Cochlear Implants
by Sara Duran

Clinical Programing Series: Pulse Width

October 7, 2024
Share
  • 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
man and grandkids outside

5 tools to expand your knowledge on the Slim Modiolar Electrode

December 4, 2019

1. Cochlear NEXT Video Series

In Spring 2019, sixty-five of your peers came together to discuss Cochlear’s CI532 Clinical Study and the implications of this emerging and impactful data.

The Cochlear NEXT video series captures the highlights of the day’s presentations with a focus on the surgical and clinical outcomes of the CI532 Clinical Study. It also discusses opportunities for hearing preservation with the Slim Modiolar electrode.

2. Audiology Online Course: Setting a New Benchmark with the Slim Modiolar Electrode

Did you miss Audiology Online’s webinar on the recent clinical evidence surrounding the Slim Modiolar electrode and its impact on performance? Watch the course now!

After attending this course you’ll be able to:

  • Explain the clinical evidence supporting the use and performance of perimodiolar electrode arrays
  • List audiological considerations with the Slim Modiolar array
  • Understand the outcomes of the new multicenter trial and bimodal benefits of the Nucleus® 7 system with Slim Modiolar

3. Educational Webinar: CI532 Best Practices – A Surgeon’s Perspective

Join NYU’s Dr. Thomas Roland in his March 2019 webinar as he discusses his experiences and best practices with the CI532 Slim Modiolar Electrode.

Topics include:

  • NYU surgical and speech performance outcomes
  • Surgical best practices
  • Case management
  • When to use CI532

4. TECH TALK: The CI532 Slim Modiolar Electrode Advantage

Dr. Anil Lalwani, Vice Chair of Research in Otolaryngology, Head, Neck and Surgery at Columbia University Medical Center, prefers the Slim Modiolar electrode above the rest.

In this TECH Talk, he outlines the many advantages to the Slim Modiolar Electrode including its small size, proximity to the modiolus and atraumatic properties. Further, his experience demonstrates that the Slim Modiolar electrode may preserve hearing and protects the electrode through the sheath function, preventing chances of getting stuck. Because the Slim Modiolar minimizes variation in surgical technique and chances of intracochlear trauma, it takes the lead as the safer option with a focus on patient outcomes.1

Watch now:

5. Journal Club: Speech recognition as a function of the number of channels in perimodiolar electrode recipients

This Journal Club explores a recent study by the team at Vanderbilt University Medical Center in a March 2019 publication, Speech recognition as a function of the number of channels in perimodiolar electrode recipients. This study revealed that increasing the number of electrodes resulted in improved performance and sound quality. Findings were statistically significant in demonstrating that the subjects with the electrodes closest to the modiolus had the best performance.

Want to see more? Subscribe to our ProNews Blog using the panel to the left to ensure you receive new blog post notifications!

References:

  1. Roland JT, A Model for Cochlear Implant Electrode Insertion and Force Evaluation: Results with a New Electrode Design and Insertion Technique, Laryngoscope 115: August 2005
Wilder Roberts, AuD

Including AuD students in MAPping appointments

March 9, 2022

By Wilder Roberts, Au.D., CCC-A

Wilder Roberts, AuD

Background

Emerging clinicians need experience MAPping cochlear implants as much as they need experience programming and fitting hearing aids.This includes candidacy evaluations, pre-implant counseling, activations, MAPping appointments, counseling, rehabilitation and device pairing/accessory. 

The average age of today’s audiologist is 42 years, which means these audiologists did have cochlear implant classes in graduate school and have seen the evolution of cochlear implant technology. These audiologists might have been trained by the manufacturers at the manufacturer’s facility or in regional training. Today’s students are more savvy to technology and their courses in graduate school are more in depth.

The textbooks for teaching are also improved and the course objectives directly address ASHA Standards II-A (Foundations of Practice), II-B (Prevention & Screening), II-C (Audiologic Evaluation), II-D (Counseling), II-E (Audiologic Rehabilitation Across the Lifespan) and II-F (Pediatric Audiologic (Re)habilitation). Topics specifically addressing cochlear implants range from candidacy and outcomes, to coding strategies and programming.  As with all AuD programs, course content provides the foundation and clinical opportunities provide the ability to apply course content and truly learn the software and live programming.

What opportunities are students seeking?

