Cochlear Implants
by Sara Duran

Clinical Programing Series: Pulse Width

October 7, 2024
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  • Approximately 5 minutes to read
  • Learning objectives:
    • Understand how pulse width affects loudness
    • Understand when changing pulse width is recommended
    • Understand the effects of changing pulse width

What is pulse width?

Each stimulation pulse delivered by the implant consists of two phases that have an equal negative and positive charge phase separated by a smaller interphase gap. These pulses are charge-balanced, making them safe for electrical stimulation of neural tissue.  Pulse width is the duration of each phase, measured in microseconds, and refers to the amount of time the pulse is on (Figure 1). Charge, or the area under the pulse waveform, is what determines the loudness for patients and is the product of the pulse width times the stimulus amplitude. Therefore, loudness can be increased by either increasing the stimulus amplitude or increasing the pulse width.

When is changing pulse width indicated?

In most cases, the default pulse width will result in enough range for C levels to be set to loud. However, in some cases increasing the C profile enough to reach appropriate loudness may result in some channels being out of compliance (OOC). This means that further increases in current amplitude won’t result in additional current delivery or loudness growth. A research study simulated this effect by clipping the upper limit of stimulation and measuring its impact on speech recognition2. The study found that small amounts of clipping (15%) can significantly reduce speech perception in background noise, and larger amounts (30%) can lead to significantly poorer outcomes in both quiet and noisy environments.

Custom Sound® Pro software automatically detects out of compliance channels during programming and prompts the clinician to increase pulse width of the map (Figure 2). If the clinician agrees, the pulse width is widened automatically on all channels, and the map T and C levels are automatically reduced to maintain comfortable stimulation and the map profile. Maintaining a uniform pulse width across the entire map is recommended to permit the use of global adjustments.

What effects will changing pulse width have on stimulation?

If pulse width was increased due to electrodes being out of compliance, this will likely restore adequate loudness growth necessary for maximizing patients’ speech understanding.2

Secondly, research shows that widening pulse width can result in narrower spread of excitation3. This is also why increasing pulse width can be beneficial in cases of facial nerve stimulation.

Lastly, since stimulation parameters like pulse width, stimulation rate, and maxima are interconnected, changing one may require changes to the others. Our maxima default is 8 and we recommend keeping this and reducing the rate before reducing the maxima below 8.  Custom Sound® Pro software manages these parameter dependencies by only permitting the selection of compatible combinations.  For instance, when using perimodiolar electrodes with default settings of 900 Hz per channel, 8 maxima, and a 25 µs pulse width, the pulse width can be increased to 50 µs without needing other adjustments. However, if the pulse width is increased to 100 us, the rate must be reduced to 500 Hz per channel to allow sufficient time for the longer pulses to be delivered.

Key takeaways:

  1. Loudness is determined by charge and can be increased by either increasing the current level or widening the pulse width.
  2. Increasing loudness by widening pulse width can control current spread3.
  3. Widening the pulse width if prompted by the software will keep the system in compliance. NOTE: adjustment to the stimulation rate may be required

The “Cochlear Implant Reference Guide” is available within the Help menu of Custom Sound Pro® for further reading on programing principles and terminology.

  1. Z43470 ISS3 Nucleus Technical Reference Manual 
  2. Saoji AA, Adkins WJ, Olund AP, Nelson-Bakkum ER, Koka K. Effect of exceeding compliance voltage on speech perception in cochlear implants. Hear Res. 2021;400:108112. doi:10.1016/j.heares.2020.108112
  3. Zhou N, Zhu Z, Dong L, Galvin JJ 3rd. Effect of pulse phase duration on forward masking and spread of excitation in cochlear implant listeners. PLoS One. 2020;15(7):e0236179. Published 2020 Jul 20. doi:10.1371/journal.pone.0236179

Related Posts
Science Spotlight

Science Spotlight: Speech perception and QoL effectiveness CI in a group of adults 65 years or older

January 19, 2021

Hearing and Quality-of-Life Outcomes After Cochlear Implantation in Adult Hearing Aid Users 65 Years or Older

A Secondary Analysis of a Nonrandomized Clinical Trial

Wick CC, Kallogjeri D, McJunkin JL, et al

Assessment of Cochlear Implants for Adult Medicare Beneficiaries Aged 65 Years or Older Who Meet Expanded Indications of Open-Set Sentence Recognition

A Multicenter Nonrandomized Clinical Trial

Zwolan TA, Kallogjeri D, Firszt JB, Buchman CA

Purpose

To explore speech perception and quality-of-life (QoL) effectiveness of cochlear implants (CI) in a group of adults 65 years or older compared with an optimized bilateral hearing aid (HA) condition, and to examine the improvement on the AzBio Sentence Test for Medicare beneficiaries who meet the expanded criteria of a score of 41% – 60% in the best-aided condition.

