Abstract: Systems for monitoring fluids such as blood being treated extracorporeally are disclosed, including a monitor for monitoring the fluid flow through a tube system between a fluid inlet, fluid treatment means and a fluid outlet. The monitor disclosed includes a monitor housing which contains at least one pressure sensor, and a cassette which is adapted to be removably coupled to the monitor housing, the cassette including pressure transmission ducts for transmitting the pressure within the tube system to a pressure transmitting cavity adapted to be juxtaposed with the pressure sensor when the cassette is coupled to the monitor housing so that the pressure within the tube system can be directly measured by the pressure sensor when the cassette is coupled to the monitor housing. In one embodiment of the monitor the cassette includes a portion of the tube system, while in another embodiment a conventional tube system can be affixed to the cassette.

Abstract: An apparatus is disclosed for measuring the pressure of a fluid comprising a pressure sensing element and a pressure transmitting element. The pressure transmitting element has at least one inlet for receiving the fluid whose pressure is to be measured and a pressure transmitting wall member in fluid communication with the inlet, whereby the pressure transmitting wall member may be brought into contact with the pressure sensing element and a source of vacuum for drawing the pressure transmitting wall member against the pressure sensing element so that the pressure sensing element can substantially measure the absolute pressure of the fluid.