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Conduct hearing assessments Contents Key to resources 2 Introduction 4 Identify significant features of client history 4 Select appropriate hearing assessment/s and explain procedure to client 5 Conduct assessments – pure tone audiometry 5 Identifying the need for further testing 7 Recording reliable results 8 Impedance audiometry 10 Tympanometry 10 Acoustic reflexes 12 Acoustic reflex decay 13 Use results to identify specific hearing loss and/or any abnormal functions 14 Summary 15 Further reading 16 Conduct hearing assessments © NSW DET 2007 1 This task guide is based on the following resources: Martin FN and Clark JG (2006) Introduction to Audiology (9th edn), Allyn and Bacon, USA* 3064-3 – Psychoacoustics 3064-9 – Audiometry-Assessment A 3064-10 – Audiometry-Assessment B 3064-2 – HLSP Audiometry – Pathologies (useful to review for this unit) *Note: The page number references provided for the textbook are based on the 9 th edition. If you have an earlier or later edition of the textbook, these pages numbers may not be the same ( but may be approximate). The headings are likely to be the same or similar in the various editions. The abovementioned resources – except for the textbook – are available in the Your Resources section. Key to resources Resource number Resource title 1 3064-3 Psychoacoustics 2 Martin FN and Clark JG (2006) Introduction to Audiology (9th edn), Allyn and Bacon, USA Chapter 2 The Human ear and simple tests of hearing Chapter 3 Sound and its measurement 3 Audiometry-Assessment A 3064-9 Pages 5-24 4 Martin FN and Clark JG (2006) Introduction to Audiology (9th edn), Allyn and Bacon, USA Chapter 4 Pure-tone Audiometry 5 Audiometry-Assessment B 3064-10 Topic 1 Identifying the need for further testing Topic 2 Post-basic assessment - Masking 6 Martin FN and Clark JG (2006) Introduction to Audiology (9th edn), Allyn and Bacon, USA Chapter 12 Nonorganic hearing loss 2 Conduct hearing assessments © NSW DET 2007 7 Martin FN and Clark JG (2006) Introduction to Audiology (9th edn), Allyn and Bacon, USA Chapter 6 Diagnostic hearing tests. Read pages 149-154 on Acoustic Immitance 8 Audiometry-Assessment B 3064-10 Topic 4 Tympanometry 9 Before you work through the readings below, you may wish to review the resource 3064-2-HLSP Audiometry – Pathologies (available in the Your Resources section). Martin FN and Clark JG (2006) Introduction to Audiology (9th edn), Allyn and Bacon, USA Chapter 8 The Outer Ear Chapter 9 The Middle Ear Chapter 10 The Inner Ear Chapter 11 The Auditory Nerve and Central Auditory Pathways 10 Martin FN and Clark JG (2006) Introduction to Audiology (9th edn), Allyn and Bacon, USA Chapter 6 Acoustic Reflexes 11 Martin FN and Clark JG (2006) Introduction to Audiology (9th edn), Allyn and Bacon, USA Chapter 6 Acoustic Reflex Decay 12 Audiometry-Assessment A 3064-9 Pages 25-31, examples of audiograms with their descriptions Conduct hearing assessments © NSW DET 2007 3 Introduction In this task guide you will learn about conducting hearing tests. Specifically, you will learn to: identify significant features of client history select appropriate hearing assessment/s and explain procedure to client wear appropriate personal protection clothing correctly and follow infection control procedures conduct assessments to produce valid, reliable and accurate results and in accordance with relevant policy and procedures use results to identify specific hearing loss and/or any abnormal functions record results in accordance with relevant policy and procedures. Identify significant features of client history Once you have taken a client history, you can establish a number of things: Is there anything of significance in the history that requires you to refer the client? Do you need to alter your usual basic test battery? Are there any additional tests you should carry out? The history should also give you a hint as to what you may expect to see. If your results are significantly different from what you expect from the case history, why is this? Now reflect on the questions below: What do you believe to be significant features of the client history that are able to give you the information you are looking for in the list above? Are the features purely medical, or do they involve personal, social and legal issues as well? 4 Conduct hearing assessments © NSW DET 2007 Select appropriate hearing assessment/s and explain procedure to client You now need to make a decision as to what type of assessment you are going to perform. The case history, in most cases, will tell you whether you are doing a screening test or a full hearing assessment. If the client is a child, you will need to use an age-appropriate assessment technique such as Play audiometry. What is the basic test