Peritoneal dialysis circuit with reduced pH disinfection.

Abstract

The peritoneal dialysis ("PD") system includes a plurality of PD fluid components, a reusable PD fluid line in selective fluid communication with the PD fluid components, a source of PD fluid in selective fluid communication with the reusable PD fluid line, a source of anti-scaling fluid in selective fluid communication with the reusable PD fluid line, and a control unit, the control unit configured to (i) operate the plurality of PD fluid components during treatment using PD fluid from the source heated to a treatment temperature, and (ii) circulate unused PD fluid heated to a disinfection temperature in combination with anti-scaling fluid from the source of anti-scaling fluid after treatment to disinfect the plurality of PD fluid components and the reusable PD fluid line, the anti-scaling fluid being provided in an amount configured to lower the pH of the unused PD fluid to a level below which a precipitate forms and above which the pH causes disinfection.

Description

[Technical field]

[0001] The present disclosure relates generally to medical fluid therapy, and more particularly, to dialysis fluid therapy. [Background technology]

[0002] (background) Due to a variety of causes, a person's renal system can fail. Renal failure produces several physiological disorders: it is no longer possible to balance fluid and minerals or excrete the daily metabolic load. Toxic end products of metabolism such as urea, creatinine, uric acid, and others can accumulate in the patient's blood and tissues.

[0003] Reduced kidney function, especially kidney failure, is treated with dialysis, which removes waste products, toxins, and excess water from the body that normally functioning kidneys would otherwise remove. Dialysis treatment for replacement of kidney function is important for many people because the treatment is life-saving.

[0004] One type of renal failure therapy is hemodialysis ("HD"), which generally uses diffusion to remove waste products from a patient's blood. A diffusion gradient occurs across a semi-permeable dialyzer between the blood and an electrolyte solution, called the dialysate or dialysis fluid, causing diffusion.

[0005] Hemofiltration ("HF") is an alternative renal replacement therapy that relies on the convective transport of toxins from the patient's blood. HF is accomplished by adding substitute or replacement fluid to the extracorporeal circuit between treatments. The substitute fluid, and fluid accumulated by the patient between treatments, is ultrafiltered over the course of HF treatment, providing a convective transport mechanism that is particularly beneficial in removing medium and large molecules.

[0006] Hemodiafiltration ("HDF") is a treatment modality that combines convective and diffusive clearance. HDF uses dialysis fluid flowing through a dialyzer, similar to standard hemodialysis, to provide diffusive clearance. In addition, a substitute solution is provided directly to the extracorporeal circuit to provide convective clearance.

[0007] Most HD, HF, and HDF treatments are performed in a centralized facility. The trend toward home hemodialysis ("HHD") exists today, in part because HHD can provide therapeutic benefits over centralized hemodialysis treatments, which are performed daily and typically performed two or three times a week. Studies have shown that more frequent treatments remove more toxins and waste products and result in less interdialytic fluid overload than patients who receive less frequent, but perhaps longer, treatments. Patients who receive more frequent treatments do not suffer as much downcycling (fluid and toxin circulation fluctuations) as centralized patients who have accumulated two or three days' worth of toxins prior to treatment. In some areas, the nearest dialysis centralized facility may be many miles from the patient's home, resulting in door-to-door treatment times consuming a large portion of the patient's day. Treatments at centralized facilities closer to the patient's home may also consume a large portion of the patient's day. HHD can be performed at night or during the day while the patient is relaxing, working, or otherwise productive.

[0008] Another type of renal failure therapy is peritoneal dialysis ("PD"), which infuses a dialysis solution, also called dialysis fluid, into a patient's peritoneal cavity via a catheter. The dialysis fluid contacts the peritoneal membrane within the patient's peritoneal cavity. Waste, toxins, and excess water pass from the patient's bloodstream, through the capillaries in the peritoneal membrane, and into the dialysis fluid due to diffusion and osmosis, i.e., an osmotic gradient occurs across the membrane. An osmotic agent in the PD dialysis fluid provides the osmotic gradient. Spent or depleted dialysis fluid is pumped out of the patient, removing the waste, toxins, and excess water from the patient. This cycle is repeated, for example, multiple times.

[0009] There are various types of peritoneal dialysis therapies, including continuous ambulatory peritoneal dialysis ("CAPD"), automated peritoneal dialysis ("APD"), tidal peritoneal dialysis ("TPD"), and continuous flow peritoneal dialysis ("CFPD"). CAPD is a manual dialysis treatment. Here, the patient manually connects an implanted catheter to a drain, allowing used or spent dialysis fluid to drain from the peritoneal cavity. The patient then switches the fluid communication so that the patient catheter communicates with a bag of fresh PD fluid and infuses fresh PD fluid through the catheter and into the patient. The patient disconnects the catheter from the fresh PD fluid bag, allowing the dialysis fluid to dwell in the peritoneal cavity, and transfer of waste, toxins, and excess water occurs. After a dwell cycle, the patient repeats the manual dialysis procedure, for example, four times per day. Manual peritoneal dialysis requires a significant amount of time and effort from the patient and leaves ample room for improvement.

[0010] APD is similar to CAPD in that the dialysis treatment includes drain, fill, and dwell cycles. However, APD machines perform the cycles automatically, typically while the patient sleeps. APD machines relieve the patient from the need to manually perform treatment cycles and transport supplies during the day. APD machines fluidly connect to an implanted catheter, to one or more bags of fresh PD fluid, and to a fluid drain. The APD machine pumps fresh PD fluid from a dialysis fluid source, through the catheter, and into the patient's peritoneal cavity. APD machines also allow the dialysis fluid to dwell within the peritoneal compartment, allowing transfer of waste, toxins, and excess water to occur. The source may contain multiple liters of dialysis fluid, including several solution bags.

[0011] APD machines pump used or depleted dialysate from the patient's peritoneal cavity, through a catheter, and to a drain. As with the manual process, several drain, fill, and dwell cycles occur during dialysis. A "last fill" may occur at the end of an APD treatment. The last fill fluid may remain in the patient's peritoneal cavity until the start of the next treatment, or may be manually emptied at some point during the day.

[0012] In any of the above modalities using automated machines, the automated machines typically operate with disposable sets that are discarded after a single use. Depending on the complexity of the disposable set, the cost of using one set per day can be significant. Also, daily consumables require space for storage, which can be troublesome for homeowners and businesses. Also, daily disposable replacement requires daily set-up time and effort by the patient or caregiver at home or in the clinic.

[0013] For each of the above reasons, it would be desirable to provide an APD machine that reduces disposable waste. Summary of the Invention [Means for solving the problem]

[0014] (summary) Known automated peritoneal dialysis ("APD") systems typically include a machine or circulator that receives and operates a pumping cassette having a rigid portion and a flexible portion that is deformable to perform pumping and valving. The rigid portion is attached to tubing that extends to various bags. The disposable cassette and associated tubing and bags can be cumbersome for a patient at home to load for treatment. The sheer volume of disposable items can also lead to multiple set-up procedures requiring input from the patient, which can expose room for error.

[0015] The present APD system and associated methodology of the present disclosure, on the other hand, converts many of the fluid-carrying portions of the peritoneal dialysis ("PD") system into reusable components that are disinfected after treatment. Fluid lines within the machine or circulator are reused. The remaining disposable items may include a drain line leading to a drain bag or indoor drain, peritoneal dialysis fluid containers with different dextrose or glucose levels, and one or more dialysis fluid containers or bags, such as a final bag container containing icodextrin. In an embodiment, a disposable filter is placed at the distal end of the patient line to provide the final stage of PD fluid filtration prior to delivery to the patient.

