USRE49881E1

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Publication number: USRE49881E1
Application number: US17/345,665
Authority: US
Inventors: Clive Henry BUCKBERRY
Original assignee: Quanta Fluid Solutions Ltd
Current assignee: Quanta Dialysis Technologies Ltd
Priority date: 2013-03-28
Filing date: 2014-03-27
Publication date: 2024-03-26
Also published as: ES2867377T3; US10314962B2; WO2014155120A1; US20160051743A1; EP2978467B1; GB201305755D0; EP2978467A1

Abstract

The present invention provides a hemodialysis machine comprising a removably mountable cartridge having at least one inlet and at least one outlet, the cartridge defining a fluid pathway between said at least one inlet and said at least one outlet, a sanitisation device having an inlet and an outlet, a conduit connected between an outlet of the cartridge and the inlet of the sanitisation device and, a conduit connected between the outlet of the sanitisation device and an inlet of the cartridge.

Description

The present application is a reissue patent application of U.S. Pat. No. 10,314,962, which issued 11 Jun. 2019, from U.S. patent application Ser. No. 14/779,175, filed 22 Sep. 2015, which is a 35 USC § 371 submission of international application no. PCT/GB2014/050978, filed on 27 Mar. 2014 and published in the English language on 2 Oct. 2014 with publication no. WO 2014/155120 A1, which claims the benefit of the filing date of application no. GB 1305755.9, filed 28 Mar. 2013.

The present invention relates to dialysis machines and in particular, but not exclusively to a disposable cartridge for use in hemodialysis machines.

Dialysis is a treatment which replaces the renal function of removing excess fluid and waste products, such as potassium and urea, from blood. The treatment is either employed when renal function has deteriorated to an extent that uremic syndrome becomes a threat to the body's physiology (acute renal failure) or, when a longstanding renal condition impairs the performance of the kidneys (chronic renal failure).

There are two major types of dialysis, namely hemodialysis and peritoneal dialysis.

In peritoneal dialysis treatment, a dialysate solution is run through a tube into the peritoneal cavity. The fluid is left in the cavity for a period of time in order to absorb the waste products, and is subsequently removed through the tube for disposal.

It is common for patients in the early stages of treatment for a longstanding renal condition to be treated by peritoneal dialysis before progressing to hemodialysis at a later stage.

In hemodialysis, the patient's blood is removed from the body by an arterial line and treated by a dialysis machine before being returned to the patient's body by a venous line. The machine passes the blood through a dialyser containing tubes formed from a semi-permeable membrane. On the exterior of the semi-permeable membrane is a dialysate solution. The semi-permeable membrane filters the waste products and excess fluid from the blood into the dialysate solution. The membrane allows the waste and a controlled volume of fluid to permeate into the dialysate solution whilst preventing the loss of larger more desirable molecules, like blood cells and certain proteins and polypeptides.

The action of dialysis across the membrane is achieved primarily by diffusion (the migration of molecules by random motion from a region of higher concentration to a region of lower concentration).

Fluid removal (otherwise known as ultrafiltration) is achieved by altering the hydrostatic pressure of the dialysate solution side of the membrane, causing free water to move across the membrane along the pressure gradient.

The correction of uremic acidosis of the blood is achieved by use of a bicarbonate buffer. The bicarbonate buffer also allows the correction of the blood bicarbonate level.

The dialysate solution consists of a sterilized solution of mineral ions. These ions are contained within an acid buffer which is mixed with the sterilised water and bicarbonate base prior to delivery to the dialyser.

Hemodialysis machines need to be sanitised between uses and maintained in a sanitised condition. Conventionally, known hemodialysis machines are sanitised either through heat cleaning or chemical cleaning to remove trace elements of dialysate solution from within fluid pathways defined by the hemodialysis machine. Dialysate solution comprises sodium bicarbonate as a constituent part which, if left in the hemodialysis machine, provides a natural food source for biofilm. Growth of biofilm in the fluid pathways defined by the hemodialysis machine can lead to unacceptable bio-incompatibility and errors in the hemodialysis process.

