Dialysis system with pump reversal disinfection

Abstract

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

Description

[Technical Field]

[0001] background FIELD OF THE DISCLOSURE The present disclosure relates generally to medical fluid treatments, and more particularly to dialysis fluid treatments that require pumping of patient infusible fluids. [Background technology]

[0002] A variety of causes can cause a person's renal system to fail. Renal failure results in several physiological disturbances: the kidneys are 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 others, can accumulate in the patient's blood and tissues.

[0003]

[0003] Declining kidney function, particularly kidney failure, is treated by dialysis, which removes waste products, toxins, and excess water from the body that normally would be removed by normally functioning kidneys. Dialysis treatment for kidney function replacement is vital for many people because the treatment is life-saving.

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

[0005] Hemofiltration ("HF") is another renal replacement therapy that relies on convective transport of toxins from the patient's blood. HF is achieved by adding replacement or substitution fluid to the extracorporeal circuit during treatment. The replacement fluid, and fluid accumulated by the patient between treatments, is ultrafiltered during HF treatment, providing a convective transport mechanism that is particularly useful for removing middle 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, replacement solution is provided directly to the extracorporeal circuit to provide convective clearance.

[0007] Most HD, HF, and HDF treatments are performed in facilities. Today, there is a trend toward home hemodialysis ("HHD"), in part because HHD can be performed daily, offering therapeutic benefits over in-center hemodialysis treatments, which are typically performed twice 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 receiving less frequent but potentially longer treatments. Patients receiving more frequent treatments do not experience as much downcycling (fluid and toxin fluctuations) as in-center patients who accumulate two or three days' worth of toxins before treatment. In certain areas, the nearest dialysis facility may be many miles from a patient's home, resulting in door-to-door treatment times consuming a significant portion of a patient's day. Treatments at facilities closer to the patient's home may also consume a significant portion of a patient's day. HHD can be performed at night or during the day when the patient is relaxing, working, or otherwise productive.

[0008] Another type of renal failure therapy is peritoneal dialysis ("PD"), in which a dialysis solution, also called dialysis fluid, is infused through a catheter into a patient's peritoneal cavity. The dialysis fluid contacts the peritoneal membrane within the patient's peritoneal cavity. Waste, toxins, and excess water enter the dialysis fluid from the patient's bloodstream through the peritoneal capillaries by diffusion and osmosis, creating an osmotic gradient across the membrane. An osmotic agent in the PD dialysis fluid provides the osmotic gradient. Spent or spent dialysis fluid is pumped out of the patient, removing the waste, toxins, and excess water from the patient. This cycle may be 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 flow dialysis, and continuous flow peritoneal dialysis ("CFPD"). CAPD is a manual dialysis treatment. In this, a 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's catheter is in communication with a bag of fresh dialysis fluid, infusing the patient with fresh dialysis fluid through the catheter. The patient disconnects the catheter from the bag of fresh dialysis fluid, allowing the dialysis fluid to dwell in the peritoneal cavity, where it transfers waste, toxins, and excess water. After the dwell period, the patient repeats the manual dialysis procedure, for example, four times a day. Manual peritoneal dialysis requires significant patient time and effort and leaves significant room for improvement.

[0010] Automated peritoneal dialysis ("APD") is similar to CAPD in that the dialysis treatment includes a drain cycle, a fill cycle, and a dwell cycle. However, automated PD machines perform these cycles automatically, typically while the patient sleeps. PD machines relieve patients of the need to manually perform treatment cycles and transport supplies during the day. PD machines are fluidly connected to an implanted catheter, a source or bag of fresh dialysis fluid, and a fluid drain. PD machines pump fresh dialysis fluid from the dialysis fluid source through the catheter and into the patient's peritoneal cavity. PD machines also allow the dialysis fluid to dwell within the cavity, allowing for the transfer of waste, toxins, and excess water. The source may contain multiple liters of dialysis fluid, including several solution bags.

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

[0012] In all of the above modalities, automated machines and even manual CAPD typically operate with disposable sets, which 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. Furthermore, daily disposables require storage space, which can be cumbersome for homes and businesses. Furthermore, changing daily disposables requires time and effort from patients and caregivers to set up each day at home or in the clinic.

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

[0014] overview The present disclosure describes an automated peritoneal dialysis ("PD") system that provides one or more PD treatment improvements. The system includes a PD device or cycler. The PD device can deliver fresh, heated PD fluid to a patient, for example, at 14 kPa (2.0 psig) or higher. The PD device can remove spent PD fluid or waste fluid from a patient, for example, at -5 kPa (-0.73 psig) to -15 kPa (-2.2 psig), e.g., -9 kPa (-1.3 psig) or higher. Fresh PD fluid can be delivered to a patient via a dual-lumen patient line and is first heated to body fluid temperature, e.g., 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 set, which is connected to a patient transfer set, which is connected to an indwelling catheter leading to the patient's peritoneal cavity. The disposable filter set is in fluid communication with the fresh and spent PD fluid lumens of the dual-lumen patient line. A disposable filter set is provided in one embodiment as a last-opportunity filter for the PD device that can be heat disinfected between treatments.

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

[0016] In one embodiment, the control unit may direct the PD fluid pump and system valves to move heated PD fluid in the normal treatment direction at the start of a thermal disinfection sequence. The heated PD fluid splits as needed to flow through the disinfection loop before returning to the in-line heater. The length of the internal reusable tubing and flexible reusable PD fluid line between the in-line heater outlet and the inlet of in-line heater 56 may be 10 meters or more. Heat loss occurs over the length of the line. Therefore, a potential problem may arise where the temperature of the PD fluid entering the in-line heater falls below what is considered a threshold minimum disinfection temperature, while the PD fluid exiting the in-line heater is at a temperature sufficient to produce the desired amount of disinfection.

