Basic Terminology of CI Programming

Question 1

What domains do we make changes?

Answer 1

Intensity
Frequency
Time
*Adjusted to the specific patient bc every one is different

Question 2

What parameters affect the signal coding in the intensity domain?

Answer 2

Stimulation levels
Amplitude
Pulse width
Electrical DR
Input DR
Sensitivity
Compression
Channel gain
Volume

Question 3

What are stimulation levels?

Answer 3

Minimum stimulation levels - least amount of stimulation a recipient can detect when electrical signal (biphasic pulses) are delivered to individual electrode contacts
Upper stimulation levels -upper limit of electrical stimulation (deal with most of the time bc this is typically where you start)
*Called something different by each manufacturer

Question 4

What is current amplitude and pulse width?

Answer 4

Amplitude is the height of the biphasic signal
Pulse width is the duration of the biphasic signal
*Can either increase amplitude or duration to increase stimulus intensity (loudness)

Question 5

How do you calculate the total energy of the stimulus?

Answer 5

(Current amplitude)(pulse width) = total charge in nanocoulombs (unit of charge)

Question 6

What is the electrical dynamic range?

Answer 6

The difference between the CI users perceptual threshold and the most comfortable level for electrical stimulation

Question 7

What parameters influence how acoustic inputs are mapped into the recipient’s electrical dynamic range?

Answer 7

Input dynamic range
Sensitivity
Compression
Channel gain
Volume control

Question 8

What is the input dynamic range?

Answer 8

Defines the range of acoustic inputs that are mapped to the users electrical dynamic range
Lower end of the IDR maps to the threshold of electrical stimulation
Upper end of the IDR maps to the maximum electrical stimulation level
Typical IDR of contemporary Ci systems ranges from 40 to 60 dB
*Acoustic stimulation fitting into the patient’s dynamic range
*In current CIs, the lower end of the IDR is usually set between 20 and 30 dB SPL, and the upper end is set between 65 and 85 dB SPL

Question 9

Will very soft sounds be completely omitted?

Answer 9

Yes, due to input dynamic range
Sound above the max stimulation level will be compressed and not omitted

Question 10

What is sensitivity?

Answer 10

Microphone gain in the sound processor
Adjusts the input signal level before frequency analysis
Works in conjunction with the IDR to shape how acoustic signals are mapped into the user’s electrical DR
Increasing sensitivity allows softer sounds to be included in the mapped input range, while decreasing it excludes lower-level sounds

Question 11

What compression system is used for CIs?

Answer 11

Automatic gain control (used by all current CI systems)

Question 12

Do all the manufacturers allow automatic gain control settings be adjusted by the clinician?

Answer 12

No, only AB and Med-El
Nucleus systems use a specialized input processor called ASC (Adaptive Sound Control), which acts like a slow-acting compressor for moderate to high-level input noise
Nucleus also applies additional compression for moderate-to-high inputs that exceed the upper limit of the IDR

Question 13

What is involved at mapping acoustic inputs into the the electrical dynamic range?

Answer 13

Channel gain - controls the amplification provided to the signal in a channel specific (frequency specific manner) - gain occurs prior to the processing of the signal
Volume control - a change in the volume control setting produces a change in the upper level of stimulation the recipient receives from the implant

Question 14

What parameters affect signal coding in the frequency domain?

Answer 14

Electrode contact vs channel
Virtual electrodes (current steering)
Frequency allocation

Question 15

What are the differences between the electrode contact and the channel?

Answer 15

Electrode contact - describes a physical contact in the internal device electrode array where stimulation is delivered to the auditory nerve fibers
Channel - describes a discrete frequency range over which sound is analyzed for eventual delivery to an electrode contact (channels are defined by bandpass filters); frequencies it stimulates - set by and comes from the speech processor
*frequency information is primarily conveyed by the place of stimulation within the cochlea

Question 16

Can channels match the electrode assignment?

Answer 16

Yes, or they could not
In other rare cases, the channel number and electrode number may be different
Channel to electrode assignment should be switched to restore tonotopicity
Contacts not in the correct place

Question 17

What is frequency allocation?

Answer 17

Controls how frequencies are delivered across the active channels
Can be automatically determined by the programming software or can be changed by the clinician in some softwares (cochlear and med-el)
Cochlear allows clinicians to adjust the upper frequency limit and the bandpass filters widths - allows clinicians to manually define the cut-off frequencies for each channel
Mel-El allows clincians to adjust the lower (70-350 Hz) to upper (3500-8500 Hz) frequency limits in 10 and 500 Hz steps - can choose from 4 frequency allocation tables
If an electrode is turned off, its frequencies are reallocated to the remining active electrodes
*Anatomy-based fitting

Question 18

What parameters affect signal coding in the time domain?

