人工心瓣脉动流试验中,主动脉根部压力、流量波形重建的实验研究

本文针对目前国内外在人工心瓣体外脉动流试验中,难以直接、准确地检测模拟主动脉根部压力、流量波形的状况,对可能导致的测试结果非客观、可比性问题进行了脉动流实验研究,并依据前文所建立的理论方法,对在现有人工心瓣体外脉动流检测装置上重建可消除测点后移误差的主动脉根部压力、流量波形,进行了流体力学实验模拟研究。     

人工心瓣脉动流试验中,主动脉根部压力,流量波形重建的…

本文针对目前国内外在人工心瓣体外脉动脉试验中，难以直接，准确地检测模拟主动脉根部压力，流量波形的状况，对可能导致的测试结果非客观，可比性问题进行了脉动流实验研究，并依据前文（２）所建立的理论方法，对在现有人工心瓣体外脉动流检测装置上重建可消除测点后移误差的主动脉根部压力，流量波形，进行了流体力学实验模拟研究。     

人工心瓣脉动流模拟实验系统的学习控制

０　引言　　目前，国内外为开展人工心瓣的研究已建立了多种脉动流模拟实验装置［１～４］，图１为本文所应用的模拟实验系统的结构图。从控制的角度看，人工心瓣脉动流模拟实验系统是一个多输入、多输出的复杂的非线性系统。系统的输出状态，如左心室压力、主动脉压力和血液流量等受多方面因素的影响，如驱动电压、特征阻力器、顺从器以及外周阻力器和顺从器等。各个因素之间又相互耦联，从而造成调整系统到期望的状态以满足人工心瓣的多种实验要求，成为一非常复杂和困难的过程。传统的脉动流模拟实验系统多采用人工调整的方法，很费时、…     

同种主动脉瓣作为人工心瓣流体动力学特性测试标准参比瓣的研究——原位移植式安装、脉动流测试结果

本研究采用类似于临床原位移植方法,将同种动脉瓣固定在PS—1型装置的主动脉瓣位上。脉动流测试结果表明:此无结构和材料缺陷心瓣表现出理想心瓣特性:小而相对固定的瓣膜关闭容积、无舒张期泄漏、瓣环可扩张,在相对于正常成人的模拟心率和心输出量时,有效开口面积不小于其对应的肺动脉瓣环径解剖值。这是用此装置测试人工心瓣血流动力学性能的绝对标准。与在体正常值比较,测试高估收缩期跨瓣压差,瞬时最大跨瓣压差这一参数的意义值得怀疑。测试结果缺乏规律,模拟左室压力波形与病理波形一致,表明采用同种主动脉瓣作为人工心瓣脉动流测试的标准参比尚需进一步研究。     

同种主动脉瓣作为人工心瓣流体动力学特性测试标准参比瓣的研究 支架固定、脉动流测试结果

在尽量保留天然结构的基础上,本研究用支架将同种主动脉辦固定在成都科大人体循环模拟系统的主动脉瓣位上,通过调整测试状态得到此种心瓣可能的最佳脉动流特性。此特性基本符合理想心瓣的特性,测试结果与临床同种瓣移植的在体观察一致,表现出较强的规律性,测试过程中装置的流动特性高度相似于生理,表明用同种主动脉瓣作为人工心瓣流体动力学特性测试的标准参比瓣完全可行且符合临床实际。为在成都科大人体循环模拟系统上,进行人工心瓣脉动流测试提供了最佳对照标准。因此采用本研究方法可建立不同测试间的可比性。     

YPV-I型牦牛心包瓣膜动物体内血流动力学

本研究报导了用20—23mm牦牛心包瓣置换二尖瓣的山羊11例。在术中测定置换前、后的左心房和左心室压力曲线,以及主动脉流量曲线。用同时测得的曲线计算出经天然和人工心瓣的平均压力降和平均流量。再根据Gomin公式求得心瓣的有效开放面积。在我们的实验条件下,人工心瓣的平均经瓣压力降比天然心瓣高出50％左右,前者的有效开放面积比后     

