Patent Description:
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 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 dialysis fluid. The semi-permeable membrane filters the waste products and excess fluid from the blood into the dialysis fluid. The membrane allows the waste and a controlled volume of fluid to permeate into the dialysis fluid whilst preventing the loss of larger more desirable molecules, like blood cells and certain proteins and polypeptides.

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

Production of dialysis fluid is described in the applicant's own applications, <CIT>, <CIT>, <CIT> and <CIT>.

Further relevant prior art is for instance disclosed in documents <CIT>, <CIT> and <CIT>.

In simple terms, dialysis water is mixed with the bicarbonate buffer and the acid buffer to create a dialysis fluid for performing dialysis across a semi-permeable membrane in a dialyzer. Dialysis water is defined by the standard ISO <NUM>-<NUM>:<NUM>. Dialysis fluid is defined by the standard ISO <NUM>-<NUM>:<NUM>. The dialysis water may be generated by a water purification system which purifies domestic tap water by passing it through a prefiltration stage and then a reverse osmosis (RO) machine. Once supplied to the dialysis machine the dialysis water is heated to the correct temperature for treatment and is provided to the dialysis fluid mixing and pumping cassette where the acid and bicarbonate solutions are added to create dialysis fluid.

Patients being treated for a renal condition are typically required to either attend a medical facility, either in an acute setting, for example an intensive care ward or in a chronic setting, for example a dialysis ward or dialysis center. Some patient's requiring treatment for chronic conditions may be able to conduct dialysis at home.

Given the varied treatment settings, there is also a variation in the availability of dialysis water. For example a hospital dialysis ward may have access to a hospital water ring main, where dialysis water is provided from a hospital plant room. This may differ from an acute setting, such as an intensive care unit, where there is no provision of a hospital ring main. This may also differ from home use, where the only plentiful source of water is through the domestic tap. Given the varied treatment settings for dialysis, some may require the dialysis machine alone, whereas others may require both the dialysis machine and the RO machine.

Typically dialysis machines and RO machines need to be sanitized between uses and maintained in a sanitized condition. Conventionally, known dialysis machines are sanitized either through heat disinfection or chemical disinfection to ensure the microbiological quality of the supplied dialysis water and dialysis fluid is kept below acceptable levels as defined by the standard ISO <NUM>-<NUM>:<NUM>. RO machines are sanitized through either through heat disinfection or chemical disinfection to ensure the microbiological quality of the supplied dialysis water is kept below acceptable levels as defined by the standard ISO <NUM>-<NUM>:<NUM>. Water treatment equipment is governed by the standard ISO <NUM>-<NUM>:<NUM>, and dialysis machines specifically by the standard IEC <NUM>-<NUM>-<NUM>:<NUM>.

Such heat sanitization processes may be achieved by means of the A0 method which uses a knowledge of the lethality to microbiological contaminants of the particular process at different temperatures to assess the overall lethality to microbiological contaminants of the cycle and express this as the equivalent exposure time at a specified temperature. An example of the application of the A0 method to a dialysis machine is described in <CIT>.

Previous heat sanitizing systems for RO machines, such as the one disclosed in <CIT>, use a combination of a heating element located in the RO machine and chemical disinfectant in order to sanitize RO machines. This sanitization system only cleans the RO machine and not the dialysis machine attached to it.

RO machines and dialysis machines have independent sanitization routines. As such, the RO and dialysis machine must be sanitized independently. Often the devices must be disconnected from each other prior to the sanitization cycle. There is still the potential for bacteria to collect and to develop into biofilm in the fluid lines that connect the RO and dialysis machine as a result.

Known dialysis and RO systems are provided as independent systems with no shared functionality of control between the RO and dialysis machine when they are fluidly connected.

A portable dialysis system according to the present invention comprises the technical features as defined in independent claim <NUM>. A method of heat sanitization of a portable dialysis system according to the present invention comprises the technical features as defined in independent claim <NUM>.

