Peritoneal dialysis system and peritoneal dialysis method for minimizing patient drain pain

Abstract

A peritoneal dialysis ("PD") system includes a PD fluid pump, a patient line for receiving spent PD fluid pumped by the PD fluid pump during patient drain, a pressure sensor positioned and arranged to sense a negative pressure associated with the PD fluid pumped during patient drain, and a control unit configured to: (i) determine or know a flow rate of PD fluid pumped during patient drain, (ii) determine an applied negative pressure at which the PD fluid pump will pump PD fluid during patient drain, the applied pressure being based on a pressure drop corresponding to the determined or known flow rate, and (iii) use the sensed negative pressure from the pressure sensor to cause the PD fluid pump to pump PD fluid at the applied negative pressure during patient drain.

Description

[Technical field]

[0001] Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 323,617, entitled "PERITONEAL DIALYSIS SYSTEM AND METHOD FOR MINIMIZING PATIENT DRAIN PAIN," filed March 25, 2022, the entire contents of which are incorporated by reference herein.

[0002] background FIELD OF THE DISCLOSURE The present disclosure relates generally to medical fluid treatment, and more particularly to dialysate treatment. [Background technology]

[0003] A variety of causes can cause a person's renal system to fail. Renal failure results in 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., can accumulate in the patient's blood and tissues.

[0004] Reduced kidney function, particularly kidney failure, is treated by dialysis, which removes waste products, toxins and excess water from the body that normally functioning kidneys would remove. Dialysis procedures to replace kidney function are vital for many people, as the treatment is life-threatening.

[0005] One type of renal failure therapy is hemodialysis ("HD"), which generally uses diffusion to remove waste products from a patient's blood. Diffusion occurs because of a diffusion gradient across a semi-permeable dialyzer between the blood and an electrolyte solution called the dialysate or dialysate.

[0006] 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 the procedure. The replacement fluid, and fluid accumulated by the patient during the procedure, is ultrafiltered during the HF procedure, providing a convective transport mechanism that is particularly useful for removing middle and large molecules.

[0007] Hemodiafiltration ("HDF") is a treatment modality that combines convective and diffusive clearance. HDF uses dialysate flowing through a dialyzer, similar to standard hemodialysis, to provide diffusive clearance. In addition, replacement solution is delivered directly to the extracorporeal circuit to provide convective clearance.

[0008] Most HD, HF, and HDF procedures 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 procedures, which are typically performed twice or three times a week. Studies have shown that more frequent procedures remove more toxins and waste products and experience less fluid overload between dialysis than patients undergoing less frequent but perhaps longer procedures. Patients undergoing more frequent procedures do not experience as many down cycles (fluid and toxin fluctuations) as in-center patients who build up two or three days' worth of toxins before a procedure. In certain areas, the nearest dialysis facility may be many miles away from the patient's home, resulting in door-to-door procedure times consuming a large portion of the patient's day. Procedures at facilities closer to the patient's home may also consume a large portion of the patient's day. HHD can be performed at night or during the day, when the patient is relaxing, working, or otherwise productive.

[0009] Another type of renal failure therapy is peritoneal dialysis ("PD"), in which dialysis solution, also called dialysate, is infused through a catheter into a patient's peritoneal cavity. The dialysate contacts the peritoneal membrane within the patient's peritoneal cavity. Waste, toxins and excess water move from the patient's bloodstream through the capillaries in the peritoneum into the dialysate by diffusion and osmosis, i.e., an osmotic gradient is created across the membrane. An osmotic agent in the PD dialysate provides the osmotic gradient. Spent or spent dialysate is pumped out of the patient, removing waste, toxins and excess water from the patient. This cycle may be repeated, for example, multiple times.

[0010] There are various types of peritoneal dialysis therapy, including continuous ambulatory peritoneal dialysis ("CAPD"), automated peritoneal dialysis ("APD"), tidal flow dialysis, and continuous flow peritoneal dialysis ("CFPD"). CAPD is a manual dialysis procedure, in which a patient manually connects an implanted catheter to a drain to allow used or spent dialysate to drain from the peritoneal cavity. The patient then switches the fluid communication so that the patient catheter is in communication with a bag of fresh dialysate to infuse fresh dialysate through the catheter and into the patient. The patient disconnects the catheter from the bag of fresh dialysate and allows the dialysate to dwell in the peritoneal cavity, where the transfer of waste, toxins, and excess water occurs. After a 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.

[0011] Automated peritoneal dialysis ("APD") is similar to CAPD in that the dialysis treatment involves drain, fill and dwell cycles. However, APD devices perform these cycles automatically, usually while the patient sleeps. APD devices relieve the patient from having to perform treatment cycles manually and from having to transport supplies during the day. APD devices are fluidly connected to an implanted catheter, a source or bag of fresh dialysate, and a fluid drain. The APD device pumps fresh dialysate from the dialysate source through the catheter and into the patient's peritoneal cavity. APD devices also allow the dialysate to dwell within the cavity, allowing the transfer of waste, toxins and excess water to occur. The source may contain multiple liters of dialysate, including several solution bags.

[0012] APD machines pump used or spent dialysate from the patient's peritoneal cavity to drain through a catheter. As with the manual process, several drain, fill and dwell cycles occur during dialysis. A "last fill" may occur at the end of an APD treatment. The last fill may remain in the patient's peritoneal cavity until the start of the next treatment, or may be manually emptied at some point during the day.

[0013] APD patients may experience what is known as drain pain. The negative pressure applied to the patient's peritoneal cavity during drainage can cause pain, especially for new patients whose peritoneal cavity may be very sensitive. The pain level may reach a point where the patient no longer wishes to continue the APD procedure. Certain APD devices are configured to provide a negative pumping pressure using air or pneumatic pressure applied to the air side of one or more flexible membranes or diaphragms. The negative pressure draws the flexible membranes or diaphragms inward, and the spent PD fluid or effluent is pulled away from the patient along the fluid side of the flexible membranes or diaphragms. The negative air pressure applied is constant, which means that the applied pressure is the same regardless of non-constant conditions present in the patient.

[0014] The conditions present in the patient change. For example, assuming an overnight procedure in which the patient is asleep, the patient's sleeping position changes. Also, the amount of effluent present in the patient's peritoneal cavity changes during patient drainage. Each of these changing conditions affects the flow rate of spent PD fluid or effluent back along the patient line to the APD device. The flow rate affects the amount of pressure drop along the patient line, with higher flow rates resulting in higher pressure drop.

[0015] For example, in low flow patient conditions where the patient's sleep position somehow restricts drainage flow or the patient's peritoneal cavity is nearly empty creating a lack of effluent supply conditions, the corresponding pressure drop will be low. The constant negative pressure applied at both high and low drainage flows creates an environment of patient drain pain during low drainage flows.

[0016] Therefore, there is a need for an improved APD system that reduces or eliminates patient drainage pain. Summary of the Invention [Means for solving the problem]

[0017] overview The present disclosure describes an automated peritoneal dialysis ("APD") system that reduces or eliminates drain pain. The APD system includes an APD device or cycler. The APD device can deliver fresh heated PD fluid to the patient, for example, at 14 kPa (2.0 psig) or higher. The APD device can remove spent PD fluid or effluent from the patient, for example, at -9 kPa (-1.3 psig) or even greater negative pressure. The resulting flow rate to and from the patient can depend on several factors, including where the patient's height is located relative to the pumping portion of the APD device, the patient's sleeping position (assuming an overnight procedure), and the amount of effluent remaining in the patient's peritoneal cavity for patient drainage.

