体外反搏下局部狭窄动脉内血液脉动流的一个数学模型

目的研究体外反搏对局部狭窄动脉内血流动力学环境的影响，进而探讨体外反搏对动脉粥样硬化斑块的干预作用。方法设计了一个基于流体动力学理论的数学模型，在特定的空间标系下推导了描述血液脉动流的控制方程，给出了合适的边界条件，并设计了数值算法对模型进行求解。以雄性乳猪的颈动脉为对象，在体测量了动脉的几何参数及反搏前后心动周期内连续的流率、动脉内压和心电。通过将反搏前后的实测数据分别应用到文中建立的数学模型中进行求解。结果得到了反搏前后心动周期里动脉模型内的多种重要的血流动力学量，包括血液流场、速度分布、壁山切应力（WSS）分布等。结论体外反搏能有效提高心动周期内动脉的血流量、提高心动周期内尤其是舒张期的动脉内壁切应力水平及压力梯度、增加动脉局部狭窄段后端回流区的血液回流速度。这些改变对于动脉粥样硬化斑块的发生及发展都有良好的干预作用。     

体外反搏下不同反搏压对动脉内血流动力学环境影响的研究

为了研究体外反搏下不同反搏压对动脉内血流动力学环境的影响，以寻求较佳的体外反搏作用机制，选用了3周龄雄性断乳乳猪四头，进行了慢性体外反搏实验。详细记录了各实验体在基础状态及不同反搏压的体外反搏状态下心动周期里颈动脉内的动态血流动力学数据，包括压力、心电及血流量，进而计算了各种状态下的实验体颈动脉内壁面切应力（WSS）的动态分布。实验及计算结果表明，体外反搏能明显提高心动周期内实验体颈动脉的血流灌注、WSS水平及舒张期压力水平；从提高心动周期的切应力水平出发，反搏压设定为0．03mPa～0．035mPa为佳。另外，体外反搏改变了心动周期里的血流脉动模式，认为血流模式的改变可能对心动周期内的WSS水平有一定的影响作用。     

体外反搏对剪切应力脉动性影响的实验研究

为研究体外反搏治疗心肌血时不同压力对体内各处血管剪切应力脉动性的影响,本研究从六条开胸犬在四种压力情况下实时测量其头臂干、胸主动脉等处的血流量,并计算出各种剪切应力的变化。统计结果表明：不同压力作用下体外反搏使剪切应力脉动性的改变是不同的。     

体外反搏对剪切应力脉动性影响的实验研究

为研究体外反搏治疗心肌缺血时不同压力对体内各处血管剪切应力脉动性的影响 ,本研究从六条开胸犬在四种压力情况下实时测量其头臂干、胸主动脉等处的血流量 ,并计算出各处剪切应力的变化。统计结果表明 :不同压力作用下体外反搏使剪切应力脉动性的改变是不同的。     

影响体外反搏效果的因素

对体外反搏过程采用线性单弹性腔模型及其等效回路进行了讨论。利用连续方程解出了独立的人体总外周阻力R、顺应性C和不受气囊控制的部分外周阻力Ru。利用上述模型评估不同的气囊压力、充气开始时刻和充气维持时间对体外反搏的效果。     

体外反搏对急性缺血犬动脉剪切应力影响的实验研究

为研究体外反搏对心肌缺血的治疗机理。分别测量在正常情况下,缺血１小时,缺血２小时、缺血１小时反反搏１小时、反搏２小时犬头臂干、颈动脉、胸主动脉、腹主动脉处的实时血流量,而后通过数学计算得出各处的实时剪切应力,结论是急性心肌缺血使各处动脉血管剪切应力的脉动性下降;体外反搏的作用可增加各处动脉剪切应力的脉动性。     

