Dialysis system with pump reverse disinfection

Abstract

A peritoneal dialysis ("PD") system includes a housing, a PD fluid pump housed by the housing, an inline heater in fluid communication with the PD fluid pump, a temperature sensor, and a control unit. The PD fluid pump and the inline heater are under the control of the control unit, and the control unit receives a temperature signal from the temperature sensor. In one embodiment, the control unit is configured to perform a thermal disinfection sequence in which the control unit causes the PD fluid pump to pump a disinfection fluid in a forward direction while the inline heater heats the disinfection fluid, and the PD fluid pump causes the PD fluid pump to pump the disinfection fluid in a reverse direction while the inline heater heats the disinfection fluid. And pumping the disinfecting fluid in a reverse direction after the temperature signal indicates that the temperature of the disinfecting fluid has dropped to or below a minimum disinfecting temperature.

Description

Technical Field

[0001] The present disclosure relates generally to medical fluid therapy, and in particular to dialysis fluid therapy requiring pumping of patient injectable fluids. Background Art

[0002] For a variety of reasons, a person's kidney system may fail. Kidney failure produces a variety of physiological disturbances. It is no longer able to balance water and minerals or excrete the daily metabolic load. Toxic end products of metabolism (such as urea, creatinine, uric acid, and other substances) may accumulate in the patient's blood and tissues.

[0003] Dialysis is used to treat decreased kidney function, especially kidney failure. Dialysis removes waste products, toxins, and excess water from the body that would normally be removed by the kidneys. Dialysis treatment to replace kidney function is vital for many people because it is life-saving.

[0004] One type of renal failure therapy is hemodialysis ("HD"), which typically uses diffusion to remove waste products from a patient's blood. A diffusion gradient is created across a semipermeable dialyzer between the blood and an electrolyte solution called dialysate or dialysis fluid to induce 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 achieved by adding replacement or substitution fluid to the extracorporeal circuit during treatment. During HF treatment, the replacement fluid and the patient's accumulated fluid between treatments are ultrafiltered, providing a convective transport mechanism that is particularly beneficial for the removal of middle and large molecules.

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

[0007] Most HD, HF, and HDF treatments are performed at centers. Today there is a trend toward home hemodialysis ("HHD"), in part because HHD can be performed daily, which provides efficacy benefits compared to hemodialysis treatments in centers, which are typically performed every two or three weeks. Studies have shown that more frequent treatments remove more toxins and wastes and reduce interdialytic fluid overload compared to patients who receive less frequent but potentially longer treatments. Patients who receive more frequent treatments do not experience as many down cycles (fluctuations in fluids and toxins) as patients in centers, who have accumulated toxins for two or three days before treatment. In some areas, the nearest dialysis center may be many miles away from the patient's home, resulting in home treatment time taking up a large part of the day. Treatment at a center near the patient's home may also take up a large part 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 the patient's peritoneal compartment via a catheter. The dialysis fluid contacts the peritoneum within the patient's peritoneal compartment. Waste products, toxins, and excess water flow from the patient's blood through the capillaries in the peritoneum and enter the dialysis fluid due to diffusion and osmosis, i.e., an osmotic gradient occurs across the peritoneum. The osmotic agent in the PD dialysis fluid provides the osmotic gradient. Used or spent dialysis fluid is drained from the patient, thereby removing waste products, toxins, and excess water from the patient. This cycle is repeated, for example, multiple times.

[0009] There are many types of peritoneal dialysis therapies, including continuous ambulatory peritoneal dialysis ("CAPD"), automated peritoneal dialysis ("APD"), tidal flow dialysis, and continuous flow peritoneal dialysis ("CFPD"). CAPD is a manual dialysis treatment. Here, the patient manually connects an implanted catheter to a drain to allow used or spent dialysis fluid to drain from the peritoneal chamber. The patient then switches the fluid connection so that the patient's catheter is connected to a bag of fresh dialysis fluid to inject fresh dialysis fluid through the catheter and into the patient's body. The patient disconnects the catheter from the bag of fresh dialysis fluid and allows the dialysis fluid to reside in the peritoneal chamber, where the transfer of waste, toxins, and excess water occurs. After the residence period, the patient repeats the manual dialysis procedure, for example four times a day. Manual peritoneal dialysis requires a large amount of time and effort from the patient, which leaves much room for improvement.

[0010] Automated peritoneal dialysis ("APD") is similar to CAPD in that dialysis treatment includes drain, fill, and dwell cycles. However, automated PD machines typically perform these cycles automatically while the patient sleeps. PD machines eliminate the need for patients to manually perform treatment cycles or deliver supplies during the day. The PD machine is fluidly connected to an implanted catheter, a source or bag of fresh dialysis fluid, and a fluid drain. The PD machine pumps fresh dialysis fluid from a source of dialysis fluid through the catheter and into the patient's peritoneal compartment. The PD machine also allows the dialysis fluid to dwell within the peritoneal compartment and allows for the transfer of waste, toxins, and excess water. The source can include multiple liters of dialysis fluid, which include several bags of solution.

[0011] The PD machine pumps the spent or exhausted dialysate from the patient's peritoneal cavity through a catheter to a drain. As with the manual process, several drain, fill, and dwell cycles occur during dialysis. A "final fill" may occur at the end of APD treatment. The final fill fluid may remain in the patient's peritoneal compartment until the next treatment begins, or may be manually emptied at some point during the day.

[0012] In any of the above modes, automated machines and even manual CAPDs are typically operated with a disposable kit that is discarded after a single use. Depending on the complexity of the disposable kit, the cost of using one kit per day may become significantly large. Moreover, daily disposable items require space for storage, which may be troublesome for homeowners and businesses. In addition, daily disposable replacement requires daily setup time and effort by the patient or caregiver at home or in the clinic.

[0013] For each of the above reasons, it is desirable to provide an APD machine that reduces disposable waste. Summary of the invention

[0014] The present disclosure describes an automated peritoneal dialysis ("PD") system that provides one or more PD treatment improvements. The system includes a PD machine or cycler. The PD machine is capable of delivering fresh, heated PD fluid to a patient at, for example, 14 kPa (2.0 psig) or higher. The PD machine is capable of removing used PD fluid or effluent from a patient at, for example, between -5 kPa (-0.73 psig) and -15 kPa (-2.2 psig), such as -9 kPa (-1.3 psig) or higher. Fresh PD fluid can be delivered to a patient via a dual-lumen patient line and first heated to body fluid temperature, such as 37°C. The heated PD fluid is then pumped through the fresh PD fluid lumen of the dual-lumen patient line to a disposable filter kit, which is connected to the patient's transfer kit, which in turn is connected to an indwelling catheter in the patient's peritoneal cavity. The disposable filter kit is in fluid communication with the fresh and used PD fluid lumens of the dual-lumen patient line. A disposable filter kit is provided in one embodiment as a last chance filter for a PD machine that can be heat sterilized between treatments.