[0018] The pressure within the patient's peritoneal cavity is typically low, only somewhat above atmospheric pressure; for example, a typical patient full of 2 liters of PD fluid has an average peritoneal cavity pressure of about 12 cmH2O (approximately 8.8 mmHg, 1.18 kPa, 0.17 psig) according to C Brandes et al., "Optimization of Dialysate Flow and Mass Transfer During Automated Peritoneal Dialysis," AJKD Vol. 25, No. 4, April 1995. If there is an abundance of spent PD fluid or effluent in the peritoneal cavity at the start of the patient drain cycle, flow rates of 100-350 ml / min can be achieved by the APD device of the present disclosure. The flow rate depends on the relative elevation distance between the pumping portion of the APD device and the patient's peritoneal cavity. A relatively high flow rate creates a relatively high pressure drop in the patient line tubing, so that a negative pressure applied by the APD device, e.g., −9 kPa (−1.3 psig), will be significantly lower (less negative) at the distal or patient end of the patient line, e.g., about −1 kPa (−0.15 psig).

[0019] For example, problems may occur at the end of patient drainage. The effluent supply is low and the peritoneum may begin to wrap around the catheter, increasing the pressure drop between the inside of the patient's indwelling catheter and the peritoneal cavity, reducing the drain flow. The reduced drain flow rate reduces the pressure drop in the patient line. If the applied negative pressure remained at a high flow setting, e.g., -9 kPa (-1.3 psig), the negative pressure experienced by the patient would increase, which may lead to drain pain. In fact, if the drain flow rate were reduced to 0, the patient would experience full negative drain pressure, which may even be increased by the head height differential between the APD device and the patient's peritoneal cavity. The APD system of the present disclosure does not allow this to occur.

[0020] The APD system of the present disclosure employs an APD device that has the ability to regulate at least the applied negative pressure (and possibly the applied positive pressure) and measure at least the patient drain flow rate (and possibly the patient fill flow rate). During patient drain, a control unit for the APD device periodically checks the current flow rate (or periodically attempts to update the flow rate commanded by the control unit 60). The control unit uses the current flow rate to determine a corresponding pressure drop along the patient line. The corresponding pressure drop may be determined in a number of ways. Described herein are equations for determining the corresponding pressure drop based on certain known quantities related to the construction and materials used for the patient line, the viscosity and density of the PD fluid used (e.g., dependent on composition such as glucose content), the PD fluid temperature, and the measured PD fluid flow rate. The corresponding pressure drop may alternatively be determined using one or more lookup tables that correlate pressure drop to the measured flow rate. The lookup tables may be populated using the equations discussed herein.

[0021] Knowing the pressure drop for the current flow rate, the control unit adjusts the negative patient exhaust pumping pressure so that the resulting effluent pressure in the patient's peritoneal cavity is at a level that is likely not to cause drain pain, for example, at a resting patient full pressure of at or around 12 cmH2O (approximately 8.8 mmHg, 1.18 kPa, 0.17 psig). By periodically checking the current patient exhaust flow rate (or attempting to periodically update the patient exhaust flow rate commanded by the control unit 60) and updating the applied negative patient exhaust pressure, the control unit of the present system maintains a natural (patient full) patient pressure during each patient drain of a PD procedure. The overall effect is to reduce, perhaps significantly, the likelihood of patient drain pain.

[0022] The disclosed system and associated methodology is also advantageous because it allows drainage time to be reduced by pulling at a higher flow rate when effluent is abundant in the patient's peritoneal cavity. In a system that does not model pressure drop according to the present disclosure, the applied negative pressure may be limited to a safe negative pressure limit at the patient, e.g., -9 kPa (-1.3 psig or perhaps more negative due to head height), even at high flow rates selected so as not to damage the patient's peritoneum. By modeling the pressure drop along the patient line, the disclosed PD device may apply a higher negative pressure, e.g., -14 kPa (-2.0 psig), during times of high flow rates, knowing that the determined pressure drop will reduce the pressure at the patient to a safe level. Applying a higher pressure during times of high flow rates accelerates patient drainage and reduces the time required for drainage. Patient filling and draining has been reported to account for 35%-55% of the total procedure time, see Alp Akonour et al., "A Mathematical Model to Optimize the Drain Phase in Gravity-Based Peritoneal Dialysis Systems," Advances in Peritoneal Dialysis, Vol. 26, 2010. Thus, shortening patient drain time leaves more time for the patient dwell where the procedure is performed and / or shortens the overall procedure.

[0023] The system and associated methodology may also be advantageous because it may allow the cost of the patient line and associated disposable set to be lowered because the patient line is made of less expensive materials, the reason being the pressure drop optimization of the present disclosure minimizes the risk of collapsing the patient line while applying negative pressure to the patient.

[0024] In a first aspect of the present disclosure, which may be combined with any other aspect or portion thereof in light of the disclosure set forth herein without limiting the disclosure in any respect, a peritoneal dialysis ("PD") system includes a PD fluid pump, a patient line for receiving spent PD fluid pumped by the PD fluid pump during patient drain, a pressure sensor positioned and arranged to sense a negative pressure associated with the PD fluid pumped during patient drain, and a control unit configured to: (i) determine or know the flow rate of the PD fluid pumped during patient drain, (ii) determine an applied negative pressure at which the PD fluid pump will pump PD fluid during patient drain, the applied pressure being based on a pressure drop corresponding to the determined or known flow rate, and (iii) use the sensed negative pressure from the pressure sensor to cause the PD fluid pump to pump PD fluid at the applied negative pressure during patient drain.

[0025] 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 repeat (i) to (iii) multiple times over the patient discharge.

[0026] In a third aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to repeat (i) to (iii) on a time period basis or on a pump stroke number basis.

[0027] In a fourth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the PD fluid pump is pneumatically actuated and the pressure sensor is associated with an air pressure line positioned and arranged to deliver negative air pressure to the PD fluid pump.

[0028] In a fifth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to accumulate known volumetric strokes by the PD fluid pump and / or use an ideal gas law algorithm in determining the flow rate of PD fluid pumped during patient drainage.

[0029] In a sixth embodiment of the present disclosure, which may be combined with any other embodiment or portion thereof, the PD fluid pump is a peristaltic pump, a piston pump, or a pressure chamber pump, and a pressure sensor is associated with the patient line.

[0030] In a seventh aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to use an output from a flow meter associated with the patient line and / or accumulate known volumetric rotations by a peristaltic pump or accumulate known volumetric strokes by a piston pump in determining the flow rate of PD fluid to be pumped during patient drain.

[0031] In an eighth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to use an output from a scale for the pressure chamber pump in determining a flow rate of PD fluid to be pumped during patient drain.

[0032] 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 know the flow rate, which is the commanded flow rate.

