BACKGROUND: local cryotherapy (LC) is a promising method of treating various diseases, as a result of which the effects of anesthesia and reduction of inflammation are achieved. The main factor of efficiency from a physical point of view is the achievement of the target temperature on the surface of the impact area. At the same time, during the procedure, the surface temperature of the tissue should not fall below the minimum permissible the limit temperature for safety. AIMS: identification of the range of target and limit temperatures in terms of safety parameters based on the results of literature analysis, carrying out experiments with the use of ice bag for cooling the biotissue phantom, determining the most appropriate impact modes. MATERIALS AND METHODS: a series of experiments was carried out on the developed stand to compare the two modes of the contact method of LC, depending on the working substance used (sodium chloride solution, a mixture of ice and water). The comparison was carried out according to the following parameters: the time to reach the target temperature on the surface, the temperature at the depth of the model medium. The temperature was measured by resistance thermometers (Pt100). RESULTS: when cooled with a sodium chloride solution, the surface temperature of the model medium dropped to 10 C in 6 minutes of exposure, and after 17 minutes reached its minimum value of 6.2 C. In the case of using a mixture of water and ice, the minimum temperature of 12.5 C was reached in 58 minutes. The minimum temperature at a depth of 8 mm in both cases was approximately the same and was about 17 C. It was reached by 19 minutes with a solution of sodium chloride and for 58 minutes with a mixture of water and ice. CONCLUSIONS: as a result of the experiments carried out, the most suitable contact cooling mode with the use of ice bag was determined - a mode using sodium chloride as a working substance with an initial temperature of minus 18.4 C with a possible impact time from 6 to 19 minutes.
BACKGROUND: Local cryotherapy (LC) is one of the physiotherapeutic treatment methods of various diseases, including musculoskeletal disorders. When choosing the method and exposure modes, the medic relies on his experience and data from LC equipment manufacturer. This is not enough for correct dosing, impact control and understanding of the relationship of one or another effect from the cooling parameters of the biotissue. Therefore, it is advisable to conduct a study of different methods of LC and modes to perform effective and safe impact. The temperature on the surface of the biotissue acts as a convenient and measurable factor of efficiency and safety. Earlier analysis shows that the target temperature is 10 2 C, the limit temperature is 0 C, when lowering below which tissue damage is possible. AIM: Experimental comparison and identification of the most suitable modes of two different methods of contactless local cryotherapy. MATERIALS AND METHODS: An experimental installation was developed and created. A series of experiments was carried out on a model medium with thermophysical properties close to biotissues. The comparison of liquid nitrogen and air flow cooling is carried out. The temperature was measured with resistance thermometers (Pt100) on the surface and in the depth of the model medium. RESULTS: When cooled by liquid nitrogen vapors from a distance of 10 and 15 cm from the surface, the accepted average target temperature of 10 C was reached in 1.8 and 4.4 min, and at a depth of 8 mm, the temperature was 26.4 and 23.7 C, respectively. When cooled with air from a distance of 10 cm from the surface with maximum and minimum flow, the target temperature was reached in 2.5 and 13.3 min, at a depth of 8 mm, the temperature was 22.9 and 16.0 C, respectively. When cooled by air from a distance of 15 cm, the temperature value did not reach the target. The less intense flow made it possible to lower the temperature inside the model medium more strongly, while having a weaker effect on the surface. This effect can potentially be positive in the treatment of musculoskeletal disorders, mainly joints. CONCLUSIONS: The most suitable modes of the considered methods that meet the requirements of efficiency, safety and convenience of practical implementation are identified. For cooling by liquid nitrogen vapors, this is a mode spraying at a distance of 15 cm with a stable technique with a possible exposure time from 4.4 to 15 minutes. For air flow cooling, this is a mode with a stable technique with a constant flow with the nozzle fixed relative to the surface of the model medium at a distance of 10 cm with a minimum flow rate (350 l/min) with a possible exposure time from 13.3 to 21.5 min.
Local low-temperature impact on biological tissues, depending on the temperature reached, can lead to destructive, preserving or therapeutic effects. The article describes the principle of a unified approach for the transition from mass recommendations for the dosing of local low-temperature exposure to personalized. It is proposed to divide the exposure process into three stages: planning, provision and control, analysis of compliance with the planned and received dose. Examples of solving the problems of heat transfer in cryosurgery and cryopreservation are given for a possible improvement of the planning stage. In the framework of the first direction, two cases are considered. The first is to improve the accuracy of prostate cryoablation planning. The second is a comparison of the effectiveness of various materials of cryosurgical applicators: copper, brass and artificial sapphire, which can be used to influence and control the freezing zone by optical methods. Within the framework of the second direction, a case of using local low-temperature exposure to solve the problem of simultaneously preserving the framework of a biological tissue and removing a layer of donor cells, called decellularization, is shown for the purposes of transplantology. The results of the above examples can potentially be used in planning a local low-temperature impact. Based on this approach, it is possible to develop methods and technologies of a new generation with the possibility of accurate dosing.
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