In accordance with an aspect of the present invention, there is provided a portable dialysis machine having a main body portion; a water purification system, the water purification system being separate to the dialysis machine; and a liquid sanitizer; wherein the liquid sanitizer is provided within the main body portion of the dialysis machine; wherein the liquid sanitizer is fluidly connected between the dialysis machine and the water.

The liquid sanitizer heater is sized for heating dialysis water at <NUM> degrees Celsius from a typical inlet temperature of <NUM> degrees Celsius and at the typical flow rate of <NUM>/min in a dialysis treatment mode. This allows the dialysis machine to produce a continuous supply of dialysis fluid to be sent to a dialyser during treatment.

In liquid sanitization mode, the liquid sanitizer heater is required to heat dialysis water to approximately <NUM> to <NUM> degrees Celsius. Further, in liquid sanitization mode, the liquid sanitizer heater is required to maintain the heated dialysis water at approximately <NUM> to <NUM> degrees Celsius. In liquid sanitization mode a finite quantity of dialysis water is circulation around a closed fluid circuit of the dialysis machine at approximately <NUM>/min.

Since in liquid sanitization mode the sanitizing liquid is circulated around a closed fluid circuit and not used to prepare a continuous supply of dialysis fluid, the volume of dialysis water that must be heated is far smaller than in treatment mode and it is also increasing in temperature as it circulates around the closed fluid circuit. The liquid sanitizer heater therefore has spare capacity to effect further fluid heating.

The present invention takes advantage of that spare capacity to extend the closed fluid circuit to optionally further include the water purification system, and thereby increase the fluid volume of the closed fluid circuit. The present invention also takes advantage of that spare capacity to account for any additional heat loss experienced by circulating the heated fluid around the extended closed fluid circuit including the water purification system. The present invention further minimises the time between treatments which is necessary to sanitize the dialysis machine and the water purification system and the operator effort required therefore.

Since the liquid sanitizer is provided within the dialysis machine, it is not necessary for the water purification system to have a heater, thus the water purification system can be smaller, simpler, and inherently more reliable.

The liquid sanitizer controller may be controlled by a dialysis machine controller. The present invention allows for central control of the liquid sanitization of both the dialysis machine and the separate water purification system. This supports the ease of use of the dialysis system.

The dialysis machine may be provided with a graphical user interface, wherein the graphical user interface can provide instructions to the dialysis machine controller.

The water purification system may comprise a reverse osmosis machine.

The reverse osmosis machine may have a controller.

The liquid sanitizer controller may be configured to determine a time-temperature value for the volume of liquid periodically once a threshold temperature has been exceeded and calculate a cumulative time-temperature value for the first closed fluid circuit and the second closed fluid circuit.

The liquid sanitizer temperature sensor may be an inlet water temperature sensor arranged on a tank inlet adjacent a liquid sanitizer tank.

A liquid sanitizer outlet valve may be positioned adjacent a liquid sanitizer outlet to control the flow via either the liquid sanitizer outlet or a liquid sanitizer return line.

The RO machine controller may be controlled by the dialysis machine controller. Typically, whilst the dialysis machine is positioned at the optimum ergonomic height for the user, liquid sanitizers are often less accessible. Therefore control of the RO machine via the dialysis machine offers a better end-user experience.

In accordance with a further aspect of the present invention there is provided a method of heat sanitization of a portable dialysis system, the method comprising the steps of:.

The steps of circulating the volume of liquid through the first closed fluid circuit and circulating the volume of liquid through the second closed fluid circuit may be terminated in a sequential fashion.

The method may comprise the further steps of determining a time-temperature value for the volume of liquid periodically once the threshold temperature has been exceeded and calculating a cumulative time-temperature value based upon the determined time-temperature value.

The cumulative time-temperature value may be calculated according to <MAT>.

The A0 value for the first closed fluid circuit may be equal to A0<NUM> and the A0 value for the second closed fluid circuit may be equal to A0<NUM>, where A0<NUM> is greater than A0<NUM>.

