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    #16
    Originally posted by niallel View Post
    Maybe start with the General Wellness category, and if that doesn't work then the exceptional use category, so we can get our hands on them before full FDA/EU approval.
    Good suggestions. Unfortunately, no matter how we slice it, these devices will be considered at least moderate risk (Class II), and the FDA is probably classifying them as De Novo (Class III, effectively higher risk because of uncertainty). General Wellness and other express lanes are for devices that are demonstrably low risk. Even if this technology is ultimately determined to be low risk, it still has to be demonstrated through clinical trials, and that's the part that takes forever.
    Co-founder & CTO of MYOLYN - FES Technology for People with Paralysis - Empowering People to Move

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      #17
      Originally posted by Matt Bellman View Post
      Good suggestions. Unfortunately, no matter how we slice it, these devices will be considered at least moderate risk (Class II), and the FDA is probably classifying them as De Novo (Class III, effectively higher risk because of uncertainty). General Wellness and other express lanes are for devices that are demonstrably low risk. Even if this technology is ultimately determined to be low risk, it still has to be demonstrated through clinical trials, and that's the part that takes forever.
      Got the name for the exceptional use wrong, its the FDA Expedited Access Pathway Program
      https://www.fda.gov/medicaldevices/d.../ucm441467.htm

      The FDA intends to notify the sponsor of its determination in writing within 30 days of receipt of a request for EAP designation.
      So it doesn't have to go through the full clinical trials if its approved for this.

      The device is more like a Class II. Other transcutaneous stimulators for pain have been classified as Class II already. Internal stimulators have been classified as Class III.

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        #18
        Originally posted by Matt Bellman View Post
        Tommy's probably referring to some of the transcutaneous designs that pass current all the way through the torso. These do require more power than your standard off-the-shelf stimulator has.
        Uh, not exactly. The human body is conductive. It's not as conductive as metals but close to the conductivity of water. For electromagnetic fields to penetrate conductors requires lower frequencies, not power. Skin depth in any conductor is inversely proportional to frequency, independent of power. More power might get you better results, but, even in that case, pulse width will be the more important parameter.
        Finally, as someone who has experienced a wide variety of stim devices, including NRT's, I can tell you it's not monstrously powerful. I have replicated the NRT electrode arrangement with other FES devices and the abdominal contraction from the NRT device is no stronger.
        T3 complete since Sept 2015.

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          #19
          Originally posted by Mize View Post
          Uh, not exactly. The human body is conductive. It's not as conductive as metals but close to the conductivity of water. For electromagnetic fields to penetrate conductors requires lower frequencies, not power. Skin depth in any conductor is inversely proportional to frequency, independent of power. More power might get you better results, but, even in that case, pulse width will be the more important parameter.
          Finally, as someone who has experienced a wide variety of stim devices, including NRT's, I can tell you it's not monstrously powerful. I have replicated the NRT electrode arrangement with other FES devices and the abdominal contraction from the NRT device is no stronger.
          Lower frequencies? The NRT device has a 30Hz frequency with a 10,000Hz carrier frequency. Would that be classified as low? I don't know, as I'm not sure how the carrier frequency would affect that classification.

          You're correct pulse width is a very important parameter. What is the pulse width of a TENS unit? I'm not trying to be antagonistic...I honestly don't know. I imagine the NRT device is capable of a much higher pulse width.

          When you say "powerful", are you referring to the amplitude of the frequency? Again, as far as I know, the NRT stimulator is capable of a higher amplitude than anything currently on the market - if I recall correctly, they have cranked it up to 180 mA with some people. What amplitude are most TENS units capable of? Again, I'm just asking because I don't know.

          The abdominal contraction from the NRT device is not indicative of the amplitude or power. I have replicated the electrode placement with other devices on myself as well, and gotten an abdominal contraction and/or lower back muscle contraction. Trunk muscle contractions are just a side effect of the main goal of the NRT and other motor-enabling transcutaneous stimulators, which is to alter the excitability of spinal neurons (not axons, but the cell bodies of neurons themselves) that current stim devices can't get to.

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            #20
            Originally posted by niallel View Post
            Got the name for the exceptional use wrong, its the FDA Expedited Access Pathway Program
            https://www.fda.gov/medicaldevices/d.../ucm441467.htm
            You're right. This technology could satisfy the criteria for the EAP program and get to market sooner. Ultimately, it comes down to risk vs. benefit and it's up to the FDA to decide.

