Patent ID: 8192367

Claim:
A system for monitoring respiration, comprising: a duct configured to allow a fluid to flow therethrough; a flow restricting element in the duct, the flow restricting element having a flow resistance, the flow restricting element shaped symmetrically with respect to an axis perpendicular to a direction of flow such that, in operation, velocity of the fluid is substantially equal upstream and downstream of the flow restricting element; a single pressure sensor arranged in the duct proximate a patient end of the flow restricting element, the single pressure sensor configured to measure a pressure of the fluid at a single location; an outlet valve coupled to an end of the duct opposite the patient end, the outlet valve having a flow resistance, the outlet valve configured to allow the fluid to exit the duct to a substantially constant pressure; and a processing unit coupled to the single pressure sensor, the processing unit being configured to determine a flow rate based on the pressure measurement of the fluid from the single pressure sensor relative to the substantially constant pressure and based on the flow resistance of the flow restricting element and the flow resistance of the outlet valve.