Dialysis system with filter testing

Abstract

A peritoneal dialysis ("PD") system includes: a housing; a PD fluid pump housed by the housing; a filter kit comprising a filter housing and a hydrophilic filtration membrane separating the upstream chamber from the downstream chamber; a dual lumen patient line including a fresh PD fluid lumen in fluid communication with the upstream chamber and a used PD fluid lumen in fluid communication with the downstream chamber; a pressure sensor positioned and arranged to provide a pressure sensor output indicative of a pressure in the downstream chamber of the filter housing; and a control unit configured to perform a pressure integrity test on the hydrophilic filtration membrane by monitoring a pressure sensor output indicative of a negative pressure generated in the downstream chamber by the PD fluid pump over a period of time. A pressure drop test for evaluating a filtration membrane is also disclosed.

Description

Background Art

[0001] The present disclosure relates generally to medical fluid processing, and particularly to dialysis fluid processing requiring fluid heating.

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

[0003] Reduced kidney function, especially kidney failure, is treated with dialysis. Dialysis removes waste products, toxins, and excess water from the body that normally functioning kidneys would remove. Dialysis treatment to replace kidney function is vital for many people because the treatment 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 occurs 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 a replacement fluid, or substitution fluid, to an extracorporeal circuit during treatment. The replacement fluid and the patient's accumulated fluid between treatments are ultrafiltered during HF treatment, providing a convective transport mechanism that is particularly beneficial in removing medium and large molecules.

[0006] Hemodiafiltration ("HDF") is a treatment modality that combines convective and diffusive clearance. HDF uses 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 in centers. Today there is a trend toward home hemodialysis ("HHD"), in part because HHD can be performed every day, which provides therapeutic benefits compared to hemodialysis treatments that are usually performed twice or three times a week in centers. Studies have shown that more frequent treatments remove more toxins and wastes and result in less interdialytic fluid overload than patients who receive less frequent but potentially longer treatments. The down cycle (fluctuation of fluids and toxins) experienced by patients who receive more frequent treatments will not be as obvious as that experienced by patients who receive treatment in centers, because patients who receive treatment in centers have accumulated toxins for two or three days before treatment. In some areas, the nearest dialysis center may be many miles from the patient's home, resulting in a large portion of the day being consumed by home treatment time. Treatment in a center close to the patient's home may also consume a large portion of the patient's day. HHD can occur at night or during the day when the patient is resting, working or performing other activities.

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

[0009] There are various types of peritoneal dialysis therapies, including continuous ambulatory peritoneal dialysis ("CAPD"), automated peritoneal dialysis ("APD"), tidal 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 consumed dialysis fluid to drain from the peritoneal compartment. The patient then switches the fluid connection so that the patient's catheter is connected to a bag of fresh dialysis fluid to infuse fresh dialysis fluid into the patient through the catheter. The patient disconnects the catheter from the bag of fresh dialysis fluid and allows the dialysis fluid to reside in the peritoneal compartment, where transfer of waste, toxins, and excess water occurs. After the dwell period, the patient repeats the manual dialysis procedure, for example four times a day. Manual peritoneal dialysis requires a significant amount of time and effort from the patient, leaving ample 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 the cycles automatically while the patient is sleeping. PD machines relieve the patient from having to manually perform treatment cycles and from having to transport 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 chamber. The PD machine also allows the dialysis fluid to dwell within the chamber and allows the transfer of waste, toxins, and excess water to occur. The source may include multiple liters of dialysis fluid, including several bags of solution.

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

[0012] In any of the above modalities, 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 can become significant. In addition, daily disposables require storage space, which can become a hassle for home owners and businesses. In addition, daily disposable replacement requires time and effort by the patient or caregiver at home or in the clinic every day.

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

[0014] Also known from document US2020086028A1 is a peritoneal dialysis ("PD") system comprising a housing, a pneumatic pump chamber operating with a fluid pump chamber of a disposable cassette housed by the housing. The patient line comprises a sterile sterilizing grade filter having a hydrophilic filter membrane and a patient line connecting the filter to the PD pump. Pressure testing of the filter membrane is easily performed before delivery to the patient.

[0015] Document US2021 / 220539A1 discloses a control unit configured to evaluate a hydrophilic filter membrane by analyzing the pressure drop across the hydrophilic filter membrane.

[0016] Documents WO 2010 / 002830 A2, US 5 275 724 A and US 2019 / 262525 A1 disclose other dialysis machines according to the prior art. Summary of the invention

[0017] The present disclosure describes an automated peritoneal dialysis ("PD") system that includes a PD machine or cycler. For example, the PD machine is capable of delivering fresh, heated PD fluid to a patient at a pressure of 14 kPa (2.0 psig) or greater. For example, the PD machine is capable of removing used PD fluid or effluent from a patient at a pressure between -5 kPa (-.73 psig) and -15 kPa (-2.2 psig), such as -9 kPa (-1.3 psig) or greater. Fresh PD fluid can be delivered to the patient via a dual-lumen patient line and first heated to body fluid temperature, e.g., 37°C. The heated PD fluid is then pumped through the fresh PD fluid cavity of the dual-lumen patient line to a disposable filter kit that is connected to the patient's transfer kit, which in turn is connected to an indwelling catheter leading to the patient's peritoneal cavity. The disposable filter kit is in fluid communication with the fresh PD fluid cavity and the used PD fluid cavity of the dual-lumen patient line. In one embodiment, the disposable filter kit is provided as a last chance filter for a PD machine, wherein the PD machine can be heat sterilized between treatments.