[0015] The system may include one or more PD fluid containers or bags that supply fresh PD fluid to the PD machine or cycler. The PD machine or cycler may include internal lines with two-way or three-way valves and at least one PD fluid pump for pumping fresh PD fluid from the one or more PD fluid containers or bags to the patient and for removing used PD fluid from the patient to a house drain or drain container. One or more flexible PD fluid lines lead from the internal lines of the PD machine or cycler to the one or more PD fluid containers or bags. The above-mentioned flexible double-lumen patient line leads from the PD machine or cycler to the patient. The flexible drain line leads from the internal lines of the PD machine or cycler to the house drain or drain container. In one embodiment, the system disinfects all internal lines, PD fluid lines, and double-lumen patient lines after treatment for reuse in the next treatment. Disinfection may involve heat disinfection using remaining fresh PD fluid.

[0016] In one embodiment, it is contemplated that the control unit causes the system's PD fluid pumps and valves to move heated PD fluid in the normal treatment direction at the start of a thermal disinfection sequence. The heated PD fluid is diverted as needed to flow through the disinfection circuit and then back to the inline heater. The length of the internal reusable tubing and flexible reusable PD fluid line between the outlet of the inline heater and the inlet of the inline heater 56 can be ten meters or more. Heat losses occur over the length of the line. Thus, a potential problem may occur in which, although the PD fluid leaving the inline heater is at a temperature sufficient to produce the desired amount of disinfection, the temperature of the PD fluid entering the inline heater is below what is considered to be the threshold minimum disinfection temperature.

[0017] In one example, a control unit, under feedback from a downstream temperature sensor, energizes the inline heater so that the PD fluid leaving the heater is at or about 85°C. In one embodiment, 85°C (185°F) is a desired output temperature because it is above the recommended minimum sterilization temperature, such as 75°C (167°F), and it is below the temperature at which the PD fluid may begin to boil. If the temperature of the PD fluid arriving at the inlet of the inline heater drops below the recommended minimum sterilization temperature, such as 75°C, corrective action is required. Corrective action may include increasing the heater outlet temperature, increasing the sterilization time, or some combination of the two. However, increasing the heater outlet temperature above 85°C risks causing the PD fluid to boil, while increasing the sterilization time increases component wear. It should be understood that the minimum sterilization temperature may vary, for example, from 65°C (149°F) to 95°C (203°F).

[0018] The present system and its associated method alternatively address potential low temperature issues by programming the control unit to automatically reverse the pumping direction of the PD fluid pump one or more times during the sterilization sequence so that newly heated PD fluid (e.g., at or about 85°C) is output from what is typically the heater inlet of the inline heater. As discussed in detail below, in one embodiment, the inline heater is bidirectional. Reversing the pumping direction of the PD fluid pump one or more times during the sterilization sequence causes the newly heated PD fluid (e.g., PD fluid newly heated to 85°C) to be more evenly distributed. Here, the hotter newly heated PD fluid mixes with the cooler PD fluid returning to the inline heater, causing the mixed PD fluid temperature to be above the recommended minimum sterilization temperature of, for example, 75°C. The more even distribution of the newly heated PD fluid helps eliminate bags of closed sterilization loops that may drop below the recommended minimum sterilization temperature. The more even distribution of the newly heated PD fluid also helps reduce the amount of time required for the sterilization sequence. For example, the time of the sterilization sequence can be roughly halved from two hours to one hour.

[0019] In one method of the present disclosure for controlling pump reversal during thermal sterilization, a control unit monitors the output of a temperature sensor positioned to sense the temperature of heated PD fluid re-entering the inline heater. In one embodiment, the control unit determines whether the temperature of the PD fluid re-entering the inline heater has dropped below a recommended minimum sterilization temperature (e.g., 75°C) for a specified or threshold amount of time (e.g., 60 seconds). Including the specified or threshold amount of time in the analysis allows the PD fluid temperature at the heater inlet to drop below the recommended minimum sterilization temperature for a short period of time or inadvertently without overreacting to the temporary temperature drop. It is contemplated that the threshold amount of time is optimized to allow for a more relaxed system, such as longer than one minute, or to allow for a tighter version of the system, such as 5 to 60 seconds.

[0020] When the temperature of the PD fluid re-entering the inline heater has dropped below the recommended minimum sterilization temperature for a threshold amount of time, the control unit causes the PD fluid pump to reverse direction and pump in the reverse direction. It is contemplated that the control unit controls the amount or timing of the reverse pumping of the PD fluid pump in a number of different ways. In one approach, the control unit causes the PD fluid pump to pump in the reverse direction for a plurality of pump strokes, such as one hundred pump strokes. In a second approach, the control unit causes the PD fluid pump to pump in the reverse direction until a particular temperature is reached at a temperature sensor that is a downstream temperature sensor during reverse pumping. In a third approach, the control unit causes the PD fluid pump to pump in the reverse direction until a particular temperature is reached at a downstream temperature sensor during pump reversal, followed by a preset number of additional pump strokes in the reverse pumping direction. The control unit causes the above sequence to repeat until the total sterilization time is reached.

[0021] In a second alternative method, a temperature sensor located immediately upstream of the heater may not be required, which has the advantage of reducing cost, eliminating sensors that may need to be calibrated from time to time, and eliminating parts that may need to be replaced. Here, the control unit causes the PD fluid pump to pump a preset number of pump strokes, such as 100 pump strokes, in the forward or normal treatment direction. After the preset number of pump strokes in the treatment direction have been completed, the control unit causes the PD fluid pump to automatically reverse and pump a preset number of pump strokes, such as 100 pump strokes, in the opposite direction. The control unit causes the above sequence to repeat until the total disinfection time is reached.

[0022] The present system and related methods may use a closed-loop heater control algorithm or a feed-forward open-loop heater control analysis. For closed-loop control, the control unit reads the temperature from a downstream temperature sensor. The control unit also stores a target temperature, for example, at or about 85°C. The control unit calculates the error between the command temperature or target temperature and the temperature read from the downstream temperature sensor. The control unit then inputs the calculated error into a closed-loop heating algorithm, such as a PID heating algorithm. The control unit uses the output from the heating algorithm to determine how much power to deliver to the inline heater. The cycle just described is repeated at a certain processing frequency.

[0023] Feed-forward open-loop heater control uses the output from the upstream temperature sensor to the control unit. For open-loop control, the control unit reads the temperature from the upstream temperature sensor and also stores a target temperature, such as 85°C. The control unit also determines (calculates or measures) the current PD fluid flow rate. If a piston pump is used as the PD fluid pump and a flow meter is not provided, the control unit calculates the current flow rate by accumulating pump strokes of a known volume pumped by the PD fluid pump and dividing the accumulated volume by the amount of time required to accumulate pump strokes. If a separate flow meter is provided instead, the control unit measures the flow rate by reading the output from the flow meter.

