Peritoneal dialysis system using cylinders and selectable air pumps

Abstract

In one example, a control unit (i) opens the second pneumatic valve and the source fluid valve and causes the linear actuator to move the piston head into the first cylinder chamber to create a negative pressure in the pneumatic pump chamber to draw the source fluid into the fluid pump chamber, and (ii) opens the first pneumatic valve and the destination fluid valve to cause the linear actuator to move the piston head into the first cylinder chamber to create a negative pressure in the pneumatic pump chamber to draw the source fluid into the fluid pump chamber. And causing the linear actuator to move the piston head into the first cylinder chamber to urge source fluid through the destination fluid valve, the control unit controlling the linear actuator using pressure sensor readings such that the final pressure for (ii) is at least substantially equal to the initial pressure for (ii), and causing the linear actuator to move the piston head into the first cylinder chamber to urge source fluid through the destination fluid valve. Such that a volume of space corresponding to movement of the piston head within the cylinder during (ii) equals a volume of source fluid delivered from the fluid pump chamber.

Description

Technical Field

[0001] The present disclosure relates generally to medical fluid therapy, and in particular to dialysis fluid therapy. Background Art

[0002] For a variety of reasons, a person's kidney system can 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 and other substances, may accumulate in the patient's blood and tissues.

[0003] Dialysis is used to treat decreased kidney function, especially kidney failure. Dialysis removes waste products, toxins, and excess water from the body that would normally be removed by the kidneys. Dialysis treatment to replace kidney function is vital for many people because it is life-saving.

[0004] One type of kidney 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 (which is 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 replacement or substitution fluid to the extracorporeal circuit during treatment. During the course of HF treatment, the replacement fluid and the patient's accumulated fluid between treatments are ultrafiltered, providing a convective transport mechanism that is particularly beneficial for the removal of middle and large molecules.

[0006] Hemodiafiltration ("HDF") is a treatment modality that combines convective and diffusive clearance. Similar to standard hemodialysis, HDF uses dialysis fluid flowing through the dialyzer to provide diffusive clearance. In addition, a replacement solution is provided directly to the extracorporeal circuit, thereby providing convective clearance.

[0007] Most HD, HF and HDF treatments are performed in centers. Today there is a trend toward home hemodialysis ("HHD"), in part because HHD can be performed every day, which provides therapeutic benefits compared to hemodialysis treatments in centers that are usually performed every two or three weeks. Studies have shown that more frequent treatments remove more toxins and wastes and provide less interdialytic fluid overload than patients who receive less frequent but potentially longer treatments. Patients who receive more frequent treatments do not experience as many down cycles (fluctuations of fluids and toxins) as patients in centers who have accumulated toxins for two or three days before treatment. In some areas, the nearest dialysis center may be many miles away from the patient's home, which results in home treatment time taking up a large part of the day. Treatment at a center near the patient's home may also take up a large part of the patient's day. HHD can be performed at night or during the day while the patient is relaxing, working or otherwise producing.

[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 peritoneum 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 peritoneum. The 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 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 pass the fresh dialysis fluid through the catheter and into the patient. 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 process, for example four times a day. Manual peritoneal dialysis requires a lot of time and effort from the patient, leaving a lot of room for improvement.

[0010] Automated peritoneal dialysis ("PD") is similar to CAPD in that dialysis treatment includes a drain cycle, a fill cycle, and a dwell cycle. However, an automated PD machine automatically performs these cycles, typically while the patient is sleeping. An automated PD machine relieves the patient from having to manually perform treatment cycles or deliver supplies during the day. The automated PD machine is fluidly connected to an implanted catheter, a source or bag of fresh dialysis fluid, and a fluid drain. The automated PD machine pumps fresh dialysis fluid from a dialysis fluid source through a catheter and into the patient's peritoneal compartment. The automated PD machine also allows the dialysis fluid to remain within the peritoneal compartment and allows the transfer of waste, toxins, and excess water to occur. The source may include multiple liters of dialysis fluid, which may include several bags of solution.

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

[0012] In any of the above modes of using an automated machine, the automated machine is typically operated with a disposable kit that is discarded after a single use. Depending on the complexity of the disposable kit, the cost of using one kit per day may become significant. Moreover, daily disposables require space for storage, which may become a nuisance for homeowners and businesses. In addition, replacement of daily disposables requires daily setup time and effort by the patient or caregiver at home or in a clinic.

[0013] The APD device also needs to be portable so that the patient can take his or her device on vacation or for work travel. In addition, the APD device needs to have pumping accuracy so that the device can accurately track how much ultrafiltration ("UF") is removed from the patient during treatment.

[0014] For each of the above reasons, it would be desirable to provide a relatively simple, compact dialysis machine, such as an APD machine, that is accurate, and a single-use kit that is simple to operate and cost-effective. Summary of the invention

[0015] The present disclosure relates to a peritoneal dialysis ("PD") machine or cycler driven by a pneumatic cylinder and an optional air pump. In a first main embodiment, only the pneumatic cylinder is provided. The cylinder is located between a first pneumatic pump chamber and a second pneumatic pump chamber. A piston is located within the cylinder, wherein the piston includes a piston head that divides the cylinder into a first cylinder chamber and a second cylinder chamber. A first pneumatic line extends from the first cylinder chamber to the first pneumatic pump chamber. A second pneumatic line extends from the second cylinder chamber to the second pneumatic pump chamber. A first pressure sensor is positioned to read the air pressure in the first pneumatic line, the first pneumatic pump chamber, and the first cylinder chamber. A second pressure sensor is positioned to read the air pressure in the second pneumatic line, the second pneumatic pump chamber, and the second cylinder chamber.

[0016] A first exhaust line and an associated first exhaust valve are optionally placed in fluid communication with the first cylinder chamber. A second exhaust line and an associated second exhaust valve are optionally placed in fluid communication with the second cylinder chamber. The piston also includes a piston shaft that is coupled to a linear actuator outside the cylinder for translating the piston shaft and the piston head within the cylinder.

[0017] All valves, motors for linear actuators, PD fluid heaters and other controllable electrical devices are under the control of a control unit that includes at least one processor, at least one memory and a video controller for controlling a user interface. The control unit is also configured to receive signals from all sensors such as pneumatic pressure sensors, fluid pressure sensors (if provided), motor encoders (if provided, for linear actuators) and any temperature sensors associated with the heaters. The control unit is programmed to run all pumping sequences discussed herein.

[0018] In one embodiment, the PD machine or the circulation machine is operated with a disposable kit. Among other items, the disposable kit includes the first fluid pump chamber and the second fluid pump chamber that operate with the first pneumatic pump chamber and the second pneumatic pump chamber respectively. When the piston head moves so as to produce negative pneumatic pressure in the first cylinder chamber or the second cylinder chamber, a corresponding negative pressure is produced in the corresponding first pneumatic pump chamber or the second pneumatic pump chamber. The negative pressure produced in the first pneumatic pump chamber or the second pneumatic pump chamber then pulls the flexible membrane of the corresponding first fluid pump chamber or the second fluid pump chamber into the first pneumatic pump chamber or the second pneumatic pump chamber, so that the fluid pump chamber is filled with fresh or used PD fluid. When the piston head moves so as to produce positive pneumatic pressure in the first cylinder chamber or the second cylinder chamber, a corresponding positive pressure is produced in the corresponding first pneumatic pump chamber or the second pneumatic pump chamber. The positive pressure produced in the first pneumatic pump chamber or the second pneumatic pump chamber then pushes the flexible membrane of the corresponding first fluid pump chamber or the second fluid pump chamber, so that the fluid pump chamber is closed and discharges fresh or used PD fluid.

[0019] The control unit in the first main embodiment causes the piston shaft to translate the piston head back and forth within the cylinder so that in one half-stroke (i), the first pump chamber is filled with fresh or used PD fluid, while the second fluid pump chamber is discharged with fresh or used PD fluid. In the second half-stroke (ii), the second pump chamber is filled with fresh or used PD fluid, while the first fluid pump chamber is discharged with fresh or used PD fluid. The control unit causes the piston head to translate back and forth in the above manner until a desired or specified volume of fresh or used PD fluid from a desired PD fluid source is delivered to a desired PD fluid destination. Fluid valves are provided and are sequentially actuated by the control unit to approach a desired fluid source and a desired fluid destination. The fluid valve can be, for example, a magnetically actuated solenoid valve, an electric pinch valve, or a pneumatically actuated valve.

[0020] In a first main embodiment, and in situations where patient pumping is occurring so that pressure control is important, the control unit monitors the outputs from the first and second pressure sensors while the piston head translates back and forth. The control unit controls the speed of the back and forth translation so that the desired safe negative or positive fluid pumping pressure is not exceeded.

[0021] In the first main embodiment, the amount of fresh or used PD fluid delivered to the destination is determined by maintaining a constant pressure before and after the piston head moves, which offsets the compressible effect of the air in the cylinder. Since the pressure after the movement (P2) is equal to the pressure before the movement (P1), the volume of air in the cylinder remains constant. Therefore, the volume displaced by the piston head is equal to the volume of fluid delivered.

[0022] In a second main embodiment, only an air cylinder is provided as before, but wherein the cylinder is dedicated to a single pneumatic pump chamber / fluid pump chamber pair. Two pneumatic pump chamber / fluid pump chamber pairs may be provided, wherein each pair has its own dedicated air cylinder. The structure of the air cylinder is the same as in the first main embodiment, including a piston head and piston shaft driven by a linear actuator. An optional exhaust line and pneumatic exhaust valve may be in pneumatic communication with the first and second chambers of each air cylinder.

[0023] In a second main embodiment, a first pneumatic line and a second pneumatic line extend from the first cylinder chamber and the second cylinder chamber, respectively, to the same pneumatic pump chamber. A first pneumatic valve and a second pneumatic valve under the control of a control unit are provided along the first pneumatic line and the second pneumatic line. One or more pressure sensors are provided along a common portion of the first pneumatic line and the second pneumatic line or along each of the first pneumatic line and the second pneumatic line. A fluid pump chamber is again provided as part of a disposable kit, wherein the fluid pump chamber pumps fresh or used PD fluid from a desired PD fluid source to a desired destination as determined by a sequence of one or more fluid valves.

[0024] The control unit in the second main embodiment causes the piston shaft to translate the piston head toward one of the first cylinder chamber or the second cylinder chamber (e.g., the first cylinder chamber), thereby generating a positive pressure in the first cylinder chamber and a negative pressure in the second cylinder chamber. The control unit also causes the source fluid valve and the second pneumatic valve to open, so that the negative pressure is allowed to reach the pneumatic pump chamber and the flexible membrane is pulled into the pneumatic pump chamber and filled with fresh or used PD fluid.

[0025] Next, the control unit closes the source fluid valve and the second pneumatic valve and opens the first pneumatic valve so that the pressure sensor can read a positive pressure in the first cylinder chamber. The control unit also moves the piston into the first cylinder chamber so that the positive pressure in the pneumatic pump chamber reads a desired pressure, such as 1.5 psig, to pump fresh or used PD fluid to the desired destination. At the end of this movement, the piston head is in the initial piston head position.

[0026] Next, the control unit maintains the first pneumatic valve in an open state and causes the destination fluid valve to open. The desired positive pressure established in the pneumatic pump chamber causes the flexible membrane of the fluid pump chamber to collapse and push fresh or used PD fluid to the desired destination. As the positive pressure dissipates, the control unit causes the piston to move further into the first cylinder chamber so that the pressure sensor continues to read the desired pressure, for example, 1.5 psig.

[0027] Eventually, the flexible membrane cannot collapse further, causing the pressure sensor reading to reach a peak, at which point the control unit stops the pump-out translation of the piston head and closes the destination fluid valve. Alternatively or additionally, the detection that the flexible membrane cannot collapse further can be determined by the control unit detecting that the linear actuator and / or piston head do not move while maintaining the desired pressure (e.g., 1.5 psig). In any case, after stopping the pump-out translation, the first pneumatic valve remains open to allow the positive pressure that has been maintained at the desired pressure to balance between the first cylinder chamber and the pneumatic pump chamber, and this positive pressure can be read by the pressure sensor. The piston head is now in the final piston head position. The volume difference of the cylinder at a known cross-sectional area between the final piston head position and the initial piston head position is the volume of fresh or used PD fluid pumped to the desired destination due to the same pressure at the initial piston head position and the final piston head position (e.g., 1.5 psig, which is the desired pump-to-patient pressure). That is, the volume of the space corresponding to the movement of the piston head in the cylinder varies with the distance the piston head moves in the cylinder and the cross-sectional area of ​​the inner diameter of the cylinder.

[0028] Next, with the second cylinder chamber still under negative pressure (this is not critical if pulling from a non-patient source), the control unit causes the source fluid valve and the second pneumatic valve to open, allowing negative pressure to reach the pneumatic pump chamber and causing the flexible membrane to be pulled into the pneumatic pump chamber and filled with fresh or used PD fluid.