The step of circulating the volume of liquid through a second closed fluid circuit may include using a water purification system pump.

The method may comprise the further step of providing an output signal once the cumulative time-temperature value has reached a level indicative of a sanitizing dose in both the first fluid circuit and the second closed fluid circuit.

The method may comprise the further step of ceasing circulation through the second closed fluid circuit once the cumulative time-temperature value equals a target cumulative time-temperature value.

The method may comprise the further step of setting at least one of the threshold temperature, the upper temperature or the target cumulative time-temperature value.

One or more of the embodiments of the invention can now be described, by way of example only, with reference to the accompanying drawings, in which:.

A dialysis system liquid sanitization system <NUM> comprises a dialysis machine <NUM>, a water purification system and a liquid sanitizer <NUM> fluidly connected there between. The water purification system is separate to the dialysis machine <NUM>. In the specific example, the water purification system comprises a reverse osmosis (RO) machine <NUM>.

The dialysis machine <NUM> has a main body <NUM> with a door <NUM> hinged to a forward-facing side of the main body <NUM>. The door <NUM> has a graphical user interface. The graphical user interface is a Liquid Crystal Display (LCD) unit <NUM> disposed on an outward-facing door surface and a door platen disposed on an inward-facing surface. The LCD unit <NUM> is touch sensitive allowing user inputs to control the dialysis machine <NUM> and liquid sanitization system <NUM> as will be described in more detail below. In alternative embodiments user input can be provided using buttons, dials or other suitable pieces of apparatus.

The door <NUM> closes against the main body <NUM> to define a recess <NUM> there-between. A dialysis fluid mixing and pumping cartridge <NUM> may be housed in the recess <NUM> as disclosed in <CIT>, <CIT> and <CIT>.

The main body <NUM> has a platen <NUM> behind which is an engine portion (not shown for clarity). The platen <NUM> is configured to receive the dialysis fluid mixing and pumping cartridge <NUM> within the recess <NUM>. The engine portion includes a pneumatic pump for providing pressure and vacuum to operate the dialysis machine <NUM>.

The dialysis machine <NUM> is further provided with a dialysis machine controller <NUM>.

The liquid sanitizer <NUM> is provided within the dialysis machine <NUM>. The liquid sanitizer <NUM> is provided within the main body <NUM> of the dialysis machine <NUM>. A dialysis machine fluid circuit <NUM> is fluidly connected to the liquid sanitizer <NUM> as will be described in more detail below.

The dialysis machine has a network of fluid pathways generally designated fluid circuit <NUM>. In dialysis use - the dialysis treatment mode - the dialysis machine fluid circuit <NUM> is connectable to the dialysis fluid mixing and pumping cartridge <NUM>, where dialysis water heated to approximately <NUM> degrees Celsius is drawn off. In sanitization use - liquid sanitization mode - the dialysis machine fluid circuit <NUM> is not connected to the dialysis fluid mixing and pumping cartridge <NUM>, instead dialysis water heated to approximately <NUM> to <NUM> degrees Celsius is not drawn off to the dialysis fluid mixing and pumping cartridge <NUM> but follows the arrows on <FIG> along the dialysis machine fluid circuit <NUM>.

The liquid sanitizer <NUM> has a number of fluid connections comprising a liquid sanitizer inlet <NUM>, a liquid sanitizer outlet <NUM>, a liquid sanitizer drain port <NUM> and a liquid sanitizer return line <NUM>. The liquid sanitizer drain port <NUM> is fluidly connected to a drain <NUM>.

The liquid sanitizer <NUM> has an inlet water temperature sensor <NUM>, a liquid sanitizer tank <NUM>, a liquid sanitizer pump <NUM>, and a liquid sanitizer controller <NUM>. The liquid sanitizer pump <NUM> may be a de-aeration pump, or another form of suitable pump. The liquid sanitizer pump <NUM> is disposed downstream of the liquid sanitizer tank <NUM> and inlet water temperature sensor <NUM>. The liquid sanitizer tank <NUM> has a liquid sanitizer heater <NUM>.

