S. Ohba

A basic study about multi channel measurement of skin impedance vector loci on the acupuncture points

Acupuncture points have been found to be points of low electrical resistance compared to the surrounding tissue. The significance and detail of the singular electrical properties of acupuncture points are uncertain at present. In this report, we measured the absolute value and the phase of skin impedance on an acupuncture point and non-acupuncture point at many frequencies and current values. Absolute value, phase and vector loci of skin impedance showed dependencies on the amplitude of applied current. So, we examined how the current dependencies changed according to the test subject and measuring points. As a result, by performing reliable measurement of skin impedance vector loci, we found that the suitable frequency range of applied current to the skin is from 10 to 400 Hz and we need to determine the current value for each measurement. Additionally, we applied those results to 4 channel measurements of the skin impedance vector loci around the acupuncture point under the condition that the room temperature and humidity were kept constant.

Fundamental Study For Rolling-over Motion Of The Body By Functional Electrical Stimulation (FES)

A method to roll-over the paralyzed body by means of Functional Electrical Stimulation (FES) is considered. It is demonstrated that individual joint motions necessary for the rolling-over are realized by electrical stimulation. EMG measurements are also performed to analyze the cooperative activities of the muscles during rolling-over motion in a case where an upper extremity was used. These results of two experiments using normal subjects verifies the fundamental feasibility of body control by FES.

Functional electrical stimulation (FES) for the voluntary rolling-over of the paralyzed body-first proposal and EMG analysis

A method is proposed for achieving voluntary rolling over of the paralyzed body by functional electrical stimulation (FES). Multichannel EMG recordings were made of the rolling-over motion of normal subjects in order to determine which muscles should be the target of FES. It is believed that the proposed method may be more practical and efficient than the use of an expensive patient care robot in order to prevent bedsores (decubitus).<<ETX>>

Temporal Resolution of the Skin Impedance Measurement in Frequency-Domain Method

The temporal-resolution of the frequency-domain method for the identification of the impedance locus depends on the basis frequency used in the current waveform construction, i.e., the higher basis frequency provides the better temporal resolution. The impedance locus can be characterized by the impedance parameters Z0, beta, and taum. The frequency distribution of limited number of data in the impedance locus would affect the accuracy of the estimated impedance parameters. Therefore, we investigated the relationship between the estimation accuracy of the impedance parameters and the frequency coverage of the impedance locus in relatively low to high impedance conditions (dc impedance Z0=51 kOmega-45 MOmega). As the basis frequency, 100 Hz was enough for the usual impedance with Z0 less than 203 kOmega. On the other hand, 10 Hz and 1 Hz were required for the medium-level (Z0=517 kOmega), and high-level (Z0=45 MOmega) impedance, respectively. The required basis frequency, accordingly the temporal resolution, depended much on the central relaxation time taum which affects the frequency distribution on the impedance locus. The results of this study are expected to serve as the reference of the frequency selection in the frequency-domain analysis of the skin impedance

Experimental tests of a musculoskeletal model of the elbow joint for FES applications

Computer model prediction of motions developed by functional electrical stimulation (FES) can be effective for clinical applications. The musculoskeletal model that responds to electrical stimulation is necessary for the model prediction. In this paper, a musculoskeletal model of the elbow joint was tested experimentally on a normal subject with surface electrode stimulation. In the musculoskeletal model, the musculotendon guide that reflects geometrical arrangement of muscles was adopted. Parameters in the muscle model were adapted to the subject based on the force measured under the isometric condition. The output of the tuned model agreed well with experimental results of the single muscle stimulation at high amplitude of stimulation and results of the simultaneous antagonistic stimulation in some stimulus conditions.

A basic study on an FES control method considering fast and slow muscle characteristics

The authors propose a control method of paralyzed muscle considering fast and slow muscle characteristics for a functional electrical stimulation (FES) system in order to improve control abilities. The differences between fast and slow muscle responses at various stimulus frequencies were investigated with rabbits. Results of this study suggest the consideration of the muscle properties is useful for FES. A few ideas of FES control methods considering these properties are discussed.

Temporal resolution of the impedance locus measurement using digitally constructed current waveform

The temporal-resolution of the frequency-domain method for the identification of the impedance locus depends on the basis frequency used in the current waveform construction, i.e. the higher basis frequency provides the better temporal resolution. The impedance locus can be characterized by the impedance parameters. The frequency distribution in impedance locus, accordingly the accuracy of the estimated impedance parameters with limited number of data, highly depends on the level of impedance. Therefore, this paper investigated the relationship between the estimation accuracy of the impedance parameters and the frequency coverage of the impedance locus in relatively low to high impedances (51kΩ~45MΩ). As the basis frequency, 100Hz was enough for the usual impedance less than 203kΩ. On the other hand, 10Hz and 1Hz was required for the medium-level (517KΩ) and high-level (45MΩ) impedance. The results of this study are expected to serve as the reference of the frequency selection in the frequency-domain analysis of the skin impedance.

Classification of nerve action potentials for estimation of sensory unit activity

A method for classifying action potentials to estimate a sensory unit activity was developed. The classification of action potentials based on their waveforms involves a pattern classification problem without supervised signal. Some methods depended on an operator for specifying parameters due to the lack of a standard criterion for classification. Therefore, we have proposed an objective classification method in this paper. The performance of our method was evaluated with a simulated signal generated by a peripheral nerve model. Our method provided more appropriate classification results against the influence of the noise process than the conventional method whose reliability was reported to be high in previous studies. The classification results of our method applied to the cuff recordings suggested that there were several different stretch receptors of different characteristics, which agrees with previous reports.

Classification of action potentials recorded from peripheral nerves with cuff electrodes

In order to extract neural information, action potentials recorded with cuff electrodes from peripheral nerves were classified into unit activities. The classification was performed based on their waveforms, as it was considered that they were affected by the radius of nerve fiber and the distance between fiber and recording electrode. This study focused on automatic classification method. Action potentials were grouped into each unit by hierarchical cluster analysis and a new criterion. The method proposed in this study might be applicable to automatic classification of nerve action potentials, because it provided the reliable estimation of unit activities.

Evaluation of percutaneous electrode after implantation for FES

A quantitative evaluation of implanted percutaneous electrodes for FES is required in clinical site. We measured impedance characteristics of the electrodes from outside of the body with the newly developed system. This measurement made it possible to estimate whether the implanted electrode has suffered breakdown or has moved. In addition, it could also provide information about disconnection between the electrodes and the stimulator.