A disposable real-time closed catheter urine output monitoring system. The monitoring system of the invention can measure urine outputs at both high and low urine flow in real time, using a pressure chamber in the form of a hollow body having an input port for coupling to a tube connected to a catheter for collection of urine from a patient, an exit port coupled to a collection container and a vent port, such that air may flow through the vent, but urine is blocked by the vent. A sensor measures flow from the exit port of the pressure chamber into the collection container, and a pressure sensor may be included to measure pressure in the pressure chamber. The invention also provides a method of using the apparatus in a real-time monitoring system.
