56. A new method for sham-controlled acupuncture in experimental visceral pain

This study aimed to investigate the validity of a new method for sham acupuncture in experimental visceral pain. Fifteen subjects underwent a sequence of either sham stimulation or acupuncture followed by visceral experimental pain stimulation. Experimental pain was induced by rectal stimulation with an inflatable balloon. The balloon was distended until the pain threshold was reached. Before and after intervention, an electroencephalogram (EEG) was recorded for 2.5 min to explore central effects of acupuncture. Only 5 participants (36%) were able to indicate the correct sequence of sham and acupuncture ( P  = 0.4; compared to chance level). A significant increase in balloon volume was observed after sham acupuncture ( P  = 0.049) and acupuncture ( P  = 0.046). However, the change in rectal balloon volume was not different between groups ( P  = 0.6). No differences in EEG spectral power distributions between sham stimulation and acupuncture were seen (all P  > 0.6). The presented sham procedure provides a valid method for blinding of “sham acupuncture” and may be used in future blinded controlled trials of acupuncture for visceral pain.