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PubMed1982

Surface processes in artificial organs. An overview.

The area of contact between an artificial organ and the biological environment results from the inner and outer surface of the organ. The lifetime of the organ determines the properties of the material's surfaces in use. Reactions occur in both directions--from the surface to the body and vice versa, from the body to the surface. Centers of nucleation and points for destruction propagation due to attacks of body fluids are irregularities of the surface structure and gradients in the chemical composition of both material and fluid. Some of the mechanisms that occur are initiated or at least promoted by mechanical factors. Some of the body-surface interactions that take place are: adsorption, degradation, corrosion, calcification, fatigue, embrittlement, and wear; these limit the lifetime of artificial organs. The strength of the interaction depends on the substituted function, the design, and the locus of implantation.

Adsorption↗
PubMed2003

The multidisciplinary approach to develop artificial organs.

This paper presents the author's perspective of how artificial organ development has evolved in the past 35 years into a multidisciplinary effort. Examples are taken from the fields of hemodialysis, oxygenators, and affinity immunoadsorption devices. Development of the multidisciplinary approach to develop dialysis and oxygenation membranes has been significantly advanced by private and governmental collaboration and conferences that gathered together chemists, physicians, engineers, and fluid dynamics experts. Lengthy delays occurred in artificial organ development when such interdisciplinary collaborations did not take place.

Artificial Organs↗
PubMedDate not supplied

A new apparatus for chronic observation of the microcirculation in situ to evaluate artificial organ performance.

Chronic study of the peripheral circulation and metabolism is very important in evaluation of artificial organ performance. However, there has been no way to observe the microcirculation in situ, chronically and continuously, without restriction. In this study, the authors developed a new apparatus that could be implanted and connected to an artificial organ that would allow continuous observation of the microcirculation while the subject is awake. The apparatus uses a charge coupled device (CCD) under a new principle: thin living tissue, such as mesentery, is put directly on a highly integrated CCD and transilluminated with a light emitting diode (LED). The vascular nets in the tissue are projected onto the CCD like a contact photograph, which is sent to a television screen and can be analyzed for motion and function. A 0.5 inch CCD with 25K pixels was used in this study. The cover glass of the CCD was removed so the tissue would be able to directly contact the CCD surface. The CCD, as well as LED, were molded with hard polyurethane as electrical insulation. The apparatus is 35 mm in diameter and 10 mm high with a micro stand for lighting with the LED, which is easy to implant in a goat or calf. The resolution of this apparatus was tested by putting a micro scale on the CCD surface. Several tenths of micrometers could be seen. In an animal experiment with a rabbit, configurations of arterioles and venules and their motions could be observed continuously for a night until the electrical insulation was broken. This method might be a strong weapon in artificial organs research.

Animals↗
PubMed2005

The European artificial organ scene: present status.

This article summarizes the current evolutions regarding artificial organs in Europe. The review emanates from the activities by four of the work groups of the European Society for Artificial Organs (ESAO) and is essentially based on the reports by these work groups at the latest ESAO meeting in Warsaw, Poland (2004). The topics are: apheresis, heart support, liver support, uremic toxins.

Artificial Organs↗
PubMedDate not supplied

Performance evaluation of implantable artificial organs by sound spectrum analysis.

In this paper, a sound spectrum analyzing method was proposed to pre detect malfunctions of implantable artificial organs, such as an electromechanical total artificial heart (TAH) or prosthetic valves, without any percutaneous invasion. For this purpose, a sound detecting device was developed using a high sensitivity condenser microphone with a frequency range of more than 13 kHz. Output signals of this device are sampled at 100 kHz maximally, and sampled data are stored in an IBM PC (SamBo, Korea). To remove environmental noises in the measured sound, an adaptive least-mean square algorithm was employed. Using the squared value of the sound signal, the best position where only sounds from mechanical components can be measured was found. The sound spectrum was obtained by the periodogram spectral estimating method. Experiments were performed with this system, and the results indicated that: 1) by using an adaptive noise cancelling algorithm, a more noise-free signal can be obtained; 2) the harmonics from the mechanical components of a pendulum type electromechanical TAH were approximately 1.3 KHz; 3) a spectral change was observed when we compared the power spectral densities of a normal and failed TAH; 4) the spectral shift to higher harmonics occurred with an increase in heart rate; and 5) the sound propagation properties of tissue were investigated with animal experiments. The method proposed was found to be applicable in the detection of implantable artificial organ mechanical failure by sound spectrum analysis without the need for percutaneous invasion.

