CPD: Helping hand – managing work-related hand-arm vibration syndrome

It is estimated more than two million workers in the UK are exposed to high levels of vibration as a result of their work tasks, potentially putting them at risk of hand-arm vibration syndrome (HAVS). Risk managing this condition, as well as managing and understanding the mental and physical implications when it does present, can be challenging, as Annie Khan and Anne Harriss explain.

Work related hand-arm vibration syndrome (HAVS) is a health disorder associated with the use of vibrating tools and machinery (Taylor et al, 1994). It is imperative that clinicians understand the disability associated with it (House et al, 2008). HAVS may be encountered in a number of workplaces; employees at particular risk include arboriculture, construction and vehicle repair workshops Poole et al, (2015).

The Health and Safety Laboratory (2018) suggests that more than two million workers in the UK are still exposed to high levels of vibration as a result of their work tasks. The good news is that from information available on the Health and Safety Executive (HSE) website there is a general reduction in claims for conditions associated with the use of vibrating tools – vibration white finger and carpal tunnel syndrome (http://www.hse.gov.uk/Statistics/causdis/vibration/index.htm).

Hand-arm vibration, also known as hand transmitted vibration (HTV), is defined by Harada and Mahbub (2008) as the transfer of vibration often transmitted from work processes into workers hands, arms or fingers, mainly from hand held power tools. Damage can occur following as little as six months’ exposure.

Nerve damage, musculoskeletal conditions and restricted blood-flow to the hand and fingers occur. This can cause debilitating symptoms and effects, including grip strength reduction and symptoms suggestive of carpal tunnel syndrome.

Collectively this is known as HAVS. Symptoms may arise collectively or in isolation and result in both mild and severe HAVS. Mild HAVS is characterised by episodic blanching, numbness and tingling. As the condition becomes severe symptoms progress to cyanosis, skin necrosis and eventually to gangrene, although this is rare. The client may experience symptoms suggestive of HAVS whilst at work but these may improve in the period that the worker waits to consult their OH provider.

Neurological injuries first present with numbness in the fingers, impaired dexterity, and sensation to touch being significantly compromised. Diagnosis results in loss of work for safety reasons (Gemne et al,1997; Poole et al, 2015; Cooke et al, 2015).

Therefore, the detrimental impact of HAVS presents a wider issue; those no longer able to undertake their usual work processes leave a large financial burden on this population (Sutinen et al,2006; Hagberg et al,2002; Lawson et al, 2003).

Vascular changes within the fingers are termed “vibration white finger” (VWF) resulting from loss of perfusion to the fingers due to vasospasm leading to a loss of sensation in the hand and fingers (Ye et al, 2016; House et al, 2017).

Initially, symptoms of white finger may go unnoticed; only the finger tips are affected in less severe cases. However, in cases where exposure to vibration continues, the condition worsens, the effects become visible and the frequency of attacks increase. According to NERC (2011) VWF is the most widely known and observed clinical manifestation of HAVS.

A further category, musculoskeletal injuries, presents with loss of grip that can be associated with arthritis and a fundamental structural change in muscle fibres. Prolonged exposure to excessive levels of vibration can cause irreversible damage, severely affect ability to work and the quality of life. The degree of injury is related to the magnitude of vibration and the duration of the exposure.

Other factors such as the method of work, workplace temperature and damp or windy conditions also have a bearing on severity. Workers with medical conditions including diabetes, circulatory or nervous disorders are at increased risk of developing HAVS. Therefore, an individual’s health status and any medication must be taken into account when considering the adverse effects of HAV (NERC 2011).

The HSE (2017) reports that in 2016 455 new claims of vibration white fingers and 240 new claims of carpal tunnel syndrome related to HAVS were reported in UK. Furthermore, from 2007 to 2016 20 women and 7,335 males had reported vibration white fingers.

On top of this, 300 women and 3,315 men reported carpal tunnel syndrome related to HAVS (HSE, 2017). These statistics highlight HAVS as a persistent major health hazard faced by workers exposed to excessive vibration. Findings consistently suggest that early recognition of signs and symptoms and effective preventative control measures are key factors to managing the adverse health effects from vibration exposure (Mason, 2005).