[0018] The system may include one or more PD fluid containers or bags that supply fresh PD fluid to a PD machine or cycler. The PD machine or cycler may include internal lines with two-way valves or three-way valves and at least one PD fluid pump for pumping fresh PD fluid from one or more PD fluid containers or bags to a patient and for removing used PD fluid from a 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 internal lines of the PD machine or cycler to the patient. The flexible drain line leads from the internal lines of the PD machine or cycler to a house drain or drain container. In one embodiment, the system sterilizes all internal lines, PD fluid lines, and double-lumen patient lines after treatment for reuse in the next treatment. Sterilization may involve heat sterilization using remaining fresh PD fluid.

[0019] To ensure that the filter kit is operating properly before and during treatment, it is contemplated that at least one of a pressure drop test or a pressure integrity test is performed on the hydrophilic membrane of the filter kit. In one embodiment, a pressure integrity test is performed before treatment, after priming the dual lumen patient line and the filter kit. It is then contemplated that one or more pressure drop tests are performed during treatment (e.g., at the beginning of each patient fill).

[0020] In one embodiment, the filter kit includes a short flexible line extending downstream from a housing of the filter kit, wherein a hydrophilic filter membrane is located within the housing, dividing the housing into an upstream chamber (in fluid communication with the fresh PD fluid lumen of the double lumen patient line) and a downstream chamber (in fluid communication with the spent PD fluid lumen of the double lumen patient line). The upstream chamber is provided with one or more hydrophobic membranes for allowing air to aseptically enter and exit the upstream chamber as needed. In one embodiment, the distal end of the short flexible line includes a connector that is capped during perfusion. In another embodiment, the short flexible line is connected to a transfer kit for the patient during perfusion. In either case, air during perfusion can be trapped in the short flexible tube. Therefore, removing air from a double lumen patient line and a filter kit including a short flexible tube involves multiple steps.

[0021] In a first step, the control unit of the PD system causes the filter set to be primed by causing the PD fluid pump to pump fresh PD fluid through the hydrophilic filter membrane, pushing air (i) out of the upstream chamber through the at least one hydrophobic membrane and (ii) out of the downstream chamber into the short flexible line. In a second priming step, the control unit further causes the PD fluid pump to apply negative pressure to the spent PD fluid chamber, the downstream chamber, and the downstream line, drawing (i) fresh PD fluid through the hydrophilic filter membrane to replace the air removed from the short flexible line, and (ii) air through the at least one hydrophobic membrane into the upstream chamber, causing air to be removed from the short flexible line. In a third priming step, the control unit is further configured to cause the PD fluid pump to pump fresh PD fluid into the upstream chamber, forcing air out of the at least one hydrophobic membrane, causing air to be removed from the upstream chamber. After the third priming step, both chambers of the filter set and the short flexible line are fully primed (possibly containing a small amount of air).

[0022] Once the patient line and the filter kit including the short flexible line are primed, the control unit causes a pressure integrity test to be performed before treatment begins (alternatively, the pressure drop test described herein is performed at the end of prime). In the pressure integrity test, the control unit in one embodiment causes the PD fluid pump to apply negative pressure to the used PD fluid chamber of the dual-lumen patient line and the downstream chamber of the filter housing. The negative pressure draws (i) fresh PD fluid from the upstream chamber through the hydrophilic filter membrane into the downstream chamber, which in turn causes (ii) air to be drawn into the upstream chamber through at least one hydrophobic membrane. Because the hydrophilic filter membrane is wet, air cannot pass through the membrane. Therefore, as negative pressure continues to be applied, air fills the upstream chamber of the filter housing.

[0023] Once the PD fluid is removed from the upstream chamber, so that all or substantially all of the wet hydrophilic filter membrane is exposed to air on its upstream surface, the negative pressure in the downstream chamber is set to the desired integrity test pressure, for example, from -60 kPa (8.7 psig) to -90 kPa (13.1 psig), such as -75 kPa (10.9 psig). At this point, the control unit closes the valve required to lock the negative pressure at the downstream chamber and begins incrementing the timer while monitoring the output of one or more pressure sensors positioned and arranged to sense the set negative pressure. The pressure monitoring and timer incrementing continue for a desired duration sufficient to detect any leak in the hydrophilic filter membrane, for example, at least one minute, such as 90 seconds.

[0024] During the monitoring period, if the measured -75 kPa (10.9 psig) does not "drop" (become less negative) by an amount equal to or greater than an allowed amount, e.g., 2.5 kPa (0.36 psig), the control unit determines that the hydrophilic filter membrane is intact and allows treatment to proceed, e.g., an initial patient drain or patient fill. However, if during this time period, the measured -75 kPa (10.9 psig) does "drop" (become less negative) by an amount equal to or greater than an allowed amount, e.g., 2.5 kPa (0.36 psig), the control unit determines that the hydrophilic filter membrane is damaged and causes the user interface to provide an audio, visual, or audiovisual alarm or alert, notifying the patient that the filter kit is faulty and needs to be replaced.

[0025] Although one or more additional pressure integrity tests may be performed during treatment, the system of the present disclosure may alternatively perform one or more pressure drop tests on the hydrophilic filter membrane during treatment (e.g., at the beginning of each patient fill). The pressure drop test is easier to perform and involves monitoring multiple pressure sensors, at least one pressure sensor measuring the pressure upstream of the hydrophilic filter membrane and at least one pressure sensor measuring the pressure downstream of the hydrophilic filter membrane. An intact hydrophilic filter membrane is expected to cause a certain pressure drop, which may increase over time due to the type of PD fluid being pumped, for example, the pressure drop is higher for the last filled PD fluid (e.g., icodextrin or higher glucose PD fluid). The pressure drop will also increase as the filter membrane accumulates fibrin, protein, and other materials on its downstream side from the patient's effluent and bacteria on its upstream side from the filtration. Therefore, it is expected that the control unit causes the PD fluid pump to flush at least the downstream surface of the filter membrane with fresh PD fluid after each discharge to remove solid effluent to discharge before starting the next patient fill.

