Patent Description:
The invention also relates to a method for performing a thermal disinfection procedure in a medical apparatus.

There are several types of treatments in which blood is extracted in an extracorporeal blood circuit. Such treatments involve, for example, haemodialysis, haemofiltration, haemodiafiltration, plasmapheresis, blood component separation, blood oxygenation, etc. Normally, blood is removed from a blood vessel at an access site and returned to the same blood vessel or at another location in the body.

A treatment fluid (also referred to as a dialysis fluid) and the patient's blood are made to flow on each side of a semi-permeable membrane of a membrane device (typically referred to as a dialyzer). Diffusive transfer is achieved from one side of the membrane to the other when the concentration of the substance on each side of the membrane differs. Such substances may be impurities in the blood (urea, creatinine, etc.) which thereby migrates from the blood to the treatment fluid. In treatment by haemodiafiltration, a convective transfer by ultrafiltration, resulting from a pressure difference created between the blood side and the treatment fluid side of the membrane, is added to the diffusive transfer.

An apparatus for extracorporeal blood treatment may include a dialysis machine which is connected to a disposable extracorporeal blood circuit. The disposable extracorporeal blood circuit includes blood transport lines (in general an arterial line for blood removal from the patient, and a venous line for blood return to the patient) and the membrane device for blood treatment.

The semi-permeable membrane of the membrane device divides a blood compartment, connected to the blood transport lines, and a fluid compartment, connected to treatment fluid supply and discharge circuits. The blood transport lines may be further coupled to a sensor and actuator system equipped on the dialysis machine, which system normally comprises means for blood circulation, pressure sensors, air bubble sensor, one or more circuit blocking clamps, blood detector, etc..

The treatment fluid supply circuit receives purified water from a water supply system. The water supply system may be a small unit providing water to only a single treatment control machine, but may also be a large unit providing water by means of a water system loop arrangement to a significant number of treatment units in for example a hospital or a clinic.

Dialysis fluid, which may come into contact with the patients' blood, is often prepared from the purified water through a treatment fluid supply circuit. It is of great importance that the dialysis fluid used for the treatment is substantially free from virus, fungi, bacteria and their residue and degradation products, such as endotoxins. Therefore, the treatment fluid path of a dialysis machine may be disinfected between dialysis treatments in order to reduce the presence of virus, fungi, bacteria, etc in the treatment fluid path. Chemical disinfection (e.g. using NaOCI or other chemical disinfection agents) is an efficient way to reduce the presence of bacteria, etc but it makes great demands on the following rinse procedure and requires very close measuring to assure that the treatment fluid path is free of chemical residual products for safety reasons before being used for subsequent treatments. The chemical process is also not environmentally friendly and may have a negative effect on the life-length of the disinfected parts and components.

In an alternative disinfection process, thermal disinfection is achieved by introducing hot water in the treatment fluid path. As a result, the problem of chemical residual products does not exist, the process puts less load on the environment, and often has comparatively less negative effect on the life-length of the disinfected parts and components compared to the use of biological aggressive solutions (as for example Chlorine).

In a further alternative disinfection process, the thermal disinfection is combined with chemical agents, such as citric acid, in order to achieve an efficient disinfection of the treatment fluid path. <CIT> discloses a disinfection arrangement for a dialysis machine consisting of a clean side and dirty side. The clean side comprises an inlet for water, a heat exchanger, as well as a water vessel containing a heater. A feed conduit leads from the water vessel to a tube which is normally connected to the clean side of the dialyzer but, during disinfection, is connected to a recirculation conduit via a valve in order to perform a first recirculation circuit. A second recirculation circuit is constituted by a recirculation conduit, a valve, a tube, which is normally connected to the dirty side of a dialyzer, a return conduit as well as a pump. A heat exchanger heats up the fluid in the second circuit with help of the fluid in the first circuit, which is heated up by the heater in the water vessel. A small amount of fluid is transferred from the first circuit to the second circuit via a shunt conduit.

Thermal disinfection of the treatment fluid path of a machine is preferably carried out after the treatment of each patient. As the number of dialysis patients increases there is a need to increase the available time for treatments in the clinics. Consequently, there is a desire to reduce the time spent on disinfection between treatments.

An increasing of the fluid temperature will lead to a reduction of the time required for the disinfection treatment to be carried out: anyhow, an excessive temperature may lead to fluid boiling, which leads to bubbles growth within the circuit, thus reducing the effectiveness of the disinfection treatment and determining damages to the fluid lines. On the other hand, if the fluid temperature is lowered to prevent boiling, the time requested for the circuit disinfection will increase accordingly.

<CIT> discloses a haemodialysis machine with sterilization unit. Disinfectant liquid boiling point T1 depends on ambient pressure and a boiling fluid may prevent an effective sterilization to occur. The proposed sterilization solution according to <CIT> includes two similar embodiments. In one first case, disinfection apparatus calculates disinfectant solution boiling point T1 based on measured atmospheric pressure value; disinfection apparatus sets the temperature of disinfectant solution at T2, slightly below boiling point T1; line end temperature T3 is measured and apparatus determines concentration N1 of disinfectant based on N1=k*(T3-<NUM>)*N, wherein N is the initial concentration of disinfectant solution, and k is concentration regulation coefficient between <NUM> and <NUM>. The apparatus determines disinfection time M based on concentration N1 of liquid: M=pT3+qN1, wherein 'p' is a temperature coefficient, and 'q' is a concentration factor. <CIT> deals with water system and dialysis machine hot water disinfection using the A<NUM> disinfection concept. The application describes using the disinfection algorithm A<NUM> for washer disinfectors (according to standard ISO <NUM>-<NUM>:<NUM>) in a water system/dialysis machine during disinfection processes.

<CIT> deals with a water purification apparatus capable of being cleaned at a point of care. The water purification apparatus provides an efficient use of a heater for heat disinfection, e.g. by recirculating heated fluid to further heat the fluid. Several different cleaning programs are provided that may be used for cleaning different parts of the water purification apparatus. In order to achieve this, the water purification apparatus runs heat disinfection programs to prevent growth of bacteria in the fluid path. The heat disinfection is based on the A<NUM> concept defining the dose of heat disinfection.

The scope of this invention is therefore to at least partially solve one or more of the drawbacks and/or limitations of the previous solutions.

A first scope is to provide a thermal disinfection system able to minimize the time required for the disinfection of a medical apparatus.

A further scope is to provide a thermal disinfection system able to maximize the disinfection effectiveness and, simultaneously, to reduce the time required for the disinfection procedure.

A further scope is to provide a thermal disinfection system able to minimize the time required for the disinfection and, simultaneously, to avoid damages to the hydraulic circuit of the medical apparatus.

A further scope is to provide a thermal disinfection system is a water purification apparatus connectable to a medical apparatus.

A thermal disinfection system according to the invention is disclosed in any one of claims <NUM>-<NUM>.

Some embodiments and some aspects of the invention will be described below with reference to the attached drawings, provided for illustrative purposes only, wherein:.

In this detailed description, corresponding parts illustrated in the various figures are indicated with the same numerical references. The figures may illustrate the invention by means of non-scale representations; therefore, parts and components illustrated in the figures relating to the object of the invention may relate exclusively to schematic representations.

The terms upstream and downstream refer to a direction or trajectory of advancement of a fluid configured to flow within the fluid line during normal usage of the apparatus or during a disinfection procedure.

According to the example of <FIG>, the thermal disinfection system <NUM> comprises a dialysis apparatus <NUM> having a hydraulic circuit <NUM>: the hydraulic circuit <NUM> comprises a feed arrangement 107a presenting at least one dialysis supply line <NUM> generally destined to transport a fluid, in particular water or purified water, from an inlet <NUM> towards an inlet <NUM> of a dialyzer <NUM> during a dialysis treatment.

The hydraulic circuit <NUM> further comprises a return arrangement <NUM> having at least one dialysis effluent line <NUM>, destined for the transport of a dialysate liquid (spent dialysate and/or liquid ultrafiltered from the blood through a semipermeable membrane <NUM> of the dialyzer <NUM>) from an outlet <NUM> of the dialyzer <NUM> towards an exit, schematically denoted by <NUM> in <FIG>.

