Dialysis system with enhanced valve features

Abstract

A medical fluid system includes a medical fluid pump configured to pump a medical fluid; a tube through which the medical fluid pumped by the medical fluid pump flows; a pinch valve positioned and arranged to block the tube to prevent medical fluid from flowing through the tube, the pinch valve comprising a motor; a current sensor positioned and arranged to sense a current consumed by a motor of the pinch valve; and a control unit operable with the current sensor to monitor a current consumed by the motor when the motor is causing the pinch valve to block the tube, the control unit configured to stop the motor when the monitored current indicates a blockage of the tube.

Description

Technical Field

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

[0002] For 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] Dialysis is used to treat reduced kidney function and particularly kidney failure. Dialysis removes waste products, toxins and excess water from the body that would otherwise be removed by normally functioning kidneys. 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 the course of HF treatment, providing a convective transport mechanism that is particularly beneficial in removing medium and large molecules.

[0006] Hemodiafiltration ("HDF") is a treatment modality that combines convective and diffusive clearance. HDF uses 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 occur at centers. Today there is a trend toward home hemodialysis ("HHD"), in part because HHD can be performed daily, thereby providing treatment benefits superior to hemodialysis treatments in centers that are typically 2 or 3 weeks in duration. Studies have shown that more frequent treatments remove more toxins and wastes, and cause less fluid overload between dialysis sessions, compared to patients receiving less frequent but potentially longer treatments. Patients receiving more frequent treatments do not experience as many down cycles (fluid and toxin swings) as patients in centers that have accumulated toxins for two or three days before treatment. In some areas, the nearest dialysis center may be miles from the patient's home, resulting in door-to-door treatment time consuming most of the day. Treatment in a center near the patient's home may also consume most of the patient's day. HHD can occur during the night or day when the patient is relaxing, working or otherwise productive.

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

[0009] There are 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 port to allow used or spent dialysis fluid to drain from the peritoneal chamber. The patient then switches the fluid connection so that the patient's catheter is connected to a bag of fresh dialysis fluid to 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 chamber, 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 a drain, fill, and dwell cycle. However, an APD machine typically performs the cycle automatically while the patient sleeps. An APD machine relieves the patient from having to manually perform treatment cycles and from having to transport supplies during the day. The APD machine is fluidly connected to an implanted catheter, a source or bag of fresh dialysis fluid, and a fluid drain. The APD machine pumps fresh dialysis fluid from a dialysis fluid source through the catheter and into the patient's peritoneal chamber. The APD machine also allows the dialysis fluid to dwell within the chamber and allows for the transfer of waste, toxins, and excess water. The source can include multiple liters of dialysis fluid, which includes several bags of solution.

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

[0012] Each of the above dialysis modes, except CAPD (which does not typically involve a machine), uses an automatic valve to control whether dialysis fluid, blood, or other fluids can flow. The valve also controls the direction of fluid flow, such as the location where the fluid is coming from or the destination to which the fluid is flowing. Different types of valves are used in dialysis systems. One type of valve is typically used with a disposable cassette having a hard plastic component and a valve seat that defines a fluid flow path and one or more flexible membranes covering one or more sides of the hard plastic component. The disposable cassette is typically loaded into a dialysis machine or circulation machine that is capable of closing a specified portion of one or more plastic sheets against the valve seat to block fluid flow and forcing or allowing the plastic to move away from the valve seat to allow fluid flow.

[0013] Another type of automatic valve is a pinch valve, which alternatively pinches closed a tube carrying dialysis fluid, blood or other fluid to block fluid flow. There are two common types of pinch valves, solenoid pinch valves and electric pinch valves. Electric pinch valves need to be configured for specific tubing diameters and specific tubing wall thicknesses. Tubing diameters and wall thicknesses are not always consistent for different sets of tubing, and tubing wall thicknesses may further vary over time due to wear and tear through repeated clamping.

[0014] Therefore, there is a need for an improved way to operate an electric pinch valve. Summary of the invention

[0015] The present disclosure describes an electric valve for a medical fluid system, such as an automated peritoneal dialysis ("PD") system, which improves the usability of the valve. Although the present system is primarily described in conjunction with PD, the improved electric valve operation of the present disclosure is applicable to machines used in any of the dialysis modes described herein, such as online HD, HF, HDF and acute HD, HF, HDF. The improved electric valve operation of the present disclosure is also applicable to any medical fluid system in which the flow of therapeutic fluid or patient fluid is controlled via one or more valves.