Conventional hemodialysis machines use peristaltic pumps, or similar, to flush a cleaning liquid through the hemodialysis machine in a single direction. Such machines risk contamination and growth of biofilm in areas of the machine where the cleaning liquid cannot access.

The present invention seeks to provide an improved hemodialysis machine.

A first aspect of the invention provides a hemodialysis machine comprising a removably mountable cartridge having a first inlet and a first outlet, the cartridge defining a fluid pathway therebetween, a sanitisation device having an inlet and an outlet, a conduit connected between the first outlet of the cartridge and the inlet of the sanitisation device, and, a conduit connected between the outlet of the sanitisation device and the first inlet of the cartridge.

Advantageously, provision of a sanitisation device permits the cartridge to be sanitised and re-used rather than being disposed of after each dialysis sitting.

Preferably, the cartridge further comprises a first mixing chamber, a second mixing chamber connected to the first mixing chamber, a first flow balance chamber connected to the second mixing chamber, a second flow balance chamber connected to the first flow balance chamber, wherein the sanitisation device is removably connected external to the cartridge between the first mixing chamber and the first flow balance chamber.

In one embodiment the cartridge further comprises a first inlet, a conduit between the first inlet of the cartridge and the first mixing chamber, a second inlet, a conduit between the second inlet of the cartridge and the first mixing chamber, a third inlet, a conduit between the third inlet of the cartridge and the second mixing chamber, a fourth inlet, a conduit between the fourth inlet of the cartridge and the second flow balance chamber, a first outlet, a conduit between the first inlet and the first outlet, a second outlet, a conduit between the first flow balance chamber and the second outlet, a third outlet, and, a conduit between the second flow balance chamber and the third outlet.

In one embodiment the sanitisation device comprises a chemical cleaning receptacle.

Preferably, the cleaning receptacle of one embodiment of the invention contains an acid concentrate.

In one embodiment, the chemical cleaning receptacle comprises a chemical bath.

In another embodiment, the chemical cleaning receptacle comprises a common manifold.

A second aspect of the invention provides a method of cleaning a cartridge for re-use in a hemodialysis machine comprising:

a) Providing a cartridge having at least one inlet and at least one outlet;
b) Connecting a sanitisation device between said at least one inlet and said at least one outlet of the cartridge external to the cartridge;
c) Flowing a liquid through the cartridge and the sanitisation device in a first direction;
d) Flowing the liquid through the cartridge and the sanitisation device in a second direction;
e) Flushing the liquid out of the cartridge through the at least one outlet.

Advantageously, directing a liquid through the cartridge in first and second directions is more efficient at sanitising the cartridge than directing the liquid through the cartridge in only one direction.

Preferably, the at least one inlet of the cartridge is a spent dialysate inlet and the at least one outlet is a drain port. In one embodiment, the cartridge further comprises a clean dialysate outlet, a water inlet, a water outlet, a bicarbonate inlet and an acid inlet.

In one embodiment, the method further comprises:

f) Connecting the spent dialysate solution inlet to the clean dialysate solution outlet;
g) Connecting the water outlet to the bicarbonate inlet;
h) Disconnecting the drain port;
i) Connecting the water inlet to a purified water supply;
j) Flushing purified water through the cartridge and out of the drain port and the acid inlet;
k) Connecting the drain port to the acid inlet;
l) Connecting the sanitisation device between the spent dialysate solution inlet and the clean dialysate outlet;
m) Measuring the conductivity of the liquid in the cartridge when flowing in a first direction to ensure that it indicates acid;
n) Disconnecting the sanitisation device and re-connecting the spent dialysate solution inlet to the clean dialysate solution outlet;
o) Flushing purified water through the cartridge and out of the drain port and the acid inlet;
p) Measuring the conductivity of the liquid in the cartridge to ensure that it indicates purified water;
q) Disconnecting all cartridge ports; and,
r) Connecting thecartridge30 to the hemodialysis machine.