Legislative requirements

Section 2 of the Health and Safety at Work etc Act 1974 encompasses the duty of care of employers to ensure the health and safety of their workforce. More specifically the Control of Vibration at Work Regulations (2005) is applicable in relation to work processes with the potential to expose employees to vibration. Under these regulations employers are required to:

• undertake risk assessments;
• control exposure using a hierarchy of controls approach;
• provide employees at risk with appropriate information, instruction and training on the effects of, and control methods which can be used to reduce exposure; and
• provide health surveillance for employees at risk.

In order to reduce/limit individual exposure, the Control of Vibration at Work Regulations (2005) stipulates that action to reduce exposure must be undertaken when a daily exposure action reaches 2.5 m/s2A (8) and a daily exposure limit value (ELV) is set of 5 m/s2A (8).

Regulation 5 requires employers to risk assess work processes identifying vibration exposures. This involves by observing working practices, including reference to the magnitude, type and duration of exposure. Risk assessments must be repeated should there be changes to work processes, practices or equipment.

Regulation 6 encompasses the responsibility of the employer to ensure that risks from vibration exposure are either eliminated at source or reduced to as low a level as reasonably practicable. Measures to mitigate vibration effects include providing:

• appropriately designed work processes and equipment which is well maintained;
• information and training for employees, such that work equipment may be used correctly and safely; and
• clothing to protect employees from vibration exposure and to cold and damp, which exacerbates the effects of vibration.

Regulation 7 requires health surveillance for those at risk in order that health effects linked with vibration exposure are identified at an early stage. (HSE 2005).

HAVS and the associated carpal tunnel syndrome (CTS) are both reportable occupational diseases as outlined under Regulation 8 of the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1995 (RIDDOR).

Management, prognosis and the responsibility of the employer

Effective control measures aimed at reducing exposure to vibration are essential as the effects of HAVS are irreversible (Heaver et al, 2011). The impact of a diagnosis of HAVS on a patient’s mental health is significant should changes to or even a loss of employment result, and the financial implications are potentially devastating. Implementation of protective and preventive measures for construction workers and others who are at risk of development of HAVS is vital (Weir et al, 2005; Chetter et al, 1997).

The associated costs of HAVS to the State, the employer and the sufferer are significant. As prescribed diseases, once diagnosed both HAVS and CTS entitle an employee to claim Industrial Injuries Disablement Benefit.

HAVS is estimated to cost employers millions of pounds per year in compensation (O’Hagan, 2012). By illustration, Balfour Beatty Ltd was fined £500,000 after the Health and Safety Executive found workers exposed to levels of vibration which put them at risk of developing HAVS (HSE, 2018).

Pathophysiology of HAVS

Vibration from hand-held tools that is absorbed by the hands and arms has the potential to affect anatomical structures, including the peripheral circulation and sensory and motor nerves leading to vascular and neurological effects.

Vascular effects

Soft tissues of the hand absorb the vibration, leading to mechanical vascular damage to blood vessels with additional neurological damage affecting vaso-regulation; consequently there is a close association between the vascular and neurological effects of HAVS. Finger blanching characteristic of HAVS is exacerbated by the cold, working in cold environments with cold tools worsens the condition.

Vibration exposure results in muscular contraction in the hand and arm that is transmitted to blood vessels. Vasospasm and vasoconstriction in turn reduces the supply of nutrients including oxygen and glucose to the tissues leading to ischeamia. There is a reduction in the production of adenosine triphosphate production stimulating anaerobic respiration affecting muscular function. Changes in pH and ineffective function of the sodium and potassium pump results and is associated with a reduced resting membrane potential (RMP) of neurones, muscle and cellular damage results.

If the plasma membrane cannot maintain the resting membrane potential, an influx of sodium ions occurs, leading to inflammatory changes within the dermis and epidermis of the skin, nerves and muscles, and an increase in blood viscosity, each affecting the hand and digits.

Immediately after finger blanching, increasing numbness, tingling and pain is frequently reported. This results from the return of blood circulation following tissue ischemia with subsequent tissue re-warming leading to reactive hyperaemia with reddening and painful throbbing sensations in the fingers. These symptoms generally worsen due to chronic inflammatory changes and are eventually present in the absence of cold.

