Mechanical fragility of red blood cells (RBCs) is a critical variable for the hemolysis testing of many important clinical devices, such as pumps, valves, and cannulae, and gas exchange devices. Unfortunately, no standardized test for RBC mechanical fragility is currently well accepted. Although many test devices have been proposed for the study of mechanical fragility of RBCs, no one has ever shown that their results have any relevance to a blood pump. Therefore, the fundamental objective of this study was to determine if one or more test devices could be validated as calibrators to document the fragility of the test blood used for any particular test blood. We compared five mechanical fragility test systems to each other and to a Biopump, with respect to hemolysis. All five devices seem to measure the same parameter; the hemoresistometer most closely matched the pump test results, but the stainless steel bead test may be the most practical for routine calibration purposes.
The potential for mechanical erythrocyte damage, or hemolysis, in heart valves and blood pumps has been estimated using computational fluid dynamics (CFD) analysis, combined with mathematical models of red cell damage mechanisms. To date, these prediction approaches have not been compared with each other in common benchmark cases, nor have they been evaluated in radically different flow geometries. In this study, four test devices, including a hemoresistometer, a spinning disk, a capillary tube, and a concentric cylinder viscometer were hemolysis tested and computationally simulated. A number of existing models were used to predict blood damage and these models were compared with each other and with actual measurement of hemolysis. The study indicates that the effectiveness of blood damage prediction from the existing models is similar and can potentially be improved with the consideration of a proposed repeated flow passage effect. It also indicates that the improved models can be used to more effectively predict blood damage in widely different situations.
The PediPump is a passive magnetic bearing, mixed flow, rotary ventricular assist device designed to provide support for the entire range of patient sizes encountered in pediatrics. Blood enters axially at the inlet and is accelerated and turned in the impeller to exit the pump at an intermediate angle. The size of the PediPump facilitates standard cannulation strategies with substantially downsized components. The program pursues three specific objectives: 1) System engineering: Progress within the last year has focused on the assembly and testing of PediPump prototypes. Initial in vitro hydraulic performance and hemolysis testing were judged satisfactory. 2) Anatomic fitting studies: As part of the PediPump program, three-dimensional modeling techniques based on routine, clinically obtained computerized tomography (CT) scans have been developed. During 2006, the same techniques developed for clinical scans were applied to CT scans obtained from sheep to guide the presurgical planning. 3) Animal studies: Animal implantation of PediPump prototypes commenced in July 2006. A total of four 6 hour acute studies were performed throughout the remainder of the year. In vivo performance was satisfactory and compared well with the in vitro results. Hemolysis levels were low.
The PediPump is a small ventricular assist device (VAD) with a hydraulic output range designed to support children from newborns to adolescents. The present report describes our initial evaluation of the PediPump as a left VAD in an acute sheep model. The PediPump was implanted in two sheep (50.8 and 62.7 kg). Pump speed was adjusted to achieve a flow of 2 L/min with the naturally occurring preload and afterload conditions to evaluate pump performance under a steady hemodynamic state for 4 hours. Upon completion, pump performance was evaluated under various blood pressure and heart rate conditions. During steady-state evaluations, the ascending aortic flow and pump speed varied slightly depending on systemic arterial pressure variations. During the hemodynamic manipulation studies, flows ranged between 0.5 and 3.2 L/min with pump speeds of 5,200-16,200 rpm and motor current of 0.06-0.75 A. The PediPump demonstrated good initial hemodynamic performance for use as an implantable left VAD. However, some depositions were detected at the time of explanation, mainly at the rear of the pump. We are continuing with further acute studies to evaluate pump performance in anticipation of beginning chronic studies to evaluate long-term biocompatibility.
This paper presents the geotechnical investigations, analyses of data, design requirements and proposed construction methods for a steep embankment in eastern Pennsylvania. As part of the improvements to the I-81 Exit 178-Avoca/Airport Interchange project, a new 1.4 km road is proposed between the interchange and a nearby industrial park. The new road will be constructed mostly on embankment fill. At one point, the road is required to pass between two existing airport runway light towers. Due to an existing valley in this vicinity and the geometric constraints of the light towers, the proposed embankment fill in this area reaches a maximum of approximately 16 m in height with slopes as steep as 0.6 horizontal to 1 vertical (0.6H:1V). The project site is located within the Northern Anthracite coal fields. Historical mine data indicate that the anthracite coal is characterized by extensive abandoned surface and underground mine workings. The critical nature of existing towers, along with difficult subsurface conditions at the project site, results in several geotechnical challenges in design of the steep embankment for the new road. This paper focuses on the proposed steep slopes at the runway tower site and presents investigations and analyses performed by Gannett Fleming including mine void identification, potential settlement estimates due to mine subsidence and stability issues of the steep embankment. Additional considerations presented include grout stabilization of mine voids and settlement monitoring.
In response to the needs of spacecraft cable three-dimensional crossover layout, research on cable installation methods based on CSB bus has been carried out. Aiming at the status of using CSB bus cable in the satellite communication cabin of DFH-4 platform for the first time, on the basis of detailed analysis of the performance of CSB bus, the laying and binding methods are analyzed and tested, and the cable installation method on the carbon fiber bracket is proposed. Technical solutions. It has been proved through practice that this method meets the actual needs of satellites, solves the problems of laying and tying the bus cables of the communication cabin, and effectively meets the needs of the spacecraft cable three-dimensional crossover layout, and greatly improves the spacecraft assembly efficiency.
Based on the current situation of passenger flow in Guangzhou Metro, this paper summarizes the shortcomings and possible risks of passenger transport organization. And after analyzing the current main methods of monitoring crowd density, and the crowd density detection algorithm in video surveillance and subsequent video processing, this paper proposes a crowd density classification method based on frame difference method with its application direction, which optimizes the existing subway station crowd control measures as well as helps subway station operators accurately identify the stage of crowd density in real time and take crowd control measures in time.
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