[0026] For the pressure drop test, multiple upstream and downstream pressure drop readings may be taken, and multiple pressure drops may be calculated, for example, over a period of several seconds, to obtain an average or mean pressure drop that is compared to an acceptable pressure drop range or a minimum expected pressure drop. In an embodiment, if the average or mean pressure drop is outside the acceptable pressure drop range or is below the minimum acceptable value, the control unit stops treatment and causes the user interface to provide an audio, visual, or audio-visual alarm or alert notifying the patient that the filter kit is faulty and needs to be replaced. If the average or mean pressure drop is within the acceptable pressure drop range, or is equal to or above the minimum acceptable pressure drop, the control unit allows treatment to proceed.

[0027] In view of the disclosure set forth herein, and without limiting the present disclosure in any way, in the first aspect of the present disclosure, any or all of the structure and / or function of any one of claims 1 to 21 may be combined with any or all of the structure and / or function of any other claim in claims 1 to 21. In the second aspect of the present disclosure, which may be combined with any part or all of the first aspect, the structure and / or function of any one of claims 1 to 21 may be combined with any or all of the structure and / or function of any other claim in claims 1 to 21. Figures 1 to 15 Any one or more of the features, functions and alternatives described in any one or more of the above may be combined with Figures 1 to 15 any combination of features, functions and alternatives described in any other description.

[0028] In view of the above aspects and the present disclosure set forth herein, an advantage of the present disclosure is to provide structure and functionality that ensures that the hydrophilic filter is intact and ready for use.

[0029] Another advantage of the present disclosure is to provide structures and functions that enable testing of hydrophilic filters prior to and / or during use.

[0030] Another advantage of the present disclosure is to provide a method that can be used to test the structure and function of a hydrophilic filter using different tests.

[0031] Yet another advantage of the present disclosure is to provide a structure and function that enables testing of hydrophilic filters using existing equipment.

[0032] Additional features and advantages are described in the following detailed description and accompanying drawings, and will be apparent therefrom. The features and advantages described herein are not all-inclusive, and in particular, many additional features and advantages will be apparent to those of ordinary skill in the art in view of 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 each advantageous embodiment be claimed separately. In particular, the system disclosed herein may have any one or more or all of the filter pressure drop test structure and method described herein, the patient line including the filter kit perfusion structure and method, and the filter pressure integrity test structure and method. In addition, it should be noted that the language used in the specification is selected primarily for readability and guidance purposes, and not to limit the scope of the subject matter of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a fluid flow schematic of one embodiment of a medical fluid (eg, PD fluid) system having a filter kit test of the present disclosure, wherein the system is in a treatment state.

[0034] Figure 2 is a fluid flow diagram of one embodiment of a medical fluid (eg, PD fluid) system having a filter kit test of the present disclosure, wherein the system is in a sterile state.

[0035] Figures 3 to 10 One embodiment is shown for priming a medical fluid (eg, PD fluid) system for performing or preparing to perform one or both of the pressure drop test or the pressure integrity test of the present disclosure.

[0036] Figures 11 to 15 One embodiment of a pressure integrity test for use with the present disclosure is shown. DETAILED DESCRIPTION System Overview

[0037] Referring now to the drawings and in particular Figure 1, a medical system having enhanced features 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. The user interface 108 may alternatively or additionally be a remote user interface, for example, via a tablet or smart phone. The control unit 100 may also include a transceiver and a wired or wireless connection to a network (not shown) (e.g., the Internet) for sending treatment data to and receiving prescription instructions / changes from a doctor's or clinician's server that interacts with the doctor's or clinician's computer. The control unit 100 in the embodiment 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 requires the PD machine or cycler 20 to be sterilized, for example, via thermal sterilization, between treatments.

[0038] Figure 1 The system 10 includes an inline resistive heater 56, reusable supply lines or tubes 52a1 to 52a4 and 52b, an air trap 60 operating in conjunction 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, pressure sensors 78a, 78b1, 78b2 and 78c, reusable patient tubes or lines 52f and 52g with corresponding valves 54f and 54g, a dual lumen patient line 28, a hose reel 80 for retrieving the patient line 28, a reusable drain tube or line 52i extending to a drain line connector 34 and having a drain line valve 54i, and reusable recirculating sterilization tubes or lines 52r1 and 52r2 operating in conjunction with corresponding sterilization valves 54r1 and 54r2. A third recirculation or sterilization tube or line 52r3 extends between sterilization or PD fluid line connectors 30a and 30b for use during sterilization. A fourth recirculation or sterilization tube or line 52r4 extends between sterilization connectors 30c and 30d for use during sterilization.

[0039] The system 10 also includes PD fluid containers or bags 38a-38c (e.g., containing the same or different formulations of PD fluid) 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 contain a PD fluid of the same or a different type (e.g., icodextrin) than the PD fluid 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.

[0040] 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, which includes an inner cavity, for example, a U-shaped cavity, which guides fresh or used dialysis fluid from one PD fluid cavity of the connection distal end 28e of the dual-lumen patient line 28 to the other PD fluid cavity for sterilization. Reusable supply tubes or lines 52a1 to 52a4 are in communication with the reusable supply lines 24a to 24d, respectively. The reusable supply tubes 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. The three-way valve 94a in the example shown allows the control unit 100 to select between (i) 2.27% (or other) glucose dialysis fluid from the container or bag 38b or 38c and (ii) icodextrin from the container or bag 38d. In the embodiment shown, the icodextrin from the container or bag 38d is connected to the normally closed port of the three-way valve 94a.

