Dual-channel self-balancing electrodermal impedance reactometer for autonomic response studies

Combined near-infrared spectroscopy and multifrequency bio-impedance investigation of skin alterations in diabetes patients based on multivariate analyses

A group of 34 diabetic men, with different degrees of diabetes complications, including skin changes, were studied by near-infrared (NIR) spectroscopy and total body multi-frequency bio-impedance analyses (MFBIA-body). Skin reflectance spectra were measured with a fibre-optic probe in four locations (sites): hand, arm, leg and foot. As control subjects, a group of 23 healthy males were also measured. A combined multivariate analysis of the two types of spectrum was performed. It was concluded that the NIR method has the potential to detect diabetes-related skin conditions and also that the combination of the two techniques provides a higher potential for classification and discrimination of the skin conditions, with correct classification increasing from 63% to 85%.

Peripheral sympathetic neuropathy evaluated by recording the evoked electrodermal response using an impedance reactometer

Autonomic nervous dysfunction was indirectly evaluated on the basis of the skin electrical resistance relative variation (SERV), recorded by our recently developed system, with two pairs of surface electrodes placed on the palm and on the sole of the foot, after the application to the subject of a sensory stimulus (sound 60 dB, 860 Hz, 0.5 s duration) or in the course of a Valsalva manoeuvre. The results were digitally measured and recorded on thermosensitive millimetric paper analysing the following parameters: latency (LT), i.e. the time interval(s) between application of the stimulus and onset of SERV, both at palm (LTh) and foot (LTf); amplitude of the response (mm) recorded and evaluated in the form of SERV; velocity of the response as rate of time change (Vr) and autonomic conduction velocity, -ACV (m/s), calculated by the height/LT ratio. The present study refers to a group of 60 diabetic patients: 32 F/28 M; mean age +/- SD 46.8 +/- 11.8 years; 29 insulin-dependent, 21 non-insulin-dependent; duration of diabetes 8.6 +/- 4.6 years. The data were compared to those recorded in a group of 50 nondiabetics (22 F/28 M; mean age 47.5 +/- 14.1 years) who were apparently healthy. A significant statistical difference (P less than 0.001) was found between diabetic patients and controls for all studied parameters: LTh (s) 2.65 +/- 1.2 vs. 1.91 +/- 0.6; LTf(s) 3.6 +/- 1.4 vs. 2.6 +/- 0.7; SERV (mm) 7.5 +/- 4.8 vs. 18.5 +/- 6.6; Vr (mm) 4.4 +/- 2.1 vs. 13.5 +/- 5.3; ACT (m/s) 0.41 +/- 0.23 vs. 0.97 +/- 0.18.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative noninvasive electrophysiological evaluation of the activity of the cutaneous division of the sympathetic nervous system

The functional status of the cutaneous division of the orthosympathetic nervous system was indirectly and non-invasively assessed by monitoring the skin electrical relative resistance variations (SERV). The advantages of our recording system of second generation were (1) simultaneous recording on two or four channels of the evoked electrodermal response to psychic or to sensorial stimulus; (2) self-balancing system which allows the recording of the relative variation of the electric parameter, i.e. its variation with time; (3) precise determination of the amplitude (omega/s, mu F/s) of the evoked response; (4) reference of the latency time (LT) of the evoked response to the length of the anatomical pathway of the signal giving the autonomic conduction velocity (ACV). Decrease in diabetic autonomic neuropathy of both spontaneous and evoked electrodermal activities suggested their relationship with cutaneous sympathetic activity.

Improved technique for testing autonomic dysfunction: evaluation of transient behaviour of the autonomic response

The transient behaviour of the autonomic response has been studied by means of a reactometer incorporating self-balancing of the electrodermal impedance. This instrument has been used for the indirect measurement of certain parameters associated with the autonomic response detected as skin electrical resistance relative variation (SERV) and capacitance (SECV). Transient signals of the electrodermal impedance response were obtained online by differentiating the analogue output of the impedance reactometer: d(SERV)/dt and d(SECV)/dt. We describe here how the use of the transient signals of the electrodermal impedance response can improve the accuracy and reduce variability and dispersion of the results and how autonomic conduction velocities (ACV) can be indirectly measured.

Measurement of perception threshold to an electric stimulus using a phase-sensitive technique in normal and diabetic subjects

To evaluate the functional state of peripheral sensitivity we measured the perception threshold to an electrical stimulus applied deeply at the level of the lower limbs in both diabetic and nondiabetic patients. The data were obtained using a phase-sensitive technique with a sinusoidal applied voltage at 1592 Hz. The test signal applied through needle electrodes was monitored using a current-to-voltage convertor, the current being considered to have two components, one resistive (IR) in phase with the voltage V across the electrodes, and the other capacitive (IC) 90 degrees out of phase. A significantly (p less than 0.001) higher perception threshold was found in diabetic patients than in nondiabetic subjects with all three electrical variables measured: IR, IC and V.