Development of magnetic defibrillator

我们开发了“磁性除颤”(MDF)，通过它在紧急情况下将室颤转化为窦性心律。如果磁场足够强且足够长，以产生用于除颤的涡流，则可以实现MDF。本研究对MDF的关键技术进行了如下研究：(1)研制了有效的心肌磁激励线圈，并对线圈产生的涡流进行了观测和计算。线圈是由Be-Cu合金制成的平板螺线管，具有令人满意的机械强度结构。两个线圈被有效地结合在一起，以增强目标心脏的刺激场。测量了充满生理盐水的圆柱体的涡流密度的空间分布。计算结果与有限差分法计算的涡流密度吻合较好。因此，目前的线圈系统被认为是有效的MDF。(2)磁神经刺激的实验和分析…更深入地研究了磁刺激中的波形效应。在实验中，青蛙坐骨神经受到抑制正弦振荡的磁场刺激。神经兴奋的阈值取决于振荡的周期，一个周期的刺激对神经的兴奋是有效的。在分析中，有髓神经受到时变磁场的刺激。波形相关性分析与实验结果吻合较好，从而确定了磁刺激的有效波形。(3)对各种磁刺激波形的激发阈值进行了解析研究。采用Beeler-Reuters建立的心室肌细胞膜模型。衰减正弦脉冲的阈值取决于振荡的周期数，导致四分之一脉冲的阈值最低。施加双撬棍脉冲可显著降低激发阈值。较少

We developed"magnetic defibrillation"(MDF)by which ventricular fibrillation was converted to sinus rhythm in emergency. MDF can be realized if the magnetic field is strong and long enough to produce eddy currents for defibrillation. In this study key technology for MDF was developed as follows.(1)Effective stimulating coils were developed for magnetic excitation of cardiac muscle, and eddy currents produced by the coils were observed andcalculated. The coils were flat solenoids made from Be-Cu alloy, having a structure at satisfactory mechanical strength. Two coils were effectively combined to intensify stimulus fields in a target heart. The spatial distribution of the eddy current density was measured for a cylindrical volume filledwith saline solution. The result agreed well with the eddy current density calculated by the finite difference method. As a consequence, the present coil systemwas recognized for effective for MDF.(2)Magnetic nerve stimulation was experimentally and analyti … More cally studied in relation to the waveform effect in magnetic stimulation. In the experiment frog sciatic narves were stimulated by magnetic fields with damped sinusoidal oscillations. The threshold of nervous excitation depends on the cycle of the oscillation, and the one-cycle period of the stimulus is effective in exciting the nerve. In the analysis the myelinated nerve was stimulated by timevarying magnetic fields. The analysis on the waveform dependence agreed well with the experimental result.As a result, we determined effective waveforms in magnetic stimulation.(3)Magnetic heart stimulation was analytically studied on the excitation threshold for a variety of magnetic stimulus waveforms. A cell membrane of the ventricular muscle modeled by Beeler-Reuter was used. The threshold for the damped sinusoidal pulses depended on the number of cycles of the oscillation, resulting in the lowest threshold for one-quarter pulse. Applying double crowbar pulses considerably lowers the excitation threshold. Less