[0029] Next, the control unit closes the source fluid valve, but allows the second pneumatic valve to remain open so that the pneumatic pump chamber and the second cylinder chamber remain exposed to the pressure sensor. The control unit translates the piston into the second cylinder chamber until the pressure sensor reads zero psig. The pressure in the first cylinder chamber should also be close to zero psig.

[0030] Next, with the source and destination fluid valves closed, the first pneumatic valve closed, and the second pneumatic valve open so that the pressure sensor can read a positive pressure in the second cylinder chamber, the control unit moves the piston into the second cylinder chamber so that the positive pressure in the pneumatic pump chamber again reads the desired pressure, e.g., 1.5 psig, for pumping fresh or used PD fluid to the desired destination. At the end of this movement, the piston head is again in the initial piston head position.

[0031] Next, the control unit maintains the second pneumatic valve in an open state and causes the destination fluid valve to open. The desired positive pressure established in the pneumatic pump chamber again forces the flexible membrane of the fluid pump chamber to collapse and push the fresh or used PD fluid to the desired destination. As the positive pressure dissipates, the control unit moves the piston further into the second cylinder chamber so that the pressure sensor continues to read the desired pressure, for example, 1.5 psig.

[0032] Eventually, the flexible membrane cannot collapse further, causing the pressure sensor reading to peak, at which point the control unit stops the pump-out translation of the piston head and closes the destination fluid valve. Alternatively or additionally, detection that the flexible membrane cannot collapse further can be determined by the control unit detecting that the linear actuator and / or piston head are not moving while maintaining the desired pressure (e.g., 1.5 psig). In any case, after stopping the pump-out translation, the second pneumatic valve remains open to allow the positive pressure, which has been maintained at the desired pressure, to balance between the first cylinder chamber and the pneumatic pump chamber, and this positive pressure can be read by the pressure sensor. The piston head is now in the final piston head position. The volume difference of the cylinder at a known cross-sectional area between the final piston head position and the initial piston head position is again the volume of fresh or used PD fluid pumped to the desired destination due to the same pressure at the initial piston head position and the final piston head position (e.g., 1.5 psig, which is the desired pump-to-patient pressure).

[0033] With the first cylinder chamber still under negative pressure (this is not critical if pulled from a non-patient source), the control unit causes the source fluid valve and the first pneumatic valve to open, thereby allowing negative pressure to reach the pneumatic pump chamber and causing the flexible membrane to be pulled into the pneumatic pump chamber and filled with fresh or used PD fluid. The above process is repeated until the desired amount of fresh or used PD fluid is delivered to the desired destination. It should be understood that the above process can be used for any fresh or used PD fluid source and any fresh or used PD fluid destination described herein, and that the aspiration pressure and delivery pressure and the volume of PD fluid delivered can be controlled and measured, respectively.

[0034] The third main embodiment introduces an air pump that operates in conjunction with an air cylinder. The air pump can generally transition more quickly between pumping positive pressure to pumping negative pressure, and vice versa. Moreover, even a small air pump can produce a wide range of pressures. These two advantages of the air pump are combined with the ability of the air cylinder to meter a known volume of fluid under pressure control as described herein.

[0035] The structure of the cylinder in the third main embodiment is substantially the same as that of the first and second main embodiments and includes a piston head and a piston shaft driven by a linear actuator. An optional exhaust line and a pneumatic exhaust valve can be pneumatically connected to the first cylinder chamber and the second cylinder chamber of each cylinder. In the third main embodiment, only the first pneumatic line extends from the cylinder to the pneumatic pump chamber. A first pneumatic valve under the control of the control unit is set along the first pneumatic line. A second pneumatic line extends from the air pump and intersects the first pneumatic line. A second pneumatic valve under the control of the control unit is set along the second pneumatic line. A pressure sensor is set along a common portion of the first pneumatic line and the second pneumatic line. One or more fluid pump chambers are again provided as part of the disposable kit, wherein the fluid pump chamber pumps fresh or used PD fluid from a desired PD fluid source to a desired destination as determined by the sequence of one or more fluid valves.

[0036] The control unit in the third main embodiment initially causes the first pneumatic valve and the second pneumatic valve to open, causes the source fluid valve to open, and causes the air pump to generate a negative pressure in the pneumatic pump chamber and the cylinder chamber, thereby pulling the flexible membrane of the fluid pump chamber into the pneumatic pump chamber and pulling fresh or used PD fluid into the fluid pump chamber. In an embodiment, the control unit monitors the speed of the air pump during the PD fluid extraction phase. When the speed of the air pump begins to decrease, the control unit determines that the flexible membrane is fully pulled and expanded, and therefore the fluid pump chamber is filled with fresh or used PD fluid. Once the flexible membrane is fully pulled, the speed of the air pump is reduced. The control unit provides closed-loop control to the air pump so that the desired pressure is maintained. The control loop via the control unit ensures that the pressure does not extend beyond a set threshold.

[0037] After the fluid pump chamber is completely filled with PD fluid, the control unit closes the source fluid valve. Then, the control unit opens the first pneumatic valve and the second pneumatic valve, and causes the air pump to generate a desired positive pumping pressure (e.g., 1.5 psig) in the pneumatic pump chamber and the cylinder chamber. Once the desired positive pumping pressure is reached, the control unit closes the second pneumatic valve, so that the air pump is isolated and blocked. The piston head of the piston is at the initial piston head position here.

[0038] The control unit then maintains the first pneumatic valve in an open state and causes the destination fluid valve to open. The desired positive pressure established in the pneumatic pump chamber causes the flexible membrane of the fluid pump chamber to collapse and push fresh or used PD fluid to the destination. As the positive pressure dissipates, the control unit moves the piston within the cylinder chamber so that the pressure sensor continues to read the desired pressure, such as 1.5 psig.

[0039] Eventually, the flexible membrane cannot collapse further, causing the pressure sensor reading to reach a peak, at which point the control unit stops the pump-out translation of the piston head and closes the destination fluid valve. Alternatively or additionally, the detection that the flexible membrane cannot collapse further can be determined by the control unit detecting that the linear actuator and / or piston head do not move while maintaining the desired pressure (e.g., 1.5 psig). In any case, after stopping the pump-out translation, the first pneumatic valve remains open to allow the positive pressure that has been maintained at the desired pressure to balance between the cylinder chamber and the pneumatic pump chamber, and this positive pressure can be read by the pressure sensor. The piston head is now in the final piston head position. The volume difference of the cylinder at a known cross-sectional area between the final piston head position and the initial piston head position is the volume of fresh PD fluid pumped to the destination due to the same pressure at the initial piston head position and the final piston head position (e.g., 1.5 psig, which is the desired pump-to-patient pressure).

[0040] The control unit then causes the first and second pneumatic valves to open, causes the source fluid valve to open, and causes the piston to move in the opposite direction within the cylinder to reposition the piston head for the next pump-out stroke. The movement of the piston creates a negative pressure in the cylinder chamber and the pneumatic pump chamber, which can be assisted by the air pump to quickly achieve the desired PD fluid extraction pressure. The flexible membrane of the fluid pump chamber is pulled into the pneumatic pump chamber, and fresh or used PD fluid is correspondingly pulled into the fluid pump chamber. The above process for the third main embodiment is repeated, wherein the control unit accumulates the pump stroke volume until the desired or prescribed amount of fresh or used PD fluid is delivered to the destination.

[0041] The fourth main embodiment also uses an air pump that operates in cooperation with the cylinder. Here, a single air pump and cylinder are capable of driving two fluid pump chambers in two pneumatic pump chambers. The structure of the cylinder in the fourth main embodiment is the same as that in the third main embodiment, and includes a piston head and a piston shaft driven by a linear actuator. An optional exhaust pipeline and a pneumatic exhaust valve can be pneumatically connected to the first cylinder chamber and the second cylinder chamber of each cylinder. In the fourth main embodiment, although only the first pneumatic pipeline extends from the cylinder, the first pneumatic pipeline is bifurcated to also include a second pneumatic pipeline, wherein the first pneumatic pipeline and the second pneumatic pipeline extend to the first pneumatic pump chamber and the second pneumatic pump chamber respectively. The first pneumatic valve and the second pneumatic valve under the control of the control unit are respectively arranged along the first pneumatic pipeline and the second pneumatic pipeline.

[0042] A third pneumatic line extends from the air pump and bifurcates into a fourth pneumatic line. The third pneumatic line intersects the first pneumatic line, and the fourth pneumatic line intersects the second pneumatic line. A third pneumatic valve under the control of the control unit is disposed along the third pneumatic line, and a fourth pneumatic valve under the control of the control unit is disposed along the fourth pneumatic line. A first pressure sensor is disposed adjacent to the first pneumatic pump chamber, and a second pressure sensor is disposed adjacent to the second pneumatic pump chamber. The first fluid pump chamber and the second fluid pump chamber are disposed as part of a disposable kit, wherein the first fluid pump chamber and the second fluid pump chamber pump fresh or used PD fluid from a desired PD fluid source to a desired PD fluid destination, as determined by a sequence of the plurality of fluid valves.

[0043] In the pumping sequence of the fourth main embodiment, the first fluid pump chamber and the second fluid pump chamber are generally alternating, wherein when one fluid pump chamber draws in fresh or used PD fluid, the other fluid pump chamber pushes out fresh or used PD fluid. Each fluid pump chamber has its own set of source valves and destination valves, however, it is not required that the first fluid pump chamber and the second fluid pump chamber are completely synchronized.

[0044] The control unit in the fourth main embodiment initially causes the third pneumatic valve and the source fluid valve for the first fluid pump chamber to open, and causes the air pump to generate a negative pressure in the first pneumatic pump chamber, thereby pulling the flexible membrane of the first fluid pump chamber into the first pneumatic pump chamber and pulling fresh or used PD fluid into the first fluid pump chamber. During the PD fluid extraction phase, the control unit can again monitor the speed of the air pump. When the speed of the air pump begins to decrease beyond a set threshold, the control unit determines that the flexible membrane is fully pulled and expanded, and therefore the fluid pump chamber is full of fresh or used PD fluid, at which time the control unit stops the air pump and closes the source fluid valve for the first fluid pump chamber. The control unit then maintains the third pneumatic valve in an open state and causes the air pump to generate a desired positive pumping pressure (e.g., 1.5 psig read by the first pressure sensor) in the first pneumatic pump chamber. At this time, the piston head of the piston of the cylinder is in an initial piston head position.

[0045] The control unit then closes the third pneumatic valve, opens the first pneumatic valve, and opens the first destination fluid valve. The desired positive pressure established in the first pneumatic pump chamber forces the flexible membrane of the first fluid pump chamber to collapse and push fresh or used PD fluid to the destination. As the positive pressure dissipates, the control unit moves the piston within the cylinder chamber so that the first pressure sensor continues to read the desired pressure, such as 1.5 psig. At the same time, the control unit opens the fourth pneumatic valve, opens the second source valve, and causes the air pump to generate a negative pressure in the second pneumatic pump chamber, thereby pulling the flexible membrane of the second fluid pump chamber into the second pneumatic pump chamber and pulling fresh or used PD fluid into the second fluid pump chamber.

[0046] Eventually, the first flexible membrane cannot collapse further, causing the first pressure sensor reading to reach a peak, at which point the control unit stops the pump-out translation of the piston head and closes the first destination fluid valve. Alternatively or additionally, the detection that the flexible membrane cannot collapse further can be determined by the control unit detecting that the linear actuator and / or piston head do not move while maintaining the desired pressure (e.g., 1.5 psig). In any case, after stopping the pump-out translation, the first pneumatic valve remains open to allow the positive pressure that has been maintained at the desired pressure to balance between the cylinder chamber and the first pneumatic pump chamber, and the positive pressure can be read by the first pressure sensor. The piston head is now in the final piston head position within the cylinder chamber. The volume difference of the cylinder at the known cross-sectional area between the final piston head position and the initial piston head position is the volume of fresh or used PD fluid pumped to the destination due to the same pressure at the initial piston head position and the final piston head position (e.g., 1.5 psig, which is the desired pump-to-patient pressure). For fluid extraction of the second fluid pump chamber, the control unit can again monitor the speed of the air pump. When the speed of the air pump begins to decrease beyond a set threshold, the control unit determines that the flexible membrane of the second fluid pump chamber is fully pulled and expanded, and therefore the second fluid pump chamber is filled with fresh or used PD fluid, at which point the control unit stops the air pump and closes the second source fluid valve for the second fluid pump chamber.