[0016] The APD system of the present disclosure includes a PD circulation device having a housing. At least one, possibly three or more reusable PD fluid lines extend from the housing. When not connected to a PD fluid container or bag, the reusable PD fluid lines can be connected to a disinfectant connector supported and provided by the housing. The reusable PD fluid lines may extend from the front of the housing, for example, and connect to a disinfectant connector also provided at the front of the housing for easy access to the PD fluid lines. The reusable PD fluid lines may be color-coded and / or keyed to match the color-coded or keyed connector of the PD fluid container or bag. The container or bag may hold a final bag of dialysis fluids with different dextrose or glucose levels, such as 1.36% glucose dialysis fluid, 2.27% glucose dialysis fluid, 3.86% glucose dialysis fluid, and / or different formulations of PD fluids, such as icodextrin. The container or bag may additionally hold fluids other than PD fluids, such as nutritional fluids.

[0017] Inside the housing, reusable tubing extends from each of the reusable dialysis fluid lines through a dialysis fluid line valve for each dialysis fluid line to an in-dialysis fluid line heater. In an embodiment, each of the valves of the PD circulation device is an electrically actuated valve having a reusable valve body that either blocks (e.g., when not powered) to prevent PD fluid from flowing through the body, or allows PD fluid to flow through the body (e.g., when powered). The valves may alternatively be bi-stable valves. The PD fluid in-line heaters are also electrically actuated in one embodiment, and are resistive heaters having a reusable heater body that receives, e.g., PD fluid for heating. The in-line heaters in an embodiment are capable of heating the PD fluid from room temperature to body temperature, e.g., 37° C., at a flow rate of at least 200 milliliters ("ml") / min. A temperature sensor is located adjacent to, e.g., downstream from, the heater to provide feedback for temperature control. It is also envisioned to install a second temperature sensor upstream of the heater for feed-forward control, stabilizing and speeding up the response of the heating control. The second sensor may also provide useful information for calculating a disinfection dose value, e.g., an A0 value, for use during disinfection.

[0018] The reusable tubing, in one embodiment, extends from the outlet of the heater in the PD fluid line to the air trap. Any of the tubing inside the circulator housing may be metal, e.g., stainless steel, or plastic, e.g., polyvinyl chloride ("PVC") or non-PVC materials such as polyethylene ("PE"), cross-linked polyethylene ("PEX"), polyurethane ("PU"), polyetheretherketone ("PEEK"), or polycarbonate ("PC"). In an embodiment, one or more level sensors are located adjacent to the air trap so that a desired level or range of levels of PD fluid is maintained in the air trap. An air trap valve is located downstream from the air trap in an embodiment so that the air trap can be closed downstream to fill the air trap. The air trap may be closed upstream by a dialysis fluid line valve for drainage. A vent valve may also be provided at the top of the air trap.

[0019] A reusable PD fluid pump is located within the circulator housing and includes a reusable pump body that receives the PD fluid for pumping. That is, the pump does not require the PD fluid to flow within a disposable item such as a tube or cassette. The PD fluid pump may be an electrically operated piston, gear, membrane, or centrifugal pump that may be inherently volumetrically accurate such that a separate PD fluid volume measuring device such as a flow meter, balance chamber, or device using the ideal gas law is not required. The PD fluid pump is controllable to pump to and from the patient at or within pressure limits by controlling the level of or the rate of current to the PD fluid pump. The positive patient pressure limit may be, for example, 1 to 5 psig (e.g., 2 psig (14 kPa)). The negative patient pressure limit may be, for example, -1.0 psig to -3.0 psig (e.g., -1.3 psig (-9 kPa)). The PD fluid pump may be bidirectional or unidirectional, and a single pump may be provided. The PD fluid pump may also be continuous.

[0020] In an embodiment, a conductivity sensor is located adjacent to the PD fluid pump. The conductivity sensor may be used to detect the conductivity of the unused PD fluid to ensure that it is the prescribed type, e.g., the prescribed glucose or dextrose level. The conductivity sensor may be used to detect the conductivity of the unused PD fluid to ensure that it is mixed correctly, for example, when an on-line PD fluid source is connected to one of the reusable PD fluid lines instead of a PD fluid container. A temperature sensor is located near the conductivity sensor so that the conductivity readings can be temperature compensated.

[0021] One or more patient line valves are located between the conductivity sensor and the reusable patient line in an embodiment. The patient line valve selectively allows unused PD fluid to flow into the unused PD fluid lumen of the dual lumen reusable patient line, while the other of the parallel patient line valves selectively allows used PD fluid to flow into the used PD fluid lumen of the dual lumen reusable patient line. One or more pressure sensors are located proximate to the parallel patient line valves to allow positive and negative patient pressures to be monitored and controlled. A patient line connector extends from the PD circulator housing and receives the dual lumen reusable patient line during disinfection and generally while the patient is not receiving treatment. A disinfection line, located inside the PD circulator housing, extends from the patient line connector to at least one disinfection connector. At least one disinfection line valve is located along the disinfection line to selectively open the disinfection line to perform a disinfection sequence. The valves of the present disclosure may be two-way valves, three-way valves, or combinations thereof.

[0022] The drain line, in one embodiment, is disposable and connects to a drain line connector extending from the housing of the PD circulation device during treatment. After treatment, the drain line is removed and discarded. The drain line connector is configured to close or be closed to the outside world when the drain line is removed. The drain line connector includes a dual lumen or dialysis fluid passage that allows a disinfectant fluid, e.g., heated used PD fluid, to flow in and out of the drain line connector during disinfection. One lumen or passage of the drain line connector is placed in selective fluid communication with the PD fluid pump via a first drain line valve. The other lumen or passage of the drain line connector is placed in selective fluid communication with the disinfection line via a second valve.

[0023] In one embodiment, a spool or hose reel is located within the housing. The hose reel is configured to automatically retract the reusable patient line when the patient line is connected to the patient line connector. The spool includes a releasable lock that a user opens to allow the spool to take up the patient line. Until the lock is released or opened, the patient line remains unwound from the spool such that the spool does not pull on the reusable patient line during treatment.

[0024] An additional pressure sensor may be located on the suction side of the PD fluid pump (from a patient fill perspective) to sense the inlet negative pressure to the pump. The additional pressure sensor is also useful for detecting an empty or nearly empty PD fluid container or bag, and therefore may be used as an alternative to, or in addition to, a flow switch. The output from the additional pressure sensor may also be used in determining the volume of PD fluid pumped in a pump stroke for PD fluid pumps that rely on inlet pressure for accuracy.

[0025] The PD circulator of the disclosed PD system includes a control unit having one or more processors and one or more memories that receive signals or outputs from the pressure, temperature, conductivity, and potentially other sensors and process the signals or outputs as feedback. The control unit uses pressure feedback to control the PD fluid pump to perform at safe patient pressure limits during treatment and safe system limits during disinfection. The control unit uses temperature feedback to control the dialysis fluid heater to heat unused PD fluid, for example, to body temperature. The control unit uses temperature compensated conductivity readings to analyze unused PD fluid, for reasons discussed herein.

[0026] The control unit also opens and closes the dialysis fluid valves in combination with the PD fluid pump and heater to perform a priming sequence, a patient fill sequence, a patient drain sequence, and a disinfection sequence after the PD treatment, with the at least one reusable PD fluid line each connected to one of the at least one disinfection connectors and the reusable patient line connected to the reusable patient line connector. The disinfection sequence prepares the PD circulation device for the next treatment. In an embodiment, unused, unused PD fluid is heated after the final drain and used for disinfection.

