Subzero Nonfreezing Preservation Of Kidney And Basic Study On Corresponding Issue

The paper focus on the heat and mass transfer mechanism for complex biotissuepreserved at subzero nonfreezing temperature. A series research was conducted fromcell experiments to organ transplantation. The characteristics of heat and mass transferof complex biological tissue is studied systematically in the subzero nonfreezingtemperature. The cryomicroscopic is used to study the pattern of heat and masstransfer during cooling. The transient temperature field during cooling process isobtained according to the real shape of the bio-tissue. A more comprehensiveunderstanding of the mechanisim of subzero nonfreezing preservation is achievedfrom the macro and micro level.The freezing process below freezing point was analyzed. The freezing injury isstudied through three aspects including: the characteristic of osmosis, mechanicalinjury and intracellular ice formation. The mechanism of injury is also discussed.The main contents for organ preservation include:(1) The physical model of theblood vessel trees is reconstructed. And the numerical simulation of3-D temperaturefield during perfusion is conducted on the basis of blood vessel.(2)The temperaturefield of kidney during perfusion is profoundly heterogeneous at multiple spatial scalesdue to the asymmetric branching of the intramural vascular tree. The heterogeneoustemperature field and temperature change results in thermal stress associated with thethermal strain. To solve these complicated heat transfer and thermal stress problems, amodel and a simulation method calculated by Ansys Workbench are presented in thispaper, with which transient temperature field, the transient stress field inside thekidney during perfusion can be calculated and analyzed. In the simulation, the porousmedia model has been used to solve a general set of heat and mass transfer equationsfor coolant flows in the tiny capillaries and its surrounding biological tissue. The renaltissue and the blood vessel walls are considered as the solid material. The relationshipbetween the temperature field and the thermal stress is analyzed. The aim ofreconstruction of the temperature and thermal stress field is to explore biomechanical effect by cold perfusion and analyze the physical injury caused by the tiny thermalstress.(3) For the basic study of subzero nonfreezing temperature preservation ofcomplex biotissue, the freezing point of renal cell suspension and renal organ weredetermined. The preservation effect at different temperature is compared. Thebiotissue preserved at freezing point3-4℃lower than the clinical achieves betterresults.Subzero nonfreezing temperature preservation (-0.8℃) can effectively inhibit thebasal metabolic rate, reduce energy consumption of cells and inhibit cold-inducedapoptosis. The kidney preserved at freezing point is used to renal autotransplantation.The renal preserved for more than30hours keeps good results. The combination ofbio-heat transfer and biomedical research achieves a theoretical concise andtechnological innovation.