[0033] In a tenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit calculates an allowable patient pressure P, assuming that the pressure drop is expressed as a positive value. ac By subtracting the pressure drop from c 設定点 =P ac -ΔP チューブ Negative pressure P applied by (Q) c 設定点 The method is configured to determine:

[0034] In an eleventh aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the acceptable patient pressure is a pressure that does not cause patient drain pain.

[0035] In a twelfth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, an applied negative pressure P c 設定点 =Pac +P ヘッド -ΔP チューブ (Q), wherein P ヘッド takes into account the head height differential between the patient's peritoneal cavity and the PD fluid pump, as determined by ρ×g×Δh.

[0036] In a thirteenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to determine the pressure drop using an algorithm that takes into account the determined or known flow rate, at least one characteristic of the patient line, and at least one characteristic of the PD fluid.

[0037] In a fourteenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the at least one characteristic of the patient line includes a patient line length, a patient line inner diameter, and a patient line surface roughness.

[0038] In a fifteenth embodiment of the present disclosure, which may be combined with any other embodiment or portion thereof, the at least one characteristic of the PD fluid includes a PD fluid density, a PD fluid viscosity, a PD fluid composition, and a PD fluid temperature.

[0039] In a sixteenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the algorithm depends on whether the PD fluid flow rate is laminar or turbulent.

[0040] In a seventeenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the algorithm further takes into account the head height differential between the patient's peritoneal cavity and the PD fluid pump.

[0041] In an eighteenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to determine the pressure drop using a look-up table correlating the pressure drop and the PD fluid flow rate.

[0042] 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 determine the applied negative pressure by taking into account a head height differential between the patient's peritoneal cavity and the PD fluid pump, and the control unit is configured to again take into account the head height differential between the patient's peritoneal cavity and the PD fluid pump when (i) the pressure sensor detects a threshold unintended PD fluid pressure change or (ii) the control unit determines that a threshold unintended PD fluid flow rate has occurred.

[0043] In a twentieth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to determine a head height differential between the patient's peritoneal cavity and the PD fluid pump by slowing or stopping the PD fluid pump at least once and reading the resulting output from the pressure sensor.

[0044] In a twenty-first aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to use the sensed negative pressure from the pressure sensor as feedback in a pressure control routine to cause the PD fluid pump to pump PD fluid at an applied negative pressure during patient drainage.

[0045] In a twenty-second aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a method for minimizing patient drain pain in a peritoneal dialysis (PD) system is disclosed. The method includes: (i) determining or knowing, by a control unit of the PD system, a flow rate of PD fluid pumped by a PD fluid pump of the PD system during patient drain, where a patient line of the PD system receives spent PD fluid; (ii) determining, by the control unit, an applied negative pressure at which the PD fluid pump will pump the PD fluid during patient drain, where the applied pressure is based on a pressure drop corresponding to the determined or known flow rate; and (iii) causing the PD fluid pump to pump the PD fluid at the applied negative pressure during patient drain based on a negative pressure associated with the PD fluid and sensed by a pressure sensor of the PD system.

[0046] In a twenty-third aspect of the present disclosure, which may be combined with any other aspect or portion thereof, one or more iterations of (i) through (iii) may be performed multiple times over the patient discharge by the control unit. Further, the one or more iterations are performed on a time period basis or a pump stroke number basis.

[0047] In a twenty-fourth embodiment of the present disclosure, which may be combined with any other embodiment or portion thereof, the method further includes accumulating known volumetric strokes by the PD fluid pump or using an ideal gas law algorithm in determining the flow rate of PD fluid pumped during patient drainage.

[0048] In a twenty-fifth embodiment of the present disclosure, which may be combined with any other embodiment or portion thereof, the PD fluid pump is a peristaltic pump, a piston pump, or a pressure chamber pump. A pressure sensor is associated with the patient line. The flow rate of the PD fluid pumped during patient drain is determined based on one or more of the output from a flow meter associated with the patient line, the accumulated known volumetric rotations by the peristaltic pump, the accumulated known volumetric strokes by the piston pump, or the output from a scale of the pressure chamber pump.

[0049] In a twenty-sixth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, an applied negative pressure, P c 設定点 is the allowable patient pressure P, assuming the pressure drop is expressed as a positive value. ac By subtracting the pressure drop from c 設定点 =P ac -ΔP チューブ (Q) is the factor that determines the degree of freedom of movement.

[0050] In a twenty-seventh aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the pressure drop is determined using an algorithm that takes into account a determined or known flow rate, at least one characteristic of the patient line, and at least one characteristic of the PD fluid.

[0051] In a twenty-eighth embodiment of the present disclosure, which may be combined with any other embodiment or portion thereof, the pressure drop is determined using a look-up table correlating pressure drop with PD fluid flow rate.

[0052] In a twenty-ninth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the applied negative pressure is determined by taking into account a head height differential between the patient's peritoneal cavity and the PD fluid pump. The method further includes retaking into account the head height differential between the patient's peritoneal cavity and the PD fluid pump when (i) a threshold unintended PD fluid pressure change is detected or (ii) a threshold unintended PD fluid flow rate occurs.

[0053] In a thirtieth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the head height differential between the patient's peritoneal cavity and the PD fluid pump is determined by slowing or stopping the PD fluid pump at least once and reading the resulting output from the pressure sensor.

[0054] In a thirty-first aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the method further includes causing the control unit to use the sensed negative pressure from the pressure sensor as feedback in a pressure control routine to cause the PD fluid pump to pump PD fluid at the applied negative pressure during patient drainage.

[0055] In a thirty-second aspect of the present disclosure, which may be combined with any other aspect or portion thereof, any of the features, functionality, and alternative forms described in association with any one or more of Figures 1 to 4B may be combined with any of the features, functionality, and alternative forms described in association with any other of Figures 1 to 4B.

[0056] In light of the above aspects and the disclosure described herein, one advantage of the present disclosure is to provide a system and method for an automated peritoneal dialysis ("APD") cycler that minimizes patient drain pain.

[0057] Another advantage of the present disclosure is to provide a system and method for an APD cycler that increases patient exhaust flow rates and decreases patient exhaust times, increasing available patient dwell time and / or decreasing overall treatment times.

[0058] A further advantage of the present disclosure is to provide a system and method for an APD cycler that enables cheaper patient lines and corresponding disposable sets.

[0059] Further features and advantages are described in and will be apparent from the following detailed description and figures. The features and advantages described herein are not all-inclusive, and in particular many further features and advantages will be apparent to those skilled in the art in view of the drawings and description. Also, it is not necessary for any particular embodiment to have all the advantages described herein, and it is expressly contemplated to separately claim each advantageous embodiment. Furthermore, it should be noted that the language used in this specification has been selected primarily for ease of reading and explanation, and is not intended to limit the scope of the subject matter of the present invention. [Brief description of the drawings]

[0060] BRIEF DESCRIPTION OF THE DRAWINGS [Figure 1] FIG. 1 is a cross-sectional schematic diagram of one embodiment for an APD system having a methodology for minimizing patient drain pain of the present disclosure.

[0061] [Diagram 2] FIG. 2 is a plot of patient line pressure drop versus drainage flow rate for several different types of PD fluid drained at a typical APD flow rate.

