A pressure sensing device (1) adapted for having a liquid flowing there throughand for sensing the pressure of said liquid. The device has a casing (2) being fluid-tightlydivided into a first (3) and a second chamber (4) by a flexible, impermeable wall(5). The first chamber (3) has a first opening (6) for the liquid, said openingbeing placed at the lower part of the chamber (3), and a second opening (7) for theliquid, said opening being placed at the top of the first chamber (3). The secondchamber (4) has a measuring port (8), which is connectable to a pressure transducer(9) for bringing the second chamber (4) into gas-tight communication with thepressure transducer (9). The device has a first orifice (10) for the liquid into/outof the device (1), which orifice is placed at the upper part of the device at a higherlevel than the second opening (7). A first channel (11) is connecting the firstorifice (10) with the first opening (6). A second orifice (12) for the liquid outof/into the device (1) is placed at the lower part of the device at a lower levelthan the first opening (6). A second channel (13) is connecting the second opening(7) with the second orifice (12). In a first embodiment the highest level of thefirst chamber (3) is at the same level as or at a higher level than the highest levelof the second channel (13). Use of such a pressure sensing device in a connectingstructure for an extracorporeal blood treatment machine is also included.