基于血液流量波及Womersley 算法的动脉血液脉动流研究

目的 建立相对便利的血流动力学理论研究体系,进行多状态的综合血液脉动流研究。方法 在完全发展脉动流Womerseley算法的基础上引入数值算法,建立基于心动周期里动脉血液流量波的血流动力学求解及分析体系;进而采用理想化的正弦波以及正常生理状态和增强型体外反搏（enhanced external counterpulsation EECP）状态下的在体测量小猪颈动脉血液流量波,进行较全面的血流动力学研究。结果 对各状态下的轴向速度分布、壁面切应力（wall shear stress, WSS）分布、震荡剪切指数（oscillatory shear index, OSI）等重要血流动力学量进行心动周期里的求解分析。流量波波形对WSS分布尤其是OSI水平有一定的影响;EECP作用能明显提升心动周期里的动脉WSS水平尤其是WSS峰值,同时也提高了OSI水平。结论 所建立的基于血液流量波的求解体系能方便有效地应用于血流动力学研究中;EECP作用在生理范围内大幅提升动脉的WSS水平可能是其良好临床效果的最重要生物力学机制之一;作为当前备受关注的血流动力学指标,OSI对于动脉内皮功能的影响作用可能远小于WSS本身,OSI可能并不是理想的预测动脉粥样硬化病变的血流动力学指标。     

体外反搏对剪切应力影响的实验研究

为了研究体外反搏治疗心肌缺血的机理,本研究从六条开胸犬实时测量颈主动脉、头臂干、胸主动脉等处的血流量,并计算出各处的剪切应力的变化。统计结果表明：体外反搏使剪切应力的平均值、变化范围及变化速度都发生了变化,即增加了血流和剪切应力的脉动性。     

体外反搏中的血流分布与反搏方式的仿真研究

据报道体外反搏对身体各部位的缺血性疾病都有一定疗效。但由于受现有实验条件及检测手段的限制,对反搏参数的对症设置缺乏理论依据。为此,我们运用心血管系统的仿真模型,通过大量的仿真实验,对反搏过程中的血流分布进行分析研究,得到了针对不同部位缺血性疾病的理想反搏控制参量。仿真模型的输出结果与现有临床数据相吻合,说明了模型的可信性,同时也表明运用这一模型得到的结果有一定的实用价值。     

冠状动脉狭窄时主动脉内气囊反搏对心内膜下动脉的影响

测量了左冠状动脉狭窄前后，主动脉内气囊反搏时，各项血流动力学参数，并用超声多普勒血流仪测量了室间隔动脉血流的变化。结果表明，当ＩＡＢＰ反搏时，加强了冠脉系统血流的脉动变化，在左冠状动脉主干狭窄时，对心内膜下小动脉的灌注产生不良影响。     

体外反搏对心肌缺血犬血流动力学的影响及内皮素机制的探讨

目的：探讨体外反搏改善心肌缺血犬血流动力学的作用和内皮素机制。 方法： 19只健康杂种犬随机分为对照组、缺血组和反搏组，分别于冠状动脉左前降支结扎前和结扎后60 min、120 min、180 min记录以下指标：①主动脉根部血压；②左心室收缩和舒张末压、+dp/dtmax和-dp/dtmax；③头臂干血流量；④放免法检测血浆和心肌内皮素-1（ET-1）的含量。 结果： 冠脉结扎1 h，缺血组和反搏组犬血压、左心室收缩和舒张功能、头臂干血流量明显低于正常组（P<0.05），而血浆ET-1水平明显高于正常组（P<0.05）。经过体外反搏2 h，反搏组犬的收缩压、舒张压和平均压、左心室收缩和舒张功能、头臂干血流量明显高于缺血组（P<0.05）；而反搏组犬的血浆和心肌ET-1水平明显低于缺血组（P<0.05）。 结论： 体外反搏可改善心肌缺血犬血流动力学指标，其机制可能与降低ET-1的产生有关。     