In another embodiment, the method further comprises:

f) Connecting the spent dialysate solution inlet, clean dialysate solution outlet, bicarbonate inlet, acid inlet and water outlet to a sanitisation device;
g) Connecting the water inlet to a purified water supply;
h) Connecting the drain port to a drain;
i) Flushing purified water through the cartridge and out of the drain port;
j) Measuring the conductivity of the liquid in the cartridge to ensure that it indicates acid;
k) Flushing purified water through the cartridge and out of the drain port;
l) Measuring the conductivity of the liquid in the cartridge to ensure that it indicates purified water;
m) Disconnecting all cartridge ports; and,
n) Connecting the cartridge to the hemodialysis machine.

In one embodiment, the method further comprises:

(f) Connecting a dialyser between the at least one inlet and the at least one outlet
(g) Connecting the dialyser to a blood pump

Preferably, the at least one outlet is a dialysate solution outlet and the at least one outlet is a dialysate solution inlet.

Advantageously, the cleaning liquid as it flows through the cartridge, in a first direction and in a second direction, also flows through the dialyser and the blood pump to permit re-use of said dialyser and blood pump. The dialyser comprises a semi-permeable membrane which separates a dialysate solution circuit, defined by the cartridge, from a blood circuit, defined by the blood pump. The cleaning liquid permeates through the semi-permeable membrane from the dialysate solution circuit into the blood circuit and is flushed through the cartridge, the dialyser and the blood pump in first and second directions.

In one embodiment, the cartridge comprises at least two inlets and at least two outlets.

In one embodiment, the sanitisation device is connected between one of said at least inlets and one of said at least one outlets and the dialyser is connected between another of said at least one inlets and said at least one outlets.

An embodiment of the invention will now be described, by way of example only, with reference to the following figures.

FIG.1 shows a schematic of a dialysis system having a disposable cartridge comprising a fluid path defined by pumps and valves.

FIG.1a shows a detailed schematic view of the cartridge ofFIG.1.

FIG.2 shows a schematic view of the operation of a pump of the type defined by the disposable cartridge.

FIGS.3a to3d show schematic views of a first method of sanitising the disposable cartridge of an embodiment of the invention.

FIG.4 shows a schematic view of a second method of sanitising the disposable cartridge of an embodiment of the invention.

FIG.5 shows a schematic view of a third method of sanitising the disposable cartridge of an embodiment of the invention.

Referring toFIGS.1 and1a, a dialysis system, generally referred to as10, is shown. Adialyser12 receives blood via anarterial line14 connected to a patient by a vascular access device (not shown for clarity), for example a hollow needle as typically used for drawing blood from a patient. The blood is pumped from the patient to the dialyser by aperistaltic pump16. The blood passes through the dialyser in a known manner and is returned to the patient via avenous line18. Thedialyser12 comprises a cylindrical tube closed by opposing ends. A semi-permeable membrane (not shown) is provided within the dialyser tube and separates the patients blood from a dialysate solution. The membrane extends substantially between the opposing ends of the cylinder. The dialysate solution removes impurities from the patients blood in a known manner.

The dialyser has aninlet20 for receiving clean dialysate solution and anoutlet22 for removing spent dialysate solution from thedialyser12. The dialyser also has aninlet24 for receiving untreated blood from theperistaltic pump16 and anoutlet26 for returning processed blood to the patient. Thedialyser12 is typically provided in a substantially upright orientation, in use, with the patients blood flowing longitudinally through thedialyser12 from theblood inlet24 to theblood outlet26. Thedialysate solution inlet20 anddialysate solution outlet22 are configured to be orientated substantially orthogonal to theblood inlet24 andblood outlet26, and to provide a counter-flow. Dialysate solution is circulated through the hemodialysis machine at a fluid flow rate in the region of 400 ml/min for approximately four hours.