battery in your clinic? Why would you veer from the usual tests? What extra tests might be done, or referred for? Conduct assessments – pure tone audiometry Conducting the hearing assessments is the bulk of your appointment, and the very reason most people are seeing you. You need to be able to select the appropriate tests, perform them in a valid manner and record results accurately. Before we launch into hearing tests, work through the following resource, if you have not done so previously. Go to Resource 1 Go to 3064-3 Psychoaccoustics. Go to Resource 2 Go to Introduction to Audiology, Chapters 2 and 3. Conduct hearing assessments © NSW DET 2007 5 You should now have an understanding of the concepts surrounding sound, the decibel and how sound is conducted along the hearing pathway. Check that you have a sound understanding of the following concepts: I am now familiar with this… anatomy of the ear Weber test sine waves longitudinal waves frequency spectrum intensity decibel sound pressure level hearing level sensation level pitch loudness localisation masking If you do not have a good understanding of any of the above concepts, revise your textbook. Now go to Resource 3 Go to Audiometry – Assessment A 3064-9 and work through pages 5–24 in this resource. Now go to Resource 4 Go to Chapter 4 in Introduction to Audiology. Also take a look at the CD-ROM that accompanies the textbook — look at the hearing test instructions in the Professional section. 6 Conduct hearing assessments © NSW DET 2007 You should also observe your supervisor doing hearing assessments, and when you are ready, start doing assessments on the people in your office and willing friends and family. When you and your supervisor are comfortable, that you are able to, start testing clients with your supervisor in the room and summarise each appointment in your log book. You should now be familiar with the following concepts: I am now familiar with this… audiometer pure tone narrow band masking noise headphones insert phones bone conductor interaural attenuation cross-heard signal masking air-bone gap sensorineural hearing loss conductive hearing loss mixed hearing loss sound proof environment tactile responses Hughson-Westlake technique patient response Identifying the need for further testing Now go to Resource 5 Go to Audiometry - Assessment B 3064-10, Topics 1 and 2. Once you have obtained the pure tone thresholds for AC and BC, you need to be able to look at your results and make a decision where further testing is necessary. In this context, it means whether you need to use masking to verify the pure tone thresholds you have recorded. Masking needs to be Conduct hearing assessments © NSW DET 2007 7 employed at any frequency where you are not sure from which ear (ie, cochlea) your recorded result stemmed. Think back to the concepts of interaural attenuation and any resultant crossheard signal. If there is a chance that the signal was heard by the non-test cochlea, then we need to keep this ear busy to ensure that the final recorded threshold is that of the test cochlea only. We do this by applying a noise to the non-test ear. This is what masking is all about. You will need to practice masking in your clinic time. Remember: air conduction masking is required if there is a 40dB (or greater) air-bone gap at any frequency. Once you are comfortable with the concept of masking and the techniques involved, start practising in the clinic and record your sessions in your logbook. Recording reliable results Sometimes the results we get may not be reliable. This may be due to a number of reasons: client didn’t understand the test procedure equipment failure client disability language barrier client was not co-operative. Client didn’t understand In the first instant, the client should be re-instructed to ensure they understand test procedure correctly. Equipment failure Equipment should have been tested at the start of the day. However equipment can become faulty during the day’s testing. Sometimes it is simple human error. The headphones may be on back to front, a switch on the audiometer may be in the wrong position or a cable has become unplugged. Check everything again. 