GB2201354A

GB2201354A - Dialysate preparation apparatus

Info

Publication number: GB2201354A
Application number: GB08725435A
Authority: GB
Inventors: David Robert Shouldice
Original assignee: Cobe Laboratories Inc
Current assignee: Terumo BCT Inc
Priority date: 1986-10-30
Filing date: 1987-10-30
Publication date: 1988-09-01
Anticipated expiration: 2007-10-30
Also published as: FR2605894A1; DE3736711C2; GB8725435D0; CA1293127C; JPS63164959A; JPH056466B2; DE3736711A1; GB2201354B; FR2605894B1

Description

1 1 J 1 1 DIALYSATE PREPARATION APPARATUS 2 2' 0 13 5 At The invention

relates to dialysate preparation apparatus for mixing dialysate concentrate with water.

In dialysate preparation apparatus of the type shown in Johnson U. S. Patent No. 4.371.185 (the disclosure of which is hereby incorporated by reference), water is heatedr deaeratedi and mixed with dialysate concentrate to continuously provide dialysate supplied to a dialyzer used with a patient. In such apparatus# dialysate is typically pumped to a junction on a main flow line for mixing with water. A downstream conductivity cell is used to sense the conductivity of the mixed solution passing through it (which conductivity is related to the concentration of elements of the dialysate in the water). and this is used in a control loop to control the-pump for dialysate concentrate. When such apparatus is disinfected and cleaned. between uses wi.th different patients, bleach or disinfectant are flushed through the hydraulic circuitry of the dialysate preparation apparatus.

We have discovered that dialysate preparationapparatus can be provided with an additional level of safety (e.g., against adding the wrong chemical) by, using a volumetric pump having a fixed discharge volume per stroke to pump concentrate to a main flow line ' through which water flows. the volumetric pump being controlled in a feedback loop by a concentrate sensor downstream on the main flow liner and by using a controller that compares the stroke rate of the pump with a range of desired operating stroke rates.

The invention accordingly provides dialysate preparation apparatus for mixing dialysate concentrate with water, said apparatus comprising: a main flow li.ne having one end, arranged for connection to a source of water and another end arranged for operatively providing 1 2 dialysate to a dialyzer; a concentrate flow line having one end arranged for operative connection to a source of dialysate concentrate a nd another end connected to a juncti.on on said main flow I ine for adding concentrate to water in said main flow line; a volumetric pump having a fixed discharge volume per stroke on said concentrat6 line; a concentrate sensor on-said main flow line downstream of said junction adapted for providing control signals to said pump to pump concentrate to achieve the desired-concentration, and a controller including a comparator adapted operatively to compare a stroke rate of said pump with limits indicating desired operating stroke rate range.

In preferred embodiments the concentrate sensor is a conductivity sensor; and the concentrate pump can be connected to either a source of concentrate or a source of cleaning chemical, andthe range of desired operating stroke rates for the concentrate excludes the pump rate of the cleaning chemical necessary to achieve the conductivity set point.

The invention is hereinafter more particularly described by way of example only with reference to the single figure of the accompanying drawing which schematically illustrates a preferred embodiment of dialysate preparation apparatus constructed according to the present invention.

Referrihg'to the drawingj, there is shown dialysate preparation apparatus 10, including main flow line 12 having end 14 for connection to a source of water and another end.connected to inlet 16 of dialyzer 18, having blood inlet 20 and blood outlet 22 connected to a patient and dialysate outlet 24. Concentrate line 26 is connected at one end to junction 28 on main flow line 12 and at the other end has connector 30 for connection to fitting 32 or fitting 34 on dialysate concentrate (acetate) jug 36 or bleach jug 38.

1 3 i 1.

9 On concentrate flow line 26 is volumetric diaphragm pump 40 that has a fixed discharge volume per stroke. Downstream of junction 28 on main flow line 12-are mixing chamber 42 and conductivity cell 44. Pump 40 is controlled by a feedback loop based on the conductivity sensed by sensor 44, which loop is indicated by dashed line 46 to controller 48 and dashed line 47 to pump 40 in the drawing. Controller 48 includes a comparator to compare the stroke rate (stroke/time) of pump 40 (i.e., the rate of pulses provided over line 47 to pump 40) with a limit indicating desired operating stroke rate range.