[0016] In the PD example, the system includes a PD machine or a circulator. The PD machine is primarily described herein as having a pneumatically driven PD fluid pump and an electromechanically actuated electric pinch valve of the present disclosure. However, alternatively, the PD fluid pump may also be electromechanically driven, such as a piston, gear, peristaltic pump, or centrifugal pump. In one embodiment, the PD machine or circulator is capable of delivering fresh, heated PD fluid to a patient at a pressure of, for example, 14 kPa (2.0 psig) or more. The PD machine is capable of removing used PD fluid or effluent from a patient at a negative pressure of, for example, -9 kPa (-1.3 psig) or even greater. The fresh PD fluid delivered to the patient may first be heated to body fluid temperature, for example, 37°C.

[0017] The PD machine or cycler of the present system operates with the electric pinch valve under the control of the control unit. The control unit may include one or more current sensors that operate with the processor and / or memory of the control unit. A dedicated current sensor may be provided for each electric pinch valve, allowing each valve to be actuated completely independently. Alternatively, one or more current sensors may be provided for multiple electric pinch valves, for example, in the case where the timing of the activation of the actuation of multiple pinch valves is ensured not to overlap. The current sensor may be provided on a control board of the control unit, or alternatively located in the pinch valve, which may include a rotating nut motor under the control of the control unit. The rotating nut motor may be a stepper motor. The rotating nut located in the rotating nut motor is fixed in translation so that its rotation causes the threaded shaft to pass through the rotating nut so as to translate in an accurate manner in both the direction of valve closing and valve opening. The end of the threaded shaft that contacts the tube includes a rounded head or a wedge that allows the tube or pipeline to be blocked without damaging the pipeline. The pinch valve also includes a stopper against which the rounded head or wedge compresses the tube.

[0018] The spin nut motor rotates the spin nut in a first direction (e.g., clockwise) to translate the threaded shaft and the rounded head in the first direction toward the stopper to block the tube. The spin nut motor rotates the spin nut in a second direction (e.g., counterclockwise) to translate the threaded shaft and the rounded head in the second direction away from the stopper to allow medical fluid to flow through the tube.

[0019] For example, when the shaft is moved a set distance expected to completely block the tube, the prior art control of the electric pinch valve may be defective and fail to achieve complete blockage of the tube because the tube wall thickness at the contact point becomes thinner due to repeated blockage. Corresponding fluid leakage occurs. Moreover, if the diameter and / or tube wall thickness of the tube is different from the diameter and / or tube wall thickness of the tube expected for the set translation distance, leakage may occur even if the tube wall thickness has not been worn or thinned.

[0020] The present method solves the above-mentioned problem by monitoring the output of the corresponding current sensor of the electric valve during the tube blockage. The control unit of the machine or circulator determines whether the output from the current sensor shows a spike signal or a characteristic change, which indicates that the tube has been completely blocked and the threaded shaft and the round head are pushed against the stopper, which forces the rotating nut motor to enter a stall state. That is, the rotating nut motor will consume more current in the fully blocked state at the end of the stroke in an attempt to keep the rotating nut rotating. The additional current consumption is detected by the current sensor. If the output from the current sensor does not show a spike signal or a characteristic change indicating that the tube is completely blocked, the control unit continues to monitor the current sensor and rotates the rotating nut motor, thereby further translating the threaded shaft and the round head. If the output from the current sensor does show a spike signal or a characteristic change indicating that the tube is completely blocked, the control unit de-energizes the rotating nut motor.

[0021] In accordance with the disclosure set forth herein and without limiting the present disclosure in any way, in a first aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a medical fluid system comprises: a medical fluid pump configured to pump a medical fluid; a tube through which the medical fluid pumped by the medical fluid pump flows; a pinch valve positioned and arranged to block the tube to prevent the medical fluid from flowing through the tube, the pinch valve comprising a motor; a current sensor positioned and arranged to sense current consumed by the motor of the pinch valve; and a control unit capable of operating in conjunction with the current sensor to monitor the current consumed by the motor while the motor is causing the pinch valve to block the tube, the control unit being configured to stop the motor when the monitored current indicates blockage of the tube.

[0022] In a second aspect of the disclosure which may be combined with any other aspect or a portion thereof, the monitored current increases to indicate blockage of the tube.

[0023] In a third aspect of the present disclosure which may be combined with any other aspect or part thereof, a current sensor is provided with the control unit or the pinch valve.

[0024] In a fourth aspect of the disclosure which may be combined with any other aspect or a portion thereof, a current sensor is configured to sense current consumed by a plurality of motors of a plurality of pinch valves.

[0025] In a fifth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, a pinch valve comprises a shaft driven by a motor.

[0026] In a sixth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the motor is a rotary nut motor and the shaft is a threaded shaft.

[0027] In a seventh aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the shaft includes a head contacting the tube, and the valve further includes a stopper against which the head abuts to block the tube.

