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EN
Objectives: Our goal is to develop a double lumen cannula (DLC) for a percutaneous right ventricular assist device (pRVAD) in order to eliminate two open chest surgeries for RVAD installation and removal. The objective of this study was to evaluate the performance, flow pattern, blood hemolysis, and thrombosis potential of the pRVAD DLC. Methods: Computational fluid dynamics (CFD), using the finite volume method, was performed on the pRVAD DLC. For Reynolds numbers <4000, the laminar model was used to describe the blood flow behavior, while shear-stress transport k-ω model was used for Reynolds numbers >4000. Bench testing with a 27 Fr prototype was performed to validate the CFD calculations. Results: There was <1.3% difference between the CFD and experimental pressure drop results. The Lagrangian approach revealed a low index of hemolysis (0.012% in drainage lumen and 0.0073% in infusion lumen) at 5 l/min flow rate. Blood stagnancy and recirculation regions were found in the CFD analysis, indicating a potential risk for thrombosis. Conclusions: The pRVAD DLC can handle up to 5 l/min flow with limited potential hemolysis. Further modification of the pRVAD DLC is needed to address blood stagnancy and recirculation.
EN
The innovative extracorporeal heart support device ReligaHeart (RH EXT) has been developed, based on POLVAD ventricular assist device clinical experience, collected in more than 300 patient applications. The innovative surface engineering technologies are applied in ReligaHeart EXT device. The pump is manufactured of new generation, modified surface structure, biocompatible polyurethanes, and equipped with original tilting disc valves, Moll type. The valve ring is made of titanium alloy, TiN+Ti2N+αTi(N) diffusive layer modified, produced with glow discharge at plasma potential, in order to obtain the lowest thrombogenicity. The valve disc is made of polyether ether ketone. The complex in vitro and in vivo biological evaluations were performed, confirming both biomaterials biocompatible properties and device biocompatibility, proved in 30 days animal heart support.
PL
Na podstawie doświadczeń klinicznych protezy serca POLVAD, zastosowanej u ponad 300 pacjentów, opracowano zmodernizowaną pozaustrojową pompę wspomagania serca ReligaHeart EXT (RH EXT). W protezie RH EXT zostały zastosowane innowacyjne technologie inżynierii powierzchni. Pompa wykonana jest z nowej generacji biozgodnych poliuretanów o modyfikowanej strukturze powierzchni i jest wyposażona w oryginalne zastawki dyskowe typu Moll. Pierścień zastawki jest wykonany ze stopu tytanu z dyfuzyjną warstwą TiN+Ti2N+αTi(N) wytwarzaną w procesie obróbki jarzeniowej na potencjale plazmy, dla osiągnięcia niskiej trombogenności. Dysk zastawki jest wykonany z polieteroketonu. Wykonano kompleksową ocenę biozgodności in vitro i in vivo, potwierdzając biozgodne własności biomateriałów i protezy RH EXT, także w czasie 30 dniowego wspomagania serca w modelu zwierzęcym.
EN
The digital image correlation is used to estimate influence of deposited heamocompatible coatings (gold and titanium nitride) on mechanical response of ventricular assist device Religa Heart_Ext made of Bionate II (thermoplastic polycarbonate urethane) under working conditions by comparison of the coated Religa Heart_Ext with uncoated Religa Heart_Ext. The DIC is applied for experimental investigation of the strains and displacements distribution on external surface of the blood chamber of ventricular assist device during loading. The experiment was conducted in a hydraulic system with water at operating temperatures of 25 and 37 °C, as well as under static pressures: 80, 120, 180, 220 and 280 mmHg, and static underpressures: –25, –45, –75 mmHg. The subsequent images were taken after stabilization of pressure on a set level. The applied research method shows that the nano-coating of 30 nm in thickness significantly affects deformation of the blood chamber of Religa Heart_Ext in macro scale. The proposed composition of coatings increases strain on external surface of the ventricular assist device.
EN
The paper presents the results of investigations concerning the noninvasive method of estimating the actual volume of the blood chamber of the POLVAD-EXT type ventricular assist device (VAD) during its operation. The proposed method is based on the principle of Helmholtz’s acoustic resonance. Both the theory, main stages of the development of the measurement method as well as the practical implementation of the proposed method in the physical model of the POLVAD-EXT device are dealt with. The paper contains the results of static measurements by means of the proposed method (conducted at the Department of Optoelectronics, Silesian University of Technology) as well as the dynamic measurements taken at the Foundation of Cardiac Surgery Development (Zabrze, Poland) with the professional model of the human cardiovascular system. The results of these measurements prove that the proposed method allows to estimate the actual blood chamber volume with uncertainties below 10%.
