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Background: Thermotactile thresholds and vibrotactile thresholds are measured to assist the diagnosis of the sensorineural component of the hand-arm vibration syndrome (HAVS). Objectives: This study investigates whether thermotactile and vibrotactile thresholds distinguish between fingers with and without numbness and tingling. Methods: In 60 males reporting symptoms of the hand-arm vibration syndrome, thermotactile thresholds for detecting hot and cold temperatures and vibrotactile thresholds at 31.5 and 125 Hz were measured on the index and little fingers of both hands. Results: In fingers reported to suffer numbness or tingling, hot thresholds increased, cold thresholds decreased, and vibrotactile thresholds at both 31.5 and 125 Hz increased. With sensorineural symptoms on all three phalanges (i.e. numbness or tingling scores of 6), both thermotactile thresholds and both vibrotactile thresholds had sensitivities greater than 80% and specificities around 90%, with areas under the receiver operating characteristic curves around 0.9. There were correlations between all four thresholds, but cold thresholds had greater sensitivity and greater specificity on fingers with numbness or tingling on only the distal phalanx (i.e. numbness or tingling scores of 1) suggesting cold thresholds provide better indications of early sensorineural disorder. Conclusions: Thermotactile thresholds and vibrotactile thresholds can provide useful indications of sensorineural function in patients reporting symptoms of the sensorineural component of HAVS. [ABSTRACT FROM AUTHOR]

Purpose: This study investigates the effects of room temperature on two standard tests used to assist the diagnosis of vibration-induced white finger (VWF): finger rewarming times and finger systolic blood pressures. Methods: Twelve healthy males and twelve healthy females participated in four sessions to obtain either finger skin temperatures (FSTs) during cooling and rewarming of the hand or finger systolic blood pressures (FSBPs) after local cooling of the fingers to 15 and 10 °C. The measures were obtained with the room temperature at either 20 or 28 °C. Results: There were lower baseline finger skin temperatures, longer finger rewarming times, and lower finger systolic blood pressures with the room temperature at 20 than 28 °C. However, percentage reductions in FSBP at 15 and 10 °C relative to 30 °C (i.e. %FSBP) did not differ between the two room temperatures. Females had lower baseline FSTs, longer rewarming times, and lower FSBPs than males, but %FSBPs were similar in males and females. Conclusions: Finger rewarming times after cold provocation are heavily influenced by room temperature and gender. For evaluating peripheral circulatory function using finger rewarming times, the room temperature must be strictly controlled, and a different diagnostic criterion is required for females. The calculation of percentage changes in finger systolic blood pressure at 15 and 10 °C relative to 30 °C reduces effects of both room temperature and gender, and the test may be used in conditions where the ±1 °C tolerance on room temperature required by the current standard cannot be achieved. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated whether the reductions in finger blood flow induced by 125-Hz vibration applied to different locations on the hand depend on thresholds for perceiving vibration at these locations. Methods: Subjects attended three sessions during which vibration was applied to the right index finger, the right thenar eminence, or the left thenar eminence. Absolute thresholds for perceiving vibration at these locations were determined. Finger blood flow in the middle finger of both hands was then measured at 30-s intervals during five successive 5-min periods: (i) pre-exposure, (ii) pre-exposure with 2-N force, (iii) 2-N force with vibration, (iv) post-exposure with 2-N force, (v) recovery. During period (iii), vibration was applied at 15 dB above the absolute threshold for perceiving vibration at the right thenar eminence. Results: Vibration at all three locations reduced finger blood flow on the exposed and unexposed hand, with greater reductions when vibrating the finger. Vibration-induced vasoconstriction was greatest for individuals with low thresholds and locations of excitation with low thresholds. Conclusions: Differences in vasoconstriction between subjects and between locations are consistent with the Pacinian channel mediating both absolute thresholds and vibration-induced vasoconstriction. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated how the vasoconstriction induced by vibration depends on the frequency of vibration when the vibration magnitude is defined by individual thresholds for perceiving vibration [i.e. sensation levels (SL)]. Methods: Fourteen healthy subjects attended the laboratory on seven occasions: for six vibration frequencies (8, 16, 31.5, 63, 125, or 250 Hz) and a static control condition. Finger blood flow (FBF) was measured in the middle fingers of both hands at 30-second intervals during five successive periods: (i) no force or vibration, (ii) 2-N force, no vibration, (iii) 2-N force, vibration, (iv) 2-N force, no vibration, (v) no force or vibration. During period (iii), vibration was applied to the right thenar eminence via a 6-mm diameter probe during ten successive 3-min periods as the vibration magnitude increased in ten steps (−10 to +40 dB SL). Results: With vibration at 63, 125, and 250 Hz, there was vasoconstriction on both hands when the vibration magnitude reached 10 dB SL. With vibration at 8, 16, and 31.5 Hz, there was no significant vasoconstriction until the vibration reached 25 dB SL. At all frequencies, there was greater vasoconstriction with greater magnitudes of vibration. Conclusions: It is concluded that at the higher frequencies (63, 125, and 250 Hz), the Pacinian channel mediates vibrotactile sensations near threshold and vasoconstriction occurs when vibration is perceptible. At lower frequencies (8, 16, and 31.5 Hz), the Pacinian channel does not mediate sensations near threshold and vasoconstriction commences at greater magnitudes when the Pacinian channel is activated. [ABSTRACT FROM AUTHOR]