            Originally posted by Mize View Post
            Uh, not exactly. The human body is conductive. It's not as conductive as metals but close to the conductivity of water. For electromagnetic fields to penetrate conductors requires lower frequencies, not power. Skin depth in any conductor is inversely proportional to frequency, independent of power. More power might get you better results, but, even in that case, pulse width will be the more important parameter.
            Finally, as someone who has experienced a wide variety of stim devices, including NRT's, I can tell you it's not monstrously powerful. I have replicated the NRT electrode arrangement with other FES devices and the abdominal contraction from the NRT device is no stronger.
            "Powerful" wasn't the best word choice, though it was the most colloquial. As I'm sure you know, electrical power is the product of voltage and current. In this context, the question was about whether or not a typical electrical stimulation device, as may be commonly purchased at a pharmacy or other retailer, would be able to generate voltages high enough to pass a therapeutically significant amount of current through the target tissues. Human tissue, especially skin and fat, have a high impedance, enabling alternating currents to pass through more easily than direct currents (part of why we all use alternating waveforms), so waveform and frequency do matter (though probably less than expected in this case).

            I think the most important statement here is the one based on your own experience that, under similar conditions, your body responded to the NRT device as it would have to other FES devices. What other FES device(s) did you try it with?

            An interesting side question: to what extent do you think the proprietary characteristics of the NRT device matter in terms of the ultimate outcomes being sought here? In other words, could someone get 95% of the same benefits seen with the NRT device while using an affordable, off-the-shelf stimulator that's already available? Or is it maybe only 5%?
            Co-founder & CTO of MYOLYN - FES Technology for People with Paralysis - Empowering People to Move

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              #21
              Ok, so, I don't have a dog in this fight. I'm crippled, and I expect to be, for the rest of my life, but, I do love it when these conversations go over my head. It makes me feel like smarter people than me are working to solve this puzzle. That's about as good as I could hope for, at this point.

              Keep it up.



              Originally posted by Matt Bellman View Post
              You're right. This technology could satisfy the criteria for the EAP program and get to market sooner. Ultimately, it comes down to risk vs. benefit and it's up to the FDA to decide.



              "Powerful" wasn't the best word choice, though it was the most colloquial. As I'm sure you know, electrical power is the product of voltage and current. In this context, the question was about whether or not a typical electrical stimulation device, as may be commonly purchased at a pharmacy or other retailer, would be able to generate voltages high enough to pass a therapeutically significant amount of current through the target tissues. Human tissue, especially skin and fat, have a high impedance, enabling alternating currents to pass through more easily than direct currents (part of why we all use alternating waveforms), so waveform and frequency do matter (though probably less than expected in this case).

              I think the most important statement here is the one based on your own experience that, under similar conditions, your body responded to the NRT device as it would have to other FES devices. What other FES device(s) did you try it with?

              An interesting side question: to what extent do you think the proprietary characteristics of the NRT device matter in terms of the ultimate outcomes being sought here? In other words, could someone get 95% of the same benefits seen with the NRT device while using an affordable, off-the-shelf stimulator that's already available? Or is it maybe only 5%?
              "I have great faith in fools; self-confidence my friends call it." - Edgar Allen Poe

              "If you only know your side of an issue, you know nothing." -John Stuart Mill, On Liberty

              Comment


                #22
                Tomsonite: my Genesy 1200 goes to 120 mA so 180 mA is certainly higher but not by orders of magnitude. More important to safety is mono vs bi-phasic waveforms where monophasic (asymmetric) will build up excessive charge at the anode. Also, 30/10kHz is only one mode the NRT unit is capable of.

                Matt: I doubt a drug store TENS unit can do much. A consumer FES like Genesy or Chattanooga will have some effect on some people, but my beat guess would be 10% of the effect at best as I've even managed to recreate the dual frequency approach but without the results of the NRT unit. Fortunately, once it clears the FDA (pending funding) the target MSRP is $2,500 which is in reach for many and it will have its own Medicare coding as well.
                T3 complete since Sept 2015.

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                  #23
                  Oh, also NRT are very excited to combine transcutaneous stim with this:
                  https://m.medicalxpress.com/news/201...rd-injury.html
                  T3 complete since Sept 2015.

                  Comment


                    #24
                    Originally posted by Mize View Post
                    Tomsonite: my Genesy 1200 goes to 120 mA so 180 mA is certainly higher but not by orders of magnitude. More important to safety is mono vs bi-phasic waveforms where monophasic (asymmetric) will build up excessive charge at the anode. Also, 30/10kHz is only one mode the NRT unit is capable of.