[0047] The control unit then retracts the piston to the initial position and repeats the above process, but with the first fluid pump chamber filled with fresh or used PD fluid and the second fluid pump chamber pushing the fresh or used PD fluid to the destination. The control unit accumulates the known stroke volume and continues to perform the alternating pumping sequence just described until the desired or prescribed amount of fresh or used PD fluid is delivered to the destination.

[0048] Similar to the fourth main embodiment, the fifth main embodiment also uses an air pump that operates in cooperation with the cylinder to drive two pneumatic pump chambers and corresponding fluid pump chambers. In the fourth main embodiment, the cylinder is unidirectional with respect to fluid volume metering because only one side of the piston head in the cylinder is exposed to the first pressure sensor and the second pressure sensor. After each fluid pump chamber extraction / fluid pump chamber delivery sequence, the piston needs to be reset accordingly. In the fifth main embodiment, a fifth pneumatic line is added that extends from the first pneumatic line to the opposite side of the cylinder so that pneumatic access to the cylinder exists on both sides of the piston head. The fifth pneumatic valve is provided with a fifth pneumatic line. A sixth pneumatic valve is added as a second valve along the first pneumatic line, which allows the cylinder on this side of the piston head to be closed.

[0049] In a pumping sequence using the fifth main embodiment, the control unit can open the second pneumatic valve and the fifth pneumatic valve, open the second destination fluid valve, and move the piston head of the air cylinder in the first direction to deliver fresh or used PD fluid from the second fluid pump chamber to the desired destination. At the same time, the control unit opens the third pneumatic valve and the first source fluid valve so that the air pump can apply negative pressure to the flexible membrane of the first fluid pump chamber, thereby pulling fresh or used PD fluid into the first fluid pump chamber.

[0050] Eventually, the second flexible membrane cannot collapse further, causing the second pressure sensor reading to reach a peak, at which point the control unit stops the pump-out translation of the piston head and closes the second destination fluid valve. Alternatively or additionally, the detection that the flexible membrane cannot collapse further can be determined by the control unit detecting that the linear actuator and / or piston head do not move while maintaining the desired pressure (e.g., 1.5 psig). In any case, after stopping the pump-out translation, the second pneumatic valve and the fifth pneumatic valve remain open to allow the positive pressure that has been maintained at the desired pressure to balance between the cylinder chamber and the second pneumatic pump chamber, and the positive pressure can be read by the second pressure sensor. The volume difference of the cylinder at the known cross-sectional area between the initial piston head position and the final piston head position is the volume of fresh or used PD fluid pumped to the destination due to the same pressure at the initial piston head position and the final piston head position (e.g., 1.5 psig, which is the desired pump-to-patient pressure). For fluid extraction from the first fluid pump chamber, the control unit can again monitor the speed of the air pump. When the speed of the air pump begins to decrease beyond a set threshold, the control unit determines that the flexible membrane of the first fluid pump chamber is fully pulled and expanded, and therefore the first fluid pump chamber is filled with fresh or used PD fluid, at which point the control unit stops the air pump and closes the first source fluid valve for the first fluid pump chamber.

[0051] Next, the first fluid pump chamber and the second fluid pump chamber switch operation so that the second fluid pump chamber extracts fresh or used PD fluid while the first fluid pump chamber delivers fresh or used PD fluid. It is worth noting that there is no need to adjust the piston head to prepare the cylinder for the switching. Here, the control unit opens the first pneumatic valve and the sixth pneumatic valve, opens the first destination fluid valve, and moves the piston head of the cylinder in the second direction to deliver fresh or used PD fluid from the first fluid pump chamber to the desired destination. At the same time, the control unit opens the fourth pneumatic valve and the second source fluid valve so that the air pump can apply negative pressure to the flexible membrane of the second fluid pump chamber, thereby pulling fresh or used PD fluid into the second fluid pump chamber.

[0052] Eventually, the first flexible membrane cannot collapse further, causing the first pressure sensor reading to reach a peak, at which point the control unit stops the pump-out translation of the piston head and closes the first destination fluid valve. Alternatively or additionally, the detection that the flexible membrane cannot collapse further can be determined by the control unit detecting that the linear actuator and / or piston head do not move while maintaining the desired pressure (e.g., 1.5 psig). In any case, after stopping the pump-out translation, the first pneumatic valve and the sixth pneumatic valve remain open to allow the positive pressure that has been maintained at the desired pressure to balance between the cylinder chamber and the first pneumatic pump chamber, and the positive pressure can be read by the first pressure sensor. The volume difference of the cylinder at the known cross-sectional area between the initial piston head position and the final piston head position is the volume of fresh or used PD fluid pumped to the destination due to the same pressure at the initial piston head position and the final piston head position (e.g., 1.5 psig, which is the desired pump-to-patient pressure). For fluid extraction of the second fluid pump chamber, the control unit can again monitor the speed of the air pump. When the speed of the air pump begins to decrease beyond a set threshold, the control unit determines that the flexible membrane of the second fluid pump chamber is fully pulled and expanded, and therefore the second fluid pump chamber is filled with fresh or used PD fluid, at which point the control unit stops the air pump and closes the second source fluid valve for the second fluid pump chamber.

[0053] The control unit accumulates the known stroke volume and continues to perform the alternating pumping sequence just described until the desired or prescribed amount of fresh or used PD fluid is delivered to the destination. For any of the above-described primary embodiments, it should be understood that for fresh or used PD fluid destinations not involving a patient (e.g., a heater bag or drain), the delivery pressure can be higher, for example, up to 8 psig. It is also contemplated that for any of the primary embodiments, while the cylinder or pump is removing used PD fluid from the patient, the control unit monitors the associated first or second pressure sensor so that the patient drain negative pressure limit, for example -1.5 psig, is not met or exceeded.

[0054] It should be appreciated that drift effects in the pneumatic pressure sensors used in the above described embodiments are offset because the important aspect of the above described cylinder sequence is that the initial and final pressures associated with fresh or spent PD fluid delivery are equal, not that the pressures are accurate from an absolute perspective (except to the patient pressure limit). Also, because the system is pressure controlled, the linear actuators do not have to be highly accurate.

[0055] According to 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 peritoneal dialysis system comprises: a pneumatic pump chamber; a cylinder; a piston, the piston comprising a piston head slidably sealed within the cylinder, the piston head separating a first cylinder chamber from a second cylinder chamber; a linear actuator, the linear actuator being mechanically connected to the piston; a first pneumatic line, the first pneumatic line extending between the first cylinder chamber and the pneumatic pump chamber; a second pneumatic line, the second pneumatic line extending between the second cylinder chamber and the pneumatic pump chamber; a first pneumatic valve, the first pneumatic valve being positioned along the first pneumatic line; a second pneumatic valve, the second pneumatic valve being positioned along the second pneumatic line; a pressure sensor, the pressure sensor being positioned and arranged to measure a pressure in the pneumatic pump chamber; a fluid pump chamber, the fluid pump chamber being operably connected to the pneumatic pump chamber; a source fluid valve; a destination fluid valve. body valve; and a control unit, the control unit being configured to (i) open the second pneumatic valve and the source fluid valve, and cause the linear actuator to move the piston head into the first cylinder chamber so as to generate negative pneumatic pressure in the second cylinder chamber and the pneumatic pump chamber to pull the source fluid into the fluid pump chamber, and (ii) close the second pneumatic valve and the source fluid valve, open the first pneumatic valve and the destination fluid valve, and cause the linear actuator to move the piston head further into the first cylinder chamber so as to push the source fluid through the destination fluid valve, and wherein the control unit uses the output from the pressure sensor to control the linear actuator so that the final pressure for (ii) is at least substantially equal to the initial pressure for (ii), so that the volume of the space corresponding to the movement of the piston head in the cylinder during (ii) is equal to the volume of the source fluid delivered from the fluid pump chamber during (ii).

[0056] In a second aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the source fluid valve is for a PD fluid supply container, a heated container, or a patient line.

[0057] In a third aspect of the present disclosure which may be combined with any other aspect or portion thereof, the destination fluid valve is for heating a container, draining a container, or a patient line.

[0058] In a fourth aspect of the present disclosure, which may be combined with any other aspect or part thereof, the volume of the space corresponding to the movement of the piston head in the cylinder varies with the distance the piston head moves in the cylinder and the cross-sectional area of ​​the inner diameter of the cylinder.

[0059] In a fifth aspect of the present disclosure which may be combined with any other aspect or part thereof, the control unit is configured to determine a volume of source fluid delivered from the fluid pump chamber during (ii) when both the source fluid valve and the destination fluid valve are closed.

[0060] In a sixth aspect of the present disclosure, which may be combined with any other aspect or part thereof, the control unit is further configured to: when the first pneumatic valve and the destination fluid valve are closed, (iii) open the second pneumatic valve and the source fluid valve to allow the negative pneumatic pressure in the second cylinder chamber generated during at least one of (i) or (ii) to reach the pneumatic pump chamber, thereby pulling the source fluid into the fluid pump chamber.

[0061] In a seventh aspect of the present disclosure, which may be combined with any other aspect or part thereof, the control unit is further configured to: when the first pneumatic valve, the source fluid valve and the destination fluid valve are closed and the second pneumatic valve is closed, (iv) cause the linear actuator to move the piston head into the second cylinder chamber so as to generate at least substantially zero pressure in the first cylinder chamber and the second cylinder chamber.

[0062] In the eighth aspect of the present disclosure, which can be combined with any other aspect or part thereof, the control unit is further configured to: (v) open the second pneumatic valve and the destination fluid valve, and cause the linear actuator to move the piston head into the second cylinder chamber so as to push the source fluid through the destination fluid valve, and wherein the control unit uses the output from the pressure sensor to control the linear actuator so that the final pressure used for (v) is at least substantially equal to the initial pressure used for (v), so that the volume of the space corresponding to the movement of the piston head in the cylinder during (v) is equal to the volume of the source fluid delivered from the fluid pump chamber during (v).

[0063] In a ninth aspect of the present disclosure, which may be combined with any other aspect or part thereof, the control unit is further configured to: when the second pneumatic valve and the destination fluid valve are closed, (vi) open the first pneumatic valve and the source fluid valve to allow the negative pneumatic pressure generated in the first cylinder chamber during (v) to reach the pneumatic pump chamber, thereby pulling the source fluid into the fluid pump chamber.

[0064] In a tenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a peritoneal dialysis system comprises: a pneumatic pump chamber; a cylinder; a piston, the piston comprising a piston head slidably sealed within the cylinder; a linear actuator, the linear actuator being mechanically connected to the piston; an air pump; a first pneumatic line, the first pneumatic line extending between the cylinder and the pneumatic pump chamber; a second pneumatic line, the second pneumatic line extending between the air pump and the pneumatic pump chamber; a first pneumatic valve, the first pneumatic valve being positioned along the first pneumatic line; a second pneumatic valve, the second pneumatic valve being positioned along the second pneumatic line; a pressure sensor, the pressure sensor being positioned and arranged to measure a pressure in the pneumatic pump chamber; a fluid pump chamber, the fluid pump chamber being operably connected to the pneumatic pump chamber; a source fluid valve; a destination fluid valve; and a control unit, the control unit being configured to: (i) cause the second pneumatic valve and the source fluid valve to actuate the second pneumatic valve; The invention relates to a method of controlling the pneumatic pump to: (i) open the body valve and cause the air pump to generate a negative pneumatic pressure in the pneumatic pump chamber, thereby pulling the source fluid into the fluid pump chamber, (ii) close the source fluid valve and, with the second pneumatic valve open, cause the air pump to generate a desired positive pressure in the pneumatic pump chamber as measured by the pressure sensor, and (iii) close the second pneumatic valve, open the first pneumatic valve and the destination fluid valve, and cause the linear actuator to move the piston head within the cylinder so as to push the source fluid through the destination fluid valve, and wherein the control unit uses the output from the pressure sensor to control the linear actuator so that the final pressure for (iii) is at least substantially equal to the initial pressure for (iii) so that the volume of the space corresponding to the movement of the piston head within the cylinder during (iii) is equal to the volume of the source fluid delivered from the fluid pump chamber during (iii).

[0065] In an eleventh aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the source fluid valve is for a PD fluid supply container, a heating container, or a patient line.

[0066] In a twelfth aspect of the present disclosure which may be combined with any other aspect or portion thereof, the destination fluid valve is used to heat a container, drain a container, or a patient line.

[0067] In the thirteenth aspect of the present disclosure which may be combined with any other aspect or part thereof, the volume of the space corresponding to the movement of the piston head in the cylinder varies with the distance the piston head moves in the cylinder and the cross-sectional area of ​​the inner diameter of the cylinder.

[0068] In a fourteenth aspect of the present disclosure that may be combined with any other aspect or portion thereof, during (i), the first pneumatic valve is opened.

[0069] In a fifteenth aspect of the present disclosure that can be combined with any other aspect or part thereof, the control unit is further configured to, when the first pneumatic valve and the source fluid valve are opened, (iv) cause the linear actuator to move the piston head in the opposite direction within the cylinder, thereby pulling the source fluid into the fluid pump chamber.