[0024] The control unit inputs the temperature from the upstream temperature sensor and the determined flow rate into the feed-forward heater algorithm. The control unit uses the output from the feed-forward heater algorithm (or a derivative or related quantity thereof) to determine how much current or power to deliver to the inline heater. The cycle just described is repeated at some processing frequency.

[0025] In accordance with the disclosure set forth herein, and without limiting the disclosure in any way, in a first aspect of the disclosure, which may be combined with any other aspect or portion thereof, a peritoneal dialysis ("PD") system comprises: a housing; a PD fluid pump housed by the housing; an inline heater in fluid communication with the PD fluid pump; a temperature sensor; and a control unit, the PD fluid pump and the inline heater being under the control of the control unit, the control unit receiving a temperature signal from the temperature sensor, the control unit being configured to perform a thermal disinfection sequence in which the control unit causes the PD fluid pump to pump a disinfection fluid in a forward direction while the inline heater heats the disinfection fluid, and to pump the disinfection fluid in a reverse direction after the temperature signal indicates that the temperature of the disinfection fluid has dropped to a minimum disinfection temperature or has dropped below the minimum disinfection temperature.

[0026] In a second aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to cause the PD fluid pump to pump the disinfection fluid in the reverse direction after the temperature signal indicates that the temperature of the disinfection fluid has dropped to the minimum disinfection temperature or has dropped below the minimum disinfection temperature during a specified amount of time.

[0027] In a third aspect of the disclosure which may be combined with any other aspect or a portion thereof, when the PD fluid pump pumps the sterilizing fluid in the forward direction, the temperature sensor is located upstream of the inline heater.

[0028] In a fourth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the temperature signal is used as closed loop feedback to the control unit for controlling the inline heater when the PD fluid pump pumps the sterilizing fluid in the reverse direction.

[0029] In a fifth aspect of the present disclosure, which may be combined with any other aspect or part thereof, the temperature sensor is a first temperature sensor and includes a second temperature sensor, wherein the second temperature sensor is located downstream of the inline heater when the PD fluid pump pumps the disinfection fluid in the forward direction, and wherein the temperature signal from the second temperature sensor is used as closed-loop feedback to the control unit for controlling the inline heater when the PD fluid pump pumps the disinfection fluid in the forward direction.

[0030] In a sixth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the inline heater is controlled such that a temperature of the disinfecting fluid exiting the inline heater is about 85°C.

[0031] In a seventh aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the control unit is configured to cause the PD fluid pump to pump the disinfecting fluid in the reverse direction for a plurality of pump strokes.

[0032] In an eighth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the control unit is configured to cause the PD fluid pump to pump the disinfecting fluid in the reverse direction until a determined temperature as indicated by the temperature sensor is reached.

[0033] In a ninth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to cause the PD fluid pump to pump the disinfectant fluid in the reverse direction until a determined temperature as indicated by the temperature sensor is reached, followed by a plurality of pump strokes in the reverse direction.

[0034] In a tenth aspect of the present disclosure, which may be combined with any other aspect or a portion thereof, the thermal disinfection sequence is performed using a disinfection circuit, the disinfection circuit comprising: a reusable patient line extending from the shell, the reusable patient line comprising a distal end, the distal end being configured to connect to a patient line connector provided by the shell; and at least one reusable PD fluid line extending from the shell, the at least one reusable PD fluid line comprising a distal end, the distal end being configured to connect to a PD fluid line connector provided by the shell.

[0035] In an eleventh aspect of the present disclosure which may be combined with any other aspect or a portion thereof, at least one of the following items is satisfied: (i) the minimum sterilization temperature is 65°C (149°F) to 95°C (203°F); or (ii) the sterilization fluid is a PD fluid.

[0036] In a twelfth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a peritoneal dialysis ("PD") system comprises: a housing; a PD fluid pump housed by the housing; an inline heater in fluid communication with the PD fluid pump; a temperature sensor; and a control unit, the PD fluid pump and the inline heater being under the control of the control unit, the control unit receiving a temperature signal from the temperature sensor, the control unit being configured to perform a thermal disinfection sequence in which the control unit causes the PD fluid pump to pump a disinfection fluid in a forward direction while the inline heater heats the disinfection fluid; and to pump the disinfection fluid in a reverse direction, wherein the control unit controls the inline heater using a feed-forward algorithm that takes into account the temperature signal and the flow rate of the disinfection fluid.

[0037] In a thirteenth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the temperature signal provides a heater inlet temperature, and wherein the feedforward algorithm subtracts the inlet temperature from a target temperature.

[0038] In a fourteenth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the flow rate of the disinfecting fluid is calculated by the control unit by accumulating known pump volumes pumped by the PD fluid pump.

[0039] In a fifteenth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the PD system comprises a flow meter in fluid communication with the PD fluid pump, and wherein the flow rate of the disinfecting fluid is measured by the flow meter.

[0040] In a sixteenth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the feedforward algorithm is constructed to calculate output power = (target temperature - inlet temperature obtained from the temperature signal) x (flow rate of the disinfection fluid) x (specific heat capacity of water).

[0041] In a seventeenth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the target temperature is 85°C.

[0042] In an eighteenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the temperature sensor is located downstream of the inline heater when the PD fluid pump pumps the disinfection fluid in the forward direction, and wherein, when the PD fluid pump pumps the disinfection fluid in the forward direction, the temperature signal is used as closed-loop feedback to the control unit for controlling the inline heater.

[0043] In a nineteenth aspect of the present disclosure, which may be combined with any other aspect or a portion thereof, the control unit is configured to cause: (i) the PD fluid pump to pump the disinfectant fluid in the forward direction for a plurality of pump strokes, and (ii) the PD fluid pump to automatically reverse and pump the disinfectant fluid in the reverse direction for a plurality of pump strokes.

[0044] In a twentieth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the control unit is further configured to repeat (i) and (ii) until a total disinfection time is reached.

[0045] In a twenty-first aspect of the present disclosure that may be combined with any other aspect or a part thereof, Figure 1 , Figure 2 and Figures 4 to 8 Any one or more of the features, functions and alternatives described in any one or more of the above may be combined with Figure 1 , Figure 2 and Figures 4 to 8 any combination of any features, functions and alternatives described in any other manner.

[0046] In view of the above aspects and the present disclosure set forth herein, it is an advantage of the present disclosure to provide dialysis systems and methods with improved thermal disinfection.

[0047] Another advantage of the present disclosure is to provide a dialysis system and method for thermal sterilization with fewer or no low temperature sterilization fluid bags.

[0048] Another advantage of the present disclosure is to provide PD systems and methods with reduced disinfection time.