窦管交界锥度对生物瓣影响的脉动流实验研究EI北大核心CSCD

为了探究窦管交界直径呈现不同锥度角对于人工生物瓣膜性能的影响,对窦管交界不同锥度角的主动脉根部模型进行脉动流实验研究。通过三维打印方法制作窦管交界锥度角分别为0度、1度、3度和5度的4组主动脉根部模型。将人工生物瓣膜装配在主动脉根部模型上,在脉动循环模拟系统中进行不同心搏出量条件下的脉动流实验测试。心率设定为70次/分,脉动流流动速率分别为2~7 L/min。在每个脉动流流动速率条件下测试10个心动周期并将结果取平均值。实验结果显示,主动脉根部窦管交界不同锥度的模型,跨瓣压差符合国内标准,均在10 mm Hg之内;窦管交界锥度对于返流百分比存在影响,较小的窦管交界锥度有利于降低返流百分比;在心搏出量较小的情况下,较小的窦管交界锥度有利于增大有效开口面积,而在心搏出量较大的情况下,较大的窦管交界锥度有利于增大有效开口面积。实验结果表明,在临床手术过程中,对于心搏出量较低的情况,建议多考虑较小的窦管交界锥度;而对于心搏出量较高的情况,建议多考虑较大的窦管交界锥度。     

窦管交界锥度对生物瓣影响的脉动流实验研究

为了探究窦管交界直径呈现不同锥度角对于人工生物瓣膜性能的影响,对窦管交界不同锥度角的主动脉根部模型进行脉动流实验研究。通过三维打印方法制作窦管交界锥度角分别为0度、1度、3度和5度的4组主动脉根部模型。将人工生物瓣膜装配在主动脉根部模型上,在脉动循环模拟系统中进行不同心搏出量条件下的脉动流实验测试。心率设定为70次/分,脉动流流动速率分别为2~7 L/min。在每个脉动流流动速率条件下测试10个心动周期并将结果取平均值。实验结果显示,主动脉根部窦管交界不同锥度的模型,跨瓣压差符合国内标准,均在10 mm Hg之内;窦管交界锥度对于返流百分比存在影响,较小的窦管交界锥度有利于降低返流百分比;在心搏出量较小的情况下,较小的窦管交界锥度有利于增大有效开口面积,而在心搏出量较大的情况下,较大的窦管交界锥度有利于增大有效开口面积。实验结果表明,在临床手术过程中,对于心搏出量较低的情况,建议多考虑较小的窦管交界锥度;而对于心搏出量较高的情况,建议多考虑较大的窦管交界锥度。     

热解碳翼形双小叶心瓣在动物体内的血流动力学

本工作对热解碳翼形双小叶心瓣在山羊身上进行了血流动力学性能的评价。用内径为16mm的这种人工心瓣作二尖瓣置换术。经换瓣前、后测量的左心房、室压力曲线及升主动脉的流量曲线而计算出经瓣压力降、经瓣血流量和心瓣有效开放面积分别为:0.57±0.16KPa对0.54±0.20KPa (P>0.5)、69.07±16.92ml.sec~(-1)对47.51±13.02ml.sec~(-1) (P<0.01)和1.10±0.28cm~2对0.77±0015cm~2(P<0.01)。与本研究室所研究的内径为20mm的YPV-Ⅰ型牦牛心包瓣膜相比,心瓣置换前的此三个参数和置换后的经瓣血流量无显著性差异(P>0.5)。但置换后,双小叶心瓣的经瓣平均压力降低于牦牛心包瓣(P<0.01);双小叶心瓣的有效开放面积大于牦牛心包瓣(P<0.01)。如果两种人工心瓣的尺寸相同,则本文研究的双小叶心瓣会有更好的血流动力学性能。     

人工心瓣在脉动循环模拟系统上的能量损耗的研究

本文对常用的不同尺寸的５种人工心瓣在脉循环系统的主动脉瓣位，在不同的心率，心输邮量和主动脉平均压下进行能量损耗（Ｅｎｅｒｇｙｌｏｓｓｅｓ）的评价。人工心瓣的能量损耗据所计录的左心室压，主动脉压，前反向的跨瓣流量而计算。结果表明，跨瓣压关（ΔＰ）主输量（ＣＯ）的增加而增加，随心率（ＨＲ）和心瓣尺寸（ＶＳ）的增加而减小；跨瓣反流量（Ｒｅｇ）随ＶＳ的增加而增加，且除笼球瓣外，Ｒｅｇ随ＣＯ的增加而减少；主     