[0017] In one example, a control unit, under feedback from a downstream temperature sensor, energizes the in-line heater so that the PD fluid exiting the heater is at or about 85°C. In one embodiment, 85°C (185°F) is the desired output temperature because it is above the recommended minimum disinfection temperature, e.g., 75°C (167°F), and 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 in-line heater falls below the recommended minimum disinfection temperature, e.g., 75°C, corrective action must be taken. Corrective action may include increasing the heater outlet temperature, increasing the disinfection time, or some combination of both. However, increasing the heater outlet temperature above 85°C risks boiling the PD fluid, while increasing the disinfection time increases wear on components. It should be understood that the minimum disinfection temperature can vary, e.g., from 65°C (149°F) to 95°C (203°F).

[0018] The present system and its associated methodology instead solve the potential low-temperature problem by programming the control unit to automatically reverse the pumping direction of the PD fluid pump one or more times during the disinfection sequence so that freshly heated PD fluid, e.g., at or about 85°C, is output from what is typically the heater inlet of the in-line heater. As described in detail below, in one embodiment, the in-line heater is bidirectional. Reversing the pumping direction of the PD fluid pump one or more times during the disinfection sequence results in a more even distribution of the newly heated PD fluid, e.g., to 85°C. Here, the hotter newly heated PD fluid mixes with the cooler PD fluid returning to the in-line heater, thereby raising the temperature of the combined PD fluid above the recommended minimum disinfection temperature, e.g., 75°C. More even distribution of the newly heated PD fluid helps eliminate pockets of closed disinfection loops that may fall below the recommended minimum disinfection temperature. More even distribution of the newly heated PD fluid also helps reduce the time required for the disinfection sequence. For example, the disinfection sequence time can be reduced by nearly half, from two hours to one hour.

[0019] In one method for controlling pump reversal during thermal disinfection of the present disclosure, the control unit monitors the output of a temperature sensor positioned to sense the temperature of the heated PD fluid re-entering the in-line heater. In one embodiment, the control unit determines whether the temperature of the PD fluid re-entering the in-line heater falls below the recommended minimum disinfection temperature, e.g., 75°C, for a specified or threshold time, e.g., 60 seconds. Including the specified or threshold time in the analysis allows the PD fluid temperature at the heater inlet to fall below the recommended minimum disinfection temperature for a short period of time or inadvertently without overreacting to temporary temperature drops. It is contemplated that the threshold time can be optimized to allow for a more lenient system, e.g., longer than 1 minute, or a more strict version of the system, e.g., 5-60 seconds.

[0020] When the temperature of the PD fluid re-entering the in-line heater drops below the recommended minimum disinfection temperature for a threshold time, the control unit reverses the PD fluid pump and pumps in the opposite direction. It is contemplated that the control unit may control the amount or time the PD fluid pump pumping is reversed in several different ways. In one method, the control unit causes the PD fluid pump to pump in the reverse direction for a certain number of pump strokes, e.g., 100 pump strokes. In a second method, the control unit causes the PD fluid pump to pump in the reverse direction until a specific temperature is reached at a downstream temperature sensor during pump reversal. In a third method, the control unit causes the PD fluid pump to pump in the reverse direction until a specific temperature is reached at a downstream temperature sensor during pump reversal, after which a preset number of additional pump strokes are performed in the reverse pumping direction. The control unit repeats the above sequence until the total disinfection time is reached.

[0021] In a second alternative method, a temperature sensor located immediately upstream of the heater may not be required, which is advantageous for reducing costs, eliminating sensors that may require occasional calibration, and eliminating parts that may need to be replaced. Here, the control unit causes the PD fluid pump to pump in the forward or normal treatment direction for a preset number of pump strokes, e.g., 100 pump strokes. After the preset number of pump strokes in the treatment direction are completed, the control unit automatically reverses the PD fluid pump and causes it to pump in the opposite direction for a preset number of pump strokes, e.g., 100 pump strokes. The control unit repeats the above sequence until the total disinfection time is reached.

[0022] The system and associated methodology may use a closed-loop heater control algorithm or a 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, e.g., 85°C or approximately 85°C. The control unit calculates the error between the commanded 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, e.g., a PID heating algorithm. The output from the heating algorithm is used by the control unit to determine the amount of power to deliver to the in-line heater. The just-described cycle is repeated at a processing frequency.

[0023] 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, e.g., 85°C. The control unit also determines (calculate or measure) the current PD fluid flow rate. If a piston pump is used as the PD fluid pump and no flow meter is provided, the control unit calculates the current flow rate by accumulating pump strokes of known volumes pumped by the PD fluid pump and dividing the accumulated volume by the time required to accumulate the 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 a feedforward heater algorithm. The output from the feedforward heater algorithm (or its derivative or correlation) is used by the control unit to determine the amount of current or power to deliver to the in-line heater. The just-described cycle is repeated at some processing frequency.

[0025] In light of the disclosure set forth herein, in a first aspect of the present disclosure, which does not limit the present disclosure in any way but which may be combined with any other aspect or portion thereof, a peritoneal dialysis ("PD") system includes a housing; a PD fluid pump contained by the housing; an in-line heater in fluid communication with the PD fluid pump; a temperature sensor; and a control unit, wherein the PD fluid pump and the in-line heater are under the control of the control unit, the control unit receiving a temperature signal from the temperature sensor, and the control unit performing a thermal disinfection sequence, wherein the control unit is configured to: cause the PD fluid pump to pump disinfectant fluid in a forward direction while the in-line heater heats the disinfectant fluid, and to pump in a reverse direction after the temperature signal indicates that the temperature of the disinfectant fluid has dropped to or below a 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 disinfectant fluid in a reverse direction after the temperature signal indicates that the temperature of the disinfectant fluid has decreased to or below a minimum disinfection temperature for a specified time.