The dialysis system defines a fluid circuit including acartridge30 as will now be described. Thecartridge30 is a consumable component in the hemodialysis machine described.

Thecartridge30 is formed from an acrylic plastic such as SG-10 and has a machine side and a patient side. Thecartridge30 defines pump chambers which are closed by respective diaphragms, formed from, for example, DEHP-free PVC, to define respective pumps. In this embodiment, each diaphragm is part of a single, common sheet of material applied to the machine side of thecartridge30. The individual diaphragms are operable by pneumatic pressure applied thereto.

A series of flow paths are formed in thecartridge30 for carrying dialysate solution constituted from water, bicarbonate solution and acid solution. The flow paths are located between the sheet of material closing the machine side of thecartridge30 and a further sheet of the same material closing the patient side of thecartridge30.

In use, the variation of pressure applied to the flexible diaphragm of each pump chamber is controlled by conventional valving. A pressure source applies either a positive or negative pressure to one side of the diaphragm of each pump chamber, as required, to pump fluid through the fluid paths in thecartridge30, in a circuit defined by a plurality of valves.

The valves of thecartridge30 are conventional diaphragm valves defined by respective openings in thecartridge30 and closed by respective flexible diaphragms. Each valve is operable by applying a negative pressure to the diaphragm to open the valve and applying a positive pressure to the diaphragm to close the valve. The diaphragm of each valve is part of the single, common sheet of material applied to the machine side of thecartridge30. The valves are opened and closed according to a flow control strategy, as will become apparent.

The machine side of thecartridge30 abuts a pump driver (not shown) comprising a platen having a plurality of recessed surfaces, each recessed surface substantially corresponding in geometry and volume to a pump chamber defined in thecartridge30. Each recessed surface has a fluid port connectable with a source of positive fluid pressure and, with a source of negative fluid pressure via a valve.

The positive and negative fluid pressure sources include a pressure pump and a vacuum pump respectively. When the valve is operated to allow fluid to flow into a recessed surface from the source of positive fluid pressure, the diaphragm moves into a corresponding pump chamber and any fluid, i.e. dialysate solution, therein is expelled from that pump chamber via the series of flow paths. When the valve is operated to allow fluid to flow out of a recessed surface to the source of negative fluid pressure, the diaphragm is moved away from a pump chamber and into the corresponding recessed surface to permit fluid to be drawn into that pump chamber via the series of flow paths. The surface of the pump chambers and of the platen provide a positive stop for each diaphragm, to prevent overstretching thereof. The positive stop ensures that the volume of fluid drawn into and pumped from the pump chambers is accurately controlled.

Thecartridge30 has two main functions, preparation of dialysate solution and flow balance. Each function is performed by a separate part of the cartridge as illustrated inFIGS.1 and2 by the schematic separation of the cartridge into two parts by the line A-A in the figures. The dialysate preparation function is performed by one part of the cartridge, generally referred to at34 and the flow balance function is performed by the other part of the cartridge, generally referred to at36. Thecartridge30 prepares an accurately mixed homogenous dialysate solution and ensures that the flow of clean dialysate supplied to thedialyser12 matches (to within clinical tolerances) the volume of spent dialysate drawn from thedialyser12.

Thecartridge30 is provided with a plurality of connections to and from thecartridge30 as described below.

Afirst inlet port38, from hereon referred to as the water inlet port, defined in the machine side of thecartridge30 receives purified water from apurified water supply31 such as a reverse osmosis water supply.

Afirst outlet port42, from hereon referred to as the water outlet port, defined in an edge of thecartridge30 directs the purified water to a first dialysate solution constituent which, in the illustrated embodiment shown inFIGS.1 and1a, isbicarbonate46.

Asecond inlet port50, from hereon referred to as the bicarbonate inlet port, defined in the same edge of thecartridge30 as thewater outlet port42 receives purified water mixed with thebicarbonate46.