Students are requesting hands-on opportunities – they want to watch and observe initially and ask questions if needed. Students have a strong desire to learn, serve patients well and feel confident in services they are providing.

How can you involve students?

If you’re not currently supervising any AuD doctoral students, I urge you to consider this!  You have much to offer our budding colleagues. Obviously, the level of involvement will depend on the clinical experience your student has had. Feel free to ask them what they’ve seen, protocols with which they are familiar (they usually have copies of them) and their comfort level with cochlear implants in general.

Sample ways to include students:

  1. Students are able to prepare equipment, check it in and get your supplies ready for an appointment.
  2. Students are able to connect sound processors to cables or Wireless Programming Pods, open patient files in Custom Sound® Pro and follow a general MAPping flow. If the student is working in the software, you’re able to counsel and guide both the patient and the student seamlessly. If there’s time, allow them to practice in ‘Training Mode’.
  3. Students are great scribes, so if you’re making MAPping changes, allow them to note this for you for easy reference and documentation.
  4. Students can spend the time showing patients how to use their battery chargers, connect sound processors to smartphones, and how to connect to the Cochlear apps.

Resources

These tasks seem simple, but if we don’t give students the opportunity to practice these skills, we can’t expect them to be able to do this independently. Feel free to assign them tutorial videos prior to attempting these skills.

To assist with this, on the myCochlear website, under “CPN resources,” there is a CPN Initial activation Checklist and the student can review this. You can  choose which part the student can cover – start slow and then add to it.

If you do not use Cochlear Link, show students how to download MAPs or upload MAPs. Allow them to work with your clinic stock or better yet, have them organize and inventory your clinic stock to familiarize themselves with your system and identify parts of the sound processors.

The Bottom Line

University clinics offer background knowledge and some clinical experience. Off-campus preceptors are invaluable to the future of our profession in helping create colleagues who you are comfortable working with and referring patients. We have to pass the baton at some point, and we all want competent professionals serving our patients. Students can be an asset in your clinic and are eager to learn from your expertise.

To read more from peers, subscribe to Cochlear ProNews.

About the author: Dr. Wilder Roberts is an Assistant Professor and Cochlear Implant Program Director at the University of South Alabama in Mobile, AL.  She received her undergraduate in Deaf Education at the University of Montevallo, her Master of Science in Audiology at the University of Montevallo and her doctorate in Audiology from the University of Florida.  She has been working with cochlear implants for over 20 years in both pediatric and adult populations.  She has training in Auditory-Verbal Techniques and is a state champion for Alabama in the American Cochlear Implant Alliance (ACIA).  She has also completed Advanced Cochlear Implant Training through the Institute for Cochlear Implant Training.   Dr. Roberts is passionate about cochlear implants and increasing candidacy awareness.  Dr. Roberts is from Mobile, AL, is married and has two sons. 

For compatibility information visit www.cochlear.com/compatibility

Cochlear logo - white

©Cochlear Limited 2024. All rights reserved. ACE, Advance Off-Stylet, AOS, Ardium, AutoNRT, Autosensitivity, Baha, Baha SoftWear, BCDrive, Beam, Bring Back the Beat, Button, Carina, Cochlear, 科利耳, コクレア, 코클리어, Cochlear SoftWear, Contour, コントゥア, Contour Advance, Custom Sound, DermaLock, Freedom, Hear now. And always, Hugfit, Human Design, Hybrid, Invisible Hearing, Kanso, LowPro, MET, MP3000, myCochlear, mySmartSound, NRT, Nucleus, Osia, Outcome Focused Fitting, Off-Stylet, Piezo Power, Profile, Slimline, SmartSound, Softip, SoundArc, True Wireless, the elliptical logo, Vistafix, Whisper, WindShield and Xidium are either trademarks or registered trademarks of the Cochlear group of companies. The names of actual companies and products mentioned herein may be the trademarks of their respective owners.

 

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.

 

Cochlear ProNews is monitored Monday through Friday, excluding some holidays. Questions and inquiries submitted over the weekends or holidays may see a delay in response. For immediate assistance please contact us directly. You are solely responsible for your interactions with other members of our Websites. Cochlear reserves the right, but has no obligation, to monitor disputes or communications between you and other members of our Websites. For a full list of Cochlear’s terms of use, click here.