To investigate whether the Pacinian channel is involved in vibration-induced reductions of finger blood flow (FBF), vibrotactile thresholds and vasoconstriction have been studied with 125-Hz vibration and two contact areas: 3- or 6-mm-diameter vibrating probes with 2-mm gaps to fixed surrounds. Fifteen subjects provided thresholds for perceiving vibration at the thenar eminence of the right hand with both contact areas. With both contact areas, FBF was then measured in the middle fingers of both hands during five successive 5-min periods: (i) no force and no vibration, (ii) force and no vibration, (iii) force with vibration 15 dB above threshold, (iv) force and no vibration, and (v) no force and no vibration. Thresholds were in the ranges of 0.16-0.66 ms r.m.s. (6-mm probe) and 0.32-1.62 ms r.m.s. (3-mm probe). With the magnitude of vibration 15 dB above each individual's threshold with the 3-mm probe, the median reduction in FBF with the 6-mm probe (to 70 and 77 % of pre-exposure FBF on the exposed right hand and the unexposed left hand, respectively) was greater than with the 3-mm probe (79 and 85 %). There were similar reductions in FBF when vibration was presented by the two contactors at the same sensation level (i.e. 15 dB above threshold with each probe). The findings are consistent with reductions in FBF arising from excitation of the Pacinian channel: increasing the area excited by vibration increases Pacinian activation and provokes stronger perception of vibration and greater vasoconstriction. [ABSTRACT FROM AUTHOR]

Purpose: To investigate how temperature influences changes in finger circulation induced by hand-transmitted vibration in healthy subjects, and the variability in individual response to both vibration and temperature. Methods: With two room temperatures (20 and 28°C), finger blood flow (FBF) and finger skin temperature (FST) were measured on the left middle fingers of 12 subjects at 1-min intervals during three successive 10-min periods. A 5-N static force was applied throughout the 30-min period, and sinusoidal 125-Hz vibration at 44 ms rms. (unweighted) was applied to the right hand during the second of the three 10-min periods. Results: Before exposure to vibration, both FBF and FST were greater with the higher room temperature. Finger blood flow in the left hand reduced during vibration of the right hand. The reduction in absolute FBF differed between the two room temperatures, but the percentage reduction in FBF relative to FBF before exposure to vibration was similar. After cessation of vibration, there was continued reduction in FBF with both room temperatures. Before and after vibration exposure, the FST was correlated with FBF and the FBF and FST at 20°C were correlated with the FBF and FST at 28°C. Conclusions: Vibration of one hand can reduce finger blood flow and skin temperature on the unexposed hand, with the reduction dependent on temperature. The absolute reduction in FBF was greater with the higher room temperature, but the percentage reduction in FBF relative to FBF before vibration exposure was similar. Those with greater finger blood flow before vibration tend to have greater blood flow during vibration, and those with greater finger blood flow with one temperature tend to have greater blood flow with another temperature. [ABSTRACT FROM AUTHOR]

Abstract: Vehicle drivers receive tactile feedback from steering-wheel vibration that depends on the frequency and magnitude of the vibration. From an experiment with 12 subjects, equivalent comfort contours were determined for vertical vibration of the hands at two positions with three grip forces. The perceived intensity of the vibration was determined using the method of magnitude estimation over a range of frequencies (4–250Hz) and magnitudes (0.1–1.58ms−2 r.m.s.). Absolute thresholds for vibration perception were also determined for the two hand positions over the same frequency range. The shapes of the comfort contours were strongly dependent on vibration magnitude and also influenced by grip force, indicating that the appropriate frequency weighting depends on vibration magnitude and grip force. There was only a small effect of hand position. The findings are explained by characteristics of the Pacinian and non-Pacinian tactile channels in the glabrous skin of the hand. [Copyright &y& Elsevier]

