lecture 20 vibration
DESCRIPTION
khaiTRANSCRIPT
Definition
Mechanical oscillation of a surface around its
reference point that occurs when mechanical
energy from oscillating source is transmitted to
another structure.
DrYusofKLIA2012 2
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
DrYusofKLIA2012 3
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.
DrYusofKLIA2012 5
DrYusofKLIA2012 6
Whole Body Vibration
Occupations: Bus and truck drivers
Heavy equipment operators
Miners
Helicopter pilots
Frequency: 2-100 Hz
DrYusofKLIA2012 7
Musculoskeletal disorders
Intervertebral disc calcification
Disturbed visual acuity
Labyrinthine disorders
G-I disturbances
Increased heart rate
Increased respiratory rate
Increased cardiac output
DrYusofKLIA2012 8
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)
DrYusofKLIA2012 10
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)
DrYusofKLIA2012 11
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
DrYusofKLIA2012 12
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
DrYusofKLIA2012 14
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
from exposure DrYusofKLIA2012 17
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