Practical aspects of CAEP testing with infants
The HEARLab® system has been designed to make objective audiological assessment as easy and efficient as possible. However, testing young children, regardless of the hardware and software employed, presents practical challenges.
The application of CAEPs to a paediatric population may be relatively new to mainstream clinical practice, however, the general techniques and strategies used in other areas of paediatric audiology are still highly relevant. Experienced clinicians will be well aware of how to best manage the test environment, and will have developed many of their own solutions to overcoming the issues that inevitably arise when working with infants.
The clinical validation trials of the new HEARLab® system involved repeated CAEP measures, conducted in a controlled and systematic way. This provided a valuable opportunity to investigate different approaches and test techniques, and to consider their relative merits, without the usual restrictions of a routine clinical assessment appointment, in which a diagnostic outcome must be achieved within a limited time frame.
Some general suggestions, based on observations made during the study, are summarised in this Appendix. It is hoped that this information may provide useful guidance, particularly for clinicians with less experience in paediatric audiology, or those who are new to using electrophysiological assessment techniques with young children.
Before the appointment
- Prior to the appointment, provide parents/care giver with information (written and verbal) about the procedure. This will reduce the time spent in explanation at the assessment.
- When arranging the appointment, ask about the child’s routines. Try to book the test at a time of day when the child is likely to be in a “good” mood, and less likely to be overtired and irritable. Allow plenty of time so that appointment is not rushed, and it is possible to take breaks if needed.
- Check whether the parent/care giver intends to bring sibling/s to the appointment.
- If it is necessary for siblings to attend, make sure there will be suitable activities/supervision away from the test room. The parent should be free to focus their attention on the child having the test.
- Ask the parent/care giver to bring food, drinks, or dummies (“pacifiers”) for the child, to the appointment. Some favourite toys, that are suitable as quiet distracters, can also be useful in making the child feel more secure in the test environment. DVDs that the child enjoys can also provide familiarity and useful distraction.
- Suggest that the child be dressed for the assessment in layers of clothing that can be easily removed. Electrode contact can be comprised if the child becomes overheated and “sweaty” and it may be necessary to remove clothing to cool them down. It is better not to have to pull clothes over the child’s head once they are “wired up”.
- Ask parents/care giver to ring and postpone the appointment if their child is unwell, particularly if the child has a temperature. A restless and irritable state is not conducive to quality recordings.
- Call the parent/care giver to confirm the appointment the day before, and take the opportunity to check whether they have any questions or concerns they would like to discuss.
- Make the test environment “child friendly’”. For example, decorate the test booth and surrounding areas using items such as mobiles, displays of soft toys (out of the child’s reach), and fabric motifs. Avoid hard reflective objects that will cause sound reflections. Minimise technical “clutter”. Keep wires out of view and laboratory supplies in drawers. Children, particularly if they have undergone medical treatment or hospitalisation in the past, may associate such items with unpleasant procedures.
- Keep the test area clean and tidy. A plastic backed ‘Draped’ sheet (available from medical suppliers) is a useful surface for arranging preparation materials, and for wrapping used electrodes, cotton tips etc. afterwards for disposal.
- Provide a chair that is as large enough for the child to sit comfortably, either on their parent’s lap or beside them, during testing. Some children become irritable if they feel overly restrained or restricted in their movements. Where possible, try to let them settle into a position which they prefer. A recliner chair works well as it can be used for adult testing as well.
- Use washable covers on the chair (eg, bath toweling) and change between assessments to maintain hygiene. This makes “dribbles” and food spills easier to contain and reduces parents inclination to perform immediate “clean ups”, which can disrupt the testing. Have tissues or baby wipes at hand if needed.
- Have a container on hand to collect items that require cleaning, according to infection control guidelines (eg, toys that have been in the child’s mouth).
- Some younger infants may be comfortable in a rocker/”Fraser chair”, but don’t rock the baby during recordings. “Bounces” can be evident in recordings and rocking can make a child sleepy.
- Fluorescent lighting can cause problems of electrical interference. Incandescent lighting should be used in preference. As well as providing a technical advantage, incandescent lamps can create a pleasant, relaxed ambience for children and parents. Novelty lamps (eg, artificial fish tanks, “lava” lamps), as well as providing illumination, can provide the child with visual distraction.
- It is important that the tester is able to monitor the test environment and the child’s state throughout the test. A strategically placed video camera can be extremely helpful if the arrangement of the test booth makes it difficult to maintain a clear view. A video camera that works well in low light is recommended.
- Where the tester is in a separate observation room, an audio monitor is essential in monitoring the ambient noise level in the test environment, to ensure consistent stimulus delivery, and is also useful in communicating with the distracter.
Preparation for testing
- Children generally have a short attention span, and their mood and state can change quickly. Have all test equipment switched on, checked and calibrated before the child arrives. Have the recording system software open and ready on the impedance check screen to avoid unnecessary delays.
