Patent ID: 7776006

Claim:
A medical fluid pumping system comprising: a medical fluid pump; a first pressure chamber separate from and connected fluidly to the medical fluid pump; a second pressure chamber separate from and connected fluidly to the medical fluid pump; first and second pressure sensors connected operably to the first and second pressure chambers, respectively; at least one processor operable with the pressure sensors to calculate a volume of gas in the medical fluid pump prior to a pump-out stroke using a reading from the first pressure sensor after exposing the pump to gas pressure from the first pressure chamber and to use the calculated volume of gas in combination with a known volume of the second pressure chamber and a pressure decay reading taken via the second pressure sensor during the pump-out stroke to calculate at least one volume of fluid pumped during the pump-out stroke; and wherein the medical fluid pump is exposed to gas pressure from the second pressure chamber to perform the pump-out stroke.