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At least 307 records · Page 17Linked to original sources
PubMed1986

Totally implantable artificial organ: cardiac prosthesis.

This article reviews the current status of completely implantable cardiac prostheses, with an emphasis on those systems presently under development at The Cleveland Clinic Foundation (CCF). Such devices have been one of the final goals of artificial heart research since 1957, when Dr. Kolff initiated these studies in Cleveland. Although earlier plans aimed at using radioisotopes as the energy source, more recently, due to public opinion and sociopolitical influences, the shift has been towards exclusive use of electrically activated energy converters. These systems can be roughly broken down into two groups according to the powertrain configuration. In the first group, electric heating coils maintain liquid salts in thermal batteries at temperatures close to 500 degrees C. This thermal energy is then converted (through a Stirling cycle) to mechanical motion of the pusher plate (PP) which in turn acts on the blood. Two such systems (emphasized in this article) are under development here at CCF in joint efforts with Nimbus Corporation and the University of Washington, respectively. In the second group of ventricular assist systems, electric energy is converted directly to PP motion through rotating cams, solenoids, or electrohydraulic transmission systems. At least four American contractors are working at the preclinical stage on this group of devices. One in particular, the CCF-Nimbus system, consisting of a biolized surface blood pump, an electrohydraulic energy converter, and a compliance chamber to handle the variable volume behind the PP, is described in depth in this discussion. In terms of future prospects, it is forecasted that by 1988, the completely implantable VAS will be used clinically, and that by 1994, a specially designed total artificial heart (nontethered patient) would be ready for human use.

Electric Power Supplies↗
PubMed1990

Platelet function in cardiopulmonary bypass and artificial organs.

Extensive contact between blood and synthetic surfaces is associated with both quantitative and qualitative changes in platelet function. Cardiopulmonary bypass is associated with a decline in the circulating platelet count, release of platelet alpha granules and possibly platelet dense and lysosomal granule release, and a prolongation of the bleeding time. It is assumed that these platelet alterations contribute to postoperative blood loss and reoperation for bleeding. Improvements in technology have reduced but not eliminated the adverse platelet changes. Temporary inhibition of platelet function during surface contact has achieved additional improvement in the setting of heparin-induced thrombocytopenia but is not yet suitable for "routine" open heart surgery. Long-term cardiopulmonary bypass or extracorporeal circulation membrane oxygenation is receiving increased use during acute respiratory insufficiency. Systemic anticoagulation is required. Bleeding and platelet consumption continue as clinical problems and are treated by repeated platelet transfusion. Because no air interface is present in this setting and the synthetic surface is homogeneous this would appear to be the ideal area for application of platelet functional inhibition and synthetic surface passivation to reduce platelet consumption. Although still under review by the Food and Drug Administration, pulsatile devices, including the total artificial heart, increasingly are being used to provide temporary support for the failing heart. Furthermore, it is likely that totally implantable devices will become available in the very near future. Considering that thromboembolism is a major problem for recipients of mechanical valves, it is likely that thromboembolism will persist as a limiting factor in the further implementation of pulsatile devices. It is assumed that imaginative antithrombotic therapy will be required and that platelet activation will be fundamental to the thrombotic process. Platelet behavior in this setting, however, remains incompletely characterized. The analytical methodology that has been used to assess platelet behavior during cardiopulmonary bypass should be applied to the pulsatile devices as well and results correlated with clinical problems. This should permit standardization of antithrombotic therapy and rational use of platelet functional inhibition.

Assisted Circulation↗
PubMed1999

Detection of epileptiform discharges in the EEG by a hybrid system comprising mimetic, self-organized artificial neural network, and fuzzy logic stages.

OBJECTIVE: A multi-stage system for automated detection of epileptiform activity in the EEG has been developed and tested on pre-recorded data from 43 patients. METHODS: The system is centred on the use of an artificial neural network, known as the self-organising feature map (SOFM), as a novel pattern classifier. The role of the SOFM is to assign a probability value to incoming candidate epileptiform discharges (on a single channel basis). The multi-stage detection system consists of three major stages: mimetic, SOFM, and fuzzy logic. Fuzzy logic is introduced in order to incorporate spatial contextual information in the detection process. Through fuzzy logic it has been possible to develop an approximate model of the spatial reasoning performed by the electroencephalographer. RESULTS: The system was trained on 35 epileptiform EEGs containing over 3000 epileptiform events and tested on a different set of eight EEGs containing 190 epileptiform events (including one normal EEG). Results show that the system has a sensitivity of 55.3% and a selectivity of 82% with a false detection rate of just over seven per hour. CONCLUSIONS: Based on these initial results the overall performance is favourable when compared with other leading systems in the literature. This encourages us to further test the system on a larger population base with the ultimate aim of introducing it into routine clinical use.

Adult↗
PubMed1999

Doppler aortic flow pattern in the recovering heart treated by cardiac extracorporeal membrane oxygenation International Society for Artificial Organs.

A 39-year-old man was admitted to our hospital because of chest pain and was diagnosed with severe heart failure due to viral myocarditis. Intraaortic balloon pumping (IABP) and cardiac extracorporeal membrane oxygenation (ECMO) were employed. Using Doppler echocardiography, we evaluated the descending aortic blood flow pattern. When cardiac ECMO was initiated from the right femoral artery, a strong backflow of blood generated by the pump was observed in the abdominal aorta because the forward flow from the native heart was weak. Two days later, the blood flow was reversed from the thoracic to abdominal aorta; the natural flow was strengthened because the native heart had improved. The observation of this phenomenon is helpful for determining the recovery of cardiac function under cardiac ECMO support.

Adult↗
PubMed1979

Defining indications for artificial organ support in respiratory failure.

Patients with acute respiratory failure who have high mortality risk can be analyzed according to the methods outlined above. Some (but not all) of the high mortality risk patients can be identified early in the course of respiratory failure. Temporary support with ECMO is indicated in these patients if there are no signs of irreversible damage.

Adult↗
PubMed1999

Atomic absorption spectrophotometry (AAS) for the evaluation of metallosis in prostheses and artificial organs: a new approach.

To study the presence of metals in body fluids and tissues after implantation of metallic biomaterials and possible related diseases, a new approach in Atomic Absorption Spectrophotometry (AAS) was developed. This technique was compared to three traditional methods: mineralisation with acid digestion (method A) also known as "wet method", dry ashing (with or without oxygen) (method B); classic Kjeldaal (method C). The new approach (method D) modifies the mineralisation phase and the instrument operating instructions. Al, Na, Cr, K, Ni, Co, Ti, Fe, Hg, Pb, V, Sb and Cu levels were tested with the four methods on bone, muscle, cartilage, skin, brain, lymph nodes, blood, urine, and hair. Test results were checked by the addition method. Results demonstrated a significantly higher percentage of Al, Cr, Ni, Ti and Hg recovery with the new approach. The advantages of method D are no residue, no redox reaction, insignificant loss of analytes and enhanced sensitivity (at ppb level vs ppm of the other methods). This approach should be considered especially when testing heavy metals and complex matrices. Its disadvantages are that it is more time consuming and requires the presence of an operator.

Humans↗