Mechanical Support Systems Research Articles

磁力支持天秤を用いた非定常流体力の測定(G05-2 物体に働く流体力,G05 流体工学部門一般講演)

The characteristics of the unsteady forces acting on the body are quite different from the quasi-steady ones. The peaks of the lift force are observed for moving airfoil at a high angle of attack. A time dependent flow forces called the dynamic lift have to be taken into account because the moving motion is obviously unsteady. In this study, the wind tunnel tests were conducted using a Magnetic Suspension and Balance System (MSBS) to measure the aerodynamic forces. The support interference problem does not exist for the MSBS because the support force of the model is generated by the magnetic field and any mechanical support system is not needed. Furthermore, the measurements of the three-dimensional velocity to understand the relation between the dynamic lift and corresponding unsteady flow field are carried out. Lift and Drag forces of the test model were measured by using the MSBS and it is confirmed that the pitching motion is one of the best way to increase lift.

Left ventricle mechanical support systems: an alternative to heart transplantation

In allogeneic transplantation the donor–recipient sex combination plays a role in outcome. In large retrospective registry studies of several thousands of patients with aplastic anemia, chronic myelocytic leukemia (CML), acute myelocytic leukemia (AML), and multiple myeloma, chronic graft-versus-host disease (cGVHD) was more frequent and transplant-related mortality (TRM) higher in males with a female donor (F → M) than in other donor–recipient sex combinations. Graft rejection was more frequent in females with a male donor (M → F) in aplastic anemia, and a graft-versus-tumor effect (GVT) was documented as a reduced relapse rate in F → M in CML, AML and multiple myeloma. The overall survival was adversely affected in F → M in aplastic anemia, AML and CML and in M → F in aplastic anemia. These results support the view that donor T cells specific for male minor histocompatiblity antigens encoded by Y-chromosome genes contribute to GVHD, graft rejection, GVT and survival in sex-mismatched transplants.

Design and R&D progress of blanket attachments

The ITER blanket is built of small regular modules attached to the vacuum vessel by an insulated mechanical support system, an electrical connector for grounding and a hydraulic connector for the coolant manifolds. An attachment has been developed which satisfies the demanding load conditions and which includes the handling features to enable the removal of the module for repair in the hot cells. Latest improvements are presented with the comprehensive R&D activities used to validate the design.

Pathological patient in protocol definition for bench testing of mechanical cardiac support system.

Clinical techniques for the restoration of a failing heart are mainly based on the use of mechanical assist devices. In recent years, with the growing need for mechanical circulatory support, these devices have been shown to be a useful therapeutic tool, thanks to their intrinsic capability to unload the failing ventricle, allowing the heart to recover. Mechanical circulatory support systems (MCSS) require an accurate biomechanical characterization of the complex interaction that occurs between the patient and the mechanical support. A protocol for MCSS testing is proposed which takes into account several working conditions, in a modified test mock loop apparatus able to mimic various pathological conditions. Both physiological and pathological conditions can be replicated to show the actual efficacy of a MCSS device in correctly supporting a wide spectrum of ventricular conditions. The test bench is able to simulate the recovery of the pathological condition quite accurately, showing, at the same time, that this set up can be a reliable choice to characterize cardiac support devices. Thus the results of this experimentation can be useful to clinicians in forecasting the response of the heart affected by a cardiac disease and to set appropriate parameters for suitable assistance.

Toward the ideal mechanical engineering design support system

This paper details the progress toward the development of the ideal mechanical engineering design support system. It attempts to look at the gap between the needs of a mechanical engineer and what is currently available on CAD systems. Since the term CAD emphasizes that the computer is an aid to the human designer, this paper is designer-centric. It is based heavily on the activities performed by designers and the types of information developed by them. Seventeen goals for the ideal mechanical design support system are listed. These are directed at the types of information developed during the design process and the activities used to develop them. For each of the seventeen, background information, the current state-of-the-art, and opportunities for future development are itemized.

Mechanical Design Support System Based on Thinking Process Development Diagram

Mechanical Design Support System Based on Thinking Process Development Diagram

1223 階層分析法を用いた最適設計支援システムの構築

1223 階層分析法を用いた最適設計支援システムの構築

1212 階層分析法を用いた最適設計支援システムの構築 : グラフモデルを用いた構成の最適化

1212 階層分析法を用いた最適設計支援システムの構築 : グラフモデルを用いた構成の最適化

The SLS storage ring support and alignment systems

Storage rings of third generation synchrotron radiation facilities pose severe challenges for lowering the beam emittances and increasing the lifetimes, requiring thus increasing positioning and alignment precisions that must be preserved over long time spans. This work describes the SLS storage ring mechanical support, alignment and disturbances compensation systems that allow to meet these requirements. In particular, their design, the tests done on the respective prototypes and the applicability of the developed arrangement to beam-based alignment are addressed.