If the negligence of an employer results in the disability in an employee, the employer is responsible, in whole or in part, for the disability. The employer is wholly responsible when the worker would not have developed the disability if the employer had taken all reasonable preventative measures. The employer is only partly responsible if the worker would probably have developed some disability even if the employer had taken all reasonable precautions. The employer’s responsibility may be estimated from the difference between the actual disability of the worker and the disability that the worker would have suffered if the employer had taken all reasonable preventative measures. This paper considers alternative ways of apportioning negligent and non-negligent exposures to hand-transmitted vibration. The equivalent daily vibration exposure, A(8), used in current EU Directives is shown to be unsuitable for distinguishing between the consequences of negligent and non-negligent exposures because the risks of developing a disorder from hand-transmitted vibration also depend on the years of exposure. Furthermore, daily exposures take no account of individual susceptibility or the practicality of reducing exposure. The consequences of employer negligence may be estimated from the delay in the onset and progression of disorder that would have been achieved if the employer had acted reasonably, such as by reducing vibration magnitude and exposure duration to the minimum that was reasonably achievable in the circumstances. This seems to be fair and reasonable for both employers and employees and indicates the consequences of negligence—the period of the worker’s life with disease as a result of negligence and the period for which their employment opportunities may be restricted as a result of the onset of the disorder due to negligence. The effects of negligence may be estimated from the delay in the onset of disease or disability that would have occurred if the employer had behaved reasonably. This definition of negligence encourages employers to reduce risks to the lowest reasonably practical level, consistent with EU Directives. [ABSTRACT FROM AUTHOR]

Regular exposure to hand-transmitted vibration can result in symptoms and signs of peripheral vascular, neurological and other disorders collectively known as the hand-arm vibration syndrome. The measurement of the effects of hand-transmitted vibration involves converting the evidence of disorder (symptoms and signs) into information that can be stored. Evaluation requires the use of scales on which to indicate the severity of the various symptoms and signs. Assessment involves a judgement of severity relative to a criterion, usually for a specific purpose (e.g. to decide on removal from work or compensation). The measurement and evaluation of symptoms and signs is necessary when monitoring patient health and when performing epidemiological studies for research. The assessment of the severity of the hand-arm vibration syndrome is currently performed with staging systems, but the criteria are not clear and not related to defined methods for measuring or evaluating the symptoms and signs. Recognizing that similar symptoms can occur without injury from occupational exposures to hand-transmitted vibration, this paper attempts to define significant peripheral neurological symptoms caused by hand-transmitted vibration (i.e. ‘unusual symptoms’) and how these symptoms and related signs may be measured. Scales for evaluating the symptoms (e.g. their extent) and the related signs (e.g. their probability relative to the probability of the sign being present in persons not exposed to vibration) are defined. A method of relating unusual symptoms to both the signs of disorder and the pattern of vibration exposure is illustrated. Assessments of severity will vary according to the reasons for assessing the health effects of vibration, and will depend on local practice and convenience, but a way of combining evaluations of symptoms and signs is demonstrated in a staging system. Although inherently complex, the methods may assist the collection of data required to improve understanding of the effects of hand-transmitted vibration and also support a more complete reporting of the condition in those adversely affected by hand-transmitted vibration. [ABSTRACT FROM AUTHOR]

The detection of vibration applied to the glabrous skin of the hand varies with contact conditions. Three experiments have been conducted to relate variations in the perception of hand-transmitted vibration to previously reported properties of tactile channels. The effects of a surround around the area of contact, the size of the area of contact, the location of the area of contact, the contact force, and the hand posture on perception of thresholds were determined for 8–500?Hz vibration. Removal of a surround around a contact area on the fingertip elevated thresholds of the NP II channel (FA I fibres) at frequencies less than 31.5?Hz and reduced thresholds of the Pacinian channel (FA II fibres) at frequencies greater than about 63?Hz. When no surround was present, thresholds reduced systematically as the contact area increased from the fingertip to the whole hand at frequencies from 16 to 125?Hz, although the decrease was not inversely proportional to the increase in contact area. The results are partly explained by spatial summation in the Pacinian channel (FA II fibres) and the involvement of the NP II channel (SA II) with some influence of biodynamic responses and contact pressures. There were regional differences in sensitivity over the hand within the NP I channel but not within the Pacinian channel: the NP I thresholds (less than 31.5?Hz) decreased from proximal to distal regions of the hand, whereas the Pacinian thresholds (125?Hz) were independent of contact location over the hand. [ABSTRACT FROM AUTHOR]

This study was designed to identify psychophysical channels responsible for the detection of hand-transmitted vibration. Perception thresholds for vibration (16, 31.5, 63 and 125?Hz sinusoidal for 600?ms) at the distal phalanx of the middle finger and the whole hand were determined with and without simultaneous masking stimuli (1/3 octave bandwidth Gaussian random vibration centered on either 16?Hz or 125?Hz for 3000?ms, varying in magnitude 0 to 30?dB above threshold). At all frequencies from 16 to 125?Hz, absolute thresholds for the hand were significantly lower than those for the finger. Changes in threshold as a function of masker level were used to estimate the thresholds of three psychophysical channels (i.e. P, NP I, and NP II channels). Increased vibrotactile sensitivity of the hand compared to the finger seems to be not entirely due to increased spatial summation via the Pacinian system (P channel); non-Pacinian system (NP I and NP II channels) also contributed to perception. Differing transmission of vibration between the hand and the finger may have also influenced the thresholds. [ABSTRACT FROM AUTHOR]

