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Introduction to Amplification and Aural Rehabilitation > Impression taking and earmoulds > Flashcards

Impression taking and earmoulds Flashcards

1
Q

What is the function of the earmould?

A

-Delivers the sound from the hearing aid to the ear in an acoustically appropriate way
-Keeps the hearing aid in place
-Modifies the frequency response of the hearing aid system according to the shape, style and acoustic options used within the earmould

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2
Q

What are the characteristics of a good earmould? (6)

A
  1. Comfortable- so that the hearing aid user can wear their hearing aid all day if they wish
  2. Snug fit- to prevent feedback or reduction in sound quality and keep the earmould in place
  3. Easy to insert and remove- especially for older patients with dexterity problems or arthritis
  4. Non-irritant- some people are allergic to acrylic or silicone which are commonly used to make earmoulds
  5. Cosmetically acceptable- can affect willingness of hearing aid wearer to wear the hearing instrument
  6. Fit-for-purpose- suitable for the individual and their type/ degree of hearing loss
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3
Q

Which anatomical parts of the outer ear need to be filled during impression taking?

A

-The impression material will initially fill the ear canal
-Then need to ensure that the concha of the pinna is sufficiently filled
-Also need to fill the fold of the anti-helix to ensure the manufacturer has enough detailed anatomical information

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4
Q

How long is the external auditory meatus in adults?

A

2.5 cm

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5
Q

How deep into the ear canal should the otostop be placed ideally?

A

1 cm deep into the ear canal

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6
Q

What is an alternative to the syringe in impression-taking?

A

-Impression taking gun which uses replaceable cartilages that contain the impression material so manual mixing is not required
-Can be difficult to manipulate but the advantage is that a new canula is used with every patient so there is high level of infection control and hygiene

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7
Q

Why may an open jaw impression be more suitable than a closed jaw impression?

A

-Some people present with problems of their hearing aid(s) whistling when they are eating, talking, chewing or swallowing
-Open jaw impression may lead to an improved acoustic seal

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8
Q

What are the advantages of open jaw impressions?

A

-Provides largest ear canal volume (best acoustic seal)
-Resulting moulds/ ITEs are secure
-Useful for fitting instruments that require high gain
-Suitable for completely-in-the-canal (CIC) aids
-Useful when patient has had previous retention problems

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9
Q

What are the disadvantages of open jaw impressions?

A

-Softer earmould materials such as silicone need to be used to get a comfortable and tight fit
-Hard acrylic is not suitable
-May be more costly and limiting

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10
Q

What questions should be asked when examining and critically evaluating an impression?

A

-Is the meatal portion of the impression long enough?
-Is it in contact with the otostop?
-Did any impression material pass the otostop?
-Is there good representation of skin texture on the surface of the earmould?
-Are there folds or bubbles?
-Is there uniform colour?
-Has the concha been over-filled?

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11
Q

What are the key characteristics of a good impression?

A
  1. Meatal depth sufficient
  2. Cotton tails along meatal floor
  3. Well positioned otostop (no material has escaped beyond it)
  4. Full helix (gone up into the fold of the antihelix)
  5. Good overlap and full concha
  6. No surface imperfections i.e. cracks, splits, air pockets
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12
Q

Explain why this image shows an example of a poor impression

A

-Otostop is not sitting flush against meatus of impression
-Not enough material used- under-filled concha
-Surface imperfections i.e. cracks, splits, air pockets

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13
Q

What are the contraindications to impression taking?

A
  1. Immediate post-operative period (2-3 weeks, probably under 2 months is risky)
  2. Excessive wax (can push the wax closer to the tympanic membrane)
  3. Foreign bodies (can push them further)
  4. Outer or middle ear infections, discharge, bleeding, inflammation (hygiene and infection control purposes)
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14
Q

What are some special considerations to impression taking?

A
  1. Perforated eardrum (impression material could go through the perforation)
  2. Stenosis (narrowing of the ear canal- otostop should be selected with care)
  3. Mastoid cavity (may need to use more than one otostop to ensure no impression material reaches the middle ear or becomes stuck in the mastoid cavity)
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15
Q

What do open fit earpieces consist of?

A

Microtube and silicone dome

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16
Q

What is the microtube made of?

A

Hard plastic

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17
Q

What is a problem associated with thin tubes?

A

-Retention
-Some microtubes have a retainer which sits in the concha and improves retention

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18
Q

What are some advantages of using microtubes and silicone domes?

A

-Variety of standardised tube lengths and replaceable silicone domes allow instant fitting
-Reduces the occlusion effect
-Improved cosmetic appearance compared to standard earmoulds

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19
Q

What are some disadvantages of using microtubes and silicone domes?

A

-High potential for feedback
-Can be easily blocked with wax so need regular cleaning

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20
Q

What kind of earmould is this image depicting? Which areas of the ear does it fill? What are some of its advantages?

