HESP712 > Cochlear Implant Programming > Flashcards

Cochlear Implant Programming Flashcards

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1
Q

What is the dynamic range of hearing and its relationship to the MAP?

A
  • NH: ~120 dB
  • CI: up to 20 dB
  • Acoustic to electrical transformation is determined by the MAP
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2
Q

Define MAPs.

A

-Configuration of current units (CUs), processing strategies, stimulation rate, etc.

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3
Q

Define programs.

A
  • Configuration of MAPs
  • Use of different programs
  • May be progressive over first to increase current levels
  • Similar to heading aid programs after first week/month (i.e., noise, school)
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4
Q

What would warrant an interim mapping appointment?

A
  • Changes in auditory discrimination
  • Increased request repetition
  • Addition/omission of syllables
  • Prolongation of vowels
  • Changes in vocal quality
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5
Q

What is most likely to warrant an interim mapping appointment for a child?

A
  • Prolongation of vowels

- Changes in vocal quality

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6
Q

What do you do to connect the equipment before programming?

A
  • Verify 4 components:
    1. Computerized processing unit (CPU)
    2. Implant
    3. Processor
    4. Patient
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7
Q

How do you prepare the equipment for programming?

A
  • Verify connection of components
  • Initialize processor
  • Condition electrode array
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8
Q

Describe how to initialize the processor.

A
  • For AB only
  • Dictate in the software: which ear, how it’s being used (i.e., AD, AU, bimodal)
  • Only needs to be done initially
  • May need to reset processor (for Cochlear)
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9
Q

Describe how to condition the electrode array.

A
  • For AB only

- Send stimulation to all channels at the same time

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10
Q

What measurements should be performed during programming?

A
  • Telemetry
  • Neural response assessment
  • T- levels
  • C- or M-levels
  • Speech strategies
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11
Q

What is telemetry?

A
  • Aka impedance
  • Confirms proper communication between the processor and the electrodes
  • Always performed
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12
Q

What is neural response assessment?

A
  • Electrophysiologic response from the nerve in response to electrode stimulation
  • Essentially an eABR
  • Useful for children who cannot give subjective measurements
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13
Q

What are speech encoding strategies?

A
  • Different methods of stimulation that can produce different perceptions from the patient
  • Method by which the implant translates the incoming acoustic signal into patterns of electrical pulses
  • Can be simultaneous and/or sequential
  • Provide spectral and envelope information
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14
Q

What is impedance?

A
  • Measure of the opposition to electrical current flow
  • Impedance = voltage/current
  • Reported in kOhms
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15
Q

What can cause electrode impedance?

A
  • Fibrous tissue
  • Electrolytes
  • Macrophages
  • Proteins
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16
Q

What are the stimulus parameters of electrode impedance?

A
  • Current
  • Voltage
  • Stimulus width
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17
Q

What should be checked when measuring impedances?

A
  • Do electrodes have normal impedances?
  • Have the impedances changed?
  • Impedance of deactivated electrodes
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18
Q

What could cause abnormally low impedance?

A

<1 kOhm

  • Short circuit = short electrodes
  • Likely to send stim across all channels (happens in pairs)
  • May be caused by wires touching
  • If the case, deactivate and never turn back on
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19
Q

What could cause abnormally high impedance?

A

> 30 kOhms

  • Open circuit
  • Likely a single channel
  • May be caused by: air bubble, broken wire, electrodes in contact with air
  • Can recover over time, so want to keep trying them
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20
Q

How should high impedances be addressed?

A
  • May decrease with use or by increasing pulse width
  • Initially, open circuits may be due to air bubbles in the cochlea (re-measure after stimulation)
  • Short circuits will never be activated
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21
Q

What is the electrically evoked compound action potential (ECAP)?

A
  • Gross potential that reflects synchronous firing of a large # of electrically stimulated nVIII fibers
  • Want to instruct patient to try to tolerate sounds but let the Au.D. if it’s too uncomfortable (want to look for nVII stim)
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22
Q

What is the utility of the ECAP?

A
  • Corresponds to wave I of the acoustic ABR

- Corresponds to upper limit of eDR (M or C)

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23
Q

How is Auto NRT (Cochlear) measured?

A
  • Select # channels to run (3, 5, 9, or all–usually adults: ~5; kids: ~9)
  • Click measure
  • Watch measurements and patient reaction
  • Prepare to skip channels if patient reports discomfort
  • Software will move on to another channel if stimulation reaches compliance without achieving a response
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24
Q

How is Flex NRI (AB) measured?

