下肢动脉闭塞性病变的多普勒血流频谱形态观察

目的：观察下肢动脉闭塞性病变的多普勒血流频谱。方法：选择32例下肢动脉栓塞患者作为研究对象并行彩色多普勒超声检查,观察血流频谱及血流频谱指标,并与健侧做比较。结果：32例下肢动脉闭塞患者,闭塞长度最长28cm,最短4.8cm,平均长度17.4±4.9cm;闭塞前段血流频谱形态失常,频窗消失,频带增宽,舒张期反向血流消失,出现静脉样血流频谱或者舒张期正向血流频谱,闭塞后段频谱多普勒呈单向且血流速度减低或无血流频谱。下肢动脉血流频谱各项指标显示,患侧PSV明显低于健侧,AT、RI、PI明显高于患侧（p＜0.05）。结论：多普勒超声血流频谱异常改变是下肢动脉闭塞性疾病一项重要的检查方式,有较高的临床价值。     

糖尿病人眼球后动脉血流的二维/脉冲多普勒超声研究

本文首次应用二维脉冲多普勒超声技术(2DE-PDE)对23例正常人和25例糖尿病患者 的视网膜中央动脉(CRA)与眼动脉(OA)进行血流动力学定量研究。证实了糖尿病患者的血 流频谱特征。其血流峰值,峰时和血流时相等测值与正常人有显著差异(P(0.05-0.01),并 与糖尿病性视网膜病变关系极为密切。平均血流速度(Vm),脉动指数(PI)和阻力指数(RI) 与血糖测值呈明显负相关关系(t值分别为-0.68,-0.51、-0.64)。2DE-PDE是一种简 便,可靠的无创性诊断技术,为糖尿病视网膜病变患者的眼血流动力学研究和动态评价提供 了一种极有价值的定量检测方法。糖…     

双功能及彩色多普勒超声检测糖尿病人下肢血管病变的价值

本文报告应用双功能及彩色多普勒超声扫描仪检测136例糖尿病人下肢动脉的血管形态和血流动力学变化结果,并与20例正常人进行对照,现报告如下: 一、病例选择与方法 136例均经临床确诊为糖尿病,男89人,女47人,年龄24～81岁(平均55.5岁),其中Ⅱ型131例,Ⅰ型5例。正常组20人,男15人,女5人,年龄43～70岁(平均57.1岁),均无糖尿病家族史,尿糖阴性,血糖正常,血压及血脂检查正常。仪器为ACUSON 128,频率5MHz。探测部位为双侧股、■、胫后及足背动脉。以二维图象显示观察下肢血管壁内膜、管腔形态及测量其内径。彩色多普勒显示血流空间分布及方位,…     

颅脑火器伤后犬颈内动脉血流动力学改变的初步观察

初步探讨颅脑火器伤后颈内动脉血流动力学变化及其临床意义。17只杂种犬,滑膛枪近距离由左额部射入钢珠建立犬颅脑枪弹伤模型。于伤前、伤后30min、2h、4h、6h检测右侧颈内动脉血流动力学参数:峰值流速(Vp)、舒张期末血流速度(Vd)、平均血流速度(Vm)、阻力指数(RI)和搏动指数(PI)。其间动态观测颅内压及动脉压。所有实验犬伤后30min颅内压较伤前已明显升高(P<0.01),动脉压降低(P<0.05),颈内动脉Vp、Vm、Vd明显降低(P<0.05)。其中4只颅内压升高最为显著的犬RI和PI明显增高,甚至在舒张早期出现负向频谱;另13只犬RI和PI较伤前改变不明显。伤后其余各时间点如内生命体征维持较平稳,血流动力学参数均稳定在伤后第一次检查水平。颅脑火器伤后颈内动脉Vp、Vm、Vd明显降低,但伤犬的血流动力学参数由于同时受颅内压升高、动脉压降低双重影响,难以准确判定其颅内压升高程度;部分伤犬RI和PI明显增大,提示颅内压升高到一定程度、动脉压又显著降低,导致脑灌注压低于某一域值,此现象的出现可能存在潜在临床意义。     