体外反搏对心肌缺血犬RAS的影响及与血流动力学的关系

目的:探讨心肌缺血与体外反搏(ECP)时犬局部肾素-血管紧张素系统(RAS)和血流动力学的改变以及它们之间的关系。方法:采用冠状动脉结扎法复制犬急性心肌缺血模型,检测缺血及外加反搏时缺血心肌、主动脉、肾脏、肺等局部肾素活性、血管紧张素Ⅱ(AngⅡ)水平和血管紧张素转换酶(ACE)活性,用八导生理记录仪记录血流动力学,分析它们之间的关系。结果:缺血能激活缺血区心肌、主动脉处肾素、ACE和AngⅡ,除缺血区心肌肾素外,ECP抑制缺血区心肌与主动脉处三者。缺血还能激活对循环RAS影响较大的肾脏与肺RAS,反搏对其有一定抑制作用。缺血与反搏时的血流动力学改变和心血管局部AngⅡ水平有关。结论:体外反搏治疗心肌缺血时,局部RAS和血流动力学状态的改变呈相关关系,即体外反搏对血流动力学的改善作用和能抑制局部RAS有关,这可能是它对缺血心肌起保护作用的机制之一。     

磁共振全脑容积动脉自旋标记成像评价单侧颈动脉狭窄患者脑血流动力学的初步研究

目的探讨磁共振全脑容积灌注3D动脉自旋标记（3DASL）成像在单侧颈动脉狭窄或闭塞中的应用价值。方法对连续36例单侧颈动脉狭窄患者（经数字减影血管造影（DSA）验证）行颈部磁共振血管成像（MRA）与头部MR3DASL检查。检验颈部MRA与DSA在狭窄程度上诊断的一致性。以DSA诊断的狭窄程度为标准,将36例患者分成轻、中、重3组,对3DASL所测得的患侧,健侧脑血流量（CBF）比率进行方差分析。以临床症状为标准,将重度狭窄的患者分为有症状组和无症状组,分析2组患侧,踺侧CBF比率的统计学意义。结果颈部MRA与DSA在动脉血管狭窄程度上的诊断,经Kappa行一致性检验,有很强的一致性（Kappa〉0．75,P〈0．05）。轻、中度狭窄组间患侧楗侧CBF比率差别无统计学意义（P〉O．05）;重度狭窄组与轻、中度狭窄组患侧健侧CBF比率差别均有统计学意义（P〈0．01）。重度狭窄患者的有症状组与无症状组患侧,睦侧CBF比率差别有统计学意义（P〈0．01）。结论3DASL技术作为一种安全、无创和可重复的检查方式,配合颈部MRA,对评价单侧颈动脉狭窄患者脑血流动力学状况在临床诊治方面有重要意义。     

Psychosocial effects of enhanced external counterpulsation in the angina patient: a second study

Enhanced external counterpulsation (EECP) is a noninvasive technique that has shown promise in the treatment of ischemic coronary artery disease. Patients undergoing EECP were tested for alterations in psychosocial state associated with treatment. Overall perception of health and quality of life improved with EECP. There was also significant improvement in levels of depression, anxiety, and somatization but no change in levels of anger or hostility. On most measures, change was more significant for subjects who showed objective evidence of resolution of ischemia. Given the known predictive relationship between depression and mortality from cardiac disease, the improvement in depression scores through EECP indicates a finding of potential importance that may warrant further study in future research.     

体外反搏对血管剪切分力频率分量的影响

目的 研究体外反搏治疗心肌缺血时血管对剪切应力各频率分量的影响.方法 对17条开胸犬实时测量其正常情况下、缺血1 h、缺血1 h后反搏1 h、反搏2 h以及正常情况时不同反搏压力下头臂干处的血流量,计算出此处剪切应力的频率分量变化.结果 体外反搏使头臂干处剪切应力的频率分量发生了明显的变化.急性心肌缺血和体外反搏可以使剪切应力的各频率分量发生明显的改变.结论 反搏压力大于一定程度时体外反搏可以明显改变体内血管剪切应力的低频分量.     

