JSP 950 UNCONTROLLED ONCE PRINTED Leaflet 6-4-2

Transcription

1 ASSESSING AUDIOGRAMS -GUIDANCE FOR MEDICAL STAFF Summary 1. This leaflet informs medical staff of how to assess audiograms, including those performed as part of a MoD Hearing Conservation Programme. It should be read in conjunction with JSP 950 Lft Annex I (Guidelines for Screening Pure Tone Audiometry) and JSP 950 Lft (Noise at Work Health Surveillance) Introduction 2. This leaflet aims to provide guidance to clinicians 1 on how to assess a screening audiogram, including those performed as part of a Hearing Conservation Programme (HCP). It represents current best practice for DMS and should be followed unless specific reasons based on sound clinical acumen justify a different course of action. Background 3. Audiograms may be performed for a number of reasons, including clinical investigation of hearing loss, or as part of a HCP. The principles for assessing audiograms are the same, although the reasons for undertaking the audiogram differ. An important element of a HCP is to identify personnel who are more susceptible than average to the damaging effects of noise so that enhanced personal protective measures may be instituted. Therefore, appropriate care should be taken when assessing audiograms. 4. This revised policy aligns assessment of audiograms more closely with Health and Safety Executive (HSE) guidance. Work is ongoing to automate analysis of audiograms on DMICP to aid this process. 5. Precise diagnosis of the various causes of hearing loss from audiograms requires considerable experience. However, the basic assessment of an audiogram as normal or abnormal; identification of a significant change between two audiograms; or unilateral hearing loss is within the capability of appropriately trained clinicians 1. Audiograms should always be compared with previous results, unless it is an initial audiogram. The minimum reliably detectable change at any single frequency is deemed to be 10 db. However, a trend of increasing hearing loss across a number of audiograms is also abnormal. By following the guidance on this leaflet, clinicians should be able to identify those individuals who require referral for specialist Occupational Health and/or Specialist Audiological advice. Medical grading considerations 6. Noise Induced Hearing Loss (NIHL) may be suspected on the strength of screening audiometry results. However, because of the potential impact of the diagnosis on an individual's career and the potential liability issues, it should only be formally diagnosed by a Consultant in Occupational Medicine or Otorhinolaryngology 2 (ORL) after "gold standard" clinical audiometry has been performed at an audiology department, such as the Defence Audiology Service (DAS) based at the Institute of Naval Medicine. If NIHL is suspected then temporary downgrading may be appropriate to protect individual from further noise exposure, but appropriate specialist opinion as above is required before any referral for a permanent medical board. A flow chart providing guidance on analysis of audiograms is at Annex A. For further information and education, guidance on interpreting audiograms for 1 This will normally be a medical officer, but could include an appropriately trained nurse or audiologist. 2 Also referred to as Ear Nose and Throat ENT. Version 1.0 Oct 13 1 Last revised: 09 Aug 13

2 NIHL is at Annex B, but this policy does not require analysis of audiograms to formally diagnose NIHL. 7. In individuals who have had clinical audiometry confirming a lowered PULHHEEMS H category, if subsequent unit screening audiometry shows an improvement placing the individual in a higher H category, in the first instance the test should be repeated, ideally on a different day by a different operator. If this confirms the apparent improvement, the individual should be referred back for further clinical audiometry. Due to the less accurate nature of the test, personnel are not to be upgraded on the strength of unit based screening audiometry in these situations. Pre-test considerations 8. To avoid Temporary Threshold Shift (TTS) giving falsely poor results, individuals should not have been exposed to loud noise (on or off duty) for a minimum of 16 hours before audiometry. Where despite this, there is concern that there may still be TTS, the audiogram should be repeated after a longer period protected from noise - typically 48 hours to 2 weeks. However, it should be noted that in a military environment, it may be difficult to protect people from noise for prolonged periods. 9. Staff performing audiograms should refer patients with a current history of earache, discharge from the ear, balance problems or new onset tinnitus causing symptomatic problems, and those who have abnormalities on otoscopy, such as inflammation, fluid behind the tympanic membrane, perforation, blood or discharge for clinical review prior to performing the test. These individuals should be assessed to determine if audiometry should be undertaken or deferred. Acute outer or middle ear disease is likely to interfere with results. In these cases, appropriate treatment should be given and the test rescheduled until after the condition has resolved. If significant amounts of wax are present (here defined as obscuring more than 80% of the view of the tympanic membrane), the wax should be removed by somebody trained in the procedure. If ear drops or ear syringing are used, at least 48 hours should be allowed post treatment before audiometry. 10. If more significant ear disease is suspected, or if an acute condition fails to resolve, referral to an appropriate specialist should be considered. This referral should include copies of all previous audiograms, and a fresh audiogram may be clinically indicated as part of the investigation prior to referral. Assessing Audiograms 11. A flow chart providing guidance on analysis of audiograms is at Annex A. This is relevant both to review with the patient present, and routine review of audiograms for HCP. A complete assessment of the audiogram should be undertaken, even when referral is indicated on one of the earlier steps. This is to ensure that all relevant issues are identified prior to referral. 12. There is additional guidance for aircrew and other specialist trades in AP1269A and for other specialised branches, such as sonar operators, in BRd 1750A. 13. It should be noted that in the following guidance, different combinations of frequencies need to be summed. Care should be taken to ensure that the correct combination is used. Version 1.0 Oct 13 2 Last revised: 09 Aug 13

