A method for controlling or regulating the pressure, which prevails within a heating bag of a tubing system used for the treatment, wherein the method encompasses the steps: Determining the pressure； comparing the determined pressure with a reference pressure or detecting its state with respect to a reference pressure range and changing a treatment parameter of the treatment of the patient or suggesting a correction of the treatment parameter in case the determined pressure is below or above, respectively, the reference pressure or outside the reference pressure range.