体外反搏对血管剪切分力频率分量的影响

目的研究体外反搏治疗心肌缺血时血管对剪切应力各频率分量的影响。方法对17条开胸犬实时测节其正常情况下、缺血1h、缺血1h后反搏1h、反博2h以及正常情况时不同反搏压力下头臂干处的血流量，计算出此处剪切应力的频率分最变化。结果体外反搏使头臂干处剪切应力的频率分量发生了明显的变化。急性心肌缺血和体外反搏可以使剪切应力的各频率分量发生明显的改变。结论反搏压力大于一定程度时休外反搏可以明显改变体内血管剪切应力的低频分量。     

Multiple modeling in the study of interaction of hemodynamics and gas exchange

Circulation plays an important rule in gas exchange. Therefore, there is an interaction between circulation and gas exchange. To understand the dynamic effect of these two physiological systems, a computer simulation model of hemodynamics and gas exchange is established in this work. This model includes two physiological systems, namely the respiratory and circulatory systems. It consists of five parts: the model of gas transport, exchange and storage within the body, the multi-element nonlinear mathematical model of human circulatory system, an alveolar ventilation controller, a cardiac output controller, and a controller of breathing frequency. Model simulations provide results consistent with both dynamic and steady-state responses under hypoxia. Simulation results can reflect the interaction of hemodynamics and gas exchange. Using this model, the changes of pulmonary arterial pressure and right ventricular pressure in high altitude are studied. The optimal mode of breathing extra oxygen using nasal prongs or a facial mask is studied. This model may provide a useful tool to study reaction of hypoxia and the oxygen inhalation mode under hypoxia environments.     

A comparative study of pulsatile arterial hemodynamics in rabbits and guinea pigs.

Pulsatile pressure and flow were measured in the ascending aorta and other arteries of 22 anesthetized rabbits and 16 anesthetized guinea pigs. Pressure/flow relationships were expressed as vascular impedance. Aortic flow waves were almost identical in the two species, but pressure waves were quite different. Reflected pressure waves returned earlier from the periphery in guinea pigs, augmenting pressure during late systole and resulting in relatively high external left ventricular work, an inappropriately larger difference between mean systolic and mean diastolic pressure and absence of any aortic diastolic pressure wave. Values of impedance modulus and phase were similar but differed in the frequency at which maxima and minima occurred. In both species, impedance curves were interpreted to indicate a functionally discrete reflecting site in the lower body whose position corresponded to the region of the aortic bifurcation. In addition, rabbits showed evidence of an upper body reflecting site approximately one-third as far distant from the heart. As in dogs, the arterial system in both species can be represented by an asymmetrical T-shaped model of realistic dimensions.     

The numerical study on specialized treatment strategies of enhanced external counterpulsation for cardiovascular and cerebrovascular disease

Traditional clinical mode of enhanced external counterpulsation is not targeted for different diseases. Specialized strategies in the treatment of enhanced external counterpulsation for coronary heart disease and cerebral ischemic stroke are supposed to be distinguished. The goal of treatment for coronary heart disease is diastolic blood pressure/systolic blood pressure?=?Q?≥?1.2 after counterpulsation, while the goal of treatment for cerebral ischemic stroke is the improvement of mean arterial pressure. A computational lumped parameter model was established for the simulation of hemodynamic effect of enhanced external counterpulsation on two diseases. Vessel collapse was considered during the simulation of counterpulsation. Based on different pressurized and decompressed rate, pressurized moment, pressure duration, and pressure amplitude, different counterpulsation modes were applied to the model and the immediate hemodynamic effects were compared. Results showed that the pressure duration and pressure amplitude had most influence on two diseases. For cerebral ischemic stroke, the longer pressure duration and the higher pressure amplitude of thighs, the higher mean arterial pressure; while for coronary heart disease, the value of Q was highest when the pressure end moment was 0.6 s during a 0.88-s cardiac cycle, and Q had a linear increase in the pressure amplitude of buttocks, but little change with the increase of calves and thighs pressure amplitude. For patients with coronary heart disease, the pressure duration was not supposed to be too long to avoid the increase of systolic blood pressure, and the improvement of pressure amplitude of buttocks could promise a positive treatment effect for coronary heart disease. While for patients with cerebral ischemic stroke, both the long pressure duration of each part and the high pressure amplitude of thighs could result in the systolic blood pressure and diastolic blood pressure have a certain increase, thus promoting the maximum mean arterial pressure and a best treatment.

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Graphical abstract The specialized treatment strategies of EECP for cardiovascular and cerebrovascular disease