3 14. When assessing audiograms, individuals who have the following are considered more vulnerable to hearing damage: a. Poor hearing demonstrated previously by an abnormal audiogram. b. Tinnitus (ringing in the ears). 15. Step 1. If completed, review the questionnaire, and consider any relevant history. If the patient has been referred in, review symptoms directly with them. Perform a visual check of the audiogram to ensure it appears to be of an acceptable quality and includes all the frequencies 500 Hz, 1, 2, 3, 4, 6 and 8 khz for both ears. Inspect the audiogram for obvious abnormalities. Ensure thresholds at each frequency have been measured in 5 db increments, and that negative values have been recorded correctly. If any single frequencies show a difference between the right and left ears of 40dB or more, cross hearing may be present 3. Referral for clinical audiometry is required. 16. Step 2. Sum the hearing levels at 500Hz, 1 and 2 khz (low tones) and 3, 4 and 6 khz (high tones) for each ear to determine H grade in accordance with JSP 950 Lft The higher value sum, representing the worst frequency group, determines the individual's overall H grade for each ear. Therefore an individual with summed low tones of 25dB (H1 bracket) and summed high tones of 60dB (H2 bracket) should be recorded as H2. Negative values are to be are to be summed as negative, and not rounded up to 0. This is to ensure that the audiogram permits subsequent changes to be detected. For example look at the following audiogram: db HL 500 1k 2k 3k 4k 6k 8k Frequency (Hz) 3 When there is a difference of greater than 40 db between the ears at one or more frequencies, there is a danger that the sound may be transmitted through the skull and be heard by the better ear on the opposite side to that being tested. This is known as cross-hearing. This can lead to false results and errors in hearing grading and should be suspected in all cases of unilateral hearing loss. The problem of cross-hearing can be overcome by using specialist techniques such as masking (introducing noise into better ear), so any individual suspected of having cross hearing this should be referred to a service approved audiology service. Version 1.0 Oct 13 3 Last revised: 09 Aug 13

4 This should be recorded as: Frequency db 500 Hz -5 1kHz -5 2 khz 5 3 khz 10 4 khz 5 6 khz 5 8 khz 10 Sum Low tones -5 Sum High tones Step 3. Perform a visual comparison of the audiogram with the previous 2 tests (unless this is an initial entry audiogram). If clinically appropriate, consider reviewing more than 2 previous audiograms. If the comparison shows a difference from previous result of 15 db or more at any frequency 4 then ensure that there has been no significant noise exposure in the last 16hrs that there are no ORL or Upper Respiratory Tract Infection (URTI) symptoms. If the protocol at JSP Annex I has been followed, this should be the case. If not, arrange a repeat audiogram when any short-term illness is resolved and the individual has not been exposed to significant noise for at least 16 hrs. If there has been no noise exposure in the last 16 hours, and there are no ORL/URTI symptoms or any other reason to doubt the accuracy, or the repeat audiogram shows the same result, the audiogram should be assumed to be a true representation of hearing acuity and appropriate advice on avoiding noise exposure and use of routine or enhanced hearing protection should be given. If required (e.g. the drop is part of a rapid change or changes the H grade) then clinical referral should be made. 18. Step 4. Assessment of fitness for role. Determine if there has been a change in H grade for either ear. Check with ss guidance to ensure the H grade is appropriate to the individual s employment group. If there has been a change in H grade from H1 to H2 in either ear consider referral to ROHT for assessment. This is mandatory for employment groups requiring H1. If there has been a change to H3 or below in either ear, the individual is to be referred to a service approved audiology Service for clinical audiometry. If this confirms the individual is H3 or below referral is required to Service approved ORL, and ROHT. Referral to ORL should be made directly by the audiology department. 19. Step 5. Assessment of rapid hearing loss. Determine if there has been a loss of 30dB or more in the sum of 3, 4 and 6 khz (high tones) compared with either of the previous 2 audiograms within the past 3 years. If there has been in either ear, the individual is to be referred to a service approved audiology Service for clinical audiometry, and ORL opinion. Referral to OM should be considered depending on the final outcome. Individuals with proportionate loss at these frequencies (e.g. 10 db over one year or 20 db over 2 years) should be monitored carefully over the next few years. 20. Step 6. Assessment of unilateral hearing loss. Unilateral hearing loss may indicate organic disease, such as acoustic neuroma or can be found after blast exposure of a single ear. Sum the hearing levels at 1, 2, 3 and 4 khz in both ears. If there is a difference between right and left ear of 45dB or more the individual is to be referred to a service approved audiology Service for clinical audiometry, and ORL opinion. See footnote 3 above 4 Changes up to and including 10dB at a single frequency between screening audiograms may not be reliable, and may occur without ear disease being present. Version 1.0 Oct 13 4 Last revised: 09 Aug 13

