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, and a pinch valve positioned and arranged to block the tube to prevent the medical fluid from flowing through the tube. The pinch valve includes a motor, a current sensor positioned and arranged to sense a current drawn by the motor of the pinch valve, and a control unit operable with the current sensor to monitor the current drawn by the motor while the motor closes the tube with the pinch valve. The control unit is configured to stop the motor when the monitored current indicates occlusion of the tube.

Description

Technical Field

[0001] The present disclosure generally relates to medical fluid therapy, and more particularly to dialysate therapy that requires fluid heating.

Background Art

[0002] For various reasons, a person's renal system may fail to function. Renal insufficiency causes several physiological disorders. It becomes impossible to balance water and minerals or excrete the daily metabolic load. Toxic end products of metabolism such as urea, creatinine, uric acid, and others can accumulate in the patient's blood and tissues.

[0003] Reduced kidney function, especially renal insufficiency, is treated by dialysis. Dialysis removes waste products, toxins, and excess water from the body that a normally functioning kidney would normally remove. Dialysis treatment for kidney function replacement is extremely important for many people because this treatment is life-saving.

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

[0005] Hemofiltration ("HF") is another kidney replacement therapy that relies on the convective transport of toxins from a patient's blood. HF is achieved by adding a replacement fluid or substitution fluid to the extracorporeal circuit during treatment. The replacement fluid, and the body fluids accumulated by the patient between treatments, are ultrafiltered over the course of the HF treatment, providing a convective transport mechanism that is particularly beneficial in removing medium and large molecules.

[0006] Hemodiafiltration ("HDF") is a treatment method that combines convective clearance and diffusive clearance. HDF provides diffusive clearance using dialysis fluid flowing through a dialyzer, similar to standard hemodialysis. Additionally, a replacement solution is provided directly into the extracorporeal circuit to provide convective clearance.

[0007] Most HD, HF, and HDF treatments are performed in a facility. Currently, there is a trend towards home hemodialysis ("HHD"), in part because HHD can be performed daily and typically offers therapeutic benefits superior to in-facility hemodialysis treatments that are typically performed two or three times a week. Studies have shown that more frequent treatments remove more toxins and waste products and result in less interdialytic fluid overload than less frequent but perhaps longer treatments received by patients. Patients receiving more frequent treatments do not experience the same degree of downcycle (fluctuations in fluid and toxins) as in-facility patients who accumulate two or three days' worth of toxins prior to treatment. In certain areas, the nearest dialysis facility may be miles from the patient's home, causing door-to-door treatment time to consume most of the day. Treatments at a facility close to the patient's home can also consume most of the patient's day. HHD can be performed at night or during the day when the patient is relaxed, working, or otherwise productive.

[0008] Another type of kidney failure treatment is peritoneal dialysis ("PD"), in which a dialysis solution, also called dialysate, is injected into the patient's peritoneal cavity via a catheter. The dialysate comes into contact with the peritoneum within the patient's peritoneal cavity. Wastes, toxins, and excess water enter the dialysate from the patient's bloodstream through the peritoneal capillaries by diffusion and osmosis. That is, an osmotic pressure gradient is generated across the membrane. Osmotic agents in the PD dialysate provide the osmotic pressure gradient. Used or spent dialysate is drained from the patient, removing wastes, toxins, and excess water from the patient. This cycle is repeated multiple times, for example.

[0009] There are various types of peritoneal dialysis therapies, which include 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 the drain to enable the used or spent dialysis fluid to be drained from the peritoneal cavity. The patient then switches the fluid communication so that the patient catheter communicates with a bag of fresh dialysis fluid and fresh dialysis fluid is infused into the patient through the catheter. The patient disconnects the catheter from the bag of fresh dialysis fluid and allows the dialysis fluid to remain in the peritoneal cavity so that the transfer of waste products, toxins and excess water takes place. 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 the patient's time and effort and leaves room for great improvement.

[0010] Automated peritoneal dialysis ("APD") is similar to CAPD in that the dialysis treatment involves cycles of drain, fill and dwell. However, APD devices typically perform these cycles automatically while the patient is sleeping. The APD device liberates the patient from having to perform the treatment cycles manually and having to transport supplies during the day. The APD device is fluidly connected to an implanted catheter, a source or bag of fresh dialysis fluid, and a fluid drain. The APD device pumps fresh dialysis fluid through the catheter into the patient's peritoneal cavity from the dialysis fluid source. The APD device also enables the dialysis fluid to dwell in the cavity and the transfer of waste products, toxins and excess water to take place. The source may contain several liters of dialysis fluid in multiple solution bags.

