitivity, and predictive value. For diffusely distributed neuropathy these levels are lower than desired. Electrodiagnostic tests for carpal tunnel syndrome have sufficient validity. Proper exposure evaluation must be based on an appreciation of the character of the vibration as well as effective duration and intermittency. If this is not taken into account, the number of hours of exposure and intensity of vibration are likely to be non-commensurable variables, and the simple product of them is a questionable dose measure. Separate models for risk evaluation of vascular and neurological disorders related to work with different tools and processes will have to be established. Ongoing research to obtain further data on exposure-response relations for neurological disturbances begins to yield encouraging results.

Thromboxane metabolite excretion in patients with hand-arm vibration syndrome

As chronic exposure to hand-held vibrating tools may cause endothelial injury, a subsequent sustained platelet activation with the increased release of vasoconstricting thromboxane A2 (TxA2) could be of pathophysiological importance in vibration-induced Raynaud's phenomenon. Therefore, the aim of this study was to elucidate whether or not hand-arm vibration syndrome is accompanied by increased endogenous TxA2 biosynthesis. The study involved 64 men, aged 23-61 years, stratified according to the exposure to vibrating tools, the presence of Raynaud's phenomenon, and smoking habit. Forty of them were car mechanics and 24 were age-matched healthy volunteers who served as controls. The assessment of platelet TxA2 formation in vivo was performed by quantification of the urinary excretion of its major metabolite, 2,3-dinorthromboxane B2 (2,3-dinor-TxB2), employing gas chromatography-mass spectrometry. The average urinary excretion rate of 2,3-dinor-TxB2 in patients with Raynaud's phenomenon was 296 +/- 42 pg/mg creatinine and did not differ significantly from the corresponding values in controls (328 +/- 62 pg/mg creatinine) or individuals exposed to vibrating tools, but without any signs of vasospastic disease (232 +/- 29 pg/mg creatinine). The only statistically significant difference was found between smokers and non-smokers (P < 0.001), a finding confirming the existence of chronic platelet dysfunction in cigarette smokers. The present data indicate that chronic exposure to vibrating tools, with or without Raynaud's phenomenon, is not associated with an enhanced platelet function as monitored by the urinary excretion of 2,3-dinor-TxB2. Hence, a possible vibration-induced vascular injury does not seem to provide a stimulus sufficient to induce a persistent platelet activation.

Hand problems in 100 vibration-exposed symptomatic male workers

Long-term use of hand-held vibrating tools may induce various types of hand problems. One hundred symptomatic men exposed to vibration from such tools were interviewed and examined with special reference to neurosensory and vasospastic problems. Three distinct symptomatic groups were identified: isolated neurosensory symptoms (48%), isolated vasospastic problems (20%), and combined neurosensory and vasospastic problems (32%). Abnormal cold intolerance (pain and coldness without blanching of the fingers on exposure to cold) occurred in 27% of the patients. Neurosensory problems were more predominant than vasospastic ones, especially during the first 20 years of vibration exposure. Of 80 patients with neurosensory symptoms, only 22 had signs of a carpal tunnel syndrome (CTS). It is concluded that vibration-induced neurosensory and vasospastic symptoms can occur separately or together, and that the neurosensory symptoms are often not due to a CTS.

Serum endothelin concentrations in workers exposed to vibration

OBJECTIVES

Endothelin 1 (ET1) is one of a newly discovered family of potent naturally occurring vasoconstrictors produced by the endothelium. A few publications indicated that the peptide may have a role in idiopathic Raynaud's phenomenon and Raynaud's phenomenon secondary to connective tissue disease. The aim of this study was to compare serum endothelin concentrations in people with vibration induced white finger (VWF) with those of controls exposed to vibration, and unexposed (pure) controls.

SUBJECTS AND METHODS

Male volunteers from a stonemasonry, two quarries, and an insurance company were classified by questionnaire and clinical examination into men with VWF (cases, n = 31), exposed controls (n = 22), or pure controls (n = 36). All subjects were asked to provide two venous blood specimens: a baseline sample after a period of warm equilibration (30 minutes seated in a warm room and 20 minutes with both hands immersed in a water bath at 37 degrees C); and again after cold challenge (both hands immersed in a water bath at 6 degrees C for six minutes). Serum concentrations of the 21 amino acid peptide endothelin ET1-21 were measured by radioimmunoassay.

RESULTS

Baseline concentrations of ET1-21 were found to be lower in cases (mean = 12.2 pmol/l) than in the two control groups (mean = 14.7 pmol/l in exposed controls; mean = 14.3 pmol/l in pure controls). Among cases there was a broad inverse relation between severity, as measured by the Griffin blanching score, and baseline ET1-21 (Spearman rank correlation coefficient -0.58, P < 0.001). Cold challenge provoked an overall rise in ET1-21 in all groups, but larger and significant mean absolute and percentage rises were found in cases (4.1 pmol/l and 54%) than in the control groups (2.6 pmol/l and 21% in exposed controls; 1.5 pmol/l and 20% in pure controls). Similar but more obvious differences occurred when controls were compared with those cases who gave a more severe history of disease (Griffin blanching score > or = 24) and those cases found to blanch after cold challenge. In these case subsets baseline ET1-21 was nearly 50% lower than for controls and a four and a half to fivefold greater percentage rise in ET1-21 occurred upon cold challenge. Differences were significant. Close matching for age and smoking did not alter the principal findings. No significant differences, whether in baseline or cold response, were found between unexposed and exposed controls.