The liquid sanitizer inlet <NUM> is fluidly connected to the liquid sanitizer tank <NUM> with the inlet water temperature sensor <NUM> adjacent the liquid sanitizer inlet <NUM>, upstream of the liquid sanitizer tank <NUM>. The liquid sanitizer pump <NUM> is fluidly connected to the liquid sanitizer tank <NUM>. The dialysis machine fluid circuit <NUM> is fluidly connected to the liquid sanitizer pump <NUM>. The dialysis machine fluid circuit <NUM> is fluidly connected to the liquid sanitizer outlet <NUM> and separately, to the inlet water temperature sensor <NUM> via a liquid sanitizer return line <NUM>. A liquid sanitizer outlet valve <NUM> positioned adjacent the liquid sanitizer outlet <NUM> controls the flow via either the liquid sanitizer outlet <NUM> or the liquid sanitizer return line <NUM>.

Thus within the liquid sanitization system <NUM> a closed fluid circuit is provided comprising the inlet water temperature sensor <NUM>, the liquid sanitizer tank <NUM>, the liquid sanitizer pump <NUM>, the dialysis machine fluid circuit <NUM> and the liquid sanitizer return line <NUM>. This is the first closed fluid circuit.

The detailed structure of the liquid sanitizer <NUM> is shown in <FIG>. The liquid sanitizer tank <NUM> contains, in use, a volume of water <NUM>. The liquid sanitizer tank <NUM> has a tank inlet <NUM>, a tank drain <NUM> and a tank outlet <NUM>. The tank inlet <NUM> is fluidly connectable to a water source (the reverse osmosis machine). The tank drain <NUM> is fluidly connectable to the drain <NUM>. The tank outlet <NUM> is fluidly connected to the liquid sanitizer pump <NUM>.

The liquid sanitizer heater <NUM> has a heating element <NUM> arranged to heat the volume of water <NUM> contained within the liquid sanitizer tank <NUM>, in this case by immersion in the volume of water <NUM>. The liquid sanitizer heater <NUM> is electronically connected to the dialysis machine controller <NUM> by a heater connector <NUM>.

Temperature sensors are arranged in the liquid sanitizer <NUM>. An outlet temperature sensor <NUM> is arranged on the tank outlet <NUM> adjacent the liquid sanitizer tank <NUM>. The inlet water temperature sensor <NUM> is arranged on the tank inlet <NUM> adjacent the liquid sanitizer tank <NUM>. The temperature sensors <NUM>, <NUM> are electronically connected to the dialysis machine controller <NUM> via sensor connectors. The connectors may be wired or wireless. The dialysis machine controller <NUM> may be remote to both the liquid sanitizer tank <NUM> and liquid sanitizer heater <NUM>. The dialysis machine controller <NUM> thereby controls both the heating of the water and receives the temperature values for the sanitizing water circuit.

Referring back to <FIG>, the reverse osmosis (RO) machine <NUM> has an RO pump <NUM>, an RO filter membrane <NUM> and an RO controller <NUM>.

The RO controller <NUM> is connected to the dialysis machine controller <NUM>. The dialysis machine controller <NUM> can communicate with and control the RO controller <NUM>.

The reverse osmosis (RO) machine <NUM> has a number of fluid connections comprising an RO inlet <NUM>, an RO outlet <NUM>, an RO return <NUM>, an RO drain <NUM>. The RO inlet <NUM> is connected to a water source <NUM>, such as a domestic tap, via a prefiltration stage.

The RO inlet <NUM> is fluidly connected to the RO pump <NUM> with an RO non-return valve (NRV) <NUM> adjacent the RO inlet <NUM>. A common fluid line <NUM> fluidly connects the RO inlet <NUM> to the RO pump <NUM> downstream of the RO inlet NRV <NUM>. The RO pump <NUM> is fluidly connected to the RO filter membrane <NUM>. The RO filter membrane <NUM> is fluidly connected to the RO outlet <NUM>, and separately to the RO drain.

