Flow balancing devices, methods, and systems

A medical treatment system, comprising:

• a flow balancing fluid management element configured to pump fluid from a patient interface device during a treatment and configured to pump fluid into the patient interface device during the treatment, the flow balancing fluid management element including a synchronization mechanism that is configured to proportion flow to and from the patient interface device in a predefined ratio during the treatment;
• the patient interface device being a device that interfaces with a patient fluid compartment including at least one of a dialyzer, a hemofilter, a hemodiafilter, an ultrafilter, and a plasmapheresis device;
• a proportioning bypass channel that includes a proportioning bypass pump and configured to pump fluid to or from the patient interface device in a predefined amount that has a predefined relationship to flows in said flow balancing fluid management element so as to produce a predefined net withdrawal from, or infusion into, a patient;
• a controller configured to control at least the proportioning bypass pump and including a processor programmed to regulate a rate of flow through the proportioning bypass pump to achieve the predefined net withdrawal from, or infusion into, the patient;
• and
• an infusion circuit connectable to a source of fluid and including an infusion circuit pump and connected to one or both of blood lines connected to a patient access, wherein
• at least a portion of the infusion circuit is selectively connectable to the proportioning bypass channel such that the infusion circuit pump and the proportioning bypass pump are connected in series through a pressure sensor, and
• the controller is programmed to calculate and store flow correction data responsively to a signal from the pressure sensor and further to modify a flow rate of said infusion circuit pump responsively to said flow correction data.