In an extracorporeal blood treatment apparatus, a user interface (22) has a touch screen for displaying two bar-graphs (24) of pressures in the extracorporeal blood circuit. By touching a bar-graph three alpha-numeric values appear: a reference value (29), an upper safety interval (28) of the pressure, comprised between an upper limit value and the reference value (29), and a lower interval value (30), comprised between the reference value and a lower limit value. The reference value is a measured pressure value. Four buttons also appear on the display for input of modifications to the upper interval and the lower interval. The setting of the total pressure safety interval is simple and immediate.