[0027] In a third aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the temperature sensor is positioned upstream of the in-line heater when the PD fluid pump is pumping disinfectant fluid in the forward direction.

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

[0029] In a fifth aspect of the present disclosure that may be combined with any other aspect or portion thereof, the temperature sensor is a first temperature sensor and includes a second temperature sensor positioned downstream of the in-line heater when the PD fluid pump is pumping the disinfectant fluid in the forward direction, and a temperature signal from the second temperature sensor is used as closed-loop feedback to the control unit to control the in-line heater when the PD fluid pump is pumping the disinfectant fluid in the forward direction.

[0030] In a sixth aspect of the present disclosure that may be combined with any other aspect or portion thereof, the in-line heater is controlled so that the temperature of the disinfectant fluid exiting the in-line heater is about 85°C.

[0031] In a seventh aspect of the present disclosure that may be combined with any other aspect or a portion thereof, the control unit is configured to cause the PD fluid pump to pump disinfecting fluid in a reverse direction for a number 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 disinfectant fluid in the reverse direction until it reaches a certain temperature indicated by a temperature sensor.

[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 disinfectant fluid in the reverse direction until a certain temperature indicated by a temperature sensor is reached, and then to pump disinfectant fluid in the reverse direction for a certain number of pump strokes.

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

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

[0036] In a twelfth aspect of the present disclosure that may be combined with any other aspects or portions thereof, a peritoneal dialysis ("PD") system includes a housing, a PD fluid pump contained by the housing, an in-line heater in fluid communication with the PD fluid pump, a temperature sensor, and a control unit, wherein the PD fluid pump and the in-line heater are under the control of the control unit, the control unit configured to receive a temperature signal from the temperature sensor and perform a thermal disinfection sequence, wherein in the thermal disinfection sequence the control unit causes the PD fluid pump to pump disinfectant fluid in a forward direction while the in-line heater heats the disinfectant fluid and in a reverse direction wherein the control unit controls the in-line heater using a feedforward algorithm that takes into account the temperature signal and a flow rate of the disinfectant fluid.

[0037] In a thirteenth aspect of the present disclosure that may be combined with any other aspect or portion thereof, the temperature signal provides a heater inlet temperature, and the feedforward algorithm subtracts the inlet temperature from the 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 that may be combined with any other aspect or a portion thereof, the PD system includes a flow meter in fluid communication with the PD fluid pump, and 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 temperature signal) x (disinfection fluid flow rate) x (specific heat of water).

[0041] In a seventeenth aspect of the present disclosure that may be combined with any other aspect or 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, a temperature sensor is positioned downstream of the in-line heater when the PD fluid pump is pumping disinfectant fluid in a forward direction, and the temperature signal is used as closed-loop feedback to the control unit to control the in-line heater when the PD fluid pump is pumping disinfectant fluid in a forward direction.

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

[0044] In a twentieth aspect of the present disclosure that 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 which may be combined with any other aspect or portion thereof, any of the features, functions, and alternatives described in connection with any one or more of Figures 1, 2, 4 to 8 may be combined with any of the features, functions, and alternatives described in connection with any other of Figures 1, 2, 4 to 8.

[0046] In light of the above aspects and the present disclosure described 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 with thermal disinfection with fewer or no pockets of low temperature disinfecting fluid.

[0048] A further advantage of the present disclosure is that it provides a PD system and method with reduced disinfection times.

[0049] Additional features and advantages are described in and will be apparent from the following detailed description and drawings. The features and advantages described herein are not all-inclusive, and in particular, many additional features and advantages will be apparent to those skilled in the art in view of the drawings and description. Moreover, any particular embodiment need not possess all of the improvements or advantages described herein; it is expressly contemplated that each advantageous embodiment may be separately claimed. In particular, the disclosed system may have any one or more or all of the drip prevention structures and techniques, PD fluid container emptying structures and techniques, and patient connection confirmation structures and techniques before draining described herein. Furthermore, it should be noted that the language used herein has been chosen primarily for purposes of readability and explanation, and not to limit the scope of the inventive subject matter. [Brief explanation of the drawings]

[0050] [Figure 1] 1 is a fluid flow schematic diagram of one embodiment of a medical fluid system, such as a PD fluid system, configured for treatment.

[0051] [Figure 2] 2 is a schematic diagram of fluid flow in one embodiment of the medical fluid system of FIG. 1, for example, a PD fluid system, reconfigured for disinfection.

[0052] [Figure 3] 10 includes plots showing in-line heater inlet temperature versus in-line heater outlet temperature with and without pump reversal disinfection of the present disclosure.

[0053] [Figure 4] FIG. 1 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] FIG. 10 is a process flow diagram illustrating another embodiment for reversing the flow of heated PD fluid during a disinfection sequence of the present disclosure.

[0055] [Figure 6] 1 illustrates a partial fluid path showing an in-line heater and temperature sensor for closed-loop control that may be used for both forward and reverse PD fluid disinfection flow.

[0056] [Figure 7] 1 illustrates a partial fluid path showing an in-line heater and upstream temperature sensor for the open-loop forward heating control algorithm used during reverse PD fluid disinfection flow.