Objectives: This study investigated the effect of hand elevation on reductions in finger blood flow (FBF) induced by hand-transmitted vibration. Methods: Fourteen males attended six sessions on six separate days, with a control sessions and a vibration session (125-Hz vibration at 44 ms rms) with the right hand supported at each of three elevations: 20 cm below heart level (HL), at HL, and 20 cm above HL. Finger blood flow on the left and right hand was measured every 30 s during each 25-min session comprised of five periods: (1) no force and no vibration (5 min), (2) 2-N force and no vibration (5 min), (3) 2-N force and vibration (5 min), (4) 2-N force and no vibration (5 min), and (5) no force and no vibration (5 min). Results: Without vibration, FBF decreased with increasing elevation of the hand. During vibration of the right hand, FBF reduced on both hands. With elevation of the right hand, the percentage reduction in FBF due to vibration (relative to FBF on the same finger at the same elevation before exposure to vibration) was similar on the middle and little fingers of both hands. After cessation of vibration, there was delayed return of FBF with all three hand heights. Conclusions: Vibration of one hand reduces FBF on both exposed and unexposed hands, with the reduction dependent on the elevation of the hand. The mechanisms responsible for vibration-induced reductions in FBF seem to reduce blood flow as a percentage of the blood flow without vibration. Tasks requiring the elevation of the hands will be associated with lower FBF, and the FBF will be reduced further if there is exposure to hand-transmitted vibration. [ABSTRACT FROM AUTHOR]

Objectives: This study investigated whether reductions in finger blood flow (FBF) during and after vibration are similarly dependent on the magnitude and duration of the vibration. Methods: FBF on the left and right hand was measured every minute during, and for 1 h following, exposure of the right hand to one of three magnitudes of 125-Hz sinusoidal vibration (0, 22, or 88 ms rms) for one of two durations (7.5 or 15 min). Each of five experimental sessions was comprised of five periods: (i) no force and no vibration (5 min), (ii) 2-N force and no vibration (5 min), (iii) 2-N force and vibration (7.5 or 15 min), (iv) 2-N force and no vibration (5 min), and (v) no force and no vibration (60 min). Results: Vibration reduced FBF in the exposed and unexposed hands, both during and after vibration. With increased magnitude of vibration, there was increased vasoconstriction in all fingers during and after exposure, and longer recovery times after vibration exposure. With increased duration of vibration, there were no changes in vascular responses during exposure but increased vasoconstriction after exposure and prolonged recovery times. With the greater vibration magnitude, the reduction in FBF during exposure was correlated with the time taken to recover after exposure. Conclusions: Subjects with greater reduction in blood flow during vibration exposure also have stronger and longer vasoconstriction during subsequent recovery. The correlation between vascular changes during and after vibration exposure suggests similar mechanisms control FBF during and after vibration exposure. [ABSTRACT FROM AUTHOR]

Objectives: Finger blood flow is reduced by hand-transmitted vibration but there has been little study of the peripheral vascular response to repetitive mechanical shocks. This study investigated how reductions in finger blood flow depend on shock repetition rate and the peak and rms magnitude of acceleration. Methods: Subjects attended seven sessions: six with repetitive mechanical shocks and a control session with no shocks. Each session comprised five successive 5-min periods: (1) no force and no vibration, (2) force and no vibration, (3) force and vibration, (4) force and no vibration and (5) no force and no vibration. During the second-fourth periods, the palm of the right hand applied 2-N force to a vibrator. During the third period, a 125-Hz mechanical shock was applied with one of four repetition rates (1.3, 5.3, 21 or 83.3/s) and one of three acceleration magnitudes (2.5, 5 or 10 ms rms, unweighted). Finger blood flow was measured every 30 s in the middle and little fingers of the right (exposed) hand and the left (unexposed) hand. Results: Different repetition rates (1.3-83.3 s) and different peak magnitudes (10-88 ms peak) but the same rms acceleration (10 ms rms) caused similar decreases in blood flow in fingers on exposed and unexposed hands. Shocks with a 83.3 s repetition rate, peak magnitude of 10 ms and rms acceleration of 10 ms provoked greater reduction in finger blood flow than shocks with the same peak magnitude but lower repetition rate (21 or 5.3 s) and lower rms acceleration (5 or 2.5 ms). Conclusions: For shocks similar to those based on 125-Hz oscillations with repetition rates between 1.3 and 83.3 s, acute reductions in finger blood flow can be predicted from the rms acceleration. [ABSTRACT FROM AUTHOR]