G7 二维/脉冲多普勒对青光眼眼血流动力学研究

本文首次应用二维和脉冲波多普勒超声技术对57例正常人(平均年龄46.6岁)共114只眼 球后的视网膜中央动脉(CRA)、睫状动脉(CA)和眼动脉(OA)进行血流动力学定量研究。结 果表明:CRA、CA和OA血流检出率分别为100%、96.5%和98.3%。频谱均呈典型的脉动 血流特征。CRA、CA和OA的峰值血流速度分别为10.03±1.98cm/see,23.27±5.72cm/ see,29.95±6.09cm/sec。并提出舒张期和平均血流速度及速度一时相等指标的测量方法和 意义。该技术是一种简便、可靠的无创性诊断方法,为临床眼血流动力学的研究和客观评价 提供了一种有价值的手段。正常人…     

糖尿病并发脑梗死患者的下肢动脉病变B超分析

目的:探讨糖尿病并发脑梗死患者的下肢动脉病变B超诊断的价值。方法:选取2013年3月至2015年10月期间在我院接受治疗的80例糖尿病并发脑梗死患者作为观察组,选取同期健康体检者80例作为对照组,采用B超对两组参与人员进行双下肢动脉检查,对比两组人员的血管形态、内-中膜厚度(IMT)、粥样硬化斑块、管腔狭窄或闭塞情况、血流动力学改变情况等。结果:观察组下肢动脉内膜增厚、斑块、狭窄及闭塞阳性率明显高于对照组,差异具有统计学意义,P0.05。结论:B超检测糖尿病并发脑梗死患者的下肢动脉病变临床价值较高。     

卧式下肢康复机器人动力学建模及控制研究

为掌握人体下肢在康复训练过程中的力学特性,对卧式下肢康复机器人进行了动力学建模和仿真研究。考虑到机器人利用机构牵引人体下肢,辅助患者实现对髋、膝、踝关节的康复训练,将人体下肢和机构作为一个整体,应用闭环矢量法和牛顿-欧拉法建立了机器人的运动学及动力学模型,并以动力学模型为基础,基于计算力矩法设计了控制器,以轨迹跟踪为目标进行了仿真研究。仿真结果表明,该控制方案对康复训练是有效的,并且动力学模型能快速、有效地给治疗师和患者提供训练参数,为制定有效的康复训练策略和进行动态性能分析提供理论依据。     

不同体重正常SD大鼠肝脏血流动力学的超声观察

目的:该研究旨在用高频超声观察SD大鼠体重对门静脉内径、门静脉及肝固有动脉血流动力学的影响。方法:按体重将100只SD大鼠分为两组,A组:200~300 g;B组:300~400 g。采用5.0~12.0 MHz超声探头测定大鼠门静脉内径,门静脉最大血流速度及肝固有动脉收缩期血流峰值速度、舒张期末血流速度及阻力指数。结果:A组SD大鼠门静脉内径(0.172±0.030)cm;B组SD大鼠门静脉内径(0.189±0.030)cm。门静脉内径在不同体重间存在显著差异(P0.01)。门静脉流速、肝固有动脉收缩期最大峰值流速、舒张期末流速及阻力差异无统计学意义。结论:在大鼠肝脏疾病模型的观测和评估实验中,动物体重应尽可能一致。     

彩色多普勒超声对移植肾血管并发症的诊断价值

目的:彩色多普勒超声检查可较敏感地反映移植肾血流动力学的改变,随时观察移植肾的成活情况,评价彩色多普勒超声在移植肾血管并发症中的应用效果。方法:回顾性分析9例移植肾血管并发症患者的彩色多普勒超声结果,观察肾结构、肾内血流信号的分布、肾静脉主干回声和血流充盈情况,测量主肾动脉、段动脉、叶间动脉及弓形动脉流速及阻力指数、搏动指数。结果:对2007年9月-2012年9月10例移植肾血管并发症进行分析,5例肾动脉狭窄,1例肾动脉栓塞,1例肾静脉狭窄,2例肾静脉血栓及1例假性动脉瘤。结论:彩色多普勒超声具有简便、迅速、无创、可重复性等优点,已成为肾移植后临床观察治疗效果的首选监测手段。它能客观、动态显示移植肾形态结构及其内部的血流分布,血流频谱形态、流速、舒张期血流方向和血流指数变化,及时发现移植肾血管并发症,查找导致移植肾功能损害的部分原因,早期明确诊断并给予及时治疗,对提高肾移植成功率起重要作用。     

