Objectives: To test whether electrical skin impedance at each of three acupuncture points (APs) is significantly lower than at nearby sites on the meridian (MP) and off the meridian (NP).
Design: Two instruments - Prognos (MedPrevent GmbH, Waldershof, Germany), a constant-current (DC) device, and PT Probe (designed for this study), a 100-Hz sinusoidal-current (AC) device-were used to record electrical impedance at three APs (right Gallbladder 14, right Pericardium 8, and left Triple Energizer 1), and two control sites for each AP. Each AP, MP, and NP was measured four times in random order with each device.
Setting: The study was conducted over a period of 4 days at the Oregon College of Oriental Medicine (OCOM).
Subjects: Twenty (20) healthy adults (14 women and 6 men), all recruited from the OCOM student body and faculty, participated in the study.
Results: The Prognos measurements had an intraclass correlation (ICC) = 0.84 and coefficient of variation (CV) = 0.43. The PT Probe had ICC = 0.81 and CV = 0.31. Impedance values at APs were not significantly less than at MPs or NPs. Impedance values at MPs were also not significantly less than NPs, although their individual p values were <0.05 in 4 of 6 cases. There was a significant trend of increasing impedance with repeated measurements with both the Prognos (p =0.003) and the PT Probe (p= 0.003).
Conclusions: Within the reliability limits of our study methods, none of the three APs tested has lower skin impedance than at either of the nearby control points. These results are not consistent with previous studies that detected lower skin impedance at APs than nearby sites. Further study is necessary to determine whether MPs have lower skin impedance than nearby NPs. Our study suggests caution is warranted when developing, using, and interpreting results from electrodermal screening devices. Further studies are needed to clarify the clinically important and controversial hypothesis that APs are sites of lower impedance.