[0070] In a sixteenth aspect of the present disclosure that may be combined with any other aspect or portion thereof, during (iv), the first pneumatic valve is opened and the air pump is actuated to help pull source fluid into the fluid pump chamber.

[0071] In a seventeenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a peritoneal dialysis system comprises: a first pneumatic pump chamber; a second pneumatic pump chamber; a cylinder; a piston, the piston comprising a piston head slidably sealed within the cylinder; a linear actuator, the linear actuator being in mechanical communication with the piston; an air pump; a first pneumatic line, the first pneumatic line extending between the cylinder and the first pneumatic pump chamber; a second pneumatic line, the second pneumatic line extending between the cylinder and the second pneumatic pump chamber; a third pneumatic line, the third pneumatic line extending between the cylinder and the second pneumatic pump chamber; and a third pneumatic line extending between the cylinder and the second pneumatic pump chamber. a third pneumatic line extending between the air pump and the first pneumatic pump chamber; a fourth pneumatic line extending between the air pump and the second pneumatic pump chamber; a first pneumatic valve, the first pneumatic valve being positioned along the first pneumatic line; a second pneumatic valve, the second pneumatic valve being positioned along the second pneumatic line; a third pneumatic valve, the third pneumatic valve being positioned along the third pneumatic line; a fourth pneumatic valve, the fourth pneumatic valve being positioned along the fourth pneumatic line; a first pressure sensor, the first pressure sensor being positioned and arranged a first pressure sensor positioned and arranged to measure the pressure in the first pneumatic pump chamber; a second pressure sensor positioned and arranged to measure the pressure in the second pneumatic pump chamber; a first fluid pump chamber, the first fluid pump chamber being operably connected to the first pneumatic pump chamber; a first source fluid valve, the first source fluid valve being used for the first pump chamber; a first destination fluid valve, the first destination fluid valve being used for the first pump chamber; a second fluid pump chamber, the second fluid pump chamber being operably connected to the first pneumatic pump chamber; a second source fluid valve, the second source fluid valve being used for the second pump chamber; a second destination fluid valve, the second destination fluid valve being used for the second pump chamber; and a control unit configured to generate negative and positive pneumatic pressures in the first and second pneumatic pump chambers using the air pump, and to actuate the linear actuator to move the piston head within the cylinder while making the initial positive and final positive pneumatic pressures equal so as to meter a determinable volume of source fluid through the first and second destination fluid valves.

[0072] In an eighteenth aspect of the present disclosure that can be combined with any other aspect or part thereof, the control unit is configured to: (i) cause the air pump to generate a negative pneumatic pressure in the first pneumatic pump chamber to pull the source fluid into the first fluid pump chamber when the third pneumatic valve and the first source fluid valve are opened, (ii) cause the air pump to generate a desired positive pneumatic pressure measured by the first pressure sensor in the first pneumatic pump chamber when the third pneumatic valve is opened and the first source fluid valve is closed, and (iii) cause the linear actuator to move the piston head in the desired direction when the first pneumatic valve and the first destination fluid valve are opened. said cylinder so as to push the source fluid through the first destination fluid valve, and wherein the control unit uses the output from the first pressure sensor to control the linear actuator so that the final pressure for (iii) is at least substantially equal to the initial pressure for (iii), so that the volume of the space corresponding to the movement of the piston head in the cylinder during (iii) is equal to the volume of the source fluid delivered from the first fluid pump chamber during (iii), and when the fourth pneumatic valve and the second source fluid valve are opened, the air pump generates a negative pneumatic pressure in the second pneumatic pump chamber, thereby pulling the source fluid into the second fluid pump chamber.

[0073] In the nineteenth aspect of the present disclosure, which can be combined with any other aspect or part thereof, the control unit is further configured to, when the piston head moves to the retracted position, cause: (iv) the air pump to generate a desired positive pneumatic pressure measured by the first pressure sensor in the second pneumatic pump chamber when the fourth pneumatic valve is open and the second source fluid valve is closed, and (v) the linear actuator to move the piston head in the cylinder to push the source fluid through the second destination fluid valve when the second pneumatic valve and the second destination fluid valve are open, and wherein the control unit uses the output from the second pressure sensor to control the linear actuator so that the final pressure for (v) is at least substantially equal to the initial pressure for (v), so that the volume of the space corresponding to the movement of the piston head in the cylinder during (v) is equal to the volume of the source fluid delivered from the second fluid pump chamber during (v), and when the third pneumatic valve and the first source fluid valve are open, the air pump to generate a negative pneumatic pressure in the first pneumatic pump chamber to pull the source fluid into the first fluid pump chamber.

[0074] In a twentieth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a peritoneal dialysis system comprises: a first pneumatic pump chamber; a second pneumatic pump chamber; a cylinder; a piston, the piston comprising a piston head slidably sealed within the cylinder, the piston head separating the first cylinder chamber from the second cylinder chamber; a linear actuator, the linear actuator being mechanically connected to the piston; an air pump; a first pneumatic line extending between the second cylinder chamber and the first pneumatic pump chamber; a second pneumatic line extending between the second cylinder chamber and the second pneumatic pump chamber; a third pneumatic line extending between the second cylinder chamber and the second pneumatic pump chamber; and a third pneumatic line extending between the second cylinder chamber and the second pneumatic pump chamber. a fourth pneumatic line extending between the air pump and the first pneumatic pump chamber; a fifth pneumatic line extending between the first cylinder chamber and the first pneumatic line; a first pneumatic valve, the first pneumatic valve being positioned along the first pneumatic line; a second pneumatic valve, the second pneumatic valve being positioned along the second pneumatic line; a third pneumatic valve, the third pneumatic valve being positioned along the third pneumatic line; a fourth pneumatic valve, the fourth pneumatic valve being positioned along the fourth pneumatic line; a fifth pneumatic valve, the fifth pneumatic valve being positioned along the fifth pneumatic line; a first pneumatic valve, the first pneumatic valve being positioned adjacent to the second cylinder chamber; a first pressure sensor, the first pressure sensor being positioned and arranged to measure the pressure in the first pneumatic pump chamber; a second pressure sensor, the second pressure sensor being positioned and arranged to measure the pressure in the second pneumatic pump chamber; a first fluid pump chamber, the first fluid pump chamber being operably connected to the first pneumatic pump chamber; a first source fluid valve, the first source fluid valve being used for the first pump chamber; a first destination fluid valve, the first destination fluid valve being used for the first pump chamber; a second fluid pump chamber, the second fluid pump chamber being connected to the first pneumatic pump chamber chamber is operably connected; a second source fluid valve, which is used for the second pump chamber; a second destination fluid valve, which is used for the second pump chamber; and a control unit, which is configured to use the air pump to generate negative pneumatic pressure and positive pneumatic pressure in the first pneumatic pump chamber and the second pneumatic pump chamber, and actuate the linear actuator to move the piston head in the first cylinder chamber and the second cylinder chamber while making the initial positive pneumatic pressure and the final positive pneumatic pressure equal to each other so as to meter a determinable volume of source fluid through the first destination fluid valve and the second destination fluid valve.

[0075] In the twenty-first aspect of the present disclosure, which can be combined with any other aspect or part thereof, the control unit is configured to cause: (i) when the third pneumatic valve and the first source fluid valve are opened, the air pump generates a negative pneumatic pressure in the first pneumatic pump chamber to pull the source fluid into the first fluid pump chamber, and when the second pneumatic valve, the fifth pneumatic valve and the second destination fluid valve are opened, the linear actuator moves the piston head toward the first cylinder chamber so as to push the source fluid through the second destination fluid valve, and wherein the control unit uses the output from the second pressure sensor to control the linear actuator so that the final pressure used for (i) is at least substantially equal to the initial pressure used for (i), so that the volume of the space corresponding to the movement of the piston head toward the first cylinder chamber during (i) is equal to the volume of the source fluid delivered from the second fluid pump chamber during (i).

[0076] In the twenty-second aspect of the present disclosure, which can be combined with any other aspect or part thereof, the control unit is further configured to: (ii) when the fourth pneumatic valve and the second source fluid valve are opened, the air pump generates a negative pneumatic pressure in the second pneumatic pump chamber, thereby pulling the source fluid into the second fluid pump chamber, and when the first pneumatic valve, the sixth pneumatic valve and the first destination fluid valve are opened, the linear actuator moves the piston head toward the second cylinder chamber so as to push the source fluid through the first destination fluid valve, and wherein the control unit uses the output from the first pressure sensor to control the linear actuator so that the final pressure used for (ii) is at least substantially equal to the initial pressure used for (ii), so that the volume of the space corresponding to the movement of the piston head toward the second cylinder chamber during (ii) is equal to the volume of the source fluid delivered from the second fluid pump chamber during (ii).

[0077] In the twenty-third aspect which may be combined with any other aspect or part thereof, Figures 1 to 28 Any features, functions and alternatives described in any one or more of the figures may be combined with Figures 1 to 28 Any combination of features, functions and alternatives described in any other figure in the.

[0078]

[0013] It is therefore an advantage of the present disclosure to provide a relatively volumetrically accurate automated peritoneal dialysis ("PD") machine.

[0079] Another advantage of the present disclosure is to provide a PD machine that achieves relatively precise pressure control.

[0080] Another advantage of the present disclosure is to provide a relatively quiet PD machine.

[0081] Yet another advantage of the present disclosure is to provide a PD machine that is accurate regardless of how the pressure sensor drifts over time, temperature, humidity, etc.

[0082] Yet another advantage of the present disclosure is to provide a PD machine that eliminates the reliance on absolute pressure sensing for volumetric accuracy.

[0083] Yet another advantage of the present disclosure is to provide a PD system that uses low-cost and simple machinery and low-cost and simple disposables.

[0084] 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. In addition, it should be noted that the language used in this specification has been selected primarily for readability and instructional purposes, and not for limiting the scope of the disclosed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 is a schematic elevational view of one embodiment of a peritoneal dialysis ("PD") system of the present disclosure.

[0086] Figure 2 and Figure 3 is a schematic diagram of a first main embodiment of the PD system of the present disclosure, which uses a pneumatic cylinder.

[0087] Figures 4 to 13 is a schematic diagram of a second main embodiment of the PD system of the present disclosure, which PD system uses a pneumatic cylinder.

[0088] Figures 14 to 20 is a schematic diagram of a third main embodiment of the PD system of the present disclosure, which PD system uses an air cylinder and an air pump.

[0089] Figure 21 to Figure 24 is a schematic diagram of a fourth main embodiment of the PD system of the present disclosure, which PD system uses an air cylinder and an air pump.

[0090] Figure 25 to Figure 28 is a schematic diagram of a fifth main embodiment of the PD system of the present disclosure, which PD system uses an air cylinder and an air pump. DETAILED DESCRIPTION

[0091] Referring now to the drawings, and in particular to Figure 1, an automated peritoneal dialysis ("PD") system 10 includes a PD machine or cycler 20 that operates with a disposable kit 110. The disposable kit 110 includes or defines at least one fluid pump chamber 112a, 112b, which may include two flexible sheets that are welded together to form, for example, a circular chamber that can be expanded in a spherical manner. At least one fluid pump chamber 112a, 112b may alternatively include a single flexible sheet welded to a rigid hemispherical pump housing. All welds discussed herein may be achieved by heat sealing, ultrasonic sealing, or solvent bonding.

[0092] The disposable kit 110 also includes or defines a plurality of fresh and used PD fluid lines, such as a heater line 114a, a drain line 114b, a PD fluid supply line 114c, 114d, 114e, a patient line 114f, and a fluid pump chamber line 114g. The fresh and used PD fluid lines may be formed via tubing, via a welded path between two flexible sheets, or via a molded path in a rigid box.

[0093] The disposable kit 110 also includes a plurality of PD fluid containers, such as a heating container 116a, a drain container 116b, and PD fluid supply containers 116c, 116d, and 116e. The heating container 116a in the illustrated embodiment is located on a heating tray at the top of the housing 22 of the PD machine or cycler 20. A batch heater 24, such as a resistive heater, is provided at the top of the PD machine or cycler 20 under the control of the control unit 100. In an alternative embodiment, an initial supply container of the supply containers 116c, 116d, and 116e is placed on the heating tray and then, once emptied, is used as a heating container for the remainder of the processing. In another alternative embodiment, the heater 24 is instead an in-line heater, such as one that operates with the patient line 114f, such that the heating container 116a can be eliminated. In any case, the control unit 100 is programmed to cause the heater 24 to heat the fresh PD fluid to patient temperature, such as 37°C.

