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1

Segmentary strategy in modeling of cardiovascular system with blood supply to regional skin

Li Zhongyou, Jiang Wentao, Diao Junjie, Chen Chong, Xu Kairen, Fan Haidong, Yan Fei

Biocybernetics and Biomedical Engineering

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2021

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Vol. 41, no. 4

1505--1517

EN

Objective: The focus of this study is to model the cardiovascular system (CS) involving regional skin blood flow (SBF) to gain new insights into the skin-CS relationship. Methods: A lumped parameter model with a series of electrical components was developed to model the CS involving SBF. Four parts were considered: the heart, arterial circulation, microcirculation (including the skin and other tissues), and the venous system. The model was validated based on previous publications. Additionally, the body surface was divided into seven blocks replaced by lumped resistances in this model, including the head, upper limbs and neck, chest and back, anterolateral abdomen, posterior abdomen, lower limbs, and buttocks. The SBF of each block was described using a weighted average method (relative ratio of cutaneous blood perfusion and regional body surface area) Results: Cardiodynamics characterized the properties of cardiac cycles, including isovolumic contraction, accelerated ejection, decelerated ejection, isovolumic diastole, and filling phases. Blood flow and pulse pressure in the arterial trunk declined and increased, respectively, from the aorta root to the distal portion, exhibiting normal cardiovascular properties. Accordingly, the blood pressure of the arterial branches attached to the arterial trunk also satisfied normal physiological characteristics; the blood flow of all the arterial branches exhibited good agreement with previous studies. Additionally, the modeled SBF of each region was consistent with the data from the weighted average method. Conclusion: This model effectively demonstrates the normal properties of the CS that involves regional SBF and may be promising in the prediction of the skin-CS relationship.

2

Numerical study on flow topology and hemodynamics in tortuous coronary artery with symmetrical and asymmetrical stenosis

Song Jianfei, Kouidri Smaine, Bakir Farid

Biocybernetics and Biomedical Engineering

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2021

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Vol. 41, no. 1

142--155

EN

Tortuosity in coronary artery has been found to be greatly related to the potential sites of stenosis in these last years. Many investigations have been carried out based on the tool of Computational Fluid Dynamics (CFD) mainly focusing on the influences of curved artery in blood flow. Within the limited investigations of coupling between stenosis and tortuosity, the stenosis has been considered to be located at the tortuous segment. However, with recent clinical studies, the case of stenosis occurred at non-tortuous segment before tortuosities has been confirmed which has not been paid enough attention yet. Therefore, the present study aims to investigate the disturbed streamlines and hemodynamics in curved and spiral artery considering symmetrical and asymmetrical stenosis upstream these tortuosities. Different stenosis severities, pulse rates and distances between stenosis and tortuosity as controlling parameters have been studied. The distribution of time averaged wall shear stress (TAWSS) and streamlines through tortuous segment have been displayed in order to determine the potential disease sites. Artery surface of TAWSS below critical value has been quantified as well to evaluate the risks of atherosclerosis. The results reveal that larger artery surface of TAWSS below critical value generally goes with smaller pulse rate, larger stenosis severity and distance between stenosis and tortuosity both for curved and spiral artery. However, exceptions were found in the cases of distance of 6 mm in curved artery with symmetrical stenosis and stenosis severity of 50% in spiral artery. Moreover, the spiral tortuosity tends to suppress the potential risks of atherosclerosis compared to curved tortuosity.

3

The effect of stenosis rate and Reynolds number on local flow characteristics and plaque formation around the atherosclerotic stenosis

Chen Xueping, Zhan Yiyi, Fu Yi, Lin Jiangguo, Ji Yanru, Zhao Chengbi, Fang Ying, Wu Jianhua

