Aural Rehabilitation & Hearing Aids Flashcards
Patient candidacy for hearing aid
Pts w/ HL who have communication difficulties either objectively or subjectively
- Type of hearing loss (no longer a factor)
- Degree of hearing loss: more appropriate for mod-severe HL (severe-profound may need CI)
- Word recognition: in general, pts w/ good word recognition are more likely to do better (but a low score should not preclude amplification trial)
- Age, physical and mental health of pt
- Pt’s (not family’s) motivation
- Finances
- Cosmetic considerations
- Communication needs
Pt’s subjective needs are more imp than audiogram
Factors that diminish word recognition
- Reduced audibility (the only factor H.A. can address)
- Cochlear distortions producing reduced freq and temporal selectivity and resolution
- Abnl central auditory processing
- Diminished cognitive fnc
Binaural or Monaural amplification?
Unless there is a significant asymmetry in sensitivity, tolerance to loudness, or word recognition ability, or unless a medical condition exists CI the insertion of anything in the EAC, the standard is to at least try binaural amplification
Reasons Binaural amplification is superior
- Eliminates or minimizes head shadow (reduction in signal intensity from the side of the head opposite the signal)
- Improved localization
- A central release from masking (binaural squelch) may result in better hearing in noise
- W/ binaural loudness summation, absolute binaural thresholds are 2-3 dB better than monaural thresholds
- Possibility of tinnitus reduction bc of inc stimulation to more cortical neural substrate
The dynamic range of listening is greater
CROS
Contralateral Routing Of Signal/Sound
- Usable hearing in 1 ear but no hearing, very poor, or unaidably hearing in 2nd ear
- Microphone placed on side of poorer ear
- Signal routed (via electrical cord of FM) to opposite ear and amplified
Transcranial CROS
Placing a hearing aid in the “dead” ear, producing bone conduction stimulation of the “good” ear
Only use if the poorer ear has no residual hearing that might produce recruitment or other distortion factors
BICROS
Bilateral Contralateral Routing Of Signal
essentially a CROS + conventional aid
-Use if the “good” ear is in need of amplification
-Only one ear is aidable
-Microphones are located on both ears but the signal is routed only to the “good” ear
BAHA
Bone anchored hearing aid
Used when the impaired ear is unaidable (in place of CROS)
Also used when HL doesn’t exceed 45 dB HL but traditional HA can’t be used (canal atresia)
-Titanium piece placed into the bone and allowed to integrate w/ skull for 3-6 mo prior to use
Hearing aid styles
- CIC (completely in canal)
- ITC (custom in the canal)
- ITE (custom in the ear)
- BTE (behind the ear)
- Open-fit mini BTE
- CROS
- BiCROS
- Body aids
CIC A&D
Adv
- Barely noticeable (inserted several mm into EAC terminating 5 mm from TM); removed by monofilament lying near tragal notch
- Partial resolution from occlusion effect
- Use w/ phone improved bc of deep canal location
- Wind-noise problem improved
- Gain in high freq improved due to pinna effect
- Secure fit, reduced feedback 2/2 min venting, good sound localization
Disadv:
- Only for mild-mod HL
- Fragile, freq repairs, shell modifications $$$
- More extensive counseling required to teach use
- Deep canal impressions required
- Small batteries, hard for dexterity-impaired
- FEEDBACK w/ JAW MVMT
- Can’t be used if unfavorable EACs
- Hardest to keep clean (wax blocks receiver)
- Needs digital feedback suppression technology or high feedback bc mic is close to receiver
- Fullness feeling to ear
- Distorted perception of own voice from occlusion effect
ITC A&D
Fills the cartilaginous portion of EAC
More visible than CIC
Adv:
- More cosmetic than larger HA
- Increased amplification provided by pinna boosts gain in high freq
- Placement of the microphone improves sound localization
Disadv:
- Only for mild-mod HL
- Fragile
- Hard for dexterity-impaired
- Small size limits number of controls for adjustments
- Limited venting options
ITE A&D
Fills entire concha
Adv:
- More cosmetic than BTE
- Increased amplification by pinna boosts gain in high freq
- Improved sound localization
- Made of only one component
Disadv:
- Amount of gain limited 2/2 acoustic feedback
- Only for mild, mod, mod-severe HL
- Small size limits number of controls on nonprogrammable aids
- Microphone more prone to breakdowns due to close proximity to cerumen in EAC
BTE
- parts
- A&D
2 parts
- Hearing aid hooks onto and rests behind pinna
- Custom earmold attached to tube that secures the aid and directs sound into EAC
Adv:
- Good for any degree of HL bc of power
- Best option for severe-profound HL
- Large enough for multiple controls for electroacoustic properties, allowing adjustment flexibility
- Less feedback bc mic and receiver further apart –> larger venting and more amplification for severe to profound losses
- Larger batteries last longer and are easier to handle
- Ideal for infants and children due to ext ear growth
Disadv:
- In pts w/ severe-profound HL, earpiece must fit tightly in the canal to eliminate feedback problems
- Require relatively nl pinna
- Easily affected by perspiration
- Less cosmetically appealing
Open fit mini BTE
Combines acoustic benefits of the larger styles with the cosmetic benefits of the smaller styles
Digital hearing aids
Computer-controlled
Digitization (incoming sounds are converted to numbers, which are then analyzed & manipulated via algorithms)
DSP (Digital signal processing - allows instruments to attempt a differentiation of noise from speech based on spectral composition and temporal characteristics)
Digital feedback reduction