The skin loses its elasticity; as a result increased collagen deposits within the skin. This affects vasoconstriction within the blood vessels of the digits, reducing peripheral circulation resulting in ischemic changes.

Neurological changes

Vibration exposure also causes inflammatory responses including epi-neural oedema and peripheral neuropathy (Gemne, 1997). Gemne (1997) refers to the damage of nerve endings and a loss of cutaneous peri-vascular nerve fibres in fingers, nerve fibrosis and de-myelinated neuropathy in the peripheral nerve trunk.

Eventually there is damage to mechanoreceptors, inducing sensory loss. Fine motor movements are compromised and chronic pain may result because of the effects on non-myelinated “C” nerve fibres involved in the transmission of chronic pain: mechanoreceptors, thermo-receptors and nociceptors.

Effects on muscle and soft tissue

The discomfort and stiffness reported by those with HAVS are associated with neural and muscular damage. Epithelial changes result in decreased release of, or increased metabolism and degradation of, nitric oxide from the endothelium. This decreases smooth muscle sensitivity (Gemne, 1997) and increases the laying down of collagen fibres.

Constant rapid exposure to vibration precipitates cell necrosis, affecting the ability to determine hand-grip pressure. The tool user then has a tendency to hold their work tools more tightly, so further constricting the blood vessels within the digits and further compounding the problem.

The literature does not yet paint a comprehensive view of the relationship between the cause (vibration) and resulting pathophysiology (neurological, vascular and musculoskeletal components) of HAVS. Several studies suggest that the knowledge on the exact mechanism leading from the chronic vibration to signs of HAVS in the clinical setting is not fully understood (House et al, 2010; Mahmood et al, 2014; Chen et al, 2016; Campbell et al, 2015).

Ye and Griffin (2016) highlight absorption of vibration by the muscles beyond their limits leads to tissue tears, bending and stress, creating tissue damage by increasing inflammation and oxidative stress.

Ebrahim et al (2014) note that the biopsy of abductor pollicis longus muscle in patients suffering from HAVS demonstrates muscle fibre damage which they propose is associated with prolonged vibration exposure.

The most common symptoms of HAVS include a vascular component, associated with secondary Raynaud’s phenomenon (Ong et al, 2015). Vascular symptoms of HAVS result from vasospasm in the vasculature in the hands and arms, resulting in loss of perfusion and ischaemia resulting in tissue blanching (Ye et al, 2016).

Blanching is a loss of blood supply, resulting in polyneuropathy and loss of sensation in the digits causing loss of feeling. There are clear health implications and significant workplace health and safety implications in relation to the employee experiencing such symptoms (Viktorova et al, 2016; Takemura et al, 2016). With prolonged ischaemia employees may develop cellulitis which if not treated quickly can lead to development of sepsis and septic shock (Levy et al, 2015).

Although the mechanical pathophysiological obstruction can be blamed on the vasospasm, studies fail to address the exact causal link between chronic exposure to vibration and vasospasm (Necking et al, 2004; Egan et al, 1996). However, Stoyneva et al, (2003) suggests that patients with HAVS have increased thickening of the smooth muscle in the digital arteries and they note that inflammatory factors and molecules such as endothelin-1, responsible for vasoconstriction, appear to be unregulated in these individuals.

Musculoskeletal HAVS, a common complication, is an inability to maintain the same grip strength as before HAVS developed. Such workers are prone to dropping equipment, dangerous when using electric saw or a pneumatic drill (Necking et al, 2004). Additionally, dropping objects accidentally, particularly if working at heights, could pose a risk to other workers and the public.

The pathophysiology of the musculoskeletal compartment is attributed to structural changes within muscle fibres diminishing their function reducing dexterity and grip strength (Bodley et al, 2015; Pavan et al, 2016) impacting negatively on their ability to undertake job tasks effectively impacting on their ongoing employability.

There seems to be little thrust in research for an industrial solution, without specialist equipment removing the risk factors of HAVS, some employers have little motivation to invest in equipment which allow workers to perform work tasks safely.

