LECTURE 6.pdf

Paediatric Audiology RHS 472 Lecture 6: Diagnosing Hearing Disorders in Infants and Children Behavioural Hearing Tests for Infants and Children Part Two: Visual Reinforcement Audiometry (VRA) Dr Arwa AlJasser Email: aljasser@ksu...

Paediatric Audiology RHS 472 Lecture 6: Diagnosing Hearing Disorders in Infants and Children Behavioural Hearing Tests for Infants and Children Part Two: Visual Reinforcement Audiometry (VRA) Dr Arwa AlJasser Email: [email protected] Paediatric Audiology RHS 472 Objectives of Behavioural Tests lectures To introduce you to the main tests available to audiologists for assessing the hearing of infants and young children. To promote understanding of the approaches to hearing assessment in infants Intended Learning Outcomes On completion of these sessions, and with further reading, you should be able to: Demonstrate understanding of the main behavioural tests used to assess hearing in preschool children Paediatric Audiology RHS 472 Directed reading BSA recommended procedure Visual Reinforcement Audiometry (2014) Madell, J and Flexer, C. (2013). Pediatric audiology; diagnosis, technology and management. Thieme medical publisher. Chapters 6,7,8 and 9 McCormick (Editor): Paediatric Audiology 0-5 years. 3rd Edition, Whurr 2004. Chapter 3 Paediatric Audiology RHS 472 Behavioural tests of hearing sensitivity 0 – 6 months: Behavioural observation audiometry (BOA) 6 – 12 months: Distraction test 6 – 36 months: Visual Reinforcement Audiometry (VRA) 30 – 36+ months: Play audiometry Paediatric Audiology RHS 472 Visual Reinforcement Audiometry (VRA) (6-36 months) Widely used in hospital based clinics: test of choice (key behavioural test) for 6-36mth age group. Based on principle that child will turn to a sound (or tactile) stimulus involuntarily but this response is reinforced in order for it to be repeated, using a visual reward. Essence of VRA is to reinforce an observable behavioural response (usually a head turn) to sounds with a visual reward. Once association established between auditory stimulus and visual reward, classical conditioning has taken place. Once you know the child has been conditioned you can then try and find thresholds by only rewarding child for accurate head turns (operant conditioning). Paediatric Audiology RHS 472 VRA (6-36 months) Test environment, set-up and equipment  The test should be performed in a room that is of adequate size to accommodate parent(s), child and two testers comfortably.  The room should have adequate ventilation and air conditioning for patient comfort; babies who are uncomfortable are less likely to respond well to testing.  The room should offer minimal distraction to the child.  The table should have a soft, wipeable surface to keep noise down to a minimum when engaging with the child, yet is still compliant with infection control procedures.  A variety of test room arrangements can be employed for VRA. However, the preferred test equipment and set-up uses two testers and two rooms. Paediatric Audiology RHS 472 VRA (6-36 months) Test environment, set-up and equipment (cont.)  In this preferred test protocol, control of stimuli and reward are operated from a second (observation) room by Tester 1 while Tester 2 engages the child.  Such an arrangement allows for discreet communication/instructions to the tester controlling the child’s attention, reduces the potential for distraction, and allows for optimum (frontal) observation of the child’s behavioural responses.  The test and observation room should be separated by a one-way window such that the child is not distracted, yet allowing the observer (Tester 1) a clear view of the child and ideally of the engager (Tester 2) as well.  This arrangement is also more useful for training purposes and for allowing other family members to observe the test discretely. Paediatric Audiology RHS 472 VRA (6-36 months) Test environment, set-up and equipment (cont.)  There should also be the facility for the Tester 1 to hear sounds made in the room (for communication and appropriate timing of stimulus).  The arrangement also allows Tester 1 to present live speech to the patient through the sound-field speakers, via a microphone with presentation level controlled by the audiometer intensity attenuator.  In exceptional circumstances, there may be a need to move Tester 2 away (e.g. when the child is shy). In these cases, particular attention must be paid to instructions to parents remaining in the test room with the child. Paediatric Audiology RHS 472 VRA (6-36 months) Recommended room layout. Note Tester 1 is positioned to one side of Tester 2 to allow for direct line of sight of the subject. Reinforcer cabinets (and/or reward monitors) should be readily moveable Paediatric Audiology RHS 472 VRA (6-36 months) One (Single) room setup (Both testers in the same room) -same principles applied. Using monitor screen linked to camera in the front of the child to observe him and tester 2 as well Tester 1 should not be visible to the child Paediatric Audiology RHS 472 VRA (6-36 months) Type of reinforcement: illuminated and animated toys  Reinforcers should be located within a moveable cabinet obscured by smoked Perspex (solid transparent plastic) screen such that the toys are not visually attractive without illumination.  