Acoustics↗
PubMedDate not supplied

Occupational chemical exposures in artificial organic fiber industries.

This review discusses artificial organic fibers that are produced from materials of natural origin such as rayons, cellulose triacetates and proteins; or made from polymerised chemicals such as polyamides, polyesters, polyvinyls, modacrylics, carbon fibers, polyolefins, polyurethane and polytetrafluoroethylene. Chemicals involved include monomers, solvents, flame retardants, pigments and other additives. Occupational exposure to chemicals in the production stages are discussed and also the potential health hazards involved are reviewed. Current exposure levels, engineering controls and work practices for some of the chemicals used in the Ontario artificial fiber industry are discussed. Recommendations are made for areas that need further study and/or investigation.

Acrylic Resins↗
PubMed1988

Method of formation of artificial organ components using a plastic dispenser system manipulated by a robot.

In order to produce an artificial organ component having a complicated structure, a plastic-forming method was proposed in which small amounts of material were accumulated successively by using a dispenser system manipulated by a robot; a preliminary experiment with silicone rubber was conducted. Components of different shapes were produced, including straight tubes, tapered tubes, bifurcating tubes, tubes having leaflets on the inside, cones, spiral tubes, and tubes with a sack. This method provides the possibility of producing complicated artificial organ components, which are difficult to produce by conventional plastic-processing methods.

Artificial Organs↗
PubMed1998

In vitro thrombogenicity testing of artificial organs.

Thromboembolic complications remain as one of the main problems for blood contacting artificial organs such as heart valves, bloodpumps and others. In vitro evaluation of thrombogenesis in prototypes has not previously been part of the standard evaluation of these devices. In comparison to hemolysis testing, evaluation of the thrombogenic potential is more difficult to perform because of the complexity of the blood coagulation system. We present an in vitro testing procedure that allows the accelerated examination of the thrombogenic potential of different types of blood pumps. Additionally, first results are presented that indicate the reliability of the accelerated clotting test for mechanical heart valves. Results for the centrifugal pump BioMedicus and two microaxial pumps have shown typical thrombus formation at locations such as bearings. The results indicate that the accelerated clotting test is an excellent addition to the much more expensive animal testing of artificial organs or assist devices. In vitro testing permits studies of thrombus formation to be performed at an early stage and at low costs and also facilitates a more precise investigation of device areas known to be potential hot spots for thrombus formation.

Animals↗
PubMed1999

A preliminary study of microcapsule suspension for hemolysis evaluation of artificial organs.

A microcapsule suspension, a substitute for animal blood in hemolysis tests, has been developed for evaluation of the absolute hemolytic properties of circulatory artificial organs. The microcapsule suspension was made by dispersing microcapsule slurry into an ethylene glycol sodium chloride solution. The microcapsule slurry was composed of a leuco dye solution and polyurethane membrane made by the reaction between aliphatic poly-isocyanate and polyamine by interfacial polycondensation. The microcapsule was a small particle containing dye inside. The microcapsule suspension was white; the diameter of the microcapsules was from 5 to 100 microns. The specific gravity of the suspension was 1.024, and the membrane was elastic. The fluid showed Newtonian characteristics, different from animal blood, and its viscosity was approximately 5.8 mPa.s. After the microcapsules were destroyed, the leuco dye was extracted with n-hexane from the suspension and was measured by spectroscopy after being colored with acid ethanol. Hemolysis can be regarded as a fatigue fracture of cell membranes rather than a static fracture. The destruction of microcapsules by a Potter type tissue grinder was observed at a low stroke number region and was compared to rat blood. Moreover, hemolysis tests of a commercially available centrifugal blood pump and the prototype of our centrifugal pump for mechanism checks were carried out with bovine blood. The hemolysis level of the prototype pump increased with time while the hemolysis level of the commercial blood pump did not change as much as that of the control when both pumps were tested with the microcapsule suspension. These results are similar to tests utilizing bovine blood. Therefore, hemolysis tests of circulatory artificial organs completed with microcapsule suspension are expected to provide results similar to tests with animal blood.