Acta of Bioengineering and Biomechanics

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2021

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Vol. 23, no. 1

135--147

EN

Purpose: Atherosclerosis causes plaque to build-up in arteries. Effect of the specific local hemodynamic environment around an atherosclerotic plaque on the thrombosis formation does not remain quite clear but is believed to be crucial. The aim of this study is to uncover the flow effects on plaques formation. Methods: To study the mechanically regulated plaque formation, the flow fields in artery blood vessels with different stenosis rates at various Reynolds numbers were simulated numerically with the two-dimensional axisymmetric models, and the hemodynamic characteristics around the plaque were scaled with stenosis rate and Reynolds number. Results: The results showed that increases of both Reynolds number and stenosis rate facilitated the occurrence of flow separation phenomenon, extended recirculation zone, and upregulated the maximum normalized wall shear stress near the plaque throat section while downregulated the minimal normalized wall shear stress at the front shoulder of plaque, as it should be; in the atherosclerotic plaque leeside of the recirculation zone, an obvious catch bond region of wall shear stress might exist especially under low Reynolds number with stenosis rate smaller than 30%. This catch bond region in the plaque leeside might be responsible for the LBF (low blood flow)-enhanced formation of the atherosclerotic plaque. Conclusions: This work may provide a novel insight into understanding the biomechanical effects behind the formation and damage of atherosclerotic plaques and propose a new strategy for preventing atherosclerotic diseases.

4

Numerical insights into the determinants of stent performance for the management of aneurysm with a visceral vessel attached

Li Zhongyou, Chen Chong, Chen Yu, Wang Zhenze, Jiang Wentao, Tian Xiaobao

Acta of Bioengineering and Biomechanics

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2021

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Vol. 23, no. 2

41--53

EN

Purpose: As the factors affecting the efficacy of the bare-metal stent in the treatment of aneurysm with a visceral vessel attached were not fully understood, we aimed to discuss the effects of different characteristics of the stent on the hemodynamics and flexibility in the treatment of the aneurysm. Methods: Single-layer (with different strut widths) and multi-layer (with a different number of struts) stent models divided into three porosity groups, with porosities of 72.3, 60.5, and 52.4%, were modeled for a comparison of their hemodynamic isolation and flexibility performance via computational fluid dynamics and finite element methods. Results: The velocity and timeaveraged wall shear stress decreased more noticeably with multi-layer stent interventions. A higher oscillatory shear index and relative residence time occurred at the aneurysmal sac wall after multi-layer stents were employed. Time-averaged wall shear stress on the aneurysmal wall decreased with an increase in the number of struts or a decrease in pore size, but oscillatory shear index and relative residence time increased as the number of struts increased or the pore size decreased. Besides, all stents affect the branch patency slightly. In the bending test, when the porosity exceeded 60.5%, multi-layer stents were more flexible. Conclusion: The number of struts or pore size of stent dominated the isolation in the management of the aneurysm and affected the flexibility significantly when the porosity was below 60.5%. These findings may contribute to the special design of the stent in the treatment of such types of aneurysms.

5

Numerical investigation of renal artery hemodynamics based on the physiological response to renal artery stenosis

Andayesh Mohammad, Shahidian Azadeh, Ghassemi Majid

Biocybernetics and Biomedical Engineering

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2020

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Vol. 40, no. 4

1458--1468

EN

Renal Artery Stenosis (RAS) is the narrowing of renal arteries, most often caused by atherosclerosis or fibromuscular dysplasia. Possible complications of renal artery stenosis are renovascular hypertension and renal ischemia. The goals of the current study were to investigate the physiological response to RAS and effects of the artery and stenosis geometry, quantify the performance of arterial pressure regulation mechanisms respect to stenosis severity, and predict future conditions of renal artery stenosis. Commercial software based on the finite volume method was utilized to solve governing equations. To determine the physiological response, simulations were done for two cases, with and without the involvement of arterial pressure regulation mechanisms. The numerical method was validated by experimental data, which obtained from two prototypes. Results showed that systemic blood pressure was increased as the physiological response to RAS; hence, the flow rate of the renal branch was improved and renal ischemia was relatively prevented. Furthermore, results demonstrated that the stenosis percentage and artery diameter were dominant geometric parameters on the hemodynamics and other parameters had negligible effects. It was demonstrated that 50% of stenosis was the critical point for the interaction of RAS and arterial pressure regulation mechanisms. Finally, wall shear stress was analyzed on an image-based geometry, and it was estimated and expected that acute renal artery stenosis was progressive and pathogenesis of arterial diseases.

6

Numerical and experimental analysis of balloon angioplasty impact on flow hemodynamics improvement

Tomaszewski Michał, Sybilski Kamil, Małachowski Jerzy, Wolański Wojciech, Buszman Piotr P.

