Open patient fluid management method and system

An open patient fluid management system for use with a semipermeable membrane device comprising:

• first volumetric metering means having an input coupled to a source of fresh fluid and an output coupled to an input of the membrane device, for metering a first volume of fresh fluid into the membrane device during an operational cycle;
• membrane means for transferring a second volume of fluid between the patient and the membrane device during said operational cycle;
• pump means having an input coupled to an output of the membrane device for withdrawing a third volume of spent fluid from the membrane device to a pump means output during said operational cycle;
• second volumetric metering means having an input coupled to the pump means output and having an output coupled to a first drain, for metering a fourth volume of fluid from the pump means output to the first drain during said operational cycle;
• open drain means having an input coupled to the output of the pump means and an output coupled to a second drain open to atmospheric pressure, for passing continuously any excess of the third volume of fluid over the fourth volume to the second drain, whereby an open system is maintained.

A system for passing fluid through a semipermeable membrane device comprising:

• first and second twin chambered pump means, each having an affluent chamber and an effluent chamber separated by a movable diaphragm, each such chamber having an input port and an output port, for metering dialysate into and out of the membrane device;
• a plurality of controllable valve means connected to said chamber ports for controlling the flow of dialysate into or out of the respective chamber, said valve means being operable to controllably open and close the ports with which they are associated;
• the input port of each affluent chamber being coupled through one of said valve means to a source of fresh fluid;
• the output port of each affluent chamber being coupled through one of said valve means to an input of the membrane device;
• the input port of each effluent chamber being coupled through one of said valve means to an output of the membrane device;
• and the output port of each effluent chamber being coupled through one of said valve means to a spent fluid output circuit;
• electronic control means for configuring the plurality of valve means into at least two operational states;
• in the first operational state the valve means being operated to open the following first set of ports:
• the input port of the first pump means affluent chamber, the output port of the first pump means effluent chamber, the output port of the second pump means affluent chamber, and the input port of the second pump means effluent chamber, and to close the remaining second set of ports;
• in the second operational state the valve means being operated to close the first set of ports and to open the second set of ports;
• and
• electronic clock means for causing the electronic control means to alternate periodically between the first and second states.