The fluid control unit (or just control unit or fluid control module or other similar variations) is used to move and control the flow of fluids essential for performing CRRT therapy.
Control units generally have several features including:
Air detector (shown right) to detect air bubbles in the tubing before the blood is returned to the patient. The detector triggers an alarm if air bubbles are detected in the return line blood. Shown right is an air detector on the Prisma machine. Most air detectors can also detect if tubing is in the air detector as a safety feature.
Clamp (shown left) which closes if the air detector detects air bubbles in the blood. The clamp is positioned below the air detector. In the Prisma clamp shown the silver part pushes down on the tubing completely stopping the blood flow, additionally the pumps stop when the alarm is triggered.
Blood leak detector (shown right) detects blood in the effluent line, an alarm is sounded if blood is detected. The dectector can generally catch less than 1% cells in the fluid. However, you can often detect blood cells in the line with the naked eye before the detector alarms. Patients with certain liver conditions require recalibration of the blood leak detector. Air bubbles will also trigger the blood detector alarm.
Currently the most widely used fluid control units are built by Gambro, the Prisma and the newer Prismaflex.
I will not vouch for this information, but I've heard Gambro's Prisma machines cost about $25,000 and Prismaflex machines cost about $40,000.