Key messages

Cochlear implantation is a safe and effective treatment for hearing loss in adults age 65+ who meet both traditional1 and expanded2 Medicare guidelines. Results show significant and meaningful improvements in speech perception and quality-of-life, without an elevated risk profile in this population.

Methods

Wick et al.

  • Non-randomized controlled trial, multicenter, prospective, repeated measures design
  • 13 clinical sites
  • 70 subjects age 65 years and older with postlinguistic onset of bilateral moderate sloping to profound sensorineural hearing loss with an aided CNC word score of ≤40% in the ear to be implanted and ≤50% in the contralateral ear. Note that Wick et al. is a secondary analysis of subjects age ≥65yrs who are part of the larger dataset found in Buchman et al.

All subjects were experienced users of hearing aids and completed objective speech perception testing and subjective QoL surveys prior to implantation. All enrolled subjects were implanted with a CI532 electrode and used a Nucleus® 7 Sound Processor on the implanted ear and a new ReSound hearing aid on the contralateral ear. Subjects were seen by their clinicians at 1m, 3m, 6m and 12m post-activation, with endpoint measurements collected at the 6m visit. Subjects also completed a post-operative high-resolution CT scan to confirm electrode placement.

Zwolan et al.

  • Non-randomized, multicenter, prospective clinical trial
  • 8 clinical sites
  • 34 subjects age 65+ years with bilateral moderate to profound hearing loss and best-aided pre-operative AzBio Sentence Test scores of 41-60%. Note that the current CMS criteria require a score of 40% or poorer.

The study examined speech recognition, telephone communication, hearing device benefit, health utility and quality-of-life in a group of Medicare beneficiaries. Assessments were performed pre-operatively, and at 6m and 12m post-cochlear implantation.  

Results

Wick and colleagues found that CIs provided meaningful improvement in speech perception and QoL in a population of 70 subjects who were age 65+ years at the time of implantation. The subjects demonstrated an estimated marginal mean (EMM) improvement in CNC words scores of 44.1% in the implanted ear alone, and 32.7% in the bimodal condition (CI+HA). Individually, 83% of subjects showed an improvement of 15% or more in the bimodal condition. On AzBio Sentences at +10dB SNR, the EMM score improved by 24.5% in the implanted ear alone and by 21.6% in the bimodal condition (Figure 1).

The Total score on the Speech, Spatial, and Qualities of Sound survey (SSQ49) improved from a baseline score of 2.04 to score 4.97 at 6 months post-CI – a difference of 2.93 points on a 10-point scale. On the Health Utilities Index (possible score range of 0-1.0), the average pre-operative hearing score was low (0.298 with bilateral HAs) and increased to 0.605 after 6 months of using a CI and HA together (change of 0.307). At this 6-month endpoint, 94% of the subjects reported that they were satisfied with their everyday listening condition, compared with only 9% of subjects who were satisfied pre-operatively when using two well-fit HAs.

In addition to the objective and subjective benefit of CI seen in this cohort, the surgery was generally well tolerated with no major adverse events within these first six months. All reported adverse events were minor, and typically associated with a CI, suggesting that this age group of recipients do not seem to present at higher risk for complication when comorbidities are appreciated and managed pre-operatively.

In agreement with the Wick article, Zwolan et al. reported similar speech perception benefits in a group of 31 subjects age 65+ years. The group in this study is further defined by their pre-operative scores of 41-60% on AzBio sentences which is better than the currently approved Medicare guideline. On CNC words, the EMM increased by 43% in the implanted ear alone, and by 36.5% in the best aided condition at six months post-implantation. On AzBio Sentences in quiet, the group demonstrated an EMM increase of 42.4% in the CI alone condition and 32.3% in the best-aided condition (Figure 2). The subjects’ reports of perceived hearing and health benefit also reflected significant and clinically meaningful improvement after receiving a CI.

