[Comparison of cryogenic support systems of surgical instruments for the local destruction of large biological tissue lesions].

Of two types of systems for cryogenic support (SCS) of surgical instruments made with open and closed contours those of the discharge type meet to a greater extent basic requirements on the SCS as concerns destruction of extensive areas of the biological tissue. These SCS permit it more readily to withstand optimal conditions of cooling, can secure better reliability in performing operations, offer greater possibilities for unification of parts in packing up the set and for covering a wider range of operations. In cases when it is important to provide for self-containment and a longer period of continuous operation the application of the SCS with a closed contour is more advisable.

[Choice of working temperatures for cryo-instruments used for local destruction of biological tissue].

When utilizing low temperatures for irreversible destruction of affected biological tissues it is important that one should have a clear idea as to the boundary of necrotic alterations. The correlation between the depth of necrosis and that of freezing, the rate of the tissue congelation, the period of cryogenic action, the temperature of the cryoinstrument and its structural shape, all these factors are analytically interrelated and this enables it to establish optimal performance characteristics in congelation of different tissues. In most cases satisfactory performance characteristics in freezing biological tissues can be achieved by using liquid nitrogen.