Characterization of Frequency-Dependent Responses of the Vascular System to Repetitive Vibration

Abstract

Objective-Occupational exposure to hand-transmitted vibration can result in damage to nerves and sensory loss. The goal of this study was to assess the frequency-dependent effects of repeated bouts of vibration on sensory nerve function and associated changes in nerves.Methods-The tails of rats were exposed to vibration at 62.5, 125, or 250 Hz (constant acceleration of 49m/s 2 ) for 10 days. The effects on sensory nerve function, nerve morphology, and transcript expression in ventral tail nerves were measured.Results-Vibration at all frequencies had effects on nerve function and physiology. However, the effects tended to be more prominent with exposure at 250 Hz.Conclusion-Exposure to vibration has detrimental effects on sensory nerve function and physiology. However, many of these changes are more prominent at 250-Hz exposure than at lower frequencies.Hand-arm vibration syndrome (HAVS) is caused by repeated exposure to vibration through the use of powered and pneumatic hand tools. 1 The hallmark symptom of HAVS is coldinduced vasospasms that result in finger blanching. However, sensorineural deficits in the fingers and hands are also prevalent in workers with HAVS. 2 These deficits include reductions in tactile and heat sensitivity and a loss of manual dexterity. In addition, workers with HAVS also develop hand and finger pain, particularly when exposed to cold. 3 Biopsy samples collected from the fingers of workers diagnosed with HAVS have demonstrated that these changes in sensorineural function are associated with a loss of peripheral nerves, nerve fibrosis, and demyelination. 4,5 Even though the morphologic and functional changes associated with sensory loss in workers with HAVS have been characterized, the mechanisms by which vibration causes these changes are still not well understood.One factor that is believed to affect the risk of injury is the vibration frequency or frequencies to which a worker is exposed. Currently, the International Standards Address correspondence to: Kristine Krajnak, PhD, NIOSH, 1095. None of the authors have any conflicts of interest with regards to this research. HHS Public Access Author Manuscript Author ManuscriptAuthor Manuscript Author ManuscriptOrganization (ISO) standard ISO 5349-1 6 presents a weighting curve that predicts the risk of developing a vibration-induced injury. One of the factors used to calculate the weighting factor is the dominant frequency to which a worker is exposed. This weighting curve assigns significantly greater weighting to low-frequency vibration (ie, ≤16 Hz), and the weighting dramatically decreases with exposures greater than 100 Hz. However, experimental and epidemiologic studies suggest that vibration-induced injuries to the fingers and hands may actually be more prevalent in workers using tools that emit a higher-frequency vibration. [7][8][9] It has been hypothesized that the increased risk of injury associated with exposure to higher frequencies may be because stress and strain to the soft tissues of the fingers and hands is grea...

The association between vibration and vascular injury in rheumatic diseases: A review of the literature

“…Longer exposure to vibration may induce endothelial damage and dysregulation, vascular remodeling, disturb smooth muscle response, and may also contribute to digital vasospasms and tissue damage [9,27,35]. In addition, vibrationinduced vascular injury could also result in inflammation, which is also capable of remodeling [35,84]. Understanding of the association between vibration and rheumatic diseases, still need lots of efforts.…”

“…Acute vibration exposure may increase plasma levels of von Willebrand factor, oxidant activity and sensitivity to a2C-adrenoreceptor-mediated vasoconstriction [35]. Longer exposure to vibration may induce endothelial damage and dysregulation, vascular remodeling, disturb smooth muscle response, and may also contribute to digital vasospasms and tissue damage [9,27,35].…”

“…Longer exposures to vibration could produce an increase in oxidative activity, an increased sensitivity to a2C-adrenoreceptor-mediated vasoconstriction and a reduction in endothelial-mediated vasodilation [33]. These changes in responsiveness to vasomodulating factors could result in vascular remodeling [34,35]. This activation is augmented by cold exposure [36].…”

Effect of higher frequency components and duration of vibration on bone tissue alterations in the rat-tail model

“…In addition, most of the tools, such as grinders and chipping hammers, used in industrial workplace generate significant vibration components in the frequency range 100–400 Hz12 ) . However, the current ISO standard 5349-1 and ANSI-standard 2.70 have given greater weight to lower frequencies (<32.5 Hz) and less weight to higher frequencies (>100 Hz)13 ) . The validity of this weighting has been questioned by researchers13,14,15,16,17 ) who suspect a greater risk of vibration-injury in the case of frequency components higher than the 100 Hz.…”

“…However, the current ISO standard 5349-1 and ANSI-standard 2.70 have given greater weight to lower frequencies (<32.5 Hz) and less weight to higher frequencies (>100 Hz)13 ) . The validity of this weighting has been questioned by researchers13,14,15,16,17 ) who suspect a greater risk of vibration-injury in the case of frequency components higher than the 100 Hz. This ISO guideline, with its higher weightage to lower frequency range, might lead to an under estimation of the risk of high frequency components.…”