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capacitive resistive monopolar radiofrequency

I was very interested to read recently the paper by Kumaran and Watson (2018) about the capacitive resistive monopolar radiofrequency (CRMR ) modality. The modality appears to have in use for quite a while in some countries where it is also known as Capacitive and Resistive Electric Transfer (CReT) (Yokota et al 2017), but as a UK based physiotherapist it is not a machine I have ever seen in practice. Despite quite a bit of literature searching on this area I have been unable to find information to help answer the following questions and would be grateful if anyone with knowledge or experience in this area could help.

  1. How does CRMR/CRet) differ substantially from the old form of long wave diathermy which I understand was discontinued a long time ago?
  2. What are the physical principles that allow/require skin coupling agent for the active and inactive electrode for CRMR/CReT, whereas in the other therapeutic radiofrequency treatments of shortwave and microwave this is not allowed/required?
  3. In most studies I have read using CRMR/CRet they seem to use 10-15 minutes of capacitive mode followed by 10-15 minutes of resistive mode. I have been unable to find any theoretical justification for the use of both modes in this way, although I understand that the capacitive and resistive modes may have similarities to the capacitive and inductive modes respectively, of short wave (Kumaran and Watson, 2015)
  4. If one was aiming for a deep thermal effect, are there any theoretical or practical reasons why this form of radiofrequency treatment could be better than continuous short wave diathermy

Any advice on any of the questions above would be very gratefully received

References Kumaran, B., & Watson, T. (2015). Thermal build-up, decay and retention responses to local therapeutic application of 448 kHz capacitive resistive monopolar radiofrequency: A prospective randomised crossover study in healthy adults. International Journal of Hyperthermia, 31(8), 883–895. http://doi.org/10.3109/02656736.2015.1092172 Kumaran, B., & Watson, T. (2018). Skin thermophysiological effects of 448 kHz capacitive resistive monopolar radiofrequency in healthy adults: A randomised crossover study and comparison with pulsed shortwave therapy. Electromagnetic Biology and Medicine, 1–12. http://doi.org/10.1080/15368378.2017.1422260 Spottorno, J., Gonzalez de Vega, C., Buenaventura, M., & Hernando, A. (2017). Influence of electrodes on the 448 kHz electric currents created by radiofrequency: A finite element study. Electromagnetic Biology and Medicine, 36(3), 306–314. http://doi.org/10.1080/15368378.2017.1354015 Yokota, Y., Tashiro, Y., Suzuki, Y., Tasaka, S., Matsushita, T., Matsubara, K., … Aoyama, T. (2017). Effect of Capacitive and Resistive Electric Transfer on Tissue Temperature, Muscle Flexibility, and Blood Circulation. Journal of Novel Physiotherapies, 7(1), 1–7. http://doi.org/10.4172/2165-7025.1000325

Alan David Hough

8 months ago

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Prof Tim Watson
Prof Tim Watson

indeed, I think that the capacitive mode may well generate pain relief on the basis of superficial heating and blood flow effects - entirely possible. When se did the clinical trial (OA knee) we did 5 mins CAP then 10 mins RES modes (as per the lab studies) but did not attempt to differentiate the pain relief effects as it would have interrupted the treatment - which would be clinically irrelevant. Will let everyone know when the paper is out. Tim

alandavidhough377
alandavidhough377

Dear Tim Many thanks for the quick and very helpful response. It is much clearer to me now how the CRET works and where it sits in comparison to shortwave, thank you. The explanation about the use and relative effects/benefits of Capacitive and Resistive modes makes complete sense to me. I wonder whether perhaps the more superficial Capacitive mode may have potentially greater pain relieving effects as well? I was thinking that one major practical advantage of the CRET over SWD would be that if it can be delivered with the operator moving the active electrode, then stray radiation from this system is not such an issue as it is with SWD systems? My feeling is that the potential hazards/inconvenience of the use of SWD in physiotherapy departments due to stray radiation, particular using the capacitive method, is one of the reasons why it is used less nowadays in the UK, despite evidence suggesting potential benefits 1–5. It would be good if similar or better clinical effects can be achieved with CRET type systems and I really look forward to seeing your clinical study paper. Many thanks again