Acta of Bioengineering and Biomechanics

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2020

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Vol. 22, no. 3

169--183

EN

Purpose: The paper focuses on the numerical and experimental evaluation of the fluid flow inside chosen fragments of blood vessels. In the first stage of the study, the experimental tests were conducted using a research test stand, designed to be used in this evaluation. The study evaluated the blood flow through a silicone vessel with an implanted coronary stent. Methods: The PIV method was used in order to visualize the flow vectors inside a silicone vessel. Deformed vessel geometry implemented for computational fluid dynamics purposes was obtained owing to a non-linear simulation of the stent expansion (angioplasty process) in a silicone vessel. Additionally, a vessel model with a statistical 55% area stenosis and an irregular real vessel with an atherosclerotic plaque were also subjected to analysis from the hemodynamic flow point of view. A vessel with a statistical stenosis was also used to simulate the angioplasty process, which resulted in obtaining a flow domain for the vessel with an atherosclerotic plaque after the stent implantation. Results: For each case, distributions of parameters such as OSI or TAWSS were also analyzed and discussed. The areas of low TAWSS values appear close to the stent struts. Conclusions: Stents with increased diameters, compared to the normal vessel diameter, create a higher risk of occurrence of the areas with low WSS values. Excessive stent deformation can cause inflammation by injuring the vessel and can initiate the restenosis and thrombotic phenomena through the increased vessel diameter.

7

Wpływ składowej magnetycznej pola elektromagnetycznego 50 Hz na zmiany hemodynamiki organizmu człowieka

Jakubaszko J., Wróblewski Z ., Sztafrowski D.

Przegląd Elektrotechniczny

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2014

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R. 90, nr 2

238--241

PL

Referat prezentuje wyniki badań wpływu składowej magnetycznej pola elektromagnetycznego 50 Hz na zmiany hemodynamiki organizmu człowieka przeprowadzone na zaprojektowanym w Instytucie Elektroenergetyki Politechniki Wrocławskiej stanowisku badawczym generującym pole magnetyczne 50 Hz o wartościach oraz homogeniczności zbieżnej z polami generowanymi przez obiekty elektroenergetyczne. Badania przeprowadzone zostały we współpracy z Katedrą Medycyny Ratunkowej Uniwersytetu Medycznego we Wrocławiu.

EN

The results of tests on influence of magnetic field with variable frequency at 50 Hz on the human cardiac chemo-dynamic processes, conducted on testing stand constructed at the Institute of Electrical Power Engineering, Wroclaw University of Technology are presented. The unique research stand generates 50 Hz magnetic field of homogeneity parameters coincident with the fields generated by electrical power facilities. The presented study was carried out in collaboration with the Medical University in Wroclaw.

8

A methodological review of data mining techniques in predictive medicine: An application in hemodynamic prediction for abdominal aortic aneurysm disease

Paramasivam V., Yee T. S., Dhillon S. K., Sidhu A. S.

Biocybernetics and Biomedical Engineering

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2014

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Vol. 34, no. 3

139--145

EN

Modern clinics and hospitals need accurate real-time prediction tools. This paper reviews the importance and present trends of data mining methodologies in predictive medicine by focusing on hemodynamic predictions in abdominal aortic aneurysm (AAA). It also provides potential data mining working frameworks for hemodynamic predictions in AAA. These frameworks either allow the coupling between a typical computational modeling simulation and various data mining techniques, using the existing medical datasets of real-patient and mining it directly using various data mining techniques or implementing visual data mining approach to already available computed results of various hemodynamic features within the AAA models. These approaches allow the possibility of statistically predicting rupture potentials of aneurismal patients and ideally provide an alternate solution for substituting tedious and time-consuming computational modeling. Prediction trends of patient-specific aneurismal conditions via mining huge volume of medical data can also speed up the decision making process in real life medicine.

9

Badania modelowe efektów reodynamicznych w rozgałęzieniach przewodów wzorowanych na układach biologicznych (problem stenozy)

Sławomirski M. R.

