A flow sensor system for ventilation treatment comprises a flow conduit configured to allow gas flow between a first region and a second region, the flow conduit defining a lumen for the gas flow; a flow restrictor disposed within the lumen of the flow conduit between the first region and the second region; a first absolute pressure sensor disposed adjacent to the first region of the flow conduit and configured to measure a pressure of the gas flow at the first region of the flow conduit; and a second absolute pressure sensor disposed adjacent to the second region of the flow conduit and configured to measure pressure of the gas flow at the second region of the flow conduit.