Apparatus formed by a shell that may be placed around a part of the body, wherein said shell comprises: an inlet that may be connected to a gas source and an outlet to evacuate the gases present inside the shell； at least two complementary portions defining between them a cavity with a cross section that is larger than that of the part of the body to be treated, characterized in that the walls of the two complementary portions have an average heat conduction that is lower than 65 mW/m·K measured according to EN-12667.