5 on the risk of cross-hearing. Referral to OM should be considered depending on the final outcome. 21. Step 7. Age and gender specific assessment. Sum the hearing levels at 1, 2, 3, 4 and 6 khz for each ear. Select the worse score (higher sum) and compare with the table below. Sum of hearing levels 1, 2, 3, 4 and 6 khz Age Males (db) Females (db) Warning Referral Warning Referral The following action is to be taken depending on the outcome: Reporting a. Normal. Sum of 1, 2, 3, 4 and 6 khz is lower than Warning level. No action required. Remain on current HCP recall frequency. Consistent with HCP pass. b. Warning. Sum of 1, 2, 3, 4 and 6 khz is greater or equal to Warning level, but below Referral level. Inform patient and line manager and place an annual HCP recall. Consistent with HCP pass. c. Referral. Sum of 1, 2, 3, 4 and 6 khz is greater or equal to Referral level. The individual is to be referred to a service approved audiology Service for clinical audiometry, and ORL opinion. Inform patient and line manager and place an annual HCP recall. Consistent with HCP action required. Referral to OM should be considered depending on the final outcome. 22. Any condition requiring referral as detailed above should be regarded as an HCP action required in the first instance. Those with normal audiometry are a HCP pass. 23. In all instances, the individual should be informed of the result of the test. If any abnormalities have been found, they should be counselled on the extent and implication of hearing damage and ways to minimise or prevent further loss. This should include specific mention of avoidance of noise and correct use of any hearing protection provided. They should also be provided with information about any referrals indicated above, and when they are next due screening audiometry. This information may be provided by letter for individuals who have normal audiometry (HCP pass). 24. Line management are to be given a report from the clinician who has assessed the audiogram on the result of the HCP. This should be pass or action required. If graded as action required, the report should advice on the fitness of the individual to work in noise hazardous environments and whether they require any additional hearing protection Version 1.0 Oct 13 5 Last revised: 09 Aug 13

6 measures. No clinical information is to be included, and the patient must informed of the content of the report and given an opportunity to see it. Verbal consent is to be obtained to the release of the report before it is sent to line management. If the individual does not consent to release of the report, line management are to be informed of this fact, but not the result of the audiometry. Subsequent action is not a medical responsibility in these circumstances. 25. Where locally agreed, it is acceptable for result of those who pass to be submitted to line management as a consolidated periodic report. It is suggested that this be at least monthly. Report for individuals requiring action should be submitted immediately to ensure they are not exposed to unnecessary risk. 26. It is a line management responsibility to review results for employment groups to identify trends. This may require re-evaluation of the noise risk assessment, checking worker s hearing protection for fit, suitability and compliance. It may also involve retraining and reinforcement of the correct use of hearing protection and advice on other hearing conservation methods. Implementation 27. Unless cancelled or otherwise revised, this leaflet will be automatically reviewed after five years. Surgeon General will make this policy leaflet publicly available in accordance with the legislation concerned with freedom of information. However, this policy leaflet is not to be published on the Internet without the express permission of the author. Where elements of this leaflet become further incorporated into ss policies and procedures that might affect individuals from minority groups, action addressees are to ensure that the information is made available in a culturally appropriate manner this includes providing translation where required. An Equality Analysis has been undertaken in the production of this policy and no impact is anticipated in terms of the Equality Act Authorisation 28. This policy is released for publication by Head of Medical Strategy and Policy on behalf of the Surgeon General. Point of contact 29. Further advice concerning this leaflet can be obtained from the Civilian Consultant in Occupational Medicine or SO1 Occupational Medicine at HQ SG. General enquiries should be addressed to SG ACDS StratPol-Med Pol SO2 telephone (Mil ). Version 1.0 Oct 13 6 Last revised: 09 Aug 13