A switch in the observation room should control animation and bright illumination of the toys.  Ideally, at least two independently controllable toys should be provided for each side of testing to vary the reward. Reinforcer can be puppets, pictures or lights Paediatric Audiology RHS 472 VRA (6-36 months) Positioning of the loudspeakers  Loudspeakers shall be positioned at 90° azimuth relative to the test position to each side(reference equivalent threshold sound pressure levels, RETSPLs, are only available for these angles of presentation)  Loudspeakers shall be at least 1 m from, the test position to each side.  The speakers should be approximately level with the child’s head; such positioning provides the most efficient means for conditioning the behaviour and establishing MRL. Paediatric Audiology RHS 472 VRA (6-36 months) Position of reinforcers  Reinforcers should be positioned as close to 90° as possible; 90° azimuth is used in order to elicit the clearest head turn.  The reinforcers should be located approximately level with the child’s head at a distance of 1−2 m.  Close proximity between speaker and reinforcer is preferred in order to aid conditioning when using soundfield stimuli; so in practice adjacent positioning of loudspeaker and reinforcers is recommended.  Facility should exist to move the reinforcers closer to the child to enhance reinforcement (if their developmental and/or visual ability requires this) although care should be taken to avoid interfering with the calibrated soundfield of the loudspeaker.  Reinforcers positioned to both sides allows children to be rewarded on their preferred side (e.g. useful when testing through insert earphones or through bone conduction). Paediatric Audiology RHS 472 VRA (6-36 months) Positioning of child and tester  A younger infant (age 5–12 months) should be seated on the parent’s knee, gently supported at the waist and facing forward. Alternatively, the infant may be placed in a secure ‘high chair’. An older child can be seated on a low chair, with parent seated on the opposite side to reinforcement, and slightly behind.  The child should be at a point determined and marked during calibration of the sound-field.  A table is placed in front of the child to provide a surface for the engaging activity. Paediatric Audiology RHS 472 VRA (6-36 months) Positioning of child and tester (cont.)  Tester 2 is positioned on the opposite of the table facing the child with a supply of suitable toys close at hand adequate for the duration of the assessment.  The table should be at a height comfortable for the child to see (and if required reach).  If a child is not developmentally ready for full head turn to a reinforcer at 90°, it may be appropriate to change the angle of position of the reinforcer to achieve a lesser angle (possibly in association with a reduced distance) from the child. Care should be taken to ensure that the calibration position is not compromised when sound-field testing (e.g. avoid moving the reinforcer in front of the speakers). Paediatric Audiology RHS 472 VRA (6-36 months) Position of tester in observation room  Tester 1 should have a clear view of the child’s face and Tester 2’s activity.  The audiometer, reinforcer control box and recording materials should be within easy reach. Communication between testers  Good two-way communication between testers is essential requirement for the test.  Communication from Tester 1 to Tester 2 should be direct and discreet so as to avoid auditory distractions for the subject, for example the use of a wirefree system. Paediatric Audiology RHS 472 VRA (6-36 months) Hearing protection Remember, when using soundfield stimuli some of the sound levels used may be uncomfortable and for this reason also hearing protection (muffs and /or plugs) shall be available for parents and observers as well as testers. Need to use ear protection for tester and parents with a suspected severe/profound loss. Paediatric Audiology RHS 472 VRA (6-36 months) Stimuli Stimulus type Vary the stimulus to keep interest, warble tones and narrow band noise (NBN). pure tones (not when using soundfield as pure tones create standing waves, which alter sound intensity within the sound field), Paediatric Audiology RHS 472 VRA (6-36 months) Stimuli Stimulus type (cont.)  Note conventional NBN is considerably less frequency specific than warble tones and can lead to the substantial under-estimation of hearing loss in people with steeply sloping hearing loss. Therefore, care should be taken in use of conventional NBN where it is suspected that the patient has a steep audiometric slope or results suggest this. Alternative NBN that is more frequency specific and provides more accurate estimation of thresholds with steeply sloping hearing loss may be available on some audiometers. (FRESH noise, pediatric noise) NBN calibration  NBN Should be calibrated in dB HL not dB effective masking level (to avoid under- estimating hearing loss by 5–10 dB).  