[0028] In an eighth aspect of the present disclosure, which may be combined with any other aspect or a portion thereof, the tube is a first tube and the pinch valve is a first pinch valve, and wherein the control unit is operable with the current sensor or the second current sensor to monitor the current consumed by the second motor of the second pinch valve while the second motor is causing the second pinch valve to block the second tube, and the control unit is further configured to stop the second motor when the monitored current indicates that the second tube is blocked.

[0029] In a ninth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the control unit is further configured to operate the motor in a reverse direction without monitoring the current consumed by the motor to allow the medical fluid to flow through the tube.

[0030] In a tenth aspect of the present disclosure, which may be combined with any other aspect or a portion thereof, the tube is disposable or reusable.

[0031] In an eleventh aspect of the present disclosure which may be combined with any other aspect or portion thereof, the control unit is configured to wait temporarily after the monitored current initially indicates blockage of the tube before stopping the motor.

[0032] In a twelfth aspect of the present disclosure, which may be combined with any other aspect or a portion thereof, a medical fluid system comprises: a medical fluid pump configured to pump a medical fluid; a tube through which the medical fluid pumped by the medical fluid pump flows; a pinch valve positioned and arranged to block the tube to prevent the medical fluid from flowing through the tube, the pinch valve comprising a motor; a sensor positioned and arranged to sense a characteristic change associated with the motor of the pinch valve when the tube is blocked; and a control unit operable with the sensor, the control unit being configured to stop the motor when a characteristic change is sensed.

[0033] In a thirteenth aspect of the present disclosure which may be combined with any other aspect or portion thereof, the sensor is a current sensor, a resistance sensor, a Hall effect sensor, or a current transformer.

[0034] In a fourteenth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the characteristic change is a characteristic increase in current consumed by the motor.

[0035] In a fifteenth aspect of the present disclosure which may be combined with any other aspect or a portion thereof, the control unit is configured to temporarily wait after sensing the characteristic change before stopping the motor.

[0036] In a sixteenth aspect of the present disclosure, which may be combined with any other aspect or a portion thereof, a method for controlling an electric pinch valve for the flow of a medical fluid comprises: (i) powering a motor of the electric pinch valve so that an axis of the electric pinch valve moves in a tube blockage direction; (ii) monitoring a sensor output indicating current consumed by the motor while the motor is powered; (iii) returning to (i) if no change in the sensor output characteristic of tube blockage is detected; and (iv) de-energizing the motor if a change in the sensor output characteristic of tube blockage is detected.

[0037] In a seventeenth aspect of the present disclosure which may be combined with any other aspect or portion thereof, the sensor is a current sensor.

[0038] In an eighteenth aspect of the present disclosure which may be combined with any other aspect or portion thereof, the output characteristic of the blockage of the tube comprises an increase in current consumed by the motor.

[0039] In a nineteenth aspect of the disclosure which may be combined with any other aspect or portion thereof, wherein in (iv), a change in the output characteristic of the sensor that detects blockage of the tube is detected for a period of time sufficient to ensure that the change is due to blockage of the tube and not some other abnormality.

[0040] In a twentieth aspect of the present disclosure which may be combined with any other aspect or portion thereof, a change in a sensor output characteristic that detects blockage of a tube is detected regardless of tube wear, tube flexibility, or tube manufacturing tolerances.

[0041] In a twenty-first aspect of the present disclosure, which may be combined with any other aspect or part thereof, Figures 1 to 6D Any features, functions and alternatives described in any one or more of the figures may be combined with Figures 1 to 6D Any features, functions and alternatives described in any other figure in the figure can be combined.

[0042]

[0013] According to the above aspects and the present disclosure set forth herein, an advantage of the present disclosure is to provide a medical fluid system with improved electric pinch valve operation.

[0043] Another advantage of the present disclosure is to provide a medical fluid system with improved electric pinch valve flexibility, wherein the valve can operate with multiple different diameters / wall thicknesses of tubing and can compensate for tubing wall thickness variations.

[0044] Another advantage of the present disclosure is to provide a medical fluid system having a simplified electric pinch valve.

[0045] Furthermore, an advantage of the present disclosure is to provide a medical fluid system having a compact electric pinch valve.

[0046] Yet another advantage of the present disclosure is to provide a medical fluid system having an effective leak-proof tubing clamping despite tubing thickness variations and wear due to repeated clamping.