8 Conduct hearing assessments © NSW DET 2007 Client disability The client may have a physical or mental disability. Age, either very young or very old, can impact on a client’s ability to understand what is required of them. You may need to repeat instructions using language appropriate to the mental age of the client. You can also change the way they respond, if a button is too difficult. Simply saying ‘yes’, tapping on the table, or raising their hand when they hear a sound can make all the difference. Language barrier If the client does not have a good grasp of English, they may have difficulty understanding instructions. Using gestures can often work, but the best way is to engage the services of an interpreter. For Australian citizens, there is a government interpreting service available. Client was not co-operative If the client was not co-operative, there is usually a good explanation. This is called non-organic hearing loss. The most common reason for people pretending to have a hearing loss is when they are children looking for attention or as adults when there is financial gain involved. This is generally the case if the client is seeking compensation for hearing loss incurred at the work place. In most cases, reinstruction, time out or a change of tester will get a reliable result. Remember never to accuse a client of faking results. You must always give them the opportunity to ‘save face’, and in most cases they’ll come around. If you are not able to elicit a reliable result, or results of audiometry, speech hearing tests and reflex thresholds are inconsistent, write ‘not for compensation purposes’ on the audiogram. This will alert all to the fact that the test was not a reliable one. Now go to Resource 6 Go to Introduction to Audiology and read Chapter 12 on non-organic hearing loss. Think about the study questions on page 362. Then reflect on the question below. Conduct hearing assessments © NSW DET 2007 9 Discuss with your supervisor what he or she does when they come across non-organic hearing loss. What are some of the tests you can do yourself, and what other tests can be performed by Audiologists to get a reliable result? Impedance audiometry ‘Impedance audiometry’ is a term that describes a number of tests which use a sound probe and pressure gauge to determine the health and functionality of the middle ear and the functionality of the contra and ipsilateral nerve pathways by using reflex arcs. This gives us valuable information about the health and functionality of the middle ear system, as well as the integrity or lack thereof, of the neural pathways that connect the ears. Impedance Audiometry should not be used in isolation and serves as a cross-reference to pure tone audiometry. For a great summary on these tests, go to the following website. www.emedicine.com/ent/topic374.htm Go to Resource 7 In Introduction to Audiology, read about acoustic immitance, pages 149– 154. Tympanometry Tympanometry is a test that gives us information about the functionality of the middle ear. Go to Resource 8 10 Conduct hearing assessments © NSW DET 2007 Read Topic 4 in Assessment B 3064-10. You should be familiar with the following concepts: I am familiar with… Compliance middle ear pressure volume Jerger types normal ranges To supplement and extend your reading, go to the resource below. Go to Resource 9 Read Chapters 8 to 11 in Introduction to Audiology. However, before proceeding to this resource, you may want to review the resource 3064-2HLSP Audiometry–Pathologies (available in the Your Resources section). Check if you are confident describing the major signs, symptoms and hearing loss patterns for the following pathologies. I am familiar with… otitis externa otitis media otosclerosis Meniere’s disease acoustic neuroma Activity Start practising tympanometry in your clinic. It should be part of your standard test battery. Conduct hearing assessments © NSW DET 2007 11 A CD-ROM accompanies your Introduction to Audiology.textbook. Look at the case studies section on this CD-ROM and see if you can readily identify the different types of tympanograms. Can you tell from them and the audiogram what pathology the client’s test results are consistent with and what referral path should be followed? _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ Logbook Start doing tympanometry testing on clients as a matter of routine and record your experiences in your logbook. Acoustic reflexes Acoustic reflexes are part of the impedance battery of tests. Go to Resource 10 Go to Chapter 6 in Introduction to Audiology and read the section on measuring the acoustic reflex on pages 159–164. In order to understand the anatomy and physiology involved, go to the Macquarie University, Department of Linguistics website: www.ling.mq.edu.au/ling/units/index.html Go to ‘Courses of study’ then ‘Undergraduate degrees’ then ‘Undergraduate units’ then click on the unit website and choose ‘SPH307 Auditory Physiology and Psychoacoustics’. Click on ‘Lectures’ on the top horizontal menu. Read these topics: 12 Conduct hearing assessments © NSW DET 2007 Outer and middle ear anatomy The cochlea Neural function and the auditory nerve Auditory cortex and central auditory processing. Note: Each section has a slide show available as well as notes and further text references. Acoustic reflex decay Acoustic reflex decay is a test performed after the reflex threshold test as