Mechanical haemolysis in shock wave lithotripsy (SWL): I. Analysis of cell deformation due to SWL flow-fields
Mechanical haemolysis in shock wave lithotripsy (SWL): I. Analysis of cell deformation due to SWL flow-fields
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DOI：
10.1088/0031-9155/46/2/310
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发表时间：
2001-02-01
影响因子：
3.5
通讯作者：
Sturtevant, B
中科院分区：
文献类型：
--
作者：
Lokhandwalla, M;Sturtevant, B
本文分析了冲击波碎石术中红细胞与冲击波和气泡流的相互作用，并在体外计算了这两种流的溶解效应。一个众所周知的实验观察到的关于RBC膜的事实是，当受到3%的面积应变（Δ A/A）（c）和10 mN m（-1）（1 mN m（-1）= 1 dyne cm（-1））的相应的临界各向同性张力T-c时，脂质双层破裂。悬浮在流体介质中的RBC倾向于根据周围流体介质的变形而变形。根据运动学分析，基本流体粒子的运动总是可以分解为均匀平移、沿沿着三个相互垂直的轴的伸展流（例如，（u）在右箭头（无穷大）上（x，y，z）=（k（t）x，-k（r）y，0））以及这些轴的刚性旋转。然而，只有拉伸流动引起流体颗粒的变形，并因此使RBC膜变形。在SWL中，假设由非均匀冲击波以及气泡的径向膨胀/内爆引起的流体流场导致细胞溶解。上述两种流场构成了不稳定的拉伸流，其对RBC膜施加惯性力以及粘性力。瞬时惯性力（表示为张力或力/长度）由类似于pr（c）（3）k/tau的T-iner给出，其中tau是瞬时流动的时间尺度，r（c）是特征单元尺寸。当膜由于惯性效应而变形时，膜应变由类似于k τ的Δ A/A给出。瞬态粘性力由类似于p（nu/tau）（1/2）r（c）（2）k的T-visc给出，其中p和v是流体密度和运动粘度。对于非均匀激波，拉伸流产生的惯性力T-iner约为64 mN m（-1），持续时间为3 ns，足以在RBC膜上产生孔隙;对于径向流场，气泡膨胀/内爆产生的惯性力T-iner约为100 mN m（-1），持续时间为1 μ s，足以引起破裂。在典型的体外实验条件下，预测气泡诱导径向流比冲击诱导流更有效。
This work analyses the interaction of red blood cells (RBCs) with shock-induced and bubble-induced flows in shock wave lithotripsy (SWL), and calculates, in vitro, the lytic effects of these two flows. A well known experimentally observed fact about RBC membranes is that the lipid bilayer disrupts when subjected to an areal strain (DeltaA/A)(c) of 3%, and a corresponding, critical, isotropic tension, T-c, of 10 mN m(-1) (1 mN m(-1) = 1 dyne cm(-1)). RBCs suspended in a fluid medium tend to deform in accordance with the deformation of the surrounding fluid medium. The fluid flow-field is lytically effective if the membrane deformation exceeds the above threshold value.From kinematic analysis, motion of an elementary fluid particle can always be decomposed into a uniform translation, an extensional flow (e.g. (u) over right arrow (infinity)(x, y, z) = (k(t)x, -k(r)y, 0)) along three mutually perpendicular axes, and a rigid rotation of these axes. However, only an extensional flow causes deformation of a fluid particle, and consequently deforms the RBC membrane. In SWL, a fluid flow-field, induced by a non-uniform shock wave, as well as radial expansion/implosion of a bubble, has been hypothesized to cause lysis of cells. Both the above flow-fields constitute an unsteady, extensional flow, which exerts inertial as well as viscous forces on the RBC membrane. The transient inertial force (expressed as a tension, or force/length), is given by T-iner similar to pr(c)(3) k/tau, where tau is timescale of the transient flow and r(c) is a characteristic cell size. When the membrane is deformed due to inertial effects, membrane strain is given by DeltaA/A similar to k tau. The transient viscous force is given by T-visc similar to p(nu/tau)(1/2)r(c)(2)k, where p and v are the fluid density and kinematic viscosity. For the non-uniform shock, the extensional flow exerts an inertial force, T-iner approximate to 64 mN m(-1), for a duration of 3 ns, sufficient to induce pores in the RBC membrane.For a radial flow-field, induced by bubble expansion/implosion, the inertial forces are of a magnitude 100 mN m(-1), which last for a duration of 1 mus, sufficient to cause rupture. Bubble-induced radial flow is predicted to be lytically more effective than shock-induced flow in typical in vitro experimental conditions.