ARTIFICIAL LIVER SUPPORT DEVICES FOR FULMINANT LIVER FAILURE

Artificial liver-support devices attempt to bridge patients with fulminant hepatic failure until either a suitable liver allograft is obtained for transplantation or the patient's own liver regenerates sufficiently to resume normal function. It is thought that toxins contribute to the clinical picture of fulminant hepatic failure. The earliest reports of successful toxin removal were blood- and plasma-exchange transfusions. Given these successful case reports, mechanical liver-support devices were designed to filter toxins. These mechanical devices used hemodialysis, charcoal hemoperfusion, hemoperfusion through cation-exchange resins, hemodiabsorption, and combinations of all of these techniques as in the MARS liver-support device. Despite promising case reports and small series, no controlled studies of mechanical devices have ever showed a long-term survival benefit. Thus, the removal of presumed toxins seems to be insufficient to support patients with fulminant hepatic failure, and the biologic function of the liver must also be replaced. Attempts at replacing the biologic function have included extracorporeal liver perfusion, cross-circulation, and hepatocyte transplantation. Current technologies have combined mechanical and biologic support systems in hybrid liver-support devices. The mechanical component of these hybrid devices serves both to remove toxins and to create a barrier between the patient's serum and the biologic component of the liver-support device. The biologic component of these hybrid liver support devices may consist of liver slices, granulated liver, or hepatocytes from low-grade tumor cells or porcine hepatocytes. These biologic components are housed within bioreactors. Currently the most clinically studied bioreactors are those that use capillary hollow-fiber systems. Both the bioartificial liver by Demetrious and the extracorporeal liver-assist device by Sussman and Kelly are in clinical trials. Although the trials seemed to have yielded good survival data when the devices are used as a bridge to transplantation, the type and degree of liver support provided by these devices remains uncertain. Thus, despite decades of great progress in the field of artificial liver support, no one technique alone yet provides sufficient liver support. A hybrid system seems to be the best option at present. Still to be determined is the best tissue to use, how much liver tissue should be used, and the optimal design of the bioreactor.

HYDRODYNAMIC PROPERTIES OF A NEW PERCUTANEOUS INTRA AORTIC AXIAL FLOW PUMP

Treatment of cardiac failure by means of mechanical support systems is an option when medical treatment fails. However, some support systems today require major surgery and therefore, we are developing a minimally invasive intraaortic axial flow pump with a foldable propeller. In animals the pump has shown a positive hemodynamic influence, and the present study evaluates the hydraulic properties of the pump in a bench test. The axial flow pump is a catheter system with a distal foldable propeller (0-15000 rpm). To protect the aortic wall, filaments forming a cage surround the propeller. The motion of the propeller is transmitted via an internal wire from a DC motor placed at the proximal end of the catheter. In the present study, tests were done in a mock loop with different tube sizes mimicking the variability in diameter of the human aorta. The test matrix included 1) the pressure generation at zero flow in the different tubes with increasing rpm, 2) the pressure generation in different tubes at constant rpm and 3) the pressure flow relationship at different rpm in the various tubes. At zero flow, there was a positive relationship between rpm and the generated pressure and a negative relationship between the diameter of the tube and the generated pressure. Within the physiological range of cardiac output there was a small drop in pressure with the increasing flow in the tubes with a small diameter. With an increasing diameter of the tube a smaller pressure drop was seen with the increasing flow. The present cardiac support system has hydraulic properties, which may be of clinical relevance for patients with left ventricular heart failure.

Transthoracic intraaortic balloon usage

lntraaortic balloon usage is increasing in left ventricular failure situations. Especially in cardiac surgery, intraaortic balloon becomes the 1irst choice of mechanical support systems when the patients could not be weaned cardiopulmonary bypass. The most frequent way of insertion is transfemoral route. However sometimes it is impossible to insert the balloon transfemorally especially in peripheral vascular disease situations. So altarnate ways of inserting the intraaortic balloon is needed. in Siyami Ersek Thoracic and Cardiovascular Surgery Centre we inserted intraaortic balloon transthoracically in 5 cases. Mean time of duration was 3 days and when compared with transfemoral route, no difference was dedected in the efficiency of the counterpulsation. However when the complications were compared, more serious complication could take place with transthoracic route. Our current recommendation is to use transthoracic route only in suitable cases when transfemoral route could not be used.

