Lecture 6 Notes PDF

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9/11/20 CSD 201 Pure Tone Audiometry 

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Test o A comprehensive hearing test begins with a detailed case history and visual examination if the outer and external ear canal (otoscopy) o Pure tone audiometry is made up of air conduction and bone conduction tones o The device that the tones are presented by is called audiometer o This is how we determine the patient’s threshold o The audiometer must meet the standards of the American National Standards Institute (ANSI) o This ensures that all audiometers are consistent in the thresholds that are obtained o The audiometer must be calibrated annually Test Environment o The quietest possible situation is necessary for hearing testing o The most common method is to utilize a sound treated booth o ANSI has background noise standards that can only be met in a sound booth o Additional method for reducing ambient noise are:  Use earphone enclosure devices for supra-aural earphones  Use insert earphones Patient Responses o Different responses o Signal button that illuminates on the audiometer  Reduces the subjective info that the clinician may provide o Raise hand  Most widely used  Responses gives info on how the patient responds and the level that produced the response  The hand raise sometimes becomes more hesitant when at or near threshold  Raise the hand on the side of the tone o “Yes, No, I hear it” can be used for children Patient Positioning o The adult patient should not be able to see the clinician o The patient may be seated at a 90-degree angle or seated with their back to the audiometric/clinician  + eliminates observation of the clinician  - eliminates observation of patient’s facial expression during testing o This may be helpful with functional HL Air Conduction Testing

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o Purpose: to specify the amount/ degree of the hearing loss o Typically completed under supra-aural headphones (TDH-39) or foam insert earphones  Can also be completed in soundfield through speakers but not ear specific o Positioning of earphones  Supra-aural earphones should be placed so that the diaphragm of the earphone is directly over the opening of the ear canal  Supra-aural earphones can cause collapsing ear canals in children and in elderly Air Conduction Procedure o Begin testing with the better hearing ear first o The presentation order of the frequencies will be: 1K, 2K, 4K, 8K, 1K again, then 500 and 250 Hz  1K is the most sensitive frequency for normal hearing individuals, less sensitive to BGN and has the best test/retest reliability of all of the frequencies  Mid octave frequencies such as 750, 1.5K, 3K, and 6KHz should be tested when octave frequencies differ by 20 dB or more o A (pulsed) pure tone is presented at 30 dB HL  1-2 seconds  If a response is given, the tone is lowered by 10 dB HL steps until no response is given o Then the tone is raised by 5 dB HL steps until a response is obtained o This is repeated until the 50% threshold response criterion has been met  This is the level at which the patient can correctly identify 3 out of 6 tone presentations o The average of threshold levels at 500, 1K, 2K, and 4KHz is called the Pure Tone Average (PTA) Severity of Hearing Loss o -10 dB to 25 dB- normal o 26 dB to 40 dB- mild hearing loss o 41 dB to 55 dB- moderate hearing loss o 56 dB to 70 dB- moderately severe hearing loss o 71 dB to 90 dB- severe hearing loss o Over 90 dB- profound hearing loss Bone Conduction Audiometry o The purpose- determine the patient’s sensorineural sensitivity  AC- determines the degree/severity of the HL  BC- determines the type of HL present o Measurements are taken with the bone conduction transducer on the mastoid process (or on the forehead)  Should not touch the pinna and glasses should be removed

The procedure is the same as AC testing although the range of frequencies and the maximum intensities are more limited: 250 through 4000 Hz (500-4000) Types of Hearing Loss o Determined by bone conduction scores  Conductive  Sensorineural  Mixed Conductive Hearing Loss o Characterized by normal bone conduction scores with abnormal air conduction scores o Behavioral symptoms of CHL  Will demonstrate no difficulty in word recognition ability if a sufficiently loud signal is presented  As long as the signal is intense enough to overcome the conductive component the cochlea with discriminate normally o May speak softly due to the occlusion effect of the CHL Sensorineural Hearing Loss o With SNHL both AC and BC thresholds are outside of normal limits and the AC and BC thresholds are within 10 dB of each other o Symptoms  Talking in a loud voice  Patient cannot hear his own voice through BC, therefore he raises his voice so it sounds “normal” to him o Decrease in word recognition ability even at increased presentation levels o Caused by damage to the hair cells of inner ear damage to the nerve fibers o The typical SNHL is characterized by better low frequency hearing with poorer high frequencies o Consonants contain HF information and vowels are predominantly low in frequency o Consonants may not be heard or may be confused o You should keep in mind that even when speech is audible, it may not be intelligible Mixed Hearing Loss o Both air and BC thresholds are below normal but ABG (air bone gap) is present o Has both SN component (decreased BC scores) and conductive components (AC scores at least 15 dB greater than BC scores) Cross Hearing o In cases where one ear has significantly improved hearing over the poorer ear, sound can “leak” or crossover to the non-test which will be heard and responded to o Interaural attenuation  Supra-aural- 40 dB 

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Inserts- 60 dB BC- 0 dB...