Functional Electrical Stimulation (FES) is efficient for restoring motor functions of paralyzed extremities by upper motor neuron disorders. An adequate set of time series of stimulus intensity to each muscle is necessary to restore desired motion by FES. With regard to the system commercially available in Japan, stimulus data that we call “stimulation patterns” are prepared and stored into the system before restoration. If patients wish to realize much better motion, it is desirable to modify the stimulation patterns. Considering their independent lives, it is very important to modify the patterns by themselves. The purpose of this study is to develop a new FES system with modification capability of the shapes of stimulation patterns. Since numerous patients have little medical knowledge about musculoskeletal system, the FES system was designed to be operated by selecting simple commands (for example, “upward”). First of all, we proposed an adjustment method of stimulus voltage using a generalized inverse matrix of the matrix describing muscles' function. Secondly, based experimental results to control wrist angles of normal subjects showed that stimulus voltages to multi-muscles were adjusted with this method. Thirdly, we developed a system that could modify stimulation patterns with the simple commands on these experimental bases. Experimental results of controlling normal subjects' wrist angles show that the user could modify stimulation patterns with this system.

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It is a time-consuming task to optimize the membership functions in fuzzy-logic-based cardiac pacing system. This paper describes a self-tuning method of membership functions and validates its feasibility in a double-sensor system which has the minute ventilation and oxygen saturation level as the guides for rate regulation. The agreement between the pacing rates (fuzzy-rates) calculated with 3 linguistic labels for each parameter and the target rates were not satisfactory, but it was improved significantly by tuning the membership functions. Higher estimated value was obtained in comparison with the case using 5 linguistic labels for each parameter. Time required for the self-tuning process was about 40 seconds (386CPU, 20MHz) which was fast enough for the system. Smaller numbers of linguistic labels results in the smaller numbers of rules, which is beneficial in the implantable cardiac pacemakers with limited memory capacity. A self-tuning method of reasoning rules is now under study.

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While, in general, spring-like property of a muscle has been assumed to account for the position control of extremity, the property has not been firmly proved in human muscles; in particular the static relation between angle and torque under the constant muscle activity that is one of the most fundamental characteristics has not been observed in human voluntary movements yet. The purpose of the preset study is to determine this static relation of human elbow joint with an aid of a neural network model. Three normal volunteers were instructed to maintain their upper extremity at target angle on the horizontal plane by balancing against an external load applied to their wrist. Both joint angle and torque around their elbow and shoulder as well as integrated electromyogram (IEMGs) of five muscles (caput longum and brave bicipitis brachii, triceps brachii, pectralis major and deltoideus) were recorded for five seconds and then time-averaged. The three-layer neural network model was constructed; the inputs were five channels of IEMGs, elbow joint angle, shoulder joint angle, and the outputs were torques of the elbow and shoulder joints. After learning, the elbow joint torque was estimated at various angles of the elbow joint while both IEMGs of five muscles and the shoulder angle were kept constant. Estimated result were as follows. The torque of elbow extensors monotonically increased as flexing the elbow joint, i. e., as elongating extensor muscles. However, the torque of elbow flexors decreased as extending the elbow joint, i. e., as elongating flexor muscles, over an angle range of largely flexed elbow joint. The property of the extensors was in agreement with that of the equilibrium hypothesis, and the property of the flexors was apparently opposite to it.

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In this paper we describe the optical characteristics of the Monoolein PVC membrane to sour solutions. The Monoolein PVC membrane was composed of polyvinyl chloride (PVC) and a synthetic lipid (Monoolein). Optical transmittance of the membrane changed remarkably after the membrane was immersed in six different sour solutions (Acetic acid, Citric acid, Formic acid, Hydrochloric acid, Lactic acid and Oxalic acid). Using an optical measurement system with optical semi-conductor devices (Light Emitting Diodes and Photo Transistors), the optical characteristics of the membrane for the sour solutions could be measured quantitatively as an intensity variation of the transmitted light of the membrane. Since the optical intensity of the transmitted light increased with different patterns in the sour solutions, the membrane had an optical selectivity. The transmitted light intensity to sour solutions were similar to the human sourness responses. To improve the time responses of the membrane reacting sour solutions, we mixed a plasticizer (di-n-butyl phthalate or tri-n-butyl phosphate) into the membrane. As a result, the time responses of the membrane became quick, and approached to the human characteristics for several sour solutions. By taking advantage of those optical characteristics, new usages, optical taste sensor and so on, are expected in the field of an ion sensing material.