The hydraulic circuit <NUM> cooperates with a blood circuit (not represented). The specific structure of the blood circuit is not fundamental, with reference to the present invention. Thus, simply a brief description of a possible embodiment of a blood circuit is made, which is however provided purely by way of non-limiting example. The blood circuit comprises a blood withdrawal line <NUM> designed to remove blood from a vascular access and connected to an inlet of a primary chamber, or blood chamber, of the dialyzer <NUM>. The blood circuit further comprises a blood return line <NUM> designed to return the treated blood to the vascular access and connected to an outlet <NUM> of the primary chamber of the dialyzer <NUM>.

The primary chamber of the dialyzer <NUM> communicates with the secondary chamber through the semipermeable membrane <NUM>, for example made of hollow-fibre type or plate type.

During a dialysis treatment, the dialysis supply line <NUM> is connected at the dialyzer treatment fluid inlet <NUM> of the secondary chamber, while the dialysis effluent line <NUM> is connected at the dialyzer treatment fluid outlet <NUM> of the secondary chamber. The blood circuit may also comprise one or more air separators, e.g. in the blood return line, upstream of a safety valve. Other air separators may be present in the blood circuit, such as positioned along the blood withdrawal line. The dialysis machine <NUM> may also comprise one or more blood pumps, for example positive displacement pumps such as peristaltic pumps, e.g. on the blood withdrawal line and optionally on the blood return line of the blood circuit.

With the aim of controlling the fluid passage towards/from the dialyzer <NUM>, a flow pump <NUM> and a suction pump <NUM> may be included, located respectively on the dialysis fluid supply line <NUM> and on the dialysate effluent line <NUM> and also operatively connected to a control unit <NUM> of the dialysis machine <NUM>. When preparing a fluid for treating a patient, purified water enters into the feed arrangement at inlet <NUM>. A heater <NUM> is also provided on the fluid supply line <NUM> and operatively connected to the control unit <NUM>: when the inlet valve <NUM> is open, the heater <NUM> is configured to heat up the water during a blood treatment session, i.e. at a temperature around <NUM>: alternatively, the heater <NUM> is configured to heat up the water during a disinfection procedure at higher temperatures T, i.e. with <NUM> <T<<NUM>. The heater may comprise an electric resistance configured to heat up due to electric current flow: the amount of heating energy or instant electric power provided by the heater <NUM> to the water may be set by controlling the amount of electric current flowing through the electric resistance. Alternatively, the control unit <NUM> may be configured to activate and deactivate the heater periodically to provide the water with a preset averaged heating energy.

Purified and heated water may be collected into a tank <NUM> provided with an expansion tube <NUM> to allow gases, eventually dissolved in the liquid, to be released to the atmosphere.

The apparatus also may also comprise a treatment fluid preparation unit <NUM> which may be of any known type, for example including one or more concentrate containers (A-concentrate <NUM> and B-concentrate <NUM>) and respective concentrate pumps (A-pump <NUM> and B-pump <NUM>) for the concentrate delivery, as well as at least a first and/or a second conductivity cell <NUM>, <NUM>.

Concentrate pump/s <NUM>, <NUM> is/are arranged in the delivery line/s 112a, 116a in order to allow the metered mixing of water and concentrated solution in the dialysis supply line <NUM>. The concentrate pump/s <NUM>, <NUM> is/are driven on the basis of the comparison between <NUM>) a target conductivity value for the mixture of liquids formed at respective infusion points where the dialysis supply line <NUM> joins the delivery line/s 112a, 116a, and <NUM>) the value of the conductivity of this mixture measured by means of a respective conductivity sensor <NUM>; <NUM> arranged in the dialysis supply line <NUM> downstream of the infusion point between the dialysis supply line <NUM> and the respective delivery line/s 112a, 116a. Instead of conductivity sensors <NUM>, <NUM>, concentration sensor may be provided on the dialysis supply line <NUM>. In particular, the first concentrate may be mixed with purified water in the dialysis supply line and the fluid conductivity measured immediately by the sensor <NUM> downstream the first infusion point. The second infusion point may be placed downstream the first conductivity sensor <NUM> and the second concentrate mixes with the fluid in the dialysis supply line. Conductivity or concentration of the prepared treatment fluid may be thereafter measured with the second conductivity sensor <NUM> before being directed to the dialyzer <NUM> during a blood treatment session. The dialysis fluid may contain, for example, ions of sodium, calcium, magnesium and potassium and the treatment fluid preparation unit <NUM> may be configured to prepare the dialysis fluid on the basis of a comparison between a target conductivity value and an actual conductivity value of the dialysis fluid measured by the conductivity sensors <NUM>, <NUM>. The concentrate pump/s <NUM>, <NUM> is/are generally configured to control the concentration of specific ionic substances in the dialysis liquid. Generally it is advantageous to control the sodium and bicarbonate concentration of the dialysis fluid.

According to an embodiment, only one conductivity sensor <NUM> may be used to control dialysis fluid preparation. The conductivity sensor <NUM> is placed on the feed arrangement downstream the infusion points of the first and second concentrate. Of course other kinds of treatment fluid preparation unit <NUM> might be equivalently used, having a single or further concentrate sources and/or a single or more pumps. Indeed, the treatment fluid preparation unit <NUM> may be any known system configured for on-line preparing dialysis fluid from water and concentrates.

The hydraulic circuit <NUM> also comprises a supply fluid temperature sensor <NUM> operatively connected to the control unit <NUM> and configured to provide a signal representative of the water temperature within the circuit. Temperature check of the fluid is useful both during a standard blood treatment session and during a disinfection procedure of the fluid lines as described in more detail in the following description. The supply fluid temperature sensor <NUM> is arranged on the supply line <NUM>. According to an embodiment, the temperature sensor <NUM> may be arranged downstream to the heater <NUM> to monitor the fluid outlet temperature. A second fluid supply temperature sensor <NUM>' may also be provided on the supply line <NUM> and arranged upstream the heater <NUM>. The treatment fluid outlet <NUM> of the dialysis supply line <NUM> may be connected to the fluid inlet <NUM> of the dialyzer <NUM> when treating a patient trough a treatment fluid removable connector <NUM>.

When disinfecting the feed arrangement 107a, a disinfectant and/or a heated fluid are circulated in the dialysis supply line <NUM>. In particular, the treatment fluid removable connector <NUM> of the dialysis supply line <NUM> is disconnected from the dialyzer <NUM> and is connected to a supply tube parking connector <NUM> provided in the chassis of the dialysis machine. A feed recirculation circuit <NUM> is designed to receive fluid from the supply tube parking connector <NUM> and to direct said fluid again to the feed arrangement 107a, in particular to the dialysis supply line <NUM> at a first connection point <NUM> immediately downstream the inlet valve <NUM> and upstream the heater <NUM>. With such a tubing configuration, an auxiliary fluid loop path is defined allowing fluid re-circulation in said closed loop path including, at least a portion of, the feed arrangement 107a and the feed recirculation circuit <NUM>. In the case the supply line <NUM> is provided with the second fluid supply temperature sensor <NUM>', the latter is interposed between the first connection point <NUM> and the inlet of the heater <NUM>.

During a thermal disinfection procedure, water is fed through the inlet <NUM> and heated to the desired disinfection temperature by heater <NUM>. For example the heater may be commanded by the control unit <NUM> to heat up water at a temperature comprised between <NUM> and <NUM>. The flow pump <NUM> operates continuously pumping the fluid in the auxiliary fluid loop path. Heated water passes along the feed arrangement 107a, the treatment fluid outlet <NUM>, a treatment fluid supply tube <NUM>, the supply tube parking connector <NUM> and the feed recirculation circuit <NUM> back to the feed arrangement 107a. In other terms, heated water is re-circulated in the closed auxiliary fluid loop path for a predetermined time period sufficient to perform heat disinfection of the portion of the hydraulic circuit upstream the dialyzer <NUM>.