Prace Instytutu Mechaniki Górotworu PAN

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2010

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Vol. 12, no. 1-4

237--251

PL

Rozgałęzienia naczyń krwionośnych występują powszechnie w organizmach ludzkich i zwierzęcych, zarówno w systemach naczyń tętniczych jak i żylnych. Obraz przepływu w obszarach bifurkacji oraz w ich sąsiedztwie daleki jest od regularnego profilu Poisseuille’a. W rozgałęzieniach istotną rolę odgrywają zjawiska w warstwie granicznej, a efekty typu oderwania i przepływu recyrkulacyjnego modyfikują w sposób istotny rozkłady prędkości, ciśnienia i wirowości. Z medycznego punktu widzenia obszary rozgałęzień są dość ‘wrażliwe’ ze względu na występujące w nich często zjawiska o istotnym znaczeniu klinicznym. W sąsiedztwie punktów bifurkacji zaobserwowano powstawanie i rozwój złogów atherosklerotycznych (tzw. atheromatic plaque) zbudowanych m.in. z lipoprotein niskiej gęstości (low density lipoproteins – LDL) pierwotnie zawartych w osoczu krwi. Istnieje w tej materii przekonująca dokumentacja medyczna w odniesieniu do naczyń wieńcowych i mózgowych, znane są też doniesienia dotyczące naczyń innych narządów, np. wątroby czy nerek. Ruch płynu w sąsiedztwie rozgałęzień ma charakter przepływu spowalniającego (ang. decelerating flow). Zachowanie się warstwy granicznej jest wówczas opisane nieliniowym równaniem różniczkowym III rzędu, które rozwiązać można zmodyfikowaną metodą strzałów (ang. schooting metod). Równanie to posiada w pewnych obszarach rozwiązania regularne, w innych występują rodziny konkurencyjnych rozwiązań, z których tylko niektóre posiadają sens fizykalny. Jako kryterium eliminacji rozwiązań ‘niefizykalnych’ przyjęto obraz rotacji prędkości. W sensie matematycznym oderwanie warstwy granicznej jest konsekwencją osobliwości opisujących jej zachowanie rozwiązań równań samopodobnych. Wyznaczone numerycznie obszary oderwania wykazują daleko idącą korelację z rejestrowanymi klinicznie strefami tworzenia się złogów atherosklerotycznych. Doprowadziło to autora do sformułownia wniosku, że tworzenie atheromy jest ściśle związane z uszkodzeniem endothelium (tj. specjalnej pojedynczej warstwy komórek wyścielającej wszystkie naczynia krwionośne organizmów ludzkich i zwierzęcych) w związku z nadmiarem wirowości w pobliżu ścianki, oderwaniem warstwy granicznej i rozwojem przepływu recyrkulacyjnego w podobszarze zmniejszonych prędkości w sąsiedztwie rozgałęzienia. Ponieważ wspomniane zjawiska reodynamiczne występują głównie we wstępnych odcinkach bocznych odgałęzień dużych tętnic, należy się tam spodziewać postępującej stenozy, tj. stopniowej redukcji światła naczyń, co klinicznie przejawia się w postaci niedokrwistości narządowej, a nawet zawałów, w szczególności w odniesieniu do pacjentów z grup wysokiego ryzyka dla których charakterystyczne są wysoki poziom LDL, nadciśnienie tętnicze oraz palenie tytoniu.

EN

Branch points of vessels constituting circulatory system are encountered commonly in human and animal organisms. The flow paterns in bifurcation zones and in their vicinity differ significantly from the regular Poisseuille motion. In branch zones boundary layer effects as separation and recirculating flow are crucial, and they modify significantly the distribution of velocity, pressure and vorticity. From the medical point of view branch zones are ‘sensitive’ owing to significant clinical phenomena. In the bifurcation zones and in their vicinity the infiltration of low density lipoproteins (LDL) under the endothelial layer, and the development of the atheromatic plaque have often been observed. There are many reports about clinical observations concerning this matter, especially those referring to renal and celebral arteries. Fluid motion in the branch zones is represented by decelerating flow. The behaviour of the boundary layer is then described by non-linear differential equation which may be solved by means of the modified schooting metod. In the certain zone the equation posesses the regular solution; in another zone there exist families of concurrent solutions, and only rare of them are physically acceptable. The distribution of vorticity has been applied as the final criterion of acceptability of solutions. From the mathematical standpoint the separation of the boundary layer is implied by singularities of self-similar solutions of differential equations describing fluid motion. The separation zones determined as the result of numerical simulations are co-related with the location of atherosclerotic plaques. Consequently the author has formulated the thesis according to which the formulation and dvelopment of atherosclerotic phenomena is related to the damage of endothelial cells and implied by the separation of boundary layer, surplus of vorticity, and recirculating flows in deceleration flow zones in the vicinty of bifurcations. The rheodynamic phenomena mentioned here are observed near the inlet of secordary arteries, and consequently, the stenosis in those zones may be deveoped, especially for the patients of high risk group (high LDL level in blood, blood overpressure, smoking).