[0062] [Diagram 3] FIG. 3 is a schematic diagram illustrating one possible control hierarchy for controlling an electromechanical pump (eg, piston or peristaltic) to manage pressure in a patient according to the present disclosure.

[0063] [Figure 4A] 4A and 4B are schematic diagrams of a PD machine, patient and patient line illustrating how patient head height is taken into account in determining the negative pressure drain set point of the dialysis machine. [Figure 4B] 4A and 4B are schematic diagrams of a PD machine, patient and patient line illustrating how patient head height is taken into account in determining the negative pressure drain set point of the dialysis machine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0064] Detailed Description Referring now to the drawings, and in particular to FIG. 1, an exemplary system 10 including the patient drain pain reduction methodology of the present disclosure is illustrated. The system 10 includes a dialysis machine 20, such as an APD machine, that operates a medical fluid handling device 70, such as a dialysate cassette. The PD machine 20 includes a housing 22 that defines a pump interface 24 having a pump actuator or pump actuation region 26 for actuating the medical fluid handling device 70. The pump actuation region 26 in the illustrated embodiment is pneumatically actuated via a positive air pressure line 28 extending from a positive air pressure source 30 to perform a pump-out or delivery stroke, for example, to (i) push fresh heated dialysate to the peritoneal cavity 14 of the patient 12 via the patient line 16 and the patient transfer set 18, (ii) push fresh dialysate to a heating reservoir (not shown) where it is heated by a dialysate heater (not shown) to body temperature, e.g., 37° C., or (iii) push spent dialysate to a drain. The pump actuation region 26 in the illustrated embodiment is pneumatically actuated via a negative air pressure line 32 extending from a negative air pressure source 34 to perform a pump-in or pull-in stroke, for example, to pull (i) fresh dialysate from a dialysate source 40 through a supply line 42, (ii) fresh heated dialysate from a heating vessel (not shown), or (iii) spent dialysate from the peritoneal cavity 14 of the patient 12 via the patient line 16 and transfer set 18.

[0065] The patient line 16 may be 3 to 7 meters in length, for example, approximately 4.5 or 6.7 meters, and may have an internal diameter of, for example, 3 to 4 millimeters. In the formulas described herein, different disposable patient lines 16 are assumed to have and provide the same basic behavior from procedure to procedure.

[0066] The PD device 20 also provides a pressure sensor 44 for measuring the positive air pressure in the positive air pressure line 28, and a pressure sensor 46 for measuring the negative air pressure in the negative air pressure line 32. The PD device 20 further includes a plurality of electrically powered pneumatic valves, e.g., valve 48, valve 50, valve 52, and valve 56. The pneumatic valve 48 is positioned in the positive air pressure line 28 to selectively allow positive pressure from the source 30 to reach the pumping region 26. The pneumatic valve 50 is positioned in the negative air pressure line 32 to selectively allow negative pressure from the source 34 to reach the pumping region 26. A relief valve 52 is provided in a vent line 54 in communication with the positive air pressure line 28 to selectively vent the positive pressure in the line 28 and the pumping region 26 to atmosphere. A second relief valve 56 is provided in a vent line 58 in communication with the negative air pressure line 32 for selectively venting the negative pressure in line 32 and pumping region 26 to atmosphere. In an alternative embodiment, a single relief valve and line may be provided to vent both positive and negative pressure from pumping region 26 to atmosphere.

[0067] 1 further illustrates that the PD device 20 includes a positive air pressure regulator 66, e.g., a variable orifice valve, located along the positive air pressure line 28, and a negative air pressure regulator 68, e.g., a variable orifice valve, located along the negative air pressure line 32. The positive air pressure regulator 66 sets the positive air pressure delivered to the pumping region 26 at a desired controlled level, which is also the pressure of the fresh or spent PD fluid being pumped out of the dialysate cassette 70. The negative air pressure regulator 68 sets the negative air pressure drawn at the pumping region 26 at a desired controlled level, which is also the pressure of the fresh or spent PD fluid being pumped into the dialysate cassette 70. In an alternative embodiment, the PD device 20 may be pneumatically configured such that a single pressure regulator, e.g., a variable orifice valve, operates as the positive air pressure regulator and the negative air pressure regulator at any given time.

[0068] The pressure sensors 44, 46, pneumatic valves 48, 50, 52, 56, and variable orifice valves or regulators 66, 68 output to or are under the control of a control unit 60 of the PD device 20. The control unit 60 in the illustrated embodiment includes one or more processors 62 and one or more memories 64. The control unit 60 may have any one or more of a master controller, a safety controller, a video controller, and / or a sub-controller or delegate controller. The control unit 60 receives pressure readings from the pressure sensors 44, 46 and selectively opens and closes the pneumatic solenoid valves 48, 50, 52, 56 at programmed times or stages. The control unit 60 uses the outputs of the pressure sensors 44, 46, respectively, in a pressure control routine to control the variable orifice valves or regulators 66, 68 to deliver positive and negative air pressure at desired or commanded levels. It should be understood that the control unit 60 may operate with additional pressure sensors, temperature sensors, valves, and PD fluid heaters, which are not shown to simplify FIG.

[0069] 1, a medical fluid handling device or disposable cassette 70 includes a pump actuation chamber 72 that mates with pump actuation region 26 to form an overall pumping chamber. Medical fluid handling device 70 in the illustrated embodiment includes a flexible membrane, diaphragm or sheet 74 that is sized to fit within pump actuation chamber 72 or (as shown) to cover the entire side of medical fluid handling device 70, with a portion of membrane 74 covering pump actuation chamber 72, which portion may be at least substantially flat or may be pre-domed or pre-shaped to fit within one or both of pump actuation region 26 and pump actuation chamber 72. The flexible membrane 74 (or separate membranes) may also be used to cover and actuate medical fluid valves (not shown), such as (i) a fluid valve positioned and arranged to selectively allow medical fluid to flow from the fluid source 40, through the supply line 42 and the supply flow path 76 of the medical fluid handling device 70 to the pump actuation chamber 72, and (ii) a fluid valve positioned and arranged to selectively allow medical fluid to flow from the pump actuation chamber 72, through a patient flow path 78 of the medical fluid handling device 70, through the patient line 16 and the patient transfer set 18 to the peritoneal cavity 14 of the patient 12. It should be understood that the medical fluid handling device 70 may have additional fluid valves, not shown to simplify FIG. 1 , such as additional fluid valves for additional pump actuation chambers 72 (which operate in alternating fashion to provide a more continuous flow) and additional fluid valves for multiple supply lines 42, fluid heater lines, and / or drain lines.

[0070] The control unit 60 causes negative pressure from the source 34 to be applied to the flexible membrane 74, pulling the sheet against the wall of the pump actuation region 26 and correspondingly drawing fresh or used PD fluid into the pump actuation chamber 72. To do so, the control unit causes valves 48, 52, 56 to close and valve 50 to open. During filling of the pump actuation chamber 72, the pressure sensor 46 measures the negative pumping pressure, which is used as feedback in the pressure control routine to set the level of negative air pressure applied at the pump actuation region 26 via the negative pressure regulator 68.