[0027] If the unused PD fluid does not contain bicarbonate, the PD fluid will not form precipitates or scaling even when heated for disinfection. However, using unused unused PD fluids containing bicarbonate for disinfection presents a risk of forming precipitates, especially when the fluid is heated for disinfection. Precipitates such as magnesium carbonate (MgCO3) and calcium carbonate (CaCO3) may form because the precipitates have reversed solubility at elevated disinfection temperatures and with increased pH. When the unused PD fluid used for disinfection contains bicarbonate, dissolved carbon dioxide (CO2) gas is less soluble and tends to evaporate, which has the effect of increasing the pH of the solution.

[0028] To avoid precipitation, which may cause PD fluid pumps to malfunction (e.g., become clogged or become slow to respond), among other consequences, the PD system of the present disclosure injects a small amount of acid, such as citric acid, into the PD disinfectant fluid. The small amount of acid lowers the pH of the unused, virgin PD fluid, for example, to pH 6.5 or below, such as to pH 4-6 or 2-6. In certain embodiments, the pH reduction is performed only during disinfection and not during treatment, so that the patient receives the prescribed PD fluid during treatment.

[0029] Lowering the pH significantly minimizes the risk of forming precipitate or scaling. The pH level of the PD fluid is the primary chemical factor for causing precipitation. While citric acid is used in one embodiment, the anti-scaling fluid or acid may alternatively include hydrochloric acid (HCl), white vinegar, ascorbic acid (e.g., at disinfection temperatures below 85°C), acetic acid, lactic acid, other suitable acids, and mixtures of acids such as those listed above. The addition of anti-scaling fluid or acid may be added to the unused PD fluid immediately prior to and / or during disinfection. It is envisioned that the circulation device of the disclosed system (i) includes a reusable container that holds the anti-scaling fluid or acid, (ii) determines whether the PD fluid to be used for disinfection contains bicarbonate, and (iii) uses the anti-scaling fluid to prevent the formation of precipitate or scaling, if applicable. Because the pH only needs to be lowered to about 6.5, or slightly below that, such as to pH 4-6 or 2-6, the container can be of compact size and still hold a large amount of anti-scaling fluid or acid for many treatments. Reducing the pH to 2 or 2.5, as is typical for disinfection, would require more acid and therefore a larger container.

[0030] In a first aspect of the present disclosure, which may be combined with any other aspect or portion thereof without limiting the present disclosure in any way in light of the disclosure described herein, a peritoneal dialysis ("PD") system includes a housing, a plurality of PD fluid components housed by the housing, at least one reusable PD fluid line in fluid communication with the plurality of PD fluid components, a source of PD fluid in valved fluid communication with the at least one reusable PD fluid line, a source of anti-scaling fluid in valved fluid communication with the at least one reusable PD fluid line, and a control unit, the control unit configured to: (i) receive a PD fluid from the source of PD fluid; The method is configured to: (i) use the D fluid to operate a plurality of PD fluid components during treatment, wherein the PD fluid is heated to a treatment temperature; and (ii) circulate unused PD fluid heated to a disinfection temperature after treatment in combination with an anti-scaling fluid from a source of the anti-scaling fluid to disinfect the plurality of PD fluid components and at least one reusable PD fluid line, wherein the anti-scaling fluid is provided in an amount configured to lower a pH of the unused PD fluid to a level below which a precipitate forms and at or above a pH of 4.

[0031] In a second aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after treatment and prior to heating the unused PD fluid to a disinfecting temperature.

[0032] In a third aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after treatment while heating the unused PD fluid to a disinfecting temperature.

[0033] In a fourth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after heating the unused PD fluid to a disinfection temperature.

[0034] In a fifth aspect of the present disclosure, which may be used in conjunction with any other aspect or portion thereof, the anti-scaling fluid is an acid, such as citric acid.

[0035] In a sixth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, the treatment temperature is about 37°C and the disinfection temperature is between 70°C and 95°C.

[0036] In a seventh aspect of the present disclosure, which may be used in conjunction with any other aspect or portion thereof, the pH of the unused PD fluid prior to reduction is at least greater than 6.5, such as 8.0.

[0037] In an eighth aspect of the disclosure, which may be used in combination with any other aspect or portion thereof, the reduced pH level is 6.5 or slightly below.

[0038] In a ninth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, the plurality of PD fluid components includes a PD fluid pump, and the control unit is configured to operate the pump to pump the PD fluid and the anti-scaling fluid.

[0039] In a tenth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, the plurality of PD fluid components includes a PD fluid heater, and the control unit is configured to operate the PD fluid heater to heat the PD fluid to a therapeutic temperature and the unused PD fluid to a disinfection temperature.

[0040] In an eleventh aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, a PD system includes a valve under the control of a control unit and a redundant valve, the valve and the redundant valve providing valved fluid communication between a source of anti-scaling fluid and at least one reusable PD fluid line.

[0041] In a twelfth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, a peritoneal dialysis ("PD") system includes a plurality of PD fluid components, at least one reusable PD fluid line in fluid communication with the plurality of PD fluid components, a source of PD fluid in valved fluid communication with the at least one reusable PD fluid line, a source of anti-scaling fluid in valved fluid communication with the at least one reusable PD fluid line, and a control unit, the control unit configured to (i) operate the plurality of PD fluid components during treatment using PD fluid from the source of PD fluid, where the PD fluid is heated to a treatment temperature, (ii) determine whether unused PD fluid from the source to be used for disinfection contains bicarbonate, and (iii) if the unused PD fluid from the source to be used for disinfection contains bicarbonate, circulate the unused PD fluid heated to the disinfection temperature after treatment in combination with the anti-scaling fluid from the source of anti-scaling fluid to disinfect the plurality of PD fluid components and the at least one reusable PD fluid line.

[0042] In a thirteenth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, in the PD system of the twelfth aspect, (ii) occurs before or after (i).

[0043] In a fourteenth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, the anti-scaling fluid is provided in an amount configured to lower the pH of the unused PD fluid to a level below which a precipitate forms and above which the pH causes disinfection.

[0044] In a fifteenth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after treatment and prior to heating the unused PD fluid to a disinfection temperature.

[0045] In a sixteenth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after treatment while heating the unused PD fluid to a disinfection temperature.

[0046] In a seventeenth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after heating the unused PD fluid to a disinfection temperature.

[0047] In an eighteenth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, the control unit is further configured such that if the unused PD fluid from the source to be used for disinfection does not contain bicarbonate, the unused PD fluid heated to the disinfection temperature after treatment is circulated without combining with the anti-scaling fluid to disinfect the plurality of PD fluid components and the at least one reusable PD fluid line.

[0048] In a nineteenth aspect of the present disclosure, which may be used in combination with any other aspect or portion thereof, determining whether unused PD fluid from a source to be used for disinfection contains bicarbonate includes determining a type of PD fluid to be used for disinfection.

[0049] In light of the above aspects and the disclosure herein, it is an advantage of the present disclosure to provide an automated peritoneal dialysis ("APD") circulatory device that reuses many components that may otherwise be disposable, lowering the cost of treatment.

[0050] It is another advantage of the present disclosure to provide a PD circulation device having fluid handling components that receive peritoneal dialysis fluid directly without the need to work with disposable items such as tubing or flexible sheeting, reducing user interaction.

[0051] It is a further advantage of the present disclosure to provide a PD circulation device that uses unused treatment fluid during disinfection while avoiding enhanced precipitation or scaling.