A first return valve <NUM> is placed in the feed recirculation circuit <NUM> for enabling and preventing, respectively, the circulation of fluid in the auxiliary fluid loop path. The first return valve <NUM> is open during thermal disinfection. Optionally, disinfection efficiency during thermal disinfection procedure may be increased by using a disinfectant mixed with water: hot water mixed with a disinfectant solution determines an improvement in terms of disinfection and may allow to reduce the time required to reach a set disinfection threshold.

In an alternative embodiment, the heater <NUM> may be arranged in the feed recirculation circuit <NUM> to heat water in the loop path. Additionally, a first heater may be provided on the supply line <NUM>, as described before, and a second heater may be provided on the feed recirculation circuit <NUM>.

The hydraulic circuit <NUM> also comprises a return arrangement <NUM> arranged to remove the dialysis fluid from the dialyzer <NUM> during dialysis treatment and forward it to the exit <NUM>. The dialysis effluent line <NUM> may be provided with a respective return fluid removable connector <NUM> configured to be removably connected to the fluid outlet <NUM> of the dialyzer <NUM> when treating a patient to receive dialysate fluid and directing it towards the exit <NUM>. The exit is adapted for connection to a waste-bag or to a drain. A suction pump <NUM> and a second flow meter (not shown) are disposed on the dialysis effluent line <NUM>. The first and second flow meters may be used to control (in a known manner) the fluid balance of a patient connected to the blood circuit during a dialysis treatment session. A conductivity sensor, not shown, may be provided on the dialysis effluent line <NUM>, immediately downstream the dialyzer <NUM>, to measure conductivity of the dialysate.

Additionally, a return fluid temperature sensor <NUM> is also arranged on the dialysis effluent line <NUM> to measure the temperature of the fluid circulating in the return arrangement <NUM>: the return fluid temperature sensor <NUM> is preferably arranged downstream the suction pump <NUM>. A first exit valve <NUM> is placed in the return arrangement <NUM> immediately upstream the exit <NUM> for enabling or preventing fluid of the return arrangement to be lead to the exit.

During a disinfection procedure, heated fluid, optionally mixed with a disinfectant solution, is circulated in the dialysis effluent line <NUM>. In particular, the return fluid removable connector <NUM> of the dialysis effluent line <NUM> is disconnected from the dialyzer <NUM> and is connected to a return tube parking connector <NUM> provided in the chassis of the dialysis machine. A return recirculation circuit <NUM> is designed to receive fluid from the return tube parking connector <NUM> and to direct said fluid again to the return arrangement <NUM>, in particular to the dialysis effluent line <NUM> at a fourth connection point <NUM> immediately upstream the exit <NUM> and preferably the first exit valve <NUM>. With such a tubing configuration, a fluid loop path is defined allowing fluid re-circulation in a closed loop path including, at least a portion of, the return arrangement <NUM> and the return recirculation circuit <NUM>. In an embodiment (not shown), only the fluid loop path is present to recirculate fluid, particularly during disinfection procedure; the auxiliary fluid loop path not being present in the 'clean side' of the hydraulic circuit. In this embodiment, no feed recirculation circuit is provided. In case of thermal disinfection only, hot water, heated to the desired disinfection temperature e.g. by heater <NUM>, is fed to the fluid loop path through the feed arrangement 107a. For example water at a temperature of <NUM>° - <NUM>° degrees may be used.

It is noted that hot water may be provided via a by-pass line <NUM>, shown in <FIG>, or any other fluid connection between the dialysis supply line <NUM> (including the heater <NUM>) and the fluid loop paths. Alternatively, or in combination, an additional heater (not shown) may be provided in the return arrangement <NUM> or in the return recirculation circuit <NUM>, to heat water.

In another embodiment, a heat exchanger may be used to transfer heat from the fluid in the feed arrangement 107a to the fluid in the return arrangement <NUM> to reach the desired temperature of the fluid in the fluid loop path. Additional heater in the return arrangement may or may not be present.

During a thermal disinfection procedure, the control unit <NUM> commands the suction pump <NUM> to continuously pump the fluid in the fluid loop path. In particular, heated water passes through the return arrangement <NUM>, the return recirculation circuit <NUM>, the return tube parking connector <NUM>, a treatment fluid return tube <NUM>, a dialysate fluid return inlet <NUM>, and back to the return arrangement <NUM>. In other terms, heated water is re-circulated in the closed fluid loop path for a predetermined time period sufficient to perform heat disinfection of the portion of the hydraulic circuit downstream the dialyzer <NUM>. A second return valve <NUM> is placed in the return recirculation circuit <NUM> for enabling or preventing the circulation of fluid in the fluid loop path. The second return valve <NUM> is open during the thermal disinfection. Notably, disinfection of the fluid loop path may alternatively be obtained using a disinfectant mixed with water; disinfection may be achieved combined with heating of the disinfectant solution or not.

The hydraulic circuit <NUM> according to <FIG> also includes a feed forward arrangement <NUM> arranged to enable a fluid of the feed arrangement 107a to be forwarded to a waste bag or drain by-passing the fluid loop path, i.e. by-passing the portion of the return arrangement <NUM> upstream the first exit valve <NUM> and by-passing the return recirculation circuit <NUM>. In the embodiment of <FIG>, the feed forward arrangement <NUM> is connected on one side to the dialysis supply line <NUM> or to the bypass line <NUM> and on the other side is directly connected to the exit <NUM> of the return arrangement <NUM>. However, it is noted that the feed forward arrangement <NUM> may be directly connected to the drain (or waste-bag) without being connected to the return arrangement <NUM>. In other terms, the feed forward arrangement <NUM> may, in some embodiments, have a discharge end portion independent and not directly connected to other lines of the hydraulic circuit and freely placeable.

The feed forward arrangement <NUM> of <FIG> is connected to the auxiliary fluid loop path (in particular to the feed arrangement 107a) at a second connection point <NUM>. Fluid from the auxiliary fluid loop path may be withdrawn at the second connection point <NUM> and directed to the exit <NUM> without circulating in the fluid loop path before being discharged. In particular, in the examples, the feed forward arrangement <NUM> is connected to the return arrangement <NUM> at a sixth connecting point <NUM> placed downstream the fourth connecting point <NUM> where the return recirculation circuit <NUM> connects to the return arrangement <NUM>.

The feed forward arrangement <NUM> comprises a second exit valve <NUM> for enabling or preventing fluid of the feed arrangement to be lead to the exit through said feed forward arrangement.

The hydraulic circuit <NUM> may also comprise the bypass line <NUM> which connects the dialysis fluid supply line <NUM> and the dialysate effluent line <NUM> bypassing the dialyzer <NUM>, and one or more bypass valves <NUM> connected to the control unit <NUM> for selectively opening and closing the bypass line <NUM>. The bypass valve <NUM> on command of the control unit opens; further the control unit <NUM> closes the fluid passage towards the treatment zone and connect the inlet <NUM> directly with the dialysis effluent line <NUM> through the bypass line <NUM>.

In the example of <FIG>, a first tract of the by-pass line <NUM> between the second connection point <NUM> and a fifth connection point <NUM> is in common with the feed forward arrangement <NUM>. In other terms, by properly controlling opening/closure of the bypass valve <NUM> and of the second exit valve <NUM> it is possible to direct fluid from the feed arrangement 107a either towards the return arrangement <NUM> or towards the exit <NUM>. In addition, both bypass valve <NUM> and second exit valve <NUM> may be open at the same time whereby it is possible to direct fluid from the feed arrangement 107a both towards the return arrangement <NUM> and towards the exit <NUM>. The by-pass line <NUM> is connected to the return arrangement <NUM> at a third connection point <NUM>, upstream the suction pump <NUM>.

