Reliability of AcuGraph system for measuring skin conductance at acupoints.

OBJECTIVE: There are many commercially available instruments for measuring electrical conductance, but there is little information about their reliability. The aim of this study was to quantify measurement variability and assess reliability of the AcuGraph system-a commonly used electrodermal screening device. METHODS: Four experiments were conducted to measure variability in electrical conductance readings obtained by the AcuGraph system. The first involved measuring known resistors. The second measured non-human organic matter. The third was a test-retest assessment of the Yuan-Source and Jing-Well points in 30 healthy volunteers who were measured by a single operator. The fourth was an interoperator reliability evaluation of seven acupuncturists at the Yuan-Source and Jing-Well acupoints on four individuals at two time points. RESULTS: Against known resistors, the AcuGraph had an average coefficient of variability (CV) of 1.8% between operators and test-retests. On non-human organic material the AcuGraph had an average CV of 0.9% and 2.8%. When a single operator tested 30 participants, the average reliability for the Yuan-Source points was 0.86 and 0.76 for Jing-Well points with a CV of 23.2% and 25.9% respectively. The average CV for the seven acupuncturists was 24.5% on Yuan-Source points and 23.7% on Jing-Well points. CONCLUSIONS: The AcuGraph measures known resistors and organic matter accurately and reliably. Skin conductance at acupoints recorded by one operator was also reliable. There was less consistency in electrodermal recordings obtained by seven different operators. Operator training and technical improvements to the AcuGraph may improve consistency among operators.

Skin conductance at 24 Source (Yuan) acupoints in 8637 patients: influence of age, gender and time of day.

The clinical practice of recording skin conductance (SC) at acupuncture points (acupoints), as a diagnostic and/or therapeutic monitoring aid may have scientific merit. However, influences of age, gender and time of day on these recordings are unknown and it is unclear whether SC at acupoints differs from SC levels in general (as reported in psychophysiology research). This paper summarizes SC data obtained with the AcuGraph 3 Digital Meridian Imaging System between June 2005 and March 31, 2010. An initial dataset of 117,725 SC examinations was scrubbed to include only the first SC examination on individual patients and exclude potentially faulty data. The final dataset consists of SC recordings at the 24 Source (Yuan) acupoints in 8637 patients, collected by 311 practitioners. Twelve left/right average conductance measures and an overall average of the 24 acupoints were assessed. Statistical analyses included two sample t tests, three way analyses of variance and linear regression. Results indicate that mean SC at acupoints, similar to SC in general, is higher in males, higher in afternoons and declines with age. Not previously reported, the rate of SC decline with age differs at different acupoints between males and females. These findings have substantial implications for acupuncture research and practice.

A multichannel system for continuous measurements of skin resistance and capacitance at acupuncture points.

Electrodermal screening (EDS) is based on three commonly held assumptions: acupuncture points (APs) have lower electrical resistance than non-APs; resistance at APs varies with health and disease; and effective acupuncture treatments are associated with normalization of resistance at APs. Although evidence confirming these assumptions is limited, EDS is frequently practiced worldwide. Researchers are also beginning to assess EDS' utility as an outcome measure in acupuncture trials. Fundamental in developing EDS as a research tool is the need for an accurate and reliable measurement. We developed an automated multichannel prototype system, the Octopus, and recorded electrical resistance and capacitance at eight skin sites in 33 healthy participants over 2 hours. The Octopus accurately measured against known resistors (within 2.5% of the mean value) and capacitors (within 10% of the mean value), and yielded repeatable readings at all eight skin sites: LR 1 (r=0.79), SP 1 (r=0.79), toe non-AP (r=0.77), LU 9 (r=0.97), PC 6 (r=0.96), wrist non-APs (r=0.97), SP 6 (r=0.96), and leg non-APs (r=0.97). Resistance at APs was significantly lower than the nearby non-APs in one out of three comparisons.