[0071] The control unit 60 causes positive pressure from the source 30 to be applied to the flexible membrane 74 to press the sheet against the wall of the pump actuation chamber 72 and correspondingly force fresh or used PD fluid out of the pump actuation chamber 72. To do so, the control unit causes valves 50, 52, 56 to close and valve 48 to open. During discharge of the pump actuation chamber 72, the pressure sensor 44 measures the positive pumping pressure, which is used as feedback in the pressure control routine to set the level of positive air pressure applied at the pump actuation region 26 via the positive pressure regulator 66.

[0072] The control unit 60 can determine the flow rates of fresh and spent PD fluid pumped by the PD device 20 of the system 10 in at least one of a number of different ways. In one method, the fixed volume pump actuation region 26 and pump actuation chamber 72 collectively form a known full stroke volume. The control unit 60 counts the number of full strokes delivered, multiplies the count by the known full stroke volume, and divides the result by the corresponding time required to make the number of full strokes delivered to determine the local or current PD fluid flow rate.

[0073] Alternatively or additionally, the control unit 60 may obtain pressure measurements before and after the fill or discharge stroke and determine the resulting volume of fresh or spent PD fluid drawn into or expelled from the pump actuation chamber 72 using an ideal gas law algorithm, as known in the art. To that end, the PD device 20 may provide positive and negative reference chambers (not shown) of known fixed volume, which may be pneumatically connected to the positive and negative vent lines 54, 58, respectively. The control unit 60 may then sum the volumes of successive fill or discharge strokes determined by the ideal gas law algorithm and divide the sum by the corresponding time required to perform successive fill or discharge strokes to determine the local or current PD fluid flow rate. The ideal gas law algorithm method of determining the local or current flow rate is advantageous because a full stokes of the diaphragm or seat 74 through the pump actuation region 26 and pump actuation chamber 72 is not required. Partial strokes may be performed and taken into account in determining the local or current flow rate.

[0074] It should be appreciated that the PD device 20 likely provides two pump actuation regions 26 and pump actuation chambers 72 that operate in alternating fashion (one filling and the other discharging) such that the flow rate of fresh or used PD fluid is for the most part continuous.

[0075] As discussed herein, applying constant negative pressure during patient drainage can lead to patient drain pain during periods of low flow. Low flow of effluent or spent PD fluid can occur at any time during patient drainage, for example, due to partial blockage of the patient line 16. At the end of patient drainage, low drainage flow can also occur. The supply of effluent is low and the peritoneum can begin to wrap around the catheter, increasing the pressure drop between the interior of the patient's indwelling catheter and the peritoneal cavity 14, decreasing the drainage flow. The decrease in drainage flow decreases the pressure drop in the patient line 16. If the applied negative pressure remained at, for example, -9 kPa (-1.3 psig), the pressure experienced by the patient would increase negatively, which could eventually lead to drainage pain.

[0076] To combat drain pain, the control unit 60 of the APD system 10 of the present disclosure is programmed with the ability to at least adjust the applied negative pressure (and applied positive pressure), as described above, and to measure at least the patient drain flow rate (and patient fill flow rate), as described above. During patient drain, the control unit 60 is programmed to periodically determine the current flow rate (e.g., once every set period, such as 5-60 seconds, or once every set number of pump strokes, such as 1-5 strokes), for example in the manner described above. The control unit 60 alternatively attempts to periodically update the commanded flow rate. The control unit 60 uses the current flow rate, in either scenario, to determine the corresponding pressure drop along the patient line 16. The corresponding pressure drop may be determined using the following equation:

[0077] The corresponding pressure drop through the patient line 16 can be determined starting from the friction head height equation, see Frank M. White, Fluid Mechanics, 2011. [ka] term h fis the friction head height in meters (“m”), f is the Darcy friction coefficient (described below), L is the length of the patient line 16 in meters, d is the inner diameter of the patient line 16 in meters, V is the velocity of the PD fluid in meters / second (equal to the determined flow rate divided by the inner area of ​​the patient line 16), and g is the flow rate in meters / second. 2 is the gravity of the Earth in units of m 3 is the determined current volumetric PD fluid flow rate in / sec.

[0078] The following formula can be used to derive the pressure drop from the head height: [ka] where ΔP is the pressure drop in kPa and ρ is the pressure drop in kilograms ("kg") / m 3 is the density of the liquid in units of PD. Combining the two equations gives: [ka]

[0079] The Darcy friction factor depends on the Reynolds number ("Re"), a dimensionless value used in flow mechanics, and the relative roughness (ε / d) of the inner diameter of the patient line 16, where ε is the effective roughness height of the patent line in meters and d is the inner diameter of the patient line 16 in meters. For flow in the patient line 16 during laminar flow conditions, the Darcy coefficient can be calculated using the following formula: [ka] The Reynolds number can be calculated by the following formula: [ka] where μ is the dynamic viscosity of the PD fluid in kg / m×s. If the flow in the patient line 16 is turbulent, i.e., at Reynolds numbers above 4000, the turbulent model of the Darcy friction factor applies. For fully steady turbulent flow, the Colebrook-White equation may be used to calculate the friction factor in the turbulent region. [ka] The above equation may be solved numerically or approximated using the following equation (Harland): [ka]

[0080] The Harland equation has been simulated for Reynolds numbers ranging from 2300 to 100000, among others, see Jukka Kiijarvi, Lunowa Fluid Mechanics Paper 11027, July 29, 2011. The Harland equation is said to result in an error in the Darcy friction coefficient f of about 2%, which is acceptable, especially considering that the dimensions and surface quality of the patient line 16 are consistent from procedure to procedure. Assuming that the patient line 16 is made of polyvinyl chloride ("PVC"), the surface roughness ε of PVC drawn pipe (and other drawn pipe materials) can be taken to be 0.0015 mm.

[0081] Flow in the patient line 16 having a Reynolds number between 2300 and 4000 is considered to be transient. The friction factor here is f 層流 and f 乱流 It will be somewhere in between.

[0082] As described above, the pressure drop ΔP may be determined knowing the length, inner diameter, and surface roughness of the patient line 16, the dynamic viscosity and density of the PD fluid (e.g., based on PD fluid composition such as glucose levels), and the determined local or current PD fluid flow rate. The PD fluid temperature may also be taken into account. The above formulas (or at least a portion thereof) may be stored in one or more memories 64 and accessed by one or more processors 62 of the control unit 60 to calculate the local or current pressure drop ΔP based on the newly determined flow rate. It should be understood that the current flow rate may not need to be calculated based on, for example, stroke volume and stroke count, but may instead be a known commanded flow rate set in the memory 64 of the control unit 60. The formula stored in the memory to calculate the pressure drop ΔP may now use the flow rate currently commanded by the control unit 60.