Also note that Reference equivalent threshold sound pressure levels (RETSPL) for calibrating NBN in dB HL are available for presentation in the sound-field only but not via other transducers Paediatric Audiology RHS 472 VRA (6-36 months) Stimuli Stimulus type (cont.) So  Typically used sound stimuli are frequency modulated warble tones (centred on 0.5, 1 2, 4 kHz)  If FRESH noise available then preferred  while NBN are used for (“attention grabbing”).  Speech stimuli (Live voice or recorded) can also be used.  Sometimes broad band stimulus is used as first signal like /∫/ or child’s name. However, it must be calibrated.  pure tones with insert or supra-aural earphones Paediatric Audiology RHS 472 VRA (6-36 months) Stimuli Stimulus delivery A range of transducers should be available for use: speakers for sound-field presentation insert earphones (e.g. EAR3A coupled with immittance tip, foam tip or earmould), supra-aural earphones (e.g. TDH39/49), and a bone vibrator. For children with hearing aids, where available, insert tips should be inserted into the tubing of their ear-moulds, as this will be useful for prescribing amplification. cross-infection control  Manufacturer’s guidelines must be followed and local advice be sought regarding best practices for cross-infection control when using supra-aural headphones or bone vibrators.  While if insert ear phones are used, disposable single-use tips should be used and be available for different ear canal sizes. Paediatric Audiology RHS 472 VRA (6-36 months) Stimuli Stimulus delivery (cont.)  There are advantages and disadvantages/limitations related to each method of stimulus delivery; e.g.: supra-aural and insert earphones. Supra-aural earphones (rest on the ear and have traditionally been used for a-c audiometry. supra- aural earphones can be cumbersome, particularly when used for masking bone conduction thresholds, and may cause the ear canal to collapse. Insert earphones use a disposable foam tip for directing the sound straight into the ear canal and therefore prevent the ear canal from collapsing. Paediatric Audiology RHS 472 VRA (6-36 months) Stimuli Stimulus delivery (cont.) Insert earphones are also associated with less transcranial transmission (interaural attenuation) of sound than supra-aural earphones so reduce the need for masking. (Remember, Interaural attenuation varies considerably from person to person. It is also earphone dependent. When using insert earphones, the transcranial transmission loss is higher than when using when using supra-aural, with a minimum transcranial transmission loss of 55 dB if the earphones are inserted correctly (Munro and Agnew, 1999). The situation with b-c is very much worse, and there can be little or no transcranial transmission loss.) However, insert earphones may not be appropriate in ears with infections, obstructions or abnormalities. In cases of excessive wax, insert earphones could also push the wax further into the canal and therefore must be avoided. Paediatric Audiology RHS 472 VRA (6-36 months) Test procedure Subject preparation  Parent(s) and child are brought into the room, seated and introductions made. History taking provides an opportunity for the child to settle in an unfamiliar environment and for the audiologist to make some preliminary observations about the child.  It is advisable to ask at the beginning about the level of alertness of the child and if this is likely to change during the consultation in order to determine the best point of time of testing. If the child is becoming restless it may be appropriate to cut the history short and begin testing. Paediatric Audiology RHS 472 VRA (6-36 months) Test procedure Subject preparation (cont.) Information should be obtained about the child’s developmental and visual status before starting the test. If there is any doubt about the child’s ability to respond in the desired manner (i.e. with a head-turn) this can be discussed with the parent. If necessary, head control and turning can be checked by having the child visually track an object of interest through an arc of 180°. It is important to advise the parents about the best way to hold / support the child. The test procedure is explained to the parent with suitable cautions about cueing the child to the presence of an auditory stimulus, and the need to minimize distracting noise. Care shall be taken when positioning parent and child to ensure that sound-field calibration (if relevant) is not compromised. Paediatric Audiology RHS 472 VRA (6-36 months) Test procedure Subject preparation (cont.) The transducer should be fitted to the child. The fitting of insert earphones should be preceded by otoscopy. Tester 2 should be alert to ensure that the conductor remains appropriately placed throughout the test procedure. Paediatric