血流与剪切应力对血液、血管及血小板的某些影响

1、循环系统有关的流变学概念宏观血液流变学把血液看作为连续介质而不考虑其微观结构，研究血液与血浆的宏观流变性质，即剪切率（shearrate），剪切应力（shearstress）与粘度（viscosity）的关系，以及血管壁上剪切应力分布等。研究循环系统的流变学——剪切与粘度，自然要涉及到支配圆形管道中液体流动的规律。其中最简单的例子是沿着长而直的管子，有恒定流动速度的流动，即所谓“定常流”。由于液体存在粘性或“内摩擦”，所以管子两端要有一定的压力差才能维持液体的常速流动。粘度的概念与液体流动的方式有关。如果一个力作用于液体…     

局部振动对家兔血液流变性的影响

本文用家兔前肢接振法进行局部振动对动物血液流变性影响的实验研究。实验历时2个月。于接振前、接振后1、2月分别测定各组家兔有关血液流变学指标。结果表明,实验组的全血低切比粘度和血细胞压积增高更明显,红细胞电泳时间明显延长(P<0.01)。说明,低频高振幅和高频低振幅的局部振动,均可使血液流变性降低,流动阻力增大,而高频低振幅振动的影啊发生更早更明显。结果还提示局部振动对血液粘度的影响,主要在于血细胞数量及质的变化,而对血浆因素影响较小,并从血液流变学的角度,就振动病的发病机理及亚临床表现进行了初步探讨。     

振动对小鼠体内尾静脉气栓模型影响的实验研究

本文在振动对管道气栓体外模拟实验研究的基础上［１］，对小鼠尾静脉按不同的Ｋ值（注入空气量／体重）注入空气，以形成气栓实验模型，观察Ｋ与存活率之间的关系，以及Ｋ＝５μＩ／ｇ、Ｋ＝－μＩ／ｇ时振动对小鼠尾静脉气栓的影响。结果表明：当Ｋ＝５μＩ／ｇ时，在振动频率为２０Ｈｚ、加速度为１．１ｇ的条件下，振动组的存活率显著高于对照组（Ｐ＜０．０１）。这表明在上述条件下振切对小鼠体内尾静脉注入气体所形成的气栓有明显的消除作用。     

振动减肥中腹壁脂肪的超声检测与力学特征

本文是在研究振动对生物体内物质的耗散作用的基础上，试图利用振动对动物腹壁脂肪进行减脂的探索。通过实验，证实了利用趋声作为手段，可以对动物体内的腹壁脂肪作无创伤活体测量，其误差仅在１０％左右。使用振动对脂肪块得出了疲劳曲线和振动在生物体内传播的衰减曲线。对新鲜离体脂肪块所作振动模拟实验，证明在所使用的频率和振幅的振动作用下，能够迅速使脂肪的厚度消减，根据初步观察，在振动过程中有甘油从脂肪块中溢出，其消减体积的百分之八十为甘油成份，可以认为振动能促使脂肪细胞膜破裂或促使脂肪细胞内的脂滴水解，因此振动有可能成为减肥治疗方案中的一个重要措施。     

淋巴微循环研究进展

尽管早在十六世纪，Aselli就发现了犬的肠系膜上有充满白色液体的管道，切开后流出白色液体。1653年Rudbeck初步建立了淋巴循环的概念[1]．但人们对淋巴系统的认识，与其他系统相比．还有相当大的差距。同样，在二十世纪兴起的微循环领域中，淋巴微循环研究较血液微循环研究要晚得多。一些学者的工作表明．淋巴微循环在正常生命活动和疾病过程中，具有重要的生理和病理生理学意义，因而有良好的发展前景。本文简述淋巴微循环的研究概况。1．概念和组成尚未统一和明确，但可从淋巴系统的功能出发，借鉴血液微循环．得到初步的认识。1993年，…     

扩血管药治疗微循环障碍的实验研究

本实验用激光多普勒微循环血流仪研究了罂粟碱、妥拉苏林对微循环障碍大鼠脏器微循环血液灌流量的影响,结果表明在本实验条件下,罂粟碱对改善以血液粘滞度增高起病的微循环障碍有一定作用,妥拉苏林则起了负作用.     