[0049] Additional features and advantages are described in and will be apparent from the following detailed description and accompanying drawings. The features and advantages described herein are not all-inclusive, and in particular, many additional features and advantages will be apparent to one of ordinary skill in the art with reference to the drawings and description. In addition, any particular embodiment need not have all of the improvements or advantages listed herein, and it is expressly contemplated that individual advantageous embodiments are individually claimed. In particular, the systems disclosed herein may have any one or more or all of the drip-proof structures and methods, PD fluid container emptying structures and methods, and pre-drain patient connection check structures and methods described herein. In addition, it should be noted that the language used in the specification is 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

[0050] Figure 1 is a fluid flow diagram of one embodiment of a medical fluid (eg, PD fluid) system configured for treatment.

[0051] Figure 2 is used for Figure 1 Schematic diagram of fluid flow of one embodiment of a medical fluid (eg, PD fluid) system that has been rearranged for sterilization.

[0052] Figure 3 Included is a graph showing the inline heater inlet temperature versus the inline heater outlet temperature when the pump reverse sterilization of the present disclosure is not used or employed.

[0053] Figure 4 is a process flow diagram illustrating one embodiment for reversing the flow of heated PD fluid during a disinfection sequence of the present disclosure.

[0054] Figure 5 is a process flow diagram illustrating another embodiment for reversing the flow of heated PD fluid during a sterilization sequence of the present disclosure.

[0055] Figure 6 A localized fluid path is shown showing an inline heater and temperature sensor for closed loop control, which may be employed for both forward and reverse PD fluid sterilization flow.

[0056] Figure 7 A partial fluid path is shown showing an inline heater and upstream temperature sensor for an open loop feed-forward heating control algorithm used during reverse PD fluid sterilization flow.

[0057] Figure 8 Included are graphs showing the inline heater inlet temperature and the inline heater outlet temperature versus time, illustrating the effectiveness of the pump reverse sterilization of the present disclosure. DETAILED DESCRIPTION

[0058] System Overview

[0059] Reference is now made to the drawings, and in particular to the Figure 1 , the medical system with reverse thermal disinfection of the pump of the present disclosure is shown via a peritoneal dialysis ("PD") system 10. The system 10 includes a PD machine or cycler 20 and a control unit 100 having one or more processors 102, one or more memories 104, a video controller 106, and a user interface 108. Alternatively or additionally, the user interface 108 can be a remote user interface, for example, via a tablet or smart phone. The control unit 100 can also include a transceiver and a wired or wireless connection to a network (not shown) (e.g., the Internet) for sending treatment data to a doctor's or clinician's server interconnected with a doctor's or clinician's computer and receiving prescription instructions / changes from a doctor's or clinician's server interconnected with a doctor's or clinician's computer. In one embodiment, the control unit 100 controls all of the electric fluid flow and heating components of the system 10 and receives outputs from all of the sensors of the system 10. The system 10 in the illustrated embodiment includes durable and reusable components that contact fresh and used PD fluids, which require the PD machine or cycler 20 to be disinfected between treatments, such as by thermal disinfection.

[0060] Figure 1 The system 10 in the embodiment includes an inline resistive heater 56, reusable supply lines or tubes 52a1 to 52a4 and 52b, an air trap 60 operating with corresponding upper and lower level sensors 62a, 62b, an air trap valve 54d, an exhaust valve 54e positioned along an exhaust line 52e, a reusable line or tube 52c, a PD fluid pump 70, temperature sensors 58a and 58b and possibly a third temperature sensor 58c, and a pressure sensor 78. a, 78b1, 78b2 and 78c, reusable patient tubing or lines 52f and 52g with corresponding valves 54f and 54g, dual lumen patient line 28, hose reel 80 for retrieving patient line 28, reusable drain tubing or line 52i extending to drain line connector 34 and having drain line valve 54i, and reusable recirculation tubing or lines 52r1 and 52r2 operating with corresponding sterilization valves 54r1 and 54r2. A third recirculation or sterilization tubing or line 52r3 extends between sterilization or PD fluid line connectors 30a and 30b for use during sterilization. A fourth recirculation or sterilization tubing or line 52r4 extends between sterilization connectors 30c and 30d for use during sterilization.

[0061] The system 10 also includes PD fluid containers or bags 38a-38c (e.g., holding the same or different PD fluid formulations) connected to the distal ends 24e of the reusable PD fluid lines 24a-24c, respectively. The system 10d also includes a fourth PD fluid container or bag 38d connected to the distal end 24e of the reusable PD fluid line 24d. The fourth PD fluid container or bag 38d can hold the same or a different type of PD fluid (e.g., icodextrin) as provided in the PD fluid containers or bags 38a-38c. The reusable PD fluid lines 24a-24d, in one embodiment, extend through an aperture (not shown) defined or provided by the housing 22 of the cycler 20.

[0062] The system 10 in the illustrated embodiment includes four sterile or PD fluid line connectors 30a to 30d for connection to the distal ends 24e of the reusable PD fluid lines 24a to 24d, respectively, during sterilization. The system 10 also provides a patient line connector 32 that includes an internal lumen, such as a U-shaped lumen, that directs fresh or used dialysis fluid from one PD fluid lumen of the connected distal ends 28e of the dual lumen patient line 28 to the other PD fluid lumen for sterilization. Reusable supply tubing or lines 52a1 to 52a4 are in communication with the reusable supply lines 24a to 24d, respectively. The reusable supply tubing or lines 52a1 to 52a3 operate with valves 54a to 54c, respectively, to allow PD fluid from the desired PD fluid container or bag 38a to 38c to be drawn into the cycler 20. In the example shown, three-way valve 94a allows the control unit 100 to select between (i) 2.27% (or other) glucose dialysis fluid from container or bag 38b or 38c and (ii) icodextrin from container or bag 38d. In the embodiment shown, icodextrin from container or bag 38d is connected to the normally closed port of three-way valve 94a.

[0063] In one embodiment, system 10 is configured such that drain line 52i is fluidly connected downstream of PD fluid pump 70 during a patient fill. In this way, if drain valve 54i fails or somehow leaks during a patient fill of patient P, fresh PD fluid is pushed down disposable drain line 36 rather than spent PD fluid potentially being pulled into pump 70. Disposable drain line 36 is removed in one embodiment for sterilization, wherein drain line connector 34 is capped via cap 34c to form a closed sterilization loop. PD fluid pump 70 may be an inherently accurate pump, such as a piston pump, or a less accurate pump, such as a gear pump that operates in cooperation with a flow meter (not shown) to control fresh and spent PD fluid flow and volume.