Animals↗
PubMed2004

Numerical estimation of blood damage in artificial organs.

The aim of this study was to determine a method for the numerical estimation of blood damage. Normally, human or animal blood is used for in vitro evaluation of lysis by artificial organs. However, blood has some disadvantages: large biological variability and different initial test conditions lead to nonreproducible test results. For that reason, it would be an advantage to have a numerical method for blood damage estimation. This proposed method is based on the calculation of an integrated hemolysis and platelet lysis index along the path line in the flow field of the artificial organ. The time-dependent shear stress related lysis is based on known experimental data. In order to calibrate these data, the method was first applied to blood circulation in the human body. The results showed that the known data overestimate hemolysis by a factor of approximately 25. Next, the method was applied to a standard Björk-Shiley valve. The flow through a valve was simulated with the computational fluid dynamics program FLUENT. The calculation of lysis was added into FLUENT and done automatically. The results showed that the Björk-Shiley valve increased the hemolysis index by 7% if implanted in the human body circulation.

Algorithms↗
PubMedDate not supplied

A gait-powered autologous battery charging system for artificial organs.

The quality of life of patients relying on electrically powered artificial organs is currently restricted by the limited energy availability provided by portable batteries. As these patients become increasingly ambulatory, and are developing more active lifestyles, this limitation grows more apparent. Coincidentally, these patients may themselves be capable of generating electrical power as a consequence of their physical activity. Extraction of this latent autologous energy could, in turn, be used to augment charging of internal batteries--thus untethering the patient from external power for extended periods of time. In this study, the viability of deriving energy associated with natural human ambulation has been evaluated. The kinematic components of gait were evaluated to identify the largest useful forces and moments that may be harnessed as an energy source, while presenting minimal "perceived" work for the patient. It was found that the ground reaction forces associated with the heel strike and toe-off phases of the gait represent the greatest potential for usable energy. This study uses a piezoelectric array within the midsole of the shoe for the conversion of mechanical to electric energy. This power could then be easily coupled in tandem with existing transcutaneous transformers for augmenting or temporarily replacing external power sources.

Artificial Organs↗
PubMed1982

Feasibility of using an isolated intestinal segment as an artificial organ for enzyme replacement therapy.

Guinea pigs fed an ascorbic acid-deficient diet develop scurvy because of the absence of the enzyme L-gulonolactone oxidase. In theory if this enzyme is provided and its substrate L-gulonolactone is present at adequate concentrations ascorbic acid will be synthesized and the development of scurvy prevented. Using this model we tested whether a viable segment of intestine could be used to contain the administered enzyme and act as an artificial organ for the production of ascorbic acid. A surgical procedure was developed to prepare an externalized pouch of intestine with its circulation left intact. When enzyme is inserted in this intestinal bag it is not toxic and not antigenic in some animals, whereas, enzyme injected intraperitoneally is clearly antigenic. Synthesis of ascorbic acid by this artificial organ could not, however, be detected by elevation of plasma concentrations of the vitamin.

Animals↗
PubMed1994

[Mechanical hemolysis caused by artificial organs--comparison of in vitro hemolysis studies and their application to in vivo conditions].

Changes of plasma concentration are often used for in vitro characterisation of the hemolytic potency of artificial organs and apparatus. Different indices of hemolysis are derived from Hb concentration, which, in general, depend on experimental conditions and cannot be compared quantitatively or used to describe the in vivo damage. In this paper we propose a similarity number called "lysis number" that is independent of experimental conditions. It describes the probability for a single blood cell to be completely destroyed in a single pass through the corresponding artificial assist system. The concept is based on the steps: 1. Definition of "lysis number" as an index of hemolytic performance of artificial organs or implants. 2. Description of more complex hemolytic damaging processes (different hemolytic steps) that may be in series or parallel and definition of an effective lysis number. 3. Experimental in vitro estimation of each of the processes in consecutive steps. 4. Calculation of total hemolysis of the complex system using the linkage rules. 5. Application to in vivo by an appropriate differential equation in RBC mas taking into account mechanically-induced hemolysis rate, survival time of normal RBC and erythropoetic generation rate.

Erythrocyte Aging↗