An 8-channel skin impedance measurement system for acupuncture research.

An 8-channel skin impedance measurement system for acupuncture research has been developed. The underlying model of the skin used is a parallel R & C network. Pulses are used to measure the R and C values. The measurement circuit is time multiplexed across the 8 channels at the rate of 2 measurements per second, leading to a complete set of measurements every 4 seconds. In static tests, the system has been operational for over 2 days of continuous measurements. In preliminary human tests, measurements over 2 hours have been collected per subject.

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.

Skin impedance measurements for acupuncture research: development of a continuous recording system.

Skin impedance at acupuncture points (APs) has been used as a diagnostic/therapeutic aid for more than 50 years. Currently, researchers are evaluating the electrophysiologic properties of APs as a possible means of understanding acupuncture's mechanism. To comprehensively assess the diagnostic, therapeutic and mechanistic implications of acupuncture point skin impedance, a device capable of reliably recording impedances from 100 kOmega to 50 MOmega at multiple APs over extended time periods is needed. This article describes design considerations, development and testing of a single channel skin impedance system (hardware, control software and customized electrodes). The system was tested for accuracy against known resistors and capacitors. Two electrodes (the AMI and the ORI) were compared for reliability of recording over 30 min. Two APs (LU 9 and PC 6) and a nearby non-AP site were measured simultaneously in four individuals for 60 min. Our measurement system performed accurately (within 5%) against known resistors (580 kOmega-10 MOmega) and capacitors (10 nF-150 nF). Both the AMI electrode and the modified ORI electrode recorded skin impedance reliably on the volar surface of the forearm (r = 0.87 and r = 0.79, respectively). In four of four volunteers tested, skin impedance at LU 9 was less than at the nearby non-AP site. In three of four volunteers skin impedance was less at PC 6 than at the nearby non-AP site. We conclude that our system is a suitable device upon which we can develop a fully automated multi-channel device capable of recording skin impedance at multiple APs simultaneously over 24 h.

Autonomic cardiovascular control in methyl-CpG-binding protein 2 (Mecp2) deficient mice.

Methyl-CpG-binding protein 2 is a transcription factor that is involved in gene silencing. It is mutated in the majority of cases of Rett syndrome. This X-linked neurodevelopmental disorder is reported to involve abnormalities in autonomic cardiovascular regulation. As an initial step in understanding the basis for these abnormalities we have characterized autonomic cardiovascular function in Mecp2 deficient mice. Arterial pressure waves were recorded in freely moving animals using telemetry. Baseline blood pressure and pulse interval (PI) as well as indices of heart rate variability (HRV): standard deviation of PI (SDNN), range encompassing 90% of PIs (PI90) and standard deviation of adjacent PIs (SDSD) were similar in Mecp2(+/+) and Mecp2(+/-) animals. Spectral analysis of mean arterial pressure (MAP) and PI in the frequency domain showed similar relative power in low frequency 1 (LF1, 08-0.4 Hz), low frequency 2 (LF2, 0.4-1.0 Hz), middle frequency (MF, 1-3 Hz) and high frequency (HF, 3.0-10.0 Hz) bands. Autonomic blockade with atropine or propranolol as well as elevation in ambient temperature to 32 degrees C resulted in changes in blood pressure, PI and HRV that did not differ between the strains. Atropine, propranolol and elevated temperature resulted in similar changes in both MAP and PI spectral power. Baroreceptor function was tested using intravenous injections of nitroprusside followed by phenylephrine. Maximum gain was not different. These results do reveal any disturbance of autonomic cardiovascular regulation in the Mecp2 deficient mouse genotype.