The RO return <NUM> is fluidly connected to the RO pump <NUM>, with a RO return NRV <NUM> adjacent the RO return <NUM>. The common fluid line <NUM> fluidly connects the RO return <NUM> to the RO pump <NUM> downstream of the RO return NRV <NUM>.

The RO drain <NUM> is fluidly connected to the common fluid line <NUM>, downstream of both the RO inlet NRV <NUM> and RO return NRV <NUM>.

The RO machine <NUM> is fluidly connected to a dialysis machine <NUM> and liquid sanitiser <NUM> as shown in <FIG>. The RO outlet <NUM> is fluidly connected to the liquid sanitizer inlet <NUM>. The RO return <NUM> is fluidly connected to the liquid sanitizer outlet <NUM>.

The fluid connections are made by fluid lines shown schematically in <FIG>. The fluid lines may be made of medical grade plastic or other suitable material. The fluid lines may be provided with thermally insulating covers which prevent thermal losses due to heat conduction.

Thus within the liquid sanitization system <NUM> a further closed circuit is provided comprising the inlet water temperature sensor <NUM>, the liquid sanitizer tank <NUM>, the liquid sanitizer pump <NUM>, the dialysis machine fluid circuit <NUM>, the RO return <NUM>, the RO return NRV <NUM>, the RO pump <NUM>, the RO filter membrane <NUM> and the RO outlet <NUM>. This is the second closed fluid circuit.

Depending upon the treatment setup, the dialysis machine <NUM> may be setup alone, or as part of a dialysis system liquid sanitization system <NUM> comprising the dialysis machine <NUM> and the water purification system. A portable unit may be used, as described in <CIT>.

The water purification system is removably provided within the portable unit, whereas the dialysis machine <NUM> is removably provided on an upper surface of the portable unit.

The dialysis machine <NUM> is used in a treatment mode to perform dialysis on a patient in a treatment session. The dialysis fluid mixing and pumping cartridge <NUM> is used to mix dialysis fluid constituent parts together with dialysis water from the RO machine <NUM>, and supply the mixed dialysis fluid to a dialyser in specific quantities at specific flow rates. The RO machine <NUM> in the treatment mode is operable to pump water at high pressure using the RO pump <NUM> (between <NUM> and <NUM> bar) across the RO filter membrane <NUM>. This generates purified water and waste water. The purified water is pumped to the dialysis machine <NUM> via the RO outlet <NUM>. The waste water is pumped to the drain <NUM> via the RO drain <NUM>. The ratio of generated purified water and waste water is known as the RO recovery rate. Typically, <NUM>% of the supplied water results in dialysis water and <NUM>% of the supplied water results in waste water.

In between treatment sessions, it is necessary to sanitize the fluid connections of the dialysis machine <NUM> and the RO machine <NUM>. This can be done to the dialysis machine <NUM> individually or to the dialysis machine <NUM> and the RO machine <NUM> combined at the same time.

The user turns on liquid sanitization system <NUM> via the graphical user interface of the dialysis machine <NUM>. The appropriate Liquid Sanitization Mode is selected and thus the appropriate fluid circuit is made available.

To select the first closed fluid circuit, liquid sanitizer outlet valve <NUM> diverts dialysis water along the liquid sanitizer return line <NUM>. To select the second first closed fluid circuit, liquid sanitizer outlet valve <NUM> diverts dialysis water out of liquid sanitizer outlet <NUM>.

The appropriate fluid circuit is primed with dialysis water from the RO machine <NUM>, which includes filling the liquid sanitizer tank <NUM> of the liquid sanitizer <NUM>.

For the first closed fluid circuit the liquid sanitizer pump <NUM> is activated to pump the dialysis water around the first closed fluid circuit. The dialysis water is gradually heated from a typical initial temperature of <NUM> degrees Celsius to a target temperature of <NUM> to <NUM> degrees Celsius as it passes through the liquid sanitizer tank <NUM>.