A

-Full shell earmould
-Fills the concha and into the helix of the ear
-Provides an effective seal to reduce the likelihood of feedback
-Sturdy and lightweight
-Suitable for moderate to high power BTE hearing aids

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21
Q

What kind of earmould is this image depicting? Which areas of the ear does it fill? What are some of its advantages? Who is it not recommended for?

A

-Half shell mould
-Covers the helix area
-Easy to insert and remove
-Not recommended for severe to profound hearing losses as sound may escape and cause feedback

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22
Q

What kind of earmould is this image depicting? Which areas of the ear does it fill?

A

-Three quarter (3/4) shell mould
-Shell mould with the helix tip removed for easier insertion

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23
Q

What kind of earmould is this image depicting? Which areas of the ear does it fill? What are some of its advantages?

A

-Skeleton earmould
-Shell earmould with most of the concha removed, leaving a thin projection around the concha to hold the earmould in place
-Made of acrylic
-Designed to be inconspicuous and lightweight
-Provides good retention
-Easy to insert
-For mild to moderate hearing losses
-Commonly used

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24
Q

What kind of earmould is this image depicting? Which areas of the ear does it fill? What are some of its advantages?

A

-Open earmould
-An acrylic framework with no meatal projection, allowing an open ear canal
-Similar to an open fitting eartip
-Good retention
-Canal portion is finished with material to the length of the tube
-Good for mild hearing losses

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25
Q

What kind of earmould is this image depicting? What are some of its advantages? Who is it not recommended for?

A

-Canal earmould
-One of the smallest earmoulds available
-Comfortable
-Cosmetically appealing
-Suitable for ears with abnormalities of the concha
-Also improves ease of insertion
-Risks poor retention of the earmould
-Not recommended for severe or profound hearing losses due to the potential for feedack

26
Q

What kind of earmould is this image depicting? What are some of its advantages? Who is it not recommended for?

A

-Canal lock earmould
-Like a canal earmould but with an added protrusion in the concha for improved retention
-Not recommended for severe to profound hearing losses due to the potential for feedback

27
Q

What do RIC earmoulds consist of?

A

-Receiver joined to the hearing aid using a thin electrical wire coated in plastic
-Silicone domes or custom earmoulds are available in different sizes to allow variable levels of occlusion and fitting a variety of ear canal sizes
-Standardised wire lengths and replaceable silicone domes allow instant fitting
-Increased gain is available as the receiver is close to the tympanic membrane
-Reduced risk of feedback as the receiver is further away from the BTE microphone

28
Q

What kind of earmould is this image depicting? Which areas of the ear does it fill?

A

-RIC open earmould
-Custom fitted canal mould that is hollow and made to accomodate RIC products

29
Q

What kind of earmould is this image depicting? What are some of its advantages?

A

-RIC closed earmould
-Similar to the open RIC earmould but has a closed canal tip
-Provides more occlusion
-Provides more gain at the low frequencies

30
Q

What modification can be carried out to RIC closed earmoulds to allow more flexibility in acoustic fitting?

A

Drilling in of small vents

31
Q

What kind of earmould is this image depicting? What are some of its advantages and what kind of hearing aids is it most commonly used in?

A

-Receiver or solid earmould
-Made of hard acrylic and has a steel ring in the centre of the earmould face
-The hearing aid receiver attaches onto the ring
-Small cavity underneath the ring and clip leads to a sound outlet that passes through the earmould and delivers the sound to the ear
-Provides an effective seal to reduce the likelihood of feedback
-Sturdy
-Most commonly used with body worn hearing aids

32
Q

Which parts of the ear are important for impression taking?

A

-Earmould should sit between the tragus and anti-tragus
-Fill the concha
-Reach up into the cymba-concha

33
Q

Describe where each part of the ear mould sits in the ear (or should)

A
  1. The helix lock sits in the cymba concha
  2. The concha rim is seated within the concha itself and underneath the ridge around the concha
  3. The inter-tragal ridge sits between the tragus and the anti-tragus
34
Q

Which frequency does the natural resonance of the ear canal show a peak?

A

Between 2-4 kHz in people with normal ear anatomy

35
Q

What are the three earmould modifications affecting the frequency response of the ear?

A
  1. Vents
  2. Filters/ dampers
  3. Horns
36
Q

What effect does venting have in general?

A

-Vents allow low-frequency signals to escape
-Used when hearing is normal in the low frequencies
-Can improve sound quality
-Also allows aeration of the external ear which prevents moisture/ condensation in the ear mould and allows pressure relief

37
Q

What are the three vent types and how do they differ from each other?

A
  1. Parallel vent: vent drilled in parallel to the sound bore, most preferable and comes in different sizes
  2. Diagonal vent: used for small ear canals, joins with the sound bore, may increase risk of feedback
  3. External vent: channel passes along the side of the mould meatus, preferable to diagonal vent as does not disturb bore, sometimes can get blocked as the ear canal moves
38
Q

How does vent diameter affect the frequency response of the hearing aid?