[0052] It is yet another advantage of the present disclosure that it provides disinfection using disinfectant fluids already available.

[0053] It is yet a further advantage of the present disclosure to automatically dose anti-scaling fluid or acid.

[0054] It is yet another advantage of the present disclosure to provide an anti-scaling or settling form that uses a small amount of anti-scaling fluid such that a relatively small container of fluid lasts for many treatments.

[0055] It is yet a further advantage of the present disclosure to provide an anti-scaling fluid or acid that removes precipitate or scaling that forms during treatment while the PD fluid is at treatment fluid temperature.

[0056] Additional features and advantages will be described in and become apparent from the following detailed description and figures. The features and advantages described herein are not exhaustive, and many additional features and advantages will become apparent to those skilled in the art in view of the figures and description. Also, it is not necessary for any particular embodiment to have all of the advantages enumerated herein, and it is expressly contemplated that each advantageous embodiment may be separately claimed. It should also be noted that the language used in this specification has been selected primarily for readability and instructional purposes, and not to limit the scope of the subject matter of the present invention. [Brief description of the drawings]

[0057] [Figure 1] FIG. 1 is a perspective view of one embodiment of an endovascular device ("APD") and associated system of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] (Detailed Description) (PD Fluid System) Referring now to the drawings, and in particular to FIG. 1, the presently disclosed peritoneal dialysis ("PD") system 10 and associated methodology includes a PD machine or circulator 20. The system 10 and circulator 20 attempt to eliminate as many disposable items as possible, and instead provide most of its fluid carrying parts as reusable components that are disinfected after treatment. The fluid lines within the machine or circulator are reused. In particular, FIG. 1 illustrates that the circulator 20 includes a housing 22 from which reusable peritoneal dialysis ("PD") fluid lines 24a-24c extend from an opening 26 defined or provided by the housing. The opening 26 may be grommeted or otherwise sealed so that dust, fluids, and other substances cannot enter the housing 22 from the environment. FIG. 1 further illustrates that a reusable patient line 28 also extends from the housing 22 of the circulator 20 through a sealed opening, e.g., grommeted. As discussed in detail below, the reusable patient line 28, which is typically longer than the reusable PD fluid lines 24a-24c, may be wound or spooled within the housing via a spool or hose reel 110 when the reusable patient line 28 is not connected to a patient for treatment.

[0059] When not connected to a PD fluid container or bag, the reusable PD fluid lines 24a-24c and the patient line 28 can be connected to dedicated connectors supported and provided by the housing. The reusable PD fluid and patient lines may, for example, extend from the front of the housing and connect to connectors also provided at the front of the housing for easy access to the PD fluid and patient lines. In the illustrated embodiment, the distal ends 24d of the reusable PD fluid lines 24a-24c are releasably attached in a fluid-tight manner to disinfectant connectors 30a-30c, respectively, provided in the housing 22. The distal end 28d of the reusable patient line 28 is releasably attached in a fluid-tight manner to a patient line connector 32, provided in the housing 22. The disinfectant connectors 30a-30c and the patient line connector 32 are configured, in one embodiment, to automatically close or close when the reusable PD fluid lines 24a-24c and the reusable patient line 28, respectively, are not connected to the connectors.

[0060] 1 also illustrates that the housing 22 provides a drain line connector 34 that may be releasably covered by a movable, e.g., rotatable or slidable, cover. The drain line connector 34 receives a disposable drain line 36 for treatment that may run to a drain container or bag or to an indoor drain. In an alternative embodiment, the drain line 36 is reusable and is connected to a disinfection loop as discussed herein.

[0061] Although not shown in FIG. 1, the system 10 also includes disposable PD fluid or solution containers or bags for connection to the reusable PD fluid lines 24a-24c. The distal ends 24d of the reusable PD fluid lines 24a-24c may be color coded and / or keyed to match color coded or keyed connectors of dedicated PD fluid containers or bags. The containers or bags may hold dialysis fluids with different dextrose or glucose levels, such as 1.36% glucose dialysis fluid, 2.27% glucose dialysis fluid, 3.86% glucose dialysis fluid, and / or different formulations of PD fluid, e.g., icodextrin, etc., at the end of the bag. It is also possible that the PD fluid containers or bags may hold glucose levels between the glucose levels approved by regulatory agencies, e.g., 1.36% glucose to 3.86% glucose.

[0062] It should be understood that any number of reusable PD fluid lines and PD fluid containers or bags may be provided, including a single reusable PD fluid line and PD fluid container, or more than one reusable PD fluid line and PD fluid container. In a further alternative embodiment, the PD fluid container or bag is replaced by an on-line PD fluid source that connects to and is in fluid communication with the single reusable PD fluid line. System 10 may also be configured to operate with either a pre-filled PD fluid container or bag or an on-line PD fluid source.

[0063] It is envisioned that any of the reusable PD fluid lines 24a-24c, reusable patient lines 28, disinfectant connectors 30a-30c, patient line connector 32, drain line connector 34, and drain line 36 are made from any one or more plastics, such as polyvinyl chloride ("PVC") or non-PVC materials, such as polyethylene ("PE"), polyurethane ("PU"), polyetheretherketone ("PEEK"), or polycarbonate ("PC"). Some of the components, such as disinfectant connectors 30a-30c, may be made from, for example, stainless steel or titanium.

[0064] 1, circulation system 20 includes reusable tubing 52a extending from each reusable PD fluid line 24a-24c, through PD fluid line valves 54a-54c, respectively, to a PD in-fluid line heater 56. Valves 54b and 54c are in fluid and selective communication with reusable tubing 52a via three-way valve 154a.

[0065] In an embodiment, the valves of the PD circulation device, including the PD fluid line valves 54a-54c, the three-way valve 154a, and all other valves discussed herein, are each electrically actuated valves with a reusable valve body that either closes to prevent PD fluid from flowing through the body (e.g., when not powered for fail-safe operation) or allows PD fluid to flow through the body (e.g., when powered). The PD fluid in-line heater 56, in one embodiment, is also electrically actuated and is a resistive heater with a reusable heater body that receives PD fluid, e.g., for treatment and disinfection heating. The in-line heater 56 in an embodiment is capable of heating the PD fluid from room temperature or lower (e.g., when the PD fluid is stored in a cold environment) to body temperature, e.g., 37° C., at a flow rate of at least 200 milliliters (ml) / min (lower flow rates can also be achieved, e.g., for children or infants). A temperature sensor 58a is located adjacent to, e.g., downstream from, the heater 56 to provide feedback for temperature control. If desired, a second temperature sensor (not shown) may be provided upstream from the heater 56 to allow the inlet temperature of the unused PD fluid to be taken into account with respect to the heating algorithm or routine, i.e., to provide feed-forward control that stabilizes and speeds up the responsiveness of the overall heating control. The second sensor may also provide useful information for calculating a disinfection dosage value, e.g., an A0 value, for use during disinfection.

[0066] The reusable tubing 52b extends from the outlet of the PD fluid in-line heater 56 to the air trap 60 in the illustrated embodiment of FIG. 2. Any of the reusable tubing inside the housing of the circulator 20, including the reusable tubes 52a and 52b, may be made from metal, e.g., stainless steel, or plastic, e.g., silicone, polyvinyl chloride ("PVC") or non-PVC materials such as polyethylene ("PE"), polyurethane ("PU"), polyetheretherketone ("PEEK"), or polycarbonate ("PC"). In an embodiment, one or more level sensors 62a and 62b are located adjacent to the air trap 60 such that a desired level or range of levels of PD fluid is maintained within the air trap. A vent valve 54v is provided at the top of the air trap 60 to allow air and / or carbon dioxide to be vented from the air trap during filling and to enter the air trap during draining. Although not shown, the vent valve 54v may include or operate in conjunction with a vent filter, e.g., a hydrophobic filter, to prevent dialysis fluid from escaping when the vent valve 54v opens and to sterile filter air entering the air trap 60 to avoid contamination. The vent valve 54v may also be opened to allow the level of dialysis fluid in the air trap 60 to be adjusted.