Audiology RHS 472 VRA (6-36 months) Test procedure Procedure for measurement of minimum response levels Initiation of test and role of Tester 2 Tester 2 will choose a suitable table-top activity (e.g. playing with small toys). The toys selected and manner employed will be the minimum necessary to encourage the child to adopt a midline forward position (for head position in relation to the calibrated sound-field system) and maintain alertness (in order to be ready to respond when the acoustic signal is presented). Very young children who have not yet reached the developmental level of object permanence should therefore require coverage of the object. Importantly Tester 2 shall provide no change in activity linked to stimulus presentation that could serve as a cue for signal presentation. Tester 2 should avoid noisy play, so as not to mask the signal, and refrain from engaging with the child too fully. Paediatric Audiology RHS 472 VRA (6-36 months) Test procedure Procedure for measurement of minimum response levels (cont.) VRA in principle: Stage 1 (conditioning): Sound + visual reward = head turn [classical conditioning] THEN: Stage 2 (testing): Sound = head turn reinforced by visual stim. [operant conditioning] Sound = NO head turn NO reinforcement No sound + a head turn? Paediatric Audiology RHS 472 parent loudspeaker loudspeaker baby Low Visual table Visual reinforcer reinforcer Audiologist (distractor) Test room Observation room audiometer Audiologist (tester) VR control box Paediatric Audiology RHS 472 Paediatric Audiology RHS 472 Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Conditioning Before testing it is essential to establish conditioning. Some children will give a clear and repeatable head-turn to an auditory stimulus without any formal conditioning while others will require a number of conditioning trials. The following sequence is suggested: 1. A 2-kHz stimulus is presented at a level judged adequately suprathreshold. As a guide, 60–70 dB HL is suitable for routine purposes, although consideration should be given to the type and degree of hearing impairment anticipated. Also, a different frequency may be selected if it is judged that the child is likely to be more responsive (e.g. a lower initial frequency would be appropriate if there is suspicion that the child has a high-frequency hearing loss). Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Conditioning (cont.) 2- If the child gives a clear head turn within 2–3 seconds of the stimulus presentation then visual reinforcement is provided in combination with the sound for a further 2–3 seconds. If repeatable, conditioning can be considered to be established and the test sequence begins. 3-. If the child does not respond spontaneously with a head turn, a more formal conditioning procedure is needed. Initially stimulus and reward are presented simultaneously and if necessary the child’s attention directed towards the reward. A number of such paired presentations may be required. When a head turn response is reliably elicited to the combined stimulus conditioning is checked by presenting the auditory signal alone and presenting the visual stimulus as a reward after the head turn response. Once the child is responding to sound alone testing can begin. Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Conditioning (cont.) 4. If the child responds to the combined stimulus/reward but fails to demonstrate a response to the stimulus alone it may be that the stimulus is insufficiently interesting or is not audible. The assumption should be that it is not audible and the presentation level increased (e.g. by 10 dB). If no response is observed at this higher level then differentiation between interest/inaudibility can be assessed by changing the stimulus type (e.g. to NBN) or changing the frequency of the stimulus. Using a vibrotactile stimulus generated from the bone vibrator (such as around 40 dB HL at 250 Hz) with reconditioning using the paired presentation should show a response even in a deaf child. If the tone is still inaudible at 80 dB HL, then care shall be taken to increase the level of the tone in 5-dB steps until a response is observed, while continuing to monitor the child for discomfort (e.g. blinking, crying). Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Conditioning (cont.) 4. If the child is not responding to the stimulus/reward combination it may be that the reward is insufficiently visible or interesting. This may be remedied by lowering the room lighting, changing the reward, using two or more rewards in combination or moving the visual reward closer to the child. Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Conditioning (cont.) Alternatively it may be that the child is not developmentally ready for the procedure or is not sufficiently motivated by the reward in which case other test procedures will be required. Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Testing When conditioning is secure (at least two consecutive correct responses), Tester 1 will proceed to the test trials proper.  