System for measuring ultrafiltration rate

Claim 3

Apparatus for measuring the rate of ultrafiltration through a semipermeable membrane wherein a first fluid continously flows across one surfacE of said membrane at a first pressure and a conductive second fluid continuously flows across the other surface of said membrane at a second pressure, a portion of said first fluid ultrafiltrating through said membrane into said second fluid, comprising: first supply means for providing a flow of said first fluid across said membrane at said first pressure, second supply means for providing a flow of said conductive second fluid across said membrane at said second pressure, shutoff means for stopping the flow of said conductive second fluid across said membrane, means for maintaining a constant pressure differential between said first and second fluids, a collection chamber through which said ultrafiltrating first fluid and said conductive second fluid flow said collection chamber having a pair of electrodes between which a constant electric potential is maintained and between which there is increased current flow as said chamber receives said ultrafiltrating first fluid and said conductive second fluid drain means for emptying said collection chamber and measuring means for sensing increased current flow between said electrodes as a function of time.

Claim 4

Apparatus for measuring the rate of ultrafiltration through a semipermeable membrane wherein a first fluid continously flows across one surfacE of said membrane at a first pressure and a conductive second fluid continuously flows across the other surface of said membrane at a second pressure, a portion of said first fluid ultrafiltrating through said membrane into said second fluid, comprising: first supply means for providing a flow of said first fluid across said membrane at said first pressure, second supply means for providing a flow of said conductive second fluid across said membrane at said second pressure, shutoff means for stopping the flow of said conductive second fluid across said membrane, means for maintaining a constant pressure differential between said first and second fluids, a collection chamber through which said ultrafiltrating first fluid and said conductive second fluid flow said collection chamber having a pair of electrodes between which a constant electric potential is maintained and between which there is increased current flow as said chamber receives said ultrafiltrating first fluid and said conductive second fluid drain means for emptying said collection chamber and measuring means for sensing increased current flow between said electrodes as a function of time.

Claim 5

Apparatus for measuring rate of ultrafiltration in an artificial kidney machine having an artificial kidney membrane which has a delivery system for providing a supply of dialysate solution, comprising: blood circulation means for flowing blood across said artificial kidney membrane at a first pressure an artificial kidney membrane across which said dialysate solution flows from said delivery system at a second pressure, a first conduit for carrying dialysate solution from said delivery system to said artificial kidney membrane dialysate shutoff means upstream of said artificial kidney membrane in said first conduit for stopping the flow of dialysate across said artificial kidney membrane a second conduit which carries said dialysate solution to drain after it flows across said artificial kidney membrane means maintaining a constant pressure differential between said first pressure of blood and said second pressure of dialysate flowing across said artificial kidney membrane an enclosed membrane in said second conduit downstream of said artificial kidney membrane drain means in said second conduit upstream of said chamber for draining said chamber a pair of electrodes in said chamber and measuring means connected to said electrodes for measuring the rate of change of electrical conductivity between said electrodes caused as said dialysate solution fills said chamber.

Claim 6

Apparatus for measuring rate of ultrafiltration in an artificial kidney machine having an artificial kidney membrane which has a delivery system for providing a supply of dialysate solution, comprising: blood circulation means for flowing blood across said artificial kidney membrane at a first pressure an artificial kidney membrane across which said dialysate solution flows from said delivery system at a second pressure, a first conduit for carrying dialysate solution from said delivery system to said artificial kidney membrane dialysate shutoff means upstream of said artificial kidney membrane in said first conduit for stopping the flow of dialysate across said artificial kidney membrane a second conduit which carries said dialysate solution to drain after it flows across said artificial kidney membrane means maintaining a constant pressure differential between said first pressure of blood and said second pressure of dialysate flowing across said artificial kidney membrane an enclosed membrane in said second conduit downstream of said artificial kidney membrane drain means in said second conduit upstream of said chamber for draining said chamber a pair of electrodes in said chamber and measuring means connected to said electrodes for measuring the rate of change of electrical conductivity between said electrodes caused as said dialysate solution fills said chamber.

