Jin W, Clark C
Department of Manufacturing and Engineering Systems, Brunel University, Uxbridge, U.K.
J Biomech. 1994 Jan;27(1):43-55. doi: 10.1016/0021-9290(94)90031-0.
The motions of the pumping diaphragm within a sac-type pneumatically driven ventricular assist device (VAD) were monitored non-intrusively using a laser Doppler anemometer (LDA) working in the back-scattering mode. The interaction between the diaphragm and the flow, and the causative factors of the motions were investigated. The motions of a number of points on the diaphragm were determined by analysing the timing of interruption of the Doppler signals due to intrusion of the diaphragm on the LDA sampling volume. The position-time relationships for the identified diaphragm points were then interpolated into two-dimensional surfaces to reconstruct the moving patterns of the diaphragm at selected instants. The motion is strongly affected by the orientation of the device with respect to gravity due to hydrostatic pressure gradients on the liquid side, which are generally large compared with those associated with the fluid accelerations. Hence, during ejection, the part of the diaphragm experiencing the lowest hydrostatic pressure is always set in motion first, while during filling, the part with the highest hydrostatic pressure moves first. Consequences of these non-symmetrical motions on local flow behaviour are discussed, and methods of controlling diaphragm shape during pumping are outlined.
利用工作在背散射模式下的激光多普勒测速仪（LDA），对囊式气动心室辅助装置（VAD）内的泵浦隔膜运动进行了非侵入式监测。研究了隔膜与流体之间的相互作用以及运动的成因。通过分析由于隔膜侵入LDA采样体积而导致的多普勒信号中断的时间，确定了隔膜上多个点的运动。然后将识别出的隔膜点的位置-时间关系插值到二维表面，以重建隔膜在选定瞬间的运动模式。由于液体侧的静水压力梯度，该运动受到装置相对于重力方向的强烈影响，与流体加速度相关的压力梯度相比，这些静水压力梯度通常较大。因此，在射血过程中，隔膜上静水压力最低的部分总是首先开始运动，而在充盈过程中，静水压力最高的部分首先运动。讨论了这些非对称运动对局部流动行为的影响，并概述了在泵血过程中控制隔膜形状的方法。