Athird inlet port82, from hereon referred to as the acid inlet port, defined in the opposite edge of thecartridge30 to thewater outlet port42 andbicarbonate inlet port50 receives a second dialysate solution constituent which, in the illustrated embodiment shown inFIGS.1 and1a, isacid80.

Asecond outlet port104, from hereon referred to as the clean dialysate solution outlet port, is defined in the same edge of the cartridge as thewater outlet port42 and thebicarbonate inlet port50. The cleandialysate outlet port104 directs clean dialysate solution to thedialyser12.

Afourth inlet port106, from hereon referred to as the spent dialysate solution inlet port, is defined in the same edge of thecartridge30 as thewater outlet port42,bicarbonate inlet port50 and cleandialysate outlet port104. The spent dialysatesolution inlet port106 receives spent dialysate solution from thedialyser12.

Athird outlet port122, from hereon referred to as the drain port, is defined in the same edge of the cartridge as theacid inlet port82. Thedrain port122 directs spent dialysate solution out of thecartridge30.

Dialysate Preparation

Dialysate solution is prepared in thecartridge30 by combining purified water with two dialysate constituents, namely a bicarbonate solution and an acid solution.

Purified water is admitted into thecartridge30 from apurified water supply31 via thewater inlet port38. The purified water passes through achannel40 via awater inlet valve41, when open, and exits thecartridge30 at thewater outlet port42. From here, the purified water is carried by atube44 through abicarbonate cartridge46 in a known manner to generate a purified water and bicarbonate solution. The purified water and bicarbonate solution is carried by atube48 and re-admitted into thecartridge30 via thebicarbonate inlet port50.

The temperature of the bicarbonate solution is measured at sensingport52 and the bicarbonate solution pressure is measured at sensingport54. The bicarbonate solution passes abicarbonate control valve56, when open, before entering abicarbonate solution reservoir58 having an inlet and an outlet. Thebicarbonate control valve56 is closed when flow therethrough is not required.

A bicarbonatedosing pump chamber60 having an inlet and an outlet receives the bicarbonate solution from thebicarbonate solution reservoir58 through a bicarbonate dosingpump inlet valve62. The bicarbonatedosing pump chamber60 is closed by a diaphragm to define a bicarbonate dosing pump which, upon actuation of the diaphragm, pumps the bicarbonate solution from thebicarbonate dosing pump60 to a first mixing pump chamber66 (bicarbonate pump chamber). Thebicarbonate dosing pump60 has a bicarbonate dosingpump outlet valve64 which is closed when the bicarbonate dosingpump inlet valve62 is open. The bicarbonate dosingpump outlet valve64 is opened to permit bicarbonate solution to be pumped to thebicarbonate pump chamber66. When the bicarbonate dosingpump outlet valve64 is open, the bicarbonate dosingpump inlet valve62 is closed to prevent bicarbonate solution from being pumped back into thebicarbonate solution reservoir58.

Thebicarbonate pump chamber66 having an inlet and an outlet receives the purified water and bicarbonate solution from thebicarbonate dosing pump60 via a bicarbonatepump inlet valve68. The bicarbonatepump inlet valve68, when open, can also admit purified water into thebicarbonate pump chamber66 from thewater inlet port38. Thebicarbonate pump chamber66 is closed by a diaphragm to define a pump which, upon actuation of the diaphragm, pumps the bicarbonate solution and purified water therein through a bicarbonatepump outlet valve70 to a second mixing pump chamber76 (acid pump).

When the bicarbonatepump inlet valve68 is open, the bicarbonatepump outlet valve70 andwater outlet valve41 are closed. When the bicarbonatepump outlet valve70 is open, the bicarbonatepump inlet valve68 is closed to prevent the bicarbonate and purified water solution from being pumped back intochannel40.