a 10dB sensation level is required. This test is only done contralaterally and only at 500Hz and 1000Hz. Reflex decay indicates an 8th nerve lesion. Go to Resource 11 Go to Chapter 6 in Introduction to Audiology and read the section on acoustic reflex decay on pages 164–165. The presence of acoustic reflex decay is a good indicator for referring clients for further testing to exclude retro-cochlear pathology. Eustachian tube function test The Eustachian tube function test is also one of the Impedance tests, but is generally only used in specific circumstances such as in Diver and Pilot assessments. The ETF test is designed to determine whether the client is able to equalize pressure in the middle ear. This is particularly important for people wishing to dive as serious injury to the ear (barotrauma) is likely if the diver is unable to do this at will. Here is what the test involves the following: The impedance probe is inserted into the ear canal and a good seal established. Pressure is reduced to -200 mmH2O. Conduct hearing assessments © NSW DET 2007 13 Ask the client to swallow or yawn several times. Run a full sweep, the peak compliance should now be negative. Ask the client to perform a Valsalva manoeuver by pinching the nostrils and blowing up their cheeks, forcing air up the Eustachian tube and the middle ear pressure to equalize. Run another sweep, the peak compliance should now have returned to normal or positive. Clients wishing to do a diving certificate, who are unable to perform a Valsalva manoeuvre should not proceed as serious damage may be caused to their ears and or balance system as a result of barotrauma. Note: the ETF test requires an impedance meter which allows manual control over the pressure pump. Perilymph fistula A perilymph fistula is a tiny hole, usually around the area of the round window, which leaks perilymph fluid. This can make the client very dizzy, especially when there is a change in pressure. This might happen when they sneeze or blow their nose. Perilymph fistula can occur as a result of barotraumas, trying to stop a sneeze or trauma to the head. By changing the pressure in the ear canal it is possible to determine if a perilymph fistula is present. This test is performed by audiologists and Ear Nose and Throat surgeons. Use results to identify specific hearing loss and/or any abnormal functions Once you have your test results, it is important for you to understand how to interpret the results that you have. Your interpretation will result in your ability to: 14 determine whether or not hearing loss is present determine what type of hearing loss is present cross-referencing whether or not results from different tests are consistent with each other and with the case history determine the need for further testing and/or referral to an audiologist, medical practitioner or other third party explain to the client the nature of the impairment and how it is likely to affect them Conduct hearing assessments © NSW DET 2007 make recommendations to your client regarding the management of the impairment. Now reflect on the following: List all the hearing tests you have learnt about and the normal and abnormal results you may elicit. Think about what each result means, what your referral path would be and how you would write the report to convey your results clearly to your referral. Go to Resource 12 Read pages 25-31 of the resource Assessment A 3064-9. Discuss with your supervisor the results that require referral to an audiologist or medical practitioner. The Rehabilitation Outcomes document of the Office of Hearing Services also has information regarding the necessity to refer when certain conditions are present, but these are also appropriate criteria for non-government clients. Rehabilitation Outcomes, Department of Health and Ageing: www.health.gov.au/internet/wcms/publishing.nsf/Content/health-hearhroinfo Summary In this topic you have learnt about different pure tone audiometry, masking and impedance audiometry. You have learnt how to perform the tests, determine the need for further testing, the need for referral and the interpretation of results. Conduct hearing assessments © NSW DET 2007 15 Further reading If you wish to carry out further research, here are some urls for you to investigate. 16 www.ebme.co.uk/arts/art9.htm Overview of different audiometric assessment techniques www.ling.mq.edu.au/ling/units/index.html For excellent resources in auditory anatomy and physiology, linguistics and psychoacoustics www.ling.mq.edu.au/ling/units/sph307/papers Click on the undergraduate units. The following are of particular interest: Ling 210 Phonetics and phonology SPH301 Acoustics and speech SPH302 Speech physiology SPH307 Auditory physiology and psychoacoustics. Conduct hearing assessments © NSW DET 2007