[0041] 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 potentially drawing spent PD fluid into pump 70. Disposable drain line 36 is removed for sterilization in one embodiment, with drain line connector 34 capped via cap 34c to form a closed sterilization circuit. PD fluid pump 70 can 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 fresh and spent PD fluid flow rates and volumes.

[0042] 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 that allows the aspiration pressure of the pump 70 to be measured to help the control unit 100 more accurately determine the pump volume. In the embodiment shown, the additional pressure sensor 78c is located along the exhaust line 52e, which may be filled with air or a mixture of air and PD fluid, but should be at the same negative pressure as the PD fluid located in the PD fluid line 52c.

[0043] Figure 1 The system 10 in the example includes redundant pressure sensors 78b1 and 78b2, where the output of one pressure sensor is used for pump control, as discussed herein, and the output of the other pressure sensor is a safety or watchdog output to ensure that the control pressure sensor is reading accurately. The pressure sensors 78b1 and 78b2 are located along the line including the third recirculation valve 54r3. The system 10 may also employ one or more crossover points, where Figure 1 Those marked by an X in the figure may (i) reduce the total amount and volume of internal reusable tubing, (ii) reduce the number of valves required, and (iii) allow minimization of the portion of the fluid circuit shared by fresh and used PD fluid.

[0044] Figure 1 The 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 acid) reaches the treatment fluid line during treatment. Citric acid (or other acid) is used instead during disinfection.

[0045] In an embodiment, the control unit 100 uses feedback from any one or more of the pressure sensors 78a to 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, 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.

[0046] Under control of the control unit 100, the inline resistive heater 56 is capable of heating fresh PD fluid to body temperature, e.g., 37°C, for delivery at a desired flow rate to the patient P. In an embodiment, the control unit 100 uses feedback from the temperature sensor 58a in a PID temperature routine to pump fresh PD fluid to the patient P at a desired temperature.

[0047] Figure 1 The system 10 is also shown to include and use a disposable filter kit 40 that is in fluid communication with the fresh and used PD fluid chambers of the dual-lumen patient line 28. The disposable filter kit 40 includes a disposable connector 42 that is 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 hydrophilic filter membrane 46, which can be sterilizing grade and further filters the fresh PD fluid. The disposable filter kit 40 is provided in one embodiment as a last chance filter for a PD machine 20 that has been heat sterilized between treatments. Any pathogens that remain after sterilization (although unlikely) will be filtered out of the PD fluid through the hydrophilic filter membrane 46 of the disposable filter kit 40.

[0048] Figure 1 The system 10 is shown arranged for treatment with PD fluid containers or bags 38a to 38d 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 a treatment.

[0049] Figure 2 The system 10 is shown in a sterilization mode. The PD fluid containers or bags 38a to 38d are removed and instead the flexible PD fluid lines 24a to 24d are inserted in a sealing manner into the sterilization or PD fluid line connectors 30a to 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 2The PD machine or cycler 20 of the system 10 in is configured to perform a sterilization sequence, for example, a heated sterilization sequence, in which fresh PD fluid is heated to a sterilization temperature, for example, 70° C. to 90° C., via an inline heater 56. The PD fluid pump 70 circulates the heated PD fluid closed sterilization circuit 90 for the amount of time required to properly sterilize the fluid components and lines of the sterilization circuit. Voltage drop test

[0050] Reference again Figure 1 It is contemplated that the control unit 100 performs a pressure drop test at a desired time or times before and / or during treatment to ensure that the hydrophilic filter membrane 46 of the disposable filter kit 40 is functioning properly. The pressure drop test requires fluid to flow through the filter membrane 46. When the fluid (e.g., PD fluid) flows through the filter membrane 46, pressure measurements are taken upstream and downstream of the filter membrane 46. Figure 1 In this embodiment, the output from pressure sensor 78a can be used as the upstream pressure measurement, while the output from any one or more of pressure sensors 78b1, 78b2 can be used as the downstream pressure measurement.

[0051] It is contemplated that a pressure drop test is performed at least during priming of the internal lines of the PD machine or cycler 20, the reusable PD fluid lines 24a to 24d, and the reusable patient line 28. During priming, the patient line 28 is connected to the patient P in one embodiment via connection to the disposable filter kit 40 and the patient's transfer kit, which may be open or closed. Primer may alternatively be performed over the flexible tubing or tube 50 (see Figures 3 to 7 ) is capped, such that disposable filter kit 40 is not yet connected to patient P. In any event, control unit 100 causes fresh PD fluid to be pumped from PD fluid container or bag 38a-38d via PD fluid pump 70 through fresh patient tube or line 52f, through the fresh PD fluid lumen of dual lumen patient line 28, and through filter kit 40 including filter membrane 46. Control unit 100 hereby causes one of PD fluid valves 54a-54c or 94a to be opened or switched, such that valves 54d and 54f are opened, and valve 54g is closed. In one embodiment, air is pushed out of hydrophobic vent 48 (see FIG. 4 ) disposed in filter kit 40. Figures 3 to 7 ). During the pressure drop test, fresh PD fluid is heated to patient temperature, eg, 37°C, so that the pressure drop is recorded under therapeutic conditions.

[0052] It should be understood that, prior to initial discharge, the spent PD fluid lumen of dual lumen patient line 28 may be filled primarily with air. However, as the PD fluid is pushed through the filter membrane, the air will be compressed to the PD fluid pressure downstream of filter membrane 46 of filter assembly 40. Thus, even when downstream pressure sensors 78b1, 78b2 are partially or completely exposed to air, the pressure downstream of filter membrane 46 can be accurately read.