[0094] Any desired number and size of PD fluid supply containers 116c, 116d, 116e may be provided and may hold PD fluids of the same or different dextrose or glucose levels. One of the PD fluid supply containers 116c, 116d, 116e may be a last fill container and contain a different PD formulation, such as icodextrin. Additionally, drain line 114b may alternatively lead to a house drain, such as a toilet or bathtub, in which case drain container 116b is not required. Any of containers 116a-116a may be formed as a flexible container or bag.

[0095] The disposable kit 110 in the illustrated embodiment also includes a plurality of fluid valve seats, such as a heater valve seat 118a, an exhaust valve seat 118b, PD fluid supply valve seats 118c, 118d, 118e, a patient valve seat 118f, and a fluid pump chamber valve seat 118g. The fluid valve seats 118a to 118g may be tubing locations formed by welding two flexible sheets or by molding in a rigid box. The fluid valve seats 118a to 118g are connected to the valve actuator ( Figure 1 The valve actuator may be a magnetically actuated solenoid pinch valve actuator, an electric pinch valve, or a pneumatically actuated valve actuator (not shown).

[0096] In system 10, and as described in detail below, supply containers 116c, 116d, and 116e are fresh PD fluid sources (("FS"), although one supply container may be a fresh PD fluid destination if used as a heating container). Drain container 116b is a spent PD fluid destination ("FD"). Heating container 116a is both a fresh PD fluid source ("FS") and a fresh PD fluid destination ("FD"). Patient line 114f (PATIENT) is both a spent PD fluid source ("FS") and a fresh PD fluid destination ("FD").

[0097] In system 10, and as described in detail below, PD fluid supply valve seats 118c, 118d, and 118e are source fluid valves (("SV"), although they may be destination fluid valves ("DV") if used as heater valves. Discharge valve seat 118b is a destination fluid valve ("DV"). Heater valve seat 118a and patient valve seat are both source fluid valves ("SV") and destination fluid valves ("DV"). Fluid pump chamber valve seat 118g allows fluid pump chambers 112a, 112b to alternately draw in or pump out fresh or used PD fluid depending on the current pumping sequence, such that flow to a desired destination is relatively continuous.

[0098] Any rigid components of the disposable set 110 can be made of plastic, such as polyvinyl chloride ("PVC"), polyethylene ("PE"), polyurethane ("PU"), or polycarbonate ("PC"). Any flexible components of the disposable set 110 (such as the membrane or diaphragm discussed herein, tubing, and containers) can be made of medically safe materials, such as one or more plastics, such as PVC, PE, PU, ​​or other suitable non-PVC polymers. The rigid pump housing 22, the cylinder discussed herein and its associated components, and the pneumatic tubing discussed herein are reusable in one embodiment and can be made of plastic (such as polyvinyl chloride ("PVC"), polyethylene ("PE"), or polyurethane ("PU")) or metal (such as stainless steel or aluminum), and combinations thereof.

[0099] First Main Embodiment

[0100] In such Figure 2 and Figure 3 In the first main embodiment of the system 10 shown, a cylinder 30 is provided. The cylinder 30 is located between a first pneumatic pump chamber 70a and a second pneumatic pump chamber 70b, which operate with the fluid pump chambers 112a, 112b of the disposable kit 110, respectively. A piston 32 is located within the cylinder 30, wherein the piston 32 includes a piston shaft 34 and a piston head 36 that divides the cylinder 30 into a first cylinder chamber 30a and a second cylinder chamber 30b. The piston shaft 34 and the piston head 36 in the illustrated embodiment are driven by a linear actuator 40. The linear actuator 40 may include a motor, such as a stepper motor that drives a rotation-to-translation conversion device (such as a lead screw or a ball screw). The linear actuator 40 may alternatively be pneumatically driven. In any case, the piston shaft 34 is connected to the linear actuator 40 outside the cylinder 30 for translating the piston shaft and the piston head 36 within the cylinder.

[0101] The first pneumatic line 42a extends from the first cylinder chamber 30a to the first pneumatic pump chamber 70a. The second pneumatic line 42b extends from the second cylinder chamber 30b to the second pneumatic pump chamber 70b. The first pressure sensor 44a is positioned to read the air pressure in the first pneumatic line 42a, the first pneumatic pump chamber 70a, and the first cylinder chamber 30a. The second pressure sensor 44b is positioned to read the air pressure in the second pneumatic line 42b, the second pneumatic pump chamber 70b, and the second cylinder chamber 30b.

[0102] A first exhaust line 46a and an associated first exhaust valve 48a are optionally placed in fluid communication with the first cylinder chamber 30a. A second exhaust line 46b and an associated second exhaust valve 48b are optionally placed in fluid communication with the second cylinder chamber 30b.

[0103] All fluid valve actuators (driving fluid valve seats 118a to 118g), motors or other drivers for linear actuators 40, PD fluid heaters 24, and other controllable electrical devices are under the control of a control unit 100, which includes at least one processor 102, at least one memory 104, and a video controller 106 for controlling a user interface 108 (which may be coupled to the circulator 20 as shown or may be a wireless user interface). The control unit may also be configured to receive signals from all sensors, such as all pneumatic pressure sensors (e.g., 44a, 44b), fluid pressure sensors (if provided), motor encoders (or other position determination mechanisms for linear actuators 40), and any temperature sensors associated with heaters 24. The control unit 100 may also include a transceiver (not shown), and a wired or wireless connection to a network (e.g., the Internet) for sending treatment data to a doctor's or physician's server that interacts with the doctor's or physician's computer, and receiving prescription instructions from the server. The user interface 108 may include a display screen that operates with a touch screen and / or one or more electromechanical buttons (such as membrane switches). The user interface 108 may also include one or more speakers for outputting alarms, warnings, and / or voice guidance commands.

[0104] To achieve the desired fresh or spent PD fluid pumping sequence described herein, the control unit 100 can feed the difference between the command pressure and the pressure measured at the associated pressure sensor (e.g., pressure sensor 44a, 44b) into a control algorithm (e.g., a proportional, integral, derivative ("PID") algorithm) that attempts to reduce the difference between the command pressure and the measured pressure to zero, and this produces an output to an electronic motor drive in one example of the linear actuator 40. In each of the main embodiments of the system 10 described herein, the control algorithm analysis is performed at some periodic frequency. The control unit 100 is programmed to run all of the pumping sequences discussed herein, including the sequence of the first main embodiment discussed next.

[0105] like Figure 2 and Figure 3As shown, the PD machine or cycler 20 operates a disposable kit 110. Among other items, the disposable kit 110 includes a first fluid pump chamber 112a and a second fluid pump chamber 112b that operate together with the first pneumatic pump chamber 70a and the second pneumatic pump chamber 70b, respectively. When the piston head 36 moves so as to generate a negative pneumatic pressure in the first cylinder chamber 30a or the second cylinder chamber 30b, a corresponding negative pressure is generated in the corresponding first pneumatic pump chamber 70a or the second pneumatic pump chamber 70b. The negative pressure generated in the first pneumatic pump chamber 70a or the second pneumatic pump chamber 70b then pulls the flexible membrane of the corresponding first fluid pump chamber 112a or the second fluid pump chamber 112b into the first pneumatic pump chamber 70a or the second pneumatic pump chamber 70b, so that the fluid pump chamber is filled with fresh or used PD fluid. When the piston head 36 moves to generate positive pneumatic pressure in the first cylinder chamber 30a or the second cylinder chamber 30b, a corresponding positive pressure is generated in the corresponding first pneumatic pump chamber 70a or the second pneumatic pump chamber 70b. The positive pressure generated in the first pneumatic pump chamber 70a or the second pneumatic pump chamber 70b then pushes the flexible membrane of the corresponding first fluid pump chamber 112a or the second fluid pump chamber 112b, causing the fluid pump chambers 112a, 112b to close and discharge fresh or used PD fluid.

[0106] The control unit 100 in the first main embodiment causes the piston shaft 34 to translate the piston head 36 back and forth within the cylinder 30 such that in one half-stroke (i), the first fluid pump chamber 112a is filled with fresh or used PD fluid while the second fluid pump chamber 112b is discharged from fresh or used PD fluid. In the second half-stroke (ii), the second pump chamber 112b is filled with fresh or used PD fluid while the first fluid pump chamber 112a is discharged from fresh or used PD fluid. The control unit 100 causes the piston head 36 to translate back and forth in the above manner until a desired or specified volume of fresh or used PD fluid is delivered from the desired PD fluid source to the desired PD fluid destination. Fluid valves are provided and sequentially actuated by the control unit 100 to access the desired fluid source and the desired fluid destination. The fluid valves may again include magnetically actuated solenoid valves, electric pinch valves, or pneumatically actuated valves.

[0107] In the first main embodiment, and in situations where patient pumping is occurring such that pressure control is important, the control unit 100 monitors the outputs from the first pressure sensor 44a and the second pressure sensor 44b while the piston head 36 is translating back and forth. The control unit 100 controls the speed of the back and forth translation so that a desired safe negative or positive fluid pumping pressure (e.g., -1.5 psig (pounds force per square inch), 1.5 psig to 3.0 psig) is not exceeded.

[0108] In the first main embodiment, the amount of fresh or used PD fluid delivered to the destination is determined by maintaining a constant pressure before and after the movement of the piston head 36, which offsets the compressibility effect of the air in the cylinder 30. Since the pressure after the movement (P2) is equal to the pressure before the movement (P1), the volume of air in the cylinder 30 remains constant. Therefore, the volume displaced by the piston head 36 is equal to the volume of fluid delivered.

[0109] Second main embodiment

[0110] Figures 4 to 13 A second main embodiment of the system 10 is shown, in which only cylinders 30 are provided as before, but in which the cylinders are dedicated to a single pneumatic pump chamber 70a, 70b / fluid pump chamber 112a, 112b pair. Two pneumatic pump chamber / fluid pump chamber pairs may be provided (pair 70a, 112a is shown by way of example), with each pair having its own dedicated cylinder 30. The structure of the cylinder 30 is the same as in the first main embodiment, including a piston 32 having a piston head 36 and a piston shaft 34 driven by a linear actuator 40. Optional exhaust lines 46a, 46b and pneumatic exhaust valves 48a, 48b may be in pneumatic communication with the first and second cylinder chambers 30a, 30b of each cylinder 30.

[0111] In the second main embodiment, the first and second pneumatic lines 56a, 56b extend from the first and second cylinder chambers 30a, 30b, respectively, to the same pneumatic pump chamber 70a. A first and second pneumatic valves 58a, 58b under the control of the control unit 100 are disposed along the first and second pneumatic lines 56a, 56b. One or more pressure sensors 44a are disposed along a common portion of the first and second pneumatic lines 56a, 56b or along each of the first and second pneumatic lines. The fluid pump chambers 112a, 112b are again provided as part of the disposable kit 110, wherein the fluid pump chamber 112a pumps fresh or used PD fluid from a desired PD fluid source FS to a desired destination FD, as determined by the sequence of the fluid source valve SV and the fluid destination valve DV.

[0112] Figure 4 It is shown that the control unit 100 in the second main embodiment causes the piston shaft 34 to translate the piston head 36 toward the first cylinder chamber 30a, thereby generating a positive pressure in the first cylinder chamber 30a and a negative pressure in the second cylinder chamber 30b. The control unit 100 also causes the source fluid valve SV and the second pneumatic valve 58b to open, thereby allowing the negative pressure to reach the pneumatic pump chamber 70a, and causing the flexible membrane of the fluid pump chamber 112a to be pulled into the pneumatic pump chamber 70a and filled with fresh or used PD fluid.

[0113] Figure 5As shown, the control unit 100 next closes the source fluid valve SV and the second pneumatic valve 58b and opens the first pneumatic valve 58a so that the pressure sensor 44a can read the positive pressure in the first cylinder chamber 30a. The control unit 100 also moves the piston 32 into the first cylinder chamber 30a so that the positive pressure in the pneumatic pump chamber 70a reads the desired pressure, such as 1.5 psig, to pump fresh or used PD fluid to the desired destination FD. At the end of this movement, the piston head 36 is in the initial piston head position.

[0114] Figure 6 As shown, the control unit 100 maintains the first pneumatic valve 58a in an open state and opens the destination fluid valve DV. The desired positive pressure built up in the pneumatic pump chamber 70a causes the flexible membrane of the fluid pump chamber 112a to collapse and push the fresh or used PD fluid to the desired destination FD. As the positive pressure dissipates, the control unit 100 moves the piston 32 further into the first cylinder chamber 30a so that the pressure sensor 44a continues to read the desired pressure, for example, 1.5 psig.