Here sound only will be presented for 2–3 seconds.  If Tester 1 judges that the child has turned in response to the sound, then visual reinforcement will be presented for 1–2 seconds, with overlap of the stimulus in order to continue a clear association between the two. Response  The desired response is a clear head-turn to view the reinforcer.  Eye glances or small movements should be interpreted with more caution and be reported as such.  False ‘checking’ responses will be managed by using variable inter-trial intervals, some of long duration, and additionally use of deliberate no-sound control trials may be employed.  Withholding the visual reinforcer for a moment or two after the child turns also may help to distinguish checking glances, which are often shortlived, from real responses. Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Testing (cont.)  Once responses have been established to the initial high level, the level should be dropped as rapidly as possible (e.g. 20-dB steps) as long as responses are still observed.  Tester 1 should determine presentation level based upon age of the child, attention state, and other factors concerned with time. However, around the estimated MRL, a ’10-dB down, 5-dB up’ rule should be adopted.  The criterion for minimal response level will be the lowest level at which a response occurs at least 2 out of 3 of ascending trials (i.e. >50 %). Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Testing (cont.)  False positive responses should be discounted from judgment against the criterion defining a MRL.  Minimum response level at one frequency should be defined before moving to another frequency where possible.  The initial and subsequent test frequencies will vary for each patient, depending on the information obtained by previous methods and the need to acquire further information. When changing stimulus frequency, present the initial stimulus at a level judged to be at or above threshold of the new frequency. It may also be helpful to present clear supra-threshold stimuli or re-condition a child who has become distracted.  Where ear-specific information is sought, insert ear phones should be used. This could be achieved for one or more frequencies in each ear following sound-field VRA. Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Testing (cont.) In instances where the child rejects the inserts, or has reduced interest/awareness, the child’s localisation ability for NBN or voice (supra-threshold, up to 30 dB above the minimal response level) may be assessed, using both low and high frequency NBN. It may be necessary to recondition the child using loudspeakers on both sides. Difficulty with localisation may indicate an asymmetric hearing loss, and may warrant the need for testing each ear individually using insert earphones. An ability to localise successfully, however does not exclude the possibility of an asymmetric loss. Therefore, where medical or parental history indicates the need to investigate for an asymmetric hearing loss, then ear-specific information should be the goal. Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Testing (cont.) Selection of frequencies for testing, will depend upon the profile of information previously obtained on the child and that required for further management. Aim to get min. response levels established at 0.5, 1, 2, 4 kHz, using up/down procedure. The sequence of assessment should be adapted depending on the objectives of the audiologist and the status of the child. However, the testers must be aware that the cooperation/interest of the child may fail at any time and this should be reflected in the sequence of assessment: the clinically more important information should be obtained first. As a guide the following sequences are suggested for an initial formal behavioural assessment commencing with stimuli presented in the sound-field: 2 kHz → 500 Hz → 4 kHz → 1 kHz or 1 kHz → 4 kHz → 500 Hz → 2 kHz Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Testing (cont.) Sound-field testing could be followed by delivery of stimuli through insert earphones where ear specific information will be of use (e.g. where the possibility of significant asymmetry is indicated by the history) or where results will be used to guide amplification. Likewise, BC testing may be indicated, with awareness of increased likelihood of vibrotactile responses at the lower frequencies compared to adults Paediatric Audiology RHS 472 VRA (6-36 months) Procedure for measurement of minimum response levels (cont.) Testing (cont.) The timescale for acquisition of MRLs should be considered carefully. On the basis that quality of results takes prominence over quantity (of MRLs) consideration should be given to arranging a sequence of appointments. This is particularly important where a large quantity of information is required and/or where the child is only just at sufficient developmental age or has relevant disabilities. A duration of 30 minutes would be