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

[0012] Except for CAPD (which typically does not involve machinery), each of the dialysis methods identified above uses automated valves to control whether dialysate, blood, or other fluids can flow or not. The valves also control the direction of fluid flow, such as where the fluid comes from or where it flows to. Different types of valves are used in dialysis systems. One type of valve is typically used with a disposable cassette, which has a rigid plastic component that defines a fluid flow path and a valve seat, and one or more flexible membranes that cover one or more surfaces of the rigid plastic component. The disposable cassette is typically loaded into a dialysis machine or cycler, which can close a designated portion of one or more plastic sheets against the valve seat to block fluid flow and move or be able to move the plastic away from the valve seat to allow fluid flow.

[0013] Another type of automated valve is a pinch valve, which instead closes by pinching the tube carrying the dialysate, blood, or other fluid to block fluid flow. Generally, there are two types of pinch valves, solenoid pinch valves and electric pinch valves. Electric pinch valves need to be configured for a specific tube diameter and a specific tube wall thickness. The tube diameter and wall thickness are not always consistent for different tube sets, and the tube wall thickness can further change over time due to wear and tear from repeated clamping.

[0014] Therefore, an improved method for operating an electric pinch valve is needed. Summary of the Invention Means for Solving the Problems

[0015] The present disclosure describes an electric valve for a medical fluid system, such as an automated peritoneal dialysis ("PD") system, that improves the usefulness of the valve. Although the system is mainly described in relation to PD, the improved electric valve operation of the present disclosure is applicable to devices used in any dialysis method 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 treatment fluid, or the flow of patient fluid, is controlled by one or more valves.

[0016] In an example of PD, the system includes a PD device or cycler. The PD device is described herein as mainly having a pneumatically driven PD fluid pump and an electromechanically actuated electric pinch valve of the present disclosure. However, alternatively, the PD fluid pump can also be electromechanically driven and can be, for example, a piston, gear, peristaltic or centrifugal pump. The PD device or cycler can, in one embodiment, deliver fresh heated PD fluid to the patient, for example, at 14 kPa (2.0 psig) or above. The PD device can remove used PD fluid or effluent from the patient, for example, at a negative pressure of -9 kPa (-1.3 psig) or more. The fresh PD fluid delivered to the patient can first be heated to body fluid temperature, for example, 37°C.

[0017] The PD device or cycler of this system operates together with an electric pinch valve under the control of a control unit. The control unit may include one or more current sensors that operate together with the processor and / or memory of the control unit. A dedicated current sensor may be provided for each electric pinch valve, enabling fully independent operation of each valve. Alternatively, for example, if it is guaranteed that the start timings of the operations of multiple pinch valves do not overlap, one or more current sensors may be provided for multiple electric pinch valves. The current sensor may be provided on the control board of the control unit or, alternatively, may be arranged within the pinch valve, which may include a rotary nut motor under the control of the control unit. The rotary nut motor may be a stepper motor. The rotary nut arranged within the rotary nut motor is translationally fixed such that its rotation causes the threaded shaft passing through the rotary nut to be accurately translated in both the valve closing direction and the valve opening direction. The end of the threaded shaft that contacts the tube includes a rounded head or wedge that enables the tube or line to be blocked without damaging the tube. The pinch valve also includes a stop where the rounded head or wedge compresses the tube.

[0018] The rotary nut motor rotates the rotary nut in a first direction, for example clockwise, translating the threaded shaft and the rounded head in the first direction towards the stop to block the tube. The rotary nut motor rotates the rotary nut in a second direction, for example counterclockwise, translating the threaded shaft and the rounded head in the second direction away from the stop to enable the medical fluid to flow through the tube.

[0019] The control of the prior art of the electric pinch valve can be insufficient when the shaft has moved the expected set distance to completely block the tube. For example, the wall thickness of the tube at the contact point has become thin due to repeated blockages, resulting in failure to block the tube. Corresponding fluid leakage occurs. Leakage can also occur when the diameter of the tube and / or the wall thickness of the tube are different from what is expected for the set translation distance, even if the wall thickness of the tube has not worn or become thin.