[0057] [Figure 8] 1 includes plots showing in-line heater inlet and outlet temperatures over time and illustrating the effect of pump reversal disinfection of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0058] Detailed Description System Overview Referring now to the drawings, and particularly to FIG. 1 , a medical system with pump reversal thermal disinfection of the present disclosure is illustrated by a peritoneal dialysis (“PD”) system 10. System 10 includes a PD device 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. User interface 108 may alternatively or additionally be a remote user interface, e.g., via a tablet or smartphone. Control unit 100 may also include a transceiver and a wired or wireless connection to a network (not shown), e.g., the Internet, for transmitting treatment data to and receiving prescription orders / changes from a physician or clinician server that interfaces with a physician or clinician's computer. In one embodiment, control unit 100 controls all electrical fluid flow and heating components of system 10 and receives outputs from all sensors in system 10. The system 10 in the illustrated embodiment includes durable, reusable components that come into contact with unused and used PD fluid, requiring the PD device or cycler 20 to be disinfected between treatments, e.g., by thermal disinfection.

[0059] System 10 of FIG. 1 includes an in-line resistance heater 56, reusable supply lines or tubes 52a1-52a4 and 52b, an air trap 60 operating in conjunction with upper and lower level sensors 62a and 62b, respectively, an air trap valve 54d, a vent valve 54e positioned along vent line 52e, a reusable line or tube 52c, a PD fluid pump 70, temperature sensors 58a and 58b, an optional third temperature sensor 58c, and pressure sensors 78a, 78b. , 78b2, and 78c, reusable patient tubing or lines 52f and 52g with respective valves 54f and 54g, dual lumen patient line 28, hose reel 80 for retracting patient line 28, reusable drain tubing or line 52i extending to drain line connector 34 and having drain line valve 54i, and reusable recirculation disinfection tubing or lines 52r1 and 52r2 operating with disinfection valves 54r1 and 54r2, respectively. A third recirculation or disinfection tubing or line 52r3 extends between disinfection or PD fluid line connectors 30a and 30b for use during disinfection. A fourth recirculation or disinfection tubing or line 52r4 extends between disinfection connectors 30c and 30d for use during disinfection.

[0060] System 10 further includes PD fluid containers or bags 38a-38c (e.g., holding the same or different formulations of PD fluid) that connect to distal ends 24e of reusable PD fluid lines 24a-24c, respectively. System 10d further includes a fourth PD fluid container or bag 38d that connects to distal ends 24e of reusable PD fluid line 24d. Fourth PD fluid container or bag 38d may hold the same or a different type of PD fluid (e.g., icodextrin) as provided in PD fluid containers or bags 38a-38c. Reusable PD fluid lines 24a-24d, in one embodiment, extend through openings (not shown) defined or provided by housing 22 of cycler 20.

[0061] In the illustrated embodiment, system 10 includes four disinfection or PD fluid line connectors 30a-30d for connection to the distal ends 24e of reusable PD fluid lines 24a-24d, respectively, during disinfection. System 10 also provides a patient line connector 32 including an internal lumen, e.g., a U-shaped lumen, that conducts unused or used dialysis fluid from one PD fluid lumen to the other PD fluid lumen of the connected distal end 28e of dual-lumen patient line 28 for disinfection. Reusable supply tubes or lines 52a1-52a4 communicate with reusable supply lines 24a-24d, respectively. Reusable supply tubes or lines 52a1-52a3 operate with valves 54a-54c, respectively, to allow PD fluid to be drawn into cycler 20 from desired PD fluid containers or bags 38a-38c. Three-way valve 94a in the illustrated example allows 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 illustrated embodiment, icodextrin from container or bag 38d is connected to a normally closed port of three-way valve 94a.

[0062] System 10, in one embodiment, is configured such that drain line 52i during patient fill is fluidly connected downstream of PD fluid pump 70. In this way, if drain valve 54i fails or somehow leaks during patient fill of patient P, unused PD fluid is forced into disposable drain line 36 instead of potentially drawing used PD fluid into pump 70. Disposable drain line 36, in one embodiment, is removed for sanitization, and drain line connector 34 is capped via cap 34c, forming a closed sanitization loop. PD fluid pump 70 may be an inherently precise pump, such as a piston pump, or a less precise pump, such as a gear pump, that operates in conjunction with a flow meter (not shown) to control the flow rate and volume of unused and used PD fluid.

[0063] System 10 may further include a leak detection pan 82 positioned at the bottom of housing 22 of cycler 20 and a corresponding leak detection sensor 84 that outputs to control unit 100. In the illustrated example, system 10 is provided with an additional pressure sensor 78c positioned upstream of PD fluid pump 70, which allows measurement of the suction pressure of pump 70 and helps control unit 100 more accurately determine pump volume. The additional pressure sensor 78c in the illustrated embodiment is positioned along vent line 52e, which may be filled with air or a mixture of air and PD fluid, but which should nevertheless be at the same negative pressure as the PD fluid positioned in PD fluid line 52c.

[0064] 1 includes redundant pressure sensors 78b1 and 78b2, one output of which is used for pump control as described herein, and the other pressure sensor output is a safety or watchdog output to ensure the control pressure sensor is reading accurately. Pressure sensors 78b1 and 78b2 are positioned along a line that includes third recirculation valve 54r3. System 10 may use one or more crosses, marked with an X in FIG. 1, which may (i) reduce the overall amount and volume of reusable internal tubing, (ii) reduce the number of valves required, and (iii) minimize the portion of the fluid circuit shared by both unused and used PD fluid.

[0065] 1 further 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 a second three-way valve 94b via a citric acid valve 54m positioned along a citric acid line 52m. The citric acid line 52m, in one embodiment, is connected to a 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 citric (or other) acid does not reach the treatment fluid line during treatment. Instead, citric (or other) acid is used during disinfection.