管壁表面效应的双电层理论

一、前言牛顿液体管内的定常层流,仅依管的几何学形状、液体的粘度以及管两端的压差而定,而与管壁的材料无关,这早已成为流体力学的常识。在流体力学看来,管壁效应不外乎由普通的非滑动条件来表示。但是,也有实验报告提出管内液体的流动,受管壁材料的影响。大约20年前,Copley等人用纤维蛋白在玻璃管内壁涂层,发现用纤维蛋白涂层的玻璃管比没涂层的玻璃管内,血液的流量有明显的增加。还提出经硅化和未经硅化处理的玻璃管内血流量几乎相等。诸如此类的管壁效应,不仅于血液,而且在血浆和血清也有类似发现。也就是     

血液流变学的病理生理意义与心脑血管病（上）

血液流变学的病理生理意义与心脑血管病（上）钱冠清中国医学科学院血液学研究所，邮政编码天津３０００２０长期以来，研究血液的流动规律侧重于研究压力、血管阻力、流量等血液动力学方面的问题，对具有复杂流变性质的血液在血液流动规律中的作用及在生理、病理生理中的...     

浅谈气体栓塞

液体在细管中流动时,如果管中出现气泡,液体流动就要受到阻碍,气泡多了就能堵住管道,使液体不能流动,这一物理现象叫做“气体栓塞”。气体进入血管,形成气体栓塞,危及患者生命,在临床上仍有所见。产生气体栓塞的原因是由于液体表面张力的存在,弯曲液面对其下层的液体作用一附加压强。对于凹的液面,液体内部压强小于液体外部压强,附加压强指向液外,如图一所示。这附加压强对于血管中的一段静止血柱,气泡两     

天模拟失重对人体血液流变性的影响

航天飞行实践证明失重对血液循环系统有明显的影响，可引起心血管功能失调和航天盆血症。在探讨失重性血循环紊乱机理时，研究者匀多着重于研究失重血液动力学的影响，而忽视了血液流变性在其中的作用。我们认为了解失重对血液流变性的影响，对于阐明航天中心血管系统和血液系统变化的机理，制定有效的防护措施都有一定的作用。本实验观察了６名被试者在７天模拟失重实验（－６度头低位卧床）中，血粘度、纤维蛋白原、血细胞压积、红     

Effects of pulmonary gas embolism on circulation and respiration in the dog

Intravenous injection of gas (10-60 ml) causes acute pulmonary embolism, which disappears completely within 10-20 min. Intravenous infusion of gas (1-5 ml min-1) can be continued for a long time. During these infusions a steady state is reached in which pulmonary arterial pressure is increased and cardiac output remains unaltered. This indicates that the degree of embolization has reached a constant level despite the continuous gas infusion. These findings can be explained by a gradual disappearance of the bubbles from the pulmonary circulation. The purpose of this study was to measure the possible excretion of gas from the intravascular gas bubbles into the alveolar air after venous administration. Neon was used as a test gas since its fractional concentration in ambient air is low (0.00018) and it can be detected by gas chromatography with sufficient accuracy. It could be demonstrated that after injection neon was present in the expiration gas. During the steady state of infusion the rate of excretion in the expiration gas appeared to be equal to the rate of infusion. Changes in the pulmonary arterial pressure curve were reflected in the neon wash-out curve. It may be concluded that during pulmonary gas embolism the administered gas is excreted into the alveolar air and that the excretion rate largely depends on the increased pulmonary arterial pressure due to the obstructing bubbles themselves.     

Cardiovascular bubble dynamics

Gas bubbles can form in the cardiovascular system as a result of patho-physiological conditions or can be intentionally introduced for diagnostic or therapeutic reasons. The dynamic behavior of these bubbles is caused by a variety of mechanisms, such as inertia, pressure, interfacial tension, viscosity, and gravity. We review recent advances in the fundamental mechanics and applications of cardiovascular bubbles, including air embolism, ultrasound contrast agents, targeted microbubbles for drug delivery and molecular imaging, cavitation-induced tissue erosion for ultrasonic surgery, microbubble-induced angiogenesis and arteriogenesis, and gas embolotherapy.     