[0115] Figure 7 It is shown that eventually, the flexible membrane cannot collapse further, causing the reading at the pressure sensor 44a to reach a peak, at which point the control unit 100 stops the pump-out translation of the piston head 36 and closes the destination fluid valve DV. Alternatively or additionally, the detection that the flexible membrane cannot collapse further can be determined by the control unit 100 detecting that the linear actuator 40 and / or the piston head 36 do not move while maintaining the desired pressure (e.g., 1.5 psig). In any case, after stopping the pump-out translation, the first pneumatic valve 58a remains open to allow the positive pressure that has been maintained at the desired pressure to balance between the first cylinder chamber 30a and the pneumatic pump chamber 70a, and this positive pressure can be read by the pressure sensor 44a. The piston head 36 is now in the final piston head position. The volume difference of the cylinder 30 at a known cross-sectional area between the final piston head position and the initial piston head position is the volume of fresh or spent PD fluid pumped to the desired destination FD as determined by the control unit 100 due to the same pressure at the initial and final piston head positions (e.g., 1.5 psig, which is, for example, the desired pump-to-patient pressure). That is, the volume of space corresponding to the movement of the piston head 36 within the cylinder 30 varies with the distance the piston head moves within the cylinder and the cross-sectional area of ​​the cylinder inner diameter (which is substantially the same as the circular area of ​​the piston head 36).

[0116] Figure 8It is shown that, next, with the second cylinder chamber 30b still under negative pressure (which is not critical if pulled from a non-patient source), the control unit 100 causes the source fluid valve SV and the second pneumatic valve 58b to open, thereby allowing negative pressure to reach the pneumatic pump chamber 70a and causing the flexible membrane of the fluid pump chamber 112a to be pulled into the pneumatic pump chamber 70a and filled with fresh or used PD fluid.

[0117] Fig. 9 It is shown that, next, the control unit 100 causes the source fluid valve SV to close, but allows the second pneumatic valve 58b to remain open, so that the pneumatic pump chamber 70a and the second cylinder chamber 30b remain exposed to the pressure sensor 44a. The control unit 100 causes the piston 32 to translate into the second cylinder chamber 30b until the pressure sensor 44a reads zero psig. The pressure in the first cylinder chamber 30a should also be close to zero psig.

[0118] Fig.10 It is shown that, next, with the source fluid valve SV and the destination fluid valve DV closed, the first pneumatic valve 58a closed and the second pneumatic valve 58b opened so that the pressure sensor 44a can read the positive pressure in the second cylinder chamber 30b, the control unit 100 moves the piston 32 into the second cylinder chamber 30b so that the positive pressure in the pneumatic pump chamber 70a reads the desired pressure again, such as 1.5psig, to pump fresh or used PD fluid to the desired destination FD. At the end of this movement, the piston head 36 is again in the initial piston head position.

[0119] Fig.11 Next, the control unit 100 maintains the second pneumatic valve 58b in an open state and causes the destination fluid valve DV to open. The desired positive pressure built up in the pneumatic pump chamber 70a again forces the flexible membrane of the fluid pump chamber 112a to collapse and push the fresh or used PD fluid to the desired destination FD. As the positive pressure dissipates, the control unit 100 moves the piston 32 further into the second cylinder chamber 30b so that the pressure sensor 44a continues to read the desired pressure, for example, 1.5 psig.

[0120] Fig.12It is shown that eventually, the flexible membrane cannot collapse further, causing the reading at the pressure sensor 44a to reach a peak, at which point the control unit 100 stops the pump-out translation of the piston head 36 and closes the destination fluid valve DV. Alternatively or additionally, the detection that the flexible membrane cannot collapse further can be determined by the control unit 100 detecting that the linear actuator 40 and / or the piston head 36 do not move while maintaining the desired pressure (e.g., 1.5 psig). In any case, after the pump-out translation is stopped, the second pneumatic valve 58b remains open to allow the positive pressure that has been maintained at the desired pressure to balance between the first cylinder chamber 30a and the pneumatic pump chamber 70a, and this positive pressure can be read by the pressure sensor 44a. The piston head 36 is now in the final piston head position. The difference in volume of the cylinder 30 at a known cross-sectional area between the final piston head position and the initial piston head position is again the volume of fresh or used PD fluid pumped to the desired destination DV calculated by the control unit 100 due to the fact that the pressures at the initial and final piston head positions are the same (e.g., 1.5 psig, which is the desired pump-to-patient pressure).

[0121] Fig.13 It is shown that, with the first cylinder chamber 30a still under negative pressure (this is not critical if pulled from a non-patient source), the control unit 100 causes the source fluid valve SV and the first pneumatic valve 58a to open, thereby allowing negative pressure to reach the pneumatic pump chamber 70a and causing the flexible membrane of the fluid pump chamber 112a to be pulled into the pneumatic pump chamber 70a and filled with fresh or used PD fluid. The above process is repeated until the desired amount of fresh or used PD fluid is delivered to the desired destination FD. It should be understood that the above process can be used for any fresh or used PD fluid source FS and any fresh or used PD fluid destination FD described herein, and the aspiration pressure and delivery pressure and the volume of PD fluid delivered can be controlled and measured respectively.

[0122] Third main embodiment

[0123] Figures 14 to 20 A third main embodiment of the system 10 is shown, which introduces an air pump 80 operating in cooperation with the air cylinder 30. An air pump can generally transition more quickly between pumping positive pressures to pumping negative pressures, and vice versa. Moreover, even a small air pump can produce a wide range of pressures. These two advantages of the air pump 80 are combined with the ability of the air cylinder 30 to meter known volumes of fluid under pressure control as described herein.

[0124] The structure of the air cylinder 30 in the third main embodiment is substantially the same as that in the first and second main embodiments, and includes a piston head 36 and a piston shaft 34 driven by a linear actuator 40. Optional exhaust lines 46a, 46b and pneumatic exhaust valves 48a, 48b may be pneumatically connected to the first cylinder chamber 30a and the second cylinder chamber 30b of each air cylinder 30 provided, respectively. In the third main embodiment, only the first pneumatic line 56a extends from the air cylinder 30 to the pneumatic pump chamber 70a. A first pneumatic valve 58b under the control of the control unit 100 is provided along the first pneumatic line 56a. A second pneumatic line 56c extends from the air pump 80 and intersects the first pneumatic line 56a. A second pneumatic valve 58v under the control of the control unit 100 is provided along the second pneumatic line 58c. A pressure sensor 44a is provided along a common portion of the first pneumatic line 56a and the second pneumatic line 56c. Again, one or more fluid pump chambers 112a, 112b (chamber 112a is shown here by way of example only) are provided as part of the disposable kit 10, wherein the fluid pump chamber 112a pumps fresh or used PD fluid from a desired PD fluid source FS to a desired destination FD, as determined by a sequence of one or more fluid valves SV, DV.

[0125] Fig.14 It is shown that the control unit 100 in the third main embodiment initially causes the first pneumatic valve 58a and the second pneumatic valve 58c to open, causes the source fluid valve SV to open, and causes the air pump 80 to generate negative pressure in the pneumatic pump chamber 70a and the cylinder chamber 30a, thereby pulling the flexible membrane of the fluid pump chamber 112a into the pneumatic pump chamber 70a and pulling fresh or used PD fluid into the fluid pump chamber 112a. In an embodiment, the control unit 100 monitors the speed of the air pump 80 during the PD fluid extraction phase. When the speed of the air pump 80 begins to decrease beyond a set threshold, the control unit 100 determines that the flexible membrane is fully pulled and expanded, and therefore the fluid pump chamber 112a is filled with fresh or used PD fluid. The speed of the air pump 80 is directly related to the flow rate of the PD fluid (e.g., how quickly the PD fluid is loaded into the pump chamber 112a). Therefore, the control unit 100 can be programmed to monitor the speed of the air pump 80 to determine whether the membrane is fully stretched (e.g., stop the air pump after detecting a threshold speed change). In an embodiment, the control unit 100 also provides closed loop control to the air pump 80 so that a desired pressure is maintained. The control loop via the control unit 100 may be a proportional, integral, derivative ("PID") control loop that ensures that the pressure does not extend beyond a set threshold that could damage the membrane.

[0126] Fig.15 It is shown that after the fluid pump chamber 112a is completely filled with the PD fluid, the control unit 100 causes the source fluid valve SV and the first pneumatic valve 58a to close. Fig.16The control unit 100 is shown then causing the first and second pneumatic valves 58a, 58c to open and causing the air pump 80 to generate a desired positive pumping pressure (eg, 1.5 psig) in the pneumatic pump chamber 70a and the cylinder chamber 30a. Fig.17 It is shown that once the desired positive pumping pressure is reached, the control unit 100 causes the second pneumatic valve 58c to close, so that the air pump 80 is isolated and blocked. The piston head 36 of the piston 32 is here in an initial piston head position.

[0127] Fig.18 Next, the control unit 100 maintains the first pneumatic valve 58a in an open state and opens the destination fluid valve DV. The desired positive pressure built up in the pneumatic pump chamber 70a causes the flexible membrane of the fluid pump chamber 112a to collapse and push the fresh or used PD fluid to the desired fluid destination FD. As the positive pressure dissipates, the control unit 100 moves the piston 32 within the cylinder chamber 30a so that the pressure sensor 44a continues to read the desired pressure, for example, 1.5 psig.

[0128] Fig.19 It is shown that, eventually, the flexible membrane of the fluid pump chamber 112a cannot collapse further, causing the reading at the pressure sensor 44a to reach a peak, at which point the control unit 100 stops the pump-out translation of the piston head 36 and closes the destination fluid valve DV. Alternatively or additionally, the detection that the flexible membrane cannot collapse further can be determined by the control unit 100 detecting that the linear actuator 40 and / or the piston head 36 do not move while maintaining the desired pressure (e.g., 1.5 psig). In any case, after stopping the pump-out translation, the first pneumatic valve 58a remains open to allow the positive pressure that has been maintained at the desired pressure to balance between the cylinder chamber 30a and the pneumatic pump chamber 70a, and this positive pressure can be read by the pressure sensor 44a. The piston head 36 is now in the final piston head position. The volume difference of the cylinder 30 at a known cross-sectional area between the final piston head position and the initial piston head position is the volume of fresh PD fluid pumped to the desired fluid destination FD calculated by the control unit 100 because the pressures at the initial piston head position and the final piston head position are the same (e.g., 1.5 psig, which is the desired pump-to-patient pressure).

[0129] Fig. 20As shown, the control unit 100 then causes the first pneumatic valve 58a and the second pneumatic valve 58c to open, causes the source fluid valve SV to open, and causes the piston 32 to move in the opposite direction within the cylinder 30 to reposition the piston head 36 for the next pump-out stroke. The movement of the piston 32 creates a negative pressure within the cylinder chamber 30a and the pneumatic pump chamber 70a, which can be assisted by the air pump 80 to quickly achieve the desired PD fluid extraction pressure. The flexible membrane of the fluid pump chamber 112a is pulled into the pneumatic pump chamber 70a, and fresh or used PD fluid is correspondingly pulled into the fluid pump chamber. The above process of the third main embodiment is repeated, wherein the control unit 100 accumulates the pump stroke volume until the desired or prescribed amount of fresh or used PD fluid is delivered to the desired fluid destination FD.

[0130] Fourth main embodiment

[0131] Figure 21 to Figure 24 A fourth main embodiment of the system 10 is shown, which also uses an air pump 80 that operates in conjunction with the air cylinder 30. Here, a single air pump 80 and air cylinder are capable of driving two fluid pump chambers 112a, 112b within two pneumatic pump chambers 70a, 70b, respectively. The structure of the air cylinder 30 in the fourth main embodiment is the same as that in the third main embodiment, and includes a piston head 36 and a piston shaft 34 driven by a linear actuator 40. An optional exhaust line and pneumatic exhaust valve (not shown) can be pneumatically connected to the first and second cylinder chambers of each cylinder. In the fourth main embodiment, only the first pneumatic line 56a extends from the air cylinder 30, but the first pneumatic line 56 is bifurcated to also include a second pneumatic line 56b, wherein the first pneumatic line 56a and the second pneumatic line 56b extend to the first and second pneumatic pump chambers 112a, 112b, respectively. The first pneumatic valve 58a and the second pneumatic valve 58b under the control of the control unit 100 are respectively disposed along the first pneumatic line 56a and the second pneumatic line 56b.

[0132] A third pneumatic line 56c extends from the air pump 80 and branches into a fourth pneumatic line 56d. The third pneumatic line 56c intersects the first pneumatic line 56a, and the fourth pneumatic line 56d intersects the second pneumatic line 56b. A third pneumatic valve 58c under the control of the control unit 100 is disposed along the third pneumatic line 56c, and a fourth pneumatic valve 58d under the control of the control unit 100 is disposed along the fourth pneumatic line 56d. The first pressure sensor 44a is disposed adjacent to the pneumatic pump chamber 70a, and the second pressure sensor 44b is disposed adjacent to the pneumatic pump chamber 70b. The first fluid pump chamber 112a and the second fluid pump chamber 112b are disposed as part of the disposable kit 100, wherein the first fluid pump chamber and the second fluid pump chamber pump fresh or used PD fluid from a desired PD fluid source FS to a desired PD fluid destination FD, as determined by a sequence of a plurality of fluid valves SV, DV.