[0083] The pressure drop ΔP corresponding to the newly determined (or currently commanded) flow rate may alternatively be determined using one or more lookup tables stored in memory 64 that correlate pressure drop to measured flow rate. The lookup tables may be populated using the equations discussed herein. Sample lookup tables for common PD fluids and typical PD fluid flow rates are shown in Table 1, where the loaded values ​​are pressure drop ΔP values. [Table 1]

[0084] FIG. 2 is essentially a plot of Table 1 showing how the pressure drop ΔP changes as a function of flow rate for four different types of PD fluids, which have various densities and viscosities based on their different chemical compositions. Each PD fluid consistently shows that the pressure drop ΔP increases as the flow rate increases. FIG. 2 illustrates that at high flow rates, almost all of the negative pressure generated by the PD device 20 is dissipated over the length of the patient line 16. Thus, the pressure within the patient's peritoneal cavity 14 is now close to its normal pressure, e.g., slightly higher than atmospheric pressure. When the control unit 60 detects that the drain flow rate is about 350 ml / min, the control unit 60 can apply a negative drain pressure at about −9 kPa (−1.3 psig) as discussed herein. When the control unit 60 detects that the flow rate has decreased to, e.g., 250 ml / min, the control unit 60 reduces the commanded negative drain pressure to about −5 kPa (−0.73 psig). As the drainage flow rate falls further, the control unit 60 will need to further reduce the commanded negative pressure to avoid the patient potentially experiencing drain pain.

[0085] It should be understood that Table 1 and FIG. 2 illustrate an example where the PD device 20 is at approximately the same head height as the patient's peritoneal cavity. In situations where the head height is different (the height of the PD device 20 is located above the patient) so as to work against the ability of the PD device 20 to remove effluent from the patient, even a lower flow rate of −9 kPa (−1.3 psig) may be required. To initially establish the flow rate, taking into account the head height, the control unit 60 is programmed in one embodiment to cause the pumping region 26 of the PD fluid pump to begin drawing in and draining effluent at a lower flow rate. The control unit 60 determines the resulting flow rate and thus knows whether the patient is relatively full and the flow rate is high, or the flow rate is low for some reason, e.g., the patient is not full. If the patient is relatively full and the flow rate is high, the control unit 60 increases the negative drain pressure using the formulas discussed herein to drain the patient more quickly while avoiding patient drain pain.

[0086] Knowing the pressure drop for the current flow rate, the control unit 60 is programmed in one embodiment to adjust the negative patient exhaust pumping pressure so that the resulting effluent pressure in the patient's peritoneal cavity 14 is at a level that is likely not to cause drain pain, for example at or around a resting patient full pressure of 12 cmH2O (approximately 8.8 mmHg, 1.18 kPa, 0.17 psig). By periodically checking the current patient exhaust flow rate (or attempting to periodically update the flow rate commanded by the control unit 60) and updating the applied negative patient exhaust pressure, the control unit 60 of the present system 10 maintains a natural (patient full) patient pressure during each patient drain of a PD procedure. The overall effect is to reduce, perhaps significantly, the likelihood of patient drain pain.

[0087] In an alternative embodiment, the control unit 60 is programmed to initiate patient drain by applying a low negative drain pressure, such as -1 kPa (-0.15 psig). Thereafter, if the control unit 60 detects that the flow rate is above a first threshold, for example 75 ml / min, the commanded negative pressure is increased by an incremental amount, for example -2 kPa (-0.29 psig). Alternatively, if the control unit 60 detects that the flow rate is below a second threshold, for example 50 ml / min, the control unit maintains the negative pressure at -1 kPa (-0.15 psig). The control unit 60 may command that a negative pressure of -2 kPa (-0.29 psig) be used over the linear range of FIG. 2, for example below 300 ml / min. When the flow rate increases to or beyond the linear range breakpoint, e.g., 300 ml / min, or a minimum negative pressure in the peritoneal cavity 14 is reached, the control unit 60 may begin using the stored formula described above.

[0088] The control unit 60 in this alternative embodiment is programmed such that at the maximum patient drainage flow rate (e.g., maximum commanded flow rate), the pressure in the patient's peritoneal cavity 14 or abdominal cavity ("ac") is calculated and used as a set point for the remaining drainage phase. Such pressure is P ac When the patient exhaust flow rate begins to decrease, the control unit 60 calculates the pressure drop ΔP for the current flow rate. チューブ (Q) (or use a look-up table). The control unit 60 then calculates P c 設定点 =P ac -ΔP チューブ The pressure drop and pressure P are ac By summing with the applied pressure or set point pressure (P c 設定点 ) to calculate

[0089] In one example using the values ​​in Table 1, assume that the maximum flow rate at -9 kPa applied using (using Dianeal™ 2.26%) is 350 ml / min. ac Therefore, −9 kPa+8.42 kPa=−0.58 kPa, and therefore −0.58 kPa is used as the tolerable patient pressure for the remainder of the treatment, i.e., the patient pressure remains at or about −0.58 kPa throughout the remaining patient discharge. c 設定点 ) is varied by the control unit 60 in response to a measured or commanded flow rate. c 設定点 starts at -9kPa and becomes less and less negative as the patient outlet flow (and corresponding drop) decreases. Thus, patient pressure remains constant (or nearly constant) and there is no pain.

[0090] The above equation again assumes that the PD device 20 is at the same height as the patient's peritoneal cavity, and therefore the differential head height is zero. Extending the above equation to take head height into account, the equation becomes: P c 設定点 =P ac +P ヘッド -ΔP チューブ (Q), where Pヘッド is determined by ρ×g×Δh, where Δh represents where the patient's peritoneal cavity is located relative to the PD device 20. For example, if the peritoneal cavity is located 0.5 meters ("m") below the PD device 20, then h=-0.5m, and therefore P ヘッド is approximately -5 kPa. The resulting set point pressure is P c 設定点 =P ac +(-5)-4=P ac If instead the patient is positioned 0.5 m above the PD device 20, the set point pressure obtained at the same flow rate is P c 設定点 =P ac +5-4=P ac +1 kPa (where the head height aids in patient evacuation).

[0091] The above example illustrates that the system 10 of the present disclosure takes into account the relative height between the location of the pump actuator or pump actuation region 26 of the PD device 20 and the location of the peritoneal cavity 14 of the patient 12 illustrated in Figure 1. For example, with a head height differential of 0.5 meters, (i) the pump actuator or pump actuation region 26 being below the peritoneal cavity 14 allows the PD device 20 to reduce its suction pressure by a difference of about 5 kPa, and (ii) the pump actuator or pump actuation region 26 being above the peritoneal cavity 14 allows the PD device 20 to increase its suction pressure by a difference of about 5 kPa. The pressure experienced by the peritoneal cavity 14 is the same in both cases.

[0092] 4A and 4B show the resulting discharge set point pressure P c 設定点 4A and 4B illustrate an embodiment for taking the patient head height into account in determining P. FIGS. 4A and 4B diagrammatically illustrate that the PD device 20 of the system 10 includes a patient line 16 that connects to the peritoneal cavity 14 of the patient 12. In FIG. 4A, the peritoneal or abdominal cavity 14 of the patient 12 is located a distance -h below the PD device 20. Thus, the PD device 20 must pull against the patient head height differential to provide additional negative exhaust pressure. Thus, the negative exhaust set point pressure is Pc 設定点 =P ac -ΔP チューブ (Q)+P(-h), where P(h)=ρ×g×Δh. In FIG. 4B, the peritoneal or abdominal cavity 14 of the patient 12 is located a distance +h above the PD device 20. Thus, the PD device 20 is assisted by the patient head height differential in drawing effluent from the patient during drainage. The negative set point drain pressure is now P c 設定点 =P ac -ΔP チューブ (Q) + P(h), where P(h) = ρ × g × Δh.

