GB2081119A

GB2081119A - Pressure and fluid flow activated, simplified proportioning system

Info

Publication number: GB2081119A
Application number: GB8118795A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-06-19
Filing date: 1981-06-18
Publication date: 1982-02-17
Also published as: GB2081119B; FR2547412A1; CA1188177A; JPS5725860A; DE3204520A1

Abstract

A hemodialysis apparatus for proportioning diluent and concentrate for blood treatment has a mixing and proportioning tank 32, a pump 22 for supplying diluent and concentrate to the proportioning tank means for filling and emptying the tank dependent upon pressure and flow in the proportioning tank, and valve menas selectively operable to either direct the diluent and concentrate to the mixing and proportioning tank or alternatively direct the resulting mixed solution from the proportioning tank to a storage tank 50. <IMAGE>

Description

SPECIFICATION Pressure and fluid flow activated, simplified propor tioning system This invention relates to a dialysate-proportioning system.

Hemodialysis has become the accepted therapy for "End Stage Renal Disease" (ESRD). Since the Westablishment of federal financing for all U.S. citi mizens, tens of thousands of terminal patients have been given a second chance to live by hospital and kidney center dialysis. Treatments average five hours in duration, and three times a week in fre quency.

U.S. Public Law changed the intent of the ESRD program in 1979 by directing that patients must be given the option of home-dialysis treatment.

Emphasis on home dialysis promises to substan tially reduce reimbursement costs by the federal agencies.

Hemodialysis equipment currently available is in general, large, heavy and not really suited for the home, much less for travel.

The equipment of the present invention can be used with any commercially available dialyzer, whether "coil" or "flat plate" or "capillary". (The dialyzer is a semi-permeable membrane device that, together with other hemodialysis equipment, purifies the blood by osmotic differentials, and removes excess fluid by pressure differentials.) Hemodialysis requires, first of all, a "proportion ing" system which accurately dilutes the dialysate concentrates with water (usually 34:1), and homogeneously mixes the resulting solution. The "dialysate" module then heats and deaerates the solution, and controls the rate of flow to the dialyzer.

Hemodialysis systems employ a built-in conduc tivity meter to ensure accurate dilution of dialysate concentrate between critical limits. Conventional calibration is generally performed by comparing the reading of this instrument with an external instru ment by passing the diluted dialysate concentrate through said external instrument (such as a laborat ory asmometer). Another method is to employ a "check point" or "calibrate circuit" within the built-in conductivity meter, usually a resistor in the elec tronic circuit. These prior art calibration methods fail to afford complete reliability and patient safety because of inherent variables, including significant potential for human error.

This invention describes a novel, simplified com pact system of accurate proportioning which elimi nates the need for complex mechanisms and con trolls (often combinations of precision hydraulic pis ton pumps operated by water pressure), and for sophisticated electronic sensing and feed-back serve circuits, According to the present invention there is pro vided a proportioning system for diluting a concen trate comprising a proportioning tank, a source of concentrate, a source of diluent, means for passing the diluent and the concentrate to the proportioning tank wherein the diluent and concentrate are mixed in a pre-arranged proportion, a storage tank, and valve means operable selectively either to direct diluent and concentrate into the proportioning tank or, alternatively, to direct the resulting solution from the proportioning tank to the storage tank.

The invention also includes a method of diluting a concentrate in accurate proportions and delivering the resultant solution comprising the steps of delivering a diluent to a proportioning tank, delivering concentrate to the proportioning tank in predetermined proportion to the amount of diluent delivered to the proportioning tank, sensing the pressure within the proportioning tank, providing valve means operable selectively, either to direct diluent and concentrate into the proportioning tank or, alternatively, to cause flow of the resulting solution from the proportioning tank, operating the valve means to cause flow from the proportioning tank when the pressure within the proportioning tank reaches a predetermined level, sensing the flow from the proportioning tank, and operating the valve means to direct diluent and concentrate to the proportioning tank when the flow from the proportioning tank reaches a predetermined level.

According to another aspect of the invention a hemodialysis system comprises a proportioning tank, a pressure switch therefor, a source of water, a source of concentrate, a flow switch actuated by the flow from the proportioning tank occasioned by the actuation of the pressure switch, and causing the flow to continue until the tank is substantially empty, a water line proceeding from the source of water to the proportioning tank, a pump in said line for pumping the water to the tank, two three-way valves, one on each side of the pump in the water line, said switches controlling the three-way valves to direct water and concentrate to the tank or to direct the solution out of the tank.