[0064] The system 10 may also include a leak detection disc 82 located at the bottom of the housing 22 of the cycler 20 and a corresponding leak detection sensor 84 that outputs to the control unit 100. In the example shown, the system 10 is provided with an additional pressure sensor 78c located upstream of the PD fluid pump 70, which allows the suction pressure of the pump 70 to be measured to help the control unit 100 more accurately determine the pump volume. The additional pressure sensor 78c in the embodiment shown is located along the exhaust line 52e, which may be filled with air or a mixture of air and PD fluid, but should still be at the same negative pressure as the PD fluid located in the PD fluid line 52c.

[0065] Figure 1 The system 10 in the example of FIG. 1 includes redundant pressure sensors 78b1 and 78b2, the output of one of the redundant pressure sensors 78b1 and 78b2 is used for pump control, as discussed herein, while the output of the other pressure sensor is a safety or watchdog output to ensure that the control pressure sensor reads accurately. The pressure sensors 78b1 and 78b2 are located along the line including the third recirculation valve 54r3. The system 10 may also employ a Figure 1 The X marks one or more cross-pieces that can (i) reduce the total amount and volume of internal reusable tubing, (ii) reduce the number of valves required, and (iii) allow for minimization of the portion of the fluid circuit that is shared by fresh and used PD fluids.

[0066] exist Figure 1The system 10 in the example of also includes an acid source, such as a citric acid container or bag 66. The citric acid container or bag 66 is in selective fluid communication with the second three-way valve 94b via a citric acid valve 54m located along the citric acid line 52m. In one embodiment, the citric acid line 52m is connected to the normally closed port of the second three-way valve 94b to provide a redundant valve between the citric acid container or bag 66 and the PD fluid circuit during treatment. The redundant valve ensures that no citric acid (or other) reaches the treatment fluid line during treatment. Instead, citric acid (or other acid) is used during disinfection.

[0067] In one embodiment, the control unit 100 uses feedback from any one or more of the pressure sensors 78a-78c to enable the PD machine 20 to deliver fresh, heated PD fluid to the patient at a pressure of, for example, 14 kPa (2.0 psig) or higher. The pressure feedback is used to enable the PD machine 20 to remove spent PD fluid or effluent from the patient at a pressure of, for example, between -5 kPa (-0.73 psig) and -15 kPa (-2.2 psig), such as -9 kPa (-1.3 psig) or higher (more negative). The pressure feedback can be used in a proportional, integral, derivative ("PID") pressure routine for pumping fresh and spent PD fluid at a desired positive or negative pressure.

[0068] The inline resistive heater 56 under the control of the control unit 100 is capable of heating the fresh PD fluid to body temperature, e.g., 37° C., for delivery to the patient P at a desired flow rate. In an embodiment, the control unit 100 uses feedback from the temperature sensor 58 a in a PID temperature routine for pumping fresh PD fluid to the patient P at a desired temperature. The control and operation of the inline resistive heater 56 for thermal disinfection is discussed in detail below.

[0069] Figure 1 Also shown is that the system 10 includes and uses a disposable filter kit 40 that is in fluid communication with the fresh and used PD fluid lumens of the dual lumen patient line 28. The disposable filter kit 40 includes a disposable connector 42 connected to the distal end 28e of the reusable patient line 28. The disposable filter kit 40 also includes a connector 44 that is connected to the patient's transfer kit. The disposable filter kit 40 also includes a sterilizing grade filter membrane 46 that further filters the fresh PD fluid. The disposable filter kit 40 is provided in one embodiment as a last chance filter for the PD machine 20, which is heat sterilized between treatments. Any pathogens that may remain after sterilization (although unlikely) are filtered out of the PD fluid via the sterilizing grade filter membrane 46 of the disposable filter kit 40.

[0070] Figure 1 The arrangement of the system 10 for treatment is shown, wherein PD fluid containers or bags 38a to 38d are connected via reusable flexible PD fluid lines 24a to 24d, respectively. The dual lumen patient line 28 is connected to the patient P via a disposable filter kit 40. The disposable drain line 36 is connected to the drain line connector 34. Figure 1 In the embodiment of the present invention, the PD machine or cycler 20 of the system 10 is configured to perform a plurality of patient drain, patient fill, patient dwell and priming procedures as part of a treatment or in preparation for performing a treatment.

[0071] Figure 2 The system 10 is shown in a sterilization mode. The PD fluid containers or bags 38a-38d are removed and the flexible PD fluid lines 24a-24d are inserted in a sealed manner into sterilization or PD fluid line connectors 30a-30d, respectively. The reusable dual lumen patient line 28 is disconnected from the disposable filter kit 40 (which is discarded) and the distal end 28e of the dual lumen patient line 28 is sealingly inserted into the patient line connector 32. The disposable drain line 36 is removed from the drain line connector 34 and discarded. The drain line connector 34 is capped via the cap 34c to form a closed sterilization circuit 90. Figure 2 The PD machine or cycler 20 of the system 10 in is configured to perform a sterilization sequence, such as a thermal sterilization sequence, in which fresh PD fluid is heated to a sterilization temperature, such as 75° C. or higher, via an inline heater 56. The PD fluid pump 70 circulates the heated PD fluid closed sterilization circuit 90 for an amount of time required to properly sterilize the fluid components and lines of the sterilization circuit.

[0072] Pump reverse thermal disinfection

[0073] In one embodiment, the control unit 100 causes the PD fluid pump 70 and valves of the system 10 to move the heated PD fluid across the PD fluid in the normal treatment direction (eg, from left to right) at the beginning of the thermal disinfection sequence. Figure 2 52i. The heated PD fluid may be split between the fresh patient conduit or line 52f and the drain conduit or line 52i. The heated PD fluid stream split through the fresh patient conduit or line 52f continues to flow through: the fresh PD lumen of the dual lumen patient line 28, the used PD lumen of the dual lumen patient line 28, the used patient conduit or line 52g, and the conduit or line 52c, back to the PD fluid pump 70. The heated PD fluid stream split through the fresh patient conduit or line 52f is further split into a line including pressure sensors 78b1 and 78b2 and a third recirculation valve 54r3, which then joins the heated PD fluid stream through the recirculation line 52r1.

[0074] The heated PD fluid flow diverted through the exhaust pipe or line 52i continues to flow through the exhaust line connector 34, the recirculation pipe or line 52r2, the recirculation pipe or line 52r1, the reusable flexible PD fluid lines 24a to 24d, the pipes or lines 52a1 to 52a4, the recirculation pipes or lines 52r3 and 52r4 back to the inlet of the inline heater 56. The length of the internal reusable pipe and reusable flexible PD fluid lines 24a to 24d between the outlet of the inline heater 56 and the inlet of the inline heater 56 can be ten meters or more. Heat losses will occur over the length of the line. Therefore, the following potential problem may occur, in which the temperature of the PD fluid returning to the inline heater 56 and entering the inline heater 56 is below the temperature considered to be the threshold minimum disinfection temperature, although the PD fluid leaving the inline heater 56 is at a temperature sufficient to produce the desired amount of disinfection.