7 JSP 950 UNCONTROLLED ONCE PRINTED Annex A to Leaflet Dated 09 Aug 13 Version 1.0 Oct 13 Last revised: 09 Aug 13

8 JSP 950 UNCONTROLLED ONCE PRINTED Annex B to Leaflet Dated 09 Aug 13 BACKGROUND INFORMATION ON THE USE OF PURE TONE AUDIOMETRY IN THE DIAGNOSIS OF NOISE-INDUCED HEARING LOSS. Introduction B1. In order to make a diagnosis of noise-induced hearing loss (NIHL), 3 requirements must be satisfied: a. A history of exposure to loud (> 85 db(a)) noise for a significant period. b. A high frequency (3, 4, or 6 khz) hearing impairment. c. The presence of a notch or bulge in the audiogram. B2. An audiogram which shows high frequency impairment, and a notch or bulge is not sufficient in order to establish a diagnosis of NIHL, as the same pattern can be seen due to other causes. The estimation of lifetime noise exposure in industry is reasonably simple if an employee has used the same equipment regularly over a long period. However, the same does not hold true in the case of Service personnel, who may be exposed to very loud noise at irregular intervals. Deployment on operations may increase the exposure, both from an individual s own weapon, and also noise and blast from hostile fire. Given the difficulty of measuring noise exposure in the Service environment, and given the requirements of hearing conservation, NIHL is usually assumed if the audiometric criteria have been met and there is no alternative explanation (i.e. ear disease) for the hearing impairment. B3. Blast Injury. These guidelines apply to the diagnosis of conventional NIHL as opposed to the effects of impulse noise (e.g. blast). Blast injury may give rise to hearing impairment with different characteristics, and its diagnosis is based upon the history of proximity to an explosion and its temporal relationship to hearing impairment. Normal Audiometry B4. Pure tone audiograms measure an individual's hearing thresholds compared to the reference value for an 18 year old, which is set at threshold of 0 db. Since the accuracy of pure tone audiometry is ± 5 db at any frequency, a typical audiogram will show a minor degree of irregularity (Figure 1). The shaded area shows the middle two quartiles of the normal range at the age of 20 years. Version 1.0 Oct 13 B-1 Last revised: 09 Aug 13

9 JSP 950 UNCONTROLLED ONCE PRINTED Annex B to Leaflet Dated 09 Aug 13 Age-Associated Hearing Loss Figure 1: normal hearing B5. Hearing declines with age, although at different rates for men and women. The decline due to age-associated hearing loss (AAHL) is more marked in the higher frequencies. As with other characteristics associated with ageing, the rate of change varies from individual to individual. A typical audiogram of a 50 year-old man is shown in Figure 2 - the shaded area shows the middle two quartiles. Figure 2: Age-Associated Hearing Loss Version 1.0 Oct 13 B-2 Last revised: 09 Aug 13

10 JSP 950 UNCONTROLLED ONCE PRINTED Annex B to Leaflet Dated 09 Aug 13 Noise-Induced Hearing Loss B6. Men and women also show different levels of NIHL, men being more affected, presumably by greater exposure. The characteristic pattern of NIHL is a notch whose maximum depth is at 4 or 6 khz (Figure 3). Because the accuracy of the measurement of the hearing threshold at each frequency is ± 5 db, the smallest notch that can be reliably detected is 10 db. It is important to measure the threshold at 8 khz in order to differentiate between NIHL and AAHL. This is shown at Figure 4, where the sole difference between the audiograms in is the threshold at 8 khz. The left audiogram shows AAHL, but no evidence of NIHL: the right one is consistent with NIHL. Figure 4: the requirement for 8 khz B7. The downward-sloping audiogram in AAHL may change a notch produced by NIHL into a bulge (Figure 5). Although the precise assessment of a bulge is somewhat complex, an approximation may be obtained by drawing a straight line between the thresholds at the lower edge of the bulge (typically at 2 or 3 khz) and at 8 khz. The depth of the bulge is found where the distance between the straight line and individual frequency thresholds is greatest (shown arrowed). As with a notch, it must be at least 10 db deep to be significant. Version 1.0 Oct 13 B-3 Last revised: 09 Aug 13

11 JSP 950 UNCONTROLLED ONCE PRINTED Annex B to Leaflet Dated 09 Aug 13 Acknowledgement. Figure 5: NIHL - a bulge These guidelines are a simplified version based upon Coles R.R.A., Lutman M.E., Buffin J.T. (2000) Guidelines on the diagnosis of noise-induced hearing loss for medico-legal purposes. Clinical Otolaryngology, 25, Version 1.0 Oct 13 B-4 Last revised: 09 Aug 13