In the preferred arrangement a main pump runs continuously, pumping water from a supply source into a proportioning tank and simultaneously into a concentrate metering pump, thereby propelling the metered concentrate into the mix tank. Alternatively, the main pump delivers proportioned dialysate to the reservoir (storage) tank after each "batch" has been prepared.

As the proportioning tank fills, pressure therein increases until a present level is reached (e.g., 25 psi). A pressure switch then applies electrical power to a pairofdirectional solenoid valves at the input and output of the pump. When energized, these direct the flow of proportioned dialysate from the proportioning tank to the reservoir tank. When they are de-energized, th e flow is directed from the water source into the proportioning tank and concentrate pump.

An air-breathing check valve in the proportioning tank opens on demand to facilitate the emptying cycle.

When the emptying cycle is initiated, a flow switch (located between the proportioning tank and reservoir tank) is actuated, picks up the electrical load from the pressure switch, and continues to supply power to the directional solenoid valves until the proportioning tank empties and flow ceases. The pressure switch automatically resets for another fill cycle.

When the proportioning tank has been emptied and its contents have been delivered under pressure into the storage tank, the directional valves deenergize, returning to their original state, and another proportioning-mixing cycle begins. The frequency of this cycle is determined by the rate of delivery of proportioned dialysate to the kidney, and by the volumes of the proportioning and storage tanks, e.g. a 500 cc/min. output, and 500-cc mix-proportioning tanks, would cycle one a minute.

The system completely eliminates the need for sophisticated electrical control of relay logic and other elements.

The balance of the system encludes: a flow meter and a flow controller.

A conductivity-measuring system.

A temperature-control and heating system.

A three-way, fail-safe, solenoid-actuated directional valve.

Normal mode to drain; emergized mode to patient (when both conductivity and temperature system are "in limits").

An air-removal system.

A "sterilize" (disinfecting) mode in which heater, conductivity system, and three-way valve are deenergized. This system is interlocked with Hansen connectors to prevent unintentional operation in the "sterilize" mode.

Display oftemperature and conductivity, with controls for adjusting both parameters.

For negative pressure dialyzers, a source of negative pressure, a control valve, and a pressureindicating gauge.

The invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 is a diagram flow sheet of a part of the system; and Figure 2 is a diagram and flow sheet of the remainder of the system.

In Figure 1 ofthe drawings reference 10 indicates a water supply under pressure controlled by a conve nientvalve 12 if such a supply is available. The reference 14 represents a water storage apparatus (no pressure) which may be used alternatively with respect to the water under pressure. The sources 10 and 14 may be connected to flow into a pipe 16 selectively by proper valving.

A directional three-way valve 18 receives the water from the pipe 16 passing it through pipe 20 to a gear pump 22. The gear pump 22 leads to a pipe 24 to another three-way valve 26 utilized to direct the waterthrough pipe 28 and branch 30 and thence into the proportioning tank 32. Some of the water from pipe 28 passes through a branch pipe 34 into a concentrate pump 36 which receives the concentrate from a concentrate source 38 through a pipe 40 and it will be seen that the concentrate and the water move together into the proportioning tank 30, becoming mixed.

When the proportioning tank is substantially full, the solution then moves back through pipe 30 and pipe 42 to the three-way valve 18, gear pump 22, three-way valve 26, pipe 44, through flow switch 46 and pipe 48 to a storage tank 50.

The pressure switch 52 operates the thrneway valves in a desired sequence to carry out the operation described above. When the proportioning tank arrives at a certain predetermined high pressure, the pressure switch operates to actuate the three-way valves 18 and 26 so that pipes 28 and 34 are closed, and the proportioning operation ceases. The proportioned dialysate then proceeds through pipes 30,42, etc., as above described, to the storage tank 50, 4 ready for use. When the emptying cycle is initiate#, the flow switch 46 actuates, assumes the electrical load from pressure switch 52, and continues to sEp- ply power to the directional solenoid valves 18 and 26 until the mix tank empties.The switches 46 and 62 automatically reset for another proportioning cycle.

From the storage tank 50, the proportioned dialysate proceeds to a heater 54, a temperature control 56, an air trap 58, a conductivity and temperature manifold 60, and a three-way valve 62 which is automatically operated by the conductivity and temperature monitors to pass the solution effectively through the artificial kidney 68. The effluent from the artificial kidney 68 passes through the blood-leak detector and sampling port 66 and finally to drain 72. Should concentration and/ortempera- ture of proportioned dialysate be out-of-limits, the three-way valve 62 functions as a positive fail-safe by directing the dialysate 70 to drain 72. The pump 64 provides the negative pressure essential for operation of parallel-flow type dialyzers, and also for pumping of effluent to drain from coil-type dialyzers.