According to a further embodiment shown in <FIG>, the hydraulic circuit <NUM> may comprise a shunt tube 132a directly connecting, during a thermal disinfection procedure, the treatment fluid outlet <NUM> of the supply line <NUM> with the dialysate fluid return inlet <NUM> of the dialysis effluent line <NUM>. During the thermal disinfection procedure, the hot water passes through the supply line <NUM>, the shunt tube 132a, the effluent line <NUM> and towards the exit <NUM>. In addition, the hydraulic circuit <NUM> may be provided with an auxiliary bypass line 109a connecting the effluent line <NUM>, at a connecting point <NUM> upstream the exit <NUM>, with the supply line <NUM> at the connecting point <NUM>. In this configuration, during the thermal disinfection procedure, the hot water passes through the supply line <NUM>, the shunt tube 132a, the effluent line <NUM> and through the auxiliary bypass line 109a, defining a loop path for recirculating the hot water.

The dialysis apparatus also comprise a pressure sensor <NUM> configured to provide a signal representative of the atmospheric pressure around the dialysis apparatus. The pressure sensor <NUM> is operatively connected to the control unit <NUM> which is configured to receive the representative pressure signal from the pressure sensor <NUM> and to provide in output an atmospheric pressure value.

The apparatus may also comprise a user interface <NUM> (e.g. a graphic user interface or GUI) operatively connected to the control unit <NUM>. The control unit <NUM> may, for example, comprise one or more digital microprocessor units or one or more analog units or other combinations of analog units and digital units. Relating by way of example to a microprocessor unit, once the unit has performed a special program (for example a program coming from outside or directly integrated on the microprocessor card), the unit is programmed, defining a plurality of functional blocks which constitute means each designed to perform respective operations. The control unit <NUM> of the dialysis apparatus <NUM> is connected to the (graphic) user interface <NUM> through which it may receive instructions, for example target values, such as a fluid set temperature Tfluid_set, a threashold temperature TT, and a set disinfection dose A0_set as described in more detail in the thermal disinfection procedure section. The (graphic) user interface <NUM> may also receive instructions to perform a treatment session, i.e. a blood treatment session: i.e. the user interface <NUM> may receive the blood flow rate Qb, dialysis fluid flow rate Qdi, infusion liquid flow rate Qinf (where appropriate), patient weight loss WL. The control unit <NUM> furthermore may receive detected values by the sensors of the apparatus, such as the aforementioned flow meters, the conductivity sensors of treatment fluid preparation unit <NUM> and the conductivity sensor in the dialysis effluent line <NUM> and the first and second supply fluid temperature sensors <NUM>, <NUM>', and the return fluid temperature sensor <NUM>. On the basis of the instructions received and the operating modes and algorithms which have been programmed, the control unit <NUM> drives the actuators of the apparatus, such as the blood pump, the aforementioned flow and suction pumps <NUM>, <NUM>, and the treatment fluid preparation unit <NUM> to perform a blood treatment session or to perform a disinfection procedure. The control unit <NUM> may also provide information to the user (e.g. treatment parameters and machine parameters) through the (graphic) user interface <NUM> about a thermal disinfection procedure of the hydraulic circuit <NUM> or the.

According to a further embodiment shown in <FIG> and <FIG>, the thermal disinfection system <NUM> includes a water purification apparatus <NUM> fluidly connectable to one or more medical apparatuses, i.e. a peritoneal dialysis apparatus or to a blood treatment apparatus to provide purified water. In particular this embodiment covers both a water purification apparatus <NUM> connectable to the medical apparatus (wherein the medical apparatus is not included), and a medical apparatus, in particular a peritoneal dialysis apparatus or the blood treatment apparatus <NUM> previously described, comprising the water purification apparatus <NUM>.

In particular, the water purification apparatus <NUM> may be fluidly connected to the inlet <NUM> of the blood treatment apparatus <NUM> previously described to provide purified water. Alternatively, the water purification apparatus <NUM> may be fluidly connected to a disposable set <NUM> (see <FIG>) of a peritoneal dialysis apparatus.

A detailed description of the inner circuit of the water purification apparatus <NUM> is not fundamental for the purposes of the present invention: anyhow, an exemplary embodiment of a water purification apparatus <NUM>, as shown in <FIG> and <FIG>, connectable to a peritoneal dialysis apparatus is described here after.

The water purification apparatus <NUM> includes at least one between a pre-treatment module <NUM>, a reverse-osmosis (RO) module <NUM> and a post-treatment module <NUM>: <FIG> shows an exemplary embodiment of the main functional parts of the water purification apparatus <NUM>, including the pre-treatment module <NUM>, the reverse-osmosis (RO) module <NUM> and the post-treatment module <NUM>.

The water purification apparatus <NUM> comprises an inlet port <NUM> for feeding water from a water source <NUM>, e.g. a water tap, into the water purification apparatus <NUM>, for purification of the water. The incoming water from the water source is fed through the inlet port <NUM> into the pre-treatment module <NUM>.

The Pre-treatment module <NUM> treats the incoming water with a particle filter and a bed of activated carbon. The particle filter is arranged to remove particles such as clay, silt and silicon from the incoming water. The particle filter is arranged to prohibit particles in the size of micro meter, optionally also larger endotoxin molecules, from the incoming water. The bed of activated carbon is arranged to remove chlorine and compositions with chlorine from the incoming water, and to absorb toxic substances and pesticides. In an example embodiment, the bed of activated carbon is arranged to remove one or several of hypochlorite, chloramine and chlorine. In a further example embodiment, the bed of activated carbon is also arranged to reduce organic compounds (TOC total organic carbon) including pesticides of the incoming water. In some embodiments, the particle filter and the bed of activated carbon are integrated in one single consumable part. The consumable part is for example exchanged on a predefined interval dependent on the incoming water quality. The quality of the incoming water is for example examined and determined by qualified people before the first use of the water purification apparatus <NUM> at a point of care.

Optionally the pre-treatment module <NUM> comprises an ion exchange device for protection of downstream located devices such as a Reverse Osmosis, RO, membrane and a polisher. The pre-treatment module <NUM> thus filters the incoming water and delivers pre-treated water to a downstream located RO- module <NUM>. RO-module The RO-module <NUM> removes impurities from the filtered water, such as microorganisms, pyrogens and ionic material from the pre-treated water by the effect of reverse osmosis. The pre-treated water is pressurized by a pump and forced through RO-membrane to overcome the osmotic pressure. The RO-membrane is for example a semi-permeable membrane. Thereby the stream of pre-treated water, called feed water, is divided into a reject stream of water and a stream of permeate water. In an example embodiment, the reject water may be passed via a one or both of a first reject path and a second reject path. The first reject path recirculates reject water back to the feed fluid path of the RO-pump in order to be fed back into RO-device again. The recirculated reject water increases the feed flow to the RO-device, to get a sufficient flow past the reject side of the RO-membrane to minimize scaling and fouling of the RO-membrane. The second reject path directs reject water to drain. This makes the concentration level on the reject side to be sufficiently low to get an appropriate, required, permeate fluid concentration. If the feed water has low content of solutes, part of the drain flow can also be directed back to the inlet side of the RO-membrane and thereby increasing the water efficiency of the water purification apparatus <NUM>.

The RO-module <NUM> thus treats the pre-treated water and delivers permeate water to a downstream located post-treatment module <NUM>. Post-treatment module <NUM> polishes the permeate water in order to further remove ions from the permeate water. The permeate water is polished using a polisher device such as an Electrodeionization, EDI, device or a mixed bed filter device. The EDI-device makes use of electrodeionization for removing ions, from the permeate water, such as aluminum, lead, cadmium, chromium, sodium and/or potassium etc., which have penetrated the RO-membrane. The EDI-device utilizes electricity, ion exchange membranes and resin to deionize the permeate water and separate dissolved ions, i.e. impurities, from the permeate water. The EDI-device produce polished water, polished by the EDI-device to a higher purity level than the purity level of the permeate water. The EDI has an anti-bacterial effect of the product water and can reduce the amount of bacteria and endotoxins in the water due to, among other, the electrical field in the EDI-device. The mixed bed filter device comprises a column, or container, with a mixed bed ion exchange material. The purified water, also called as product water, is thereafter ready for being delivered from a product port <NUM> of the water purification apparatus <NUM> to a point of use of the product water. The product water is suitable for dialysis, i.e. for blood dialysis or peritoneal dialysis. In a further embodiment, the product water may be used for injection in the blood stream of a patient.

