Abstract: OBJECTIVE: To observe capillary blood flow at acupoints during acupuncture treatment of primary dysmenorrhea and gain new insights into its analgesic mechanism. METHODS: Patients with primary dysmenorrhea were enrolled and randomly assigned to a treatment or control group. Subjects' symptoms were differentiated into variousTraditional Chinese Medicine(TCM) syndromes and treated for 10 sessions with puncturing acupuncture or self-pressing right-hand Hegu(LI 4), adding other acupoints based on syndrome. Laser speckle was used to compare the change in the vasomotor amplitude and perfusion of the capillaries in Hegu(LI 4) before and during the treatment. Each subject was required to finish the period pain symptoms observation form, verbal rating scales, numerical rating scale, pain rating index, face rating scale, Zung self-rating depression scale, Zung self-rating anxiety scale, and numerical rating scale before and after treatments. RESULTS: After 10 sessions, the symptom scores, pain index(PI), and visual analog scale(VAS) decreased significantly in treatment group. The volume of blood flow in Hegu(LI 4) declined slightly. No significant evidence supported that needling caused capillary contraction, but the capillary vasomotor amplitude at Hegu(LI 4) increased remarkably. CONCLUSION: Acupuncture can increase the capillary blood flow, thus promoting the flow of Qi and blood in terms of TCM theory, which facilitates pain relief.

Key words: Capillaries, Perfusion, Acupuncture therapy, Arrival of Qi, Point LI 4(Hegu), Dysmenorrhea, Manifest anxiety scale, Laser speckle blood flow scanning, Vasomotor amplitude