A
  • Select channels to stimulate (3, 7, 11, 15–avoiding basal channels)
  • Recording channel is 2 apical from stim
  • Select level of ordering (low to high if patient is conscious; high to low if patient is sedated)
  • Set min and max stim levels (-100 to 250 uV)
  • Look for 3 repetitions of response per channel (can change levels while running, skip to next data point, skip to next electrode)
  • Creates EP Growth Function
  • tNRI corresponds to M-levels
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25
How is NRI measured for MED-EL?
-It can't be measured manually
26
What is the clinical utility of NRT/NRI?
- Relatively stable over time - Used with impedances to tell if change in performance if due to device function or neural responsiveness (i.e., integrity of internal device) - Establishing a baseline for monitoring (every 6-12 months) - Establishing appropriate programming levels - Assess pitch perception at activation (i.e., same vs. different, pitch quality)
27
What is the electrically evoked stapedial reflex threshold (ESRT)?
- Electrical stimulation to implant - Measure SRT in non-implanted ear (via immittance bridge) - SRT occurs at/near max levels used by speech processor - Not recorded in 25-35% CI patients - Requires some cooperation on the part of the patient
28
How is the ESRT measured?
- Probe placed in contralateral ear - Continuously record acoustic admittance with 226 Hz probe tone - Present programming stimulus used for upper limit of DR (M-/C-levels) - Change in admittance occurs time-locked with stimulus when presentation level is of the ideal intensity for the upper limit of the DR
29
What is stimulation mode?
- Location of the reference electrode to the active electrode - Can be monopolar or bipolar
30
What is monopolar stimulation mode?
- Ground electrode is outside the cochlea - Wider spread for stim (problematic for strange anatomy) - Allows for lower thresholds (due to greater separation between ground and active) - Better battery life - More consistent thresholds for adjacent electrodes (can interpolar, don't need to measure each)
31
What is bipolar stimulation mode?
- All stimulation occurs within the cochlea | - Better when there are concerns about spread of excitation
32
What stimulation modes are available for the 3 manufacturere?
- Cochlear and AB: either monopolar or bipolar | - MED-EL: monopolar mode only
33
What is the input dynamic range (IDR)?
- CI selects the range of intensities of input to code - What we try to mimic in CI output - Want a minimum DR of 30 or 60 CUs - Number of changes that happen to signals with CIs is significantly higher than with hearing aids (why brain/adaptation is so important)
34
What are threshold levels (T-levels)?
- Ensure that speech sounds are audible - Soundfield responses to NBN should be in line with specs ( 20-25 dB for Cochlear, 30-35 dB for MED-EL & AB) - If ~10 dB HL, too much stimulation (need to lower T's to reduce stimulation)
35
What would happen if T's are too high?
- Patient might be able to hear the processor - Turn off mic and see if noise goes away - If yes, then lower T's - Want to ask what kinds of sounds are too loud
36
What would happen if T's are too low?
- Patient can't detect soft sounds (i.e. LING sounds) | - If yes, then raise T's
37
How are T-levels established for Cochlear?
- Measured manually - Set at or just above threshold - Can be obtained via: ascending, bracketing, loudness growth chart
38
How are T-levels established for AB & MED-EL?
- Interpolated based on M-levels | - Highest stim where no sound is perceived
39
What is a t-tail?
- Doesn't decrease in perceived level by patient but different in programming level - Want to set at highest stim level
40
How should T-levels be measured in pediatrics?
- May use with objective offset programming method (want threshold in at least 1 channel to see DR, then can apply DR to rest of MAP) - Can measure behaviorally via BOA, VRA, CPA in office or soundbooth (but with stim as stimulus)
41
What are some considerations for setting T-levels in tinnitus patients?
- Presence of tinnitus causes difficulties detecting stimulus during measurement (need to move quickly because there is no ambient noise to mask tinnitus when implant is off) - Multiple presentations of stim can help in perception over tinnitus
42
How should T-levels be set in tinnitus patients?
- Set T's over level of tinnitus and then decrease globally | - Loudness balancing at 50% over T's
43
What is the significance of T-levels?
- Artificially raised T's results in better performance (also preferred by participants) - Progressively louder T's, effectively reducing the DR (very little difference in performance)
44
What are comfort levels?
- Upper limit of the DR - Cochlear: set below max comfort (due to summation across electrodes) - AB: most comfortable level - MED-EL: highest stim level at which sound is loud but comfortable
45
How should M-levels be measured for AB?
- Channels are grouped by 4 - Want a flap MAP across all channels (can flatten by doing single-channel measurements) - Measure groups of 4 channels with speech bursts - Measure single channels with tone bursts
46
How should M-levels be measured for MED-EL?
- Want a flap MAP across all channels - EX: start with all even channels, then odds - EX: 6, 12, 4, 16 (alternate so no residual stim) - Measure M-levels with tone bursts
47