[0047] Additional features and advantages are described in and will be apparent from the following detailed description and accompanying drawings. The features and advantages described herein are not all-inclusive, and in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the accompanying drawings and description. Moreover, it is not necessary for any particular embodiment to have all of the advantages listed herein, and it is expressly contemplated that each advantageous embodiment is individually claimed. Furthermore, it should be noted that the language used in this specification is selected primarily for readability and instructional purposes, and does not limit the scope of the subject matter of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a cross-sectional schematic diagram of one embodiment of an APD system having electric pinch valve operation of the present disclosure.

[0049] Figure 2A and Figure 2B 1 and 2 are respectively a top view and a side view of an embodiment of an electric pinch valve of the present disclosure.

[0050] Figure 3 is a process flow diagram of a prior art method of plugging a flexible tube using an electric pinch valve.

[0051] Figure 4A and Figure 4B is a schematic diagram illustrating problems with the operation of a related art electric pinch valve.

[0052] Figure 5 is a process flow diagram of the disclosed structure and method for plugging a flexible tube using an electric pinch valve.

[0053] FIG. 6A to FIG. 6D is a schematic elevation view showing the disclosed structure and method for plugging a flexible tube using an electric pinch valve. DETAILED DESCRIPTION

[0054] Referring now to the drawings and in particular to Figure 1 , an example system 10 including the electric pinch valve operation of the present disclosure is shown. The system 10 includes a dialysis machine 20 (such as an automated peritoneal dialysis ("PD") machine) operating a medical fluid handling device 70 (such as a dialysis fluid cassette). Although the present system 10 is primarily described in conjunction with PD, the improved electric valve operation of the present disclosure is applicable to machines used in any of the dialysis modes described herein, such as online HD, HF, HDF and acute HD, HF, HDF. The improved electric valve operation of the present disclosure is also applicable to any medical fluid system in which the flow of therapeutic fluid or patient fluid is controlled via one or more valves.

[0055] The PD machine 20 in the illustrated embodiment includes a housing 22 defining 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 pneumatic line 28 extending from a positive pneumatic source 30 to perform a pumping or draining stroke, for example, to (i) push fresh heated dialysis fluid to the peritoneal cavity 14 of the patient 12 via the patient line 16 and the patient delivery set 18, for example, at a pressure of 14 kPa (2.0 psig) or higher, (ii) push fresh dialysis fluid at a higher system pressure to a heating container (not shown) to be heated to body temperature, for example, 37° C., by a dialysis fluid heater (not shown), or (iii) push spent dialysis fluid at a higher system pressure to a drain. The pump actuation region 26 in the illustrated embodiment is pneumatically actuated via a negative pneumatic line 32 extending from a negative pneumatic source 34 to perform a pumping or aspiration stroke, for example, to (i) draw fresh dialysis fluid from a dialysis fluid source 40 through a supply line 42 at a higher system pressure, (ii) draw fresh heated dialysis fluid from a heating container (not shown) at a higher system pressure, or (iii) draw spent dialysis fluid from the peritoneal cavity 14 of the patient 12 via the patient line 16 and the transfer set 18 at, for example, -9 kPa (-1.3 psig) or potentially greater negative pressure.

[0056] The patient line 16 can be three to seven meters long, such as approximately 4.5 meters or 6.7 meters, with an inner diameter of, for example, two to four millimeters ("mm") and a wall thickness of approximately 1 mm. The supply line 42 may also have an inner diameter of, for example, 2 mm to 4 mm and a wall thickness of approximately 1 mm. The PD machine 20 also provides a pressure sensor 44 for measuring the positive pneumatic pressure in the positive pneumatic line 28 and a pressure sensor 46 for measuring the negative pneumatic pressure in the negative pneumatic line 32. The PD machine 20 also includes a plurality of electrically operated pneumatic valves, such as valves 48, 50, 52, and 56. The pneumatic valve 48 is positioned in the positive pneumatic line 28 to selectively allow positive pressure from the source 30 to reach the pump actuation area 26. The pneumatic valve 50 is positioned in the negative pneumatic line 32 to selectively allow negative pressure from the source 34 to reach the pump actuation area 26. An exhaust valve 52 is provided in a vent line 54 in communication with the positive pneumatic line 28 to selectively vent the positive pressure in the line 28 and the pump actuation area 26 to the atmosphere. A second exhaust valve 56 is provided in a vent line 58 in communication with the negative pneumatic line 32 to selectively vent the negative pressure in the line 32 and the pump actuation area 26 to the atmosphere. In an alternative embodiment, a single exhaust valve and line may be provided to vent both the positive and negative pressures from the pump actuation area 26 to the atmosphere.