- If testing is with hearing aids on, change the batteries and check the devices on arrival. Having another staff member do this while you are interviewing the parent will minimise delay in commencing testing.
- Ensure that the parent understands what is involved in the test. The child is more likely to be relaxed and co-operative during the assessment if their parent is confident and relaxed about what is happening.
- Make the parent comfortable. Providing a hot drink or glass of water can help put parents at ease. It is a good idea to have a safe place to put a drink beside a parent so that it cannot be knocked onto the child or electrical equipment.
- Ensure the parent feels in control of the situation. Seek their advice about the child’s preferences, and the best strategies for preparing them for testing. Respect their opinion and follow their suggestions.
- Try to build some rapport with the child. A little physical interaction with the child while you are interviewing the parent (eg, patting or stroking their arm or head) can be useful in gauging how they will react to the preparation for electrode sites, and may possibly help the child accept it more readily.
- Make sure the child’s physical needs (eg, nappy changing) are attended to before starting preparation for the electrode placement.
- Have any items that might be needed (eg, bottles, food, toys) close at hand, in order to minimise noise and disruption during testing. Check with parents to see if bottles need warming or food needs preparation before you start.
- Attempt otoscopy and tympanometry first if indicated, but don’t persevere if it causes the child to become too active or distressed.
- Ask parents to switch off mobile ‘phones or pagers as these may cause distraction to the child if they ring during testing, and may also be a potential source of electrical interference.
Preparation of electrode sites
- Attaching the electrodes is potentially the most challenging part of the test procedure. Approach the preparation confidently but not too forcefully. Smile, and talk to the child reassuringly.
- Start the preparation in a position where the child is comfortable and not overly restrained. For example, try starting while an older infant is playing on the floor, or at a child’s table and chair.
- Try not to physically “stand over” the child while doing skin preparation. Working from behind the child may be a good option. For your own health and safety, try to maintain a posture that is ergonomic and doesn’t place strain on your back or neck. Sitting on the floor beside baby whilst chatting to Mum or Dad and gently rubbing the skin can be a very non-threatening way to get the skin prepared.
- Electrode sites are generally prepared by abrading with a cotton applicator ‘bud’ and a medical gel intended for the purpose. Rub firmly and vigorously enough to cause a slight redness on the skin surface, but not so hard that the child becomes obviously distressed by the sensation. Rubbing gently, but firmly, back and forth works better than “dabbing” at the skin. Rub on the back of Mum or Dad’s hand first so they know what it feels like.
- Work as quickly as possible and minimise the number of physical contacts with the child. Don’t fuss or “overdo” it, but be mindful that it is better to prepare skin thoroughly than to have to repeat the whole process.
- If the child needs reassurance about the preparation, modelling the procedure (eg, by rubbing the forehead of the parent or a doll with a cotton bud, and sticking on an electrode) can be helpful. Try letting an older child have a “turn” at putting an electrode on a toy or on their parent.
- Some children will be reassured by watching the preparation in a mirror, but this may make others more apprehensive.
- Television can be a good distraction during electrode placement. Use a range of children’s DVDs with lots of colour and movement. If the child becomes interested, the DVD can be left playing (with the sound muted) when testing starts. This is the time to use your noisy, fun toys, before the real testing begins! Make sure you put these out of sight before you start.
- Wherever possible have a trained distractor (in addition to the parent), to interact with the child during electrode placement, as well as during testing. Toys that involve some fine motor manipulation (eg, block stacking, button pressing) can help keep hands away from the electrode sites.
- Cleaning skin with an isopropyl alcohol prep swab after abrading is sometimes recommended, and may improve contact, but it can make the electrode stick very firmly and make it difficult to remove. It can also feel “stingy” – try it on yourself if you don’t believe this! Preparation with an alcohol wipe is not needed and is not recommended for the delicate skin of infants.
Optimising and maintaining electrode contact
- Use a liberal amount of electrode paste under the vertex electrode even if a disposable electrode, that already contains conductive gel, is used.
- If using disposable electrodes, a spot of double sided tape (the type used for retaining hearing aids) on the underside of the plastic tab of the electrode stud, can give a firmer hold, particularly for mastoid or forehead sites (ie, where the skin is free of hair).
- A headband is very helpful in keeping the electrodes in place, particularly at the vertex, but some children are less accepting of wearing a headband than others.
- To make wearing a headband more appealing to the child, choose colourful, soft and stretchy materials. Give older children a choice of colours or designs (eg, have a selection of different motifs sewn on a selection of headbands). Having a choice of “girls” or ‘”boys’” styles can be important to the child, and sometimes also to the parent. Use fabrics that are easy to wash and dry after use.
- Dividing the top of the headband before use (by cutting a slit a few inches long across its centre) allows a section of fabric to be stretched forward to hold the forehead electrode in place.
- Passing the leads under the headband can help reduce pulling and strain on the electrode site during the test.
