Inspired by Chao et al 2021.[1]
Random – refers to random frequency EA (in this case from 2Hz to 10Hz)
key to acronyms
DD – dense dispersed (in this case 2/10Hz for 5s each)
EA – electroacupuncture
MA – manual acupuncture
CCI – chronic constriction injury
ABVN – auricular branch of the vagus nerve
This is quite an unusual paper that was published online first in Acupuncture in Medicine on 10 November 2021. It is the first study to evaluate the effects of a random mode of delivering EA frequencies compared with the more standard DD mode.
So called dense dispersed mode was first developed by Professor Jisheng Han to maximise the effects of both low frequency and high frequency EA stimulation, since their effects appeared to be mediated by different endogenous opioids.[2] This mode of stimulation has been the most common for decades, and very few clinical trials have had the power to differentiate between different modes of EA treatment, or indeed between EA and MA.
As basic science studies have probed the various mechanisms of EA and MA, and as animal models have become more sophisticated, it has become clear that the most interesting and lasting effects of acupuncture derive from stimulation of small nerve fibres in deep somatic tissue. These fibres may have an optimal stimulation frequency in the range 2 to 15Hz and attempting to stimulate them at higher frequency may be suboptimal. I am sure I have mentioned this in the blog previously, but this idea came from discussions with the late Professor John Longhurst over his chapter in the 2nd edition of the textbook Medical Acupuncture.[3]
Laboratory experiments in animal models have the disadvantage of focussing on relatively short-term outcomes, although a few have managed to test multiple treatment cycles. This paper measures outcomes for up to 24 hours, which is long enough to demonstrate interesting differences between the modes of stimulation but is too short to draw meaningful conclusions about clinical practice in human patients, even overlooking the fact that it is a mouse model of course.
The model used in this pilot study was a CCI applied to the sciatic nerve in which 4 ligatures are tied loosely around the nerve at 1 to 1.5mm intervals. This creates hyperalgesia and allodynia in the affected limb, as well as spontaneous pain behaviour.
EA was applied to ST36 and GB34 on the affected side at either 2/10Hz DD mode or a random sequence of frequencies between 2 and 10Hz. EA was applied at a level to achieve a motor response between 0.4 to 2.0mA in anaesthetised animals for 20 minutes in one set of groups and 40 minutes in another set of groups.
random mode EA effects lasted up to 24 hours
Three different outcomes were measured. Two were different tests for mechanical allodynia and the third was a spontaneous pain behaviour scale. The results seem to show that the random mode effects lasted up to 24 hours and the DD mode effects lasted around 2 to 4 hours. The effects of the random mode were unaffected by increasing the time of stimulation from 20 to 40 minutes, whereas the effects of DD mode appeared to be diminished with the extended time.
The random mode was also applied to points in the concha of the ear (innervated by the ABVN) in another group and the effects appeared to be almost identical to the random mode applied to ST36 and GB34.
All measurements were performed blind, although animals with the CCI would have been identifiable by their behaviour from those that were normal or had received sham surgery. I don’t think this is a problem, but the fact that there were only 3 animals in each group is a limitation, and means we really need this work to be replicated before we all reach for this fancy EA device from Brazil.
Having said that, I have already looked in to getting hold of the EL608 before I saw this research because it has an ideal waveform, fine control of current and 8 outputs.
References
1 Chao L, Gonçalves AS, Campos ACP, et al. Comparative effect of dense-and-disperse versus non-repetitive and non-sequential frequencies in electroacupuncture-induced analgesia in a rodent model of peripheral neuropathic pain. Acupunct Med Published Online First: 10 November 2021. doi:10.1177/09645284211055751
2 Han JS. Acupuncture and endorphins. Neurosci Lett 2004;361:258–61. doi:10.1016/j.neulet.2003.12.019
3 Longhurst JC. Acupuncture in cardiovascular medicine. In: Filshie J, White A, Cummings M, eds. Medical Acupuncture – A Western Scientific Approach. London: Elsevier 2016. 394–421.
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