Cha v CFM Engineering Pty Ltd

[2022] NSWPICMP 528

DETERMINATION OF APPEAL PANEL
CITATION:	Cha v CFM Engineering Pty Ltd [2022] NSWPICMP 528
APPELLANT:	Byung Ho Cha
RESPONDENT:	CFM Engineering Pty Limited
Appeal Panel
MEMBER:	Richard Perrignon
MEDICAL ASSESSOR:	Joseph Scoppa
MEDICAL ASSESSOR:	Robert Payten
DATE OF DECISION:	22 December 2022
CATCHWORDS:	wORKERS cOMPENSATION - Appeal from assessment of 6% whole person impairment (binaural hearing impairment); whether Medical Assessor (MA) erred in excluding hearing levels below 2000hZ from assessment; whether MA erred in calculating total noise-induced and other losses from data in the Cortical Evoked Responses (CERA) table; Held – Medical Assessment Certificate revoked.

BACKGROUND TO THE APPLICATION TO APPEAL

1. The appellant worker appeals from the Medical Assessment Certificate of Medical Assessor Williams dated 26 September 2022, who assessed a 6% whole person impairment (binaural hearing loss) as a result of injury on 30 June 2014 (deemed date).

2. In doing so, he excluded hearing loss below 2kHz, because the results on bone conduction testing were ‘flat’.

3. He calculated the percentage of total binaural hearing impairment in each of six frequency ranges, and combined them to produce a total of 45.7% binaural hearing impairment. From this, he deducted 33.1% for ‘pre-existing non-related loss’, and a further 0.4% for presbycusis, yielding an adjusted binaural hearing impairment of 12.2% resulting from injury.

4. This converts to 6% whole person impairment.

5. The appellant alleges that the Medical Assessor erred:

   (a)    by excluding hearing losses below 2kHz from his assessment, and failing to give adequate reasons for doing so;

   (b)    by assessing work-related hearing loss at 12.2%, inconsistently with the figures for work-related losses in the final column of the table which add up to 20.6%, and

   (c)    by assessing pre-existing (non-work-related) hearing loss at 33.1%, in circumstances where the difference between total hearing losses of 45.7% and work-related losses of 20.6% is 25.1%.

6. The Appeal Panel conducted a preliminary review of Medical Assessor Williams’ medical assessment in the absence of the parties and in accordance with the NSW Workers Compensation Guidelines for the Evaluation of Permanent Impairment (4th edition) (the Guidelines). Though it identified demonstrable error, the error was capable of correction without further examination.

Submissions

1. The appellant’s submissions are summarised above.

2. In summary, the respondent submits:

   (a)    that the Guidelines were correctly applied;

   (b)    that the Medical Assessor’s reasons are not to be minutely construed with an eye keenly attuned to perception of error, and

   (c)    that the reasons given were adequate and consistent with the outcome.

Exclusion of hearing loss below 2kHz

1. On examination, the Medical Assessor noted at [5] that both external auditory canals were partially obscured by earwax and that both tympanic membranes were retracted. He also reported that tympanograms were abnormal on both sides.

2. At [10a], he gave the following reasons for excluding hearing losses below 2kHz from his assessment of work-related hearing loss – emphasis added:

   “… Physical examination shows retracted tympanic membranes and my CERA indicate a bilateral sensorineural hearing loss maximal in the high frequencies and conduction hearing losses (bilateral mixed hearing loss).  The responses I obtained upon my CERA are repeatable on ascending and descending threshold measurement and I considered them to represent accurate auditory thresholds.  The configuration of his sensorineural hearing loss is not one wholly caused by his occupational noise exposure as described above. 

   Therefore considering his medical history and medical examination including my CERA, I formed the opinion that his sensorineural hearing loss at 2-4kHz inclusive is caused by occupational noise exposure, and his sensorineural hearing losses below 2kHz are not caused by his occupational noise exposure.  The configuration of the sensorineural hearing losses on the CERA below 2kHz is flat, which in combination with the extent of all the hearing losses below 2kHz indicates the sensorineural hearing losses below 2kHz are inconsistent with being caused by his occupational noise exposure.  The conduction hearing losses in both ears are unrelated to his occupational [sic] because occupational noise induced hearing loss of gradual process will not cause conduction hearing losses.”

3. We note in passing that the reference in the last sentence to ‘conduction’ hearing losses appears to be a clerical error. ‘Conduction’ losses are those measured by placing the sound emitter hard against the mastoid bone. That is an accurate measure of sensorineural loss, which can be caused by noise exposure, including exposure in the workplace. We consider that Medical Assessor Williams meant to say that noise-induced hearing loss does not necessarily cause conductive hearing loss – that is, hearing loss measured by emitting sound into the air in the ear canal. Such losses may result from earwax or abnormalities of the tympanic membrane, for example, which was the case here.

4. The Medical Assessor’s reasons are to be understood as a whole, when read in combination with the CERA table which followed them.

5. That table records hearing levels for the left and right ear separately in each of the six frequency ranges. In each case, ‘air’ and ‘bone’ conduction readings are recorded separately.