[0066] In one embodiment, control unit 100 uses feedback from any one or more of pressure sensors 78a-78c to enable PD device 20 to deliver fresh, heated PD fluid to the patient, for example, at 14 kPa (2.0 psig) or greater. Pressure feedback is used to enable PD device 20 to remove spent PD fluid or drainage from the patient, for example, at between -5 kPa (-0.73 psig) and -15 kPa (-2.2 psig), for example, -9 kPa (-1.3 psig) or greater (more negative). Pressure feedback can be used in proportional, integral, derivative ("PID") pressure routines to pump fresh and spent PD fluid at desired positive or negative pressures.

[0067] An in-line resistive heater 56 under the control of the control unit 100 can heat the virgin PD fluid to body temperature, e.g., 37°C, for delivery to the patient P at a desired flow rate. In one embodiment, the control unit 100 uses feedback from the temperature sensor 58a in a PID temperature routine to pump the virgin PD fluid to the patient P at the desired temperature. The control and operation of the in-line resistive heater 56 for thermal disinfection is described in detail below.

[0068] 1 also illustrates that system 10 includes and uses a disposable filter set 40 in fluid communication with the unused and used PD fluid lumens of dual-lumen patient line 28. Disposable filter set 40 includes a disposable connector 42 that connects to the distal end 28e of reusable patient line 28. Disposable filter set 40 also includes a connector 44 that connects to the patient's transfer set. Disposable filter set 40 further includes a sterilizing-grade filter membrane 46 that further filters the unused PD fluid. In one embodiment, disposable filter set 40 serves as a last-resort filter for PD device 20 and is heat-sterilized between treatments. Pathogens that may remain after sterilization, although unlikely, are filtered from the PD fluid via sterilizing-grade filter membrane 46 of disposable filter set 40.

[0069] FIG. 1 illustrates the configuration of system 10 for treatment with PD fluid containers or bags 38a-38d connected via reusable flexible PD fluid lines 24a-24d, respectively. Dual-lumen patient line 28 is connected to patient P via disposable filter set 40. Disposable drain line 36 is connected to drain line connector 34. In FIG. 1, PD device or cycler 20 of system 10 is configured to perform multiple patient drain, patient fill, patient dwell, and priming procedures as part of treatment or in preparation for treatment.

[0070] FIG. 2 illustrates system 10 in a disinfection mode. PD fluid containers or bags 38a-38d are removed and, instead, flexible PD fluid lines 24a-24d are sealingly inserted into disinfection or PD fluid line connectors 30a-30d, respectively. Reusable dual-lumen patient line 28 is disconnected from disposable filter set 40 (which is discarded), and the distal end 28e of dual-lumen patient line 28 is sealingly inserted into patient line connector 32. Disposable drain line 36 is removed from drain line connector 34 and discarded. Drain line connector 34 is capped via cap 34c, forming a closed disinfection loop 90. PD device or cycler 20 of system 10 of FIG. 2 is configured to perform a disinfection sequence, e.g., a thermal disinfection sequence, in which unused PD fluid is heated via in-line heater 56 to a disinfection temperature, e.g., 75°C or higher. The PD fluid pump 70 circulates a closed disinfection loop 90 of heated PD fluid for the amount of time necessary to adequately disinfect the fluid components and lines of the disinfection loop.

[0071] Pump Reversal Heat Disinfection In one embodiment, at the start of a thermal disinfection sequence, control unit 100 causes PD fluid pump 70 and the valves of system 10 to move heated PD fluid in the normal treatment direction, e.g., from left to right across PD fluid pump 70 in FIG. 2 . The heated PD fluid may be split between unused patient tubing or line 52f and drain tubing or line 52i. The flow of heated PD fluid splitting through unused patient tubing or line 52f flows through an unused PD lumen in dual-lumen patient line 28, a used PD lumen in dual-lumen patient line 28, used patient tubing or line 52g, and tubing or line 52c, and returns to PD fluid pump 70. The flow of heated PD fluid splitting through unused patient tubing or line 52f also splits further into lines containing pressure sensors 78b1 and 78b2 and a third recirculation valve 54r3 before joining the flow of heated PD fluid through recirculation line 52r1.

[0072] The heated PD fluid flow splits through drain tubing or line 52i and flows through drain line connector 34, recirculation tubing or line 52r2, recirculation tubing or line 52r1, reusable flexible PD fluid lines 24a-24d, tubing or lines 52a1-52a4, recirculation tubing or lines 52r3 and 52r4, and back to the inlet of in-line heater 56. The length of the internal reusable tubing and reusable flexible PD fluid lines 24a-24d between the outlet of in-line heater 56 and the inlet of in-line heater 56 may be 10 meters or more. Heat loss occurs over the length of the line. Thus, a potential problem may arise where the temperature of the PD fluid returning to in-line heater 56 is below what is considered a threshold minimum disinfection temperature while the PD fluid exiting in-line heater 56 is at a temperature sufficient to produce the desired amount of disinfection.

[0073] In one example, the control unit 100, under feedback from the temperature sensor 58a, energizes the in-line heater 56 so that the PD fluid exiting the heater is at or about 85°C. In one embodiment, 85°C (185°F) is a desirable output disinfection temperature because it is above the recommended minimum disinfection temperature, e.g., 75°C (167°F), and 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 in-line heater 56 falls below the recommended minimum disinfection temperature, e.g., 65°C (149°F) to 95°C (203°F), e.g., 75°C (167°F), corrective action must be taken. Figure 3 includes a plot illustrating the temperature of the heater inlet 56i versus the temperature of the heater outlet 56o without 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), remaining above the recommended minimum sanitization temperature of, for example, 75°C (167°F), while the temperature at the inlet 56i of the heater 56 approaches, but remains below, 70°C (158°F). Thus, the temperature at the inlet 56i of the heater 56 is likely to fall below the recommended minimum sanitization temperature of, for example, 75°C (167°F). In the illustrated embodiment, the time varies in minutes.