For the second closed fluid circuit the liquid sanitizer pump <NUM> and the RO pump <NUM> are activated to pump the dialysis water around the second closed fluid circuit. The RO machine controller <NUM> is controlled by the dialysis machine controller <NUM> in order to activate the RO pump <NUM>. The dialysis water is gradually heated from a typical initial temperature of <NUM> degrees Celsius to a target temperature of <NUM> to <NUM> degrees Celsius as it passes through the liquid sanitizer tank <NUM>.

Thus in both cases, the dialysis machine controller <NUM> activates the liquid sanitizer heater <NUM> to heat the volume of water <NUM> passing through the liquid sanitizer tank <NUM> via the heating element <NUM>.

When sanitizing the dialysis machine only (first closed fluid circuit), the heated water is circulated around from the liquid sanitizer tank <NUM>, the liquid sanitizer pump <NUM>, the dialysis machine fluid circuit <NUM>, the liquid sanitizer return line <NUM> and back to the liquid sanitizer tank <NUM> past inlet water temperature sensor <NUM>.

When sanitizing the dialysis machine and the reverse osmosis machine (second closed fluid circuit), the heated water is circulated around from the liquid sanitizer tank <NUM>, the liquid sanitizer pump <NUM>, the dialysis machine fluid circuit <NUM>, the RO return <NUM>, the RO return NRV <NUM>, the RO pump <NUM>, the RO filter membrane <NUM> and the RO outlet <NUM> and back to the liquid sanitizer tank <NUM> past inlet water temperature sensor <NUM>.

Again, in both cases, the dialysis water passes the inlet water temperature sensor <NUM> before re-entering the liquid sanitizer tank <NUM> as the dialysis water circulates around either the first or second closed fluid circuit.

The temperature of the water exiting the liquid sanitizer tank <NUM> via tank outlet <NUM> is periodically sensed by outlet temperature sensor <NUM>, and the temperature data is periodically sent to liquid sanitizer controller <NUM>. The temperature of the water returning to the liquid sanitizer tank <NUM> via tank inlet <NUM> is periodically sensed by inlet water temperature sensor <NUM>, and the temperature data is periodically sent to liquid sanitizer controller <NUM>. The liquid sanitizer controller <NUM> therefore periodically receives sensed temperature data to provide a feedback loop to moderate the heating of the volume of water <NUM> to maintain the temperature of the volume of water <NUM> above a threshold temperature. The threshold temperature is typically between <NUM> degrees Celsius and <NUM> degrees Celsius. The liquid sanitizer controller <NUM> may also moderate the heating of the volume of water <NUM> to maintain the temperature of the volume of water <NUM> below an upper temperature. The upper temperature may be between <NUM> degrees Celsius and <NUM> degrees Celsius.

When the liquid sanitizer controller <NUM> receives data from the inlet water temperature sensor <NUM> that the volume of water <NUM> has exceeded the threshold temperature, the liquid sanitizer controller <NUM> periodically samples the temperature of the volume of water <NUM> via the inlet water temperature sensor <NUM>, which theoretically represents the lowest possible temperature of the water on either of first and second closed fluid circuits.

The sampling is performed periodically at, for example, <NUM> second intervals. The sampling intervals may be varied as appropriate. Each sampled temperature represents a time-temperature value, which can be calculated by the liquid sanitizer controller <NUM>. The liquid sanitizer controller <NUM> calculates a cumulative time-temperature value for the volume of water <NUM> by summing the sampled time-temperature values. This is compared to a target total time-temperature value indicative of a sanitizing dose for either the first and second closed fluid circuits as appropriate.