[0057] Figure 1 The PD machine 20 is also shown to include a positive pneumatic pressure regulator 66 (e.g., a variable orifice valve) positioned along the positive pneumatic line 28 and a negative pressure regulator 68 (e.g., a variable orifice valve) positioned along the negative pneumatic line 32. The positive pneumatic pressure regulator 66 sets the positive pneumatic pressure delivered to the pump actuation area 26 to a desired and controlled level, which is also the pressure of the fresh or spent PD fluid pumped out of the dialysis fluid cassette 70. The negative pneumatic pressure regulator 68 sets the negative pneumatic pressure drawn at the pump actuation area 26 to a desired and controlled level, which is also the pressure of the fresh or spent PD fluid pumped into the dialysis fluid cassette 70. In an alternative embodiment, the PD machine 20 may be pneumatically configured such that a single pressure regulator (e.g., a variable orifice valve) operates as a positive pneumatic pressure regulator and a negative pneumatic pressure regulator at different times.

[0058] The pressure sensors 44 and 46, the pneumatic valves 48, 50, 52 and 56, and the variable orifice valves or regulators 66 and 68 are output to or controlled by the control unit 60 of the PD machine 20. The control unit 60 in the illustrated embodiment includes one or more processors 62a and one or more memories 62b. The control unit 60 may have any one or more of a main controller, a security controller, a video controller, and / or a sub- or delegated controller.

[0059] exist Figure 1In the illustrated embodiment of the medical fluid handling device or disposable cassette 70, a pump actuation chamber 72 is provided, which cooperates with the pump actuation area 26 to form an overall pumping chamber. The medical fluid handling device 70 in the illustrated embodiment includes a flexible membrane, diaphragm or sheet 74, which can be sized to fit the pump actuation chamber 72, or can be sized to cover the entire side of the medical fluid handling device 70 (as shown), wherein a portion of the membrane 74 covers the pump actuation chamber 72, and wherein the portion can be at least substantially flat or preformed into a dome shape or preformed to fit into one or both of the pump actuation area 26 and the pump actuation chamber 72. The control unit 60 causes negative pressure from the source 34 to be applied to the flexible membrane 74 to pull the sheet toward the wall of the pump actuation area 26, thereby correspondingly drawing fresh or spent PD fluid into the pump actuation chamber 72. To this end, the control unit causes valves 48, 52 and 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 pneumatic pressure applied at the pump actuation area 26 via the negative pressure regulator 68 .

[0060] The control unit 60 causes positive pressure from the source 30 to be applied to the flexible membrane 74 to push the sheet against the wall of the pump actuation chamber 72, thereby correspondingly pushing fresh or spent PD fluid from the pump actuation chamber 72. To this end, the control unit causes valves 50, 52, and 56 to be closed and valve 48 to be opened. During the 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 program to set the level of positive pneumatic pressure applied at the pump actuation area 26 via the positive pressure regulator 66.

[0061] The control unit 60 can determine the flow rate of fresh and spent PD fluid pumped by the PD machine 20 of the system 10 in at least one of a number of different ways. In one approach, the fixed volumes of the pump actuation area 26 and the pump actuation chamber 72 together 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 amount of time required to perform the number of full strokes delivered to determine the local or current PD fluid flow rate.

[0062] Alternatively or additionally, the control unit 60 takes pressure measurements before and after a fill or discharge stroke and uses an ideal gas law algorithm known in the art to determine the resulting volume of fresh or spent PD fluid drawn into or discharged from the pump actuation chamber 72. To this end, the PD machine 20 may provide positive and negative reference chambers (not shown) of known and fixed volume, which may be pneumatically connected to the positive vent line 54 and the negative vent line 58, respectively. The control unit 60 may then add the volumes of the successive fill or discharge strokes determined by the ideal gas law algorithm and divide the sum by the corresponding amount of time required to perform the 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 in that a full stroke of the diaphragm or sheet 74 through the pump actuation region 26 and the pump actuation chamber 72 is not required. Partial strokes may be performed and taken into account when determining the local or current flow rate.

[0063] It should be understood that the PD machine 20 may provide two pump actuation areas 26 and pump actuation chambers 72 that operate in an alternating manner (one fills while the other drains) so that the flow of fresh or used PD fluid is mostly continuous. Figure 1 A pneumatically driven pump actuation region 26 and pump actuation chamber 72 are shown, but the PD fluid pumping of system 10 may alternatively be electromechanically driven, such as via a piston, gear, peristaltic pump, or centrifugal pump.

[0064] In the illustrated embodiment, regardless of the type of pumping employed by the system 10, the PD machine 20 includes electromechanical electric pinch valves 80a, 80b under the control of the control unit 60. Figure 1 As shown, electric pinch valve 80a is operable with supply line 42, while electric pinch valve 80b is operable with patient line 16. Figure 1 Two electric pinch valves 80a, 80b are shown, but the PD machine 20 of the system 10 may include additional electric pinch valves, such as additional fluid valves for additional pump actuation chambers 72 (operated in an alternating manner to provide more continuous flow) and additional fluid valves for multiple supply lines 42, fluid heater lines, and / or exhaust lines, for simplicity. Figure 1 , they are not shown.