Model of the female urethra: Part 2—Flow properties

We have used a series of urethral models to test a theory of flow through distensible tubes having a pressure maximum (elastic constriction) near the midpoint. From measurements of pressure head and flow rate the properties of each elastic constriction have been deduced by means of the theory, and have been compared with those known from static measurements (paper I). For models with a sufficiently broad elastic constriction the theory is correct. Increasing departures occur as the elastic constriction becomes more sharply localised. In particular, pressures measured by a static method, similar to the Brown-Wickham method used clinically, become greater than those deduced from the flow measurements. Similar behaviour is expected for the real urethra, and may be important in the understanding of incontinence. These models show the negative-resistance behaviour believed to be characteristic of sharply localised elastic constrictions.     

Effects of Radial Wall Motion and Flow Waveform on the Wall Shear Rate Distribution in the Divergent Vascular Graft

Among the hemodynamic factors influencing intimal hyperplasia in the anastomotic region of a vascular graft, wall shear rate is believed to be one of the most important. We would like to study the effects radial wall motion on the wall shear rate distribution in the end-to-end anastomosis model of an artery and a divergent graft. Rigid and elastic models are constructed and the wall shear rate distributions are measured along the anastomosis using photochromic flow visualization method for carotid and femoral flow waveform. The mean and peak of shear rate decrease along the divergent graft, and the decreases are more significant in the elastic model. The shear rate waves are decomposed using the Fourier transform in order to separate the effects of radial wall motion and geometry. The percentage reductions of mean wall shear rates compared to steady shear rates at mean flow are calculated, and additional 8% (carotid) and 22% (femoral) reductions are observed in the elastic models near the end of the divergent graft. Also radial wall motion decreases the amplitudes of higher harmonics of wall shear rates in the elastic models. Since radial wall motion may affect the flow field differently for different geometry, wall elasticity should be considered in studying arterial hemodynamics. © 1998 Biomedical Engineering Society. PAC98: 8745Hw, 8790+y     

Left ventricular output derived from the time-derivative and phase velocities of the aortic pressure wave

A method of deriving aortic flow from pressures measured in the proximal aorta has been tested. The Womersley equation was used with the pressure gradient substituted by the time derivative of the pressure and the measured phase velocity c′ of each harmonic component. Reflected waves alter the value of c′ and are a source of error when a constant value of c is used, as in previous methods in which dP/dt has been used. The predicted mean flow was compared with that measured with a flowmeter. The results were N=720, r=0·97, y=1·00x+0·19 ml/s, s.e.e. ±12%. This was not significantly altered by a series of interventions which produced a wide range in stroke outputs. The prediction of a pulsatile flow wave was less accurate than that for mean flow. Analysis of the results shows that this is due to the fact that any method using the time derivative of the pressure cannot predict the phase of the input impedance; this leads to a distortion of the waveform on resynthesis. The amplitude of the impedance is accurately measured by the present method even when reflections markedly alter the wave velocity, as at slow heartrates. The results for predicting mean flow are shown to be better than those reported by other methods.     

弹性动脉狭窄血管内血液流动的ALE方法分析

针对弹性动脉狭窄血管中血液的流动状况,采用任意拉格朗日-欧拉方法(ALE),在给定相同的边界条件下模拟出了弹性血管和刚性血管中血流速度和压力的变化情况,分析了不同狭窄程度模型的血流状态.结果表明:随着动脉的狭窄程度增加,其中心流速越来越大,窄前压力逐渐升高,窄后压力逐渐降低,狭窄前后的压差单调增加;刚性血管无法对人体正常生理状态进行比较好的模拟,其计算所得结论与实际情况差距较大.说明ALE方法对血液流动的数值研究是可行的.     