With reference to the criticality of proportioning of dialysate concentrate, this invention will directly check and calibrate the built-in conductivity meter with its built-in cell. Means is provided to introduce a standard reference solution into the cell and observe the meter reading as a means of directly calibrating the cell, its electrodes and its temperature compensation, as well as the electronics and the meter.

This invention affords a system which need not rely on external water supply pressure.

The invention can be used with a "pre-mix" dialysate.

The dialysate-proportioning system of this invention can be used as a source of dialysate supply for a multiple-patient hemodialysis unit.

Claims

1. A proportioning system for diluting a concentrate comprising a proportioning tank, a source of concentrate, a source of diluent, means for passing the diluent and the concentrate to the proportioning tank wherein the diluent and concentrate are mixed in a pre-arranged proportion, a storage tank, and valve means operable selectively either to direct , diluent and concentrate into the proportioning tatk or, alternatively, to direct the resulting solution from the proportioning tank to the storage tank.

2. A proportioning system according to Claim 1 wherein the proportioning tank includes a first sensor-operated switch arranged to operate at a pre-determined high pressure to actuate the valve means to direct solution from the proportioning tank to the storage tank.

3. A proportioning system according to Claim 1 or 2 wherein a second sensor-operated switch is provided between the proportioning tank and the storage tank, the second switch being arrange#d to operate at a pre-determined flow to actuate the valve means to direct diluent and concentrate into the proportioning tank.

4. A proportioning system according to Claim 1, 2 or 3 wherein the means for passing the diluent and the concentrate to the proportioning tank comprises a first pump for diluent, and a second pump for concentrate propelled by diluent from the first pump.

5. A proportioning system according to Claim 4 wherein the first pump is continuously operating, either pumping the solution to the storage tank or the diluent and concentrate to the proportioning tank.

6. A proportioning system according to Claim 1 wherein the means for passing the diluent and the concentrate to the proportioning tank is a pump for delivering the diluent and concentrate to the proportioning tank simultaneously.

7. A proportioning system according to Claim 1 wherein a pump passes the diluent to the proportioning tank and also delivers the concentrate to the proportioning tank, and the concentrate is maintained by a concentrate pump maintaining the amount of concentrate in proportion to the amount of diluent pumped into the proportioning tank.

8. A proportioning system according to Claim 1 wherein the diluent supply is not under pressure.

9. A proportioning system according to Claim 1 wherein the diluent supply is under pressure.

10. A proportioning system according to Claim 6 or 7 wherein the pump is a gear pump.

11. A method of diluting a concentrate in accurate proportions and delivering the resultant solution comprising the steps of delivering a diluent to a proportioning tank, delivering concentrate to the proportioning tank in predetermined proportion to the amount of diluent delivered to the proportioning tank, sensing the pressure within the proportioning tank, providing valve means operable selectively, either to direct diluent and concentrate into the proportioning tank or, alternatively, to cause flow of the resulting solution from the proportioning tank, operating the valve means to cause flow from the proportioning tank when the pressure within the proportioning tank reaches a predetermined level, sensing the flow from the proportioning tank, and operating the valve means to direct diluent and concentrate to the proportioning tank when the flow from the proportioning tank reaches a predetermined level.

12. A hemodialysis system comprising a proportioning tank, a pressure switch therefor, a source of water, a source of concentrate, a flow switch actuated by the flow from the proportioning tank occasioned by the actuation of the pressure switch, and causing the flow to continue until the tank is substantially empty, a water line proceeding from the source of water to the proportioning tank, a pump in said line for to the tank, two three-way valves, one on each side of the pump in the water line, said switches controlling the three-way valves to direct water and concentrate to the tank or to direct the solution out of the tank.

13. A hemodialysis system according to Claim 12 including means to supply a single patient.

14. A hemodialysis system according to Claim 12 including means to supply multiple patients.

15. A hemodialysis system according to Claim 12 including a conventional electronic conductivity test system which can be calibrated in place by introducing a "standard" solution into its integral measuring cell.

15. A hemodialysis system according to Claim 12 including negative pressure systems for "plate" or "capillary" dialyzers.