TENS Under the Hood: Intensity Automation

06/17/2020 • Shai Gozani M.D., Ph.D.

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This is the fifth in a series of posts that explore how TENS devices work.  Our intention is to go “under the hood” of these useful pain relief devices to help you understand their operation.  We explore key technical specifications and operating principles.  We hope this information is valuable when deciding on a TENS device for your particular needs.

Our topic today covers automation, which means the automatic handling of operations that would otherwise be undertaken by humans.  A contemporary example is home automation like the Nest® smart thermostat.  Medical devices are increasingly adopting automation technology to enhance performance and improve safety.  Examples include robotic surgery and computer aided mammography.

Automation can make TENS devices easier and more effective.  There are several aspects of TENS therapy that can benefit from automation.  We will focus on control of stimulation intensity, which was discussed in our third post (TENS Under the Hood: Intensity Control) and is the most important TENS parameter for achieving pain relief.  Read on to learn about intensity automation.

Variation in Optimal Intensity

The stimulation intensity that is optimal for pain relief effectiveness and comfort is generally not constant.  It can change during the course of a typical 30 to 60-minute therapy session and over the course of the day and night.  At the start of a therapy session, the intensity is increased to a “strong but comfortable” level within a minute or two.  During a therapy session, the intensity should be intermittingly increased to counter nerve desensitization, a process whereby nerves become less responsive to stimulation over time.  In the absence of this periodic adjustment, pain relief may be reduced.  The intensity may require further modifications to account for changes in body position during a therapy session to maintain comfortable stimulation.

If therapy extends over hours or days, as in wearable TENS applications, then further tuning may be necessary.  Nerve sensitivity changes during the day, usually following a circadian rhythm.  In some individuals, the same stimulation intensity feels stronger in the morning or afternoon compared to other times of the day.  Stimulation during sleep, which may be helpful in controlling overnight pain, may require a lower stimulation intensity to avoid disturbing sleep.

Automatic Control of Intensity

In a typical TENS device, the user must manually adjust the intensity to maintain an optimal level of nerve stimulation.  This requires constant vigilance and regular interaction with the TENS device, which complicates use and may lead to sub-optimal pain relief.  Quell® has Autopilot™ technology that automatically controls the stimulation intensity based on the user’s physiological characteristics and preferences.  Like cruise control on your car, this technology automatically manages stimulation intensity, while allowing the user to take manual control at any time.

Given the obvious value of automatic intensity control, why is it not widely available in TENS devices?  The reason is that this technology is complex and requires sophisticated software algorithms and sensors that are only found in Quell.

If you would like to read more posts in the TENS Under the Hood series, please click here.

©2020 NeuroMetrix, Inc. All Rights Reserved.

About The Author
Shai Gozani M.D., Ph.D.

Dr. Gozani is an expert in non-invasive neurostimulation. He received his M.D. degree from Harvard Medical School and the Harvard-MIT Division of Health Science and Technology. Dr. Gozani earned his Ph.D. in Neurobiology, M.S. in Electrical Engineering & Computer Science and B.A. in Computer Science from the University of California at Berkeley. Following his studies, Dr. Gozani conducted post-doctoral research at Harvard Medical School and MIT. He holds 36 U.S. patents and has authored over 30 articles in scientific and clinical peer-reviewed journals. Dr. Gozani is founder, president and CEO of NeuroMetrix, Inc.; which designs and manufactures Quell.

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