[0093] To determine the head height differential, the PD device 20 of the system 10 in one embodiment asks the patient 12 prior to treatment to input (i) whether the patient's stomach region is above or below the pump actuator or pump actuation region 26 (a horizontal line may be placed on the front of the PD device housing 22 as a reference), and (ii) by how much (e.g., entered in centimeters, meters, inches, or feet). The control unit 60 of the PD device 20 of the system 10 alternatively or additionally determines the head height differential by taking a pressure measurement with the pressure sensor(s) 44, 46 (or an in-line pressure sensor in the electromechanical pump actuator 26) when the PD fluid flow rate is zero. Here, if the patient is above the PD device 20, the pressure measurement is positive. If the patient is below the PD device 20, the pressure measurement is negative. The magnitude of the negative or positive pressure measurement indicates how far above or below the PD device 20, respectively.

[0094] During pumping, if (i) pressure sensor(s) 44, 46 (or another one or pressure sensors) senses a significant or threshold unintended PD fluid pressure change, or (ii) control unit 60 determines that a significant or threshold unintended PD fluid flow rate change has occurred, control unit 60 may stop operation of pump actuator or pump actuation region 26 such that PD fluid flow rate is zero and reacquire head height determination pressure measurements. Control unit 60 then adjusts the pressure set point based on the new head height differential determined. In an alternative embodiment, control unit 60 only slows down the PD fluid flow rate (e.g., one or more times) in an attempt to distinguish between a change in head height differential and an occlusion in patient line 16. If the sensed pressure remains constant despite changes in PD fluid flow rate (or unexpected changes in response to changes in patient head height), the control unit 60 determines that the original sensed pressure change is due to an occlusion, such as an occlusion due to omental coverage, catheter migration / blockage, or movement of the patient 12 blocking the patient line 16 (FIG. 1), each of which causes a change in the drain profile. If the sensed pressure changes as a function of the PD fluid flow rate change, the control unit 60 determines that the original sensed pressure change is due to a change in head height between the peritoneal cavity 14 and the pump actuation region 26. The control unit 60 then adjusts the pressure set point based on a new head height differential determined by one or more decelerations of the PD flow rate and the corresponding measured pressure(s). With reference to FIG. 1, it should be appreciated that locating one or more pressure sensors along the patient flow path 78 immediately upstream of the patient line 16 allows the patient head height to be continuously monitored regardless of the type of pumping provided, e.g., piston pumping, pneumatic pumping, peristaltic pumping, etc.

[0095] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Accordingly, such changes and modifications are intended to be covered by the appended claims. For example, although the PD device 20 is illustrated as a pneumatically operated PD device, the system 10 may alternatively use different types of PD fluid pumping (and valving), e.g., peristaltic pumping, piston pump pumping, or pumping using a PD fluid pump with a pressure chamber. Here, the control unit 60 of the system 10 may use multiple proportional, integral, derivative ("PID") control loops, such as an "inner" control loop and an "outer" control loop, sometimes referred to as a cascade controller. The inner control loop may, for example, use "rigid" control of the PD fluid flow rate. The outer control loop may instead provide a set point based on measured pressure. The overall compliance, such as the length of the patient line 16, dampens the vibrations of the stiffness-controlled electromechanical pump (e.g., piston or peristaltic) and allows a uniform pressure to be delivered to the patient.

[0096] FIG. 3 illustrates an example of multiple control loops that may be used to control an electromechanical pump (e.g., piston or peristaltic) to manage pressure in a patient to reduce or eliminate drainage pain as described herein. FIG. 3 illustrates that the electromechanical pump control scheme includes an inner loop that may be referred to as a fast control loop, including C2 and process P2. C2 is the electromechanical pump motor driver (electrical circuit) and inputs the motor shaft revolutions per minute ("RPM") set point. The output of the inner loop from a summation circle with disturbance d2 is y2, which represents the PD fluid flow, which may be taken as, for example, 0.5 ml per revolution in process P2 of the inner loop for a piston pump.

[0097] Thus, the inner loop of the electromechanical pump control scheme of Figure 3 is a direct high speed conversion from motor shaft RPM to flow rate (ml / min) (for electromechanical pump actuator 26) taking into account disturbances d2. Disturbances d2 may be any disturbance that affects the inner loop process P2. Possible examples include (i) a shift in the supply voltage to the motor driver of the electromechanical pump actuator 26, e.g., a drop in supply voltage from 24.7VDC to 23.4VDC due to a dialysate heater being energized, and (ii) stroke volume changes, e.g., a drop in stroke volume from 1ml / stroke to 0.9ml / stroke for a peristaltic pump actuator 26 whose pumping tubing segments wear over time.

[0098] The outer loop of the electromechanical pump control scheme of FIG. 3 controls pressure by providing an RPM set point to the inner loop. Process P1 is an outer loop process that describes how PD fluid flow rate corresponds to PD fluid pressure, which in one embodiment is filtered by a low pass filter. The low pass filter and the compliance of the patient line 16 form process P1, and C1 is a controller that controls the pressure accordingly (e.g., using PID pressure control). Disturbance d1 may be any disturbance that affects the process P1 of the outer loop. One possible example here includes PD fluid pressure fluctuations due to patient movement. The initial set point input (left-most signal) is the pressure set point by the electromechanical pump PD device or cycler 20. In FIG. 3, the inner loop controls the speed (e.g., RPM) of the electromechanical pump actuator 26, which is directly coupled to the flow (e.g., by a fixed stroke volume). The outer loop control pressure y1 is the output of the overall controller of FIG. 3, which is a function of the effect of the inner loop.

[0099] Alternative pumping, e.g., pressure chamber pumping, may also be used with one or more scales outputting to the control unit 60 so that the amount of fresh PD fluid delivered to the patient and the amount of spent PD fluid withdrawn from the patient may be known. If desired, the fresh or spent PD fluid weight change may be divided by a corresponding duration to determine the current or local fresh or spent PD fluid flow rate. In such alternative pumping embodiments, one or more pressure sensors outputting to the control unit 60 may be positioned to sense positive and negative PD fluid pressures along the patient line 16. The one or more pressure sensors may be pod-type sensors or strain gauge-type sensors in direct contact with the patient line 16. The PD fluid flow rate may be determined from a flow meter associated with the patient line 16 and / or by accumulating (for the most part) peristaltic pump revolutions of a known volume or accumulating piston pump strokes of a known volume and dividing by the corresponding duration required to make such a revolution or stroke.

Claims

1. 1. A peritoneal dialysis ("PD") system comprising: A PD liquid pump; a patient line for receiving spent PD fluid pumped by the PD fluid pump during patient drainage; a pressure sensor positioned and arranged to sense a negative pressure associated with the PD fluid being pumped during the patient drain; a control unit configured to: (i) determine or know a flow rate of the PD fluid to be pumped during the patient drain; (ii) determine an applied negative pressure at which the PD fluid pump will pump the PD fluid during the patient drain, the applied pressure being based on a pressure drop corresponding to the determined or known flow rate; and (iii) use the sensed negative pressure from the pressure sensor to cause the PD fluid pump to pump the PD fluid at the applied negative pressure during the patient drain; A PD system comprising:

2. The PD system of claim 1 , wherein the control unit is configured to repeat (i) through (iii) multiple times over the patient discharge.