Conclusions

The results of these two clinical trials of participants ≥ 65 years found clinically important speech understanding improvements in quiet and noise, and notable QoL and hearing satisfaction benefits when using a CI or a CI+HA versus using bilateral HAs. The advantages were seen in subjects who meet the current CMS indication for cochlear implantation, as well as in those who exceed it by as much as 20%. Complications and adverse events were neither major nor prolonged, indicating the risk/benefit profile to be acceptable for this age group. These findings suggest that cochlear implantation in older adults could be extended to those with better pre-operative speech understanding and could contribute to a healthy aging process.

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References

Buchman CA, Herzog JA, McJunkin JL, et al. Assessment of Speech Understanding After Cochlear Implantation in Adult Hearing Aid Users: A Nonrandomized Controlled Trial. JAMA Otolaryngol Head Neck Surg. Published online August 27, 2020. doi:10.1001/jamaoto.2020.1584

Citation:

  1. Wick CC, Kallogjeri D, McJunkin JL, et al. Hearing and Quality-of-Life Outcomes After Cochlear Implantation in Adult Hearing Aid Users 65 Years or Older: A Secondary Analysis of a Nonrandomized Clinical Trial. JAMA Otolaryngol Head Neck Surg. Published online August 27, 2020. doi:10.1001/jamaoto.2020.1585
  2. Zwolan TA, Kallogjeri D, Firszt JB, Buchman CA. Assessment of Cochlear Implants for Adult Medicare Beneficiaries Aged 65 Years or Older Who Meet Expanded Indications of Open-Set Sentence Recognition: A Multicenter Nonrandomized Clinical Trial. JAMA Otolaryngol Head Neck Surg. Published online August 27, 2020. doi:10.1001/jamaoto.2020.2286

Authors & Affiliations:

Department of Otolaryngology–Head and Neck Surgery, Washington University School of Medicine in St Louis, St Louis, Missouri

Cameron C. Wick, MD (1)

Dorina Kallogjeri, MD, MPH (1,2)

Jonathan L. McJunkin, MD (1)

Nedim Durakovic, MD (1)

Laura K. Holden, AuD (1)

Jacques A. Herzog, MD (1)

Jill B. Firszt, PhD (1,2)

Craig A. Buchman, MD (1,2)

Statistics Editor, JAMA Otolaryngology–Head & Neck Surgery

Dorina Kallogjeri, MD, MPH (1,2)

Department of Otolaryngology-Head and Neck Surgery, Michigan Medicine, Ann Arbor

Teresa A. Zwolan, PhD (2)

This article is intended to serve as a resource for clinicians to help keep up to date with current clinical literature and is intended for professionals only. Clinical literature is based on research, which may include the experimental use of new or currently available products and technologies. Therefore, literature presented on this blog may represent use of Cochlear products that does not align with the intended use or indications approved by regulatory bodies, also known as off-label use. Cochlear does not condone any off-label use of its products, and it is not Cochlear’s intent to promote off-label use by providing this blog as a resource to clinicians.

This content is meant for professional use. If you are a consumer, please seek advice from your health professional about treatments for hearing loss. Outcomes may vary, and your health professional will advise you about the factors which could affect your outcome. Always read the instructions for use. Not all products are available in all countries. Please contact your local Cochlear representative for product information. Views expressed are those of the individual. Consult your health professional to determine if you are a candidate for Cochlear technology.

All figures are our own.

For compatibility information and devices visit www.Cochlear.com/compatibility and resound.com/compatibility. For a list of compatible ReSound hearing aids visit www.Cochlear.com/nucleus/compatibility

cochlear next

Cochlear NEXT CI532 Clinical Study Insights – Is Hearing Preservation Possible with CI532?

October 14, 2019

In the spring of this year, sixty-five otology and audiology professionals came together for Cochlear NEXT – a program focused on learning and discussing Cochlear’s CI532 Clinical Study and the respective implications of this emerging and impactful data.

The following information reviews the primary talking points and output from the day’s third and final topic of hearing preservation. You can also find available video recordings of Cochlear NEXT sessions on our YouTube channel.

Is Hearing Preservation Possible with CI532?