[0065] Figure 1It is shown that the control unit 60 may also include one or more current sensors 64a, 64b, which work together with one or more processors 62a and / or one or more memories 62b. A dedicated current sensor 64a, 64b may be provided for each electric pinch valve 80a, 80b, allowing each valve to be actuated completely independently. Alternatively, one or more current sensors 64a, 64b may be provided for multiple electric pinch valves 80a, 80b, for example, where the timing of the start of the actuation of the pinch valves 80a, 80b is ensured to not overlap. Although the current sensors 64a, 64b are shown as being arranged together with the control unit 60, for example, arranged on a control board of the control unit 60, the current sensors 64a, 64b may alternatively be located in the pinch valves 80a, 80b, respectively.

[0066] Figure 2A and Figure 2B The electric pinch valves 80a, 80b are shown in more detail. In the illustrated embodiment, the electric pinch valves 80a, 80b each include a rotary nut motor 82 under the control of the control unit 60. The rotary nut motor 82 may be a stepper motor. The rotary nut located within the rotary nut motor 82 is fixed in translation so that its rotation causes a threaded shaft 84 threadedly passing through the rotary nut to translate in an accurate manner in both the valve closing direction and the valve opening direction. The contact tube (e.g., Figure 1 The end of the threaded shaft 84 of the patient line 16 or supply line 42 in the tubing is provided with a rounded head or wedge 86 which allows the tube or line 16, 42 to be blocked without damaging the line or tube. Figure 2A and Figure 2B The pinch valve 80a, 80b in the embodiment also includes a stopper 88, against which the rounded head or wedge 86 compresses the tube or line 16, 42. The rotating nut motor 82 rotates the rotating nut in a first direction (e.g., clockwise) to translate the threaded shaft 84 and the rounded head 86 toward the stopper 88 in the first direction, thereby blocking the tube or line 16, 42. The rotating nut motor 82 rotates the rotating nut in a second direction (e.g., counterclockwise) to translate the threaded shaft 84 and the rounded head 86 in the second direction away from the stopper 88, thereby allowing medical fluid to flow through the tube or line 16, 42.

[0067] Figure 3A prior art method 100 for plugging a flexible tube using an electric pinch valve is shown. At ellipse 102, the method 100 begins. At box 104, a rotary nut motor (such as a stepper motor) moves in a commanded number of steps, which is calculated in conjunction with the geometry of the threaded shaft to produce the amount of translational movement of the threaded shaft and circular head required to plug the pipe or pipeline. When the commanded number of motor steps has moved, the motor stops, as shown in box 106. At ellipse 108, the method 100 ends. Figure 4A and Figure 4B The problem of using method 100 is shown. When the contacting portions of the pipes or pipelines 16, 42 have Figure 4A When the threaded shaft and the rounded head are at their intended thickness as shown, translating the threaded shaft and the rounded head a calculated fixed distance (to the dashed line) results in the tube or pipeline 16, 42 being properly blocked. However, when the contacting portion of the tube or pipeline 16, 42 has become thinner, for example, due to repeated clamping or blocking, or due to manufacturing tolerances in manufacturing the tube wall, and is therefore thinner than specified or expected, as shown in FIG. Figure 4B As shown, translating the threaded shaft and circular head a calculated fixed distance (to the dashed line) does not result in the tube or line 16, 42 being properly plugged and thereby causing a leak.

[0068] Figure 5 A method 110 of the present disclosure for plugging a flexible tube 16, 42 using an electric pinch valve 80a, 80b is shown. At oval 112, the method 110 begins. At box 114, the control unit 60 rotates the rotary nut motor 82 and begins translating the threaded shaft 84 and the circular head 86 toward the stop 88. At box 114, the control unit 60 also begins monitoring the output of the current sensors 64a, 66b associated with the pinch valves 80a, 80b. As discussed above, any current sensor 64a, 64b may be associated with one or more electric pinch valves 80a, 80b.