EN
Some medical devices such as mechanical circulatory support systems and defibrillators require synchronization with the appropriate phase of the cardiac cycle of the patient. This paper presents a description of the electrocardiographic (ECG) signal amplifier and QRS detector designed for use with such devices. The detector system was built using a programmable analog array AN231E04 and the ECG amplifier with an analog-digital (A/D) converter based on a programmable circuit (front-end) ADS129x. By using the programmable elements and exploiting the potential of dynamic analog matrix reconfiguration, the presented detector achieved the desired features, such as low latency of QRS detection, automatic gain control and the ability to change the time constant by software. High-resolution of the A/D converter in the ADS1298x and the possibility of programming the gain of the amplifier allow the acquisition of the ECG signal acquired from different types of electrodes: disposable standard, epicardial or endocavitary. The tests of the prototype system proved that it is highly effective for the detection of QRS complexes in ECG waveforms recorded from all kinds of electrodes.
EN
The stroke volume of pulsatile ventricular assist device (VAD) is one of the key clinical indicators to evaluate the adequacy of the process of mechanical heart assistance and ensuring the patient’s safety. In order to evaluate the volume changes in VAD blood chamber, a bioimpedance method was applied, based on volumetric electric conductivity of the blood. Periodic changes in VAD volume during its operation result in a pulsatile impedance waveform; its amplitude in the subperiods of filling and ejection correlates with blood volume in the chamber. The paper presents the method of analysis of the bioimpedance signal recorded in VAD blood chamber with a reference to the classical method of analysing the cardioimpedance signal from the patient’s thorax. The paper also presents the results of determining stroke volume of blood chamber based on an empirical formula that has been developed.
PL
Urządzenia do sztucznego wspomagania pracy serca wymagają synchronizacji z odpowiednią fazą cyklu pracy serca pacjenta. W artykule przedstawiono opis konstrukcji wzmacniacza sygnału EKG i detektora zespołów QRS przeznaczonego do współpracy z takim systemem. Układ detektora zrealizowano wykorzystując programowalną matrycę analogową typu AN231E04, natomiast wzmacniacz sygnału EKG z przetwornikiem A/C oparto na programowalnym układzie ADS 1298. Dzięki użyciu elementów programowalnych i wykorzystaniu możliwości dynamicznej rekonfigurowalności matrycy analogowej, uzyskano pożądane cechy detektora takie jak: małe opóźnienie detekcji zespołów QRS, automatyczną regulację wzmocnienia i możliwość zmiany stałej czasowej na drodze programowej. Badania układu prototypowego potwierdziły wysoką skuteczność detekcji zespołów QRS dla przebiegów EKG zarejestrowanych z elektrod nasercowych.
EN
Cardiac assist devices require synchronization with the proper phase of the heart cycle. This paper presents an ECG amplifier and QRS complexes detector designed for application in a ventricular assist device. The ECG amplifier with the A/D converter was built using ADS 1298 - low-power, 8-channel, 24-bit analog front-end for biopotential measurements. The analog path of the QRS complexes detector was implemented in a Field Programmable Analog Array (FPAA) AN231E04. The dynamic reconfigurability of the FPAA makes it possible to obtain desired features such as: the automatic gain control, low time delay of the QRS detection and automatic time constant correction function. The research works on the prototype circuit proved high detection efficiency for the real ECG signals registered from the epicardial electrodes.
EN
The Polish ventricular assist device, POLVAD_EXT, is made of a polymer designed to be covered with a nanocoating of titanium nitride to improve haemocompatibility. A loss of cohesion can occur between the coating and the substrate. An analysis of stress and strain states in a multi-scale model of the blood chamber was performed in the finite element computer program, VADFEM. The multiscale model is composed of a macro model of the blood chamber and a micro model of the titanium nitride (TiN) deposited on the polymer. The finite element method and the goal function, based on the triaxiality factor, are used to solve the problems formulated. The theories of non-linear elasticity and elasto-plasticity are applied. The goal of the paper is to optimise the construction of the POLVAD_EXT with respect to shape parameters.