[0075] In one example, the control unit 100 energizes the inline heater 56 based on feedback from the temperature sensor 58a so that the PD fluid exiting the heater is at or about 85°C. In one embodiment, 85°C (185°F) is a desired output sterilization temperature because it is above the recommended minimum sterilization temperature, such as 75°C (167°F), and it is below the temperature at which the PD fluid may begin to boil. If the temperature of the PD fluid arriving at the heater inlet 56i of the inline heater 56 drops below the recommended minimum sterilization temperature, such as 65°C (149°F) to 95°C (203°F), such as 75°C (167°F), corrective action needs to be taken. Figure 3 A graph showing the temperature at the heater inlet 56i versus the temperature at the heater outlet 56o is included without the pump reversal of the present disclosure. Here, the temperature at the outlet 56o of the heater 56 varies between 80°C (176°F) and 90°C (194°F) and remains above the recommended minimum sterilization temperature, which is, for example, 75°C (167°F), whereas the temperature at the inlet 56i of the heater 56 approaches but remains below 70°C (158°F). The temperature at the inlet 56i of the heater 56 may therefore drop below the recommended minimum sterilization temperature, which is, for example, 75°C (167°F). In the illustrated embodiment, the time varies in minutes.

[0076] Used to raise Figure 3Corrective measures for the temperature of the inlet 56i of the illustrated heater 56 may include increasing the heater outlet temperature, increasing the sterilization time, or some combination of the two. However, increasing the heater outlet temperature above 85°C risks causing the PD fluid to begin boiling, while increasing the sterilization time increases component wear. The system 10 and associated methods alternatively address potential low temperature issues by programming the control unit 100 to automatically reverse the pumping direction of the PD fluid pump 70 one or more times during the sterilization sequence so that newly heated PD fluid (e.g., at 85°C) is output from what is typically the heater inlet 56i of the inline heater 56. In one embodiment, the inline heater 56 is bidirectional so that PD fluid flowing in either direction from the inlet 56i to the outlet 56o or from the outlet 56o to the inlet 56i can be heated to a desired temperature under the control of the control unit 100. A non-bidirectional inline heater 56 may be used. Here, control unit 100 may heat the PD fluid in the normal direction for a desired number of pump strokes and to a desired and controlled temperature, and then cause PD fluid pump 70 to pump the same desired number of pump strokes in the reverse direction to push the newly heated PD fluid out of heater inlet 56i. When pumping in the reverse direction, inline heater 56 may or may not be powered.

[0077] Reversing the pumping direction of the PD fluid pump 70 one or more times during the sterilization sequence allows the newly heated PD fluid (e.g., PD fluid heated to 85° C.) to be more evenly distributed. Here, the hotter newly heated PD fluid mixes with the cooler PD fluid returning to the inline heater 56, bringing the mixed PD fluid temperature above the recommended minimum sterilization temperature of, e.g., 75° C. The more even distribution of the newly heated PD fluid helps eliminate bags of the closed sterilization loop 90 that may drop below the recommended minimum sterilization temperature. The more even distribution of the newly heated PD fluid also helps reduce the amount of time required for a sterilization sequence. For example, using the pump-reversed heated PD fluid sterilization of the present disclosure, the time for a sterilization sequence can be roughly halved from two hours to one hour.

[0078] Figure 4 A method 110 is shown that can be implemented in the control unit 100 for controlling pump reversal during thermal disinfection of the present disclosure. At oval 112, the method 110 begins. At box 114, the control unit 100 opens all two-way valves associated with the disinfection circuit 90 and causes the PD fluid pump 70 to flow in the forward treatment direction (from left to right through the PD fluid pump 70). Figure 1 and Figure 2The pump 70 in the sterilization sequence is operated, which is also considered the normal sterilization sequence direction. At box 114, the control unit 100 also uses feedback from the temperature sensor 58a and a heating algorithm (such as a proportional, integral, derivative ("PID") heating algorithm) to control the inline heater 56 to output heated PD fluid at the heater outlet 56o at the desired sterilization temperature (such as 85°C).

[0079] At box 116, the control unit 100 monitors the output of the temperature sensor 58c, which is the temperature of the heated PD fluid re-entering the inline heater 56 at the heater inlet 56i. At diamond 118, the control unit 100 determines whether the temperature of the PD fluid re-entering the inline heater 56 at the heater inlet 56i (as indicated by the temperature sensor 58c) has dropped below the recommended minimum sterilization temperature (e.g., 75°C) for a threshold or specified amount of time (e.g., 60 seconds). Including the threshold amount of time in the query at diamond 118 allows the PD fluid temperature at the heater inlet 56i to drop below the recommended minimum sterilization temperature for a short period of time or unintentionally without overreacting to the temporary temperature drop. It is contemplated that the threshold amount of time is optimized to allow for a more relaxed version of the method 110 (e.g., longer than one minute) or to allow for a more stringent version of the method 110 (e.g., five to sixty seconds).

[0080] If the temperature of the PD fluid re-entering the inline heater 56 at the heater inlet 56i has not dropped below the recommended minimum sterilization temperature for a threshold amount of time, as determined at diamond 118, then at diamond 120, the control unit 100 determines whether the total sterilization sequence time has been reached. Proper sterilization of the sterilization circuit 90 involves movement of PD fluid heated to or above the recommended minimum sterilization temperature through the sterilization circuit 90 for a specified period of time, such as two hours. Once the total or specified sterilization time is reached, as determined at diamond 120, the sterilization sequence is completed and the method 110 ends at oval 122.

[0081] If at diamond 120, the total or specified disinfection time has not been reached, the method 110 returns to the Figure 4 The loop just described between box 114 and diamond 120 is repeated until the total or specified sterilization time has been reached (at diamond 120) or the temperature of the PD fluid re-entering the inline heater 56 at the heater inlet 56i has dropped below the recommended minimum sterilization temperature for a threshold amount of time (at box 118).

[0082] At box 118, when the temperature of the PD fluid re-entering the inline heater 56 at the heater inlet 56i has dropped below the recommended minimum sterilization temperature for a threshold amount of time, at box 124, the control unit 100 reverses the PD fluid pump 70 and pumps in the opposite direction (in the reverse direction). Figure 1 and Figure 2 The control unit 100 also operates any valves of the disinfection circuit 90 in sequence as needed, such as operating the three-way valve 94a in sequence. It is contemplated that the control unit 100 controls the amount or timing of the pumping reversal of the PD fluid pump 70 in a variety of different ways. In one approach, the control unit 100 causes the PD fluid pump 70 to pump a plurality of pump strokes in the reverse direction, such as one hundred pump strokes. In a second approach, the control unit 100 causes the PD fluid pump 70 to pump in the reverse direction until a certain temperature, such as 85° C. (the command output of the heater 56) is reached at the temperature sensor 58 c, where the temperature sensor 58 c is the downstream temperature sensor during reverse pumping. In a third approach, the control unit 100 causes the PD fluid pump 70 to pump in the reverse direction until a certain temperature, such as 85° C., is reached at the temperature sensor 58 c, and then a preset number of additional pump strokes are performed in the reverse pumping direction.

