Development of a multifunctional detoxifying unit for liver failure patients.

Background/aims: Extracorporeal blood detoxification strategies aimed at supporting impaired liver function have been explored because of the imbalance between donor organs and waiting patients. A limited number of artificial devices are now available clinically, and these are characterized by the use of multistage adsorption procedures in conjunction with hemodialysis, but these features simultaneously increase system complexity and treatment costs.

Methods: The authors developed a simpler strategy for liver dialysis based on the use of a multifunctional filter, which enables plasma separation and perfusion in a single unit.

Evaluation of a new method for pulse push/pull hemodialysis: comparison with conventional hemodialysis.

The repetition of forward and backward filtration during hemodialysis (HD) increases convective mass transfer, and thus, the authors devised a method of achieving cyclic repletion of ultrafiltration and backfiltration. Hemodialytic efficiencies of the developed unit are described. The devised method, named pulse push/pull hemodialysis (PPPHD), is based on the utilization of dual pulsation in a dialysate stream.

A dual-chambered hemodialyzer for convection-enhanced hemodialysis.

Convective clearance during hemodialysis (HD) improves dialysis outcomes in kidney failure patients, and, thus, trials have been undertaken to increase convective mass transfer, which is directly related to internal filtration rates. The authors designed a new hemodialyzer to increase the internal filtration rates, and here describe the hemodialytic efficacy of the devised unit. The developed dual-chambered hemodialyzer (DCH) contains two separate chambers for dialysate flow within a single housing.

Effects of arterial port design on blood flow distribution in hemodialyzers.

Background/aims: Blood flow profiles in fiber bundles depend on the design of the arterial port and affects the biocompatibility of the hemodialyzer. We analyzed the effects of arterial port design on blood flow distribution in fiber bundles using nonintrusive imaging techniques.

Methods: The velocity fields in arterial ports and the hemodynamics in fiber bundles were analyzed for hemodialyzers with different configurations using particle image velocimetry and perfusion computed tomography.

Development of a cold dialysate regeneration system for home hemodialysis.

Background/aims: Because longer and/or more frequent dialysis has potential clinical benefits, home hemodialysis (HHD) systems should provide flexible renal replacement therapies. We propose a new cold dialysate regeneration system that requires 10 l per treatment for HHD.

Methods: We designed a dialysate regeneration system using cold dialysate and 2 activated carbon columns alternatively switched between adsorption and desorption.

Quantitative analysis of pulsatile flow contribution to ultrafiltration.

We evaluated the quantitative contribution of pulsatile flow to ultrafiltration (UF) in terms of fluid power, membrane stretch, and reduction of membrane layering. An in vitro comparison of the UF rate using pulsatile and roller pumps was performed with distilled water and bovine whole blood. The mean transmembrane pressure (TMPm) and UF rate were higher with the pulsatile pump for the same mean flow rate: 6.

Pulse push/pull hemodialysis in a canine renal failure model.

A new dialysis modality was devised to increase convective mass transfer. Blood and dialysate are circulated by a pulsatile pump, but with pulsatile flow patterns that are 180 degrees out of phase, which causes blood-to-dialysate pressure gradients to oscillate between positive and negative. In the present study, hemodialytic performance of the devised modality was investigated using a canine renal failure model.

Application of an elastic biodegradable poly(L-lactide-co-epsilon-caprolactone) scaffold for cartilage tissue regeneration.

In cartilage tissue regeneration, it is important that an implant inserted into a defect site can maintain its mechanical integrity and endure stress loads from the body, in addition to being biocompatible and able to induce tissue growth. These factors are crucial in the design of scaffolds for cartilage tissue engineering. We developed an elastic biodegradable scaffold from poly(L-lactideco-epsilon-caprolactone) (PLCL) for application in cartilage treatment.

Comparison of a pulsatile blood pump and a peristaltic roller pump during hemoperfusion treatment in a canine model of paraquat poisoning.

This study examined the treatment efficacy and the damage to the blood during hemoperfusion for treating paraquat poisoning using two blood pump mechanisms. Paraquat-poisoned animal models were prepared. A conventional hemodialysis machine, AK90, with a peristaltic roller pump and a cardiopulmonary support system, T-PLS, with a pulsatile blood pump were used during the animal experiments.

Pulse push/pull hemodialysis: in vitro study on new dialysis modality with higher convective efficiency.

Midsize molecule retention is related with renal-failure-associated mortality. Here, the authors describe a new dialysis modality, pulse push/pull hemodialysis (PPPHD), which increases convective clearance. Blood and dialysate are circulated by a pulsatile pump, but with pulsatile flow patterns that are 180 degrees out of phase.

Hemodialysis using a valveless pulsatile blood pump.

Research on pulsatile blood pumps for extracorporeal life support has been widely performed because of the proven advantageous effects of blood pulsation. However, studies on the use of pulsatile blood pumps for hemodialysis are limited, although available evidence demonstrates that pulsatile blood flow has a positive influence on dialysis outcome. Therefore, the authors designed a new pulsatile pump, which is characterized by minimal-occlusion of blood-containing tubing, no requirement for valves, and no blood flow regurgitation.

Comparison of hemolytic properties of different shapes of occlusion of blood sac in occlusive-type pulsatile blood pump.

The occlusive-type pulsatile extracorporeal blood pump (T-PLS, Seoul National University, Seoul, Korea) received the Communauté Européenne mark of the European Directives (2003) and Korea Food and Drug Administration approval (2004) for short-term application as an extracorporeal life support system. The pump system was recently upgraded in the ameliorated actuator head for reducing hemolysis, rather than in the existing actuator head. In this study, the hemolytic performance of the new pump system (assessed as the degree of occlusiveness of the blood sac) was compared with the existing one.

