Yu. M. Kiselev

An investigation of flow structure in an artificial heart ventricle

In order to improve AV construction, it is necessary to solve a series of bioengineering problems, including the optimization of AV geometry and the selection of artificial heart valve (AHV) orientation in the AV. Toward this goal, a series of studies were conducted concerning flow structure in model AVs, covering among other things, planar models [6], glass models [5], a specially prepared AV (optical knife method) [3], during orientation of an AHV disk on the AV membrane (optical polarization method) [6], and on AV output [2]. From the viewpoint of the authors, practical interest has focused on the investigation of flow structure throughout the volume of actually utilized AVs [4] with a series of AHVs in order to provide fabrication recommendations leading to the improvement of existing and workable AV and AH constructions. Visualization studies of flow structure were carried out using the laser knife method. The principle of this method consists of the following. A light beam is formed by a lens system, a mirror and slitted diaphragm into a fine beam and then guided into the cross section of the model to be investigated. A solution is introduced into the fluid flow having fluorescent properties such that the maximum fluorescent radiation lies in a longer wavelength region than the maximum spectral light intensity. The molecules of the fluorescent substance, when the pencil of light rays strike the flowing fluid, initiate light emission of a characteristic fluorescent wave length. Since the characteristic time for the process of light absorption, molecular excitation, and radiation (fluorescence) is short, usually 10 -~ to 10 -s sec, the resulting pictures portray the instantaneous distribution of the fluorescent substance in the complete stream. It should be pointed out that the presented kinogram shows the instantaneous distribution of the fluorescent substance in a section not a projection, as would be the case when using a dye solution. A schematic diagram of the experimental setup is presented in Fig. i. The AV 1 and AHVs 2 were placed in a rectangular-shaped vessel 3 filled with water. Water was utilized as the working fluid. Fluid was supplied to the AV from an upper supply tank 4 and ran off into a lower tank 5. Illustrated in Fig. 2 is the variant 1 orientation in the AV of the EMIKS type AHV disks, where the right valve is the input and the left is the output. Flow visualization was carried out at sections A--A and B--B. Visualization was conducted under stationary flow conditions with two different values for the flow rate: gl = 0.6

Thermodynamic bases and physiological criteria for the application of heat engines for driving artificial heart ventricles

ConclusionWe have considered the thermodynamic bases for the application of heat engines to drive the ventricles of artificial hearts in humans. An analysis of the Carnot, Brighton, Stirling, and Rankine cycles indicated that the Rankine cycle is preferable, specifically in its implementation in the steam piston engine. In this context it is essential that the optimal operating frequency for the motion of the steam engines piston lies in the range of physiological frequencies for the contraction of the human heart, which allows the application of this engine for driving IAH ventricles without converting frequencies.We have further considered the physiological criteria for the application of heat engines as part of IAH, such as overall size, mass, efficiency, and provision of hemodynamics. It is pointed out that from the perspective of physiological compatibility the steam piston engine is optimal. With this in mind, for the implanting of a complete IAH it is necessary to supply separate drives for the ventricles by utilizing independent piston engines, as achieved in the “Mikron” project.

Artificial-heart blood heat exchangers with radioisotopic power supplies

Conclusions1. An experimental model of an artificial-heart heat exchanger has been developed which preserves thrombosis-resistant properties for long periods of time.2. An analytic expression has been derived that relates the maximum blood temperature rise, the quantity of heat power released to the blood, the length of the heated section of the heat exchanger, and the Reynolds number (640<Re<1050).3. The specificity of the local thermal effect on the fibrinothrombocytic structure in vivo has been revealed.4. Supplemental thermal loads on a homoisothermal organism amountingto one-half of its normal metabolism has no significant effect on the chemical thermogenesis structure.5. The supplemental heat is dissipated by the respiratory system.

Power units used in an implanted artificial heart and auxiliary circulation systems

ConclusionA brief analysis of various designs of power units shows that the partially self-contained power units are the simplest to manufacture. Here there is no need to solve such important problems as extra pure Pu238, i.e., having a minimum radiation effect on the body, protection of the body from this effect, dissipation of large quantities of heat, high cost, etc. Other requirements imposed on power units are also met considerably more simply in this case.However, the value of the self-contained AH as a means of returning the patient to normal activity surpasses many times that which can be expected from the partially self-contained AH.From this viewpoint, the scheme of a partially self-contained power unit with the use of a heat engine as a converter deserves special attention as it permits changing to a completely self-contained AH with minimum design changes.