PL
W artykule rozpatrzono problem numerycznego modelowania stanu naprężeń i odkształceń komory sztucznego serca POLVAD_EXT, pokrytej powłoką TiN w celu zwiększenia biozgodności. Zaproponowano rozwiązanie tego problemu za pomocą metody elementów skończonych (MES). Wykorzystano teorię nieliniowej sprężystości oraz sprężysto-plastyczności. Własności mechaniczne poliuretanu uzyskano za pomocą testów na rozciąganie, natomiast dane dla powłoki TiN otrzymano za pomocą analizy odwrotnej. Zaproponowany model uwzględnia naprężenia własne, powstające w TiN w procesie nanoszenia powłoki. Wykonano eksperyment numeryczny, pozwalający na analizę wpływu grubości powłoki, wartości naprężeń własnych i falistości powierzchni na wartości naprężeń i odkształceń, decydujące o możliwości powstawania mikropęknięć.
EN
The problem of numerical modeling of the stress and strain states in blood chamber of POLVAD_EXT is considered in the paper. The blood chamber is covered by TiN coating to increase its biocompatibility. The finite element method (FEM) is proposed to solve the formulated problem. The theory of nonlinear elasticity and elasto-plasticity is applied. The mechanical properties of polyurethane were obtained in tension tests and for TiN nanocoating by using inverse method. The suggested model takes into account the residual stresses occurring in TiN during deposition process. The numerical experiment was performed for analysis the influence of thickness of coating, residual stress and wave of surface of coating on stress-strain state which decides about capabilities of micro cracks formation.
EN
Numerical analyses of flow properties for POLYAD-IMPL device eąuipped with Medtronic HallTM valves were performed. Steady flow conditions were assumed in all calculations. Analysis concerned the device in fuli filling position, with inlet and outlet valves open and steady determined flow rate was performed. The analysis of inlet angular valve position in the prosthesis connector in full filling state and outlet valve nearly closed was also performed. Mesh sensitivity analysis on calculation results was examined. Comparative analysis of angular valve position in implantable VAD construction, as well as the analysis of the construction itself, showed that it is necessary to modify the geometry due to hazardous fluid stagnation areas in blood chamber volume and irregular outflow from the chamber into the outlet connector. The construction with angular valve position of 90 centigrade (relative to the base) was characterized by the best flow conditions. However advanced analysis showed significant mesh influence on stagnation areas in the chamber. Better detection of stagnation areas was probably reached due to better mesh "resolution" in the wall vicinity. Despite of multi-million element meshes resulting with significant extension of calculation time, performing analyses with different variants of meshes seems to be important. There is a question constantly where is the"good" mesh limit and how to determine, when it is reached.
PL
W ramach jednego z zadań Programu Polskie Sztuczne Serce, opracowano konstrukcję nowej implantowalnej komory wspomagania serca POLYAD-IMPL. Rezultaty prezentowane w artykule, są jednym z etapów realizowanych prac dla opra­cowania nowej konstrukcji komory i dotyczą analizy jednej z wersji opracowywanej komory PÓLVAD IMPL. Analiza numeryczna przepływu ma na celu zbadanie samej konstrukcji oraz wyłonienie potencjalnie niebezpiecznych obszarów, w których może wy krzepiąc krew. Modelowanie numeryczne wspomaga proces projektowy komory POLYAD-IMPL. Symulacje zostały przeprowadzone w warunkach ustalonych dla komory z zastawkami Medtronic HallTM. Analiza została prze­prowadzona dla komory w fazie pełnego napełnienia przy maksymalnym otwarciu zastawek (wlotowej i wylotowej), dla stałego, ustalonego przepływu. Przeprowadzono również analizę ustawienia kątowego zastawki wlotowej w konektorze napływowym komory w pozycji pełnego napełnienia z domknięta zastawką wylotową. Wykonano analizę wrażliwości siatki na wyniki rozwiązania.
EN
A Ventricular Assist Device (VAD) is used in case of severe heart illnesses when the natural heart supplies the body with an insufficient volume of blood. Any damage or improper fiinctioning of the VAD can result in the patienfs death. This implies the constant need to improve the design of VADs and artificial valves which are crucial parts of the device. The authors used the latest Computer Aided Design and Computational Fluid Dynamics software to analyze the flow in the pneumatic Ventricular Assist Device designed at the Foundation of Cardiac Surgery Development and eąuipped with two different types of valves. In the study, a single-disc mechanical artificial heart valve based on the invention of Prof. J.J. Moll, modified at the Institute of Turbomachinery, TU Lodz, was compared with a three-leaflet polyurethane artificial heart. A comparison was made on the basis of the flow visualization inside the VAD chamber and the size of stagnation regions where the flowing blood may coagulate. An angular position of the disc valve was determined on the basis of the previous studies. A steady state simulation was performed on the assumption that walls of the assist device, adapters and valves were rigid. Dynamie viscosity of blood was defined on the basis on the Non-Newtonian Power Law. Simulations were preformed for systole and diastole conditions. The Ansys CFX vi2 code was used to perform preprocessing, solving and postprocessing stages. Deformations of the three-leaflet polyurethane valve were obtained in SolidWorks 2009 and imported to Ansys ICEM v. 12. On the basis of the preformed analysis, it has been proven that the disc mechanical heart valve generates better flow conditions inside the heart chamber, especially if a risk of coagulation is concerned. Moreover, the flow observed inside the chamber when the disc valve was used is more homogenous and a single swirl occurring in the central part enables good washing of the connection of the diaphragm and chamber regions.