10

Modelling of hemodynamics in 3D bypass models

Vimmr J., Jonasova A.

Modelling and Optimization of Physical Systems

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2010

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z. 9

87--92

EN

The study is divided into two parts. The first one deals with the modelling of non-Newtonian effects in occluded femoral bypass considering steady blood flow. The second part is devoted to the analysis of pulsatile Newtonian blood flow in stenosed coronary bypass applying realistic inlet flow rates. The bypass models are assumed to be idealized and complete, i.e. the native artery and the bypass graft are modelled as tubes with both proximal and distal parts. The governing equations are solved numerically with explicit and implicit schemes formulated in the sense of the finite volume method using developed in-house software.

CS

Tato studie je rozdělena na dvě části. První se zabývá modelováním nenewtonských efektů ve femorálním bypassu pří uvažováni ustáleného proudění krve. Druhá část je věnována analýze pulzujícího proudění krve jakožto newtonské kapaliny v koronárním bypassu. Matematický model je řešen pomocí explicitních a implicitních schémat formulovaných ve smyslu metody konečných objemů a za použití vlastního vyvinutého softwaru.

11

Biventricular pacemaker synchronization: A numerical cardiocirculatory model application to reproduce in vivo data

Di Molfetta A., De Lazzari C., Ferrari G., Moscariello F., Aguzzi G., Fresiello L., Darowski M., Trivella M. G., Alessandri N

Biocybernetics and Biomedical Engineering

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2010

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Vol. 30, no. 1

3-15

EN

Cardiac Resynchronization Therapy (CRT) seems to be the most encouraging treatment to limit the damages of ventricular remodelling in patients with moderate-severe cardiac insufficiency. Mathematical modelling of the cardiovascular system is a tool potentially useful to understand how the Biventricular Pacemaker (BPM) must be synchronised during CRT. In this work a computer simulator reproduces clinical data measured, on different patients affected by asynchronous ventricular contraction, before and after CRT. Three patients, affected by asynchronous ventricular contraction, were monitored before and after biventricular stimulation through CRT. Measured and simulated data were compared. Results show that the software simulator can well reproduce in vivo data. Besides, simulated results from BPM together with drug therapy are in accordance with literature data. Numerical modelling could be a useful tool to optimize the BPM synchronization.

12

Ocena odruchu z baroreceptorów tętniczych po zabiegu kriostymulacji ogólnoustrojowej u osób zdrowych

Zalewski P., Klawe J., Tafil-Klawe M., Buszko K., Panowicz I.

Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna

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2010

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Vol. 16, nr 1

38-43

PL

Krioterapia ogólnoustrojowa {whołe-body cryotherapy - WBC) jest powszechnie stosowaną metodą terapeutyczną w leczeniu dysfunkcji układu ruchu lub układu nerwowego oraz w odnowie biologicznej. Celem niniejszych badań była ocena zmian odruchu z baroreceptorow tętniczych pod wpływem krioterapii ogólno-ustrojowej u osób zdrowych. Badaniami objęto grupę 25 zdrowych mężczyzn, którzy przebywali 3 minuty w kriokomorze w temperaturze około -110 stopni C. Poza parametrami hemodynamicznymi ocenie poddano parametry oceniające reaktywność baroreceptorów tętniczych metodą sekwencyjną, m.in.: up-events slope mean - w zakresie sekwencji narastających, down-events slope mean - w zakresie sekwencji malejących, total events slope mean - wartość całkowita seltwencji. Rejestrację parametrów hemodynamicznych przeprowadzono dwukrotnie: przed (01) i po (02) po zabiegu kriostymulacji ogolnoustrojowej za pomocą systemu Task Force Monitor firmy CNSystems. Badania wykonano zgodnie z kryteriami oceny czynnościowej autonomicznego układu nerwowego. Po ekspozycji na temperatury kriogeniczne, poza zmianami parametrów hemodynamicznych, zarejestrowano istotny wzrost czułości odruchu z baroreceptorów tętniczych, zarówno w zakresie sekwencji malejących, jak i narastających. Wzmożona odpowiedź z baroreceptorów tętniczych na skutek działania temperatur kriogenicznych najprawdopodobniej była efektem wzmożonego powrotu żylnego i poziomu wypełniania komór, co skutkowało również zwiększoną objętością wyrzutową serca (S V - stroke volume).

EN

Whole-body cryotherapy (WBC) is a one of well known physical therapy methods. The assessment of arterial baroreceptors activity after exposure to the whole-body cryotherapy in healthy subject, is presented. Twenty five healthy subjects were exposed to 3-niinute whole-bo-ćy cryotherapy procedure (-110 degrees C). The following parameters were recorded: Up-Events Slope Mean, Down-Events Slope Mean, Total Events Slope Mean. Subjects were examined twice: before (01) and after (02) cryotherapy. The Task Force Monitor was used to measure beat-to-beat hemodynamic parameters during supine rest. Examination was made according to standards of autonomic nervous system assessment. Whole-body cryotherapy caused significant increase of arterial baroreceptors activity, both in decreasing sequences Down-Events Slope Mean and increasing sequences Up-Events Slope Mean. Boosted arterial baroreceptors response was a result of increased volume of venous return and ventricles volume, włiich caused an increased level of stroke volume (SV).

13

Zmiany wybranych parametrów hemodynamicznych po zabiegu kriostymulacji ogólnoustrojowej u osób zdrowych

Zalewski P., Tafil-Klawe M., Buszko K., Lewandowski A., Panowicz I.

Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna

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2009

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Vol. 15, nr 3

209-214

PL

Ekspozycja organizmu na działanie bodźca termicznego w za-kresie temperatur kriogenicznych wywołuje reakcje fizjologiczne w układzie krążenia. Celem badań była ocena zmian parametrów hemodynamicznych, zachodzących pod wpływem krioterapii ogólnoustrojowej u osób zdrowych. Badaniami objęto grupę 25 zdrowych mężczyzn; którzy przeby-wali jeden raz w kriokomorze w temperaturze około -110 oC przez 3 minuty. Ocenie poddano następujące parametry: inter-wały R-R (RRI), częstość akcji serca (HR), ciśnienie krwi skurczowe (sBP), ciśnienie krwi rozkurczowe (dBP), ciśnienie krwi średnie (mBP), objętość wyrzutową serca (SV), wskaźnik skurczowy serca (SI), objętość minutową serca (CO), wskaźnik sercowy (CI), całkowity opór naczyniowy (TPR), wskaźnik całkowitego oporu naczyniowego (TPRI). Rejestrację parametrów hemodynamicznych przeprowadzono dwukrotnie za pomocą systemu Task ForceŽ Monitor firmy CNSystems: przed (01) i po (02) po zabiegu kriostymulacji ogólnoustrojowej. Badania wykonano zgodnie z kryteriami oceny czynnościowej autonomicznego układu nerwowego. W efekcie ekspozycji na działanie temperatur kriogenicznych nastąpiło istotne zmniejszenie częstości pracy serca (HR) oraz zwiększenie objętości wyrzutowej i wskaźnika skurczowego serca (SV, SI). Wartości ciśnienia skurczowego (sBP), rozkurczowego (dBP), średniego (mBP) oraz wskaźnika sercowego (CO, CI) nie wykazały istotnych statystycznie zmian, podobnie jak wartość całkowitego oporu naczyniowego (TPR, TPRI). Zakres zmian powyższych parametrów wskazuje na wystąpienie wzrostu obciążenia wstępnego bez obciążenia następczego serca po zabiegu krioterapii ogólnoustrojowej.