Optionally, the water purification apparatus <NUM> comprises a drain port <NUM>. The drain port <NUM> is in one example embodiment used for receiving used fluid, e.g. from a PD patient, via a drain line <NUM>, for further transport via a first drain path <NUM> inside the water purification apparatus <NUM> to a drain <NUM> of the water purification apparatus <NUM>. As a further option, the drain port <NUM> receives a sample of ready mixed solution for further transport to a conductivity sensor arranged in the water purification apparatus <NUM>, e.g. in the first drain path <NUM>.

In an example embodiment, a disposable line set <NUM> for peritoneal dialysis, shown in <FIG> may be fluidly connected to the product port <NUM> of the water purification apparatus <NUM> to receive the purified water.

Disposable set <NUM> includes an upstream water line segment 64a that extends to a water inlet 66a (<FIG>) of water an accumulator <NUM>. A downstream water line segment 64b extends from a water outlet 66b (<FIG>) of the water accumulator <NUM> to a cassette <NUM>. In the illustrated embodiment, upstream water line segment 64a begins at a water line connector <NUM>, which is located upstream from water accumulator <NUM>, configured to be connected to the product port <NUM> of the water purification apparatus <NUM>. Water purification apparatus <NUM> outputs purified water and water suitable for e.g. peritoneal dialysis ("WFPD"). WFPD is water suitable for making dialysis fluid for delivery to the peritoneal cavity of a patient P.

In one embodiment, a sterile sterilizing grade filter 70a is placed upstream from a downstream sterile sterilizing grade filter 70b. Filters 70a and 70b may be placed in water line segment 64a upstream of the water accumulator <NUM>. Sterile sterilizing grade filters 70a and 70b may be pass-through filters that do not have a reject line. Pore sizes for sterilizing filter may, for example, be less than a micron, such as <NUM> or <NUM> micron. Suitable sterile sterilizing grade filters 70a and 70b may, for example, be Pall IV-<NUM> or GVS Speedflow filters, or be filters provided by the assignee of the present disclosure. In alternative embodiments, only one or more than two sterile sterilizing grade filter are placed in water line segment 64a upstream of water accumulator <NUM>. The one or several sterile sterilizing grade filters may be arranged close to the water accumulator <NUM>, such that the fluid line set <NUM> becomes easier to fold. In further alternative embodiments, there are no sterile sterilizing grade filters in the water line segment 64a. The sterile sterilizing grade filters may for example be replaced by one or several ultrafilters located in the product fluid path of the water purification apparatus <NUM>.

Disposable line set <NUM> includes a patient line <NUM> that extends from a patient line port of cassette <NUM> and terminates at a patient line connector <NUM> to be connected to the patient. Patient line connector <NUM> connects to a patient transfer set <NUM>, which in turn connects to an indwelling catheter located in the peritoneal cavity of patient. Disposable line set <NUM> also includes a drain line <NUM> that extends from a drain line port of cassette <NUM> and terminates at a drain line connector <NUM>. Drain line connector <NUM> may be connected removably to the drain port <NUM> of the water purification apparatus <NUM>.

Disposable set <NUM> further comprises a last bag or sample line <NUM> that extends from a last bag or sample port of cassette <NUM>. Last bag or sample line <NUM> terminates at a connector <NUM>, which may be connected to a mating connector of a premixed last fill bag of dialysis fluid or to a sample bag or other sample collecting container. Last bag or sample line <NUM> and connector <NUM> may be used alternatively for a third type of concentrate if desired. Disposable set <NUM> includes a first concentrate line <NUM> extending from a first concentrate port of the cassette <NUM> and terminates at a first cassette concentrate connector 80a. The first cassette concentrate connector 80a is configured to be fluidly connected to a first concentrate container 84a holding a first, e.g., glucose, concentrate. A second concentrate line <NUM> extends from a second concentrate port of cassette <NUM> and terminates at a second cassette concentrate connector 82a. The second container concentrate connector 82b is configured to be fluidly connected to a second concentrate container 84b holding a second, e.g., buffer, concentrate.

In an embodiment, to begin treatment, patient P loads cassette <NUM> into a cycler and in a random or designated order (i) places heater/mixing bag <NUM> onto the cycler, (ii) connects upstream water line segment 64a to product port <NUM> of water purification apparatus <NUM>, (iii) connects drain line <NUM> to drain port <NUM> of water purification apparatus <NUM>, (iv) connects first cassette concentrate connector 80a to first container concentrate connector 80b, and (v) connects second cassette concentrate connector 82a to second container concentrate connector 82b. <FIG> illustrates a detailed embodiment of a water purification apparatus <NUM>.

The differences in line style of the fluid paths of <FIG> illustrate the main flows in a first fluid path (thicker lines) and a second fluid path (dash double dot line), during a general disinfection. With reference now to <FIG>, the RO-device <NUM> is arranged to produce a purified fluid flow and a reject fluid flow. In greater detail, the RO-device <NUM> comprises a feed inlet 301a, a permeate outlet 301b and a reject outlet 301c. The RO-membrane <NUM> separates the feed inlet 301a and the reject outlet 301c, from the permeate outlet 301b. A feed fluid path <NUM> is connected to the feed inlet 301a, in order to transport feed fluid to the feed inlet 301a. The feed fluid path <NUM> is arranged with a tank <NUM> for collecting fluid, and a RO-pump <NUM>, arranged to pump feed fluid to the feed inlet 301a. The RO-pump <NUM> is arranged downstream a tank <NUM>. The RO-pump <NUM> is configured to be controlled by a control unit to a certain pump rate corresponding to a certain flow rate of the permeate fluid.

The water purification apparatus <NUM> further comprises a purified fluid path <NUM>, connected to the permeate outlet 301b and to the product port <NUM>, in order to transport purified fluid from the permeate outlet 301b to the product port <NUM>. The purified fluid path <NUM> comprises the permeate fluid path 371a, a polisher fluid path 371b and a product fluid path 371c. The polisher fluid path 371b comprises a polisher-device <NUM>, for example an EDI-device or a mixed bed filter device. A bypass path 371d is arranged to bypass the polisher device. A three-way valve 305c is arranged to be controlled by the control unit <NUM> to direct the permeate fluid flow selectively to either into the polisher-device <NUM>, or into the bypass path 371d in order to bypass the polisher-device <NUM>. A first drain path <NUM> is connected to the drain port <NUM> and to the drain <NUM>, in order to pass fluid from the drain port <NUM> to the drain <NUM>. The first drain path <NUM> here embodies the part of a cycler drain path that is present inside the water purification apparatus <NUM>. The first drain path is arranged for example to transport drained PD-solution from the patient to the drain <NUM> of the water purification apparatus <NUM>.

The water purification apparatus <NUM> is further arranged with a heating unit <NUM>, also refereed as heater <NUM>, arranged to heat the purified fluid produced by the RO-device <NUM> downstream the RO-device <NUM>. The heater <NUM> may for example include a heating element. A first recirculation path <NUM>, is arranged to circulate heated purified fluid from a point downstream the RO-device <NUM> and downstream the heater <NUM>, to the feed fluid path <NUM>, inside the water purification apparatus <NUM>, upstream the pump <NUM> and the heater <NUM>. The heated purified fluid is here recirculated to the tank <NUM> and again fed to the feed inlet 301a of the RO-device <NUM>. However, the heated purified fluid is alternatively recirculated directly to the fluid line upstream the RO-pump <NUM>. The reject flow is feed back to the feed fluid path <NUM> via a first reject path 385b. The first reject path 385b is connected with, and in fluid communication with, the reject outlet 301c and the feed fluid path <NUM>. A second reject path <NUM>, is connected with, and in fluid communication with, the reject outlet 301c of the tank <NUM>. However, the second reject path <NUM> is alternatively connected with and in fluid communication with the feed fluid path <NUM>. A second drain path <NUM> may be arranged to feed reject fluid from the reject outlet 301c to a drain <NUM>. A valve 305b, i.e. a three-way valve, is arranged to selectively direct the reject flow into either the second reject path <NUM> or into the second drain path <NUM>. A constant flow device <NUM> is arranged to control the flow rate in the second reject path upstream the three-way valve 305b.