[0020] This method solves the above problems by monitoring the output of the corresponding current sensor of the electric valve during tube occlusion. The control unit of the device or cycler determines whether the output from the current sensor indicates a spike or characteristic change indicating that the tube is completely blocked and that the threaded shaft and rounded head are pressing against the stop, which forces the rotary nut motor into a stalled state. That is, the rotary nut motor tries to continue rotating the rotary nut and draws more current in the fully closed state at the end of the progression. The additional current draw is detected by the current sensor. If the output from the current sensor does not indicate a spike or characteristic change indicating that the tube is completely blocked, the control unit continues to monitor the current sensor, rotates the rotary nut motor, and further translates the threaded shaft and rounded head. If the output from the current sensor indicates a spike or characteristic change indicating that the tube is completely blocked, the control unit stops the power to the rotary nut motor.

[0021] In a first aspect of the present disclosure, which can be combined with any other aspect or part thereof without limiting the present disclosure in any way, 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, and a pinch valve positioned and arranged to block the tube to prevent the medical fluid from flowing through the tube, the pinch valve including a motor, a current sensor positioned and arranged to sense a current drawn by the motor of the pinch valve, and a control unit operable with the current sensor to monitor the current drawn by the motor while the motor closes the tube with the pinch valve, the control unit being configured to stop the motor when the monitored current indicates occlusion of the tube.

[0022] In a second aspect of the present disclosure, which can be combined with any other aspect or part thereof, the monitored current indicates occlusion of the tube by increasing.

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

[0024] In a fourth aspect of the present disclosure, which can be combined with any other aspect or part thereof, the current sensor is configured to sense currents drawn by motors of a plurality of pinch valves.

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

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

[0027] In a seventh aspect of the present disclosure that can be combined with any other aspect or portion thereof, the shaft includes a head that contacts the tube, the valve further includes a stop, and the head closes the tube against the stop.

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

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

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

[0031] In an eleventh aspect of the present disclosure that can be combined with any other aspect or portion thereof, the control unit is configured to wait for a moment after the monitored current first indicates occlusion of the tube before stopping the motor.

[0032] In a twelfth aspect of the disclosure, which can be combined with any other aspect or portion thereof, 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, and a pinch valve positioned and arranged to block the tube to prevent the medical fluid from flowing through the tube, the pinch valve including a motor, a sensor positioned and arranged to sense a change in a characteristic 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 the change in the characteristic is sensed.

[0033] In a thirteenth aspect of the disclosure, which can 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 disclosure, which can be combined with any other aspect or portion thereof, the change in the characteristic is an increase in a characteristic in the current drawn by the motor.

[0035] In a fifteenth aspect of the disclosure, which can be combined with any other aspect or portion thereof, the control unit is configured to wait for a moment after the change in the characteristic is sensed and before stopping the motor.

[0036] In a sixteenth aspect of the disclosure, which can be combined with any other aspect or portion thereof, a method of controlling an electric pinch valve for the flow of a medical fluid includes: (i) supplying power to a motor of the electric pinch valve such that a shaft of the electric pinch valve moves in a tube-blocking direction; (ii) monitoring a sensor output indicative of the current drawn by the motor while power is supplied to the motor; (iii) returning to (i) if a change in the sensor output characteristic of tube blockage is not detected; and (iv) stopping the power to the motor if a change in the sensor output characteristic of tube blockage is detected.

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

[0038] In an eighteenth aspect of the present disclosure that can be combined with any other aspect or portion thereof, the output characteristics of the occlusion of the tube include an increase in the current drawn by the motor.

[0039] In a nineteenth aspect of the present disclosure that can be combined with any other aspect or portion thereof, in (iv), the change in the sensor output characteristics of the occlusion of the tube is detected over a sufficient period to ensure that the change is due to the occlusion of the tube and not due to any other abnormality.

[0040] In a twentieth aspect of the present disclosure that can be combined with any other aspect or portion thereof, the change in the sensor output characteristics of the occlusion of the tube is detected regardless of tube wear, tube softness, or tube manufacturing tolerances.

[0041] In a twenty - first aspect of the present disclosure that can be combined with any other aspect or portion thereof, any of the features, functionalities, and alternatives described in relation to any one or more of FIGS. 1 to 6D can be combined with any of the features, functionalities, and alternatives described in relation to any of the others of FIGS. 1 to 6D.

[0042] In light of the above aspects and the present disclosure described herein, one advantage of the present disclosure is to provide a medical fluid system having improved electric pinch valve operation.