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To develop the cardiac assist technique using the skeletal muscle (Cardiomyoplasty), we implanted a skeletal muscle stimulator which responded to muscle stress during continuous stimulation. To achieve this we designed a new stimulator. The stimulator responds to the variation of the output voltage from an acceleration sensor which has been inserted between the skeletal muscle and an experimental pump. The stimulator also provides the functions of R-wave synchronous stimulation and ventricular demand pacing. Both of these parameters were made programmable. In animal experiments, we confirmed the function of skeletal muscle stress estimation by using the acceleration sensor. We further confirmed synchronization rates for muscle stimulation which could be automatically controlled.

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Proportional assist ventilation (PAV) is a new mode of assist ventilation in which patients have more freedom in controlling their breathing pattern and frequency as compared to volume-cycled ventilation or pressure support ventilation such as BiPAP. Therefore, PAV is more appropriate for ventilatory assists during exercise or in a situation where patients' ventilatory demands greatly vary. We have developed an open-circuit proportional assist ventilator. The ventilator increased the maximal support pressure and the work rate in proportion to the increase in ventilation during incremental exercise up to 80 Watt. The two-dimensional diagram of the rib cage and abdominal motions (Konno-Mead diagram) resembled that during spontaneous breathing, whereas subjects had to activate abdominal muscles at the end of inspiration during exercise with BiPAP for terminating IPAP, which deformed the diagram. We infer that the criterion for detecting the inspiratory-to-expiratory transition is better in our PAV ventilator than in BiPAP. We conclude that our PAV ventilator provides a better ventilatory support for patients with respiratory insufficiency, especially during exercise or rehabilitation.

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To analyze the flow field and the mass transfer characteristics around a red blood cell moving in a fine capillary, we developed a code for grid generation around the arbitrary body and a numerical code to solve the axisymmetric Navier-Stokes equations and the diffusion equation. The numerical code was developed based on the finite difference technique and the curvilinear coordinate transformation technique. In the present paper, a red blood cell was approximated to be an axisymmetric parachute configuration based on the experimental observations. The flow field and the mass transfer characteristics around a red blood cell moving under the zero drag condition in a fine capillary were numerically obtained. Consequently, it was found that there existed an attached wake behind the red blood cell in parachute configuration even at extremely low Reynolds numbers of 0.001, and that the pressure and the shear stress along the membrane of red blood cell changed steeply. It was also found that the velocity or the physical properties of the plasma and the diffusion coefficient of the oxygen had little effect on mean Sherwood number at extremely low Reynolds numbers of 0.001 and in the range of Pe≤10.

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In this study, the parameters obtained from the impulse response function in the time domain are proposed as new pamameters for evaluation of HRV (heart rate variability). The impulse response function is estimated from the autoregressive model by which the R-R interval time series is expressed. HRV during graded head-up tilt was analyzed using the parameters, ARV, TP, heart rate, CV_R-R, and a power spectrum density function. RHI, power, time constant, and settling time were obtained from the impulse response function. The RHI is the summation of the impulse response function during the transient decreasing of the function. The power is the average value of the square of the impulse response function of the maximum settling time. The time constant is the time to reach the output value of the system when stimulation is input to 1/e or less. The settling time is the time for the value of the impulse response function to become ±0.1 or less. ARV expresses the irregularity of the time series. TP evaluates the adjustment function of the system. The subjects were the healthy males aged 19 to 27 years old. The tilt angle was 0, 20, 30, 45, 60, 90, and 0 degrees, and it was changed, respectively, every four minutes. As a result, RHI, power and TP showed a high correlation between LF/HF, that is, the index of sympathetic nerve activity. ARV exhibited a high correlation between HF, that is, the index of the parasympathetic nerve. It was possible to analyze the autonomous nerve response by TP, ARV, RHI and the power of the impulse response function. With these parameters, the realization of a simple, portable autonomous nerve response analysis device targeting real-time, non-stationary data is expected.

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