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- Evaluation of Noise Induced Hearing Loss and Presbycusis Using
Internet-Based Software
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- Noise Induced Hearing Loss
- Presbycusis: Definitions and Measurement
- Hearing Handicap Determination & Medical Legal Concerns
- Client Evaluation
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- Sensory hearing loss with loss of discrimination commensurate with the
loss in hearing.
- Maximum in the high frequencies sometimes with a 4000 Hz Notch.
- 23% will have tinnitus (Phoon WH, 1983)
- Vertigo is not present
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- After 10 years of exposure, the damage caused by noise remains constant,
but presbycusis progresses as predicted.
- Passchier-Vermeer, W Hearing Loss due to Exposure to
Steady-State Broadband Noise.
IG-TNO report no. 35. Delft,The Netherlands: Research Institute for Public Health
Engineering, Sound and Light Division (1968)
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McCrae JH, Noise-induced hearing loss and
presbyacusis. Audiology 10:323-333,1971.
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- Individuals have different susceptibilities to noise.
(Kyong-Myong Chon, 1996)
- Noise levels are measured in dB SPL on the A Scale.
- Impulse Noise is more damaging than a constant noise.
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- OSHA
- 25% chance of developing NIHL with a 40-year lifetime exposure
- NIOSH
- 8% chance of developing NIHL with a 40-year lifetime exposure
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- OSHA Maximum Exposure
- = 16 / (( dB – 85 ) / 5 ) 2
- NIOSH Maximum Exposure
- = 16 / (( dB – 82 ) / 3 ) 2
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- Pure Presbycusis refers to the hearing loss which occurs with
physiological aging. Schuknecht divided "Pure
Presbycusis" into sensory, neural, strial (metabolic) and cochlear
conductive
- Nosocusis refers to hearing loss caused by other factors than noise and
pure presbycusis (aging).
- Sociocusis non-work related noise induced hearing loss.
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- Accounting for presbycusis is not mandatory but it is often done in the
legal setting. What is actually sought is to account for
non-occupational hearing loss. Seven states allow deductions for
presbycusis.
- Or to answer the question: Is the
progression of hearing loss in the worker more than which can be
expected from non-occupational hearing loss?
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- NIOSH does NOT recommend accounting for presbycusis when looking for Medical
Causation of a progressive hearing loss. If a worker has a progressive hearing
loss it is assumed to be due to noise trauma and corrective measures
should be taken.
- However, estimation of presbycusis is used for compensation
purposes. The test for
compensation is whether the hearing loss is medically more likely than
not caused by noise exposure.
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- Several researchers have studied primitive cultures to determine the
influence of aging on hearing acuity in the absence of occupational
noise. These studies found aging effects on hearing, but observed
no sex difference in the hearing loss. Goycoolea MV, 1986; Rosen S, 1962
- Animal studies have also found no sex difference.
Hunter KP, 1987
- It has been proposed that the difference between male and female
thresholds as a function of age, is due to environmental factors.
The most important of which is noise exposure. Kryter KD, 1983
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- However, Spoor's Equations (1967) and Robinson Sutton's (1979) Data in
ISO-1999 Annex A were derived from populations screened for noise
induced hearing loss and there is still a marked difference between the
sexes. Rosenhall (1990) also found a gender difference when noise
exposure was compensated for.
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- Robinson Sutton's Equations: These equations were derived by
combining a number of studies and are adopted for the values in ISO-1999
Annex A
- Spoor's Equations: Combined data from 8 different studies.
Spoor accounted and controlled for noise in the derivations of his
equations.
- OSHA (Occupational Safety and Health Administration) has published
correction values for aging. These values will correct threshold
frequencies of 1000 Hz to 6000 Hz. Since no values are given for
500 Hz, this method can only be used with the NIOSH and Wisconsin
equations.
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- Determination of a hearing impairment from an audiogram is performed by
one of the predefined equations.
- The equation selected is often dictated by statue, not by medical
opinion.
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- Uses 1000, 2000, 3000, and 4000 Hz.
- The equation was first proposed for detecting the early effects of noise
on inner ear function.
- It is now used by the Federal Government for compensation purposes.
- Dobie, fells that this is not the best equation to use, since the mean
frequency of speech recognition is 1600 Hz. The best representative frequencies
are 500, 1000, 2000, & 4000 Hz
(Dobie RA, 1998)
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- Employers will argue for the use of the AAOO-1959 Equation.
- Plaintiffs will argue for the use of the NIOSH-1997 Equation.
- A good compromise is the AAO-1972 Equation.
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- The percentage of handicap due to presbycusis is often determined by
ISO-1999 Annex A (Robinson Sutton's Data). It is assumed that
presbycusis and noise trauma are additive but one can argue in severe
hearing losses that this is not true. However, legally this is a
mute point. Since, either the two are additive and the percentage
of presbycusis is predicted by Robinson Sutton's Equations or if they
are not additive then some of the noise trauma prevented some
presbycusis from taking place, or visa versa. Thus, this
percentage of noise trauma caused no harm and therefore would still not
be compensatible.
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- It is assumed with all of the calculators that hearing loss due to noise
and presbycusis are additive.
- ISO 1999 compression factor is applied when projecting audiometric data.
- Hearing Loss = ARL + NIL - (ARL * NIL)/120
- ARL: Age Related
Loss, NIL: Noise Induced Loss
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- Answer the Question: Is the
hearing loss in the patient’s employment exit audiogram greater than
that expected from the effects of aging on the pre-employment audiogram?
- Remember the test is “medically more likely than not.” In other words: Your opinion has a greater than 50%
chance of being correct.
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- Finally, the client’s hearing handicap is used to determine the “Total
Body Handicap.”
AMA Guide to Permanent Impairment, 4th ed.
- A 100% hearing handicap will have a total body handicap of 35%.
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- Other ear diseases can cause a hearing loss.
- Other associated systemic diseases which can cause a hearing loss.
- Other exposure to noise trauma.
This is very important because noise exposure’s effects on the
inner ear are finite and will cause no further damage after
approximately 10 years. Thus, it
could be argued that the plaintiff's occupational exposure to noise
caused no harm because of his home/recreational exposure.
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- Vertigo
- Endolymphatic Hydrops
- Perilymph Fistula
- Dizziness
- Eustachian Tube Dysfunction
- Tympanic Membrane Perforation
- Ossicular Fixation or
Discontinuity
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- Ototoxic Drug Use
- Otologic Ear Infections
- Meningitis
- Head Trauma
- Alcohol Usage
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- Hunting. Kryter KD, 1991 found that 69% of 9800 railroad
workers used guns.
Most have an asymmetrical hearing loss.
(Job A, Grateau P, Picard J, 1998)
- Home machinery – Lawn mowers,
weed trimmers, etc.
- Chain saws
- Loud Music, Rock Concerts
(Yassi A et al Canadian Family Physician, 1993)
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- Examination of the ear
- Tuning fork and whispered voices
- Full ENT examination
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- No exposure to noise for 24 hrs.
- Air & Bone Conduction
- Speech Reception Thresholds
- Speech Discrimination
- If unilateral – Stenger Testing
- Tympanometry
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Notes