typical for an assessment appointment that included sound-field VRA. Paediatric Audiology RHS 472 VRA (6-36 months) Interpretation of results The process described above provides calibration to adult norms for a conventional audiometric technique. There are no specific international standards on the RETSPL values for stimuli used for VRA. Audiologists should be mindful of the influence of age of subject and the test method employed when interpreting and reporting results. Consideration should also be given to the use of MRL information, whether to inform others (e.g. ENT medical colleagues) of hearing status or for use by the Audiologist to guide effective amplification to a prescriptive target. Paediatric Audiology RHS 472 VRA (6-36 months) Interpretation of results (cont.) There are numerous factors contributing to the known difference between infant VRA MRLs and adult normative thresholds. These include sensory and nonsensory factors (including ear canal size) and other factors such as the effects of subject generated noise. The effect of these contributory elements is complex and not fully understood. However, the sum of these effects is that normally hearing infants performing VRA require a higher intensity stimulus to induce a response (e.g. a head turn) than that required for normally hearing adults performing pure-tone audiometry. Paediatric Audiology RHS 472 VRA (6-36 months) Interpretation of results (cont.) Although some studies have investigated and reported on the difference between MRLs obtained by VRA in infants and adult threshold normative data, the data set (relating to test frequency, age of subject and type of transducer) is far from complete. Further studies are required to confirm and build upon this knowledge base before we can endorse a series of specific correction factors for VRA (as is the case for auditory brainstem response testing of newborn babies). Paediatric Audiology RHS 472 VRA (6-36 months) Interpretation of results (cont.) With due consideration of the above, the materials presented below represent current information on the scale of infant-adult correction factors based upon the mode of stimulus delivery, stimulus type and age. Consequently, the correction values indicated are provisional at this time. Sound field testing 7-12 months ( approximately +10 dB relative to adult thresholds ( 0.5 to 4 kHz) Insert earphone Frequency- specific correction factors should be considered in 8-11 months infants 15 at 500 and 1000 Hz 5 at 2000 and 4000 Hz Paediatric Audiology RHS 472 VRA (6-36 months) Interpretation of results (cont.) These values should be subtracted from the MRLs to provide estimation for threshold level For example, MRL of 30 dB HL at 500 Hz using inserts will be considered as 30- 15= 15 dB HL However, as such studies have only been carried out on normally hearing infants, it is possible that these correction factors do not apply to children with sensorineural hearing impairment. In addition clinicians should be aware that there are no studies that investigate such MRLs in older children yet. Care should be taken in reporting results to other professionals who may be more familiar with interpreting thresholds rather than MRLs. Paediatric Audiology RHS 472 VRA (6-36 months) Interpretation of results (cont.) The records and reporting of results should be clearly accompanied by a description of the type of transducer, and any comments on the reliability of responses or factors preventing completion of the test. Also each audiogram record should indicate whether recorded levels are MRL or corrected to provide estimated adult thresholds. Bone conduction No studies have been identified that provide correction factors between bone conduction VRA MRLs and sound-field thresholds in dB HL. In view of this, it is important to label results appropriately where BC MRLs are presented alongside corrected AC MRLs. Paediatric Audiology RHS 472 VRA (6-36 months) Tips for effective VRA testing  The procedure relies on continued cooperation of the child, in particular their ability to stay in the required test position and to maintain interest; time will therefore be limited. To avoid delay/disruptions ensure that all required equipment is checked in advance (Stage A calibration checks are completed, reward system operating and communications equipment ready for immediate use WILL BE DISCUSSED AT THE END OF this LECTURE ).  Some children may be upset by certain animated toys. If so, reward through simple illumination rather than animation or switch to alternative toys.  To extend interest in responding, switch reward toys and/or use in combination. Also be prepared to take a break from testing and return to complete the assessment, or switch testers. The interest of older children in particular may be extended by praise/encouragement of correct head turn, provided by Tester 2.  