CONCLUSIONS

Baseline findings seem to contradict various published series and attempts are made to reconcile the differences. It is suggested that a lower baseline ET1-21 in cases may result from a disease compensation mechanism or damage effect. The large relative rise in serum ET1-21 when cases are cold challenged may contribute directly or indirectly to vasospasm, but a simple mechanism is unlikely and interpretation is limited by the absence of measurements of forearm blood flow.

Change in digital blood flow with simultaneous reduction in plasma endothelin induced by hand-arm vibration

Involvement of endothelium-derived relaxing factor (EDRF) or endothelium-derived constricting factor (EDCF) has been proposed as the pathophysiologic mechanism of vibration-induced white finger (VWF). Recent evidence that endothelin is a potent vasoconstrictor peptide indicates that it may play a role in vasoregulation during vibration exposure through the local actions of EDRF or EDCF. Therefore, we examined the effects of grasping (50 N) and hand-arm vibration (50 m/s2 rms, 120 Hz, x-axis) on digital blood flow (DBF) and on the level of plasma endothelin in seven healthy male office workers. Grasping decreased DBF without affecting endothelin, and vibration increased DBF with a simultaneous reduction in endothelin. The grasping-induced decrease in DBF seemed to be due to mechanical compression of the vessels. The negative correlation between DBF and endothelin during vibration exposure suggests that a reduction in release of endothelin from smooth muscle into the vessel cavity during vibration leads to vasodilatation, possibly attributable to the local axon reflex.

Dose-response relation for vascular disorders induced by vibration in the fingers of forestry workers

OBJECTIVES

To study the relation between the prevalence of vascular disorders (white finger) and vibration exposure in a group of 222 forestry workers, of whom 164 (73.9%) had work experience limited to antivibration (AV) chain saws only and 58 (26.1%) had operated both non-AV and AV chain saws.

METHODS

The chain saw operators and 195 control workers never exposed to hand transmitted vibration were interviewed with health and workplace assessment questionnaires. The diagnosis of vibration induced white finger (VWF) was made on the basis of subjective symptoms of finger blanching and the results of a cold test with plethysmographic measurement of systolic blood pressure of the finger. Vibration was measured on a representative sample of AV and non-AV chain saws. Daily vibration exposure was assessed as eight hour energy equivalent frequency weighted acceleration (A(8)). A lifetime vibration dose was estimated for each of the forestry workers.

RESULTS

The overall prevalence of VWF among the forestry workers was 23.4%. The diagnosis of VWF was made in 13.4% of the forestry workers who handled only AV chain saws and in 51.7% of those who had also operated non-AV chain saws in the past. Raynaud's phenomenon was found in 2.6% of the controls. In the forestry workers, the risk for VWF showed positive increments with each increment of vibration dose, suggesting a monotonic dose-response relation. The responsiveness to cold in the digital arteries of the forestry workers was also found to increase with increasing vibration dose and severity of VWF. The estimated relation between VWF and vibration exposure showed that the expected prevalence of VWF increased almost linearly to either A(8) (with exposure duration unchanged) or the number of years of exposure (with equivalent acceleration unchanged).

CONCLUSIONS

In this study of VWF among forestry workers, the estimated dose-response relation showed that if the magnitude of vibration acceleration is doubled, the total duration of exposure should be halved to produce an equivalent effect. On the basis of the assessment of vibration exposure, the estimated risk for VWF in the study population was found to be lower than that predicted by the international standard ISO 5349. These findings suggest a revision of the risk estimates for VWF currently provided by ISO 5349.

Neuropathy in female dental personnel exposed to high frequency vibrations

OBJECTIVE

To evaluate early neuropathy in dental personnel exposed to high frequency vibrations.

METHODS

30 dentists and 30 dental hygienists who used low and high speed hand pieces and ultrasonic scalers were studied, and 30 dental assistants and 30 medical nurses not exposed to vibration (all women). Vibrotactile sensibility, strength, motor performance, sensorineural symptoms and signs, and vascular symptoms in the hands, as well as mercury concentrations in biological samples and cervicobrachial symptoms, were studied.

RESULTS

The two groups exposed to vibration had significant impairments of vibrotactile sensibility, strength, and motor performance, as well as more frequent sensorineural symptoms. In the dentists there were significant associations between the vibrotactile sensibility and strength, motor performance, superficial sensibility, and sensorineural symptoms. There were no associations between these findings and cervicobrachial symptoms, mercury concentrations, or smoking. There was no increase of vascular symptoms of the hands in the groups exposed to vibration.

CONCLUSION

Dental hygienists and dentists had a slight neuropathy, which may be associated with their exposure to high frequency vibrations, and which may be detrimental to their work performance. Thus, development of safer equipment is urgent.