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The physiological changes in blood flow during acupuncture needle insertion have been explored using different forms of Doppler imaging including laser Doppler perfusion imaging,1 laser Doppler flowmetry,2 and ultrasound colour Doppler.3 However, a review of the literature found no study exploring the effects of acupuncture on blood vessel size and muscle strain. With advances in ultrasound technology, these variables can be easily studied. We aimed to analyse the real-time changes in blood vessel size, blood flow velocity and volume, and muscle strain, before and after acupuncture needle insertion, and following needle removal.
Acupuncture needle insertion
We performed acupuncture needle insertion on two healthy volunteers who were part of the study team. Both team members signed an institutional informed consent form acknowledging the potential adverse effects, risks and complications. The acupuncture was performed by a certified acupuncturist with >20 years’ experience. Volunteer 1 was a male who had been exposed to acupuncture regularly. Volunteer 2 was a female with no previous exposure to acupuncture.
Scans were conducted using a Philips iu22 system (Philips Healthcare, Bothell, Washington, USA) with a 12-5 MHz linear probe. A board certified sonographer performed both scans to ensure consistency. Aquasonic 100 gel was used as the coupling agent.
The brachial artery was identified under ultrasound guidance in the transverse plane. The ultrasound probe was placed transversely approximately 1 cm proximal to the cubital crease, over the biceps muscle. This was followed by needle insertion by the acupuncturist (figure 1A) at LU5 (Chize).4 Measurements of arterial cross-sectional area (CSA; figure 1B), velocity (cm/s; figure 1C) and muscle strain (at rest; figure 1D) were performed before and after needle insertion, and following needle removal.
The CSA of the brachial artery remained constant in subject 2. In subject 1, the arterial CSA increased during needle insertion, and decreased after the needle was removed. The velocity of blood flow decreased immediately after needle insertion for both subjects. However, the decline observed in subject 1 was double that of subject 2. Following needle removal, the velocity of blood flow was maintained at a level below pre-needle insertion for subject 1, while subject 2 experienced an increased blood flow rate relative to baseline. In subject 1, the blood flow volume decreased after needle insertion, and further declined post-needle removal. In subject 2, the blood flow volume decreased after needle insertion, but increased after the needle was removed. In subject 1, the muscle strain index declined post-needle insertion, but increased after needle removal. By contrast, in subject 2, the muscle strain index increased during needle insertion, and declined post-needle removal. A summary of the changes in arterial CSA, rate of blood flow and muscle strain is given in table 1.
Our study showed that there are definite measurable physiological and physical changes during acupuncture needling. Upon needle insertion, blood flow velocity and volume decreased. This is consistent with the findings of a previous study3 that also found that blood volume returned to normal post-needle removal. By contrast, in the present experiment, the blood flow rate for the female subject spiked while that of the male remained lower than baseline following needle removal. Larger studies could be conducted to explore this phenomenon further.
For subject 1, the CSA of the brachial artery increased during acupuncture needling, while that of subject 2 remained constant. This finding corroborates a previous study, which found that the radial arterial diameter significantly increased in subjects who were regularly exposed to acupuncture, whereas no significant change was observed in acupuncture-naïve subjects.5
Observed changes in muscle strain pre-needle insertion and post-needle removal were contradictory between the two subjects. Our study shows that there may be changes in muscle strain during needle insertion and post-needle removal, but could not ascertain a definite trend. Moreover, changes in muscle strain index could also be associated with non-acupuncture related factors such as anxiety.
Acupuncture has physiological and physical effects on the human body. We observed changes in brachial artery CSA, blood flow velocity and volume, and muscle strain in healthy volunteers. Blood flow velocity decreased after needle insertion, although subsequent changes were subjective. Prior exposure to acupuncture may have an impact on the effects of needling.
Contributors MQHL, TC and SCT conceptualised the study. MQHL performed the data analysis. CCO and SHEL performed the ultrasound scans. SLC performed the acupuncture intervention. MTBMS interpreted the radiology results. All authors were involved in manuscript writing.
Competing interests None declared.
Participant consent obtained.
Provenance and peer review Not commissioned; internally peer reviewed.
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