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

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

[0045] Moreover, one 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 - preventing tube clamping that is independent of changes in tube thickness and wear due to repeated clamping.

[0047] Additional features and advantages will be described in, and will be apparent from, the following detailed description and drawings. The features and advantages described herein are not all - inclusive, and in particular, many additional features and advantages will be apparent to one of ordinary skill in the art upon consideration of the drawings and description. Also, any particular embodiment need not have all of the advantages listed herein, and it is expressly contemplated that individual advantageous embodiments may be claimed separately. Further, it should be noted that the language used herein has been selected primarily for readability and description purposes and is not intended to limit the scope of the subject matter of the invention.

Brief Description of the Drawings

[0048]

Figure 1

[0049]

Figure 2

[0050]

Figure 3

[0051]

Figure 4

[0052]

Figure 5

[0053]

Figure 6A

Figure 6B

Figure 6C

Figure 6D

DETAILED DESCRIPTION OF THE INVENTION

[0054] Referring now to the drawings, and in particular to FIG. 1, an exemplary system 10 including the operation of the electric pinch valve of the present disclosure is illustrated. System 10 includes a dialysis device 20 (such as an automated peritoneal dialysis (“PD”) device), and the dialysis device 20 operates a medical fluid handling device 70 (such as a dialysis fluid cassette). Although the system 10 is primarily described in relation to PD, the improved electric valve operation of the present disclosure is applicable to devices used in any dialysis method 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 treatment fluid or patient fluid is controlled by one or more valves.

[0055] The PD device 20 of the illustrated embodiment includes a housing 22 that defines a pump interface 24, and the pump interface 24 has a pump actuator or pump operating region 26 for operating a medical fluid handling device 70. The pump operating 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 pump out or discharge stroke, for example, (i) pushing fresh heated dialysate into the peritoneal cavity 14 of the patient 12 via the patient line 16 and the patient transfer set 18 at, for example, 14 kPa (2.0 psig) or more, (ii) pushing fresh dialysate into a heating container (not shown) heated to body temperature (e.g., 37°C) by a dialysate heater (not shown) at a higher system pressure, or (iii) pushing used dialysate out to a drain at a higher system pressure. The pump operating region 26 of the illustrated embodiment is pneumatically actuated via a negative pneumatic line 32 extending from a negative pneumatic source 34 to perform a pump in or draw-in stroke, for example, (i) drawing in fresh dialysate from a dialysate source 40 through a supply line 42 at a higher system pressure, (ii) drawing in fresh heated dialysate from a heating container (not shown) at a higher system pressure, or (iii) drawing in used dialysate 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, perhaps, a negative pressure exceeding that.

[0056] The patient line 16 can be 3 to 7 meters in length, for example, approximately 4.5 or 6.7 meters, and can have an inner diameter of, for example, 2 to 4 millimeters (mm) and a wall thickness of about 1 mm. The supply line 42 can also have an inner diameter of, for example, 2 to 4 mm and a wall thickness of about 1 mm. 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 electro-pneumatic valves, such as valves 48, 50, 52, and 56. The pneumatic valve 48 is positioned in the positive air pressure line 28 so as to selectively enable the positive pressure from the pressure source 30 to reach the pump operating region 26. The pneumatic valve 50 is positioned in the negative air pressure line 32 to selectively enable the negative pressure from the pressure source 34 to reach the pump operating region 26. The vent valve 52 is provided in a vent line 54 in communication with the positive air pressure line 28 to selectively release the positive pressure in the line 28 and the pump operating region 26 to the atmosphere. The second vent valve 56 is provided in a vent line 58 in communication with the negative air pressure line 32 to selectively release the negative pressure in the line 32 and the pump operating region 26 to the atmosphere. In an alternative embodiment, a single vent valve and line can be provided to release both the positive and negative pressures from the pump operating region 26 to the atmosphere.

[0057] FIG. 1 further illustrates that the PD device 20 includes a positive air pressure regulator 66, such as a variable orifice valve, disposed along the positive air pressure line 28, and a negative air pressure regulator 68, such as a variable orifice valve, disposed along the negative air pressure line 32. The positive air pressure regulator 66 sets the positive air pressure delivered to the pump operating region 26 to a desired controlled level, which is also the pressure of the fresh PD fluid or used PD fluid delivered from the dialysate cassette 70. The negative air pressure regulator 68 sets the negative air pressure drawn in at the pump operating region 26 to a desired controlled level, which is also the pressure of the fresh PD fluid or used PD fluid delivered to the dialysate cassette 70. In an alternative embodiment, the PD device 20 can be configured pneumatically such that a single pressure regulator, such as a variable orifice valve, operates as a positive air pressure regulator and a negative air pressure regulator at different times.