[0083] When reverse pumping of the PD fluid pump 70 is completed via any of the above-described methods, the method 110 returns to the Figure 4 As discussed in conjunction with diamond 118 and box 124, the temperature sensor 58c located immediately upstream of the heater inlet 56i in the normal pumping direction is used as part of the trigger for initiating pump reversal (diamond 118) and may be used to determine how long to perform pump reversal (box 124). The output of the temperature sensor 58c is also used as feedback to the control unit 100 for controlling the power supply to the inline heater 56 when the pumping of the PD fluid pump 70 is reversed so that a maximum temperature, such as 85°C, is not exceeded.

[0084] Figure 5 An alternative method 130 is shown in which the temperature sensor 58c located just upstream of the heater inlet 56i may not be required, which has the advantage of reducing cost, eliminating sensors that may need to be calibrated from time to time, and eliminating parts that may need to be replaced. At box 132, the method 130 begins. At box 134, the control unit 100 opens all two-way valves associated with the sterilization circuit 90. At box 134, the control unit 100 also uses feedback from the temperature sensor 58a and a heating algorithm (such as a proportional, integral, derivative ("PID") heating algorithm) to control the inline heater 56 to output heated PD fluid at the heater outlet 56o at a desired sterilization temperature (such as 85°C). At box 134, the control unit 100 causes the PD fluid pump 70 to flow in the normal treatment (forward) direction (from left to right through the sterilization circuit 90). Figure 1 and Figure 2 The pump 70 in the embodiment of the present invention pumps a preset number of pump strokes, for example 100 pump strokes.

[0085] At block 136, after a preset number of pump strokes in the treatment direction have been completed, the control unit 100 automatically reverses the PD fluid pump 70 and pumps in the opposite direction (in the Figure 1 and Figure 2 The control unit 100 also operates any valves of the sterilization circuit 90 in sequence as needed, such as the three-way valve 94a. In one embodiment, the control unit 100 causes the PD fluid pump 70 to pump a preset number of pump strokes, such as 100 pump strokes, in the reverse direction. As described below, in one embodiment, the control unit 100 can use feed-forward open-loop heater control during pump reversal of the method 130, which does not require the use of the temperature sensor 58c (but closed-loop control using the temperature sensor 58c can be performed instead).

[0086] At diamond 138, after the preset number of pump strokes in the reverse direction have been completed, the control unit 100 determines whether the total disinfection sequence time has been reached. Proper disinfection of the disinfection circuit 90 of method 130 again involves movement of PD fluid heated to or above the recommended minimum disinfection temperature through the disinfection circuit 90 for a specified period of time. If the total or specified disinfection time has not been reached, as determined at diamond 138, the method 130 returns to box 134. Once the total or specified disinfection time is reached, as determined at diamond 138, the disinfection sequence is complete and the method 130 ends at oval 140.

[0087] Figure 6 One embodiment of closed loop control using a downstream pressure sensor is shown, which may be used for forward and reverse heated PD fluid sterilization flows in method 110 and for forward heated PD fluid sterilization flows in method 130 . Figure 6 A portion of a disinfection circuit 90 is shown having an inline heater 56, a temperature sensor 58a outputting to a control unit 100, and a temperature sensor 58c outputting to a control unit 100. In the forward direction, the output from the temperature sensor 58a is used for feedback control. In the reverse direction, the output from the temperature sensor 58c is used for feedback control.

[0088] Figure 5It is shown that for closed loop control, the control unit 100 reads the temperature from the associated temperature sensors 58a, 58c. The control unit 100 also stores a target temperature, for example 85°C. The control unit 100 calculates the error between the command or target temperature and the temperature read from the associated temperature sensors 58a, 58c. The control unit 100 then inputs the calculated error into a heating algorithm, such as a PID heating algorithm. The control unit 100 uses the output from the heating algorithm to determine how much power to deliver to the inline heater. The cycle just described is repeated at a certain processing frequency.

[0089] It should be understood that for both methods 110 and 130, closed-loop control in the forward direction should very quickly produce a temperature reading at temperature sensor 58a that is within the range of the commanded temperature, e.g., 85°C. For method 100, which triggers reverse flow when temperature sensor 58c senses a low temperature for a certain period of time as described above, then the same temperature sensor 58c used for closed-loop control will initially read a lower temperature corresponding to a mixture of hot PD fluid leaving the inline heater 56 in the reverse direction and the cooler PD fluid just residing upstream of the heater inlet 56i. Here, after a period of time, temperature sensor 58c begins to read temperatures within the commanded temperature range (e.g., 85°C).

[0090] Figure 7 An alternative approach for controlling the inline heater 56 during reverse PD fluid flow is shown which involves feed-forward open loop control and which does not require a temperature sensor 58c ( Figure 7 ). Therefore, the feed-forward open-loop heater control is applicable to the reverse PD fluid flow of method 130. The feed-forward open-loop heater control used during the reverse PD fluid flow of method 130 Figure 7 The feed-forward open loop heater control uses the output from the temperature sensor 58a to the control unit 100. It should be appreciated that the temperature sensor 58a is located upstream of the heater outlet 56o of the inline heater 56 during reverse PD fluid flow.

[0091] Figure 6 It is shown that for open loop control, the control unit 100 reads the temperature from the temperature sensor 58a and also stores a target temperature, e.g., 85°C. The control unit 100 also determines (calculates or measures) the current PD fluid flow rate. If a piston pump is used as the PD fluid pump 70 and a flow meter is not provided, the control unit 100 calculates the current flow rate by accumulating pump strokes of a known volume pumped by the PD fluid pump 70 and dividing the accumulated volume by the amount of time required to accumulate pump strokes. If instead a separate flow meter ( Figure 1 and Figure 2 (not shown), the control unit 100 measures the flow rate by reading the output of the flow meter.

[0092] exist Figure 7 At , the control unit 100 inputs the temperature from the temperature sensor 58a and the determined flow rate into the feed-forward heater algorithm. The control unit 100 uses the output from the feed-forward heater algorithm (or its derivative or related quantity) to determine how much power to deliver to the inline heater. The cycle just described is repeated at a certain processing frequency. In one example, the feed-forward heater algorithm can be:

[0093] Required heater output power = (target temperature - inlet temperature) x PD fluid flow x specific heat capacity of water

[0094] In the example where the inlet temperature read by the temperature sensor 58a is 70°C, the target temperature is 85°C, the determined flow rate is 300 ml / min (5 ml / sec), and the specific heat capacity of water is 4.184 (Joules / gram x °K), then the required output power is (85-70) x 5 x 4.184, which equals a heating power of 313.8 watts. In one embodiment, the control unit's memory 104 stores a lookup table for the inline heater 56 that correlates how much current or heater input power is required to achieve a heating power of 313.8 watts (or the closest power stored).

