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Objectives: Segmental sensory nerve conduction velocity (SNCV) was measured from the wrists to the hands and digits in a population of 134 (126 men and 8 women) vibration-exposed shipyard workers following systemic warming using a bicycle ergometer. Results were compared to earlier nerve conduction tests, identical in execution, except that the warming process was segmental and cutaneous. The study was designed to investigate whether SNCVs, which were selectively slow in the fingers after segmental cutaneous (skin surface) warming, would be affected differently by systemic warming., Methods: Wrist-palm, palm-proximal digit, and digital sensory nerve segments were assessed antidromically by stimulating at the wrist with recording electrodes placed distally. The same subjects were cutaneously warmed in 2001 to >or=31 degrees C and were systemically warmed 28 months later in 2004 by ramped sustained exercise to 100 W for 12 min. Skin temperatures were measured by traditional thermistry and by infrared thermal images taken over the hand and wrist surfaces., Results: When systemic warming was compared to segmental cutaneous warming, SNCVs were increased by 15.1% in the third digit and 20.4% in the fifth digit of the dominant hand. Respective increases in the non-dominant hand were 11.0% and 19.4%. A strong association between increased surface skin temperature and faster SNCV, which had been observed after segmental cutaneous warming, was largely eliminated for both digit and palmar anatomic segments after systemic warming. Significant differences in SNCV between vibration-exposed and non-exposed workers, which had been observed after segmental cutaneous warming, were eliminated after systemic warming. Systemic warming had only a small effect on the wrist-palm (transcarpal) segmental SNCVs., Conclusions: Reduced SNCV in the digits was observed in vibration-exposed and non-exposed workers. Substituting exercise-induced systemic warming for segmental cutaneous warming significantly increased SNCV in the digits and appeared to reduce differences in SNCV between vibration-exposed and non-exposed workers. These findings persisted despite a substantial time interval between tests, during which the subjects continued to work. There may be more general implications for diagnosing clinical conditions in industrial workers, such as the carpal tunnel syndrome and the hand-arm vibration syndrome.

Objectives: The purpose of this paper is to assess the overlap and stability of two different case definitions of carpal tunnel syndrome CTS. The analysis considers the association between different case definitions and objective tests (sensory nerve conduction velocities, SNCVs and vibrotactile perception thresholds, TTS), and the natural history of CTS, in the context of two vibration-exposed cohorts., Methods: Clinical CTS cases were defined in two ways: (1) by the study physician using fixed criteria, and; (2) by questionnaire and hand diagram. SNCV in median and ulnar nerves was measured for digital, transpalmar, and transcarpal segments, and conventionally as from wrist-digit. Skin temperature was assessed as a point measurement by thermistor and regionally by thermal imaging. VTTs were determined at the bilateral fingertips of the third and fifth digits using a tactometer meeting the requirements of ISO 13091-1 (ISO 2001). The subjects were cohorts of shipyard workers in 2001 and 2004, and dental hygienists in 2002 and 2004., Results: Results are reported for 214 shipyard workers in 2001 and 135 in 2004, and for 94 dental hygienists in 2002 and 66 in 2004. In 2001, 50% of shipyard workers were diagnosed as CTS cases by at least one of the diagnostic schemes, but only 20% were positive by both criteria. Among study physician diagnosed cases, 64% were CTS negative in 2001, 76% were negative in 2004, 13% were positive in both years, 22% became negative after being positive, and 11% became positive after being negative. For only study physician diagnosed CTS did VTTs differ between cases differ and non-cases in digit 3; there was no such distinction in digit 5. The dental hygienists had little CTS., Conclusion: Clinical case definitions of CTS based on diagrams and self-assessment, and clinical evaluation have limited overlap. Combining clinical criteria to create a more narrow or specific case definition of CTS does not appear to predict SNCV. The natural history of CTS suggests a protean disorder with considerable flux in case status over time.

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.