Cartilaginous tissue formation using a mechano-active scaffold and dynamic compressive stimulation.

It is known that complex loading is involved in the development and maintenance of articular cartilage in the body. It means the compressive mechanical stimulation is a very important factor for formation of articular cartilage using a tissue-engineering technique. The objective of this study is to engineer cartilaginous constructs with mechano-active scaffolds and to evaluate the effect of dynamic compression for regeneration of cartilage.

Computational dose predictions for combined treatment of hemofiltration with weekly hemodialysis.

Hemodialysis (HD) has sufficient efficacy as a conventional diffusive treatment for removing small molecules, whereas hemofiltration (HF), which is a convective treatment, has an improved the clearance of intermediate-sized molecules. This paper reports a combined treatment (CT) which combines the diffusive and convective efficacies of HF several times weekly with HD weekly. CT modalities with various schedules and prescriptions are described mathematically using a variable-volume two-compartment kinetics model, and the kinetic parameters were obtained from previous clinical reports and a hemodialysis-related database.

Durability improvement of polymer chamber of pulsatile extracorporeal life support system in terms of mechanical change.

Twin Pulse Life Support, T-PLS has received the CE mark (2003) and Korea Food and Drug Administration (KFDA) approval (2004) for short-term application as an Extracorporeal Life Support system (ECLS). T-PLS's original intention was to apply for not only short-term but also long-term application such as Extracorporeal ventricular assist device (VAD). Hence, a long-term durability test was conducted.

Convection-enhanced high-flux hemodialysis.

Internal filtration contributes to convective clearance in high-flux hemodialysis but its contribution is limited by low pressure gradients. Therefore, a modification using a conventional dialyzer was conceived to enhance internal filtration and backfiltration (BF) rates. The modified dialyzer includes two longitudinal independent regions for blood flow, which were created by redesigning dialyzer caps.

Pseudo-organ boundary conditions applied to a computational fluid dynamics model of the human aorta.

In three-dimensional numerical studies of the aorta, it is difficult to apply proper boundary conditions at the end of each major aortic branch because of interactions between blood and organs. Organs and body parts were assumed to be likened to cylindrically shaped porous media, so-called pseudo-organs, and treated in the computational domain as forms of hemodynamic resistance. Permeability functions were determined from two-dimensional axisymmetric computations of each aortic branch and these functions were then used in an unsteady three-dimensional simulation of the complete aorta.

Probe classification of on-off type DNA microarray images with a nonlinear matching measure.

We propose a nonlinear matching measure, called counting measure, as a signal detection measure that is defined as the number of on pixels in the spot area. It is applied to classify probes for an on-off type DNA microarray, where each probe spot is classified as hybridized or not. The counting measure also incorporates the maximum response search method, where the expected signal is obtained by taking the maximum among the measured responses of the various positions and sizes of the spot template.

Differentiation, engraftment and functional effects of pre-treated mesenchymal stem cells in a rat myocardial infarct model.

Background: Mesenchymal stem cells (MSCs) offer a novel therapeutic option in the treatment of acute myocardial infarction. MSCs are able to differentiate into myogenic cells after 5-azacytitdine treatment. However, 5-azacytidine might have genotoxic effects.

Computational analysis of the three-dimensional hemodynamics of the blood sac in the twin-pulse life-support system.

Blood flow in the twin-pulse life-support system (T-PLS) pulsatile blood pump was simulated using a three-dimensional rigid body-fluid-solid interaction model. This model can delineate the blood flow in the T-PLS resulting from operation of a moving actuator. The numerical method used in this study was a commercial finite element package called ADINA.

Computerized scheme for assessing ultrasonographic features of breast masses.

Rationale And Objective: To evaluate the ultrasonographic features of breast masses using a computerized scheme and to correlate the feature values with radiologists' grading.

Materials And Methods: One hundred and seventy-five breast ultrasound images (one to five images per subject) from 61 women (age 17-89 years, mean 43 years) were studied. Thirty-eight of the 157 images were from 11 women with malignant lesions, and the remaining 137 were from 50 patients with benign lesions.

Nonlinear matching measure for the analysis of on-off type DNA microarray images.

We propose a new nonlinear matching measure for automatic analysis of the on-off type DNA microarray images in which the hybridized spots are detected by a template-matching method. The proposed measure is obtained by binary thresholding over the entire template region and taking the number of white pixels inside the spotted area. This measure is compared with the normalized covariance method in terms of classifying the ability to successfully locate markers.

Assessment and improvement of the system efficiency for the moving-actuator type biventricular assist device.

This is a test report on the efficiency of a moving-actuator type biventricular assist device (AnyHeart, Seoul National University). From the viewpoint of the various system mechanisms, the device can be subdivided into three separate parts: the motor and its associated controller, the actuator and motor assembly, and the blood sac and its associated components (including valves). The motor was operated under various conditions, including different torque, angular speed, and voltage pulses.

In vivo evaluation of the pulsatile ECLS system.

Extracorporeal life support (ECLS) systems have been increasingly applied to groups of patients with cardiorespiratory failure, including pediatric and adult patients with respiratory failure. Current pulsatile ECLS systems use a single pulsatile blood pump that generates a high inlet pressure in the membrane oxygenator. To minimize this high inlet pressure, we have developed a new and improved ECLS system, twin pulse life support (T-PLS).