Neurological effects associated with vibration exposure and HAVS include loss of sensation, numbness, or tingling in the digits. Sensation loss results from polyneuropathy within sensory nerve endings in the digits due to myelin loss (Takemura et al, 2015).

Furthermore, studies indicate a loss of digital cutaneous perivascular nerve fibres in patients diagnosed with neurological HAVS. This is important as these nerve fibres are responsible for the production of calcitonin-gene related peptide, a vasodilator. Loss of this would alter the balance between vasoconstrictors and vasodilators, swaying the concentration of vasoconstrictors to be higher than vasodilators (Kuryliszyn-Moskal et al, 2015).

In contrast to vascular HAVS, the neurological symptoms of including finger numbness, is not exacebated by environmental factors such as temperature, (Bast-Petterson et al, 2015). As the signs and symptoms of vascular HAVS are made more acute as a result of a cold temperature, measures can be made to improve temperature of the hands through thicker gloves, and better insulation in the work place.

However, this is not the case for neurological or musculoskeletal HAVS, thus highlighting an unmet need, as well as further exacerbating the urgent need for developing preventative measures.

Activities of living are affected – simple tasks including lifting a kettle filled with water may be too difficult leading to implications for the individual and their family, who may need to assist with, or undertake tasks previously completed by the individual (Janicak et al, 2004).

HSE (2011) highlights the importance of breaks and stringent time monitoring for employees who are using vibrating equipment. Frequent breaks must be taken to prevent prolonged vibration exposure. Breaks in isolation are unlikely to be effective in reducing HAVS cases if the employee is still using the equipment daily for several years.

Health surveillance

A five-tiered health surveillance approach is used for workers exposed to vibration as follows

• Tier 1 (pre-employment). A worker self-administered questionnaire which may be supplemented by an OHN assessment. Baseline information can be recorded and there are opportunities to educate employees regarding measures they can use to protect themselves.
• Tier 2. An annual questionnaire completed by a responsible, competent person. This may be a supervisor, technician or an OHN. Provided no abnormalities are detected no further action is required at this point.
• Tier 3. This clinical assessment undertaken by a suitably qualified clinician (such as an OHN) incorporates recording a history and using a targeted clinical examination of vascular and neurological function of the arm and hand. This is supplemented with a musculoskeletal assessment. Objective tests included within this tier assess grip strength using a dynamometer, manual dexterity assessed using a Purdue peg board and neurological deficits assessed using monofilaments. Should symptoms suggestive of HAVS be noted a referral to an FOM HAVS approved occupational physician follows constituting the fourth tier.
• Tier 4. Standardised tests are used to make a formal diagnosis of HAVS. Once a diagnosis of HAVS has been confirmed HAVS this condition is reportable under RIDDOR. At this point the employer should be advised regarding the type of work that may now be appropriate.
• Tier 5. Tier 5 is optional and incorporates a referral to a specialist laboratory such as Health and Safety Laboratories.

Health surveillance is just one element of health protection for workers exposed to workplace vibration; effective control measures are of greater importance. Bazylevska et al (2017) highlight that health surveillance is crucial for detecting health issues at an early stage – early treatment can prevent the condition worsening.

Health surveillance allows employees to raise concerns about their present working environment and any potential health issues in relation to this (Gillibrand et al, 2016).

Conclusion

HAVS is a debilitating, preventable condition. It is essential that employers and employees are fully informed of the effects of vibration and of the need for effective measures to control exposure. An awareness of early signs and symptoms of HAVS amongst those working with vibrating tools is essential in order that early referrals to occupational health can be facilitated.

Significant factors in the development of HAVS includes failure to understand the importance of assessing risk and exposure levels, putting control measures in place then regularly evaluating and maintaining them. Only when all employees and employers take joint responsibility for full adherence to The Control of Vibration at Work Regulations (2005) will cases of HAVS significantly reduce.

References
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Ye, Y, and Griffin, M (2016). Assessment of two alternative standardised tests for the vascular component of the hand–arm vibration syndrome (HAVS). Occupational Environment Medicine, 73(10), pp.701-708.

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