[0058] 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 the control unit 60 of the PD device 20. The control unit 60 of the illustrated embodiment includes one or more processors 62a and one or more memories 62b. The control unit 60 can have any one or more of a master controller, a safety controller, a video controller, and / or a subcontroller or delegate controller.

[0059] In the illustrated embodiment of FIG. 1, the medical fluid handling device or disposable cassette 70 includes an operating chamber 72, and the pump operating chamber 72 mates with the pump operating region 26 to form the entire pumping chamber. The medical fluid handling device 70 of the illustrated embodiment includes a flexible membrane, diaphragm or sheet 74, The diaphragm or sheet 74 is sized to fit within the pump actuation chamber 72 or (as shown) may be sized to cover the entire side of the medical fluid handling device 70, with a portion of the membrane 74 covering the pump actuation chamber 72, such portion being at least substantially flat or may be pre-domed or pre-formed to fit one or both of the pump actuation region 26 and the pump actuation chamber 72. The control unit 60 causes a negative pressure from the pressure source 34 to be applied to the flexible membrane 74, pulling the sheet against the walls of the pump actuation region 26 and correspondingly drawing fresh PD fluid or used PD fluid into the pump actuation chamber 72. To do so, the control unit causes valves 48, 52, 56 to be closed and valve 50 to be opened. During filling of the pump actuation chamber 72, the pressure sensor 46 measures the negative pumping pressure, which is used as feedback in a pressure control routine to set the level of negative air pressure applied in the pump actuation region 26 via the negative pressure regulator 68.

[0060] The control unit 60 causes a positive pressure from the pressure source 30 to be applied to the flexible membrane 74, pushing the sheet against the walls of the pump actuation chamber 72 and correspondingly pushing fresh PD fluid or used PD fluid out of the pump actuation chamber 72. To do so, the control unit causes valves 50, 52, 56 to be closed and valve 48 to be opened. During discharge of the pump actuation chamber 72, the pressure sensor 44 measures the positive pumping pressure, which is used as feedback in a pressure control routine to set the level of positive air pressure applied in the pump actuation region 26 via the positive pressure regulator 66.

[0061] The control unit 60 can determine the flow rates of fresh PD fluid and used PD fluid pumped by the PD device 20 of the system 10 in at least one of a plurality of different ways. In one way, the fixed volumes of the pump operating region 26 and the pump operating chamber 72 collectively form a known full stroke volume. The control unit 60 counts the number of delivered full strokes, multiplies that count by the known full stroke volume, and divides the result by the corresponding time required to make the number of delivered full strokes to determine the local or current PD fluid flow rate.

[0062] Alternatively or additionally, the control unit 60 obtains pressure measurements before and after a fill stroke or a discharge stroke and uses an ideal gas law algorithm, as known in the art, to determine the volume resulting from fresh or used PD fluid drawn into or discharged from the pump operating chamber 72. To do so, the PD device 20 may provide reference chambers (not shown) of known fixed positive and negative volumes, which may be pneumatically connected to positive and negative vent lines 54, 58, respectively. The control unit 60 then adds the volumes of successive fill or discharge strokes determined by the ideal gas law algorithm and divides the sum by the corresponding time required to make the successive fill or discharge strokes to determine the local or current PD fluid flow rate. The method of the ideal gas law algorithm for determining the local or current flow rate is advantageous because full strokes of the diaphragm or sheet 74 through the pump operating region 26 and the pump operating chamber 72 are not required. Partial strokes may be made and considered in determining the local or current flow rate.

[0063] The PD device 20 provides two pump operating regions 26 and pump operating chambers 72, which operate in an alternating manner (one fills while the other discharges), whereby it should be understood that the flow rate of fresh or used PD fluid is likely to be continuous for the most part. Further, although FIG. 1 illustrates pneumatically driven pump operating regions 26 and pump operating chambers 72, the PD fluid pumping of system 10 can alternatively be driven electromechanically via, for example, piston, gear, peristaltic or centrifugal pumps.