[0069] At diamond 116, the control unit 60 determines whether the output from the current sensors 64a, 64b shows a spike or characteristic change indicating that the tube or pipeline 16, 42 has been completely blocked and the threaded shaft 84 and the round head 86 are pushing against the stop 88, which forces the rotary nut motor 82 to enter a stall state. That is, the rotary nut motor 82 will consume more current in the end-of-stroke, fully blocked state in an attempt to keep its rotary nut rotating. The additional current consumption is detected by the current sensors 64a, 64b. If the output from the current sensors 64a, 64b at diamond 116 does not show a spike or characteristic change indicating that the tube or pipeline 16, 42 has been completely blocked, the method 110 returns to box 114, where the control unit 60 continues to monitor the current sensors 64a, 64b and rotate the rotary nut motor 82, thereby translating the threaded shaft 84 and the round head 86 toward the stop 88. If at diamond 116 the output from current sensor 64a, 64b does show a spike or characteristic change indicating that tube or line 16, 42 is completely blocked, method 110 moves to box 118 where control unit 60 stops spin nut motor 82. At oval 120, method 110 ends.

[0070] FIG. 6A to FIG. 6D The method 110 is shown in more detail via the sequence of electric pinch valves 80a, 80b during occlusion. Fig. 6A In the embodiment of the present invention, the control unit 60 causes the rotary nut motor 82 to be powered and causes the threaded shaft 84 and the circular head 86 to begin translating. The corresponding outputs from the current sensors 64a, 64b as shown on the display 90 indicate that the rotary nut motor 82 initially consumes a typical or expected amount of current during the onset of a jam. Figure 6B , the control unit 60 continues to cause the spin nut motor 82 to be energized and the threaded shaft 84 and rounded head 86 to continue to translate so as to contact and begin to compress the tube or line 16, 42. As indicated by the corresponding outputs from the current sensors 64a, 64b shown on the display 90, the spin nut motor 82 continues to draw a normal or expected amount of current during the initial tube contact portion of the occlusion.

[0071] exist Figure 6C , the control unit 60 continues to cause the spin nut motor 82 to be powered and the threaded shaft 84 and rounded head 86 to continue occluding the tube or pipeline 16, 42. As indicated by the corresponding output from the current sensors 64a, 64b shown on the display 90, the spin nut motor 82 continues to draw the usual or expected amount of current during the further tube contacting portion of the occlusion. Fig.6D, the control unit 60 attempts to continue rotating the rotary nut motor 82 and continue translating the threaded shaft 84 and the circular head 86 in order to continue blocking the tube or pipeline 16, 42. However, because the tube or pipeline 16, 42 is completely compressed between the circular head 86 and the stop 88, the rotary nut can no longer rotate. The rotary nut motor 82 enters a stalled state and consumes more current in an attempt to keep the rotary nut rotating. The additional current consumption is detected by the corresponding outputs from the current sensors 64a, 64b as shown on the display 90, indicating that the threaded shaft 84 and the circular head 86 have completely blocked the tube or pipeline 16, 42, such that the head 86 is now pressed against the stop 88. The control unit 60 quickly senses the increase in current spike signal or characteristic and cuts off power to the rotary nut motor 82. Fig.6D In one embodiment, the control unit 60 is programmed to wait for a period of time, such as about one second, to ensure that the current spike signal or characteristic increase is due to the blockage of the main pipe or pipeline 16, 42, rather than some other current spike signal abnormality. That is, the control unit 60 can cause the rotary nut motor 82 to continue to push against the pipe or pipeline 16, 42, for example, about one second after the current spike signal or characteristic increase is first observed. Small current spikes that do not indicate complete blockage will usually occur due to noise. However, after observing the characteristic increase for, for example, about one second, the control unit 60 safely determines that the pipe or pipeline 16, 42 is completely blocked. However, it should be understood that care should be taken to ensure that the motor 82 is not powered long enough to cause it to become heated.

[0072] In one embodiment, the control unit 60 does not monitor the output from the current sensors 64a, 64b when rotating the rotary nut motor 82 in the opposite tube opening direction. Here, the control unit 60 can be programmed to run the rotary nut motor 82 in the opposite direction for a determined number of stepper motor steps, or until a limit switch is triggered (e.g., to allow the use of a less expensive non-stepper motor), wherein the top end of the circular head 86 is known to disengage from the tube or line 16, 42 so that the tube can be fully opened to allow medical fluid (e.g., PD fluid) to flow therethrough.

[0073] Figure 5 and FIG. 6A to FIG. 6D The structure and corresponding method of the electric pinch valve 80a, 80b of the present disclosure successfully plugs the tube or pipeline 16, 42 regardless of the tube (the tube 16, 42 must be initially installed in Fig. 6ASuccessful plugging of the tube or line 16, 42 also occurs regardless of manufacturing tolerances, regardless of the diameter of the tube or line 16, 42 (in the space between the rounded head 86 and the stop 88 in the plug), and regardless of whether the wall thickness of the tube 16, 42 changes over time due to repeated plugging, or whether the tube 16, 42 becomes softer during repeated plugging, in which case the tube 16, 42 needs to be compressed more to form a good seal.

