PUMP CALIBRATION DURING BAG FILLING

Abstract

In medical apparatus, for example a dialysis machine, a pump is used to move fluid such as purified water or dialysate. The pump performance is monitored by determining the weight or mass of the fluid being pumped. A less expensive pump may be used whilst maintaining an accurate determination of the volume pumped.

Claims

1. Apparatus for pumping a fluid comprising a reservoir for, in use, holding a supply of the fluid, a pump coupled to the reservoir to receive fluid therefrom or to pump fluid thereto, a sensor for determining a variation in an amount of the fluid held in the reservoir and a controller to determine from the variation an amount of fluid pumped by the pump.

2. Apparatus as claimed in claim 1 wherein the amount is one of volume or weight.

3. Apparatus as claimed in claim 1 further comprising a sensor to provide an output representative of the number of pump cycles performed and to provide the output to the controller which controller being configured to determine therefrom, and the determined amount, a value of the amount of fluid pumped per cycle.

4. Apparatus as claimed in claim 2 comprising a memory for storing the determined value of the amount of fluid pumped per cycle of the pump.

5. Apparatus as claimed in claim 4 wherein the stored determined value of the volume of fluid pumped per cycle is used by the controller to determine subsequent amounts of fluid pumped by the pump using a count of the cycles performed.

6. Apparatus as claimed in claim 5 wherein the controller compares a past determined value of the amount of the fluid pumped per cycle with a more recent determined value of the amount of the fluid pumped per cycle and in the event that the comparison exceeds a threshold performing a recalibration of the pump to determine a current amount of fluid pumped per cycle of the pump and or indicating a pump fault.

7. A dialysis machine comprising apparatus for pumping a fluid as claimed in claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0017] A specific embodiment of the invention will now be described with reference to the figures in which:

[0018] FIG. 1 shows in schematic form a dialysis machine in accordance with an embodiment of the invention in which a preparator module of the machine is located in a patient's bathroom and a cycler module of the machine is located in the patient's bedroom; and

[0019] FIG. 2 shows a pumping apparatus in accordance with the invention used in the dialysis machine of FIG. 1.

DETAILED DESCRIPTION

[0020] Unless defined otherwise, all technical and scientific terms used generally have the same meaning as commonly understood by one of ordinary skill in the art.

[0021] The articles “a” and “an” are used to refer to one or to over one (i.e., to at least one) of the grammatical object of the article. For example, “an element” means one element or over one element.

[0022] The term “comprising” includes, but is not limited to, whatever follows the word “comprising.” Use of the term indicates the listed elements are required or mandatory but that other elements are optional and may be present.

[0023] The term “consisting of” includes and is limited to whatever follows the phrase “consisting of.” The phrase indicates the limited elements are required or mandatory and that no other elements may be present.

[0024] The term “consisting essentially of” includes whatever follows the term “consisting essentially of” and additional elements, structures, acts or features that do not affect the basic operation of the apparatus, structure or method described.

[0025] The term “dialysate” describes a fluid into or out of which solutes from a fluid to be dialyzed diffuse through a membrane. An initial dialysate used for therapy typically contains electrolytes close in concentration to the physiological concentration of electrolytes found in blood. However, the concentration of the dialysate can change over the course of therapy, and can further be adjusted as desired.

[0026] The term “dialysis flow path” refers to a fluid pathway or passageway configured to convey a fluid, such as dialysate and/or blood, wherein said pathway forms at least part of, preferably the whole of, a fluid circuit for peritoneal dialysis, haemodialysis, hemofiltration, hemodiafiltration or ultrafiltration. A dialysis machine may be included within the flow path. A dialyzer may be included in the flow path.

[0027] The term “mix” means to combine one or more substance so that the resulting mixture is not easily separated. Mixing, especially evenly spreading, of solute and solvent aids and speeds the process of dissolution. Mixing can be achieved by any method, including spraying, stirring, shaking, or otherwise agitating. The term “improved mixing” refers to a situation wherein the components of a mixture are more evenly distributed and not clumped together. Improved mixing may be achieved, for example, by speeding the mixing up. In the context of a solution, improved mixing results in a solution of the correct concentration because all or most of the solutes dissolve, rather than remaining as clumps or aggregated within the solvent.

[0028] The present invention relates to an improved automated peritoneal dialysis machine that includes a preparator and cycler for in situ preparation of peritoneal dialysis fluid (PDF) for delivery and drainage from a patient with communications links established therebetween.

[0029] FIG. 1 shows an example of a peritoneal dialysis machine 1 according to the present invention. The peritoneal dialysis machine 1 is set up in the patient's home which is represented by two rooms, a bathroom 2 and an adjoining bedroom 3 (although these rooms are representative only and the locations could be other rooms). The peritoneal dialysis machine 1 includes a preparator 4, an automatic cycler 5, a flexible dialysate supply tube 6 and an electrical power supply line 7.

[0030] The preparator 4 is positioned in bathroom 2 as it requires a water source to enable the preparator 4 to generate peritoneal dialysis fluid. The water source may comprise, for example, a tap (faucet) or a more permanent outlet. The preparator 4 first filters the input water and mixes it with a quantity of powered dialysate in accordance with a preprogramed formulation. The powered dialysate will include dextrose, magnesium and calcium and lactate bicarbonate and sodium chloride.