微创介入全降解血管支架和心脏瓣膜国内外研发现状与研究前沿

心血管疾病是世界范围内的头号健康杀手。我国心血管疾病患者近3亿人,心血管疾病死亡人数约300万人/年,占所有疾病致死总人数45%。临床主要心血管疾病是冠心病和心脏瓣膜疾病。目前,微创介入治疗因风险小、手术时间快、创伤小、恢复快,已成为心血管疾病治疗最为有效的手段和主流趋势。因此,心血管微创介入材料与器械已成为心血管疾病治疗领域研究的热点。随着全球医疗器械市场稳健快速发展,心血管器械已成为医疗器械行业中仅次于体外诊断的第二大市场。心血管介入医疗器械领域的两个市场前景广阔的代表性产品是全降解血管支架和经导管心脏瓣膜。全降解支架克服了传统支架植入后长期存留在血管中会引起潜在的慢性炎症、晚期血栓及需长期进行抗血小板治疗等问题,已成为当下心血管植介入领域的研究热点及焦点。全降解血管支架根据材料的不同可分为全降解聚合物血管支架与全降解金属血管支架。因采用的材料性能各异,支架的制备方式也大有不同。近10多年来,微创介入式生物瓣膜产品研发取得了快速发展。相关国产产品自2017年起已获得CFDA批准上市并在临床上大规模应用。然而现有的生物瓣膜仍然存在使用寿命较短、适用人群受限、置入准备过程繁琐、无法紧急应用导致的各类手术风险等不足,因此,研发具有更加优良的抗钙化、防周漏、可预装等性能的瓣膜已成为当前微创介入瓣膜研究的趋势与前沿。本文详细总结了心血管介入医疗器械领域的两个代表性产品(全降解血管支架和经导管心脏瓣膜)的国内外研发现状及研究前沿,并讨论了目前研究中存在的难题和解决思路。最后展望了未来该领域的研究方向及前景,为相关研究者提供借鉴与参考。     

A new multi-scale simulation model of the circulation: from cells to system

We developed a comprehensive cell model that simulates the sequential cellular events from membrane excitation to contraction in the human ventricle. By combining this ventricular cell model with a lumped circulation model, we examined how blood pressure dynamics in the ventricle and aorta are related to the cellular processes. To convert cell contraction into ventricular pressure using Laplace's law, we introduced a simple geometric model of a ventricle: one shaped like a thin-walled hemisphere. The force of contraction of a single cell induces tension in the hemispheric ventricular wall, which generates the ventricular and aortic pressures in the lumped circulation model. The time courses of the hemodynamic properties, as well as the volume-pressure trajectory of the left ventricle, were well reproduced. Our multi-scale cardiovascular model, which covers from cardiac cells to the circulatory system, simulates the typical characteristics of heart mechanics, such as the pressure-volume relationship, stroke volume and the effect of the increased maximum free calcium concentration on cardiovascular hemodynamics. To test the cell-circulation coupling characteristics of the model, we simulated the effects of a decrease in L-type calcium channel conductance (cell level) on left ventricular pressure (system level). The variation due to different pacing frequencies for myocyte excitation was also investigated to assess the effects of heart rate on cardiac cells and the circulatory system.     