Three-dimensional tree constructs of “constant” thermal resistance

This article extends to three-dimensional heat flow the constructal method of minimizing geometrically the thermal resistance between a heat-generating volume and one point. Optimized is the geometry of each volume element, and the shape and distribution of high-conductivity inserts. The new feature is the maximization of the amount of heat-generating material that operates at temperatures close to the hot-spot level (Tmax). Volume elements and subsequent constructs acquire optimal shapes where all the external surfaces are isothermal at Tmax. The same, constant thermal resistance separates each surface point (Tmax) and the common heat-sink point (Tmin). The optimized architecture is pine-cone-like, with high-conductivity nerves and low-conductivity filling (and heat-generating) material. The similarities between the constant-resistance structures and the three-dimensional tree networks found in nature are discussed. The analogy between evolutionary flow systems and evolutionary mechanical support systems is reasoned based on the same (constructal) principle of pursuing objective (purpose) subject to global and local constraints.

Temporary pulsatile ventricular assist devices and biventricular assist devices

Background. During the past years several systems for mechanical circulatory support have become available. In this study we describe our experience with short-term and mid-term application of the ABIOMED and Thoratec device. Methods. Since 1990 the ABIOMED BVS and since 1992 the Thoratec VAD have been applied to 75 and 103 patients, respectively, with postcardiotomy heart failure, as a bridge-to-transplant procedure, and with different other indications. Results. In the ABIOMED collective 25 of 50 patients (50%) with postcardiotomy heart failure and 1 of 4 patients with miscellaneous other indications could be discharged from hospital, 7 of 14 bridge-to-transplant patients (50%) underwent transplantation with a post-transplant survival of 86%. In the Thoratec collective 6 of 10 patients (60%) with postcardiotomy heart failure and 4 of 8 patients (50%) with miscellaneous indications could be discharged from hospital, 48 bridge-to-transplant patients (74%) underwent transplantation with a post-transplant survival of 90%. Conclusions. The results show the versatility of the Thoratec VAD for short-term and mid-term application in patients with postcardiotomy heart failure and as a bridge-to-transplant procedure. The use of the ABIOMED device is not indicated for bridging patients to transplantation. Although in case of postcardiotomy heart failure, Thoratec is also superior to ABIOMED, the high costs of the Thoratec VAD limits its wide acceptance in this patient cohort.

Weaning from mechanical cardiac support in patients with idiopathic dilated cardiomyopathy.

Implantation of mechanical cardiac support systems (MCSS) in patients with idiopathic dilated cardiomyopathy (IDC) may improve cardiac function and allow explantation of the device. We report of long-term effects of ventricular unloading on cardiac function, humoral anti-beta1-adrenoceptor autoantibodies (A-beta1-AABs), and myocardial fibrosis. Seventeen patients in New York Heart Association functional class IV with nonischemic IDC received MCSS. All had a cardiac index of < 1.6 L x min(-1) x m(-2) of body surface area, a left ventricular ejection fraction (LVEF) of <16%, and a left ventricular internal diameter in diastole (LVIDd) of >68 mm and tested positive for A-beta1-AABs. Echocardiographic evaluation, serum tests for A-beta1-AABs, and histological assessment of myocardial fibrosis were performed before and after MCSS implantation. The mean support duration was 230+/-201 days. Six patients died, four were transplanted, and two are still on MCSS. Five patients with significant cardiac recovery (mean LVIDd, 54+/-2.3 mm; LVEF, 47+/-3.7%) were weaned after 160 to 794 days and are now device free for 51 to 592 days. A-beta1-AABs disappeared gradually during MCSS without increase after weaning; cardiac function and volume density of fibrosis remained normal. Nine patients' cardiac function hardly improved during ventricular unloading. Cardiac function can be normalized in selected patients with end-stage IDC by MCSS. The degree of preoperative myocardial fibrosis may be an indicator for outcome; A-beta1-AABs can be used to monitor myocyte recovery. Weaning from MCSS offers an alternative to cardiac transplantation in certain patients.

Will permanent LVADs be better than heart transplantation?

