To elucidate the rules of temporal and spatial variations in distal skin potential at Hegu (LI4) under different stimulation modes by extracting nonlinear characteristic parameters from array multichannel data and adopting multivariate statistical analysis.

Seven healthy subjects were selected and the surface potential at the left Quchi (LI11) was collected using 14×9 array multichannel electrodes. Using Hegu (LI4) on the left as the stimulation point, four stimulation modes were applied, i.e. being quiescent, point pressing, moxibustion, and manual needling manipulation. Electrical signals were collected for 30 s in each mode, with a 5-min interval between operations, and a sampling frequency of 16384 Hz. The data was denoised using ensemble empirical mode decomposition (EEMD), and sample entropy (SaEn) features were extracted. Statistical analysis was conducted on these data using factor analysis and multivariate analysis of variance.

The SaEn values of most electrode channels were higher under point pressing, moxibustion and manual needling manipulation compared with those under quiescent condition. Under manual needling manipulation, the SaEn value of the electrode channel reached the peak in the first time interval (1-5 s) and it was declining thereafter. Factor analysis showed that the specificity of activation channels was concentrated at the left Quchi (LI11) (loading capacity ≥0.90). Analysis of variance indicated that the significant differences were presented in average sample entropy (SaEn) values of activation channels among different stimulation modes at Hegu (LI4) (P＜0.001), but there was no statistically significant interaction effect between groups and time intervals (P＞0.05).

Through nonlinear characteristic parameter extraction and multivariate statistical analysis, we have uncovered the complex temporal and spatial dynamical rules of distal skin potential at Hegu (LI4) under various stimulation modes and successfully identified the specific activation characteristics at Quchi (LI11).