Leg stiffness of sprinters using running-specific prostheses

Running-specific prostheses (RSF) are designed to replicate the spring-like nature of biological legs (bioL) during running. However, it is not clear how these devices affect whole leg stiffness characteristics or running dynamics over a range of speeds. We used a simple spring–mass model to examine running mechanics across a range of speeds, in unilateral and bilateral transtibial amputees and performance-matched controls. We found significant differences between the affected leg (AL) of unilateral amputees and both ALs of bilateral amputees compared with the bioL of non-amputees for nearly every variable measured. Leg stiffness remained constant or increased with speed in bioL, but decreased with speed in legs with RSPs. The decrease in leg stiffness in legs with RSPs was mainly owing to a combination of lower peak ground reaction forces and increased leg compression with increasing speeds. Leg stiffness is an important parameter affecting contact time and the force exerted on the ground. It is likely that the fixed stiffness of the prosthesis coupled with differences in the limb posture required to run with the prosthesis limits the ability to modulate whole leg stiffness and the ability to apply high vertical ground reaction forces during sprinting.     

Continuous renal replacement therapy is associated with acute cardiac stunning in critically ill patients

Introduction: Intermittent renal replacement therapy induces cardiac stunning in chronic hemodialysis and acute kidney injury (AKI) patients. In chronic hemodialysis, recurrent stunning contributes to heart failure and cardiac death, with ultrafiltration and intradialytic hypotension being the principal determinants of this injury. Continuous renal replacement therapy (CRRT), with its lower ultrafiltration rates and improved hemodynamic profile, should protect against cardiac stunning in AKI. The objective of this study was to assess whether CRRT is associated with cardiac stunning in critically ill patients with AKI. Methods: We prospectively measured cardiac function using global and segmental longitudinal left ventricular strain using transthoracic echocardiography in 11 critically ill patients who were started on CRRT for AKI. We compared measurements at 4, 8, and 24 hours to baseline immediately prior to initiation of CRRT, with each patient serving as their own control. We also recorded blood pressure, heart rate, dose of vasoactive medications and intensive care unit mortality. Findings: Ten of 11 patients developed new regional cardiac stunning, with 8/11 within 4 hours of starting CRRT, despite stable hemodynamics. The number of affected left ventricular segments varied from 1 to 11 (out of 12). The stunning occurred both in patients with preserved and impaired baseline cardiac function, and 7/11 patients died in the intensive care unit. Discussion: Initiation of CRRT in critically ill patients with AKI is associated with cardiac stunning despite stable hemodynamics. This mechanism may explain lack of clinical benefit of CRRT over intermittent modalities and warrants further investigation to improve cardiovascular outcomes in critically ill patients with AKI.     

Fluid–structure Interaction Modeling of Aneurysmal Conditions with High and Normal Blood Pressures

Hemodynamic factors like the wall shear stress play an important role in cardiovascular diseases. To investigate the influence of hemodynamic factors in blood vessels, the authors have developed a numerical fluid–structure interaction (FSI) analysis technique. The objective is to use numerical simulation as an effective tool to predict phenomena in a living human body. We applied the technique to a patient-specific arterial model, and with that we showed the effect of wall deformation on the WSS distribution. In this paper, we compute the interaction between the blood flow and the arterial wall for a patient-specific cerebral aneurysm with various hemodynamic conditions, such as hypertension. We particularly focus on the effects of hypertensive blood pressure on the interaction and the WSS, because hypertension is reported to be a risk factor in rupture of aneurysms. We also aim to show the possibility of FSI computations with hemodynamic conditions representing those risk factors in cardiovascular disease. The simulations show that the transient behavior of the interaction under hypertensive blood pressure is significantly different from the interaction under normal blood pressure. The transient behavior of the blood-flow velocity, and the resulting WSS and the mechanical stress in the aneurysmal wall, are significantly affected by hypertension. The results imply that hypertension affects the growth of an aneurysm and the damage in arterial tissues.     