[0067] The reusable tubing 52c extends between the air trap valve 54d and a PD fluid pump 70 located within the housing 22 of the circulator 20. The PD fluid pump 70 in one embodiment includes a reusable pump body that receives the PD fluid for pumping. That is, the pump 70 does not require the PD fluid to flow within a disposable item such as a tube or cassette. The reusable pump body of the pump 70 itself receives the PD fluid. The PD fluid pump 70 may be of a type that is inherently volumetrically accurate so that a separate PD fluid volume measuring device such as a flow meter, balance chamber, or device using the ideal gas law is not required. The PD fluid pump 70 may be an electrically operated piston or membrane pump. The PD fluid pump 70 may alternatively be a less accurate gear or centrifugal pump that does not operate with a separate PD fluid volume measuring device. The PD fluid pump 70 is controllable to pump to and from the patient at or within the pressure limits by controlling the level of current to the PD fluid pump. The positive patient pressure limit may be, for example, 1 to 5 psig (e.g., 2 psig (14 kPa)). The negative patient pressure limit may be, for example, -1.0 psig to -3.0 psig (e.g., -1.3 psig (-9 kPa)). The pump 70 is also capable of providing lower magnitude pressures if needed, for example, for small children or infants. The PD fluid pump 70 is bidirectional and continuous in one embodiment, such that a single pump may be provided and used to pump the anti-scaling fluids discussed herein.

[0068] In the illustrated embodiment of FIG. 1, a conductivity sensor 74 is located along the reusable line or tubing 52d adjacent to the PD fluid pump 70. The conductivity sensor 74 is used to detect the conductivity of the unused PD fluid to ensure that it is the prescribed type, e.g., the prescribed glucose or dextrose level. The conductivity sensor 74 may alternatively or additionally be used to detect the conductivity of the unused PD fluid to ensure that it is properly mixed, for example, if an on-line PD fluid source is instead connected to one of the reusable PD fluid lines 24a-24c. A temperature sensor 58b is located proximate the conductivity sensor 74 in the illustrated embodiment so that the conductivity readings from the sensor may be temperature compensated.

[0069] 1 further illustrates that the reusable line or tubing 52d extends to a second three-way valve 154b that is toggled differently depending on whether fresh or used PD fluid is being pumped. In one toggled state, the three-way valve 154b allows fresh PD fluid to be pumped to the patient through the reusable fresh PD fluid line 52f and the fresh PD fluid lumen of the dual lumen reusable patient line 28. In a second toggled state, the three-way valve 154b allows used PD fluid to be pumped from the patient through the used PD fluid lumen of the dual lumen reusable patient line 28 and through the reusable used PD fluid line 52u. A first pressure sensor 78a is located along the reusable line or tubing 52d to allow the positive fresh PD fluid fill pressure to be monitored and controlled.

[0070] A second pressure sensor 78b is located along or in fluid communication with the spent PD fluid line 52u to allow the negative spent PD fluid drain pressure to be monitored and controlled. The first pressure sensor 78a may also be used to measure the spent PD fluid drain pressure, for example, for redundancy and increased accuracy. A reusable drain line 52e extends from the reusable tubing or line 52c to the drain line connector 34 to deliver spent PD fluid pumped by the PD fluid pump 70 running in reverse to the drain line 36. A drain line valve 54e is located along the reusable drain line 52e.

[0071] A reusable sanitizing tube or line 52f is located inside the housing 22 of the PD circulation device 20, extends from the used PD fluid line 52u, and branches into reusable sanitizing line branches 52f1 and 52f2 at a valve 54f. The reusable sanitizing line branch 52f1 extends to a T-junction in fluid communication with the PD fluid line valve 54a. A sanitizing line branch valve 54f1 is located along the reusable sanitizing line branch 52f1 for sanitizing fluid control through the line. The reusable sanitizing line branch 52f2 extends to form a vent line to atmosphere, controlled by the sanitizing line branch valve 54f2. If a vent valve 54e is provided in the air trap 60, the reusable sanitizing line branch 52f2 may instead extend to an upper portion of the air trap. In some embodiments, the reusable sanitizing line branch 52f2 and the sanitizing line branch valve 54f2 are omitted.

[0072] A recirculation line 52g also extends from the reusable disinfection line branch 52f2. The recirculation line 52g extends to the drain line connector 34. The two reusable lines 52e and 52g, which extend to the drain line connector 34, allow disinfection fluid to be recirculated through the drain line connector 34 during disinfection, for example, with the disinfection line branch valve 54f2 closed and the disposable drain line 36 removed. Similarly, the patient line connector 32 extends from the PD circulator housing and receives the dual lumen reusable patient line 28 during disinfection, and generally while the patient is not receiving treatment. The patient line connector 32 includes an internal U-turn or 180° turn to allow disinfection fluid to flow from one of the dual lumens of the dual lumen patient line to the other of the dual lumens during disinfection.

[0073] The circulation device 20 includes an additional reusable sanitizing line 52h that extends from one leg of the three-way valve 154a to the sanitizing connector 30c. A further reusable sanitizing line 52i extends from the sanitizing connector 30b to the sanitizing connector 30a. A sanitizing connector valve 54i is located along the reusable sanitizing line 52i to selectively allow flow of sanitizing fluid between the sanitizing connectors 30a and 30b during sanitizing.

[0074] Reusable PD fluid lines 24a-24c connected to disinfection connectors 30a-30c, respectively, reusable line or tubing 52a, reusable body of PD fluid line heater 56, reusable line or tubing 52b, reusable air trap 60, reusable line or tubing 52c, reusable pump body of PD fluid pump 70, reusable line or tubing 52d including conductivity sensor 74, reusable tubing or lines 52f and 52u, reusable dual lumen patient line 28 connected to patient line connector 32, crowned drain line connector 34, and disinfection lines 52f, 52f1, 52f2, 52g, 52h, and 52i together form a disinfection loop 50 that allows disinfection fluid, e.g., heated used PD fluid, to contact all internal reused surfaces continuously over a timed disinfection sequence to provide proper disinfection.

[0075] In the illustrated embodiment, the circulator 20 of the system 10 further includes an anti-scaling fluid or citric acid source 40 placed in selective fluid communication with the disinfection line 52h via a citrate line 52j and a valve 54j located along the citrate line. In the illustrated embodiment, the three-way valve 154a is toggled to close toward the citrate source 40 during treatment, providing a second protective valve that additionally ensures that no anti-scaling fluid, e.g., citric acid, leaks into the treatment fluid path of the circulator 20 during treatment. Also, view FIG. 1 to understand that during treatment, the reusable PD fluid line 24c is disconnected from the disinfection connector 30c such that no anti-scaling fluid can enter the treatment fluid path of the circulator 20 via the disinfection connector 30c and the reusable PD fluid line 24c, even if the citrate valve 54j leaks. The anti-scaling fluid or citric acid source 40 may be located in an alternate location relative to the disinfection loop 50, however, it is important in one embodiment to have redundant valves between the source 40 and any lines or components used during treatment.