From the bicarbonatepump outlet valve70, the bicarbonate and purified water solution enters a sensor channel72 in which the hemodialysis machine measures the conductivity of the bicarbonate and purified water solution in a known manner. The bicarbonate and purified water solution then enters atemperature sensor74 before, if the conductivity and temperature of the bicarbonate and purified water solution are within tolerance, entering theacid pump chamber76.

Theacid pump chamber76 having an inlet and an outlet receives the bicarbonate and purified water solution from thebicarbonate pump66 via an acidpump inlet valve78. The acidpump inlet valve78, when open, can also admit an acid solution into thepump chamber76. Theacid pump chamber76 is closed by a diaphragm to define a pump which, upon actuation of the diaphragm, pumps the acid solution, bicarbonate solution and purified water therein through an acidpump outlet valve88 to the first flowbalance pump chamber100. When the acidpump inlet valve78 is open, the acidpump outlet valve88 is closed. When the acidpump outlet valve88 is open, the acidpump inlet valve78 is closed.

The acid solution is admitted into thecartridge30 from a pre-determined supply ofacid80 via the acidsolution inlet port82. From the acid solution inlet port the acid solution passes through an aciddosing pump chamber86 via an acid dosingpump inlet valve84 and an acid dosingpump outlet valve87. The acid dosingpump outlet valve87 is closed when the acid dosingpump inlet valve84 is open. The acid dosingpump inlet valve84 is closed when the acid dosingpump outlet valve87 is open.

The dialysate solution exits the acid pump chamber via the acidpump outlet valve88 and passes through a first dialysate solution temperature sensor90 and a first dialysatesolution conductivity sensor92. A second dialysatesolution temperature sensor94 and a second dialysatesolution conductivity sensor96 are provided to corroborate the data provided by the first dialysate solution temperature sensor90 and the first dialysatesolution conductivity sensor92. Providing the data measured by

sensors

90,92,94 and96 is within tolerance, the dialysate solution is admitted into a first flowbalance pump chamber100

Flow Balance

The flow balance function of thecartridge30 provides first and second flow

balance pump chambers

100,108, each having two inlets and two outlets to define two independent flow paths therethrough. The first and second flow

balance pump chambers

100,108 are of approximately equal volume. Either the first or second flow

balance pump chamber

100,108 pumps dialysate solution to adialyser12 and the other of the first or second flow

balance pump chambers

100,108 pumps dialysate solution from thedialyser12 to thedrain port122. After every approximately 20 strokes of the first and second flow balance pumps100,108, their function is reversed.

From this point onwards, dialysate solution will be referred to as either clean dialysate solution or spent dialysate solution. Clean dialysate solution is intended to mean dialysate solution that is either new dialysate solution or clean dialysate solution that has been treated to remove waste product therefrom. Spent dialysate solution is intended to mean dialysate solution that has passed through thedialyser12 to remove waste fluids from a patients blood into the dialysate solution.

Each of the first and second flow

balance pump chambers

100,108 are closed by a diaphragm to define respective pumps. The diaphragm is actuated away from a pump chamber by a negative pressure source to draw a volumetrically measured quantity of dialysate solution into the pump chamber. The diaphragm is actuated toward the pump chamber to pump the fluid therein out of an outlet.

The first flowbalance pump chamber100 has a clean dialysate solution inlet valve98 for receiving clean dialysate solution from theacid pump76 and a clean dialysatesolution outlet valve102 for pumping clean dialysate solution to thedialyser12. The first flowbalance pump chamber100 also has a spent dialysatesolution inlet valve118 for receiving spent dialysate from thedialyser12 and a spent dialysatesolution outlet valve120 for pumping the spent dialysate to drain viadrain outlet port122.

At any one time, only one of

valves

98,102,118 or120 will be open and the other three valves will be closed. The flow balance function, as described above, requires alternating the function of each flow balance pump approximately every 20 cycles. Therefore, when the firstflow balance pump100 is pumping clean dialysate solution to thedialyser12, onlyvalves98 and102 are in use and when the firstflow balance pump100 is pumping spent dialysate solution from thedialyser12 to drain, only

valves

118 and120 will be in use.