6. In this case, hearing levels recorded for bone conduction are a better indicator of true sensorineural hearing loss, because they eliminate superficial, ephemeral interferences such as ear wax and retracted eardrums (both of which were observed to be present bilaterally in this case). For the same reason, air conduction readings are less reliable. Both the Medical Assessor’s reasons (above) and his conclusions demonstrate that he has preferred bone conduction as the more reliable indicator for sensorineural hearing loss. In our view, that approach was reasonably open to him, and appropriate.

7. In the range 500hZ to 2000hZ, left ear bone conduction - recorded at 15dB in each case – demonstrated normal hearing. There was no measurable loss. These results, if produced in the form a graph, would appear ‘flat’, as the Medical Assessor described it.

8. In the same range, right ear bone conduction is recorded at 15dB (normal) at 500hZ, and at 20dB (near normal) from 1000hZ through to 2000hZ. If produced in a graph, these results also would appear to be flat, or nearly so.

9. Hearing loss caused by noise exposure tends to increase with frequency. That was not the pattern displayed on bone conduction. From 1000hZ through to 2000hZ, hearing level in the right ear was constant at 20dB. Though there is a minimal progression of loss from 15dB to 20dB between 500hZ and 1000hZ, the pattern, when viewed from 500hZ to 2000hZ, is too stable (or ‘flat) to attribute the loss to noise exposure.

10. In our view, between 500hZ and 1500hZ:

    (a)    the normality of bone conduction readings in the left ear precluded a finding of noise-induced hearing loss, and

    (b)    the near normality of bone conduction readings in the right ear, together with the nearly flat nature of progression with frequency, justify the assessor’s finding that such minimal loss as occurred is unlikely to be noise-induced.

11. When the Medical Assessor’s reasons are read together with the CERA table, they are sufficient to enable an expert to understand the path of reasoning followed.

12. When properly understood, the reasoning was correct. The conclusions reached were consistent with it, and reasonably open to the Medical Assessor.

13. We can identify no error in this respect.

CERA table – alleged errors of calculation

1. In the CERA table, the Medical Assessor listed total percentage hearing losses for each of the six frequency ranges tested. He correctly added these to produce a total of 45.7% binaural hearing impairment.

2. In the final column, he also listed the percentages of work-related binaural hearing impairment in each range. When combined, these produce a total work-related hearing impairment of 13.5%. Deducting 0.4% for presbycusis assessed by the Medical Assessor yields a 13.1% adjusted work-related binaural hearing impairment. In his Table, the Medical Assessor calculated this figure as 12.2%. That calculation was in error.

3. The difference between 13.5% and total binaural hearing impairment of 45.7% is 32.2%, which represents non-work-related losses.

4. The Medical Assessor calculated the latter figure as 33.1%. That calculation was also in error.

5. Subtracting 32.2% and presbycusis of 0.4% (measured by the Medical Assessor) from total binaural hearing impairment of 45.7% yields work-related binaural hearing impairment of 13.1%. The same results is produced by subtracting 0.4% for presbycusis from the total work-related losses of 13.5%.

6. As indicated, the Medical Assessor calculated an adjusted (work-related) binaural hearing impairment of 12.2%, which was also in error.

7. The 13.1% adjusted binaural hearing impairment converts to 7% whole person impairment.

Conclusion

1. The appeal succeeds in part. The calculation of percentage binaural hearing impairment due to noise exposure was incorrect, demonstrating error on the face of the certificate.

2. Correctly calculated on the basis of the Medical Assessor’s examination, binaural hearing impairment resulting from injury was 13.1%. This converts to 7% whole person impairment.

3. The Medical Assessment Certificate of Medical Assessor Williams is set aside and replaced with the attached Medical Assessment Certificate.

APPEAL PANEL

MEDICAL ASSESSMENT CERTIFICATE

Injuries received after 1 January 2002

Matter Number:	W1745/22
Applicant:	Byung Ho CHO
Respondent:	CFM Engineering Pty Limited

This Certificate is issued pursuant to s 328(5) of the Workplace Injury Management and Workers Compensation Act1998.

The Appeal Panel revokes the Medical Assessment Certificate of Medical Assessor Williams and issues this new Medical Assessment Certificate as to the matters set out in the Table below:

MY CERA Audiogram

Injury deemed to have happened on:	Frequency Hz	Left dB HL Air        Bone		Right dB HL Air          Bone		Total % BHI	Occupational % BHI
30.6.2014	500	35	15	30	15	3.4	0.0
1000	45	15	50	20	10.5	0.0
1500	55	15	55	20	11.2	0.0
2000	50	15	55	20	7.4	0.3
3000	65	>45	65	>45	7.0	7.0
4000	60	55	75	55	6.2	6.2
TOTAL % BHI: 45.7%
Less Pre-existing non-related loss: 32.2%
Less Presbyacusis correction: 0.4%
Add % of severe tinnitus: 0.0%
Adjusted total % BHI: 13.1%
Resultant total BHI of 13.1%  =  7% whole person impairment (Table 9.1)