Once the calculated cumulative time-temperature value and the target cumulative time-temperature value are equal, the liquid sanitizer controller <NUM> sends an output signal to indicate that a sanitizing dose has been reached. The output signal is received by the liquid sanitizer heater <NUM> and automatically switches off the liquid sanitizer heater <NUM>. The output signal is received by the liquid sanitizer pump <NUM> which is automatically switched off. In the case of the second closed fluid circuit, the output signal is also received by the RO controller <NUM> which relays the signal to the RO pump <NUM> which is automatically switched off.

In an alternate embodiment, the liquid sanitizer controller <NUM> may switch off the liquid sanitizer heater <NUM> in advance of a sanitizing dose being reached, by calculating that there is sufficient thermal energy contained within the appropriate closed fluid circuit that the water temperature will remain above the threshold temperature for long enough to ensure a sanitizing dose is reached. In that case, periodic sampling would be continued, such that the liquid sanitizer controller <NUM> is able to send the output signal to indicate that a sanitizing dose had indeed been reached.

The output signal is received by the graphical user interface, which displays the text "COMPLETE" in reference to the completed sanitizing dose. In alternate embodiments, the graphical user interface includes an audible alarm. The audible alarm can be configured to bleep repeatedly until the liquid sanitization system <NUM> is turned off.

In alternate embodiments the liquid sanitizer controller <NUM> calculates two cumulative time-temperature values and two target total time-temperature value indicative of a sanitizing dose. A first cumulative time-temperature value for the first closed fluid circuit and a first target time-temperature value indicative of a sanitizing dose in the first closed fluid circuit. A second cumulative time-temperature value for the second closed fluid circuit and a second target time-temperature value indicative of a sanitizing dose in the second closed fluid circuit. Having two separate cumulative time-temperature values and target time-temperature values allows for optimised control of the sanitization of the RO and dialysis machine. The sanitization can be tailored to each component using the different sanitization target times.

The heat sanitization processes may be achieved by means of the A0 method which uses a knowledge of the lethality to biofilms of the particular process at different temperatures to assess the overall lethality to biofilms of the cycle and express this as the equivalent exposure time at a specified temperature.

The A value is a measure of the heat resistance of a microorganism. A is defined as the equivalent time in seconds at <NUM> to give a sanitization effect. The z value indicates the temperature sensitivity of the reaction. It is defined as the change in temperature required to change the A value by a factor of <NUM>. When the z value is <NUM>, the term A0 is used. The A0 value of moist heat sanitization process is the equivalent time in seconds at a temperature of <NUM> delivered by that process to the product with reference to microorganisms possessing a z value of <NUM>.

In calculating A0 values a temperature threshold for the integration is set at <NUM> since for temperatures below <NUM> the z and D value of thermophilic organisms may change dramatically and below <NUM> there are a number or organisms which will actively replicate. In dialysis current practice, raising the temperature to <NUM> for <NUM> minutes gives a benchmark value A0 equal to <NUM>.

Claim 1:
A portable dialysis system (<NUM>) comprising:
a dialysis machine (<NUM>) having a main body portion (<NUM>);
a water purification system, the water purification system being separate to the dialysis machine (<NUM>);
and a liquid sanitizer (<NUM>);
wherein the liquid sanitizer (<NUM>) is provided within the main body portion (<NUM>) of the dialysis machine (<NUM>);
wherein the liquid sanitizer (<NUM>) is fluidly connected between the dialysis machine (<NUM>) and the water purification system,
the liquid sanitizer (<NUM>) having a heater (<NUM>) arranged to heat a volume of liquid, a temperature sensor (<NUM>, <NUM>) arranged to sense the temperature of the volume of liquid and a liquid sanitizer controller (<NUM>),
the dialysis system defining a first closed fluid circuit comprising the dialysis machine (<NUM>) and the liquid sanitizer (<NUM>), wherein the first closed fluid circuit is wholly within the dialysis machine main body portion (<NUM>), and a second closed fluid circuit comprising the water purification system, the dialysis machine (<NUM>) and the liquid sanitizer (<NUM>); and
wherein the liquid sanitizer (<NUM>) is configured to effect sanitization of the first closed fluid circuit and the second closed fluid circuit.