                    Matt: I doubt a drug store TENS unit can do much. A consumer FES like Genesy or Chattanooga will have some effect on some people, but my beat guess would be 10% of the effect at best as I've even managed to recreate the dual frequency approach but without the results of the NRT unit. Fortunately, once it clears the FDA (pending funding) the target MSRP is $2,500 which is in reach for many and it will have its own Medicare coding as well.
                    180 mA is not orders of magnitude higher, but as far as I'm aware, exceeds the current FDA limit on clinical stimulators (which, when I was still working in the clinic, was 140 mA I believe). In one of the original papers published by Edgerton/Gerasimenko et al, they used a monophasic waveform, which I imagine would be adjustable on their device but is certainly a safety consideration, as you point out. I know a couple of clinics that have been getting motor-enabling results with a Chattanooga stimulator, but I don't think it has been as robust as what NRT is reporting. From what I've been told, the carrier frequency they're using is what lets them increase the amplitude so high, which is one of the things that make the capabilities of their stimulator unique.

                    Originally posted by Mize View Post
                    Oh, also NRT are very excited to combine transcutaneous stim with this:
                    https://m.medicalxpress.com/news/201...rd-injury.html
                    Interesting, I haven't heard that. I do know in one of their original papers they gave a drug that acts on serotonin receptors, and that amplified the results they got vs. when they used the stimulator alone. There are many different ways to manipulate serotonin and other neuromodulatory neurotransmitters (that's what I'm currently doing my PhD on actually). My theory is that in the end, this stimulator will be best when combined with chemical neuromodulation and rehab/exercise - time will tell, of course.

                    Comment


                      #25
                      Originally posted by Mize View Post
                      Tomsonite: my Genesy 1200 goes to 120 mA so 180 mA is certainly higher but not by orders of magnitude. More important to safety is mono vs bi-phasic waveforms where monophasic (asymmetric) will build up excessive charge at the anode. Also, 30/10kHz is only one mode the NRT unit is capable of.
                      Since we're being precise with our language, monophasic, biphasic, symmetric, asymmetric...none of those characteristics matter when it comes to charge build-up. All that matters is charge balance (i.e., Coulombs in, Coulombs out), which can be achieved in many ways. For example, our stimulators use biphasic, symmetric, rectangular pulses, which is characteristically charge-balanced. RTI uses alternating monophasic pulse (rectangular, symmetric) to achieve charge balance. TENS units are usually biphasic with asymmetric phases, but the phases transfer the same total charge in and out of the tissue. Of course, this also depends on whether you're using monopolar, bipolar, or even tripolar electrode configurations...

                      Originally posted by Mize View Post
                      Matt: I doubt a drug store TENS unit can do much. A consumer FES like Genesy or Chattanooga will have some effect on some people, but my beat guess would be 10% of the effect at best as I've even managed to recreate the dual frequency approach but without the results of the NRT unit. Fortunately, once it clears the FDA (pending funding) the target MSRP is $2,500 which is in reach for many and it will have its own Medicare coding as well.
                      Interesting. I know Becca Martin at Kennedy Krieger is doing transcutaneous spinal cord stimulation in pediatric populations using an Empi 300V, and it accomplishes the same thing, though it doesn't work as well in adults because adults are physically larger, which is the thought process behind my earlier comments.

                      Originally posted by tomsonite View Post
                      180 mA is not orders of magnitude higher, but as far as I'm aware, exceeds the current FDA limit on clinical stimulators (which, when I was still working in the clinic, was 140 mA I believe). In one of the original papers published by Edgerton/Gerasimenko et al, they used a monophasic waveform, which I imagine would be adjustable on their device but is certainly a safety consideration, as you point out. I know a couple of clinics that have been getting motor-enabling results with a Chattanooga stimulator, but I don't think it has been as robust as what NRT is reporting. From what I've been told, the carrier frequency they're using is what lets them increase the amplitude so high, which is one of the things that make the capabilities of their stimulator unique.
                      Technically, the FDA doesn't specify a limit. If you're claiming substantial equivalence to a predicate device, you're limited (mostly) to what that predicate does. However, generally speaking, the FDA follows the muscle and nerve stimulator standard, IEC 60601-2-10, which specifies the safe output limits. Without going into all the details, the safe limits are much higher than what anyone uses, primarily because of issues with sensation. Also worth mentioning that the larger your electrodes, the safer it is to use higher currents, because it's current density (W/cm^2) that matters when you're talking about pain and burns.
                      Co-founder & CTO of MYOLYN - FES Technology for People with Paralysis - Empowering People to Move

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