振动对小鼠体内伊文氏篮分布的影响

在以往工作的基础上[1，2]，本文用药理学实验的方法对小鼠尾静脉注入伊文民蓝染料，在振动频率为20Hz，振幅为O．67mm与50Hz，0．44mm的条件下分别刚试了小鼠体内血液和腹腔渗出液中伊文氏蓝在0至2小时内的分布。结果表明：对于血液中伊文氏蓝浓度峰伍，两振动组均比对照组提前0．5小时；对于腹腔渗出液中伊文氏蓝浓度峰值，仅20Hz组比对照组提前0．5小时。从而证实了20Hz组与50Hz组可以改变血液中伊文氏蓝的分布。但是仅频率为20Hz，振幅为0.67mm的振动可以加快腹腔内毛细血管网处微血管内血液的流动。     

Massive paradoxical air embolism in brain occurring after central venous catheterization: a case report

Cerebral air embolism is a rare but fatal complication of central venous catheterization. Here, we report a case of paradoxical cerebral air embolism associated with central venous catheterization. An 85-yr-old man underwent right internal jugular vein catheterization, and became obtunded. Brain MR imaging and CT revealed acute infarction with multiple air bubbles on the side of catheter insertion. The possibility of cerebral air embolism should be considered in patients developing neurological impairment after central venous catheterization, and efforts should be made to limit cerebral damage.     

The alveolar surface network: A new anatomy and its physiological significance

It is generally held that the terminal lung unit (TLU) is an agglomeration of alveoli that opens into the branching air spaces of respiratory bronchioles, alveolar ducts, and alveolar sacs and that these structures are covered by a continuous thin liquid layer bearing a monomolecular film of surfactants at the open gas-liquid interface. The inherent structural and functional instability given TLUs by a broad liquid surface layer of this nature has been mitigated by the discovery that the TLU surface is in fact an agglomeration of bubbles, a foam (the alveolar surface network) that fills the TLU space and forms ultrathin foam films that 1) impart infrastructural stability to sustain aeration, 2) modulate circulation of surface liquid, both in series and in parallel, throughout the TLU and between TLUs and the liquid surface of conducting airways, 3) modulate surface liquid volume and exchange with interstitial liquid, and 4) sustain gas transfer between conducting airways and pulmonary capillaries throughout the respiratory cycle. The experimental evidence, from discovery to the present, is addressed in this report. Lungs were examined in thorax by stereomicroscopy immediately from the in vivo state at volumes ranging from functional residual capacity to maximal volume (Vmax). Lungs were then excised; bubble topography of all anterior and anterolateral surfaces was reaffirmed and also confirmed for all posterior and posterolateral surfaces. The following additional criteria verify the ubiquitous presence of normal intraalveolar bubbles. 1) Bubbles are absent in conducting airways. 2) Bubbles are stable and stationary in TLUs but can be moved individually by gentle microprobe pressure. 3) Adjoining bubbles move into the external medium through subpleural microincisions; there is no free gas, and vacated spaces are rendered airless. Adjacent bubbles may shift position in situ, while more distal bubbles remain stationary. 4) The position and movement of “large” bubbles identifies them as intraductal bubbles. 5) Transection of the lung reveals analogous bubble occurrence and history in central lung regions. 6) Bubbles become fixed in place and change shape when the lung is dried in air; the original shape and movement are restored when the lung is rewet. 7) All exteriorized bubbles are stable with lamellar (film) surface tension near zero. 8) Intact lungs prepared and processed by the new double-embedding technique reveal the intact TLU bubbles and bubble films. Lungs were also monitored directly by stereomicroscopy to establish their presence, transformations, and apparent function from birth through adulthood, as summarized in the following section. Anatomy: Intraalveolar bubbles and bubble films (the unit structures of the alveolar surface network) have been found in all mammalian species examined to date, including lambs, kids, and rabbit pups and adult mice, rats, rabbits, cats, and pigs. Rabbits were used for the definitive studies. 1) A unit bubble occupies each alveolus and branching airway of the TLU; unit bubbles in clusters correspond with alveolar clusters. 2) The appositions of unit bubble lamellae (films) form a network of liquid channels within the TLUs. The appositions are bubble to bubble (near alveolar entrances, at pores of Kohn, and between ductal bubbles), bubble to epithelial cell surface, and bubble to surface liquid of conducting airways. They rapidly form stable Newtonian black foam films (∼7 nm thick) under hydrodynamic conditions expected in vivo. 3) Lamellae of the foam films and bubbles tend to exclude bulk liquid and thus maintain near-zero surface tension. At the same time, the foam film formations—abetted by the constant but small retractive force of tissue recoil—stabilize unit bubble position within the network. 4) Unit bubble mobility in response to applied force increases as liquid accumulates within the network (e.g., in excised lungs or (in extremis) pulmonary edema) to produce reversible foam film transformations (Newtonian black ⇄ common ⇄ thin liquid). 5) Free (bulk) liquid is normally present at Plateau borders of the foam films and over crevices in the epithelial cell surface (the pressure points). 6) Thus, the network is both a continuous liquid circulation within foam film channels and a gas phase within the lamellae of unit bubbles. 7) Both foam films and their constituent bubble films are deformed and destroyed by the usual laboratory methods of lung degassing and tissue processing for light and electron microscopy. However, they can be preserved in the fresh lung by aldehyde fixation alone and by a new double-embedding method. Physiology: 1) Bubble formation and lamellar appositions originate in previously airless units to form, re-form, and repair the network. Formation mechanisms include gas dispersion in liquid and liquid drainage from microdroplets. 2) The essential substrates are components of the lung surfactant system. 3) Both unit and collective (i.e., network) bubbles provide the infrastructural support that sustains alveolar and ductal aeration. 4) Network formation is the indispensable process for transition from the fetal aqueous to the neonatal aerial environment. Surfactant-poor, bubble-free immature lungs fail this transition without therapy (e.g., instillation or aerosol delivery of surfactant to induce bubble formation). 5) The network, from birth to adulthood, modulates gas, liquid, and solute balance at the TLU surfaces. It minimizes liquid content of the gas-permeable lamellae (black films) in the path of respiratory gas exchanges. At the pressure points, it is a reservoir for liquid and solute exchanges within the network and with the septal interstitium and liquid surface of conducting airways. 6) Fluidity of unit structures of the network is a fundamental characteristic of TLU mechanics that underlies the independence of unit structure and consequent local modulation of gas and liquid transfers, the modest force requirement to effect volume change in the normal breathing range, the virtual exclusion of liquid from interfacial lamellae to establish near-zero surface tension in this range, the reentry of liquid at high volumes (>∼80% Vmax), the formation of surpellic films that resist collapse at the lowest volumes, the formation of new bubbles in previously airless units, the formation of new bubbles in units with preexisting bubbles, and the virtually frictionless movement of newly formed bubbles to establish/reestablish the TLU space-filling topography of the network. Anat. Rec. 251:491–527, 1998. © 1998 Wiley-Liss, Inc.     