PL
Gdy lewa komora serca nie pracuje prawidłowo, to jest zastępowana protezą - pulsacyjną komorą wspomagania pracy serca (VAD, z ang. ventricular assist device), którą często wykonuje się z poliuretanu (PU) i naniesionej za pomocą metody PLD (osadzenie laserem impulsowym) biokompatybilnej powłoki TiN. Otrzymywane duże wartości ściskających naprężeń własnych, są najwyższe ze wszystkich mierzonych, gdy powłokę TiN nanosi się metodą PLD. Celem niniejszej pracy jest opracowanie programu komputerowego wykorzystującego metodę elementów skończonych (MES) do wieloskalowego modelowania stanu odkształceń i naprężeń dla komory krwistej zbudowanej z PU/TiN, który to program będzie wykorzystywany do określania najbardziej niebezpiecznych miejsc ze względu na możliwe uszkodzenia materiału powierzchni komory, jakie mogą się pojawiać w warunkach pracy komory. Algorytmy wykorzystywane do tworzenia siatki elementów skończonych, implementacja warunków brzegowych i otrzymane rozwiązanie numeryczne zaprezentowano w niniejszej pracy. Opracowany kod MES jest oparty na nowym podejściu do symulowania materiałów wielopowłokowych otrzymywanych metodą PLD. Model w skali mikro zawiera dwa składniki: model naprężeń własnych (naprężeń początkowych) powstałych w procesie nanoszenia powłok i model obciążeń zadawanych w komorze krwistej VAD. Przewidywane w modelu rozkłady naprężeń i odkształceń pomagają określić dokładnie te strefy komory krwistej, które można zdefiniować, jako obszary będące źródłem jej uszkodzeń  
EN
In industrialized countries cardiovascular diseases are the major cause of death. The last clinical therapy option for some patients, suffering from terminal heart diseases, is donor heart transplantation. As the available number of donor organs is decreasing, many patients die while waiting for a transplant. For this reason Ventricular Assist Devices (VADs), which can mechanically support the human heart to achieve a sufficient perfusion of the body, are under development. For an implantable VAD, design constraints have to be deduced from the physiological conditions in the human body. In case of a VAD drive, these constraints are for example dimensions, electric losses, which might result in an overheating of blood, and a long durability. Therefore a hybrid permanent magnet hydrodynamic bearing is designed in this paper, which works passively and contactless. Based on Finite Element simulations of magnetic fields, various permanent magnet topologies are studied in terms of axial forces and stiffness.
EN
Synchronization of operation of an artificial chamber supporting the sick heart of a patient has a crucial meaning for the effectiveness of support. To make the synchronized operation possible, the information on patient's heart activity should be fed to a controller of the supporting chamber. To this end, the QRS complex detector operating on ECG signal is necessary. The signal must be acquired from a patient's heart. Appropriate signal quality at long-term support may be assured only in a case the signal is acquired with epicardial electrodes. In the paper, the concept of hardware construction of a QRS complex detector has been presented, based on a field programmable analog array FPAA. The results of verification of the developed detector include the correct operation while using the epicardial signals recorded from patients which undergone the cardiosurgical operations.
15
Content available remote Mechanical circulatory support systems at Tokyo Medical and Dental University
EN
This paper describes mechanical circulatory support devices (MCSD) which are under development at Tokyo Medical and Dental University in collaboration with Tokyo Institute of Technology. They include para-corporeal magnetic levitated (Mag-lev) centrifugal blood pump, implantable Mag-lev centrifugal blood pump, extra-corporeal pediatric centrifugal blood pump, and implantable pulsatile ventricular assist device (VAD) and totally replacement artificial heart system.
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).
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