[0053] The pressure used for the pressure drop determination, and the determination itself, is performed over a period of time sufficient to ensure that the determined pressure drop is stable and accurate (e.g., one to five seconds). During this period, multiple sets of upstream and downstream pressure drop readings may be taken, and multiple pressure drop calculations may be performed. Multiple pressure drop calculations may be averaged, or the average pressure drop in the calculation may be used as the pressure drop for comparison with an acceptable pressure drop range.

[0054] In an embodiment, if the average or mean pressure drop is outside the acceptable pressure drop range or is below the minimum acceptable value, the control unit 100 stops the treatment and causes the user interface 108 to provide an audio, visual or audio-visual alarm or alert, notifying the patient that the filter kit 40 is faulty and needs to be replaced. If the average or mean pressure drop is within the acceptable pressure drop range, or is equal to or higher than the minimum acceptable pressure drop, the control unit 100 allows the treatment to proceed. In an embodiment, it is assumed that the minimum acceptable pressure drop or pressure drop range at the start of treatment is the pressure drop or pressure drop range at which the hydrophilic filter membrane 46 is in its original state.

[0055] As described above, the valve at the patient's transfer kit can be opened or closed during the pressure drop test performed during priming. Alternatively, the filter kit 30 can be disconnected from the patient's transfer kit during priming. Performing a pressure drop test with the transfer kit valve open during priming relieves the patient from having to remember to open the valve during treatment. However, performing a pressure drop test with the transfer kit connected and the transfer kit valve open during priming means that the PD fluid flow will be diverted, with some of the flow returning to the PD machine or cycler 20 via the spent PD fluid lumen of the dual lumen patient line, and some of the PD fluid flow flowing to the patient.

[0056] In addition to priming, it is contemplated that subsequent pressure drop tests may be performed one or more times during treatment, for example, at the beginning of each patient fill using the PD machine or cycler 20. Here again, pressure measurements are taken upstream and downstream of the filter membrane 46 while the PD fluid is flowing through the filter membrane 46. Figure 1 In this embodiment, the output from pressure sensor 78a can be used as the upstream pressure measurement, while the output from one or more pressure sensors 78b1, 78b2 can be used as the downstream pressure measurement.

[0057] During each patient fill, patient line 28 is connected to patient P via connections to disposable filter kit 40 and a patient transfer kit, which may be open or closed. Control unit 100 causes fresh PD fluid to be pumped from one of PD fluid containers or bags 38a-38d via PD fluid pump 70 through fresh patient tube or line 52f, through the fresh PD fluid lumen of dual lumen patient line 28, through filter kit 40 including filter membrane 46, and through the patient transfer kit into the peritoneal cavity of patient P. Control unit 100 hereby causes one of PD fluid valves 54a-54c or 94a to open or switch, and causes valves 54d and 54f to open. Used PD fluid valve 54g is closed. During a patient fill, fresh PD fluid is heated to patient temperature, e.g., 37°C.

[0058] In many cases, after priming, the first treatment operation is to remove the last fill of spent PD fluid from the patient P. In this case, the spent PD fluid lumen of the dual lumen patient line 28 is filled with spent PD fluid for each patient fill and each pressure drop test during treatment. If there was no last fill removed from the patient, such that the first treatment operation is the first patient fill, the spent PD fluid lumen of the dual lumen patient line 28 may be filled primarily with air. However, again, as the PD fluid is pushed through the filter membrane 46 of the filter assembly 40, the air will be compressed to the PD fluid pressure downstream of the filter membrane. Thus, even when the downstream pressure sensors 78b1, 78b2 are partially or completely exposed to air during the first patient fill, the pressure downstream of the filter membrane 46 will be accurately read.

[0059] The pressure used for the pressure drop determination during treatment, as well as the determination itself, can be performed over a period of time sufficient to ensure that the determined pressure drop is stable and accurate (e.g., one to five seconds). During this period, multiple sets of upstream and downstream pressure drop readings can be obtained by monitoring the pressure sensors 78a, 78b1, 78b2 by the control unit 100, and multiple pressure drop calculations can be performed. The multiple pressure drop calculations can be averaged, or the average pressure drop in the calculation can be used as the pressure drop for comparison with the acceptable pressure drop range.

[0060] For example, prior to priming, if the average or mean pressure drop during treatment is outside of an acceptable pressure drop range or is below a minimum acceptable value, the control unit 100 stops treatment and causes the user interface 108 to provide an audio, visual, or audio-visual alarm or alert, notifying the patient that the filter kit 40 is faulty and needs to be replaced. If the average or mean pressure drop is within an acceptable pressure drop range, or is equal to or above the minimum acceptable pressure drop, the control unit 100 allows the current patient fill to proceed.

[0061] It is expected that during treatment, the pressure drop across the hydrophilic filter membrane 46 will increase. The pressure drop may increase due to the type of PD fluid being pumped, for example, the pressure drop is higher for the last fill of PD fluid (e.g., icodextrin or higher dextrose PD fluid). The pressure drop will increase as the filter membrane 46 accumulates fibrin, protein, and other materials on its downstream side from the patient's effluent and accumulates bacteria on its upstream side from filtration. It is expected that the control unit 100 causes the PD fluid pump 70 to flush at least the downstream surface of the filter membrane 46 with fresh PD fluid after each discharge to remove solid effluent for discharge before starting the next patient fill. In one embodiment, flushing includes pushing a small amount of fresh PD fluid (e.g., 5-50 ml) through the filter membrane 46 to remove solid effluent material from its downstream surface, and then removing a small amount of PD fluid (including the removed effluent material) for discharge. However, even with flushing after discharge, it is expected that the control unit 100 may have to increase the minimum acceptable pressure drop or pressure drop range during treatment for comparison with the measured pressure drop. Filling / Pressure Integrity Testing