[0133] In the pumping sequence of the fourth main embodiment, the first fluid pump chamber 112a and the second fluid pump chamber 112b are generally alternating, wherein when one fluid pump chamber 112a or 112b draws fresh or used PD fluid, the other fluid pump chamber 112b or 112a pushes out fresh or used PD fluid. Each fluid pump chamber 112a, 112b has its own set of source valves SV and destination valves DV, however, it is not required that the first fluid pump chamber 112a and the second fluid pump chamber 112b are completely synchronized.

[0134] Fig.21 It is shown that the control unit 100 in the fourth main embodiment initially causes the third pneumatic valve 58c and the source fluid valve SV for the first fluid pump chamber 112a to open, and causes the air pump 80 to generate a negative pressure in the first pneumatic pump chamber 70a, thereby pulling the flexible membrane of the first fluid pump chamber 112a into the first pneumatic pump chamber 70a and pulling fresh or used PD fluid into the first fluid pump chamber. During the PD fluid extraction phase, the control unit 100 can again monitor the speed of the air pump 80. When the speed of the air pump 80 begins to decrease beyond a threshold, the control unit 100 determines that the flexible membrane is fully pulled and expanded, and therefore the fluid pump chamber 112a is filled with fresh or used PD fluid, at which point the control unit 100 stops the air pump 80 and closes the source fluid valve SV for the first fluid pump chamber 112a.

[0135] Fig. 22 It is shown that, next, the control unit 100 maintains the third pneumatic valve 58c in an open state and enables the air pump 80 to generate a desired positive pumping pressure (e.g., 1.5 psig read by the first pressure sensor 44a) in the first pneumatic pump chamber 70a. At this time, the piston head 36 of the piston 32 of the cylinder 30 is in the initial piston head position.

[0136] Fig.23 As shown, next, the control unit 100 causes the third pneumatic valve 58c to close, the first pneumatic valve 58a to open, and the first destination fluid valve DV to open. The desired positive pressure built in the first pneumatic pump chamber 70a forces the flexible membrane of the first fluid pump chamber 112a to collapse and push the fresh or used PD fluid to the desired fluid destination FD. As the positive pressure dissipates, the control unit 100 causes the piston 36 to move within the cylinder chamber 30a so that the first pressure sensor 44a continues to read the desired pressure, such as 1.5 psig. At the same time (or nearly at the same time), the control unit 100 causes the fourth pneumatic valve 58d to open, the second source valve SV to open, and the air pump 80 to generate a negative pressure in the second pneumatic pump chamber 70b, thereby pulling the flexible membrane of the second fluid pump chamber 112b into the second pneumatic pump chamber 70b and pulling the fresh or used PD fluid into the second fluid pump chamber.

[0137] Fig.24 It is shown that, eventually, the first flexible membrane of the first fluid pump chamber 112a cannot collapse further, thereby causing the reading at the first pressure sensor 44a to reach a peak, at which time the control unit 100 stops the pump-out translation of the piston head 36 and closes the first destination fluid valve DV. Alternatively or additionally, the detection that the flexible membrane cannot collapse further can be determined by the control unit 100 detecting that the linear actuator 40 and / or the piston head 36 do not move while maintaining the desired pressure (e.g., 1.5 psig). In any case, after stopping the pump-out translation, the first pneumatic valve 58a remains open to allow the positive pressure that has been maintained at the desired pressure to balance between the cylinder chamber 30a and the first pneumatic pump chamber 70a, and the positive pressure can be read by the first pressure sensor 44a. The piston head 36 is now in the final piston head position within the cylinder chamber 30a. The volume difference of the cylinder 30 at a known cross-sectional area between the final piston head position and the initial piston head position is the volume of fresh or used PD fluid pumped to the desired fluid destination FD calculated by the control unit 100 due to the same pressure at the initial piston head position and the final piston head position (e.g., 1.5 psig, which is the desired pump-to-patient pressure). For fluid extraction of the second fluid pump chamber 112b, the control unit 100 can again monitor the speed of the air pump 80. When the speed of the air pump 80 begins to drop beyond a threshold, the control unit 100 determines that the flexible membrane of the second fluid pump chamber 112b is fully pulled and expanded, and therefore the second fluid pump chamber is full of fresh or used PD fluid, at which point the control unit stops the air pump 80 and closes the second source fluid valve SV for the second fluid pump chamber 112b.

[0138] The control unit 100 then retracts the piston 32 to the initial position and repeats the above process, but with the first fluid pump chamber 112a filled with fresh or used PD fluid and the second fluid pump chamber 112b pushing the fresh or used PD fluid to the desired fluid destination FD. The control unit 100 accumulates the known stroke volume and continues to perform the alternating pumping sequence just described until the desired or prescribed amount of fresh or used PD fluid is delivered to the desired fluid destination FD.

[0139] Fifth main embodiment

[0140] Figure 25 to Figure 28 A fifth main embodiment of the system 10 is shown, which, like the fourth main embodiment, also uses an air pump 80 that operates in cooperation with the cylinder 30 to drive two pneumatic pump chambers 70a, 70b and their corresponding fluid pump chambers 112a, 112b. In the fourth main embodiment, the cylinder 30 is unidirectional with respect to fluid volume metering because only one side (chamber 30a) of the piston head 36 within the cylinder is exposed to the first pressure sensor 44a and the second pressure sensor 44b. In the fourth embodiment, after each fluid pump chamber extraction / fluid pump chamber delivery sequence, the piston 32 needs to be reset accordingly. In the fifth main embodiment, a fifth pneumatic line 56e is added, which extends from the first pneumatic line 56a to the opposite side of the cylinder 30 so that there is pneumatic access to the cylinder on both sides of the piston head 36. A fifth pneumatic valve 58e is provided to operate with the fifth pneumatic line 56e. A sixth pneumatic valve 58f is added along the first pneumatic line 56a as a second valve that allows the cylinder 30 at the chamber 30b to be closed.

[0141] Fig.25 It is shown that in the pumping sequence of the fifth main embodiment using the system 10, the control unit 100 opens the second pneumatic valve 58b and the fifth pneumatic valve 58f, opens the second destination fluid valve DV, and moves the piston head 36 of the cylinder 30 in the first direction to deliver fresh or used PD fluid from the second fluid pump chamber 112b to the desired destination FD. At the same time, the control unit 100 opens the third pneumatic valve 58c and the first source fluid valve SV so that the air pump 80 can apply negative pressure to the flexible membrane of the first fluid pump chamber 112a, thereby pulling fresh or used PD fluid into the first fluid pump chamber.

[0142] Fig.26It is shown that, eventually, the second flexible membrane of the second fluid pump chamber 112b cannot collapse further, causing the reading at the second pressure sensor 44b to reach a peak, at which time the control unit 100 stops the pump-out translation of the piston head 36 and closes the second destination fluid valve DV. Alternatively or additionally, the detection that the flexible membrane cannot collapse further can be determined by the control unit 100 detecting that the linear actuator 40 and / or the piston head 36 do not move while maintaining the desired pressure (e.g., 1.5 psig). In any case, after stopping the pump-out translation, the second pneumatic valve 58b and the fifth pneumatic valve 58e remain open to allow the positive pressure that has been maintained at the desired pressure to balance between the cylinder chamber 30a and the second pneumatic pump chamber 70b, and this positive pressure can be read by the second pressure sensor 44b. The volume difference of the cylinder 30 at a known cross-sectional area between the initial piston head position and the final piston head position is the volume of fresh or used PD fluid pumped to the desired fluid destination DV calculated by the control unit 100 due to the same pressure at the initial piston head position and the final piston head position (e.g., 1.5 psig, which is the desired pump-to-patient pressure). For fluid extraction of the first fluid pump chamber 112a, the control unit 100 can again monitor the speed of the air pump 80. When the speed of the air pump 80 begins to drop beyond a threshold, the control unit 100 determines that the flexible membrane of the first fluid pump chamber 112a is fully pulled and expanded, and therefore the first fluid pump chamber is full of fresh or used PD fluid, at which point the control unit 100 stops the air pump 80 and closes the first source fluid valve SV for the first fluid pump chamber 112a.

[0143] Fig. 27 1 and 12. It is shown that, next, the first fluid pump chamber 112a and the second fluid pump chamber 112b switch operations so that the second fluid pump chamber 112b extracts fresh or used PD fluid, while the first fluid pump chamber 112a delivers fresh or used PD fluid. It is noteworthy that there is no need to adjust the piston head 36 to prepare the cylinder 30 for such switching. Here, the control unit 100 opens the first pneumatic valve 58a and the sixth pneumatic valve 58f, opens the first destination fluid valve DV, and moves the piston head 36 of the cylinder 30 in the second direction to deliver fresh or used PD fluid from the first fluid pump chamber 112a to the desired fluid destination FD. At the same time, the control unit 100 opens the fourth pneumatic valve 58d and the second source fluid valve SV so that the air pump 80 can apply negative pressure to the flexible membrane of the second fluid pump chamber 112b, thereby pulling fresh or used PD fluid into the second fluid pump chamber.

[0144] Fig.28It is shown that, eventually, the first flexible membrane of the first fluid pump chamber 112a cannot collapse further, causing the reading at the first pressure sensor 44a to reach a peak, at which time the control unit 100 stops the pump-out translation of the piston head 36 and closes the first destination fluid valve DV. Alternatively or additionally, the detection that the flexible membrane cannot collapse further can be determined by the control unit 100 detecting that the linear actuator 40 and / or the piston head 36 do not move while maintaining the desired pressure (e.g., 1.5 psig). In any case, after stopping the pump-out translation, the first pneumatic valve 58a and the sixth pneumatic valve 58f remain open to allow the positive pressure that has been maintained at the desired pressure to balance between the second cylinder chamber 30b and the first pneumatic pump chamber 70a, and this positive pressure can be read by the first pressure sensor 44a. The volume difference of the cylinder 30 at a known cross-sectional area between the initial piston head position and the final piston head position is the volume of fresh or used PD fluid pumped to the desired fluid destination FD calculated by the control unit 100 due to the same pressure at the initial piston head position and the final piston head position (e.g., 1.5 psig, which is the desired pump-to-patient pressure). For fluid extraction of the second fluid pump chamber 112b, the control unit 100 can again monitor the speed of the air pump 80. When the speed of the air pump 80 begins to drop beyond a threshold, the control unit 100 determines that the flexible membrane of the second fluid pump chamber 112b is fully pulled and expanded, and therefore the second fluid pump chamber is full of fresh or used PD fluid, at which point the control unit 100 stops the air pump 80 and closes the second source fluid valve SV for the second fluid pump chamber 112b.

[0145] The control unit 100 accumulates the known stroke volume and continues to perform the alternating pumping sequence just described until the desired or prescribed amount of fresh or spent PD fluid is delivered to the desired fluid destination FD. It should be understood that for any of the first through fifth main embodiments described above, the delivery pressure can be higher, such as up to 8 psig, for fresh or spent PD fluid destinations that do not involve a patient (e.g., the heater container 116a or the drain container 116b). It is also contemplated that for any of the first through fifth main embodiments, the control unit 100 monitors the associated first pressure sensor 44a or second pressure sensor 44b as the cylinder 30 or pump 80 removes spent PD fluid from the patient so that the patient drain negative pressure limit (e.g., -1.5 psig) is not met or exceeded.

[0146] It should be appreciated that the drift effects in the pneumatic pressure sensors 44a, 44b used in the above-described embodiments are offset because the important aspect of the above-described sequence involving the air cylinder 30 is that the initial and final pressures associated with fresh or spent PD fluid delivery are equal, not that the pressures are accurate from an absolute perspective (except for the patient pumping pressure limit). Also, because the system 10 is pressure controlled, the linear actuator 40 does not have to be highly accurate.

[0147] 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. Such changes and modifications may be made without departing from the spirit and scope of the present subject matter and without reducing its expected advantages. Therefore, these changes and modifications are intended to be covered by the appended claims.