3. The PD system of claim 2 , wherein the control unit is configured to repeat (i) through (iii) on a time period basis or on a pump stroke number basis.

4. 10. The PD system of claim 1, wherein the PD fluid pump is pneumatically actuated and the pressure sensor is associated with an air pressure line positioned and arranged to deliver negative air pressure to the PD fluid pump.

5. 5. The PD system of claim 4, wherein the control unit is configured to accumulate known volumetric strokes by the PD fluid pump and / or use an ideal gas law algorithm in determining the flow rate of the PD fluid pumped during the patient drain.

6. The PD system of claim 1 , wherein the PD fluid pump is a peristaltic pump, a piston pump, or a pressure chamber pump, and the pressure sensor is associated with the patient line.

7. 7. The PD system of claim 6, wherein the control unit is configured to use an output from a flow meter associated with the patient line and / or to accumulate known volumetric rotations by the peristaltic pump or to accumulate known volumetric strokes by the piston pump in determining the flow rate of the PD fluid pumped during the patient drain.

8. 7. The PD system of claim 6, wherein the control unit is configured to use an output from a scale for the pressure chamber pump in determining the flow rate of the PD fluid pumped during the patient drain.

9. The PD system of claim 1 , wherein the control unit is configured to know the flow rate, which is a commanded flow rate.

10. The control unit calculates the acceptable patient pressure P, assuming the pressure drop is expressed as a positive value. ａｃ By subtracting the pressure drop from P ｃ 設定点 =P ａｃ -ΔP チューブ (Q) applies the negative pressure P ｃ 設定点 The PD system of claim 1 configured to determine:

11. The PD system of claim 10 , wherein the acceptable patient pressure is a pressure that does not cause patient exhaustion pain.

12. The applied negative pressure is P ｃ 設定点 =P ａｃ +P ヘッド -ΔP チューブ (Q), wherein P ヘッド 11. The PD system of claim 10, wherein a head height difference between the patient's peritoneal cavity and the PD fluid pump is taken into account such that is determined by ρ×g×Δh.

13. 2. The PD system of claim 1, wherein the control unit is configured to determine the pressure drop using an algorithm that takes into account the determined or known flow rate, at least one characteristic of the patient line, and at least one characteristic of the PD fluid.

14. The PD system of claim 13 , wherein the at least one characteristic of the patient line includes a patient line length, a patient line inner diameter, and a patient line surface roughness.

15. 14. The PD system of claim 13, wherein the at least one characteristic of the PD fluid includes a PD fluid density, a PD fluid viscosity, a PD fluid composition, and a PD fluid temperature.

16. The PD system of claim 13 , wherein the algorithm depends on whether the PD fluid flow rate is laminar or turbulent.

17. 14. The PD system of claim 13, wherein the algorithm further takes into account a head height differential between the patient's peritoneal cavity and the PD fluid pump.

18. The PD system of claim 1 , wherein the control unit is configured to determine the pressure drop using a look-up table correlating pressure drop and PD fluid flow rate.

19. 2. The PD system of claim 1, wherein the control unit is configured to determine the applied negative pressure by taking into account a head height differential between the patient's peritoneal cavity and the PD fluid pump, and wherein the control unit is configured to re-take into account the head height differential between the patient's peritoneal cavity and the PD fluid pump when (i) the pressure sensor detects a threshold unintended PD fluid pressure change or (ii) the control unit determines that a threshold unintended PD fluid flow rate has occurred.

20. 20. The PD system of claim 19, wherein the control unit is configured to determine the head height differential between the patient's peritoneal cavity and the PD fluid pump by slowing or stopping the PD fluid pump at least once and reading the resulting output from the pressure sensor.

21. 2. The PD system of claim 1, wherein the control unit is configured to use the sensed negative pressure from the pressure sensor as feedback in a pressure control routine to cause the PD fluid pump to pump the PD fluid at the applied negative pressure during the patient drain.

22. 1. A control unit for minimizing patient drainage pain in a peritoneal dialysis (PD) system, the control unit comprising: (i) determining or knowing the flow rate of PD fluid pumped by a PD fluid pump of the PD system during patient drain, wherein a patient line of the PD system receives spent PD fluid; (ii) determining an applied negative pressure at which the PD fluid pump will pump the PD fluid during the patient drain, the applied pressure being based on a pressure drop corresponding to the determined or known flow rate; (iii) causing the PD fluid pump to pump the PD fluid at the applied negative pressure during the patient drain based on a negative pressure associated with the PD fluid and sensed by a pressure sensor in the PD system; The control unit is configured to:

23. A control unit as described in claim 22, configured to perform one or more repetitions of (i) to (iii) multiple times throughout the patient discharge, and the control unit configured to perform the one or more repetitions on a time period basis or a pump stroke count basis.

24. accumulating known volumetric strokes by the PD fluid pump; or Using an ideal gas law algorithm in determining the flow rate of the PD fluid pumped during the patient drain.

23. The control unit of claim 22, configured to:

25. the PD fluid pump is a peristaltic pump, a piston pump, or a pressure chamber pump, the pressure sensor is associated with the patient line, and the control unit an output from a flow meter associated with the patient line; the accumulated known volume rotation by said peristaltic pump; the accumulated known volumetric strokes made by said piston pump, or Output from a scale for the pressure chamber pump 23. The control unit of claim 22, configured to determine the flow rate of the PD fluid pumped during the patient drain based on one or more of:

26. Assuming that the pressure drop is expressed as a positive value, the allowable patient pressure P ａｃ By subtracting the pressure drop from P ｃ 設定点 =P ａｃ -ΔP チューブ 23. The control unit of claim 22, configured to determine the applied negative pressure, Pc setpoint, by (Q).

27. ​​A control unit as described in claim 22, configured to determine the pressure drop using an algorithm that takes into account the determined or known flow rate, at least one characteristic of the patient line, and at least one characteristic of the PD fluid.

28. The control unit of claim 22, configured to determine the pressure drop using a lookup table correlating pressure drop with PD fluid flow rate.

29. The method of claim 29, wherein the control unit is configured to determine the applied negative pressure by taking into account a head height differential between the patient's peritoneal cavity and the PD fluid pump, Re-accounting for a head height differential between the patient's peritoneal cavity and the PD fluid pump when (i) a threshold unintended PD fluid pressure change is detected or (ii) a threshold unintended PD fluid flow rate occurs.

23. The control unit of claim 22, configured to:

30. A control unit as described in claim 29, configured to determine the head height difference between the patient's peritoneal cavity and the PD fluid pump by slowing or stopping the PD fluid pump at least once and reading the resulting output from the pressure sensor.

31. A control unit as described in claim 22, configured to use the sensed negative pressure from the pressure sensor as feedback in a pressure control routine to cause the PD fluid pump to pump the PD fluid at the applied negative pressure during patient discharge.

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