[0062] Reference now Figures 3 to 15 Just after priming, in addition to or in lieu of a pressure drop test, the control unit 100 may cause an integrity test of the hydrophilic (eg, sterilizing grade) filter membrane 46 to be performed. Figures 3 to 10 One suitable priming sequence for dual lumen patient line 28 and filter set 40 is shown. Figures 3 to 10 The filter kit 40 is shown to include a filter housing 40h that holds a hydrophilic filter membrane 46 in a sealed manner so as to form an upstream chamber 40u and a downstream chamber 40d located upstream and downstream of the filter membrane 46, respectively. The filter housing 40h includes: a connector 42 that connects to the distal end 28e of the reusable patient line 28; and a connector 44 that connects to the patient's transfer kit, or in one embodiment, to a short flexible line or tube 50 that extends to a connector 64c ( Figure 8 ).

[0063] Figures 3 to 10 The filter housing 40h is also shown to include one or more hydrophobic membranes or vents 48 along the upstream chamber 40u to allow air to be forced out or poured out of the filter housing. In one embodiment, the (e.g., sterilizing grade) filter membrane 46 is made of a hydrophilic material that may have a pore size of about 0.2 microns through which fresh PD fluid flows for further filtration. For example, the filter membrane 46 may be made of polysulfone or polyethersulfone blended with polyvinylpyrrolidone. The one or more hydrophobic membranes 48 may be made, for example, of polytetrafluoroethylene ("PTFE").

[0064] Figure 3 A first priming step is shown in which the control unit 100 causes the appropriate valves to open and the PD fluid pump 70 pumps fresh PD fluid from the PD fluid containers or bags 38a-38d, through the fresh PD fluid lumen of the dual lumen patient line 28 and into the upstream chamber 40u of the filter housing 40h so as to contact the upstream side of the filter membrane 46. Air in the upstream chamber 40u is forced out of the filter housing via the one or more hydrophobic membranes or vents 48. Air may also travel through the hydrophilic filter membrane 46 as long as the hydrophilic filter membrane 46 is dry. However, Figure 4 The filter membrane 46 is shown to wet quickly, forcing the air to exit only through the one or more hydrophobic membranes 48 .

[0065] Figures 5 to 7 It is shown that once the upstream chamber 40u of the filter housing 40h becomes completely full of fresh PD fluid, the fresh PD fluid is forced (filtered) through the filter membrane 46 into the downstream chamber 40d of the filter housing 40h. Figure 7 The upstream and downstream chambers are shown both completely filled with fresh PD fluid.

[0066] Figure 8 The air from the downstream chamber 40d is shown to be forced into a short flexible line or tube 50 extending to the patient transfer kit 64. In order to remove the air pushed into the short flexible line or tube 50, Fig. 9 4. The control unit 100 in FIG. 4 causes the fresh PD fluid valve 54f to close, and causes the spent PD fluid valve 54g and the drain valve 54i to open. The control unit 100 causes the PD fluid pump 70 to apply negative pressure to the spent PD fluid chamber 28u of the dual lumen patient line 28. The negative pressure (i) draws air in the short flexible line or tube 50 into the spent PD fluid chamber 28u, and (ii) draws air from the environment through the one or more hydrophobic membranes 48 into the upstream chamber 40u of the filter housing 40h. The air entering the upstream chamber 40u in turn pushes fresh PD fluid through the hydrophilic filter membrane 46 into the short flexible line or tube 50, thereby replacing the exiting air. Therefore, in one embodiment, it is contemplated that the filter housing 40h and the short flexible line or tube 50 are configured so that the volume of the upstream chamber 40u is equal to or greater than the internal volume of the short flexible line or tube 50, so that there is sufficient fresh PD fluid to fill the flexible tube.

[0067] Fig.10The next step is shown to be that control unit 100 causes used PD fluid valve 54g and drain valve 54i to close, and causes fresh PD fluid valve 54f and the appropriate PD fluid valve to open. Control unit 100 then causes PD fluid pump 70 to refill upstream chamber 40u with fresh PD fluid, exhausting air to atmosphere via one or more hydrophobic membranes or vents 48. Fig.10 At the end of the procedure in , the filter housing 40h and the short flexible line or tube 50 are completely filled with fresh PD fluid (there may be a small amount of residual air, eg, less than 1 cubic centimeter).

[0068] For ease of explanation, Figures 8 to 10 The spent PD fluid chamber 28u of the dual lumen patient line 28 is shown extending from a short flexible line or tube 50. However, it should be understood that the spent PD fluid chamber 28u may alternatively be placed in direct fluid communication with the downstream chamber 40d of the filter housing 40h. Figure 1 As shown, both the used PD fluid chamber 28u and the fresh PD fluid chamber 28f can be connected to a disposable connector 42, wherein the connector 42 includes an internal port extending into the downstream chamber 40d, which allows the used PD fluid chamber 28u to communicate with the downstream chamber 40d.

[0069] Figures 11 to 15 One embodiment of an integrity or pressure retention test of the system 10 of the present disclosure is shown, which may occur directly after priming and replace the pressure drop test discussed above, but a pressure drop test is still performed during treatment (e.g., at the beginning of each patient fill). Figures 11 to 15 In the pressure integrity test of filter housing 40h, the wet membrane becomes a complete wall of air when filter housing 40h is filled with PD fluid on both sides of hydrophilic filter membrane 46. For the integrity test, control unit 100 causes fresh PD fluid valve 54f to be closed, so that fresh PD fluid chamber 28f of dual-lumen patient line 28 is closed. Control unit 100 also causes used PD fluid valve 54g and drain valve 54i to be opened, and causes PD fluid pump 70 to apply negative pressure on downstream chamber 40d via used PD fluid chamber 28u, used PD fluid line 52g, line 52c, and drain line 52i.