Answer 18

Stimulation rate - the number of biphasic pulses that are delivered to an individual electrode contact within 1 second; changes can affect pitch and loudness perception (high rates can result in a higher pitch percept and increase loudness due to temporal summation)
Total stimulation rate - overall max rate of stimulation possible across all active electrodes within 1 second; calculated by multiplying the per channel stimulation rate by the number of active channels

Question 19

What factors can influence optimal stimulation rate?

Answer 19

Varies across individuals
Varies on the basis of CI hardware - must support narrow pulse widths and high current amplitudes to achieve high stimulation rates
Electrode spacing - closer spacing and higher stimulation rates increases the risk of temporal channel interaction, which can degrade performance

Question 20

What are the theoretical benefits of high stimulation rates?

Answer 20

Improved access to fine temporal details in sound
Enhanced temporal resolution (which supports better speech understanding in noise, improved music perception and appreciation, recognition of vocal pitch, and potential for improved pitch perception)

Question 21

When spectral cues are limited, do fine temporal cues become especially important for distinguishing between similar speech sounds?

Answer 21

Yes

Question 22

What is electrode coupling strategy/stimulation mode?

Answer 22

Indicates how channels are connected to form an electrical current through which current can be delivered to the auditory nerve
Monopolar - active intracochlear electrode and an extracochlear electrode serves as the return (travels a longer distance)
Bipolar - active intracochlear electrode and a neighboring intracochlear electrode serving as the return (shorter distance = less channel interaction)

Question 23

What does monopolar stimulation provide?

Answer 23

Provides relatively broad spread of electrical current
Requires less current
Gradual change in stimulation levels from one electrode to the next (interpolation can be viable option)

Question 24

What does bipolar stimulation provide?

Answer 24

Provides relatively narrow spread of electrical current
Requires higher current/drain battery
Stimulation requirements may change drastically from one electrode to the next (interpolation is not an option and CL must measure stimulation levels for all active Els

Question 25

What is common ground coupling?

Answer 25

An electrode coupling mode used for diagnostic purposes but is not used for stimulation in contemporary signal coding strategies Electrical current is delivered to an active intracochlear electrode, and all of the remaining intracochlear electrodes serve as the collective return Most sensitive mode for detecting shorted electrodes during electrode impedance assessment (due to all of them being coupled and electrical resistance across electrodes can be referenced to an extracochlear electrode serving as the ground)

Question 26

What is sequential stimulation vs simultaneous stimulation?

Answer 26

Sequential - in most contemporary CI systems, presentation of pulses occurs one after another; reduced or prevents channel interaction Simultaneous - presentation of an electrical signal to several electrodes at one time

Question 27

What is interpolation?

Answer 27

Strategy designed to allow for quick programming within sacrificing sound quality or performance Refers to the estimation of stimulation levels on the basis of measured values from neighboring channels Example, if the measured T levels for electrodes 6 and 8 were 70 and 90, respectively, the estimated T level for electrode 7 would be 80 Measured channels are called anchor channels *clinicians should consider measuring stimulation levels when a large difference exists in the measured values of two anchor channels

Question 28

What is sweeping?

Answer 28

Refers to the sequential presentation of the programming stimulus across the active electrodes at a given stimulation level Typically performed at the upper-stimulation level and can be performed at lower

Question 29

What is the purpose of sweeping?

Answer 29

Ensure equal loudness for lower level inputs (and across electrodes) Ensure that none of the electrodes are too loud or result in unfavorable sound quality Verify that the perceived pitch is progressively higher if sweeping is performed from the apical to basal direction Identify any electrodes producing distorted or undesirable sound quality  Identify electrodes causing nonauditory side effects (e.g., facial nerve stimulation)

Question 30

What is loudness balancing?

Answer 30

Successive presentation of a programming stimulus to two or more active electrodes to ensure that they are perceived equally loud at a defined percentage of the dynamic range Typically performed near upper stimulation level (100 or 80%) Adjustments are made based on the patient's feedback

Question 31

What is the mixing ratio?

Answer 31

Controls the relative strength of the signal from the speech processor microphone and the direct auditory input (DAI) source All contemporary CI sound processors have a DAI port for the direct delivery of an external input Allows the clinician to choose from a variety of ratios ranging in a graded manner from an equal emphasis on signals from the sound processor mic and the DAI to DAI only