Claim 7

The device of claim 3 in which said measuring means comprises: an oscillator for providing a constant AC voltage through a first transformer to said electrodes in said chamber and through a second current transformer amplifier means for amplifying the output of said second current transformer, peak value detector means for converting the output of said amplifier means to a direct current voltage representing the amount of fluid in said chamber, and differentiator means which receives the output of said peak value detector means and converts said output to a voltage proportional to the rate of increase of fluid in said chamber.

Claim 8

The device of claim 4 further comprising: indicator means for displaying the output of said differentiator means.

Claim 9

The apparatus of claim 3 wherein said means for maintaining a constant pressure differential comprises: a first summing amplifier a first pressure transducer which provides a first output current flowing into the bus of said first summing amplifier proportional to positive venous blood pressure a second pressure transducer which provides a second output current flowing into the bus of said first summing amplifier proportional to negative dialysate pressure at the output of said kidney membrane said first summing amplifier converting said first and second outputs to a first summer output negative voltage proportional to the actual transmembrane pressure differential a second summing amplifier for receiving said first summer output means for providing current to the bus of said second summing amplifier proportional to a desired transmembrane pressure differential said second summing amplifier producing at its output an error signal proportional to the difference between actual transmembrane pressure differential and desired transmembrane pressure differential pump means downstream of said kidney membrane for pumping dialysate solution a motor for driving said pump means and control means for regulating the current flow through said motor in response to said error signal such that the torque of said motor is varied in a manner to adjust the dialysate pressure to cancel said error signal and to maintain the desired transmembrane pressure differential.

Claim 10

In an artificial kidney machine having a dialysate delivery system located upstream from an artificial kidney membrane, a system in which the variables of the pressure of dialysate flowing across the kidney membrane, the dialysate flowrate across the membrane and the dialysate mix ratio may each be varied independently of the other two comprising: a backpressure regulator downstream of said dialysate delivery system but upstream of said kidney membrane, and means located downstream of said kidney membrane for maintaining a constant transmembrane pressure differential.

Claim 11

In an artificial kidney machine having a dialysate delivery system located upstream from an artificial kidney membrane, a system in which the variables of the pressure of dialysate flowing across the kidney membrane, the dialysate flowrate across the membrane and the dialysate mix ratio may each be varied independently of the other two comprising: a backpressure regulator downstream of said dialysate delivery system but upstream of said kidney membrane, and means located downstream of said kidney membrane for maintaining a constant transmembrane pressure differential.

Claim 12

The system of claim 7 in which said backpressure regulator comprises: a housing having an input cavity for receiving dialysate from said delivery system and an output passageway connected to said input cavity through which dialysate flows to said kidney membrane a needle valve which seats in said outlet passageway and a diaphragm which encloses said input cavity and which resiliently urges said needle valve into said output passageway in response to a lowering of dialysate pressure in said input cavity.

Claim 13

The system of claim 7 wherein said means for maintaining a constant transmembrane pressure differential comprises: a first summing amplifier a first pressure transducer which provides a first output current flowing into the bus of said first summing amplifier proportional to positive venous blood pressure a second pressure transducer which provides a second output current flowing into the bus of said first summing amplifier proportional to negative dialysate pressure at the output of said kidney membrane said first summing amplifier converting said first and second outputs to a first summer output negative voltage proportional to the actual transmembrane pressure differential a second summing amplifier for receiving said first summer output means for providing current to the bus of said second summing amplifier proportional to a desired transmembrane pressure differential said second summing amplifier producing at its output an error signal proportional to the difference between actual transmembrane pressure differential and desired transmembrane pressure differential pump means downstream of said kidney membrane for pumping dialysate solution a motor for driving said pump means and control means for regulating the current flow through said motor in response to said error signal such that the torque of said motor is varied in a manner to adjust the dialysate pressure to cancel said error signal and to maintain the desired transmembrane pressure differential.