Cerebrospinal Fluid Flow Dynamics in the Central Nervous System

Cine-phase-contrast-MRI was used to measure the three-dimensional cerebrospinal fluid (CSF) flow field inside the central nervous system (CNS) of a healthy subject. Image reconstruction and grid generation tools were then used to develop a three-dimensional fluid–structure interaction model of the CSF flow inside the CNS. The CSF spaces were discretized using the finite-element method and the constitutive equations for fluid and solid motion solved in ADINA-FSI 8.6. Model predictions of CSF velocity magnitude and stroke volume were found to be in excellent agreement with the experimental data. CSF pressure gradients and amplitudes were computed in all regions of the CNS. The computed pressure gradients and amplitudes closely match values obtained clinically. The highest pressure amplitude of 77 Pa was predicted to occur in the lateral ventricles. The pressure gradient between the lateral ventricles and the lumbar region of the spinal canal did not exceed 132 Pa (~1 mmHg) at any time during the cardiac cycle. The pressure wave speed in the spinal canal was predicted and found to agree closely with values previously reported in the literature. Finally, the forward and backward motion of the CSF in the ventricles was visualized, revealing the complex mixing patterns in the CSF spaces. The mathematical model presented in this article is a prerequisite for developing a mechanistic understanding of the relationships among vasculature pulsations, CSF flow, and CSF pressure waves in the CNS.     

Implication of the systolic hump in systemic arterial pressure waves

The systolic hump in the aortic blood pressure wave is defined as the aorticresistance component proportional to the aortic blood flow superimposed on the windkessel component. An electrical analogue comprising a series resistance (aortic resistance) plus a resistance (peripheral resistance) and capacitance (aortic compliance) in parallel (i.e. windkessel component) is used for analysis. Curve fitting using the leastsquares method is performed on calculated and measured blood pressure waves from dogs under haemodynamical conditions induced by infusion of three drugs (noradrenaline, isoproterenol and acetylcholine). The curve fitting RMS (root mean square) errors are <3% for blood pressure waves and <30% for blood flow waves, with good agreement between measured and calculated blood flow waveforms. Infusion of noradrenaline and acetylcholine is found to induce a significant decrease and increase in the aortic resistance, respectively. Although only a small fraction of the blood pressure wave, the systolic hump has a marked effect on the systolic pressure waveform.     

脑室腹腔分流装置流量测算方法

目的 提供一种预算患脑室腹腔分流装置实际流量的方法；方法 根据流体力学的相似原理，首先测定水通过患拟使用的分流装置的压力－流量关系，然后利用腰椎穿刺测定患颅内压及脑脊液粘度；利用流体力学相似准则推导公式，计算出脑脊液实际流量；结果 准确测算在一定体温、颅内压、脑脊液粘度的条件下脑脊液在分流装置中的流量，为术前选择分流装置及术后控制分流量提供客观依据；结论 此测算方法为进一步研究脑脊液粘度、蛋白含量、流量之间关系提供方法；并在一定条件下指导分流术前选管和术后分流管的管理。     

Pulse-wave reflection in elastic tubes

Reflection of incident pressure and flow waves will occur at any discontinuity present in an elastic tube. This paper investigates the magnitude of the reflected waves produced by abrupt changes in the tube diameter and wall elasticity. The effect of these reflections on the proximal and distal pressure and flow waves is demonstrated together with the resultant effects on the hydraulic impedance. Experimental values of reflection coefficient are calculated from the impedance data and compared with those obtained from a theoretical model. The diagnostic significance of these findings is discussed.     

Evaluation of the appropriate root pressure for maintaining heartbeat during an aortic cross-clamp for primary repair of the aortic arch in premature infants with associated cardiac anomalies

We developed a new cardiopulmonary bypass (CPB) method to minimize myocardial damage during aortic arch reconstruction. In this method, coronary flow and heartbeat were stabilized by maintaining the aortic root pressure with an adjusted preload of the ventricle during aortic cross-clamping. This study was performed to determine the appropriate root pressure to maintain the heartbeat without causing deterioration of ventricular function. Study 1. Under partial CPB, the ascending aorta was cross-clamped in 6 pigs (group 1). Experimental data at various systolic aortic root pressures was analysed to determine the appropriate root pressure. Study 2. In group 2 (control, n＝6), the aorta was not clamped, while in group 3 (n＝6), the aorta was cross-clamped for 60 min and the systolic aortic root pressure was maintained at the pressure determined in study 1. Study 1. The diastolic coronary flow was stabilized at values comparable to that before initiation of CPB (6.6±1.4 ml/beat) when the systolic aortic root pressure was above 80 mmHg. Intracardiac pressure and the myocardial oxygen consumption (MvO2) seemed to be acceptable when the systolic aortic root pressure was below 100 mmHg. Therefore, 90 mmHg was selected for study 2. Study 2. Perioperative cardiac function did not differ between the groups. We concluded that 90 mmHg was the systolic aortic root pressure appropriate for this method.