[0064] Regardless of the type of pumping used by system 10, the PD device 20 includes electromechanical pinch valves 80a, 80b that are under the control of the control unit 60 in the illustrated embodiment. As shown in FIG. 1, the electric pinch valve 80a is operable with the supply line 42, and the electric pinch valve 80b is operable with the patient line 16. Although FIG. 1 illustrates two electric pinch valves 80a, 80b, the PD device 20 of system 10 may include additional fluid valves for additional pump operating chambers 72 (which operate in an alternating manner to provide a more continuous flow and are not shown in FIG. 1 for simplicity), and additional electric pinch valves such as additional fluid valves for multiple supply lines 42, fluid heater lines, and / or drain lines.

[0065] FIG. 1 illustrates that the control unit 60 may further include one or more current sensors 64a, 64b that operate with one or more processors 62a and / or one or more memories 62b. Dedicated current sensors 64a, 64b may be provided for each of the electric pinch valves 80a, 80b, respectively, to allow for fully independent operation of each of the valves. Alternatively, for example, one or more current sensors 64a, 64b may be provided for a plurality of electric pinch valves 80a, 80b if it is guaranteed that the timing of the start of operation of the pinch valves 80a, 80b does not overlap. The current sensors 64a, 64b are illustrated as being provided, together with the control unit 60, for example, on the control board of the control unit 60, but the current sensors 64a, 64b may alternatively be disposed within the pinch valves 80a, 80b, respectively.

[0066] Figures 2A and 2B illustrate the electric pinch valves 80a, 80b in more detail. In the illustrated embodiment, each of the electric pinch valves 80a, 80b includes a rotary nut motor 82 under the control of the control unit 60. The rotary nut motor 82 can be a stepping motor. The rotary nut disposed within the rotary nut motor 82 is translationally fixed such that rotation of the rotary nut translates the threaded shaft 84 passed through the rotary nut in both the valve closing direction and the valve opening direction in an accurate manner. The end of the threaded shaft 84 that contacts the tube (e.g., the patient line 16 or the supply line 42 of FIG. 1) is provided with a rounded head or wedge 86 that enables the tube or lines 16, 42 to be occluded without damaging the line or tube. The pinch valves 80a, 80b of FIGS. 2A and 2B also include a stop 88 against which the rounded head or wedge 86 compresses the tube or lines 16, 42. The rotary nut motor 82 rotates the rotary nut in a first direction, e.g., clockwise, translating the threaded shaft 84 and the rounded head 86 in the first direction toward the stop 88 to occlude the tube or lines 16, 42. The rotary nut motor 82 rotates the rotary nut in a second direction, e.g., counterclockwise, translating the threaded shaft 84 and the rounded head 86 in a second direction away from the stop 88 to allow the flow of medical fluid through the tube or lines 16, 42.

[0067] Figure 3 illustrates a prior art method 100 of closing a flexible tube using an electric pinch valve. At ellipse 102, method 100 begins. At block 104, a rotary nut motor, such as a stepper motor, is moved a calculated number of commanded steps that, in combination with the geometry of the threaded shaft, produces the translational movement of the threaded shaft and rounded head necessary to close the tube or line. The motor is stopped when the commanded number of motor steps has been moved, as illustrated at block 106. At ellipse 108, method 100 ends. FIGS. 4A and 4B illustrate problems associated with method 100. If the contact portions of tubes or lines 16, 42 have their expected thicknesses as in FIG. 4A, translating the threaded shaft and rounded head the calculated fixed distance (to the dotted line) will properly close tubes or lines 16, 42. However, if the contact portions of tubes or lines 16, 42 are thinner, for example, as in FIG. 4B, due to repeated tightening or closing, or due to manufacturing tolerances where the tube walls are manufactured thinner than specified or intended, translating the threaded shaft and rounded head the calculated fixed distance (to the dotted line) will not cause tubes or lines 16, 42 to be properly closed and will cause leakage.

[0068] Figure 5 illustrates a method 110 of the present disclosure for closing flexible tubes 16, 42 using electric pinch valves 80a, 80b. At ellipse 112, method 110 begins. At block 114, control unit 60 causes rotary nut motor 82 to rotate and begins translating threaded shaft 84 and rounded head 86 toward stop 88. At block 114, control unit 60 also begins monitoring the outputs of current sensors 64a, 64b associated with pinch valves 80a, 80b. As discussed above, any current sensors 64a, 64b can be associated with one or more electric pinch valves 80a, 80b.