[0070] In an embodiment, the integrity or pressure hold test pressure is -60 kPa (8.7 psig) to -90 kPa (13.1 psig), such as -75 kPa (10.9 psig). Figures 11 to 13 It is shown that the control unit 100 may initially operate the PD fluid pump 70 at a higher rate to more quickly increase the negative pressure within the downstream chamber 40d. Fig.11 An initial application of negative pressure is shown. Fig.12 and Fig.13Negative pressure is shown drawing PD fluid from upstream chamber 40u, through hydrophilic filter membrane 46 and into downstream chamber 40d. In one embodiment, control unit 100 uses output from at least one pressure sensor 78b1, 78b2 as feedback to know the negative pressure within downstream chamber 40d.

[0071] exist Fig.14 In an embodiment, when the measured negative pressure approaches the target integrity test pressure, the control unit 100 causes the PD fluid pump 70 to slow down significantly until the negative pressure within the downstream chamber 40d reaches the target pressure, eg, -75 kPa (10.9 psig). Fig.14 It is also shown that substantially all of the PD fluid has been expelled from the upstream chamber 40u, through the hydrophilic filter membrane 46, and into the downstream chamber 40d.

[0072] exist Fig.15 Once the target pressure is reached, control unit 100 stops PD fluid pump 70 and performs an integrity or pressure hold test (with spent PD fluid valve 54g and drain valve 54i opened or closed). Fig.15 As shown, the upstream chamber 40u is at zero kPA (zero psig) due to entry into the atmosphere via one or more hydrophobic membranes or vents 48, while the downstream chamber 40d is maintained at a target pressure, e.g., -60 kPa (8.7 psig) to -90 kPa (13.1 psig), such as -75 kPa (10.9 psig). Therefore, there is a relatively large pressure differential across the filter membrane 46, which is relied upon to detect any leaks in the membrane. In the integrity or pressure retention test of the present disclosure, the control unit 100 monitors the output from at least one pressure sensor 78b1, 78b2 for a specified time period (e.g., at least one minute or 90 seconds). If the measured -75 kPa (10.9 psig) does not "drop" (become less negative) by an amount equal to or greater than an allowed amount, e.g., 2.5 kPa (0.36 psig), during this time period, the control unit 100 determines that the hydrophilic filter membrane 46 is intact and allows treatment to continue, e.g., to an initial patient discharge or patient fill. However, if during this time period, the measured -75 kPa (10.9 psig) does "drop" (become less negative) by an amount equal to or greater than an allowed amount, e.g., 2.5 kPa (0.36 psig), the control unit 100 determines that the hydrophilic filter membrane 46 is damaged and causes the user interface 108 to provide an audio, visual, or audio-visual alarm or alert, notifying the patient that the filter kit 40 is faulty and requires replacement.

[0073] It is contemplated that the integrity or pressure retention test of the system 10 of the present disclosure is capable of detecting holes or ruptures with a nominal diameter of 10 to 20 μm. If no such holes or ruptures are found and it is determined that the hydrophilic filter membrane 46 is intact, the control unit 100 repeats the Fig.10 , wherein the PD fluid pump 70 is caused to refill the upstream chamber 40u with fresh PD fluid, exhausting the air to the atmosphere via the one or more hydrophobic membranes or vents 48. The filter housing 40h and short flexible line or tube 50 are both filled with fresh PD fluid, and the hydrophilic filter membrane 46 is ready for treatment.

[0074] 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. Therefore, such changes and modifications are intended to be covered by the appended claims. For example, the system 10 for any of the improved treatment features discussed herein need not use redundant or durable components, and may instead employ a disposable kit having a disposable pumping portion in contact with the corresponding medical fluid. For example, although the disposable filter kit 40 need not be a last chance filter for a system without thermal disinfection, if fresh PD fluid is manufactured online at the time of use, the disposable filter kit 40 may still be provided as a last chance filter for online PD fluid. PD fluid pumping with a disposable kit may alternatively be performed via pneumatic pump actuation of a sheet of a disposable box of a disposable kit, via an electromechanical pump actuation of a sheet of a disposable box of a disposable kit, or via a peristaltic pump actuation of a pumping tubing segment provided with a disposable kit.

Claims

1. A peritoneal dialysis (PD) system (10), comprising: Housing (22); A PD fluid pump (70) housed by the housing (22); A filter kit (40) comprising a hydrophilic filter membrane (46); a dual lumen patient line (28) in fluid communication with the PD fluid pump (70), the dual lumen patient line (28) comprising a fresh PD fluid lumen (28f) in fluid communication with the upstream side of the hydrophilic filter membrane (46) and a spent PD fluid lumen (28u) in fluid communication with the downstream side of the hydrophilic filter membrane (46); a first pressure sensor (78a) positioned and arranged to provide a first pressure sensor output indicative of PD fluid pressure in the fresh PD fluid chamber (28f); a second pressure sensor (78b1, 78b2) positioned and arranged to provide a second pressure sensor output indicative of PD fluid pressure in the spent PD fluid chamber (28u); as well as A control unit (100) is configured to evaluate the hydrophilic filter membrane (46) by analyzing a pressure drop across the hydrophilic filter membrane (46), wherein the pressure drop comprises a difference between the second pressure sensor output and the first pressure sensor output.

2. The PD system (10) according to claim 1, wherein: The control unit (100) is configured to assess the hydrophilic filtration membrane (46) as intact if the pressure drop is equal to or higher than a minimum pressure drop or within an acceptable pressure drop range.

