Strong energy stimulation is most effective method for the treatment of heart paralyzation (also called fibrillation), which is the main cause of sudden cardiac death. Automatic implantable defibrillator is available for the treatment of this arrhythmia. However, since the mechanism of termination of fibrillation by the electrical stimulation is not well understood, currently available automatic implantable defibrillator has many problems such as large size, heavy weight, short battery life and so on. The development of low energy defibrillation method is ideal for the improvement of current system. The purpose of this study is the development of multifunctional strong energy heart electric stimulator which is of help investigating the improvement of low energy defibrillation method. In this stimulator, number of stimulus, waveform shape such as monophasic and biphasic waveform, each subpart waveform duration, interphasic duration and output energy can be controlled. In the animal experiment using this stimulator, defibrillation energy requirement using biphasic waveform stimulation was less than50%of that using monophasic waveform stimulation.

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A wheelchair with an assistive power unit employing a differential gear is now under development. The wheelchair is specially aimed to those who have a little residual power to drive a hand driven wheelchair, but often use a powered wheelchair. People who have C5 or C6 level spinal cord injury or the aged who have lower limb impairment are initially considered. The purpose is to encourage them to keep their residual ability or even to improve it by adjusting the assistive ower. A prototype has been developed and tested on experimental basis. The prototype has one DC servo motor(120W)and the output torque is transmitted to rear wheels through a differential gear, Oldam's shaft couplings and electromagnetic clutches. Applying voltage to the clutches turns the land-driven wheelchair into a powered wheelchair. The control system is utilizing an 8 bit single chip microcomputer and rotation angle sensors. Velocity feedback control is installed in the oftware. In addition to performance tests following the JIS test procedures, 11subjects, hand-driven wheelchair users tried the prototype and found its operation easy and that it is helpful when ascending or descending a slope.

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Abstract: We have developed a pneumatically driven, pulsatile 20mL. ventricular assist device(VAD), designed to be driven using a widely distributed IABP driver. All parts of the VAD(Fig.1)including the integrated valves, housing and base were fabricated from Pellethane a biocompatible polyurethane(PU), using the vacuum forming process. The fabrication process was assesed for variations in performance of individual VADs in terms of hydrodynamics, especially in the valves. The fabrication of valves using the vacuum forming process as well as solution casting were assessed using a commercially available Bjork-Shiley Monostrut(BS)valve for comparison. The leakage rate for the valves produced by the vac. forming resulted in a rate one-fifth that of the BS valve. However, the forward flow resistance which was ten times greater than the BS valve, did not adversley effect the functioning of the PU valve. A comparison with PU valves(Fig.2)made using solution casting resulted in a leakage rate of 83-285ml/min as compared to79-109ml/min for the vac. formed valves. The VAD fabricated by vacuum forming produced a mean flow rate of approx. 2L/min(Fig.3)with only minor variations in performance, at a drive pressure of 180mmHg, vacuum of -20mmHg and under an afterload of 90mmHg. The VAD has also been trialed in chronic animal experiments to assess its' hemodynamic characteristics. The VAD was implanted in left and right heart configurations in sheep and goats for periods up to 1 month, resulting in low blood hemolysis with little evidence of thrombosis. From these results it was evident that it was possible to control the quality of an inexpensive VAD using the vacuum forming technique.

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