[0074] Corrective actions for increasing the temperature of the heater 56 inlet 56i illustrated in FIG. 3 may include increasing the heater outlet temperature, increasing the disinfection time, or some combination of both. However, increasing the heater outlet temperature above 85°C risks causing the PD fluid to begin boiling, while increasing the disinfection time increases component wear. Instead, the system 10 and associated methodology 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 disinfection sequence so that freshly 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. It may be possible to use an inline heater 56 that is not bidirectional. Here, control unit 100 may cause the PD fluid to be heated in the normal direction for a desired number of pump strokes to a desired controlled temperature, and then cause PD fluid pump 70 to pump in the reverse direction for the same desired number of pump strokes to force the newly heated PD fluid out heater inlet 56i. During reverse pumping, in-line heater 56 may or may not be powered.

[0075] Reversing the pumping direction of the PD fluid pump 70 one or more times during the disinfection sequence results in a more even distribution of the freshly heated PD fluid, e.g., to 85°C. The hotter freshly heated PD fluid then mixes with the cooler PD fluid returning to the in-line heater 56, thereby raising the temperature of the combined PD fluid above the recommended minimum disinfection temperature, e.g., 75°C. The more even distribution of the freshly heated PD fluid helps eliminate pockets in the closed disinfection loop 90 that may fall below the recommended minimum disinfection temperature. The more even distribution of the freshly heated PD fluid also helps reduce the time required for the disinfection sequence. For example, the time for a disinfection sequence can be reduced by nearly half, from two hours to one hour, using the pump-reversal heating PD fluid disinfection of the present disclosure.

[0076] FIG. 4 illustrates one method 110 that may be implemented by the control unit 100 for controlling pump reversal during thermal disinfection of the present disclosure. At oval 112, the method 110 begins. At block 114, the control unit 100 opens all two-way valves associated with the disinfection loop 90 and operates the PD fluid pump 70 in a forward treatment direction (from left to right through the pump 70 in FIGS. 1 and 2), which may also be considered the normal disinfection sequence direction. At block 114, the control unit 100 also controls the in-line heater 56 using feedback from the temperature sensor 58a and a heating algorithm, such as a proportional-integral-derivative ("PID") heating algorithm, to output heated PD fluid at the heater outlet 56o at a desired disinfection temperature, such as 85°C.

[0077] At block 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 in-line 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 in-line heater 56 at the heater inlet 56i, as indicated by the temperature sensor 58c, has fallen below a recommended minimum disinfection temperature, e.g., 75°C, for a threshold or specified time, e.g., 60 seconds. Including the threshold time in the query at diamond 118 allows the PD fluid temperature at the heater inlet 56i to fall below the recommended minimum disinfection temperature for a short period of time or inadvertently without overreacting to a temporary drop in temperature. It is contemplated that the threshold time may be optimized to allow for a more lenient version of the method 110, e.g., longer than 1 minute, or a more strict version of the method 110, e.g., 5-60 seconds.

[0078] If the temperature of the PD fluid re-entering the in-line heater 56 at the heater inlet 56i has not fallen below the recommended minimum disinfection temperature for the threshold time, as determined by diamond 118, then the control unit 100 determines whether the total disinfection sequence time has been reached, at diamond 120. Proper disinfection of the disinfection loop 90 involves movement of PD fluid heated to or above the recommended minimum disinfection temperature through the disinfection loop 90 for a specified period of time, e.g., two hours. Once the total disinfection time or the specified disinfection time has been reached, as determined by diamond 120, the disinfection sequence is complete and the method 110 ends at oval 122.

[0079] If, at diamond 120, the total disinfection time or the specified disinfection time has not been reached, the method 110 returns to block 114 as illustrated in Figure 4. The just-described loop between block 114 and diamond 120 is repeated until either the total disinfection time or the specified disinfection time is reached (at diamond 120) or until the temperature of the PD fluid re-entering the in-line heater 56 at heater inlet 56i falls below the recommended minimum disinfection temperature for a threshold time (at block 118).

[0080] When the temperature of the PD fluid re-entering the in-line heater 56 at the heater inlet 56i drops below the recommended minimum disinfection temperature for a threshold time in block 118, the control unit 100 reverses the PD fluid pump 70 to pump in the opposite direction (from right to left in FIGS. 1 and 2 ) in block 124. The control unit 100 also sequences any of the valves in the disinfection loop 90 as needed, e.g., sequencing the three-way valve 94a. It is contemplated that the control unit 100 controls the amount or time that the pumping of the PD fluid pump 70 is reversed in a number of different ways. In one method, the control unit 100 causes the PD fluid pump 70 to pump in the reverse direction for a number of pump strokes, e.g., 100 pump strokes. In a second method, the control unit 100 causes the PD fluid pump 70 to pump in the reverse direction until a specific temperature, e.g., 85°C (the commanded output of the heater 56), is reached at the temperature sensor 58c, where the temperature sensor 58c is a downstream temperature sensor during the reverse pumping. In a third method, the control unit 100 causes the PD fluid pump 70 to pump in the reverse direction until a specific temperature, e.g., 85°C, is reached at the temperature sensor 58c, and then a preset number of pump strokes are performed in the reverse pumping direction.

[0081] Once the pumping reversal of the PD fluid pump 70 is completed by any of the methods previously described, the method 110 returns to block 114, as illustrated in FIG. 4. As described in connection with diamond 118 and block 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 to initiate pump reversal (diamond 118) and, potentially, in determining the time at which pump reversal is performed (block 124). The output of the temperature sensor 58c is also used as feedback to the control unit 100 to control the power supply to the in-line heater 56 while the pumping of the PD fluid pump 70 is reversed, so that a maximum temperature, e.g., 85°C, is not exceeded.