A kinematic study of the oropharyngeal swallowing of a liquid

Swallowing can become a problem for people with advanced age or laryngeal cancer, especially after surgical resection. The purpose of this study was to quantify the mechanical transport of the bolus through the throat by simultaneously comparing the instantaneous position and velocity of the bolus to the generation of pressure at different sites in the oropharyngeal cavity. Swallows of barium liquid were analyzed using Manofluorography, which simultaneously recorded pressure and barium position through a split screen display. Frame-by-frame analysis was used to describe bolus motion. The graph of head and tail movement showed an hourglass shape with an initial slow, then rapid movement of the bolus head. The peak bolus head velocity averaged 47 cm/s and the maximum acceleration was 460 cm/s². Comparison of pressure traces with the kinematic curves revealed the relative timings of tongue movement, negative suction pressure from the pharyngoesophageal segment and the contraction wave. The magnitude of the gravity and resistance forces were estimated and relative strengths compared. The pharynx can be viewed as a dynamic conduit with changing diameters. The tongue driving force initially drove the bolus. Laryngeal elevation and the pharyngoesophageal segment developed a prebolus negative suction pressure ahead of the bolus. For vertical swallowing of the barium liquid, gravity played the dominant role in head transport. Contraction of the pharyngeal walls served to clear the tail of the bolus from the pharynx. These results aid in the understanding of the physiology of normal swallowing and provide quantitative data for the evaluation of oropharyngeal reconstruction.     