Current interest in permanent mechanical support systems has been renewed as a result of the present shortage of human heart donors, and in view of the satisfactory results obtained with their use as a bridge-to-transplant. As the number of donors is unlikely to increase dramatically in the near future, there is an urgent need to develop mechanical alternatives to transplantation. Preliminary data on the use of the implantable electric LVAD as a bridge-to-transplant indicate that the adverse clinical and mechanical events in outpatients are few and do not preclude use of the device on a permanent basis. Except for infections, transplant issues relating to need for endomyocardial biopsies, rejection, malignancies, and graft arteriosclerosis do not apply to LVAD recipients who face important issues relating to device durability, cost, and potential need for concomitant right heart support. This lack of data on long-term durability contrasts with a yearly mortality rate of about 5% after the first year of transplant. With the initiation of clinical trials on the permanent use of the electric LVAD, several design modifications and upgrading of the currently available devices are expected. Completely sealed systems with steadily improving durability will hopefully appear. Inductive coupling techniques under investigation and development appear to be able to transmit energy without damage across the skin. It is anticipated that with more reliable electronic microprocessors, the future generation of implantable LVADs will be smaller, more reliable and longer lasting.

Current status of mechanical ventilation decision support systems: a review.

Objectives of computerized decision support systems for mechanical ventilation are discussed. Questions considered are: Why is computerized decision support for mechanical ventilation important? What parameter(s) should be optimized? What are the differences between a single attribute and a multiattribute value function used for optimization? How is it possible to achieve optimization in clinical practice with existing ventilators? How does one solve the problem of acquiring measurement of data needed for closed loop control? The possibilities and limitations of three existing decision support systems are discussed. 1) Computerized protocols from LDS Hospital in Salt Lake City, Utah, USA. 2) Optimization Program (OPTPROG) developed jointly at the Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland and Medical Intensive Care Unit, Department of Medicine at Karolinska Institute, South Hospital, Stockholm, Department of Medical Informatics Linkoping University, Sweden. 3) Ventilator Therapy Planner (VENT-PLAN) from the Section on Medical Informatics at Stanford University, Palo Alto, California, USA. Strategies leading to an optimal computerized decision support system are proposed. These strategies include development of better measurement methods for blood gases and cardiac output, improvement of man-machine and machine-machine interaction and the selection of optimization criteria. Finally, research directed towards building quantitative, dynamic patient models based on computerized databases of mechanically ventilated patients are discussed.

Thermal isolation of large loads at low temperature using Kevlar rope

A mechanical support system is described for a space-borne 3He refrigerator that relies on Kevlar 29 braided cords to achieve thermal isolation at temperatures ranging from 0.3 to 40 K. Measurements of the Young's modulus, tensile strength, creep and thermal conductivity of Kevlar cords at room and liquid nitrogen temperatures are discussed and used to predict the performance of the system. Results of vibration tests of the mechanical support are compared with these predictions. The system safely supports a 350 g mass against 30 G sinusoidal accelerations at frequencies of 20 Hz to 2 kHz. The calculated heat load between 2 and 0.3 K is 0.7 μW.

Results of acute heart retransplantation in Eurotransplant.

In 1988 a special programme for acute retransplantation was introduced in Eurotransplant, giving patients awaiting acute retransplantation priority in the selection procedure. Due to scarcity of donor hearts the question arose whether graft survival after acute retransplantation justified the use of these hearts for this category of patient. A retrospective analysis on the results of transplantations performed in patients who were awaiting acute retransplantation within Eurotransplant was done. In 18 out of 46 cases the patient was treated prior to retransplantation with some kind of mechanical support device. Of the 46 grafts, 28 failed. The actuarial 1-year graft survival in this study group was 36%. In comparison, graft survival for primary cardiac transplantation is approximately 81%. Graft survival after acute heart retransplantation is very poor, especially when the patient has been pretreated with a severe mechanical support system.

Results of acute heart retransplantation in Eurotransplant

In 1988 a special programme for acute retransplantation was introduced in Eurotransplant, giving patients awaiting acute retransplantation priority in the selection procedure. Due to scarcity of donor hearts the question arose whether graft survival after acute retransplantation justified the use of these hearts for this category of patient. A retrospective analysis on the results of transplantations performed in patients who were awaiting acute retransplantation within Eurotransplant was done. In 18 out of 46 cases the patient was treated prior to retransplantation with some kind of mechanical support device. Of the 46 grafts, 28 failed. The actuarial 1-year graft survival in this study group was 36%. In comparison, graft survival for primary cardiac transplantation is approximately 81%. Graft survival after acute heart retransplantation is very poor, especially when the patient has been pretreated with a severe mechanical support system.