[0069] In diamond 116, the control unit 60 determines whether the outputs from current sensors 64a, 64b indicate a spike or a characteristic change (the spike or characteristic change indicates that tubes or lines 16, 42 are completely blocked and that threaded shaft 84 and rounded head 86 are pressing against stop 88, which is causing rotary nut motor 82 to stall). That is, rotary nut motor 82 tries to keep rotating its rotary nut and draws in more current in the fully blocked state at the end of travel. The additional current draw is detected by current sensors 64a, 64b. If the outputs from current sensors 64a, 64b in diamond 116 do not indicate a spike or a characteristic change indicating that tubes or lines 16, 42 are completely blocked, method 110 returns to block 114, and control unit 60 continues to monitor current sensors 64a, 64b, rotates rotary nut motor 82, and translates threaded shaft 84 and rounded head 86 towards stop 88. If the outputs from current sensors 64a, 64b in diamond 116 indicate a spike or a characteristic change indicating that tubes or lines 16, 42 are completely blocked, method 110 moves to block 118, and control unit 60 stops rotary nut motor 82. In ellipse 120, method 110 ends.

[0070] Figures 6A through 6D illustrate method 110 in more detail with a continuous display of the closing electric pinch valves 80a, 80b. In Figure 6A, control unit 60 causes rotary nut motor 82 to be powered and threaded shaft 84 and rounded head 86 to begin translation. The corresponding outputs from current sensors 64a, 64b, as shown on display 90, indicate that rotary nut motor 82 during the start of closing initially draws a normal (or expected) amount of current. In Figure 6B, control unit 60 continues to power rotary nut motor 82 and causes threaded shaft 84 and rounded head 86 to continue translating into contact with and begin compressing tube or line 16, 42. The corresponding outputs from current sensors 64a, 64b, as shown on display 90, indicate that rotary nut motor 82 in the first tube contact portion of closing continues to draw a normal (or expected) amount of current.

[0071] In FIG. 6C, the control unit 60 continues to cause the rotary nut motor 82 to be powered and the threaded shaft 84 and the rounded head 86 to continue to translate so as to continue to block the tubes or lines 16, 42. The corresponding outputs from the current sensors 64a, 64b as shown on the display 90 indicate that the rotary nut motor 82 in the further tube contact portion of the blockage continues to draw a normal (or expected) amount of current. In FIG. 6D, the control unit 60 attempts to cause the rotary nut motor 82 to rotate and the threaded shaft 84 and the rounded head 86 to continue to translate so as to continue to block the tubes or lines 16, 42. However, since the tubes or lines 16, 42 are completely compressed between the rounded head 86 and the stop 88, the rotary nut can no longer rotate. The rotary nut motor 82 enters a stalled state and draws more current as it attempts to continue rotating the rotary nut. The corresponding outputs from the current sensors 64a, 64b as shown on the display 90 detect the additional current draw, and the additional current draw indicates that the threaded shaft 84 and the rounded head 86 have completely blocked the tubes or lines 16, 42 and now the head 86 is pressing against the stop 88. The control unit 60 quickly senses the current spike or characteristic increase and cuts off the power to the rotary nut motor 82. The tubes or lines 16, 42 are completely blocked in FIG. 6D. In one embodiment, the control unit 60 is programmed to wait for a period, such as about 1 second, to ensure that the current spike or characteristic increase is due to the complete blockage of the tubes or lines 16, 42 and not due to some other current spike anomaly. That is, the control unit 60 can continue to cause the rotary nut motor 82 to press against the tubes or lines 16, 42 (e.g., after first confirming the current spike or characteristic increase, for about 1 second). Small current spikes that do not indicate complete blockage typically occur due to noise.However, for example, after checking for an increase in characteristics for about one second, the control unit 60 safely determines a complete occlusion of the tube or line 16, 42. However, it should be understood that care is taken to ensure that the motor is not powered for a long enough time to become heated.

[0072] In one embodiment, the control unit 60 does not monitor the outputs from the current sensors 64a, 64b in rotating the rotary nut motor 82 in a direction opposite to the tube opening direction. Here, the control unit 60 can be programmed to operate the rotary nut motor 82 in the opposite direction for the determined number of steps of the stepping motor or until the limit switch is triggered (e.g., to allow the use of a less expensive non-stepping motor), in which case it is known that the tip of the rounded head 86 is away from the tube or line 16, 42, whereby the tube can be fully opened to allow a medical fluid (e.g., PD fluid) to flow through the tube.

