Patent attributes
Improvements in fluid volume measurement systems are disclosed for a pneumatically actuated diaphragm pump in general, and a peritoneal dialysis cycler using a pump cassette in particular. Pump fluid volume measurements are based on pressure measurements in a pump control chamber and a reference chamber in a two-chamber model, with different sections being modeled using a combination of adiabatic, isothermal and polytropic processes. Real time or instantaneous fluid flow measurements in a pump chamber of the diaphragm pump are also disclosed, in this case using a one-chamber ideal gas model and using a high speed processor to obtain and process pump control chamber pressures during fluid flow into or out of the pump chamber. Improved heater control circuitry is also disclosed, to provide added or redundant safety measures, or to reduce current leakage from a heater element during pulse width modulation control of the heater element. Improvements are also disclosed in an application of negative pressure during a drain phase in peritoneal dialysis therapy, and to control an amount of intraperitoneal fluid accumulation during the therapy. Improvements in efficiency are also disclosed in movement of fluid into and out of a two-pump cassette and a heater bag of the peritoneal dialysis cycler, and in synchronization of operation of two or more pumps in the peritoneal dialysis cycler or other fluid handling devices using a multi-pump arrangement.