[0082] FIG. 5 illustrates an alternative method 130 in which the temperature sensor 58c positioned immediately upstream of the heater inlet 56i may not be necessary, which is advantageous for reducing costs, eliminating sensors that may require occasional calibration, and eliminating parts that may require replacement. The method 130 begins in block 132. In block 134, the control unit 100 opens all two-way valves associated with the disinfection loop 90. In block 134, the control unit 100 also controls the in-line heater 56 using feedback from the temperature sensor 58a and a heating algorithm, such as a proportional-integral-derivative ("PID") heating algorithm, to output heated PD fluid at the heater outlet 56o at a desired disinfection temperature, such as 85°C. In block 134, the control unit 100 causes the PD fluid pump 70 to pump in the normal treatment (forward) direction (from left to right through the pump 70 in FIGS. 1 and 2) for a preset number of pump strokes, e.g., 100 pump strokes.

[0083] In block 136, after a preset number of pump strokes in the treatment direction are completed, control unit 100 automatically reverses PD fluid pump 70 to pump in the opposite direction (from right to left in FIGS. 1 and 2 ). Control unit 100 also sequences any of the valves in disinfection loop 90 as needed, for example, sequencing three-way valve 94a. In one embodiment, control unit 100 causes PD fluid pump 70 to pump in the reverse direction for a preset number of pump strokes, for example, 100 pump strokes. As described below, in one embodiment, control unit 100 may use forward open-loop heater control during pump reversal in method 130, which does not require the use of temperature sensor 58c (closed-loop control using temperature sensor 58c can alternatively be implemented).

[0084] At diamond 138, after completing a preset number of pump strokes in the reverse direction, the control unit 100 determines whether the total disinfection sequence time has been reached. Proper disinfection of the disinfection loop 90 in method 130 again involves moving PD fluid heated to or above the recommended minimum disinfection temperature through the disinfection loop 90 for a specified period of time. If the total disinfection time or the specified disinfection time has not been reached, as determined at diamond 138, the method 130 returns to block 134. Once the total disinfection time or the specified disinfection time has been reached, as determined at diamond 138, the disinfection sequence is complete and the method 130 ends at oval 140.

[0085] Figure 6 illustrates one embodiment for using a downstream pressure sensor for closed-loop control that may be used in method 110 for both forward and reverse heated PD fluid sanitizing flow and method 130 for forward heated PD fluid sanitizing flow. Figure 6 illustrates a portion of sanitizing loop 90 having in-line heater 56, temperature sensor 58a with output to control unit 100, and temperature sensor 58c with output to control unit 100. In the forward direction, the output from temperature sensor 58a is used for feedback control. In the reverse direction, the output from temperature sensor 58c is used for feedback control.

[0086] 5 illustrates that the control unit 100 reads temperatures from the appropriate temperature sensors 58a, 58c for closed-loop control. The control unit 100 also stores a target temperature, e.g., 85°C. The control unit 100 calculates the error between the commanded or target temperature and the temperature read from the appropriate temperature sensor 58a, 58c. The control unit 100 then inputs the calculated error into a heating algorithm, e.g., a PID heating algorithm. The output from the heating algorithm is used by the control unit 100 to determine the amount of power to deliver to the in-line heater. The just-described cycle is repeated at some processing frequency.

[0087] For both methods 110 and 130, it should be understood that forward closed-loop control should very quickly produce a temperature reading at temperature sensor 58a in the commanded temperature range, e.g., 85°C. In method 100, which triggers reverse flow when temperature sensor 58c senses a low temperature for a certain period of time as described above, the same temperature sensor 58c subsequently used for closed-loop control initially reads a lower temperature corresponding to a mixture of hot PD fluid exiting in-line heater 56 in the reverse direction and cooler PD fluid present just upstream of heater inlet 56i. Here, a period of time occurs before temperature sensor 58c begins to read a temperature in the commanded temperature range, e.g., 85°C.

[0088] 7 illustrates an alternative method of controlling in-line heater 56 during reverse PD fluid flow that involves forward open-loop control and does not require temperature sensor 58c (which is absent in FIG. 7). Thus, forward open-loop heater control is suitable for the reverse PD fluid flow of method 130. The forward open-loop heater control of FIG. 7 used during the reverse PD fluid flow of method 130 uses the output from temperature sensor 58a to control unit 100. It should be understood that during reverse PD fluid flow, temperature sensor 58a is positioned upstream of heater outlet 56o of in-line heater 56.

[0089] 6 illustrates that for open-loop control, control unit 100 reads the temperature from temperature sensor 58a and stores a target temperature, e.g., 85°C. Control unit 100 also determines (calculates or measures) the current PD fluid flow rate. If a piston pump is used as PD fluid pump 70 and no flow meter is provided, control unit 100 calculates the current flow rate by accumulating pump strokes of known volumes pumped by PD fluid pump 70 and dividing the accumulated volume by the time required to accumulate the pump strokes. If a separate flow meter is provided instead (not shown in FIGS. 1 and 2), control unit 100 measures the flow rate by reading the output from the flow meter.

[0090] 7, control unit 100 inputs the temperature from temperature sensor 58a and the determined flow rate into a feedforward heater algorithm. The output from the feedforward heater algorithm (or its derivative or correlation) is used by control unit 100 to determine the amount of power to deliver to the in-line heater. The cycle just described is repeated at some processing frequency. In one example, the feedforward heater algorithm: Required heater output power = (target temperature - inlet temperature) x PD fluid flow rate x specific heat of water may be. In an example where the inlet temperature read by 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 of water is 4.184 (Joules / gram x °K), the required output power is (85 - 70) x 5 x 4.184, which equals 313.8 watts of heating power. In one embodiment, the control unit memory 104 stores a lookup table for the inline heater 56 that correlates the amount of current or heater inlet power required to achieve 313.8 watts of heating power (or the nearest stored power).