Morphologischer Beitrag zur Frage der Verbrauchscoagulopathie bei Luftembolie

Zusammenfassung Bei der Luftembolie entsteht am Rand der im Blut befindlichen Luftblasen eine Fremdkörperreaktion, an der Leukocyten, vorwiegend aber Thrombocyten in Form z.T. dichter Ansammlungen beteiligt sind. Eine komplette Gerinnung wurde bei den im Experiment und beim Menschen beobachteten Überlebenszeiten nicht beobachtet. Daher wird angenommen, daß die Thrombocytenansammlungen reversibel sind. Die in der terminalen Strombahn gefundenen Entmischungserscheinungen, Ansammlung von Leukocyten, weniger von Thrombocyten, werden als Folge der durch Embolie bedingten Minderdurchblutung angesehen. Mit einer Verbrauchscoagulopathie ist bei Luftembolie nicht zu rechnen.

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A morphologic contribution regarding consumption-coagulopathy in air embolism

Summary In air embolism there is a reaction to be seen around the air bubbles in the blood, especially in the blood of heart chambers. The reaction consists of an accumulation of leucocytes and/or thrombocytes. A complete coagulation of blood is not found. It is concluded, that the accumulation of thrombocytes around the air bubbles is reversible. We regard the phenomena of corpuscular aggregation in the terminal blood stream to be caused indirectly by air embolism and related to the decreased circulation. It is suggested that air embolism does not cause a Verbrauchscoagulopathie.

     

Estimation of the size of air emboli detectable by electrical impedance measurement

Non-invasive detection of air emboli in blood is investigated in vitro using a tetrapolar electrical impedance measurement. A cubic tank with a linear array of four electrodes, spaced approximately 1 cm apart down one side, was filled with 0.2 Sm⁻¹ saline. Bubbles were generated by carbon dioxide gas. Electrical transfer impedance was measured every 8.2 ms at 1.25 MHz. The movement of bubbles was recorded by a video camera, and their sizes and depths from the middle of the array were measured using captured video images. Changes in transfer impedance caused by passage of bubbles were clearly observed and almost identical with those calculated theoretically. Using lead field theory and experimental results, the fundamental limit on the detectable size of bubbles was estimated at the carotid artery, the great saphenous vein and the cephalic vein. The theoretical results showed that a 0.5 mm diameter bubble is detectable at a depth of 5.3 mm, similar to the depth of the great saphenous and the cephalic veins, and a 2.3 mm diameter bubble is detectable at a depth of 21 mm, similar to the depth of the common carotid artery.     

ACUTE DECOMPRESSION SICKNESS

A case of acute decompression sickness presenting severe clinical features was reported. At the time of autopsy, intra-and extravascular air bubbles were found in various organs. Pulmonary fat embolism was also prominent in association with severe circulatory disturbances of the lungs. The spinal cord showed edematous and congestive swelling which was intimately related to the coagulation of blood within the epidural veins that contained innumerable fat droplets. Intravascular fat seemed to be created in and released from the injured adipose tissue, especially that of the bone marrow during decompression and to have acted as an accelerator of intravascular coagulation. The pathophysiological significance of the fat embolism for the development and the progression of decompression sickness is discussed.     

Preparation of microbubble suspensions by co-axial electrohydrodynamic atomization

In this paper we report a novel method, based on co-axial electrohydrodynamic jetting, for the preparation of microbubble suspensions containing bubbles <10 microm in size and having a narrow size distribution. No selective filtration is necessary and the suspensions are produced directly by the process. To demonstrate the method, glycerol was used as the liquid medium, flowing in the outer needle of the co-axial twin needle arrangement and undergoing electrohydrodynamic atomization in the stable cone-jet mode while air flowed through the inner needle at the same time. At zero applied voltage a hollow stream of liquid flowed from the outer needle. When the applied voltage was increased, eventually the hollow stream became a stable cone-jet and emitted a microthread of bubbles, which were collected in a container of glycerol to obtain microbubble suspensions. The size of the microbubbles was measured via optical microscopy and laser diffractometry. Several microbubble suspensions were prepared and characterised and the size distribution was found to be critically dependent on the ratio (n) of flow rates of liquid/air and, in particular the flow rate of the air. At n=1.5, with the flow rate of air set at approximately 1.7 microl/s, a microbubble suspension containing bubbles in the size range 2-8 microm was obtained.