The clean dialysate solution is pumped out of the first flowbalance pump chamber100 through the first flow balance pump clean dialysatesolution outlet valve102, upon closure of the first flow balance pump clean dialysate inlet valve98, to thedialyser12 via thedialyser outlet port104.

Spent dialysate solution returns to thecartridge30 from thedialyser12 via thedialyser inlet port106. The second flowbalance pump chamber108 has a spent dialysatesolution inlet valve110 for receiving spent dialysate solution from thedialyser12 and a spent dialysatesolution outlet valve112 for pumping the spent dialysate solution to drain viadrain outlet port122. The secondflow balance pump108 also has a clean dialysate solution inlet valve114 for receiving clean dialysate solution from theacid pump chamber76 and a clean dialysatesolution outlet valve116 for pumping clean dialysate solution to thedialyser12.

At any one time, only one of

valves

110,112,114,116 will be open and the other three valves will be closed. When the secondflow balance pump108 is pumping clean dialysate solution to thedialyser12, onlyvalves114 and116 will be in use and when the secondflow balance pump108 is pumping spent dialysate solution from thedialyser12 to drain, onlyvalves114 and116 will be in use.

In the illustrated example, the operation of the first and second flow balance pumps100,108 can be switched so that the firstflow balance pump100 is used to draw spent dialysate solution from thedialyser12 and the secondflow balance pump108 is used to pump clean dialysate solution into thedialyser12 as described below.

The clean dialysate solution is drawn into the second flowbalance pump chamber108 from theacid pump76 via the second flow balance pump clean dialysate solution inlet valve114 upon actuation of the diaphragm. The clean dialysate solution is then pumped from the second flowbalance pump chamber108 via the second flow balance pump clean dialysatesolution outlet valve116, upon closure of the clean dialysate solution inlet valve114, to thedialyser12.

Spent dialysate solution from thedialyser12 is drawn into the firstflow balance pump100 via the second flow balance pump spent dialysatesolution inlet valve118. The spent dialysate solution is then pumped out of the first flowbalance pump chamber100 via the second flow balance pump spent dialysatesolution outlet valve120, upon closure of the spent dialysatesolution inlet valve118, to drain viadrain outlet port122.

The volume of fluid that is returned from thedialyser12 is greater than the volume of fluid that is pumped to the dialyser via the first or second

flow balance pump

100,108. The first and second flow balance pumps have fixed volumes meaning that the excess fluid volume cannot be accommodated in the first or second flow balance pump. Anultrafiltration pump200 is provided between the first and second flow balance pumps100,108 and has aninlet valve210 and anoutlet valve212. Theultrafiltration pump200 comprises a concave recess in the cartridge closed by a flexible diaphragm, the concave recess and the flexible diaphragm defining an ultrafiltration pump chamber.

In use, theinlet valve210 of theultrafiltration pump200 is opened to allow the ultrafiltration pump to draw in a pre-determined volume of spent dialysate solution. When theinlet valve210 of the ultrafiltration pump is open, theoutlet valve212 of theultrafiltration pump200 is closed. When theultrafiltration pump200 has received a volume of spent dialysate solution, theoutlet valve212 is opened and the spent dialysate solution in the ultrafiltration pump chamber is pumped through theoutlet valve212 to drain via thedrain outlet port122. When theoutlet valve212 of theultrafiltration pump200 is open, theinlet valve210 of theultrafiltration pump200 is closed.

FIG.2 shows a representative view of aflow balance pump100 according to the present invention. The flowbalance pump chamber194 is provided on the cartridge and is closed by a diaphragm196 which, at rest, sits across thepump chamber194. The pump chamber receives either clean or spent dialysate solution via a dialysatesolution inlet port210 and pumps dialysate solution from the pump chamber via a dialysatesolution outlet port212.