Upper extremity musculoskeletal disorders (UEMSDs) comprise a large proportion of work-related illnesses in the USA. Physical risk factors including manual force and segmental vibration have been associated with UEMSDs. Reduced sensitivity to vibration in the fingertips (a function of nerve integrity) has been found in those exposed to segmental vibration, to hand force, and in office workers. The objective of this study was to determine whether an association exists between digital vibration thresholds (VTs) and exposure to ergonomic stressors in automobile manufacturing. Interviews and physical examinations were conducted in a cross-sectional survey of workers (n = 1174). In multivariable robust regression modelling, associations with workers' estimates of ergonomic stressors stratified on tool use were determined. VTs were separately associated with hand force, vibration as felt through the floor (whole body vibration), and with an index of multiple exposures in both tool users and non-tool users. Additional associations with contact stress and awkward upper extremity postures were found in tool users. Segmental vibration was not associated with VTs. Further epidemiologic and laboratory studies are needed to confirm the associations found. The association with self-reported whole body vibration exposure suggests a possible sympathetic nervous system effect, which remains to be explored.

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., (Copyright 2004 Wiley-Liss, Inc.)

Objectives: Segmental sensory nerve conduction velocity (SNCV) was measured from the wrists to the hands and digits of a population of vibration-exposed shipyard workers. This study was designed to investigate whether SNCV was selectively slowed in the fingers and whether a laboratory approach could be adapted for robust field use., Methods: Wrist-palm, palm-proximal digit, and digital segments were determined from stimulation at the wrist with recording electrodes placed distally and adjusted to individual anatomy. The cohort was selected on the basis of current use of vibratory tools., Results: Wrist-palm and digital segments were slower than palm-proximal digit segments for dominant and non-dominant hands and for both ulnar and median nerves. In the dominant-hand median nerve of participants with current exposure, the SNCV was 41.4 m/s (SD 8.0) for the wrist-palm segment, 50.8 (SD 9.5) for the palm segment, and 42.1 m/s (SD 9.3) for the digital segment. Temperature had an important effect on nerve conduction velocity but not equally across segments. Other explanatory variables had modest effect on SNCV., Conclusions: Reduced SNCV in the digits may be a consequence of industrial exposure to vibration. Each sensory nerve segment appeared to have a different characteristic velocity and different pattern of association with skin temperature. There are differences between median and ulnar nerve segments, with potentially important consequences when standard distances are used to assess wrist-digit velocity.

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.

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.

The hand-arm-vibration syndrome (HAVS) is a complex entity composed of circulatory, sensory, and motor disturbances, as well as associated musculoskeletal components. This study was performed to find a diagnostic testing modality with sufficient sensitivity, specificity, and predictive value to be utilized as a screening test for this disorder in a working population. A full range of testing modalities was utilized in the shipyard medical department. In addition, a clinical diagnosis of vascular and sensorineural disease was established in the workers by a combination of plethysmography, vibrometry, two point discrimination, and monofilament testing in an independent occupational medicine clinic. No one test modality met the requirements for such a definitive diagnostic test. Rather, a range of modalities was required to reach any acceptable level of predictive value, with sufficient degrees of specificity and sensitivity.

Five patients developed symptoms of Raynaud's phenomenon and upper extremity paresthesias after 7-32 months of exposure to air-powered surgical instruments used for the harvest of bone for bone banks. Results of cold challenge plethysmography, nerve conduction studies, vibrotactile thresholds, and quantitative sensory testing were as follows: all patients had significant reproducible vasospasm with nondetectable finger systolic blood pressure (FSBP = 0) after local digital cooling; nerve conduction abnormalities included delayed median nerve sensory conduction (< 48 m/s) across 5 of 10 wrists; and no ulnar nerve abnormalities were detected. Vibrotactile thresholds were only modestly elevated, an unexpected outcome given the frequently recognized association between vibrotactile tests and nerve conduction studies. These abnormalities occurred with exposures to frequencies previously thought to be too high to be harmful to medical personnel.