Risk factors associated with elevated serum pancreatic amylase levels during hemodialysis

Elevated levels of serum pancreatic enzymes are frequently observed in hemodialysis (HD) patients. The complex hemodynamic, biochemical, and physiological alterations in uremia were speculated to cause excessive release of pancreatic enzymes beyond decreased renal clearance. However, hemodynamic factors are seldom explored in this aspect. We performed the study to evaluate the association between intradialytic hemodynamic change and elevated serum pancreatic amylase (SPA). Eighty‐three prevalent HD patients without any clinical evidence of acute pancreatitis underwent pre‐HD and post‐HD blood sampling for serum pancreatic enzyme levels. Demographic, biochemical, and hematological data were collected from patient record review. Hemodialysis information including intradialytic blood pressure changes and ultrafiltration (UF) amount were collected and averaged for 1 month before the blood sampling day. Patients with elevated SPA during the HD session had greater mean systolic blood pressure and mean arterial pressure reduction, greater UF volume, greater pre‐HD blood urea nitrogen and serum creatinine, higher serum phosphorus, lower pre‐HD serum total CO₂, and lower left ventricle ejection fraction (LVEF). Using multivariate linear and logistic regression analysis, the independent predictors of elevated SPA were determined to be mean arterial pressure reduction during HD, mean UF amount, pre‐HD serum total CO₂, and LVEF. Greater blood pressure reduction during HD, greater UF volume, lower pre‐HD serum total CO₂, and lower LVEF were significantly associated with elevated SPA during HD. This suggests that hemodynamic factors contribute to elevated serum pancreatic enzymes in HD patients.     

Residual renal function and arterial stiffness mediated the blood pressure change during interdialytic weight gain in hemodialysis patients

Volume overload is thought to be the main cause of hypertension in dialysis patients. However, the effect of interdialytic weight gain (IDWG) in hemodialysis (HD) patients, which was considered as an increase in extracellular water (ECW), on blood pressure (BP) change, was controversial. Our aim was to examine the changes in hemodynamics and arterial stiffness during IDWG in HD patients and attempt to explore the possible mechanism of diverse BP change. Thirty prevalent patients on HD were enrolled. The height, weight, BP, blood chemistry, volume status assessed by bioelectrical impedance analysis, hemodynamic parameters obtained by echocardiography, and pulse wave velocity (PWV) were collected within 1 hour postdialysis and again just before the next dialysis session. Meanwhile, blood samples were drawn to analyze vasoactive hormones, including renin, angiotensin II, catecholamine, and endothelin. The patients' weights and ECWs during the next predialysis were significantly higher than those during the postdialysis. The BP showed no difference between postdialysis and the next predialysis. There was an obvious increase in cardiac output and decrease in total peripheral resistance as a whole during the next predialysis than that during postdialysis. When patients were divided into the BP increase group (BPI group, 13 patients) and BP decrease group (BPD group, 11 patients) according to the change in systolic BP higher than 10 mmHg, both groups displayed a significant increase in weight, ECW, cardiac output, and a decrease in total peripheral resistance. As compared with the BPI group, patients in the BPD group had significantly lower IDWG, shorter time on dialysis treatment, and higher residual renal function. A decrease in catecholamine and endothelin in the next predialysis was obvious in the BPD group. There was a significant decrease in PWV at the next predialysis in the BPD group while the PWV did not change significantly in the BPI group. Our results showed that the diverse BP change during IDWG was significantly affected by residual renal function, PWV, and vasoactive substances.     

A multilayered wall model of arterial growth and remodeling

Adaptations of large arteries to sustained alterations in hemodynamics that cause changes in both caliber and stiffness are increasingly recognized as important initiators or indicators of cardiovascular risk to high flow, low resistance organs such as the brain, heart, and kidney. There is, therefore, a pressing need to understand better the underlying causes of geometric and material adaptations by large arteries and the associated time courses. Although such information must ultimately come from well designed experiments, mathematical models will continue to play a vital role in the design of these experiments and their interpretation. In this paper, we present a new multilayered model of the time course of basilar artery growth and remodeling in response to sustained alterations in blood pressure and flow. We show, for example, that single- and multi-layered models consistently predict similar changes in caliber and wall thickness, but multilayered models provide additional insight into other important metrics such as the residual stress related opening angle and the axial prestress, both of which are fundamental to arterial homeostasis and responses to injury or insult.     