EN

Whole-body cryotherapy (WBC) causes various physiological reactions, affecting mainly the peripheral and central part of circulatory system. The aim of this study was to assess the hemody-namic changes after whole-body cryotherapy in healthy subjects. Twenty five healthy subjects were exposed for 3 minutes once to whole-body cryotherapy (WBC) in the temperature of -110 oC. The recording of biological signals included: R-R intervals (RRI), heart rate (HR), systolic blood pressure (sBP), diastolic blood pressure (dBP), mean blood pressure (mBP), stroke volume (SV), stroke index (SI), cardiac output (CO), cardiac index (CI), total peripheral resistance (TPR), total peripheral resistance index (TPRI). Subject were investigated twice: before (01) and after (02) cryotherapy exposition. The Task ForceŽ Monitor was used to measure beat-to-beat hemodynamic parameters during the supine rest. Examination was made according to standards of autonomic nervous system assessment. Whole-body cryotherapy (WBC) decreased heart rate (HR) and increased stroke volume and stroke index (SV, SI). The values of systolic (sBP), diastolic (dBP), mean (mBP) pressures remained unchanged. None of significant differences in cardiac output (CO), cardiac index (CI) and total peripheral resistance (TPR) were found. The hemodynamic changes indicate that whole-body cryotherapy (WBC) influences the increase of preload without increasing the afterload of the heart.

14

Metoda grafów wiązań w zastosowaniu do opracowania szczególnego obwodu elektrycznego

Muc A., Matulewicz W., Retkowski M.

Przegląd Elektrotechniczny

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2008

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R. 84, nr 9

173-178

PL

Grafy wiązań wykorzystano do odwzorowania krwiobiegu nerki. Zaproponowany model, uwzględnia również odcinek tętnicy głównej oraz, w uproszczeniu, dystrybucję krwi do pozostałych segmentów krwiobiegu. Opisanie zjawisk przepływu krwi w naczyniach krwionośnych za pomocą grafów wiązań pozwala w łatwy sposób przejść do modelu w postaci obwodu elektrycznego. Sprowadzenie problemu dystrybucji krwi do modelu elektrycznego umożliwia zastosowanie sieciowych metod analizy obwodów i uproszczenia analizy zjawisk hemodynamicznych.

EN

The bond graph to modelling of the kidney blood circulation system was applied. Main artery and system of vessels of abdominal cavity in model were included as well. The created model is easy to change into the equivalent electric circuit. By applying electric circuit to modelling the blood circulation system the networks methods of electric circuits analysis are possible to use. Simplification of analysis of the hemodynamics phenomena is main advantage of this approach.

15

Influence of junction angle on hemodynamics in a bypass model

Vimmr J., Jonasova A.

Modelling and Optimization of Physical Systems

|

2007

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z. 6

153--156

EN

The problem of steady laminar flow of an incompressible Newtonian fluid through an idealized 2-D bypass model with a stenosed coronary artery is solved using the finite volume approach of the MacCormack and Runge-Kutta schemes. The bypass model includes proximal and distal parts of the artery together with end-to-side graft. The changes of hemodynamics are investigated with three different junction angles (ɑ = 20°,45°,70°) between the graft and the artery. The velocity and wall shear stress distributions obtained using both numerical schemes for all three cases are analyzed and compared with each other.

16

A newly-designed myocardial assist device using a sophisticated shape memory alloy fibre

Shiraishi Y., Yambe T., Sekine K., Ogawa D., Nagatoshi J., Itoh S., Park Y., Uematsu M., Sakata R., Wada Y., Saijo Y., Higa M., Hori Y., Liu H., Wang Q., Konno S., Kuwayama T., Olegario P., Tanaka A., Masumoto N., Ibuki R., Maruyama S., Okamoto E., Fujimoto T., Yoshizawa M., Umezu M., Imachi K., Nitta S.-I., Sasada H., Tabayashi K., Homma D.