The hand-arm vibration syndrome, widely known as vibration white finger, is a disorder of nerves and blood vessels that occurs in workers exposed to segmental vibration. A cross sectional symptom survey was performed on a sample of workers employed by a large shipyard in the north eastern United States. Random samples were drawn from departments composed of full time dedicated pneumatic grinders, workers with part time exposure to vibration, and other workers not exposed to vibratory tools. Of the 375 workers sampled, 79% responded. The prevalence of white finger symptoms was 71%, 33%, and 6% among the three exposure groups respectively. Similarly, the prevalence of numbness and tingling in the hands and fingers in the three exposure groups was 84%, 50%, and 17%. Workers were classified according to the Stockholm Workshop staging systems for vascular and sensorineural symptom severity. Exposure-response analyses of both vascular and sensorineural stage showed monotonically increasing prevalence of higher disease stages with increasing duration of exposure. Logistic regression analysis, performed to control for potential confounding factors including age and current smoking state, produced highly significant (p less than 0.001) associations between cumulative duration of exposure and prevalence of symptoms. In these analyses smoking state was significantly related to vascular and sensorineural symptoms and age was not. Average latency to onset of symptoms was less than five years of full time equivalent work with vibratory tools. Logistic regression analyses were performed to assess the effect of use of particular work practices on reported symptoms. Further study of this workforce with objective, quantitative measures of peripheral neurological and vascular function is required to characterise the clinical and subclinical effects of vibration exposure.

Forty eight patients with extensive occupational exposure to pneumatic grinding tools were evaluated at a university sponsored occupational health clinic. All patients were interviewed and examined by a physician and assessed neurologically with standard clinical, functional motor, quantitative vibrotactile, and electrodiagnostic tests. Sensorineural symptoms were nearly universal; 47 patients (98%) reported numbness and tingling of the hands and fingers. Among clinical tests, two point discrimination and 30 Hz vibration perception were most frequently abnormal. In order to evaluate associations between quantitative test results and sensorineural symptoms, patients were stratified into two groups of symptom severity according to a consensus sensorineural staging system. The tests that discriminated best between the groups of more and less symptomatic patients were hand strength dynamometry, and vibrotactile thresholds. Age standardised 120 Hz vibrotactile thresholds were significantly raised in digit II in 41% of hand measurements. Nerve conduction studies were neither significantly different between more and less symptomatic groups nor correlated with clinical and quantitative sensory tests. Twenty five per cent of the patients had slowing of sensory conduction velocities in the median nerve at the wrist (less than 48 m/s). Of this subset of patients only two showed abnormal slowing of the median nerve distal to the wrist, but half also showed ulnar nerve slowing (less than 47 m/s). This observation highlights the difficulty of differentiating median nerve entrapment from diffuse distal neuropathy in workers exposed to vibration and points to the need for concomitant quantitative sensory and functional motor assessment.

Vibration delivered to the hand and arm by industrial pneumatic tools is a common cause of vascular and neurovascular problems, including cold-induced vascular spasm (vibration white finger) and peripheral neuropathies with paresthesias, dysesthesias, and sensory abnormalities. A decade ago, the US Public Health Service estimated that 1.2 million American workers were at risk. Differentiation of primary and secondary Raynaud's phenomenon from the thoracic outlet syndrome and from the carpal tunnel syndrome pose potential diagnostic difficulties. Despite growing public recognition of upper extremity problems caused by repetitive trauma, there have been few investigations of vibration-induced disorders in the United States. This is not true worldwide, particularly in Northern Europe, where there has been significant intervention in medical surveillance and tool design. There does appear to be, however, frequent misdiagnosis and misdirected surgery. This has particular significance for the clinician, since in the 1990s, cumulative trauma injuries are expected to exceed all other work-related injuries.