The water purification apparatus <NUM> may comprise a second recirculation path <NUM> arranged with a flow control device 305a. In one example embodiment, the second recirculation path <NUM> is referred to as a second fluid path. The second recirculation path <NUM> is arranged to transport the heated purified fluid inside the water purification apparatus <NUM>. In an exemplary embodiment, the second drain path <NUM> is also referred to as a second fluid path.

The control unit <NUM> is configured to perform a thermal disinfection procedure of the water purification apparatus <NUM>. This means to control cleaning of all, or parts of, the parts of the fluid path of the RO module <NUM> and post-treatment module <NUM> of the water purification apparatus <NUM> that are in contact with fluid. A fluid path is here meant to include tubes, lines, channels inside of apparatuses, ports, the tank, components such as valves, control devices etc. of the water purification apparatus <NUM>. The control unit <NUM> is configured to cause the water purification apparatus <NUM> to control heating, with the heater <NUM>, of the purified fluid from the RO-device <NUM>. The heater <NUM> comprises for example a heating rod. In one example embodiment, part of the permeate fluid path 371a is wound around the heating rod, in order to heat the purified fluid in the permeate fluid path 371a efficiently. Alternatively, the heater <NUM> comprises a heat exchanger, arranged to exchange heat between a heating medium and the fluid in permeate fluid path 371a. The heater <NUM> is in one embodiment configured to heat the purified fluid with a certain heating rate. By controlling the power to the heater <NUM>, and thus the power of the heater, the heating rate of the heater <NUM> can be regulated. The heating rate is however also dependent on the flow rate of the purified fluid.

A valve arrangement <NUM> is arranged to direct the heated purified fluid into the first fluid path or the second fluid path. The valve arrangement <NUM> comprises for example, but not limited to, one or several of: the flow control device 305a, the three-way valve 305b, a three-way valve 305c and a product water valve 305d.

The water purification apparatus <NUM> comprises one or more temperature sensors <NUM>, <NUM>, <NUM>.

Temperature sensor <NUM> is arranged to measure a temperature of the water downstream the heater <NUM>: in particular the temperature sensor <NUM> is arranged close to the outlet of the heater <NUM> so that the water temperature might be assumed as the maximum temperature of the water within the circuit. When the heated permeate fluid is directed to the first recirculation path <NUM>, the temperature of the heated permeate indicates the temperature of the fluid in the first recirculation path <NUM>. The temperature sensor <NUM> may also be called as high temperature sensor <NUM>. Furthermore, a product fluid temperature sensor <NUM> may be arranged downstream the EDI-device <NUM> to measure the temperature of the water, thus the temperature of the fluid in the product fluid path 371c. Furthermore, a product fluid temperature sensor <NUM> may be arranged upstream the heating unit <NUM>: in particular the temperature sensor <NUM> is arranged close to the inlet of the heating unit <NUM> so that the water temperature might be assumed as the lowest temperature of the water within the circuit. The temperature sensor <NUM> may also be called as low temperature sensor <NUM>.

A flow sensor <NUM> is arranged to measure a flow rate of the purified fluid. The flow sensor <NUM> is here arranged to the fluid path 371a and is arranged to measure the flow rate of the permeate fluid from the RO-device <NUM>. The flow sensor <NUM> is arranged downstream the permeate outlet 301b, and upstream the heater <NUM>, for example directly downstream the RO-device <NUM>.

For cleaning the water purification apparatus <NUM>, the control unit <NUM> is configured to control the valve arrangement <NUM> to re-circulate the heated purified fluid in a first fluid path, e.g. the first recirculation path <NUM>, until a first temperature dependent criterion is fulfilled.

The water purification apparatus <NUM> or the peritoneal dialysis apparatus also comprises the pressure sensor <NUM> configured to provide a signal representative of the atmospheric pressure around the dialysis apparatus. The pressure sensor <NUM> is operatively connected to the control unit <NUM> which is configured to receive the representative pressure signal from the pressure sensor <NUM> and to provide in output an atmospheric pressure value. The peritoneal dialysis apparatus of the above-described embodiment may also comprise a user interface <NUM> (e.g. a graphic user interface or GUI) operatively connected to the control unit <NUM> similar or equivalent to the user interface <NUM> of the blood treatment apparatus <NUM> previously described. The control unit <NUM> may, for example, comprise one or more digital microprocessor units or one or more analog units or other combinations of analog units and digital units. Relating by way of example to a microprocessor unit, once the unit has performed a special program (for example a program coming from outside or directly integrated on the microprocessor card), the unit is programmed, defining a plurality of functional blocks which constitute means each designed to perform respective operations.

The present invention is directed to a thermal disinfection system <NUM> configured to perform a disinfection procedure of the hydraulic circuit of the medical apparatus <NUM>, such as a blood treatment apparatus <NUM> previously described. Alternatively, the thermal disinfection system <NUM> is configured to perform a disinfection procedure of the purifying water system <NUM>, according to the above description, fluidly connectable to one or more medical apparatuses to provide water: this medical apparatus may be one or more blood treatment apparatuses <NUM> or a peritoneal dialysis apparatus for home use. Still in an alternative embodiment, the thermal disinfection system <NUM> is configured to perform a disinfection procedure of a peritoneal dialysis apparatus, in particular a disinfection procedure of fluid lines of a peritoneal dialysis apparatus, wherein the fluid lines may comprise disposable fluid lines or operational fluid lines internal to the peritoneal dialysis apparatus.

The disinfection procedure comprises at least the steps of receiving a temperature signal from a temperature sensor <NUM>, <NUM>', <NUM>; <NUM>, <NUM> and determining a measured temperature value Tfluid_mes of the fluid within the hydraulic circuit <NUM>. Furthermore, the thermal disinfection procedure comprises the steps of receiving the pressure signal from the a pressure sensor <NUM>; <NUM>, determining a measured local atmospheric pressure value Patm, and driving the heating unit <NUM>; <NUM> to heat up the fluid based on the measured temperature value Tfluid_mes, and on the measured local atmospheric pressure value Patm.

The thermal disinfection procedure also comprises determining a set temperature Tfluid_set of the fluid based on the local atmospheric pressure value Patm, wherein this set temperature Tfluid_set is comprised between <NUM> and <NUM>, in particular between <NUM> and <NUM>. Thus, the thermal disinfection procedure comprises controlling the heating unit <NUM>; <NUM> based on the measured temperature value Tfluid_mes, to heat up the fluid up to, and in particular not beyond, the set temperature Tfluid_set. In particular the control unit <NUM> is configured to compare the measured temperature value Tfluid_mes with the set temperature Tfluid_set, compute a difference between the measured temperature value Tfluid_mes with the set temperature Tfluid_set, and based on this difference controlling the heating unit <NUM>; <NUM> to heat up the fluid up to, and in particular not beyond, the set temperature Tfluid_set.

The local atmospheric pressure value Patm is related to the fluid set temperature Tfluid_set by a predefined relationship: this relationship defines a boiling point temperature BPT as a function of the local atmospheric pressure value Patm. For example, water at a local pressure of 1ATM has boiling point temperature BPT equal to <NUM>: a decrease of the local temperature determines a decrease of the boiling point temperature BPT according to a well know relationship. According to the present invention, the fluid set temperature Tfluid_set may be comprised between limits as <NUM> · BPT < Tfluid_set < BPT, more in particular <NUM> · BPT < Tfluid_set < <NUM> · BPT, more in particular <NUM> · BPT < Tfluid_set < <NUM> · BPT.

Notably, the thermal disinfection procedure aims to maximize the fluid set temperature Tfluid_set based on the local atmospheric pressure value Patm avoiding boiling of the fluid within the hydraulic circuit <NUM>. For example, if the local pressure is 1ATM, the fluid set temperature Tfluid_set will be heated up as close as possible to <NUM>: higher temperatures will be avoided in order to prevent boiling of the fluid within the hydraulic circuit <NUM> which may cause damage to the circuit itself or determine a poor disinfection efficiency.