[0031] The automatic cycler 5 is positioned in the bedroom 3 where the patient “P” intends to undergo peritoneal dialysis. The cycler 5 is connected to a dialysate delivery tube 8 which is connected to a catheter (not shown) which is inserted into the peritoneum of the patient. The cycler 5 controls the flow of the dialysate into, and out of, the patient in accordance with the required dialysis procedure. Dialysate removed from the patient is stored in a container in the cycler 5 (not shown) for subsequent disposal. This procedure is predetermined and held in memory within the cycler 5 operated under processor control. Broadly, the machine operates by preparing dialysate at the preparator 4, the prepared dialysate is pumped via the dialysate supply tube 6 to the cycler 5. There it is heated to patient temperature and administered to the patent via the delivery tube 8 and the catheter into the patient. After, the appropriate time-period for dialysis, the dialysate is removed from the patient via catheter and the delivery tube 8 and held in storage for subsequent removal and disposal.

[0032] As will be appreciated, although the two modules are not collocated, it is necessary for instructions and data to pass between the modules. For example, the preparator 4 will need to provide status updates to the cycler 5 indicating that the dialysate is mixed and available for delivery. The cycler 5 will need to instruct the preparator 4 to commence with delivery, or to increase, or reduce the rate of delivery. Error states may need to be passed. For example, the preparator 4 may experience a problem with the water supply pressure and that will need to be communicated to the cycler and indicated as a fault condition on a display. Accordingly, the preparator 4 and the cycler 5 are each provided with a suitably programmed processor to control its respective functions. In addition, a master processor or controller is provided or designated to control the function of the machine as a whole. These processors (or one processor programmed to provide a number of processing functions) provide in addition a communication function to allow the modules to interoperate and to be controlled.

[0033] In this embodiment of the invention, there are two communications links which are operable to enable communications between the modules. A first communications link 10 using radio and operating in accordance with a Wi Fi communications protocol and a physical communications link 11 provided by cable 7 over which a Powerlink communications protocol is used.

[0034] In order to move the dialysate from the preparator 4 to the cycler 5 and to and from the patient, a pump (or pumps are required). In this case the pump is located at the preparator 4 but it could be located at the cycler or indeed two or more pumps could be provided located at each module.

[0035] FIG. 2 shows a pump apparatus 20 within the preparator 4. It includes a purifier 21 which accepts water via valve 22 from a domestic water supply. The purifier 21 includes filters and a uv light source to purify the mains water and to remove metals or other contaminants. The purifier has an outlet which is coupled to a reservoir 23 where the purified water is stored.

[0036] The reservoir is a plastics material container and rests on a piezo electric sensor 24. It has an outlet coupled to a pump 25.

[0037] The pump 25 is has an outlet which is coupled to a mixing section 26 and is optically connected to a revolution counting sensor 27. The counting sensor 27 counts the number of pump revolutions and provides the count to a processor 28.

[0038] The mixing section 26 accepts dialysate concentrate from a bag 29 and mixes it with the purified water received from the pump 25. The resultant peritoneal dialysis fluid is then output from the preparator 4 to the cycler 5 via the fluid supply line 6.

[0039] The processor 28 is a controller controls the functions of the preparator 4 and, in particular, monitors the performance of the pump 25 to determine that the correct amount of fluid is delivered in the following manner. The processor/controller 28 is a microprocessor operating in accordance with a programme and data held in memory 30.

[0040] The sensor 24 provides a signal representative of the weight of the water held in the reservoir 23. This signal is provided to a weight processor 31 which determines the weight and passes this figure to processor 28. The processor 28 determines from the weight at the start of a pumping cycle. At the end of the pumping cycle, the processor determines the current weight of water remaining in the reservoir and determines the difference between that and the initial weight to give a value of the weight of the water delivered to the mixing section. From the weight (mass), the volume of the water may be determined from a predetermine value of water density form the relationship Volume=Mass/density.

[0041] The pump 25 is a rotary pump and the count sensor 27 provides to the processor 28 a value for the number of revolutions of the pump made during the pumping cycle. The volume of the pump stroke, that is to say, the volume of one revolution of the pump, may then be calculated. In essence this will provide a calibration point for the pump. The pump stroke may be used for future calculations of the fluid volume delivered which avoid the necessity to measure the volume using the weight of the water delivered. It may also be recorded over time in a periodic manner, and if it drifts, used as an indication that the pump may need replacement or servicing.

[0042] In alternative embodiments, the pump 20 may be located in the cycler with the reservoir holding the PDF and the pumping of that being monitored just prior to delivery to the patient's peritoneum. More than one pump may be provided in each module in alternative embodiments. The pump may be sued to delivery fluid to a reservoir rather than from it and the increase in weight noted to determine the volume of water pumped.

[0043] One skilled in the art will understand that various combinations and/or modifications and variations can be made in the described apparatus, methods and uses depending upon the specific needs for operation. Moreover, features illustrated or described as being part of an aspect of the invention may be used in the aspect of the invention, either alone or in combination.