Towards the end of the test procedure, return to the first frequency tested and present at MRL (or 5 dB above that dial level); does the child still respond? This information will help the tester judge reliability of later responses. Paediatric Audiology RHS 472 VRA (6-36 months) VRA: common pitfalls Inadequate test set-up and communication between testers Attempting to condition to subthreshold (below threshold) stimuli Not establishing clear responses during conditioning before proceeding to test trials Counting a checking response as a true response Parents cue the child Too little or too much activity by distractor with the child Overemphasis on quantity of data rather than quality Inefficient use of time Paediatric Audiology RHS 472 Calibration  Always and for any test stimuli presented through headphones, bone vibrator or insert-earphones shall be calibrated in accordance with the relevant international standards, preferably in dB HL in order to present a unified documentation of the audiogram.  Calibration of stimuli presented in the sound-field by loudspeakers is less straightforward. Sound-field calibration requires a considerable knowledge of the use and limitations of sound level meters and sound-field acoustics. Most test environments do not provide the ideal anechoic condition and a number of measures have to be taken to ensure that the sound level delivered to a child’s ear is accurate and stable. It is recommended that expert help be sought from centres with experience in this field. Paediatric Audiology RHS 472 Calibration (cont.) So calibration stages for subjective tests in audiology clinics should include 1. Full calibration initially when installing a new equipment and annually against the standards (Stage B) (done by experts). 2. A daily visual examination and listening checks shall be carried out in order to check the audiometer is functioning across the range (Stage A check) (done by a clinician with sufficiently good hearing to detect any faults). 3. Calibration should be carried out when any major changes are made (e.g. to room layout) or changes in external noise levels occur. The test environment should be clearly documented with a defined layout of furniture, furnishings, equipment and positions for people in the room during testing; marks should be provided to floors and ceilings to ensure that layout and positions remain consistent as any deviation may compromise calibration. Paediatric Audiology RHS 472 Calibration (cont.) Stage A check: routine checking and subjective tests The following tests 1 to 8 should be carried out daily with additional checks of reinforcers and between-room communication systems. Such checks are particularly important for VRA given the variety of stimuli and transducers typically employed and routing of signals between rooms often via additional cable connections. Where apparent faults are noted, equipment shall not be used until correct performance has been confirmed. 1. Clean and examine the audiometer and all accessories. Check earphone cushions, plugs, main leads and accessory leads for signs of wear or damage. Any badly worn or damaged parts should be replaced. If any transducers are replaced, then the audiometer must undergo a Stage B check. Paediatric Audiology RHS 472 Calibration (cont.) Stage A check: routine checking and subjective tests 2. Switch on equipment and leave for the recommended warm-up time. (If no warm-up period is quoted by the manufacturer, allow 5 minutes for circuits to stabilise.) Carry out any setting-up adjustments as specified by the manufacturer. On battery-powered equipment, check battery state using the specified method. Check that earphone and bone vibrator serial numbers tally with those on the instrument’s calibration certificate. An instrument’s transducers shall not be changed unless a full Stage B calibration is undertaken. 3. Check that the audiometer output is approximately correct on both air and bone conduction by sweeping through at a hearing level of just audible tones (e.g. 10 dB HL or 15 dB HL). This test should be performed at all appropriate frequencies and for both earphones and the bone vibrator. Paediatric Audiology RHS 472 Calibration (cont.) Stage A check: routine checking and subjective tests (cont.) 4. Check that the masking noise is approximately correct at all frequencies through both earphones, at a level of 60 dB HL. 5. Perform a high-level listening check on air and bone conduction at all frequencies used, on all appropriate functions and on both earphones (e.g. 60 dB HL for air conduction, 40 dB HL for bone conduction). Listen for proper functioning, absence of distortion, freedom from clicks when presenting the tone etc. 6. Check all earphones and the bone vibrator for absence of distortion and intermittency; check plugs and leads for intermittency. 7. Check that all the switches are secure and that lights and indicators work correctly. 8. Check that the subject response button works correctly. It is also recommended to weekly perform an audiogram on a known subject, and check for significant deviation from previous audiograms (e.g. 10 dB or greater). Paediatric Audiology RHS 472 Thank you