Stimulated by Chen et al 2020.
This paper was a last-minute decision as I looked through today’s searches on PubMed. I was ready to address the influence of a WFPB meal on PPG and try to draw in the data on acupuncture for ED, but I thought TEAS would be safer.
I have avoided addressing TEAS for theoretical reasons drawn from basic science. TEAS is essentially TENS, although there are differences in terms of stimulation parameters. An intermediate term used was ALTENS or acupuncture-like TENS. Research on the best frequencies to use in EA (electroacupuncture) seemed to suggest low frequency had some advantages, but conventional TENS used high frequency, so ALTENS started with low frequency pulses of a high frequency. TEAS was developed by Jisheng Han, following on from his research on EA, and the devices still bear his name (as does the website on which they are to be found). So the HANS-200A is essentially a type of TENS device that supplies mixed frequency outputs including 2/100Hz dense dispersed – 2Hz alternating with 100Hz every 3 seconds. The pulse width used is generally 600ms at 2Hz and 200ms at 100Hz.
There is an assumption in most papers that it is equivalent to EA. My problem with this is that the clinically useful effects of acupuncture derive from stimulating small high threshold fibres (type II and III) in deep somatic tissue, and electrical stimulation on the surface of the skin (as in TENS or ALTENS or TEAS) cannot achieve this without causing intense pain in the skin as the electrical field strength diminishes from the source in an inverse square relationship (ie the field strength drops very quickly, and a few millimetres of fat are probably enough to prevent any small fibres below the skin to be discharged).
Well let’s put that aside for the moment and look at the paper.
It looks like a straight-forward parallel arm RCT comparing two doses of TEAS, and measuring post-operative pain, pre-operative sedation, and post-operative use of patient-controlled analgesia (sufentanil). The surgery was thoracoscopic pulmonary resection for early stage lung cancer. They used the acronym VATS – video-assisted thoracic surgery.
The TEAS was applied to four points on each hand and wrist: LI4, SI3, PC6 and TE6. In the sham group the stimulation was applied before and after surgery at 5mA, which is the threshold for sensation. In the active group stimulation was applied at 10-15mA before and after surgery, and 30mA during surgery whilst under anaesthesia.
The results look beautiful, with highly significant differences between the groups in nearly all outcomes measured. Part of the beauty comes from the violin plots used to present the data. I think it is the first time I have seen these used!
So, according to this and other papers, TEAS appears to be a useful technique, but I still think that it is likely to be more like TENS than it is like EA. So I thought I’d do some reference checking…
The paper’s last reference is to a review article by Han. This is a nice review of the different neurotransmitters involved in low, intermediate and high frequency EA. At the start of the article Han cites evidence (a single paper) supporting the idea that EA and TENS on acupuncture points have similar potency and mechanisms. The paper quoted is a laboratory study on rats from 1992. Unfortunately I do not have access to this paper, so I can only comment on the abstract. It was a study applying EA or TENS to ST36 and SP6 and measuring tail flick latency to a thermal stimulus. My problem with extrapolating from this type of model is that the skin and subcutaneous tissue of the lower limb of a rat is likely to be considerably thinner than that of a human, and when we bring in the inverse square law, any difference is likely to be magnified considerably.
So, I remain highly sceptical that TENS or TEAS and EA are equivalent in clinical practice, although I agree that the former are more convenient, and therefore preferable under certain circumstances.
1 Chen J, Zhang Y, Li X, et al. Efficacy of transcutaneous electrical acupoint stimulation combined with general anesthesia for sedation and postoperative analgesia in minimally invasive lung cancer surgery: A randomized, double-blind, placebo-controlled trial. Thorac cancer 2020;:1759-7714.13343. doi:10.1111/1759-7714.13343
2 Han J-S. Acupuncture: neuropeptide release produced by electrical stimulation of different frequencies. Trends Neurosci 2003;26:17–22. doi:10.1016/S0166-2236(02)00006-1
3 Wang JQ, Mao L, Han J-S. Comparison of the Antinociceptive Effects Induced by Electroacupuncture and Transcutaneous Electrical Nerve Stimulation in the Rat. Int J Neurosci 1992;65:117–29. doi:10.3109/00207459209003283
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