[0074] It should be understood that various changes and modifications to the currently preferred embodiments described herein will be apparent to those skilled in the art. Therefore, these changes and modifications are intended to be covered by the appended claims. For example, although system 10 is shown as operating with disposable cartridges 70, system 10 may alternatively use durable or reusable components that are, for example, sterilized, such as heat sterilized after use. Here, flexible lines or tubes 16, 42 may alternatively be disposed in a PD machine or circulation machine 20, wherein the lines are sterilized after treatment. Moreover, although sensors 64a, 64b are described as current sensors, other types of sensors may be used, such as resistive sensors, Hall effect sensors, and current transformers.

Claims

1. A medical fluid system, comprising: a medical fluid pump configured to pump a medical fluid; a tube through which the medical fluid pumped by the medical fluid pump flows; a pinch valve positioned and arranged to occlude the tube to prevent the flow of medical fluid through the tube, the pinch valve including a motor; a current sensor positioned and arranged to sense current consumed by a motor of the pinch valve; as well as A control unit is operable with the current sensor to monitor current consumed by the motor while the motor is causing the pinch valve to occlude the tube, the control unit being configured to stop the motor when the monitored current indicates occlusion of the tube.

2. The medical fluid system of claim 1, wherein: An increase in the monitored current indicates blockage of the tube.

3. The medical fluid system of claim 1, wherein: The current sensor is provided together with the control unit or the pinch valve.

4. The medical fluid system of claim 1, wherein: The current sensor is configured to sense current consumed by a plurality of motors of a plurality of pinch valves.

5. The medical fluid system of claim 1, wherein: The pinch valve includes a shaft driven by the motor.

6. The medical fluid system of claim 5, wherein: The motor is a rotary nut motor and the shaft is a threaded shaft.

7. The medical fluid system of claim 5, wherein: The shaft includes a head that contacts the tube, and the valve further includes a stopper against which the head blocks the tube.

8. The medical fluid system of claim 1, wherein: The tube is a first tube and the pinch valve is a first pinch valve, and wherein the control unit is operable with the current sensor or the second current sensor to monitor the current consumed by the second motor of the second pinch valve while the second motor is causing the second pinch valve to block the second tube, and the control unit is further configured to stop the second motor when the monitored current indicates blockage of the second tube.

9. The medical fluid system of claim 1, wherein: The control unit is also configured to operate the motor in a reverse direction without monitoring the current consumed by the motor to allow medical fluid to flow through the tube.

10. The medical fluid system of claim 1, wherein: The tube may be disposable or reusable.

11. The medical fluid system of claim 1, wherein: The control unit is configured to wait momentarily after the monitored current initially indicates blockage of the tube before stopping the motor.

12. A medical fluid system, comprising: a medical fluid pump configured to pump a medical fluid; a tube through which the medical fluid pumped by the medical fluid pump flows; a pinch valve positioned and arranged to occlude the tube to prevent the flow of medical fluid through the tube, the pinch valve including a motor; a sensor positioned and arranged to sense a change in a characteristic associated with a motor of the pinch valve when the tube is blocked; as well as A control unit is operable with the sensor, the control unit being configured to stop the motor when the characteristic change is sensed.

13. The medical fluid system of claim 12, wherein: The sensor is a current sensor, a resistance sensor, a Hall effect sensor or a current transformer.

14. The medical fluid system of claim 12, wherein: The characteristic change is a characteristic increase in the current consumed by the motor.

15. The medical fluid system of claim 12, wherein: The control unit is configured to wait temporarily after sensing the characteristic change before stopping the motor.

16. A method for controlling an electric pinch valve for a flow of a medical fluid, comprising: (i) supplying power to the motor of the electric pinch valve so that the shaft of the electric pinch valve moves in the tube blocking direction; (ii) while powering the motor, monitoring a sensor output indicative of current consumed by the motor; (iii) if no change in the sensor output characteristic indicating blockage of the tube is detected, return to (i); as well as (iv) if a change in the sensor output characteristic indicating blockage of the tube is detected, the motor is de-energized.

17. The method according to claim 16, wherein: The sensor is a current sensor.

18. The method according to claim 16, wherein: The output characteristic of the blockage of the tube includes an increase in the current consumed by the motor.

19. The method according to claim 16, wherein: In (iv), the change in the sensor output characteristic of the clogging of the tube is detected for a period of time sufficient to ensure that the change in the sensor output characteristic of the clogging of the tube is due to the clogging of the tube and not some other abnormality.

20. The method according to claim 16, wherein: A change in the sensor output characteristic that detects blockage of the tube regardless of tube wear, tube flexibility, or tube manufacturing tolerances.

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