Local changes in microcirculation and the analgesic effects of acupuncture: A laser doppler perfusion imaging study

Objectives: Although the local response induced by acupuncture manipulation has been considered to be among the important factors that induce the effects of acupuncture, this connection has not yet been properly studied with standardized tools. The aims of this study are to examine the local changes in microcirculation that occur at different manipulation intensities and explore any associations of these changes with the analgesic effects of acupuncture. Participants/Interventions: Twelve healthy volunteers received three acupuncture interventions (insertion only, a single manipulation, and repeated manipulations) at the right LI4 (Hegu or Hapgok) in random order. Outcome measures: Skin blood perfusion was measured in a 100-mm² area ellipse centered on LI4 by using laser Doppler perfusion imaging (LDPI) before, during, and after acupuncture stimulation. Pressure pain thresholds (PPTs) were measured at ipsilateral areas, including acupoints ST25 (abdomen), LI5 (hand), LI10 (arm), and SP9 (leg). Results: Repeated acupuncture manipulations enhanced microcirculatory perfusion compared with the insertion-only (p<0.01) and the single-manipulation (p<0.05) conditions. The repeated acupuncture manipulations significantly decreased the pressure pain at ST25 compared with the other groups (each p<0.05). Of note, Spearman correlation analysis revealed significant correlation between changes of local perfusion and PPTs (r=0.393; p=0.018). Conclusions: These results suggested that repeated manipulation induced higher local microcirculatory changes that were correlated with the analgesic effects at the relevant sites. The findings suggest that a proper dose of acupuncture stimulation might be essential to elicit the acupuncture effects.