[0091] 8 illustrates two temperature plots over time, Ti and To, which are the temperature at the inlet 56i of the in-line heater 56 and the temperature at the outlet 56o of the in-line heater 56, respectively. A reversal of the PD fluid pump 70 during disinfection, triggered by the control unit 100, occurs, for example, at time t when a sudden increase in temperature occurs at the inlet 56i of the heater 56. rev The cessation of reversal of the PD fluid pump 70 during disinfection, triggered by the control unit 100 to instead pump in the normal direction again, occurs, for example, at time t norm8 occurs at 140°F (60°C). While the temperatures in both temperature plots Ti and To are shown to drop to approximately 140°F (60°C), likely below the minimum disinfection temperature, it should be understood that the power (or duty cycle) to heater 56 can be increased so that the minimum temperatures in temperature plots Ti and To do not fall below, or not significantly below, the minimum disinfection temperature, e.g., 167°F (75°C). In the illustrated embodiment, the time is varied in minutes. The significance of Figure 8 is that it shows that pump reversal has a significant and immediate effect on the temperature at the inlet 56i of in-line heater 56.

[0092] 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, and it is therefore intended that such changes and modifications be covered by the appended claims.

Claims

1. 1. A peritoneal dialysis ("PD") system comprising: Housing and a PD fluid pump contained by the housing; an in-line heater in fluid communication with the PD fluid pump; A temperature sensor; a control unit, wherein the PD fluid pump and the in-line heater are under the control of the control unit, the control unit comprising: receiving a temperature signal from the temperature sensor; executing a thermal disinfection sequence, wherein the control unit causes the PD fluid pump to pump the disinfectant fluid in a forward direction while the in-line heater heats the disinfectant fluid, and in a reverse direction after the temperature signal indicates that the temperature of the disinfectant fluid has dropped to or below a minimum disinfection temperature; a control unit configured to A PD system comprising:

2. 2. The PD system of claim 1, wherein the control unit is configured to cause the PD fluid pump to pump the disinfectant fluid in the reverse direction after the temperature signal indicates that the temperature of the disinfectant fluid has decreased to or below the minimum disinfection temperature for a specified time.

3. The PD system of claim 1 , wherein the temperature sensor is positioned upstream of the in-line heater when the PD fluid pump is pumping the disinfecting fluid in the forward direction.

4. 2. The PD system of claim 1, wherein the temperature signal is used as closed-loop feedback to the control unit to control the in-line heater when the PD fluid pump is pumping the disinfectant fluid in the reverse direction.

5. 2. The PD system of claim 1, wherein the temperature sensor is a first temperature sensor and includes a second temperature sensor positioned downstream of the in-line heater when the PD fluid pump is pumping the disinfectant fluid in the forward direction, and a temperature signal from the second temperature sensor is used as closed-loop feedback to the control unit to control the in-line heater when the PD fluid pump is pumping the disinfectant fluid in the forward direction.

6. 6. The PD system of claim 5, wherein the in-line heater is controlled so that the temperature of the disinfectant fluid exiting the in-line heater is about 85°C.

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

8. 10. The PD system of 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 specific temperature indicated by the temperature sensor is reached.

9. 2. The PD system of 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 specific temperature indicated by the temperature sensor is reached, and then to pump the disinfecting fluid in the reverse direction for a number of pump strokes.

10. The thermal disinfection sequence is performed using a disinfection loop, the disinfection loop 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 extending 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; and The PD system of claim 1 , comprising:

11. 10. The PD system of claim 1, wherein at least one of: (i) the minimum disinfection temperature is between 65°C (149°F) and 95°C (203°F); or (ii) the disinfecting fluid is a PD fluid.

12. 1. A peritoneal dialysis ("PD") system comprising: Housing and a PD fluid pump contained by the housing; an in-line heater in fluid communication with the PD fluid pump; A temperature sensor; a control unit, wherein the PD fluid pump and the in-line heater are under the control of the control unit, the control unit comprising: receiving a temperature signal from the temperature sensor; executing a thermal disinfection sequence, wherein the control unit causes the PD fluid pump to pump the disinfectant fluid in a forward direction while the in-line heater heats the disinfectant fluid, and in a reverse direction wherein the control unit controls the in-line heater using a feed-forward algorithm that takes into account the temperature signal and the disinfectant fluid flow rate; a control unit configured to A PD system comprising:

13. The PD system of claim 12 , wherein the temperature signal provides a heater inlet temperature and the feedforward algorithm subtracts the inlet temperature from a target temperature.

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

15. 13. The PD system of claim 12, including a flow meter in fluid communication with the PD fluid pump, wherein the flow rate of the disinfecting fluid is measured by the flow meter.

16. 13. The PD system of claim 12, wherein the feedforward algorithm is configured to calculate output power = (target temperature - inlet temperature obtained from the temperature signal) x (the disinfection fluid flow rate) x (specific heat of water).

17. The PD system of claim 16 , wherein the target temperature is 85° C.

18. 13. The PD system of claim 12, wherein the temperature sensor is positioned downstream of the in-line heater when the PD fluid pump is pumping the disinfectant fluid in the forward direction, and the temperature signal is used as closed-loop feedback to the control unit to control the in-line heater when the PD fluid pump is pumping the disinfectant fluid in the forward direction.

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

20. 20. The PD system of 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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