Claims

1. A peritoneal dialysis system, comprising: Pneumatic pump room; cylinder; a piston including a piston head slidably sealed within the cylinder, the piston head separating the first cylinder chamber from the second cylinder chamber; a linear actuator in mechanical communication with the piston; a first pneumatic line extending between the first cylinder chamber and the pneumatic pump chamber; a second pneumatic line extending between the second cylinder chamber and the pneumatic pump chamber; a first pneumatic valve positioned along the first pneumatic line; a second pneumatic valve positioned along the second pneumatic line; a pressure sensor positioned and arranged to measure pressure in the pneumatic pump chamber; a fluid pump chamber operably coupled to the pneumatic pump chamber; source fluid valve; Destination Fluid Valve; as well as A control unit, the control unit being configured to (i) open the second pneumatic valve and the source fluid valve, and cause the linear actuator to move the piston head into the first cylinder chamber so as to generate a negative pneumatic pressure in the second cylinder chamber and the pneumatic pump chamber, thereby pulling the source fluid into the fluid pump chamber, and (ii) close the second pneumatic valve and the source fluid valve, open the first pneumatic valve and the destination fluid valve and cause the linear actuator to move the piston head further into the first cylinder chamber so as to push the source fluid through the destination fluid valve, and wherein the control unit uses the output from the pressure sensor to control the linear actuator so that the final pressure for (ii) is at least substantially equal to the initial pressure for (ii), so that the volume of the space corresponding to the movement of the piston head in the cylinder during (ii) is equal to the volume of the source fluid delivered from the fluid pump chamber during (ii).

2. The peritoneal dialysis system according to claim 1, wherein: The source fluid valve is used with a PD fluid supply container, heated container, or patient line.

3. The peritoneal dialysis system according to claim 1, wherein: The destination fluid valve is used to heat a container, drain a container, or a patient line.

4. The peritoneal dialysis system according to claim 1, wherein: The volume of the space corresponding to the movement of the piston head in the cylinder varies with the distance the piston head moves in the cylinder and the cross-sectional area of ​​the inner diameter of the cylinder.

5. The peritoneal dialysis system according to claim 1, wherein: The control unit is configured to determine a volume of source fluid delivered from the fluid pump chamber during (ii) with both the source fluid valve and the destination fluid valve closed.

6. The peritoneal dialysis system according to claim 1, wherein: The control unit is further configured to: when the first pneumatic valve and the destination fluid valve are closed, (iii) open the second pneumatic valve and the source fluid valve to allow the negative pneumatic pressure in the second cylinder chamber generated during at least one of (i) or (ii) to reach the pneumatic pump chamber, thereby pulling the source fluid into the fluid pump chamber.

7. The peritoneal dialysis system according to claim 6, wherein: The control unit is also configured to: when the first pneumatic valve, the source fluid valve and the destination fluid valve are closed and the second pneumatic valve is closed, (iv) cause the linear actuator to move the piston head into the second cylinder chamber so as to generate at least substantially zero pressure in the first cylinder chamber and the second cylinder chamber.

8. The peritoneal dialysis system according to claim 7, wherein: The control unit is also configured to (v) cause the second pneumatic valve and the destination fluid valve to open, and cause the linear actuator to move the piston head into the second cylinder chamber so as to push the source fluid through the destination fluid valve, and wherein the control unit uses the output from the pressure sensor to control the linear actuator so that the final pressure used for (v) is at least substantially equal to the initial pressure used for (v), so that the volume of the space corresponding to the movement of the piston head in the cylinder during (v) is equal to the volume of the source fluid delivered from the fluid pump chamber during (v).

9. The peritoneal dialysis system according to claim 8, wherein: The control unit is also configured to: when the second pneumatic valve and the destination fluid valve are closed, (vi) open the first pneumatic valve and the source fluid valve to allow the negative pneumatic pressure in the first cylinder chamber generated during (v) to reach the pneumatic pump chamber, thereby pulling the source fluid into the fluid pump chamber.

10. A peritoneal dialysis system, comprising: Pneumatic pump room; cylinder; a piston including a piston head slidably sealed within the cylinder; a linear actuator in mechanical communication with the piston; air pump; a first pneumatic line extending between the cylinder and the pneumatic pump chamber; a second pneumatic line extending between the air pump and the pneumatic pump chamber; a first pneumatic valve positioned along the first pneumatic line; a second pneumatic valve positioned along the second pneumatic line; a pressure sensor positioned and arranged to measure pressure in the pneumatic pump chamber; a fluid pump chamber operably coupled to the pneumatic pump chamber; source fluid valve; Destination Fluid Valve; as well as A control unit configured to: (i) open the second pneumatic valve and the source fluid valve and cause the air pump to generate a negative pneumatic pressure in the pneumatic pump chamber to draw the source fluid into the fluid pump chamber, (ii) close the source fluid valve and, with the second pneumatic valve open, cause the air pump to generate a desired positive pressure in the pneumatic pump chamber as measured by the pressure sensor, and (iii) close the second pneumatic valve, open the first pneumatic valve and the destination fluid valve, and cause the linear actuator to move the piston head within the cylinder to push the source fluid through the destination fluid valve, and wherein the control unit uses the output from the pressure sensor to control the linear actuator so that the final pressure for (iii) is at least substantially equal to the initial pressure for (iii) and so that the volume of the space corresponding to the movement of the piston head within the cylinder during (iii) is equal to the volume of the source fluid delivered from the fluid pump chamber during (iii).

11. The peritoneal dialysis system according to claim 10, wherein: The source fluid valve is used with a PD fluid supply container, heated container, or patient line.

12. The peritoneal dialysis system according to claim 10, wherein: The destination fluid valve is used to heat a container, drain a container, or a patient line.

13. The peritoneal dialysis system according to claim 10, wherein: The volume of the space corresponding to the movement of the piston head in the cylinder varies with the distance the piston head moves in the cylinder and the cross-sectional area of ​​the inner diameter of the cylinder.

14. The peritoneal dialysis system according to claim 10, wherein: During (i), the first pneumatic valve is open.

15. The peritoneal dialysis system according to claim 10, wherein: The control unit is further configured to: when the first pneumatic valve and the source fluid valve are open, (iv) cause the linear actuator to move the piston head in an opposite direction within the cylinder to draw source fluid into the fluid pump chamber.

16. The peritoneal dialysis system according to claim 15, wherein: During (iv), the first pneumatic valve is opened and the air pump is actuated to help draw source fluid into the fluid pump chamber.

17. A peritoneal dialysis system, comprising: The first pneumatic pump chamber; The second pneumatic pump chamber; cylinder; a piston including a piston head slidably sealed within the cylinder; a linear actuator in mechanical communication with the piston; air pump; a first pneumatic line extending between the cylinder and the first pneumatic pump chamber; a second pneumatic line extending between the cylinder and the second pneumatic pump chamber; a third pneumatic line extending between the air pump and the first pneumatic pump chamber; a fourth pneumatic line extending between the air pump and the second pneumatic pump chamber; a first pneumatic valve positioned along the first pneumatic line; a second pneumatic valve positioned along the second pneumatic line; a third pneumatic valve positioned along a third pneumatic line; a fourth pneumatic valve positioned along the fourth pneumatic line; a first pressure sensor positioned and arranged to measure pressure in the first pneumatic pump chamber; a second pressure sensor positioned and arranged to measure pressure in the second pneumatic pump chamber; a first fluid pump chamber operably coupled to the first pneumatic pump chamber; a first source fluid valve for the first pump chamber; a first destination fluid valve for the first pump chamber; a second fluid pump chamber operably coupled to the first pneumatic pump chamber; a second source fluid valve for the second pump chamber; a second destination fluid valve for the second pump chamber; as well as a control unit configured to generate negative and positive pneumatic pressures in the first and second pneumatic pump chambers using the air pump, and to actuate the linear actuator to move the piston head within the cylinder while equalizing the initial and final positive pneumatic pressures to meter a determinable volume of source fluid through the first and second destination fluid valves.

18. The peritoneal dialysis system according to claim 17, wherein: The control unit is configured to: (i) with the third pneumatic valve and the first source fluid valve open, causing the air pump to generate negative pneumatic pressure in the first pneumatic pump chamber, thereby pulling the source fluid into the first fluid pump chamber, (ii) causing the air pump to generate a desired positive pneumatic pressure in the first pneumatic pump chamber as measured by the first pressure sensor with the third pneumatic valve open and the first source fluid valve closed, and (iii) when the first pneumatic valve and the first destination fluid valve are opened, the linear actuator moves the piston head in the cylinder so as to push the source fluid through the first destination fluid valve, and wherein the control unit uses the output from the first pressure sensor to control the linear actuator so that the final pressure used for (iii) is at least substantially equal to the initial pressure used for (iii), so that the volume of the space corresponding to the movement of the piston head in the cylinder during (iii) is equal to the volume of the source fluid delivered from the first fluid pump chamber during (iii), and when the fourth pneumatic valve and the second source fluid valve are opened, the air pump generates a negative pneumatic pressure in the second pneumatic pump chamber to pull the source fluid into the second fluid pump chamber.

19. The peritoneal dialysis system according to claim 18, wherein: The control unit is further configured to, when the piston head moves to the retracted position: (iv) causing the air pump to generate a desired positive pneumatic pressure in the second pneumatic pump chamber as measured by the first pressure sensor with the fourth pneumatic valve open and the second source fluid valve closed, and (v) with the second pneumatic valve and the second destination fluid valve opened, causing the linear actuator to move the piston head within the cylinder so as to push the source fluid through the second destination fluid valve, and wherein the control unit uses the output from the second pressure sensor to control the linear actuator so that the final pressure for (v) is at least substantially equal to the initial pressure for (v), so that the volume of the space corresponding to the movement of the piston head within the cylinder during (v) is equal to the volume of the source fluid delivered from the second fluid pump chamber during (v), and with the third pneumatic valve and the first source fluid valve opened, causing the air pump to generate a negative pneumatic pressure in the first pneumatic pump chamber to pull the source fluid into the first fluid pump chamber.

20. A peritoneal dialysis system, comprising: The first pneumatic pump chamber; The second pneumatic pump chamber; cylinder; a piston including a piston head slidably sealed within the cylinder, the piston head separating the first cylinder chamber from the second cylinder chamber; a linear actuator in mechanical communication with the piston; air pump; a first pneumatic line extending between the second cylinder chamber and the first pneumatic pump chamber; a second pneumatic line extending between the second cylinder chamber and the second pneumatic pump chamber; a third pneumatic line extending between the air pump and the first pneumatic pump chamber; a fourth pneumatic line extending between the air pump and the second pneumatic pump chamber; a fifth pneumatic line extending between the first cylinder chamber and the first pneumatic line; a first pneumatic valve positioned along the first pneumatic line; a second pneumatic valve positioned along the second pneumatic line; a third pneumatic valve positioned along a third pneumatic line; a fourth pneumatic valve positioned along the fourth pneumatic line; a fifth pneumatic valve positioned along the fifth pneumatic line; a sixth pneumatic valve, the sixth pneumatic valve being positioned adjacent to the second cylinder chamber; a first pressure sensor positioned and arranged to measure pressure in the first pneumatic pump chamber; a second pressure sensor positioned and arranged to measure pressure in the second pneumatic pump chamber; a first fluid pump chamber operably coupled to the first pneumatic pump chamber; a first source fluid valve for the first pump chamber; a first destination fluid valve for the first pump chamber; a second fluid pump chamber operably coupled to the first pneumatic pump chamber; a second source fluid valve for the second pump chamber; a second destination fluid valve for the second pump chamber; as well as a control unit configured to generate negative and positive pneumatic pressures in the first and second pneumatic pump chambers using the air pump, and to actuate the linear actuator to move the piston head within the first and second cylinder chambers while equalizing an initial positive and final positive pneumatic pressures to meter a determinable volume of source fluid through the first and second destination fluid valves.

21. The peritoneal dialysis system according to claim 20, wherein: The control unit is configured to: (i) when the third pneumatic valve and the first source fluid valve are opened, the air pump generates a negative pneumatic pressure in the first pneumatic pump chamber to pull the source fluid into the first fluid pump chamber, and when the second pneumatic valve, the fifth pneumatic valve and the second destination fluid valve are opened, the linear actuator moves the piston head toward the first cylinder chamber to push the source fluid through the second destination fluid valve, and wherein the control unit uses the output from the second pressure sensor to control the linear actuator so that the final pressure for (i) is at least substantially equal to the initial pressure for (i), so that the volume of the space corresponding to the movement of the piston head toward the first cylinder chamber during (i) is equal to the volume of the source fluid delivered from the second fluid pump chamber during (i).

22. The peritoneal dialysis system according to claim 21, wherein: The control unit is further configured to: (ii) when the fourth pneumatic valve and the second source fluid valve are opened, the air pump generates a negative pneumatic pressure in the second pneumatic pump chamber to pull the source fluid into the second fluid pump chamber, and when the first pneumatic valve, the sixth pneumatic valve and the first destination fluid valve are opened, the linear actuator moves the piston head toward the second cylinder chamber to push the source fluid through the first destination fluid valve, and wherein the control unit uses the output from the first pressure sensor to control the linear actuator so that the final pressure used for (ii) is at least substantially equal to the initial pressure used for (ii), so that the volume of the space corresponding to the movement of the piston head toward the second cylinder chamber during (ii) is equal to the volume of the source fluid delivered from the second fluid pump chamber during (ii).

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