[0076] It is possible that the PD fluid pump 70 is precise enough to handle the very small amounts of citric acid metered into the disinfection loop 50 at a given time. Although not shown, if needed, a small, precise citric acid metering pump may be located along the citric acid line 52j to meter precise amounts of citric acid into the disinfection loop 50 as discussed in detail herein. The citric acid metering pump may be, for example, a small piston pump. Although citric acid is used in one embodiment, the anti-scaling fluid or acid may alternatively include hydrochloric acid (HCl), white vinegar, ascorbic acid (e.g., at disinfection temperatures below 85° C.), acetic acid, lactic acid, other suitable acids, and mixtures of acids such as those listed above. It should also be understood that the disinfection loop 50 may be configured in many different ways with different valve arrangements, different components, and the like. However, each different configuration will likely provide an anti-scaling fluid source 40 and possibly an associated anti-scaling fluid metering pump. The anti-scaling fluid source 40 may be sized to hold, for example, 1 liter of anti-scaling fluid, which is sized to be used over many treatments, such as 500 daily treatments as shown below.

[0077] FIG. 1 further illustrates that the PD circulation device 20 of the system 10 of the present disclosure includes a control unit 100 having one or more processors 102 and one or more memories 104 that receive, store, and process signals or outputs from pressure sensors 78a and 78b, temperature sensors 58a and 58b, conductivity sensor 74, and other sensors or switches, such as a flow switch to ensure flow to power in-line heater 74. The control unit 100 uses pressure feedback and controls dialysis fluid pump 70 to pump unused and used PD fluid at safe patient and system pressure limits. In an embodiment, the control unit keeps track of the amount of unused or used PD fluid and its associated flow rate by counting and accumulating pump strokes of known volume. The control unit 100 will also control an anti-scaling fluid metering pump, if provided, that may run open loop when the metering pump is inherently accurate and the volume of anti-scaling fluid is likely known. Control unit 100 uses temperature feedback to control in-line dialysis fluid heater 56 to heat the unused PD fluid, e.g., to body temperature, and to heat the disinfectant fluid to a desired disinfection temperature, e.g., 70° C.-95° C. Control unit 100 analyzes the unused PD fluid to ensure it is of the prescribed type or glucose level, e.g., using temperature compensated conductivity readings. Control unit 100 also opens and closes dialysis fluid valves 54a-54f, 54f1, 54f2, 54h, and 54j in combination with operation of dialysis fluid pump 70 and heater 56 to perform a priming sequence, multiple patient fill sequences, multiple patient drain sequences, and a disinfection sequence after PD treatment.

[0078] The control unit 100 may also include a video controller 106 that interfaces with a user interface 108, which may include a display screen that operates in conjunction with one or more electromechanical buttons, such as a touch screen and / or membrane switches. The user interface 108 may also include one or more speakers for outputting alarms, alerts, and / or voice guidance commands. The user interface 108 may comprise the circulation device 20 as illustrated in FIG. 1 and / or may be a remote user interface that operates in conjunction with the control unit 100. The control unit 100 may also include a transceiver (not shown) and a wired or wireless connection to a network, e.g., the Internet, to transmit treatment data to and receive prescription instructions from a physician's or clinician's server that interfaces with the physician's or clinician's computer.

[0079] (Disinfection by injecting anti-scaling fluid (e.g., citric acid)) As mentioned above, in the disinfection sequence, each reusable PD fluid line 24a-24c is connected to a disinfection connector 30a-30c, respectively, the reusable patient line 28 is connected to the reusable patient line connector 32a, and the drain line connector 34 is covered or capped by a cover. The disinfection sequence prepares the PD circulator 20 for the next treatment. In an embodiment, unused PD fluid is heated after the final drain of the treatment and used as the disinfection fluid for disinfection. There are several benefits to using unused PD fluid as the disinfection fluid. First, for example, the PD fluid is already available, and therefore no separate water connection is required, and no extra patient step is required to connect to a separate disinfection fluid source. The unused PD fluid is also sterile.

[0080] It is envisioned that the control unit 100 keeps track of the type of unused PD fluid being used for treatment and the type of PD fluid being used for disinfection. The control unit 100 may also be programmed to keep track of PD fluids that contain bicarbonate and those that do not. The control unit 100 can thus determine whether to add citric acid in accordance with the present disclosure based on whether the PD fluid to be used for disinfection contains bicarbonate. If the PD fluid to be used for disinfection contains bicarbonate, the control unit 100 causes citric acid or other anti-scaling fluid to be dispensed into the unused unused PD in the manner discussed herein. If the PD fluid to be used for disinfection does not contain bicarbonate, the control unit 100 does not cause the anti-scaling fluid to be dispensed, in which case the anti-scaling fluid in the source or container 40 is preserved.

[0081] One obstacle to using virgin PD fluid containing bicarbonate as a disinfectant fluid is that the PD fluid may contain substances and ions such as calcium, magnesium, sodium, potassium, chloride, acetate, lactate, bicarbonate, and possibly other substances. Such substances may form scale on critical parts of the disinfection loop 50, for example, inside the PD fluid pump 70. The most commonly formed scale and precipitate is from calcium carbonate (CaCO3) because it has inverse solubility with respect to temperature. The pH of PD fluids that may be used for disinfection is likely to be higher than 6.5 and may be higher than 8.0 according to EUROPEAN PHARMACOPOEIA 9.6 (01 / 2019:0862). PD fluids containing bicarbonate at this high pH will rapidly precipitate / scale as their temperature is increased by the in-line heater 56. There is a need to adjust the PD fluids used for thermal disinfection accordingly. The system 10 of the present disclosure in an embodiment adds a relatively small amount, e.g., a few drops of citric acid or other anti-scaling fluid, into the PD fluid flowing through the disinfection loop 50 during thermal disinfection, perhaps just prior to heating the PD fluid for disinfection. The pH is not lowered using citric acid to a level that would aid in disinfection. Instead, the pH drop is to a level that avoids scaling and precipitation, e.g., to about pH 6.5, or below, such as pH 4-6 or 2-6. At pH within such ranges, calcium (up to 1.75 mM), magnesium (up to 0.25 mM), and carbonate solutions remain stable even at elevated disinfection temperatures.

[0082] If citric acid is used as the anti-scaling fluid in the source or container 40, it acts as a complex binder that lowers the pH of the disinfecting fluid (as an acid it releases one or more protons) and also reduces the risk of calcium and magnesium carbonate precipitation by creating a water soluble complex with calcium and magnesium (via the citrate ion). Anti-scaling agents, such as citric acid, may also remove precipitation or scaling that occurs during treatment while the unused PD fluid is at body temperature or 37°C. Reaction 1 shows the reaction for how acid (H+) reacts with CaCO3. Reaction 1: CaCO3(s)+2[H+](aq)=>[Ca2+](aq)+CO2(aq)+H2O(l)

[0083] To reach a desired pH of 6.5 or lower, such as pH 4-6 or 2-6, the L'Angelier Saturation Index ("LSI") was used for system 10. The LSI was calculated and used to predict when risk for system 10 of forming precipitate / scale would occur. For the calculation, Physioneal TM A worst case scenario was used in which a bicarbonate-containing PD fluid commercially available as P35 was modeled. The solution yielded the following input data: A conductivity of 12 msec / cm (higher conductivity gives better results, therefore 12 msec / cm is assumed to be the worst case), Bicarbonate concentration (HCO3), 25mmol / L+5%=26.25mmol / L; Calcium concentration (Ca), 1.75mmol / L+5%=1.84mmol / L; Lactate concentration (CH3CH(OH)COO - ) 10mmol / L-5%=9.5mmol / L, Disinfection temperature of 79°C, and pH variable (range investigated) → pH from 6.3 to 7 (pH was varied fixing the worst case parameters listed above to understand the effect of pH behavior, and the results are listed in Table 2 below).