Integration of clinical and imaging data to predict death in hemodialysis patients

In a prior publication, we demonstrated that a model integrating clinical and simple imaging data predicted the presence and severity of coronary artery calcification in prevalent hemodialysis patients. Herein we report the ability of the same model to predict all‐cause death. We assessed all‐cause mortality in 141 consecutive maintenance hemodialysis patients from two dialysis centers followed for a median of 79 months from enrollment. Patients were risk stratified according to a simple cardiovascular calcification index (CCI) that included patient's age, dialysis vintage, calcification of the cardiac valves, and abdominal aorta. The mean patients’ age was 55 ± 14 years. Abdominal aorta calcification was present in 57% of the patients, and 44% and 38% had aortic and mitral valve calcification, respectively. During follow‐up, 75 deaths (93 deaths per 1000 person‐years) were recorded. The CCI was linearly associated with risk of death, such that the unadjusted hazard risk (HR) increased by 12% for each point increase in CCI (P < 0.001). Further adjustments for age, sex, study center, diabetes mellitus, history of cardiovascular disease, hypertension, congestive heart failure, left ventricular hypertrophy, systolic, and diastolic blood pressure did not substantially change the strength of this association (HR 1.10; 95%CI: 1.00–1.21; P = 0.03). The CCI is a simple clinical model that can be used to risk stratify maintenance hemodialysis patients.     

反应堆压力容器接管安全端焊接残余应力模拟及其焊接参数优化研究

目的 针对反应堆压力容器接管安全端焊接残余应力较大易导致应力腐蚀开裂的问题,探究焊接工艺参数对焊接残余应力的影响,并寻找最佳工艺参数。方法 利用有限元参数化建模方法建立反应堆压力容器接管安全端的三维热-力耦合模型,模拟其焊接过程,研究焊接残余应力的变化情况。采用正交试验设计法分析了焊接电流、焊接速度及层间冷却时间对焊后最大等效应力的影响,建立了焊后最大等效应力与焊接电流、焊接速度及层间冷却时间的二次回归模型,基于该模型利用遗传算法寻优焊接参数。结果 焊接残余应力峰值靠近熔合区位置,残余应力较高,超过了材料的屈服应力;各参数按对焊后等效残余应力峰值的影响由大到小的顺序依次为焊接速度、焊接电流、层间冷却时间。正交试验所得最佳工艺参数如下：焊接电流为610 A,焊接速度为20 mm/s,层间冷却时间为400 s,经遗传算法进一步优化后所得的最佳参数如下：焊接电流为610 A,焊接速度为23 mm/s,层间冷却时间为427 s。通过仿真验证遗传算法优化结果,得到焊接残余应力的峰值为373 MPa,比未优化前减小了44 MPa。结论 优化后的工艺参数有效降低了焊接残余应力,提高了反应堆压力容器接...     

Predicting Interfacial Loads between the Prosthetic Socket and the Residual Limb for Below-Knee Amputees – A Case Study

Abstract:  In this study, an artificial neural network (ANN) was deployed as a tool to determine the internal loads between the residual limb and prosthetic socket for below-knee amputees. This was achieved by using simulated load data to validate the ANN and captured clinical load data to predict the internal loads at the residual limb–socket interface. Load/pressure was applied to 16 regions of the socket, using loading pads in conjunction with a load applicator, and surface strains were collected using 15 strain gauge rosettes. A super-position program was utilised to generate training and testing patterns from the original load/strain data collected. Using this data, a back-propagation ANN, developed at the University of the West of England, was trained. The input to the trained network was the surface strains and the output the internal loads/pressure. The system was validated and the mean square error (MSE) of the system was found to be 8.8% for 1000 training patterns and 8.9% for 50 testing patterns, which was deemed an acceptable error. Finally, the validated system was used to predict pressure-sensitive/-tolerant regions at the limb–socket interface with great success.