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Lecture 19

Definition

Mechanical oscillation of a surface around its

reference point that occurs when mechanical

energy from oscillating source is transmitted to

another structure.

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Measurement Of Vibration

1. Direction of vibration forces

X axis - fore and aft

Y axis - side to side

Z axis – vertical (cephalo-caudal)

2. Parameters related to vibration

Displacement (m) x

Velocity (m/s) dx/dt

Acceleration (m/s2) dx/dt2

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Mechanism Of Action

1. All structures have their own natural vibration

level.

2. Human body and organs within human body

have own natural vibration level.

3. Suspended organs have higher natural

frequencies than structural parts.

4. Those parts of body with similar frequencies as

vibrating source resonate when in contact with

vibrations.

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Whole Body Vibration

Occupations: Bus and truck drivers

Heavy equipment operators

Miners

Helicopter pilots

Frequency: 2-100 Hz

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Musculoskeletal disorders

Intervertebral disc calcification

Disturbed visual acuity

Labyrinthine disorders

G-I disturbances

Increased heart rate

Increased respiratory rate

Increased cardiac output

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Segmental Vibration (Hand-arm)

Occupations: Exposure to vibration form hand tools

e.g. Power saws, Jackhammers, Grinders,

Sanders, Pneumatic drills

Frequency: 10-1500 Hz (Usually 125-300 Hz)

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Health effects:

1. Low frequencies (20-40 Hz): Degenerative osteoarticular lesions in elbows and shoulders

2. High frequencies (40-300 Hz): Hand-arm vibration syndrome (Vibration white finger, Traumatic vasospastic disease)

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Hand-arm Vibration Syndrome

(HAVS)

Symptoms range – mild intermittent symptoms –

constant progressive and severely restricting

activities of daily living.

Direct relationship between HAVS and increasing

acceleration – certain frequencies more harmful.

Shorter latency - more susceptible or more

exposure.

Vascular: vasospasm and blanching (Raynaud’s)

Neurological: tingling, numbness, loss of dexterity

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1. Pathophysiology not clearly understood.

2. Vascular problem – stages:

a) digital artery spasm

b) arterial hypertrophy

c) perivascular fibrosis

d) increased vasoconstrictor sensitivity

3. Nerve degeneration associated with myelin sheath – not

clear nerve injury primary or secondary to vascular change

4. Diagnosis based on signs and symptoms. Objective tests

–cold water provocation with Doppler flow studies in

digits.

Pathophysiology of HAVS

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Taylor-Pelmear System of Classification

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Clinical Management of HAVS

1. Reduce or eliminate exposure to vibration.

2. Until Stage 2, symptoms reversible on

eliminating exposure

3. Medical treatment with vasodilators – ineffective

in treating symptoms or preventing progression,

asked to stop tobacco use.

4. Stage 1 – counseled other jobs, Stage 2

strongly recommended, Stage 3 remove worker

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PREVENTION AND CONTROL OF

VIBRATION HAZARDS

1. Determine source of vibration.

2. Substitute production method or tool.

3. Redesign tool to reduce vibration.

4. Adequate maintenance of vibratory tools.

5. Provide flexible and warm gloves.

6. Pre-placement examination of all workers and

medical examination for workers with symptoms.

7. Exposure terminated if diagnosed with VWF DrYusofKLIA2012 18