[0084] Table 1 shows the virgin PD fluids tested (Physioneal TM P35) are shown as additional input data. Table 2 shows the output from the calculations. [Table 1] [Table 2]

[0085] Table 2 illustrates that the LSI calculation calls for only calcium and not magnesium. However, as explained herein, both calcium and magnesium found in PD fluids will form precipitate / scale in the presence of carbonate. However, when calcium and magnesium are both in solution at the same time, there is a competition between them for carbonate ions. Thus, calling only calcium in the calculation here is a worst-case approach. Notably, the solubility of magnesium carbonate is higher than calcium carbonate, i.e., 0.1 g / l vs. 0.00015 g / l, and therefore, if calcium carbonate is formed, it will begin to form a precipitate quickly. Table 2 also illustrates that a pH of 6.5 is the highest pH and requires the least amount of anti-scaling fluid, e.g., citric acid, to result in a solution that does not form scale or precipitate. Lower pHs, such as pH 4-6 or 2-6, are also suitable for the system 10.

[0086] The amount of citric acid required to achieve a pH of 6.5 is calculated as follows: Assuming again a virgin PD fluid used for disinfection (see Table 1 for input data) having an ionic strength of 140 mmol / L and a sodium bicarbonate concentration of 26.25 mmol / L (i.e., +5%), a lactate concentration of 9.5 mmol / L (i.e., -5%), and a pH higher than 6.5, such as 8.0 or higher (maximum upper limit by drug type), the PD fluid would require the addition of approximately 0.0034 mol / L of citric acid to reach a pH of 6.5 (see Table 3).

[0087] Also, assuming a total internal volume for the disinfection loop 50 of 300 ml (can be more or less), the volume required for 10 wt% liquid citric acid (10 wt% citric acid=104 g citric acid and 937 grams RO water for 1 liter) is 1.7 ml (C concentrate, 0.54mol / L ×V concentrate =C fluid path, 0.003mol / l ×V fluid path, 300ml ). 10 wt% citric acid is chosen because it does not require any safety equipment for the patient. That is, a patient can easily handle the 10 wt% citric acid concentration, e.g., replace its container 40, without fear of harm from being contacted by such a solution. However, it should be understood that more concentrated citric acid, e.g., even up to 50 wt% or more (55%), could instead be used to provide antimicrobial effects, with the container 40 and its replacement being configured to mitigate against patient or user contact with the citric acid. A higher concentration of citric acid would reduce the volume of citric acid required, allowing the container 40 to be smaller.

[0088] Assuming the container 40 holds a volume of 1 liter of 10 wt% liquid citric acid, assuming 2 ml per treatment, and assuming daily treatments / cleaning, the container 40 will last for 500 treatments / 500 days. The assumption of using 2 ml of citric acid per treatment is based on a PD disinfectant fluid having an ionic strength of 140 mmol / l and a sodium bicarbonate concentration of 26.25 mmol / l, a lactate concentration of 9.5 mmol / L, and a normal (without the addition of anti-scaling fluid) pH of 8, which would require the addition of approximately 0.0034 mol / L of citric acid to reach a pH of 6.5 (see Table 3). The volume of 10 wt% citric acid would then be approximately 2 ml.

[0089] Table 3 shows the resulting pH for calculations performed for the addition of citric acid to the worst case scenario set of inputs described above. [Table 3] Table 3 shows that molarities at or between 3.00E-03M and 4.00E-03 lead to a resultant disinfectant PD fluid pH of 6.5 or slightly lower. Therefore, to determine the amount of citric acid needed per treatment, the 0.0034 mol / L citric acid mentioned above is used.

[0090] The control unit 100 in one embodiment sends a message to a central location when it determines that the citric acid or other anti-scaling fluid in the container 40 is low so that new citric acid can be ordered and delivered. The user interface 108 may also provide an audio, visual, or audiovisual message to the patient that the anti-scaling fluid is low but that a new supply will arrive shortly. In response to receiving the new supply, the user interface 108 may also provide audio, visual, or audiovisual instructions to the patient on how to transfer the new supply into the reusable container 40 or replace the reusable container 40 with a new container.

[0091] Any acid used for the anti-scaling fluid will generate carbon dioxide (CO2) gas due to the reaction between the bicarbonate and the acid. Maintaining a higher pH will generate less CO2 gas, allowing pressure developments, e.g., spikes, to be more gradual and the system 10 to be more robust. It is envisioned that the use of a higher pH fluid during thermal disinfection will allow the material compliance of the disinfection loop 50 to withstand increased pressures. The air trap 60 and vent valve 54v may also help accommodate the production of CO2 gas.

[0092] The system 10 takes into account pressure build-up due to the production of CO2 gas, for example, because the increased pressure can affect the performance of the PD fluid pump 70, e.g., a piston pump. There are two main chemical reactions that form CO2 gas within the disinfection loop 50. Reaction 2 below occurs between bicarbonate and citric acid (C6H8O7). Reaction 3 below between calcium carbonate (CaCO3) and citric acid is likely to occur only to a minor extent. Reaction 2 is the dominant reaction, which is very rapid and the only one considered for CO2 gas pressure boost analysis. In reaction 2, the amount of citric acid (three acidic protons) is greater than that of bicarbonate, as the concentration of citric acid is lower (e.g., citric acid:bicarbonate (3×3×10 -3 :0.02625)), it is consumed. Reaction 2: C6H8O7(aq)+3NaHCO3(aq)→3H2O(l)+Na3C6H5O7(aq)+3CO2(aq) Reaction 3:3CaCO3+2C6H8O7→3H2O(l)+Ca3(C6H5O7)2+3CO2(aq)+3H2O(l)

[0093] When assessing the effect of CO2 gas formation, the volume increase due to gas formation is calculated. Here, the ideal gas law (PV=nRT) is applied. For ambient conditions, At temperature (T) = 298.15 K and thermal disinfection temperature (273.15 + 85 = 358.15 K, which is a common temperature used during thermal disinfection), Pressure (P) = 101,325 Pa, Number of moles = n, i.e., 3 x 3 x 10 of this system -3 x 0.3 (0.3 L volume) of disinfection loop 50 moles of citrate protons = 0.0027 moles (or H2CO3, 8.461 x 10 -3 mol / L×0.3L=0.0025mol) (H2CO3 is not stable, CO2+2H + ), and R = Universal gas constant, 8.134 m 3 ·Pa·K -1 mol -1 . Applying the ideal gas law, 2.5 mmol of CO2 gas will create pressure against the compliance of the disinfection loop 50 (e.g., flexibility of the fluid paths), resulting in the following additional volume being required, assuming all of the CO2 formed is in the gas phase (at high temperatures, such as disinfection, most of the CO2(aq) (dissolved) will become CO2(g)): At room temperature: V = 0.0025 × 8.314 × (298.15) / 101,325 = 6.6 × 10 -5 m 3 =66ml. At disinfection temperature: V = 0.0025 × 8.314 × (358.15) / 101,325 = 7.9 × 10 -5 m 3 =79ml. A portion of the 79 ml of CO2 generation (it should be understood that this is a worst case scenario) may be vented through valve 54v and / or delivered to a drain, with drain line 36 attached during the initial portion of the disinfection sequence when antiscaling fluid or citric acid is added and CO2 is generated. The CO2 does not need to be completely vented, but only managed so that the corresponding pressure increase is limited. For comparison, citric acid used for disinfection typically requires a solution pH of 2.5. Using (i) a concentration for citric acid required to achieve a solution pH of 2.5 (citric acid 0.465 mol / l, see Table 3), (ii) a concentration of carbonic acid (H2CO3) of 0.02624 mol / L, and (iii) a heated disinfection fluid temperature results in an extra volume of V=0.02624×0.3×8.314×(358.15) / 101,325=230 ml required for the generation of CO2 gas. The extra volume required for a solution pH of 2.5 is correspondingly about three times that of a solution pH of about 6.5 used in the present application. Using a lower pH for the system 10 of the present disclosure, such as 4-6 or 2-6, will produce more CO2, but still significantly less than a disinfecting pH of 2.5.