Biocybernetics and Biomedical Engineering

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2007

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Vol. 27, no. 1-2

147-154

EN

Recently, the ventricular assist devices are widely applied for a surgical treatment of the final stage of severe heart failure as the bridge to heart transplantation or the destination therapy. However, it was anticipated that the artificial components in the ventricular assist devices might cause the problems concerning thrombosis and infection. As heart failure involves the decrease in myocardial contractile function, the mechanical assistance by using an artificial myocardium might be effective. In this study, the authors developed a mechano-electric artificial myocardial assist system (artificial myocardium), which is capable of supporting natural contractile function from the outside of the ventricle.

17

Zastosowanie elektrycznego schematu zastępczego do analizy zmian przepływu krwi w nerce

Matulewicz W., Muc A., Retkowski M.

Przegląd Elektrotechniczny

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2006

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R. 82, nr 6

63-65

PL

Podano podstawę przedstawiania krwiobiegu w postaci przepływu prądu w zastępczym obwodzie elektrycznym. Zasady te zostały zastosowane do odwzorowania krwiobiegu nerki. Istotą badań symulacyjnych z zastosowaniem obwodu elektrycznego jest opracowanie sposobu identyfikacji przyczyn zmian przebiegu prądu, który odwzorowuje przebieg krwi. Jest to bardzo ważne zagadnienie w przypadku diagnostyki nerki po transplantacji umożliwiającej wykrycie zmian stanu krwiobiegu nerki.

EN

Basic principles of showing the blood circulation in the form of current flow in the equivalent circuit were described. These principles have been employed formodeling of the kidney blood circulation. The essence of simulation research with using the electric circuit is a method of the identification of reasons for changes in the current waveform, which the course of blood is copying. This problem is very important in the case of the kidney diagnostic after the transplantation.

18

A family of circulatory computer models developed to analyse and predict physiopathological events: applications to mechanical circulatory and ventilatory assistance

De Lazzari C., Darowski M., Ferrari G., Tosti G.

Biocybernetics and Biomedical Engineering

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2006

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Vol. 26, no. 2

25-37

EN

The aim of this work is to present a family of circulatory computer models suitable to be used for analysis and prediction. Circulatory models can reproduce many circulatory phenomena for several practical applications referable to the main functional sectors of analysis and prediction. Of course, the models are different in relation to the phenomena to be represented. An important issue is the possibility to represent the artero-ventricular interactions and the effects, in different ventricular conditions, of the influence of mechanical ventilatory and circulatory assistance. In these models of human cardiovascular system, the influence of mechanical ventilation was introduced, changing the thoracic pressure to positive values. In the work, two different applications were presented: in the first one the trends of the haemodynamic variables were analysed when mechanical ventilation of the lungs was applied for different values of mean intrathoracic pressure. In the second application, were presented the effects on the haemodynamic variables of the left ventricular assist device (in particular arotary blood pump).

19

Rheological models of human blood as a non-Newtonian fluid

Wojnarowski J., Mirota K.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no 2

413-421

EN

One of the most important problems of model hemodynamics is the descriptions of the rheological properties of the flowing blood. In this work, two basic classes of a hemorheology models have been analysed. The first one considers human blood as a non-Newtonian and time-independent fluid. However, the dynamical formation of its time-dependent collective structure leads to a viscoelastic and tixotropic blood response. In consequence, this study presents a second class of hemorheology model, considering blood as a fluid thinning and thickening with time.

20

The influence of ventilatory support on coronary flow and oxygen consumption in different circulatory conditions

De Lazzari C., Darowski M., Ferrari G., Mimmo R., Guaragno M., Tosti G.

Biocybernetics and Biomedical Engineering

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2003

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Vol. 23, no. 1

103-110

EN

The aim of this work is to predict the influence of mechanical ventilation on cardiac output, coronary flow and left ventricular myocardial oxygen consumption in different circulatory conditions. To study this interaction we used a computer simulator of human cardiovascular system in which lumped parameters models were used to reproduce the circulatory phenomena in terms of pressure and volume relationships. Variable elastance models reproduce the Starling's law of the heart, for each ventricle. In the study the left ventricular elastance assumed two different values. Symetric arterial resistance was changed during the simulation. The influenece of mechanical ventilation was introduced by positive mean thoracic pressure. Positive thoracic pressure, changes of peripheral resistance and different ventricular elastance values have a significant influence on cardiac output, coronary flow and myocardial oxygen consumption.