Apparatus 10 also includes a heat exchanger, a combined heater and deaerator, balance chambers (to balance to flow into the dialyzer with that coming out of the dialyzer to control ultrafiltration) and further conductivity cells and a pH sensor all not shown. It also includes a second concentrate supply line (including a pump and jug connector) and junction, mixing chamber and conductivity cell, all upstream of junction 28, to permit bicarbonate to be added using.this additional supply line and acid to be added by line 26, to permit use with bicarbonate and acid solutions instead of acetate.

In operation water is provided to flow line 12 at end 14, and dialysate concentrate is pumped by pump 40 to junction 28, in which there is initial mixing of water with the concentrate. Further mixing occurs in mixing chamber 42, which has a vent. connected to a vacuum pump (not shown) to remove any gas volatilized from the solution. From mixing - -.tz 4 t chamber 42, the mixed dialysate concentrate/water solution passes through conductivity cell 44, and from there it flows to the dialysate side of the membrane in dialyzer 18. The conductivity sensed by sensor 44 is fed back and used to control pump 40 to achieve a conductivity associated with desired dialysate concentration. The stroke rate of pump 40 is automatically monitored by controller 48, which continuously compares it with a range of desired operating stroke rates for the particular concentrate.

Between use with different patients, the hydraulic circuitry is rinsed with water and flushed with cleaning fluids, some of which may remain in the circuitry for A period of time. "Cleaning flUldC, as used herein means bleach or disinfectant or other chemicals which might be flushed through the system. E.g., bleach in jug 38, shown in the drawing, is flushed through the system using pump 40 after connector 30 has been connected to fitting 34 on jug 38.

The continuous Monitoring of the stroke volume by controller 48 prevents use of an improper chemical that could be proportioned to the conductivity set point and cause patient harm. For example, dialysate concentrate is pumped to mix 1 part of it with 34 parts of water, and the conductivity associated with the mixed solution is used as a-set-point. If the stroke rate of pump 40 is such that it would be pumping 1:20, an alarm is sounded.- _To pump'enough bleach to reach the conductivity set point would require pumping at a stroke rate higher than that associated with 1:20 mixing.

1 1 i 1 1 1 ,- t A further advantage is that loop 46 automatically corrects for changes in concentration of concentrate in jug 36.

i 1 6

Claims

CLAIMS:

1. Dialysate preparation apparatus for mixing dialysate concentrate with waterj, said apparatus comprising: a main flow line _having one end arranged for connection to a source of water and another end arranged for operatively providing dialysate to a dialyzer; a concentrate flow line having one end-arranged for operative connection to a source of dialysate concentrate and another end connected to a junction on said main flow line for-adding concentrate to water in said main flow line; a volumetric pump having a fixed discharge volume per stroke on said concentrate line; a concentrate sensor on said main flow line'downstream of said ju nction adapted for providing control signals to said pump to pump concentrate to achieve the desired concentration; and a controller including a comparator adapted operatively to compare a stroke rateof said pump with limits indicating desired operating stroke rate range.

2. The dialysate preparation apparatus of Claim l# wherein said concentrate sensor is-a conductivity sensor having a Conductivity set point associated with it corresponding to said desired concentration.

3. The dialysate preparation apparatus of Claim 2. wherein said concentrate line includes a mechanism adapted to connect the concentrate line to a source of concentrate or to-a source of cleaning fluid; and wherein said limits indicated desired operating stroke rate range for said concentrate does not include a rate permitting pumping of said cleaning fluid to achieve said conductivity set point.

1 1 7 k

4. Dialysate preparation apparatus for mixing dialysate c6ncentrate with water. said apparatus. being substantially as hereinbefore described with reference to and as shown in the accompanying drawing.

Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WCIR 4TP. Further copies may be obtained from The Patent office, Sales Branch, St Mar7 Cray, Orpinpm, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent Con. 1/87.