The thermal disinfection procedure may comprises a step of continuously updating measurements of the local atmospheric pressure Patm during the thermal disinfection procedure according to a predetermined sample rate comprised between <NUM>,<NUM> and <NUM>, in particular comprised between <NUM>,<NUM> and <NUM>. The continuous updating may be periodic or random in time or based on a preset algorithm. Analogously, the thermal disinfection procedure may comprises a step of continuously updating the set temperature Tfluid_set during the disinfection procedure based on the updated measurements of the local atmospheric pressure Patm: in other terms, if the local atmospheric pressure Patm changes during the disinfection procedure, the set temperature Tfluid_set will be changed accordingly. In this way, if the local atmospheric pressure Patm increases during the disinfection procedure, the set temperature Tfluid_set will be increased as well, so that the time required to perform the disinfection procedure decreases as described here after in more detail.

Alternatively, the thermal disinfection procedure may comprises a step of measuring the local atmospheric pressure Patm by the pressure sensor <NUM>,<NUM> only at an initial stage of the disinfection procedure or just before starting of the thermal disinfection procedure: therefore, the fluid set temperature Tfluid_set is also set at the initial stage of the thermal disinfection procedure according to the measured local atmospheric pressure Patm, and kept constant during the whole thermal disinfection procedure. In this case, pressure fluctuations during the disinfection procedure are not taken into account and the set temperature Tfluid_set does not change as well.

According to the standard ISO <NUM>-<NUM>: <NUM> "washer-disinfectors - part <NUM>: general requirements, terms and definition" the definition of cleaning is "removal of contamination from an item to the extent necessary for its further processing and its intended subsequent use". Disinfection is specified by reference to time and temperature for thermal disinfection. According to the standard, whenever practical, thermal disinfection is preferred as it is more easily controlled and avoid the hazards to staff, patients and the environment that can occur through the use of chemical disinfectants.

The definition of the thermal disinfection process may be achieved through an "A<NUM>" method which uses knowledge of the lethality of the particular process at different temperatures to assess the overall lethality of the cycle and express this as the equivalent exposure time at a specified temperature. The term "A", also referred as the disinfection dose, is defined as the equivalent time in seconds at <NUM> which generates a certain disinfection action against microorganisms with a defined "z" value, where the "z" value is a measurement, expressed in °C, of the temperature relationship to the killing process. Based on the definition, the "z" value corresponds to the increase in temperature required to reduce a "D" value of a particular microorganism by <NUM>%: the "D" value is the time required at a given temperature to kill <NUM>% of a population of the respective microorganisms (Decimal reduction time). The "z" value of a microorganism thus increases in tandem with growing resistance of this organism. Bacterial spores, which are the most resistant of all microorganism, have an average value of z = <NUM>. This z value is also employed in the "A<NUM>" concept, despite the fact that spores are not an explicit goal targeted by thermal disinfection. Selection of the "z" value can be seen, however, as a safety reserve when defining disinfection parameters. In the case of z = <NUM>, the term "A<NUM>" is used instead of "A". A given "A<NUM>" value can be achieved with the most diverse temperature/time combinations.

The mathematic formula for calculation of A0 is as follows: <MAT> where "A<NUM>" is the "A" value when z = <NUM>; Δt is the chosen time interval in seconds; T is the fluid temperature in °C measured at the time "t". A lower temperature limit for the integration is set at <NUM>. Consequently, A<NUM> is a time related unit which is dependent on temperature. As an example, A<NUM>= <NUM> may be achieved by <NUM> at <NUM>, or by <NUM> at <NUM> or by <NUM> at <NUM>. <FIG> shows a diagram with the relationship between time and temperature for A<NUM>= <NUM>. For sterilization of medical devices, values of A<NUM> comprised between <NUM> and <NUM> may be used: anyhow, lower or higher values of A<NUM> may be set according to the need.

In the case wherein the water temperature is constant ("Tconstant") along the whole disinfection procedure, the disinfection dose A<NUM> may be calculated by the following formula: <MAT> where "A<NUM>" is the "A" value when z = <NUM>; tproc is the time duration of the disinfection procedure; Tconstant is the fluid temperature in °C maintained during the whole disinfection process.

<FIG> shows the evolution of time, in minutes, required to complete a disinfection procedure as a function of the fluid temperature Tfluid_set according to the equations <NUM> and <NUM>, wherein the set disinfection dose A0_set is <NUM>. The higher the fluid temperature, the lower is the time required for the disinfection procedure to be carried on.

Based on what above, the thermal disinfection procedure further comprises the steps of receiving a set disinfection dose A0_set representative of a disinfection grade required, and calculating, during the disinfection procedure, an achieved disinfection dose A0_achieved. In particular, the disinfection procedure comprises comparing the achieved disinfection dose A0_achieved with the set disinfection dose A0_set and, based on this comparison, discontinue the disinfection procedure if the achieved disinfection dose A0_achieved equals or exceeds the set disinfection dose A0_set. The set disinfection dose A0_set may be comprised between <NUM> and <NUM>, in particular between <NUM> and <NUM>, more in particular between <NUM> and <NUM>. Notably, the calculating step of the achieved disinfection dose A0_achieved is based on a reference fluid temperature Tref (namely the fluid temperature T in °C measured at the time "t" referred to in equations <NUM> and <NUM> reported above) measured by the at least one temperature sensor <NUM>, <NUM>', <NUM>, wherein the reference fluid temperature Tref is assumed to be substantially the lowest fluid temperature within the hydraulic circuit <NUM> during the thermal disinfection procedure for safety reasons. For example, according to the circuit of <FIG> and <FIG>, the temperature sensor <NUM>' may be also called as the low temperature sensor <NUM>', wherein the latter is arranged upstream the heating unit <NUM> and close to the inlet of the heating unit <NUM>: thus, the low temperature sensor <NUM>' is configured to detect the reference fluid temperature Tref. Alternatively, the reference fluid temperature Tref may be measured by the return fluid temperature sensor <NUM>, which is preferably arranged as close as possible to the drain exit <NUM>, when the hydraulic circuit <NUM> is in an open configuration wherein the heated fluid flows from the inlet <NUM>, through the dialysis supply line <NUM> and the dialysis effluent line <NUM>, and towards the drain exit <NUM>.

Alternatively, according to the circuit of <FIG>, a temperature sensor <NUM>, also called as low temperature sensor <NUM>, may be arranged upstream the heating unit <NUM>. On the other hand, the fluid temperature value Tfluid_mes of the fluid may be measured by the temperature sensor <NUM>, <NUM> also called high temperature sensor <NUM>, <NUM> arranged downstream the heating unit <NUM>,<NUM>; in particular the high temperature sensor <NUM>,<NUM> is arranged close to the outlet of the heating unit <NUM>,<NUM> on the dialysis supply line <NUM>. Therefore, during the disinfection procedure, the high temperature sensor <NUM>, <NUM> is configured to detect the fluid temperature value Tfluid_mes of the fluid and the control unit <NUM> is configured to control the heating unit <NUM>,<NUM> so that Tfluid_mes=Tfluid_set. In particular the control unit <NUM> is configured, during the disinfection procedure, to control heating power or energy provided by the heating unit <NUM>, <NUM> to the fluid to reach the desired fluid temperature Tfluid_set. The heating power is controlled by varying the electric energy provided.

The disinfection procedure is completed when A0_achieved ≥ A0_set corresponding to a disinfection procedure time period DPt: the disinfection procedure comprises step of storing in a memory, in particular a digital memory, this time period DPt relative to the completed disinfection procedure. Subsequently, the control unit <NUM> is configured to determine the starting time of a subsequent disinfection procedure based on this time period DPt of the preceding disinfection procedure. The thermal disinfection procedure may also comprise a step of receiving or storing a threshold temperature value TT, such that the step of the disinfection procedure of calculating the achieved disinfection dose A0_achieved starts when a measured temperature of the heated fluid equals or exceeds said threshold temperature value TT: in particular this measured temperature of the heated fluid is the fluid reference temperature Tref. The achieved disinfection dose A0_achieved is computed only based on time periods when the measured temperature of the fluid exceeds this threshold temperature value TT. On the contrary, during time periods wherein the measured temperature of the fluid is lower than this threshold temperature value TT, the achieved disinfection dose A0_achieved is not computed. In other terms, the achieved disinfection dose A0_achieved does not increment during time periods wherein the measured temperature of the fluid is lower than this threshold temperature value TT.