3. The PD system (10) according to claim 2, wherein: The minimum pressure drop or the acceptable pressure drop range increases during treatment.

4. The PD system (10) according to any one of the preceding claims, wherein: The control unit (100) is configured to evaluate the hydrophilic filter membrane (46) as faulty if the pressure drop is below a minimum pressure drop or outside an acceptable pressure drop range.

5. The PD system (10) according to any one of the preceding claims, wherein: The pressure drop includes an average of a plurality of differences between a plurality of the second pressure sensor outputs and a plurality of the first pressure sensor outputs.

6. The PD system (10) according to any one of the preceding claims, wherein: The pressure drop includes a mean pressure drop derived from a plurality of differences between a plurality of the second pressure sensor outputs and a plurality of the first pressure sensor outputs.

7. The PD system (10) according to any one of the preceding claims, wherein: The control unit (100) is configured to evaluate the hydrophilic filter membrane (46) by analyzing the pressure drop across the hydrophilic filter membrane (46) during at least one patient fill of PD therapy.

8. The PD system (10) according to any one of the preceding claims, wherein: The control unit (100) is configured to cause the PD fluid pump (70) to flush PD fluid through the hydrophilic filter membrane (46) to a discharge port prior to the at least one patient fill and after at least one patient discharge.

9. The PD system (10) according to any one of the preceding claims, wherein: The control unit (100) is configured to evaluate the hydrophilic filter membrane (46) by performing a pressure integrity test on the hydrophilic filter membrane (46) prior to PD treatment.

10. The PD system (10) according to any one of the preceding claims, wherein: The pressure integrity test includes the control unit (100) being configured to: (i) cause the PD fluid pump (70) to generate a pressure difference across the hydrophilic filter membrane (46), and (ii) monitor at least one of the first pressure sensor output or the second pressure sensor output to detect a change in the pressure difference.

11. The PD system (10) according to any one of the preceding claims, wherein: The filter kit (40) includes at least one hydrophobic membrane (48), and wherein the control unit (100) is configured to perform the pressure integrity test after priming the filter kit (40), wherein priming the filter kit (40) includes exhausting air through the at least one hydrophobic membrane (48).

12. A peritoneal dialysis (PD) system (10), comprising: Housing (22); A PD fluid pump (70) housed by the housing (22); A filter kit (40) comprising a filter housing (22) and a hydrophilic filter membrane (46), wherein the hydrophilic filter membrane separates an upstream chamber (40u) from a downstream chamber (40d) in the filter housing (22); a dual lumen patient line (28) in fluid communication with the PD fluid pump (70), the dual lumen patient line (28) comprising a fresh PD fluid lumen (28f) in fluid communication with the upstream chamber (40u) and a spent PD fluid lumen (28u) in fluid communication with the downstream chamber (40d); a pressure sensor (78b1, 78b2) positioned and arranged to provide a pressure sensor output indicative of the pressure in the downstream chamber (40d) of the filter housing (22); as well as A control unit (100) is configured to perform a pressure integrity test on the hydrophilic filter membrane (46) by monitoring the pressure sensor output over a period of time, the pressure sensor output being indicative of the negative pressure generated by the PD fluid pump (70) in the downstream chamber (40d).

13. The PD system (10) according to claim 12, wherein: The negative pressure generated in the downstream chamber (40d) is a negative PD fluid pressure.

14. The PD system (10) according to claim 12 or 13, wherein: The negative pressure is -60 kPa (8.7 psig) to -90 kPa (13.1 psig), such as -75 kPa (10.9 psig), and the time period is at least one minute.

15. The PD system (10) according to any one of claims 12 to 14, wherein: The upstream chamber (40u) is maintained at atmospheric pressure during the pressure integrity test.

16. The PD system (10) according to claim 15, wherein: The filter housing (22) comprises at least one hydrophobic membrane (48) forming a part of the upstream chamber (40u), and wherein the atmospheric pressure is achieved by the hydrophobic membrane (48).

17. The PD system (10) according to claim 16, wherein: The control unit (100) is configured to generate negative pressure in the downstream chamber (40d) by causing the PD fluid pump (70) to apply negative pressure to the used PD fluid chamber (28u) and the downstream chamber (40d), so that PD fluid is sucked from the upstream chamber (40u) into the downstream chamber (40d) through the hydrophilic filter membrane (46), and wherein the PD fluid sucked out from the upstream chamber (40u) is backfilled with air through the hydrophobic membrane (48).

18. The PD system (10) according to any one of claims 15 to 17, wherein: The control unit (100) is configured to prime the filter kit (40) including a pipeline (50) extending downstream from the filter kit (40) before performing the pressure integrity test.

19. The PD system (10) according to claim 18, wherein: The control unit (100) is configured to prime the filter assembly (40) by causing the PD fluid pump (70) to pump fresh PD fluid through the hydrophilic filter membrane (46), pushing air (i) out of the upstream chamber (40u) through the at least one hydrophobic membrane (48) and (ii) out of the downstream chamber (40d) into the downstream line (50).

20. The PD system (10) according to claim 19, wherein: The control unit (100) is also configured to apply negative pressure to the used PD fluid chamber (28u), the downstream chamber and the downstream pipeline (50) by causing the PD fluid pump (70) to draw fresh PD fluid through the hydrophilic filter membrane (46) to replace the air removed from the downstream pipeline (50), and to draw air through the at least one hydrophobic membrane (48) into the upstream chamber (40u) to remove air from the downstream pipeline (50).

21. The PD system (10) according to claim 20, wherein: The control unit (100) is also configured to remove air from the upstream chamber (40u) by causing the PD fluid pump (70) to pump fresh PD fluid into the upstream chamber (40u) to evacuate air from the at least one hydrophobic membrane (48).

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