- Elastic bandage, particularly of material that allows the ends to adhere without pins or tape (eg, “peg” bandage), can be a reasonable alternative, but tends to be more “fiddly” to put on than a headband. If an inexpensive type is chosen it can also be disposed of after use which can be an advantage.
- Micropore tape (either on its own or with a headband) is appropriate for keeping re-usable type electrodes attached.
- Once the electrodes are attached, try to drape the leads behind the child, avoiding contact with the child’s face or neck. If the child can feel them, they will be more inclined to pull at them. Try to keep the leads away from clothing (eg, don’t let them become tangled in bibs or collars).
- Loosely taping the leads to the back of the child’s clothing (using micropore tape) may be helpful, but ensure they are not taped so tightly that the electrode leads are pulled off the head if the child suddenly leans forward.
- Make sure that if the parent is holding the child, that the electrode leads are not cramped or pulled under the parent’s arm. Try directing the leads up and over the parent’s shoulder.
- Avoid the child leaning back onto the electrode leads, or making sudden large movements, such as lunging forward. Strategic use of distraction toys can help in this respect.
- If the child starts to touch the leads or electrodes don’t over-react (eg, grab suddenly at the child’s hands). In preference, try to distract the child by offering them an alternative item to play with.
- Once the electrodes are in place, avoid touching them unless really necessary (ie, they are obviously slipping/becoming unstuck). Drawing the child’s attention to them will often result in renewed efforts to remove them.
- Don’t let the child overheat. This can result in electrodes lifting and the reject rate increasing. If the child gets very restless it can be better to suspend testing rather than let it proceed until they are “hot and bothered”.
- The distractor is best seated in a comfortable position at, or below, the child’s eye level. Care must be taken to maintain an appropriate position in relation to the speaker if the stimulus is presented free-field.
- Have a wide selection of age appropriate toys that are not too noisy. Keep toys and other distraction aids in easy reach, to minimise noise and disruption as the test proceeds. Choose toys that can be cleaned according to infection control procedures. Toys that can’t be cleaned (eg, soft toys) should be kept out of the child’s reach.
- For very young infants, the main aim of distraction is to keep them alert and awake (they do not have the motor skills to pull at the leads or electrodes). Mobiles, hand and finger puppets are all useful items. Visual novelties (eg, toys with lights and motion) can be excellent. Some mechanised toys are too noisy to use while the testing is in progress, but can be good to use during breaks, in order to regain a child’s interest and increase alertness.
- Toys that are used for VROA distraction are generally suitable for children in the 7-24 month age group. Examples include; stacking plastic rings or cups, farm animals, large counting and threading beads, puzzles, colourful teething rings and so on. Items that keep hands occupied are ideal for children old enough to manage them.
- For younger children or those who are not developmentally ready to “play” with items, toys with texture (eg, spiky plastic balls, plastic animals etc) can be interesting for the child to touch or mouth (make sure you put them in the “washing” container after use).
- Action toys (eg, water-wheels, small spinning tops, “pecking” birds, ‘”wobbly” animals, clear plastic balls that contain moving toys) can be useful as long as they are not too noisy. If children are allowed to hold the items they should not contain small parts that may be a choking hazard, and they must be easy to clean. Watch that water-filled toys don’t leak.
- For older infants (around 24 months and over) try colouring-in books with big colourful crayons, play-dough (if past eating it, or well supervised), paper with stickers or self-inking stamps.
- Books can be good for children of all ages. Heavy cardboard books of various shapes, or with flaps/pop-up features, can provide “hands on” activity. Books made of plastic (ie, intended for bath time) can be ideal for very young children as they are easy to clean if mouthed.
- Almost every child enjoys watching bubbles being blown. The small bottles used for parties are inexpensive and easy to use. Avoid “sticky” bubbles that are designed not to burst. They tend to leave messy residue in the test environment.
- Eating and drinking are excellent distracters. Good choices include baby bottles or infant sipping cups, and soft foods such as banana, custard, fruit gel, or sultanas. Avoid hard foods (eg, crunchy crackers) or large pieces of food of that require a lot of chewing, as the resulting noise and jaw movements can affect recordings.
- Breastfeeding is good for calming infants, but often can induce sleep. If the baby must feed during the assessment, watch very carefully and rouse the child gently if they begin to doze off, or appear their eyes start to appear “unfocused”. Be prepared to pause testing if the child’s state becomes inappropriate. Sometimes a short break to have a feed can give baby a boost to keep them going for a bit more testing.
- Avoid distraction activities that are too stimulating or that encourage increased vocalisation, for example, physically vigorous play, or games/gestures that encourage the child to answer questions or name objects. Parents may sometimes need some guidance about activities that are inappropriate in this respect.
- If the child is content and quiet it can be best for the distractor to sit quietly or withdraw and leave them to their own devices. If the child is unsettled sometimes it can help for the distracter to get right out of their view and let the parent try to settle the child before proceeding.
- Try to end the test on a ‘”happy note”, rather than persisting until the child (and potentially the parent) is distressed. This is especially important if the child will have to attend on another occasion.