Thecartridge30 is removably mounted into a hemodialysis machine which has a flowbalance pump cavity198 substantially corresponding in dimension and shape to thepump chamber194. Upon supply of positive or negative pressure via a pump cavitypressure inlet port214, the diaphragm is actuated into either thepump chamber194 orpump cavity198 to either draw fluid into thepump chamber194 or pump fluid from thepump chamber194.

Cartridge Cleaning

After each use, the hemodialysis machine requires sanitising to prevent contamination of a patients bloodstream during subsequent dialysis sittings. Theremovable cartridge30, as described above, is usually disposed of after each sitting. In one embodiment of the invention, thecartridge30 is sanitised to allow re-use in subsequent dialysis sittings.

Asanitisation device188, such as a chemical cleaning receptacle, is connected to thecartridge30 using the following method (seeFIGS.3a to3d):

a) Connecting the spentdialysate solution inlet104 to the cleandialysate solution outlet106;
b) Connecting thewater outlet42 to thebicarbonate inlet50;
c) Disconnecting thedrain port122;
d) Connecting thewater inlet38 to apurified water supply31;
e) Flushing purified water through thecartridge30 and out of thedrain port122 and out of theacid inlet82;
f) Connecting thedrain port122 to theacid inlet82;
g) Connecting asanitisation device188 between the spentdialysate solution inlet104 and the cleandialysate solution outlet106;
h) Flowing a liquid through the cartridge and the sanitisation device in a first direction;
i) Flowing the liquid through thecartridge30 in a second direction;
j) Disconnecting thesanitisation device188 and re-connecting the spentdialysate solution inlet104 to the cleandialysate solution outlet106;
k) Flushing purified water through thecartridge30 and out of thedrain port122 and theacid inlet82;
l) Disconnecting allcartridge ports104,106,42,38,122; and,
m) Re-connecting thecartridge30 to thehemodialysis machine10.

An alternative method of cleaning the cartridge provides (SeeFIG.4):

a) Connecting the spentdialysate solution inlet104, cleandialysate solution outlet106,bicarbonate inlet50,acid inlet82 andwater outlet42 to achemical bath190;
b) Connecting thewater inlet38 to apurified water supply31;
c) Connecting thedrain port122 to a drain;
d) Flushing purified water through thecartridge30 and out of thedrain port122;
e) Flowing a cleaning chemical from thechemical bath190 through the cartridge130 in a first direction;
f) Measuring the conductivity level of the chemical to ensure that it indicates acid;
g) Flowing the chemical from thechemical bath190 through thecartridge30 in a second direction;
h) Flushing purified water through thecartridge30 and out of thedrain port122;
i) Measuring the conductivity of the purified water to ensure that it indicates purified water;
j) Disconnecting allcartridge ports104,106,50,82,42,38; and,
k) Re-connecting thecartridge30 to thehemodialysis machine10.

Thechemical bath190 may be provided with a heater to heat the cleaning chemical contained therein before the cleaning chemical is flowed through thecartridge30.

In another alternative method, with reference toFIG.5, thechemical bath190 could be replaced by a manifold192 with a chemical receptacle provided between the manifold and any one or more of the clean dialysate outlet, spent dialysate inlet, bicarbonate port, acid port and water outlet.

In any of the methods of cleaning the cartridge described, the cleaning chemical is drawn through the cartridge by one or more of the acid pump, bicarbonate pump, first flow balance pump or second flow balance pump.

Thedialyser12, if connected to thecartridge30, can also be cleaned by the cleaning liquid to allow re-use for subsequent dialysis sessions. Cleaning fluid, when passing through thedialyser12, permeates through the semi-permeable membrane of thedialyser12 and enters a blood pump (not shown) connected to thedialyser12. In this way, the membrane of thedialyser12 and the blood pump are cleaned in the same manner as thecartridge30.

The embodiments of the present invention, described with reference to the figures, are examples only and not exclude variations therefrom from the scope of the claims.