FR2547412A1 - Simplified pressurised-fluid dose mixing system, especially for haemodialysis devices - Google Patents

Abstract

The invention relates to a simplified pressurised-fluid mixing system especially for haemodialysis systems. In this system, a first switching means 52 reacting to pressure is combined with a metering tank 32 and actuated when the pressure prevailing in this tank reaches a predetermined level. A second switching means 46, reacting to the flow rate of the fluid, is mounted in a pipe 44, 48 situated just in front of an accumulation (storage) tank 50. Distributors 18, 26 of the three-way type, installed in the pipes between a pump 22, the dosing tank 32 and the accumulation tank 50 are actuated by the said first 52 and second 48 switching means to determine the direction of the flow of a dialysate. Application especially to haemodialysis devices.

Description

 Hemodialysis has emerged as a therapy for end-stage renal disease.

 The hemodialysis equipment currently available is generally bulky, heavy and not really suitable for use at home, even less for transport.

 The present invention relates to equipment of this type which, easily transportable, compact and of low weight, does not in any way sacrifice the reliability or the efficiency proper to devices of the same kind which are more bulky. This team can be used with any commercially available dialyzer, whether the latter is of the "serpentine", "plate" or "capillary" type. The dialyzer is a semi-permeable membrane device which, combined to other hemodialysis devices, purifies the blood by osmotic differentials and removes excess fluid by pressure differences.

 First of all, hemodialysis requires a dosing system which precisely dilutes the dialysate concentrates with water, usually 34: 1, and which homogeneously mixes the resulting solution. Then, the dialysate module heats and degasses the solution, then it controls the flow directed to the dialyzer.

 These hemodialysis systems include a built-in conductivity meter to ensure precise dilution of the dialy5atj concentrate between critical limits.

 Conventional calibration generally takes place by comparing the result displayed by this instrument to that of an external instrument by passing the diluted dialysate concentrate through this external instrument (such as a laboratory osmometer).

Another method is to use a "control point" or "calibrated circuit" inside the conductivity meter, usually incorporating a resistor connected to the electronic circuit. These prior art calibration methods do not offer complete reliability or total patient rity because of inherent variables, including a notable possibility of human error.

 The present invention provides a new, compact and simplified system allowing precise dosing and eliminating the need for complicated control mechanisms and devices (very often combinations of high precision hydraulic piston pumps actuated by pressurized water) , as well as the need to use very sophisticated electronic circuits for detection and retro-actio.

 In the system according to the invention, a main pump continuously operates, pumping water from a supply source to a mixing or metering tank and simultaneously to a pump for measuring the concentrate, thus propelling the concentrate measured in the mixing tank. As a variant, this main pump delivers metered dialysate to the accumulation tank after each "batch" has been prepared.

 When filling the dosing tank, the pressure inside the dosing tank increases until it reaches a predetermined level (for example 1.72 bar). A switch reacts to the pressure then supplies electrical energy to a pair of electromagnetic distributors at the inlet and outlet of the pump.

When supplied, these distributors direct the flow of metered dialysate from the metering tank to the accumulation tank. When the activation of these dispensers ceases, the flow is directed from the water source to the dosing tank and the concentrate pump
A breather-type check valve mounted in the swouvre dosing tank when necessary to facilitate the emptying cycle.

 When the emptying cycle is initiated, a flow switch (interposed between the metering tank and the storage tank) is actuated, it tends to place the pressure control switch to supply the. electric current and it continues to supply the electromagnetic distributors with energy until the metering tank is empty and the circulation of the fluid is interrupted.

The pressure control switch returns automatically to another fill cycle.

When the dosing tank has been emptied and its contents have been introduced under pressure into the accumulation tank, the distributors are de-energized, returning to their initial positions, and another dosing / mixing cycle begins. The frequency of this cycle is determined by the speed at which metered dialysate is delivered to the kidney and by the volumes enclosed by the respective dosing and accumulation reservoirs, for example for an outlet flow rate of 500 cm / min, from the reservoirs of
3 mixing / dosing of 500 cm would each cycle in one minute.

 The system completely eliminates the need for a complicated electrical device for controlling relays and other elements.

The system or apparatus este includes:
- a flow meter and a flow control device
- a system measuring conductivity,
- a temperature and temperature control system
heater;
- an electromagnetic distributor of the three type
tracks operating without any failure [presenting
a normal operating mode, with connection
lie to an evacuation; and a mode of operation
under excitation, with connection to the patient
when the conductivity and
temperature are within ac limits
ceptables);
- an air purge system:
- a "sterilization" procedure ("disinfection"
in which the heating system, the system
conductivity and the three-way distributor
are de-energized. This system cooperates with
Hansen fittings to prevent operation
involuntary in "sterilization"mode;
- a device for displaying the temperature and
conductivity, equipped with control elements
to set these two parameters; and
- for dialyzers operating under vacuum,
a vacuum source, a control valve
and a probe indicating the value of the pressure.

The invention will now be described in more detail with reference to the accompanying drawing by way of non-limiting examples, and in which:
Figure 1 is a block diagram illustrating the flow in a part of the system; and
Figure 2 is a block diagram showing the circulation in the remaining part of this system.

 By way of example, in FIG. 1, the reference 10 designates a source of pressurized water supply controlled by an appropriate valve 12 if such a supply source is available. Reference 14 indicates a water storage device (free of pressure), which can be used as a variant of the pressurized water supply.

These sources 10 and 14 can be selectively connected to a tube 16 by an appropriate valve system.

 A distributor 18 of the three-way type receives water from the tube 16 and directs this water to a gear pump 22 by passing it through a tube 20.