[0095] Figure 8 Two temperature graphs Ti and To are shown over time, which are the temperature at the inlet 56i of the inline heater 56 and the temperature at the outlet 56o of the inline heater 56, respectively. The reversal of the PD fluid pump 70 caused by the control unit 100 during sterilization, for example at time t rev t occurs, where a sharp increase in temperature occurs at the inlet 56i of the heater 56. Stopping the reversal of the PD fluid pump 70 caused by the control unit 100 during sterilization and instead pumping again in the normal direction occurs, for example, at time t norm , where a sharp increase in temperature occurs at the outlet 56o of the heater 56. It should be understood that although the temperatures in both temperature graphs Ti and To are shown to drop to about 60°C (140°F), which may be below the minimum sterilization temperature, the power (or duty cycle) of the heater 56 can be increased so that the minimum temperature of the temperature graphs Ti and To does not drop or does not drop significantly below the minimum sterilization temperature, such as 75°C (167°F). In the illustrated embodiment, the time varies in minutes. Figure 8 The importance of φ is that it shows that pump reversal does have a significant and immediate effect on the temperature at the inlet 56 i of the inline heater 56 .

[0096] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Accordingly, such changes and modifications are intended to be covered by the appended claims.

Claims

1. A peritoneal dialysis ("PD") system comprising: case; a PD fluid pump, the PD fluid pump being accommodated by the housing; an inline heater in fluid communication with the PD fluid pump; Temperature sensor; as well as a control unit, the PD fluid pump and the inline heater being under the control of the control unit, the control unit being configured to: receiving a temperature signal from the temperature sensor, and A thermal disinfection sequence is performed in which the control unit causes the PD fluid pump to pump disinfection fluid in a forward direction while the inline heater heats the disinfection fluid, and to pump the disinfection fluid in a reverse direction after the temperature signal indicates that the temperature of the disinfection fluid has dropped to a minimum disinfection temperature or has dropped below the minimum disinfection temperature.

2. The PD system according to claim 1, wherein: The control unit is configured to cause the PD fluid pump to pump the sterilization fluid in the reverse direction after the temperature signal indicates that the temperature of the sterilization fluid has dropped to or below the minimum sterilization temperature during a specified amount of time.

3. The PD system according to claim 1, wherein: When the PD fluid pump pumps the sterilizing fluid in the forward direction, the temperature sensor is located upstream of the inline heater.

4. The PD system according to claim 1, wherein: The temperature signal is used as closed loop feedback to the control unit for controlling the inline heater when the PD fluid pump pumps the sterilizing fluid in the reverse direction.

5. The PD system according to claim 1, wherein: The temperature sensor is a first temperature sensor, and the PD system includes a second temperature sensor, wherein the second temperature sensor is located downstream of the inline heater when the PD fluid pump pumps the disinfection fluid in the forward direction, and wherein the temperature signal from the second temperature sensor is used as closed-loop feedback to the control unit for controlling the inline heater when the PD fluid pump pumps the disinfection fluid in the forward direction.

6. The PD system according to claim 5, wherein: The inline heater is controlled such that the temperature of the sterilizing fluid exiting the inline heater is approximately 85°C.

7. The PD system according to claim 1, wherein: The control unit is configured to cause the PD fluid pump to pump the disinfecting fluid in the reverse direction for a plurality of pump strokes.

8. The PD system according to claim 1, wherein: The control unit is configured to cause the PD fluid pump to pump the disinfecting fluid in the reverse direction until a determined temperature is reached as indicated by the temperature sensor.

9. The PD system according to claim 1, wherein: The control unit is configured to cause the PD fluid pump to pump the disinfecting fluid in the reverse direction until a determined temperature is reached as indicated by the temperature sensor, followed by a plurality of pump strokes in the reverse direction.

10. The PD system according to claim 1, wherein: The thermal disinfection sequence is performed using a disinfection circuit comprising: a reusable patient line extending from the housing, the reusable patient line including a distal end configured to connect to a patient line connector provided by the housing; and At least one reusable PD fluid line extends from the housing, the at least one reusable PD fluid line including a distal end configured to connect to a PD fluid line connector provided by the housing.

11. The PD system according to claim 1, wherein: At least one of the following is met: (i) the minimum sterilization temperature is 65°C (149°F) to 95°C (203°F); or (ii) the sterilization fluid is a PD fluid.

12. A peritoneal dialysis ("PD") system comprising: case; a PD fluid pump, the PD fluid pump being accommodated by the housing; an inline heater in fluid communication with the PD fluid pump; Temperature sensor; as well as a control unit, the PD fluid pump and the inline heater being under the control of the control unit, the control unit being configured to: receiving a temperature signal from the temperature sensor, and executing a thermal disinfection sequence in which the control unit causes the PD fluid pump to pump disinfection fluid in a forward direction while the inline heater heats the disinfection fluid; and pumping the sterilizing fluid in a reverse direction, wherein the control unit controls the inline heater using a feed-forward algorithm that takes into account the temperature signal and the flow rate of the sterilizing fluid.

13. The PD system according to claim 12, wherein: The temperature signal provides a heater inlet temperature, and wherein the feed-forward algorithm subtracts the inlet temperature from a target temperature.

14. The PD system according to claim 12, wherein: The flow rate of the disinfecting fluid is calculated by the control unit by accumulating the known pump volumes pumped by the PD fluid pump.

15. The PD system of claim 12, comprising a flow meter in fluid communication with the PD fluid pump, and wherein: The flow rate of the disinfection fluid is measured by the flow meter.

16. The PD system according to claim 12, wherein: The feed-forward algorithm is constructed to calculate output power=(target temperature-inlet temperature obtained from the temperature signal) x (flow rate of the sterilizing fluid) x (specific heat capacity of water).

17. The PD system according to claim 16, wherein: The target temperature was 85°C.

18. The PD system according to claim 12, wherein: The temperature sensor is located downstream of the inline heater when the PD fluid pump pumps the sterilizing fluid in the forward direction, and wherein the temperature signal is used as closed-loop feedback to the control unit for controlling the inline heater when the PD fluid pump pumps the sterilizing fluid in the forward direction.

19. The PD system according to claim 12, wherein: The control unit is configured to cause: (i) the PD fluid pump to pump the disinfecting fluid in the forward direction for a plurality of pump strokes, and (ii) the PD fluid pump to automatically reverse direction and pump the disinfecting fluid in the reverse direction for a plurality of pump strokes.

20. The PD system according to claim 19, wherein: The control unit is further configured to repeat (i) and (ii) until a total disinfection time is reached.

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