Presenters:
• Ryan Lopez, Group Product Leader, Nucleus® Cochlear™ Implants, Cochlear Americas
• Brian Kaplan, MD, Surgeon and Global Head of Clinical Innovation, Cochlear Americas
• David Kelsall, MD, Surgeon and CI532 Investigator, Rocky Mountain Ear Center

While not designed as a hearing preservation study, CI532 study data offers insights regarding the ability to preserve hearing using the CI532 Slim Modiolar electrode. But how is hearing preservation defined, and what other characteristics beyond electrode design play a role in patient outcomes in this regard?

During this session, NEXT participants were exposed to new, intriguing data that supports the use of CI532 in hearing preservation cases, while anecdotal discussion allowed surgeons to share their own experience preserving measurable hearing with this electrode.

Recent perspectives on hearing preservation vary in terms of how hearing preservation is defined – does hearing preservation refer to measurable hearing, or to functional hearing? Something aid-able? During a live poll, the audience overwhelmingly responded that ‘Preserving functional hearing to improve outcomes’ is the most appropriate description. Likewise, on pre and post-event surveys, the group overall agreed that functional hearing preservation should only be considered when a patient’s pre-operative low-frequency pure tone average (PTA) is better than 65dB.

Building on the consensus of defining hearing preservation, the discussion moved into which electrode design factors impact preservation, and how the CI532 Slim Modiolar array compares versus previous generation perimodiolar and lateral wall arrays – dispelling a common misconception that the CI532 will not preserve residual hearing.

Electrode Design Factors for Preservation1

The ability of CI532 to preserve functional hearing (defined for this presentation as PTA ≤ 80dB at 250 Hz and 500 Hz) was illustrated by examining the published literature, the CI532 multi-center clinical study, and the experience at Rocky Mountain Ear Center (RMEC). Overall the three data sets produced highly consistent results across 215 patients total, with 34-40% maintaining PTA ≤ 80dB at initial activation2,3,4. Looking specifically at CI532 subjects and patients of RMEC, more than 70% of patients maintained measurable thresholds at initial activation 1,4 – this despite patients not being ‘traditional’ hearing preservation candidates.

Additional discussion centered around the divergent factors affecting hearing preservation and performance – whether biological, technological, or environmental. Leading into the discussion, participants had agreed (as measured on pre-event survey) that hearing preservation is NOT the factor that has the greatest impact on hearing performance. This perspective remained largely the same following the discussion and presentation.

Conclusion

Cochlear NEXT presented a unique opportunity to bring together diverse thought and experience to address common questions regarding hearing performance – what is the impact of placement on performance, are we implementing the correct clinical measures pre- and post-implantation, and is hearing preservation possible with the CI532 Slim Modiolar electrode?

Learnings from Cochlear NEXT demonstrate that across the variability of patients we serve, biological factors are as important and impactful, if not more so, than the technology alone. Further, data collected prior to, during and after the program indicates that while there is some movement toward consensus on these issues, there will continue to be different perspectives among professionals across the continuum of care. However, that also provides opportunity for emerging insights, renewed debate, and evolving solutions to maximize patient outcomes and ensure access to a lifetime of hearing.

Check out our new YouTube playlist featuring video highlights of session topics including CI532 Study Surgical and Clinical Outcomes.


References

  1. Sweeney A, Hunter J, Carlson M, Rivas A, Bennett M, Gifford R, Noble J, Haynes D, Labadie R, Wanna G. Durability of Hearing Preservation after Cochlear Implantation with Conventional-Length Electrodes and Scala Tympani Insertion. Otolaryngol Head Neck Surg. 2016 May;154(5):907-13. doi: 10.1177/0194599816630545. Epub 2016 Feb 23
  2. Preliminary Data on File: US Multicenter CI532 Study. 2018.
  3. Friedmann et al. Surgical Experience and Early Outcomes With a Slim Perimodiolar Electrode. NYU Cochlear Implant Center. Otology & Neurotology 2019
  4. Data on file: Rocky Mountain Ear Center, 2019.
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This material is intended for health professionals. If you are a consumer, please seek advice from your health professional about treatments for hearing loss. Outcomes may vary, and your health professional will advise you about the factors which could affect your outcome. Always read the instructions for use. Not all products are available in all countries. Please contact your local Cochlear representative for product information.

 

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