The gear pump 22 is connected by a tube 24 to another distributor 26 of the three-way type used to direct the water, via a tube 28 and a transplanting conduit 30, towards a reservoir of metering 32. Part of the water passes through a transplanting duct 34 to gain a concentrate pump 36 which receives the concentrate from a source 38 of concentrate via a tube 40, and we can see that the concentrate and the water both go in metered flows to the metering tank 32 where they are mixed.

 When the dosing tank is substantially full, the solution returns to an accumulation tank 50 via the tube 30 and the tube 42, passing through the three-way distributor 18, the gear pump 22 and the three-way distributor 26 and passing through a tube 44, a flow regulator controlled by a switch 46 and a tube 48.

 A switch with pressure probe 52 activates the three-way distributors in a desired sequence to carry out the operation described above. When the pressure prevailing in the metering tank reaches a certain predetermined level, this pressure switch comes into operation to actuate the distributors 18 and 26 so as to close the tubs 28 and the transplanting duct 34, which ends the metering process . Then, the metered dialysate borrows the tubes 30, 42, etc. (as described above) to gain the storage tank 50 pr & to operate.

When the emptying cycle is initiated, the dulie switch 46 enters an action, replaces the switch 52 ut continues to supply the electromagnetic distributors 28 and 26 with energy until the metering or mixing tank becomes empty.

The switch 46 and the switch 52 automatically return from zero for another dosing cycle.

 From the accumulation tank 50, the metered dialysate gains a heating element 54, a member 56 for controlling the temperature, a trap 58. for air retention, a detector 60 of conductivity and temperature, as well as a distributor 62 of the three-way type which is actuated automatically by the conductivity and temperature detectors to efficiently pass the solution through an artificial kidney 66. The effluent coming from this artificial kidney 66 passes through a hemoglobin presence detector ( loss of blood) and a connection 66 for taking samples to finally reach a discharge conduit 72. In the case where the concentration and / or the temperature of the dialysate prove to be outside acceptable limits, the distributor 62 acts effectively as a safety device by directing the dialysate via a conduit 70 towards the evacuation conduit 72. A pump 64 generates the vacuum essential for the operation of dialyzers of the parallel flow type, as well as pumping the effluent from coil dialyzers to send the effluent to the outlet.

 Given the important nature of the dosage of the dialysate concentrate, the present invention directly controls and calibrates the incorporated conductivity meter and its incorporated cell. Means are provided for introducing into this cell a standard reference solution and for observing the values displayed by the measurer as a means for directly calibrating said cell.

its electrodes and its temperature compensation, as well as the electronic components and the meter.

 This invention provides a system that does not need to be equipped with an external source of pressurized water.

 The invention can be used with a premixed dialysate.

 The dialysate dosing system according to the present invention can be used as a dialysate supply source in a hemodialysis machine treating multiple patients.

 It goes without saying that many modifications can be made to the system described and shown, without departing from the scope of the invention.

Claims (10)

 1. Dosing system comprising a dosing and mixing tank (32), an accumulation tank [50), a source t38) of concentrate, a source [14; 16) of diluent, a pumping means E22 36) operating continuously and tubes (16, 20, 24, 28, 34; 30, 42, 20, 24, 44, 48) for directing the diluent from said source (14 ; 16) to said metering tank (32) and from this metering tank (32) to said accumulation tank (50), the pumping means (36) discharging, via a conduit (40) of the concentrate from said source (38) in said metering tank (32) with a predetermined proportion of concentrate and diluent, system characterized in that a first switching means (52), actuated by a pressure-activated detector, is associated with said metering tank (32) to be actuated when the pressure prevailing in said metering tank reaches a certain predetermined level when this metering tank is filled, a second switching means [463 controlled by a detector activated by the flow of the fluid being installed in the conduit (44, 48) located just before the accumulation tank (50 ) in order to be activated when the fluid flow reaches a predetermined value; and by the fact that distributors [1d, 26) are mounted in the tubes between said pumping means (22), said metering tank t32) and said accumulation tank (50), these distributors (16, 26) being first actuated by said first switching means (52) responsive to pressure so as to direct the fluid from said metering tank (32) to said accumulation tank (50) when said pumping means (22) continues to operate, while these distributors t18, 26) isolate said metering tank (32) from the concentrate and diluent, said second switching means (46) reacting to the flow of the fluid being actuated to maintain said distributors (18, 263 in this position as long as the flow rate continues, and this second switching means (46) reacting to the flow rate of the fluid entering into action to return said distributors (16, 26) to their initial positions so as to once again direct the diluent and the concentrate worm s the dosing tank (32).  2. Dosing system according to claim 1, characterized in that the distributors (18, 26) are of the three-way type.  3. Metering system according to claim 1, comprising transplanting conduits and characterized in that the pumping means (22) delivering the diluent to the metering tank (32) via said transplanting conduits (34, 30 ) also simultaneously delivers the concentrate to this metering tank (32).  4. Metering system according to claim 1, comprising transplanting conduits and characterized in that the pumping means (22) delivering the diluent to the metering tank t32) via said transplanting conduits (34, 30) also delivers the concentrate to this metering tank (32), and by the fact that a means (36) for pumping the concentrate keeps the amount of concentrate proportional to the amount of diluent discharged into said metering tank [32).  5. Metering system according to claim 1, characterized in that it comprises a means (14) for supplying non-pressurized diluent.  6. Dosing system according to claim 1, characterized in that it comprises a means [12) for supplying pressurized diluent.  7. Metering system according to claim 1, characterized in that the pumping means is a gear pump (22).  8. Dosing system according to claim 1, characterized in that it comprises means for treating a single patient.  9. Dosing system according to claim 1, characterized in that it comprises means for treating several patients.  10. Dosing system according to claim 1, characterized in that it comprises a means or pump (64) making it possible to generate a vacuum in dialyzers of the plate or capillary type.