Target temperature of local cryotherapy

BACKGROUND: Local cryotherapy (LC) is a promising method for treating various diseases, achieving the effects of anesthesia, and a reduction of inflammation. From a physical viewpoint, the main factor of efficiency is achieving the target temperature on an impact area surface. At the same time, during the procedure, the surface temperature of the tissue should not fall below the minimum permissible temperature for safety.

AIMS: Identification of the ranges of temperature targets and temperature limits in terms of safety parameters based on the results of a literature analysis, performing experiments with the use of an ice bag for cooling the biotissue phantom, and determining the most appropriate impact modes.

MATERIALS AND METHODS: A series of experiments was performed on the developed stand to compare two contact cooling modes of LC, depending on the working substance used (sodium chloride solution or a mixture of ice and water). The comparison was conducted according to the following parameters: the time to reach the target temperature on the surface and the temperature at the depth of the model medium. The temperature was measured using resistance thermometers (Pt100).

RESULTS: When cooled with a sodium chloride solution, the surface temperature of the model medium dropped to 10 °C in 6 min of exposure and reached its minimum value of 6.2 °C after 17 min. In the case of using a mixture of water and ice, a minimum temperature of 12.5 °C was reached in 58 min. In both cases, the minimum temperature at a depth of 8 mm was approximately 16 °C, reached in 20 min and 60 min with a solution of sodium chloride and a mixture of water and ice, respectively.

CONCLUSIONS: On the basis of the experiments, the most suitable contact cooling mode with the use of an ice bag was determined—using sodium chloride as the working substance at an initial temperature of −18.4 °C, with a possible impact time of 6–25 min.