[0094] It is envisioned that the control unit 100 of the system 10 may cause the PD fluid pump 70 (or a separate micropump) to inject, at the end of treatment, e.g., 2 ml of anti-scaling fluid or citric acid at 10 wt% citric acid concentration, (i) all at once prior to or at the beginning of heating the PD fluid for disinfection via the heater 56, or (ii) a portion, e.g., half, prior to or at the beginning of heating the PD fluid for disinfection, and the remaining portion, e.g., the remaining balance, at once during disinfection at the disinfection temperature, or distributed in equal amounts over multiple intervals during disinfection. In further alternative embodiments, the control unit 100 may cause the PD fluid pump 70 (or a separate micropump) to inject equal portions, e.g., 0.1 ml to 0.2 ml, of the anti-scaling fluid or citric acid over multiple intervals that divide the entire disinfection process, including heating the disinfection fluid and circulating the disinfection fluid at the desired disinfection temperature for a programmed disinfection time.

[0095] It is further envisioned that at the end of disinfection, the control unit 100 causes the PD fluid pump 70 to flush the disinfection loop 50 with additional unused PD fluid that has not been injected with the anti-scaling fluid. However, flushing may be performed because the glucose in the PD fluid may not be acceptable in terms of glucose degradation products ("GDP") after being heated to disinfection temperatures. In an alternative embodiment, the control unit 100 instead causes flushing to be performed at the start of the next treatment. In another alternative embodiment, the control unit 100 instead causes the disinfection loop 50 to drain after disinfection so that the circulator 20 is left disinfected and dry until the next treatment.

[0096] It should also be understood that other changes and modifications of the presently preferred embodiment described herein are covered by the appended claims. Accordingly, it is intended that such changes and modifications be covered by the appended claims. For example, although the drain line is illustrated and described as being disposable, the drain line may alternatively be reusable, and an additional disinfection connector is provided for the drain line to connect the drain line to a disinfection loop for a disinfection sequence.

Claims

1. 1. A peritoneal dialysis ("PD") system comprising: The housing and a plurality of PD fluid components contained by the housing; at least one reusable PD fluid line in fluid communication with the plurality of PD fluid components; a source of PD fluid in valved fluid communication with the at least one reusable PD fluid line; a source of anti-scaling fluid in valved fluid communication with the at least one reusable PD fluid line; Control unit and Equipped with the control unit is configured to: (i) operate the plurality of PD fluid components during treatment using PD fluid from the PD fluid source, wherein the PD fluid is heated to a treatment temperature; and (ii) circulate unused PD fluid heated to a disinfection temperature after treatment in combination with anti-scaling fluid from the anti-scaling fluid source to disinfect the plurality of PD fluid components and the at least one reusable PD fluid line, wherein the anti-scaling fluid is provided in an amount configured to lower a pH of the unused PD fluid to a level below which precipitate forms and to a level at or above a pH of 4; The PD system further comprises a valve and a redundant valve under the control of the control unit, the valve and the redundant valve providing the valved fluid communication located between the source of the anti-scaling fluid and the at least one reusable PD fluid line.

2. 10. The PD system of claim 1, wherein the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after treatment and prior to heating the unused PD fluid to the disinfecting temperature.

3. 3. The PD system of claim 1, wherein the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after treatment while heating the unused PD fluid to the disinfecting temperature.

4. 3. The PD system of claim 1 or 2, wherein the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after heating the unused PD fluid to the disinfecting temperature.

5. The PD system of claim 1 , wherein the anti-scaling fluid is an acid, such as citric acid.

6. The PD system of claim 1 , wherein the treatment temperature is approximately 37°C and the disinfection temperature is between 70°C and 95°C.

7. The PD system of claim 1 , wherein the pH of the unused PD fluid prior to pH reduction is greater than 6.5, such as at least 8.

0.

8. 10. The PD system of claim 1, wherein the reduced pH level is 6.5 or slightly below 6.

5.

9. 9. The PD system of claim 1, 7, or 8, wherein the plurality of PD fluid components includes a PD fluid pump, and the control unit is configured to operate the pump to pump the PD fluid and the anti-scaling fluid.

10. 2. The PD system of claim 1, wherein the plurality of PD fluid components includes a PD fluid heater, and the control unit is configured to operate the PD fluid heater to heat the PD fluid to the therapeutic temperature and the unused PD fluid to the disinfection temperature.

11. 11. The PD system of claim 1 or 10, wherein the anti-scaling fluid is provided in an amount configured to reduce the pH of the unused PD fluid to a level at a pH of 4-6.

12. 1. A peritoneal dialysis ("PD") system comprising: a plurality of PD fluid components; at least one reusable PD fluid line in fluid communication with the plurality of PD fluid components; a source of PD fluid in valved fluid communication with the at least one reusable PD fluid line; a source of anti-scaling fluid in valved fluid communication with the at least one reusable PD fluid line; Control unit and Equipped with The control unit (i) operating the plurality of PD fluid components during treatment using PD fluid from the PD fluid source, wherein the PD fluid is heated to a treatment temperature; (ii) determining whether unused PD fluid from said source to be used for disinfection contains bicarbonate; (iii) circulating the unused PD fluid heated to a disinfecting temperature after treatment in combination with anti-scaling fluid from the source of anti-scaling fluid to be used for disinfection when the unused PD fluid from the source to be used for disinfection contains bicarbonate to disinfect the plurality of PD fluid components and the at least one reusable PD fluid line; A PD system configured to:

13. 13. The PD system of claim 12, wherein (ii) occurs before or after (i).

14. 14. The PD system of claim 12 or 13, wherein the anti-scaling fluid is provided in an amount configured to lower the pH of the unused PD fluid to a level below which a precipitate forms and above which the pH causes disinfection.

15. 14. The PD system of claim 12 or 13, wherein the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after treatment and prior to heating the unused PD fluid to the disinfecting temperature.

16. 14. The PD system of claim 12 or 13, wherein the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after treatment while heating the unused PD fluid to the disinfecting temperature.

17. 14. The PD system of claim 12 or 13, wherein the control unit is configured to combine at least a portion of the anti-scaling fluid with the unused PD fluid after heating the unused PD fluid to the disinfecting temperature.

18. 13. The PD system of claim 12, wherein the control unit is further configured such that when the unused PD fluid from the source to be used for disinfection does not contain bicarbonate, the unused PD fluid heated to a disinfection temperature after treatment is circulated without combining with the anti-scaling fluid to disinfect the plurality of PD fluid components and the at least one reusable PD fluid line.

19. 13. The PD system of claim 12, wherein determining whether unused PD fluid from the source to be used for disinfection contains bicarbonate includes determining a type of PD fluid to be used for disinfection.

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