[0073] Figures 5 and 6A through 6D show that the structure and corresponding methodology of the electric pinch valves 80a, 80b of the present disclosure can successfully occlude the tube or line 16, 42 regardless of the diameter of the tube (the tubes 16, 42 must first fit within the space between the rounded head 86 and the stop 88 of Figure 6A), and regardless of whether the wall thickness of the tubes 16, 42 changes over time due to repeated occlusions, or whether the tubes 16, 42 become softer over repeated occlusions (in which case the tubes 16, 42 need to be compressed more to form a good seal). The successful occlusion of the tube or line 16, 42 occurs regardless of manufacturing tolerances.

[0074] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Accordingly, such changes and modifications are intended to be covered by the appended claims. For example, although system 10 is illustrated as operating with a disposable cassette 70, system 10 may alternatively use durable or reusable components that are sterilized, such as by heat sterilization after use. In this case, flexible lines or tubes 16, 42 may instead be provided inside the PD device or cycler 20, in which case the lines are sterilized after treatment. Although sensors 64a, 64b are described as current sensors, other types of sensors such as resistance sensors, Hall effect sensors, and current transformers may also be used.

Claims

1. A medical fluid system, wherein the 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 including a motor, the pinch valve; A current sensor positioned and arranged to sense a current drawn by the motor of the pinch valve; A control unit operable with the current sensor to monitor the current drawn by the motor while the motor closes the tube with the pinch valve; and The control unit is configured to stop the motor when the monitored current indicates blockage of the tube. A medical fluid system.

2. The medical fluid system according to claim 1, wherein the monitored current indicates the blockage of the tube by increasing.

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

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

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

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

7. The shaft includes a head that contacts the tube, the valve further includes a stop portion, and the head closes the tube against the stop portion. The medical fluid system according to claim 5.

8. The tube is a first tube, the pinch valve is a first pinch valve, and the control unit is operable with the current sensor or a second current sensor to monitor the current drawn by a second motor of the second pinch valve while the second motor closes a second tube with the second pinch valve, and the control unit is further configured to stop the second motor when the monitored current indicates occlusion of the second tube. The medical fluid system according to claim 1.

9. The control unit is further configured to operate the motor in the opposite direction without monitoring the current drawn by the motor to allow medical fluid to flow through the tube. The medical fluid system according to claim 1.

10. The tube is disposable or reusable. The medical fluid system according to claim 1.

11. The control unit is configured to wait for a moment after the monitored current first indicates occlusion of the tube before stopping the motor. The medical fluid system according to claim 1.

12. A medical fluid system, the 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 block the tube to prevent medical fluid from flowing through the tube, the pinch valve including a motor, the pinch valve A sensor positioned and arranged to sense a change in a characteristic associated with the motor of the pinch valve when the tube is blocked, A control unit operable with the sensor, Comprising, The control unit is configured to stop the motor when the change in characteristics is sensed, a medical fluid system.

13. The sensor is a current sensor, a resistance sensor, a Hall effect sensor, or a current transformer, the medical fluid system according to claim 12.

14. The change in characteristics is an increase in characteristics in the current drawn by the motor, the medical fluid system according to claim 12.

15. The control unit is configured to wait for a moment after the change in characteristics is sensed and before stopping the motor, the medical fluid system according to claim 12.

16. A method for controlling an electric pinch valve for the flow of a medical fluid, the method 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) Monitoring a sensor output indicative of the current drawn by the motor while power is being supplied to the motor; (iii) Returning to (i) if no change in the sensor output characteristics of the tube blockage is detected; (iv) Stopping the power to the motor if a change in the sensor output characteristics of the tube blockage is detected. Including, a method.

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

18. The method according to claim 16, wherein the output characteristics of the occlusion of the tube include an increase in the current drawn by the motor. **Claim 19** The method according to claim 16, wherein in (iv), the change in the sensor output characteristics of the occlusion of the tube is detected over a period sufficient to ensure that the change is due to the occlusion of the tube and not due to any other abnormality. **Claim 20** The method according to claim 16, wherein the change in the sensor output characteristics of the occlusion of the tube is detected regardless of tube wear, tube softness, or tube manufacturing tolerances.

Images