What are methods of measuring C- and M-levels?
- Ascending technique (w/ multiple presentations at each levels) - Loudness growth charts
48
What are some programming methods?
- Behavioral - Objective preset - Objective with behavioral offset
49
What is objective preset programming?
-Take NRIs/NRTs and have programming may you a MAP from it
50
What is objective w/ behavioral offset programming?
-Use objective preset for T's and C's/M's and then do behavioral measurements on at least 1 channel
51
What influences current levels?
- Speech processing strategies - Bipolar vs. monopolar mode - Stimulation rates - Proximity of electrode array to modiolus
52
What is the effect of stim rate on current levels?
- As rate increases, level decreases | - But doesn't preserve battery life
53
What are compliance levels?
- The amount of voltage allowed for each electrode | - Ran first thing on new or transfer patients
54
What does it mean to be "out fo compliance"?
- Maximum voltage available from the implant is not sufficient to generate the desired current level - No further perception of loudness growth - Increase pulse width or decrease stim rate - Will then need to redo entire MAP
55
What are the consequences of being out of compliance?
- Insufficient loudness growth, variable loudness, lack of loudness growth - Sound may be distorted - Poor battery life - Decreased performance in general
56
What is Automatic Pulse Width (APW)?
- AB - Optimizes PW and rate during programming - Designed to maintain the narrowest PW and fastest rate for a selected HiRes strategy - APW calculates and adjusts PW and rate based on compliance and M-level requirements - May help to determine which manufacturer to select for a patient
57
What are the two versions of APW?
- APW I: most narrow PW for fastest rates | - APW II: more compliance headroom to allow for fluctuating impedances (default)
58
What patients may benefit from APW?
- Patients whose body chemistry may change | - EX: transfusions, arthritis
59
When should manual PW be used?
- Poor sound quality - Cannot obtain adequate loudness due to nVII stim - Increase PW (decrease rate)
60
What is radio frequency (RF) transmission?
- CIs have no internal batteries - All power comes across the skin from the transmitter coil - Burden of power rests upon what power it receives from the SP - Many intermittencies and sound quality problems arise from issues that surround transmission of power (disturbances between external and internal devices)
61
What contributes to successful RF transmission?
- Flap thickness/thinness - RF power level in software - Transmitter cable length - Battery option - Compliance levels - C-levels - Rate/maxima - Listening environment/input level
62
How does flap thickness impact RF transmission?
- Thick/fat head = hard to transmit signal | - Thin skin = ex/internal device are too close together (touchy transmission)
63
What is power optimization?
- The need for power - Voltage and Power dictate the user's power level - Can the battery type provide sufficient voltage to deliver requested amount of current? - System calculated how much power is consumed by the "worst-case condition" (i.e., ambient room noise >65 dB) - Measurement done for each MAP (but only on main processor)
64
What is indicated by power optimization across the skin?
- Sufficient voltage available to the implant to ensure all electrodes remain in compliance - Sufficient power (voltage and current) for the demands of the chosen MAP
65
What is voltage impacted by?
- Skin flap thickness - T's and C's (current levels) - Impedances
66
As required voltage increases, battery life life decreases. How can this be addressed?
- Decrease pulse rate | - Want to use automatic power as much as possible
67
When should compliance and power status be checked?
- New MAP - New SP - Reported intermittences - Poor battery life - Change in sound quality - Transfer patient - >6 months since last visit - Lost/gained weight - Significant growth/shortening of hair
68
How should problems with battery life be addressed?
- Decrease rate/maxima if high stim levels or OOC conditions are not an issue - Increase PW - Move to body worn SP
69
What are some live voice modifications?
- Tilting - Increasing/decreasing levels on all channels - Gain - Frequency adjustments
70
What are some options for noise reductions?
- AGC autosensitivity - Adaptive directional range optimization (ADRO--Coclear) - BEAM: multi-microphone technology
71
What is ADRO?
- Cochlear | - Adjusts gain at each frequency band to optimize the signal
72
What is loudness balancing?
- Ensure equal loudness on all electrodes - Need to make sure the patient understands the tasks (must understand pitch vs. loudness) - Incorrect loudness balancing can be detrimental to performance - Not always necessary due to use of loudness charts (may be warranted if MAP looks funny/not balanced, or if patient is getting artifact with live voice) - Can be done via balancing or sweeping
73
What is pitch ranking?
- If the electrode array is rolled over on itself, pitch does not increase from low to high on sequential electrodes - Usually identified in post-op X-ray - Balance neighboring electrodes - Reorder channels
74
Describe counseling re: patient controls.
- Programs: microphone modes - Volumes: modifies C-levels - Sensitivity: distance of hearing
HESP712
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