  1. Wang H, Zhang C, Gao C, et al. Effects of short-wave therapy in patients with knee osteoarthritis: a systematic review and meta-analysis. Clin. Rehabil. 2017;31(5):660-671. doi:10.1177/0269215516683000.
  2. Incebiyik S, Boyaci A, Tutoglu A. Short-term effectiveness of short-wave diathermy treatment on pain, clinical symptoms, and hand function in patients with mild or moderate idiopathic carpal tunnel syndrome. J. Back Musculoskelet. Rehabil. 2015;28(2):221-228. doi:10.3233/BMR-140507.
  3. Hanchard NCA, Goodchild L, Thompson J, O’Brien T, Davison D, Richardson C. Evidence-based clinical guidelines for the diagnosis, assessment and physiotherapy management of contracted (frozen) shoulder: quick reference summary. Physiotherapy 2012;98(2):117-20. doi:10.1016/j.physio.2012.01.001.
  4. Leung MSF, Cheing GLY. Effects of deep and superficial heating in the management of frozen shoulder. J. Rehabil. Med. 2008;40(2):145-50. doi:10.2340/16501977-0146.
  5. Laufer Y, Dar G. Effectiveness of thermal and athermal short-wave diathermy for the management of knee osteoarthritis: a systematic review and meta-analysis. Osteoarthr. Cartil. 2012;20(9):957-966. doi:10.1016/j.joca.2012.05.005.
Prof Tim Watson
Prof Tim Watson

Interesting query. I will do what I can - though as I was involved in the research you are citing, I appreciate that you might be 'wary' of my response. We have a CRET clinical trial about to come out (submitted) which might provide useful additional information.

How does CRMR/CRet) differ substantially from the old form of long wave diathermy which I understand was discontinued a long time ago? ^^ the old longwave diathermy was a NON CONTACT technique - more like current shortwave applications. The CRET is a similar radiofrequency (around 0.5MHz) BUT is delivered in CONTACT with the tissues - this (to me) is the critical difference. There IS a current flow through the tissues with CRET. There is an INDUCED current with longwave.

What are the physical principles that allow/require skin coupling agent for the active and inactive electrode for CRMR/CReT, whereas in the other therapeutic radiofrequency treatments of shortwave and microwave this is not allowed/required? ^^ as above - it is necessary as the energy delivered is effectively an electric current application. I have been thinking of it as a Radio Frequency Electric Current. Skin contact and electric coupling are therefore essential for the energy to get into the tissues

In most studies I have read using CRMR/CRet they seem to use 10-15 minutes of capacitive mode followed by 10-15 minutes of resistive mode. I have been unable to find any theoretical justification for the use of both modes in this way, although I understand that the capacitive and resistive modes may have similarities to the capacitive and inductive modes respectively, of short wave (Kumaran and Watson, 2015) ^^ my personal opinion (backed up by the Kumaran and Watson research that you cite) is that the RESISTIVE mode is probably the most 'effective'. The CAPACITIVE mode (we only used 5 mins) may serve to increase skin temp and blood flow making it 'easier' for the RESISTIVE energy to get into the tissue at depth. Our evidence would support that postulation.

If one was aiming for a deep thermal effect, are there any theoretical or practical reasons why this form of radiofrequency treatment could be better than continuous short wave diathermy ^^ our results (lab and clinical) included direct comparisons with shortwave - which we took to be the nearest equivalent existing therapy. The CRET results (using Indiba equipment at 448kHz) were significantly 'stronger' and certainly longer lasting than those with shortwave. I genuinely did not expect this result - thought they would be the same or at least very similar. The CRET effects were still in evidence 45mins + after end of treatment - WAY longer than shortwave effects. ??? Any help ??? Tim

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