A

As vent size increases there is a decrease in the low frequency gain

39
Q

What are the disadvantages of vents?

A

-Allow sound to escape from the hearing aid which can cause feedback especially if the vent is large
-Can be challenging to fit into the mould especially for smaller ears

40
Q

What effect do filters/ dampers have in general?

A

Used to smooth out resonant peaks introduced by earhook or tubing

41
Q

Which frequencies do filters/ dampers primarily effect?

A

Between 750-3000Hz

42
Q

What are the factors affecting the severity of the filter?

A

-The location of the filter in the hook or tubing
-The greatest attenuation will occur when the filter is placed closest to the sound output
-Greater damping for placement near the top of the earhook

43
Q

What are the disadvantages of filters/ dampers?

A

-Can be challenging to select the correct filter and most appropriate placement in the earmould tubing system
-Sometimes removed by hearing aid wearers from the hook of the hearing aid who assume they shouldn’t be there

44
Q

What effect do horns have in general?

A

-Changes the diameter of the sound bore in order to enhance/ reduce high frequency components
-For downward sloping hearing losses (e.g. presbycusis), it is difficult to obtain the necessary amount of gain

45
Q

Which frequencies do horns primarily effect?

A

Above 2000Hz

46
Q

What is the most common type of horn used?

A

Libby horn

47
Q

What happens as size of the final aperture of the Libby horn is increased?

A

Greater increase in the higher frequencies

48
Q

What are the disadvantages of earmould horns?

A

-Can be challenging to fit into the mould especially for smaller ears
-Can be perceived as affecting the appearance of the hearing aid

49
Q

What is the occlusion effect?

A

-Occurs when an object fills the outer portion of a person’s ear canal
-Bone-conducted sound vibrations are reflected back towards the eardrum
-This boosts low frequencies (below 500 Hz) in the ear canal by 20 dB
-Causes own voice to sound hollow or booming echo-like

50
Q

What are two solutions for the occlusion effect?

A
  1. Venting the earmould- allows sounds to escape, however sometimes causes feedback and is not suitable for people with severe to profound hearing loss
  2. Increasing the length of the meatal tip past the second bend (acoustic seal area)- prevents the vibrations from occurring but can make the earmould more difficult to insert
51
Q

How does the degree of hearing loss affect earmould selection?

A

-The greater the hearing loss the larger the earmould needs to be to reduce the chance of feedback
-Accuracy of earmould impression is very important if maximum amplification needs to be high without feedback

52
Q

What modifications can be made for older patients or patients with dexterity problems?

A

-Smooth earmould materials can be used to prevent patients with thin skin from getting insertion abrasions
-Tapering the end of the canal may make insertion easier but increases chance of feedback
-Removing or reducing the helix lock can make insertion easier

53
Q

What are the 4 physical properties that earmould materials can differ on?

A
  1. Degree of softness: the lower the shore value the softer the material. Hard acrylic has the highest shore value and silicone has the lowest.
  2. Finishing characteristics: whether the material is easy to modify once the earmould has been made, whether the surface is smooth or tacky, whether it causes abrasions on the skin
  3. Extent of shrinkage: ideally an earmould will shrink very little over time since shrinkage can allow sound leakage and cause feedback
  4. Discolouration: whether the earmould discolours over time can affect acceptance
54
Q

What are the advantages of acrylic/ lucite?

A

-Very hard so possible to make thin ridges
-Keeps shape without shrinkage
-Easy to modify
-Easy to insert/ remove
-Fairly hypoallergic

55
Q

What are the disadvantages of acylic/ lucite?

A

-Will not bend or compress to get past narrow openings on insertion
-More prone to feedback
-Not usually recommended for children (danger of ear injury if struck)

56
Q

Is acrylic a hard or soft material?

A

-Acrylic can hard or soft
-However soft acrylic is not as soft as silicone
-Hard and soft can be combined in one earmould (tip- soft, rest-hard)

57
Q

What are the advantages of polyvinyl chloride?

A

-Softer and more comfortable than acrylic
-Appropriate for children
-Appropriate for hearing losses in the moderate to severe range
-Although not as slick as acrylic, not as tacky as silicone (reasonably easy to insert)

58
Q

What are the disadvantages of polyvinyl chloride?

A

-Not very durable
-Soft nature makes modification more difficult than acrylic
-Prone to discoloration over time
-Problematic for people with vinyl allergies

59
Q

What are the advantages of silicone?

A

-Soft and tacky nature makes silicone ideal for severe to profound hearing losses
-Appropriate for chldren
-Fairly hypoallergenic

60
Q

What are the disadvantages of silicone?

A

-Soft nature makes modification more difficult than acrylic
-Soft and tacky nature makes it the most difficult to insert and remove
-Can cause skin abrasions in patients with fragile skin
-Tubing adhesive does not bond well so may need mechanical tubing lock

Introduction to Amplification and Aural Rehabilitation (9 decks)

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