<FIG> shows an exemplary heating curve of the fluid temperature within the hydraulic circuit <NUM> as a function of the elapsed time. C1 curve represents the initial fluid temperature (i.e. <NUM>) before the disinfection procedure has started. Heating of the fluid starts at time t<NUM>, corresponding to the time when the control unit <NUM> activates the heating unit: C2 curve represents fluid temperature increase versus time, which occurs between t<NUM> and t<NUM>: in particular the fluid temperature curve C2 is preferably measured by the low temperature sensor of the hydraulic circuit and used to compute the achieved disinfection dose A0_achieved. Notably, the fact that the fluid temperature of the curve C2 in <FIG> does not reach a flat constant maximum temperature, does not limit the present disclosure: indeed, during a thermal disinfection procedure the fluid measured temperature may definitely reach a plateau temperature (level C5) and maintained until the thermal disinfection procedure is completed. The plateau temperature is caused by the fact that the fluid maximum temperature at the outlet of the heating unit is controlled and maintained at a maximum fixed temperature Tfluid_set.

The curve C6 represents the threshold temperature value TT: when the fluid temperature curve C2 reaches the threshold temperature value TT at time t<NUM>, the disinfection procedure starts computing the achieved disinfection dose A0_achieved. Calculation of the achieved disinfection dose A0_achieved is performed between t<NUM> and t<NUM>. On the contrary, between t<NUM> and t<NUM>, the achieved disinfection dose A0_achieved is not computed. The level C5 is the maximum temperature reached by the fluid at the low temperature sensor: indeed, the temperature detected at the high temperature sensor, namely at the outlet of the heating unit, may be higher than that represented by the curve C2. The curve C3 shows the fluid temperature decreasing which occurs when the thermal disinfection procedure is terminated, in particular when the control unit <NUM> deactivate the heating unit.

The thermal disinfection procedure of the hydraulic circuit <NUM> further comprises activating the pump <NUM>, <NUM>; <NUM> during the thermal disinfection procedure to determine flowing of the heated fluid within the hydraulic circuit <NUM>. The thermal disinfection procedure, in order to exclude the dialyzer from the hydraulic circuit to be disinfected, may comprise a step of connecting a shunt tube 132a between the dialysis fluid supply outlet <NUM> and the dialysate fluid return inlet <NUM>. In addition, the hydraulic circuit <NUM> may be configurable, at least during the disinfection procedure, in a loop circuit for recirculation of the heated fluid: according to the circuits previously described, the loop circuit may comprise the heating unit <NUM>, the pump <NUM>, <NUM>, the at least one temperature sensor <NUM>, <NUM>', <NUM>, at least part of the dialysis supply line <NUM>, at least part of the dialysis effluent line <NUM>, optionally one or more by-pass lines <NUM>, 109a fluidly connecting the dialysis supply line <NUM> with the dialysis effluent line <NUM>, and optionally the shunt tube 132a. The disinfection procedure may imply to command, in an open or closed position, one or more valves <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the dialysis apparatus to define this loop circuit for recirculation of the heated fluid. With the term loop circuit it is meant a path wherein the same heated fluid circulates to perform the disinfection procedure. In a further implementation, the control unit <NUM> may receive the local atmospheric pressure value Patm and based on the maximum temperature achievable without the fluid boiling into the lines determine which is the most efficient disinfection procedure among different disinfection procedures. Indeed, based on the local atmospheric pressure value Patm and/or the (maximum) set temperature Tfluid_set thereby achievable during the disinfection procedure, the control unit <NUM> may provide information to the user (e.g., through a user interface) about the disinfection procedure that takes the least time to perform. The user may select the proposed procedure or deny and continue with a different procedure.

In general, thermal disinfection procedure (in more detail using the A<NUM> concept) is preferred. However, based on the atmospheric pressure condition (and on the desired disinfection level required e.g., the A<NUM> set target value to be achieved), time to obtain the thermal disinfection may be too long and chemical disinfection could be preferred. In other terms, with a chosen temperature for heat disinfection the system may estimate the time needed to complete a thermal heat disinfection (based on fluid path design and empirical tests). The estimated time could be used as indication for the user when about to start heat disinfection. From this indication, the user may decide to continue with heat disinfection or choose another type of disinfection to save time between treatments. With a low temperature the heat disinfection may take a too long time to be considered as efficient and a chemical disinfection (with or without heat applied) could be a better choice.

The control unit <NUM> based on the determined set temperature Tfluid_set calculates an estimated time Test to completion of the thermal disinfection procedure; compares the estimated time Test to completion of the thermal disinfection procedure with a reference time; based on the comparison outcome, the control unit <NUM> continues with the thermal disinfection procedure or recommend (on the user interface) or starts a different disinfection procedure, such as a chemical disinfection procedure. In particular the reference time may be the time required for a different (e.g., chemical) disinfection with regard to the thermal disinfection. Therefore, said different disinfection procedure requires less time for disinfection than thermal disinfection procedure. In one example, the different disinfection procedure is a chemical disinfection, using a chemical disinfection agent, such as NaOCl. Alternatively, another disinfection agent may be used, such as citric acid.

Furthermore, the different disinfection procedure may also be based on heating a fluid that includes a chemical agent (i.e., it is a chemical and thermic disinfection); this is advantageous if reduces the disinfection time.

Claim 1:
Thermal disinfection system (<NUM>) including a blood treatment apparatus (<NUM>) comprising a hydraulic circuit (<NUM>) for fluid transit, the hydraulic circuit (<NUM>) having:
- at least one dialysis supply line (<NUM>) extending from a fluid inlet (<NUM>) to a dialysis fluid supply outlet (<NUM>) connectable with an inlet of a dialyzer (<NUM>);
- a dialysis effluent line (<NUM>) extending from a dialysate fluid return inlet (<NUM>) to a drain exit (<NUM>), the dialysate fluid return inlet (<NUM>) being configured to connect with an outlet of the dialyzer (<NUM>);
- a heating unit (<NUM>) configured to heat up a fluid, in particular water or a disinfectant solution or dialysis fluid or a mixture thereof, within the hydraulic circuit (<NUM>);
- at least one temperature sensor (<NUM>, <NUM>', <NUM>) configured to provide a signal representative of a fluid temperature within the hydraulic circuit (<NUM>);
- at least one pressure sensor (<NUM>) configured to provide a signal representative of a local atmospheric pressure;
the blood treatment apparatus (<NUM>) comprising a control unit (<NUM>) configured to perform a thermal disinfection procedure of the hydraulic circuit (<NUM>), the thermal disinfection procedure comprising at least the following steps performed by the control unit (<NUM>):
- receiving the temperature signal from the at least one temperature sensor (<NUM>, <NUM>', <NUM>) and determining a measured temperature value (Tfluid_mes) of the fluid within the hydraulic circuit (<NUM>);
- receiving the pressure signal from the at least one pressure sensor (<NUM>) and determining a measured local atmospheric pressure value (Patm);
- determining a set temperature (Tfluid_set) of the fluid based on the local atmospheric pressure value (Patm) to avoid boiling of the fluid within the hydraulic circuit (<NUM>), said set temperature (Tfluid_set) being comprised between <NUM> and <NUM>;
characterized by the fact that the thermal disinfection procedure further comprises at least the following steps performed by the control unit (<NUM>):
- based on the determined set temperature (Tfluid_set) calculating an estimated time (Test) to completion of the thermal disinfection procedure;
- comparing the estimated time (Test) to completion of the thermal disinfection procedure with a reference time;
- based on a comparison outcome, continuing with thermal disinfection procedure or recommending/starting a different disinfection procedure, e.g., a chemical disinfection procedure.