CN117717664A - Hemodialysis system with variable dialysate flow - Google Patents

Abstract

A hemodialysis system is provided with a variable dialysate flow that is a portable hemodialysis system that includes a dialyzer, a closed-loop blood flow path that conveys blood from a patient through the dialyzer and back to the patient, and a closed-loop dialysate flow path that conveys dialysate through the dialyzer. Preferably, the hemodialysis system includes an adsorption filter in the dialysate flow path. Further, the hemodialysis machine includes a blood pump and a pair of dialysate pumps. The processor controls the flow of blood through the blood flow path, and the processor controls the flow of dialysate through the dialysate flow path. In addition, the processor stores a patient treatment plan in which the flow of dialysate through the dialysate flow path is reduced throughout the patient treatment period to maximize the amount of urea purged by the adsorption filter.

Description

Hemodialysis system with variable dialysate flow

Technical Field

The present invention relates to an artificial kidney system for providing dialysis. More particularly, the present invention relates to a hemodialysis system for a hemodialysis system.

Background

Applicant incorporates by reference in this application any and all patents and published patent applications cited or referred to in this application.

Hemodialysis is a medical procedure for effecting extracorporeal removal of waste products including creatine, urea, and free water from a patient's blood, including diffusion of solutes across a semi-permeable membrane. Failure to properly remove such waste products can lead to renal failure.

During hemodialysis, a patient's blood is withdrawn through an arterial line, treated with a dialysis machine, and returned to the body through a venous line. The dialysis machine includes a dialyzer containing a plurality of hollow fibers that form a semipermeable membrane through which blood is transported. In addition, dialysis machines use dialysate that is also pumped through the dialyzer, which contains appropriate amounts of electrolytes and other essential components (e.g., glucose).

Typically, the dialysate is prepared by mixing water with the appropriate proportions of the acid concentrate and bicarbonate concentrate. Because the calcium and magnesium in the acid concentrate precipitate out upon contact with the high level of bicarbonate in the bicarbonate concentrate, it is preferred to separate the acid and bicarbonate concentrate until final mixing just prior to use in the dialyzer. The dialysate can also include appropriate levels of sodium, potassium, chloride, and glucose.

The dialysis process across the membrane is achieved by a combination of diffusion and convection. Diffusion requires the migration of molecules from high concentration regions to low concentration regions by random movement. At the same time, convection generally requires movement of the solute in response to a difference in hydrostatic pressure. The semi-permeable membrane forming fibers separate the plasma from the dialysate and provide a large surface area for diffusion, allowing waste products including urea, potassium, and phosphate to permeate into the dialysate while preventing the transfer of larger molecules such as blood cells, polypeptides, and certain proteins into the dialysate.

Typically, the dialysate flows in a direction opposite to the blood flow in the extracorporeal circuit. Countercurrent flow maintains a concentration gradient across the semipermeable membrane, thereby increasing dialysis efficiency. In some cases, hemodialysis may provide fluid removal, also known as ultrafiltration. Ultrafiltration is typically accomplished by reducing the hydrostatic pressure of the dialysate compartment of the dialyzer, allowing water containing dissolved solutes (including electrolytes and other permeable substances) to migrate across the membrane from the plasma into the dialysate. In rare cases, the fluid in the dialysate flow path portion of the dialyzer is higher than the blood flow portion, resulting in movement of fluid from the dialysis flow path to the blood flow path. This is commonly referred to as reverse ultrafiltration. Ultrafiltration and reverse ultrafiltration are typically performed under the supervision of trained medical personnel, as ultrafiltration and reverse ultrafiltration increase the risk to the patient.

Unfortunately, hemodialysis suffers from a number of drawbacks. Arteriovenous fistulae are the most common access points. To form a fistula, the physician ties the artery and vein together. Since this process bypasses the capillaries of the patient, blood flow is rapid. For each dialysis, the fistula must be punctured with a large needle to deliver blood into the dialyzer and return blood from the dialyzer. Typically, the procedure is performed 3 times per week, requiring 3-4 hours for an outpatient. To a lesser extent, patients undergo hemodialysis at home. Home dialysis is typically performed for six days a week for two hours each. However, home hemodialysis requires more frequent treatment.

Home hemodialysis suffers from other drawbacks. Current home dialysis systems are bulky, complex, daunting and difficult to operate. The apparatus requires a great deal of training. Home hemodialysis systems are currently too large to carry, thereby impeding the travel of hemodialysis patients. Home hemodialysis systems are expensive and require a high initial capital investment, especially compared to central hemodialysis where the patient is not required to pay the machine cost. Current home hemodialysis systems do not adequately provide for reuse of supplies, making home hemodialysis economically affordable to medical suppliers. Because of the above drawbacks, few aggressive patients are willing to take on the business of home hemodialysis.

Furthermore, hemodialysis systems using adsorption filters have not been widely accepted. Unfortunately, adsorption filters are relatively expensive and may be consumed quickly due to an ion exchange that occurs when excess dialysis ions-k+, ca++, mg++, and phosphate (PO 4) are exchanged for benign or less toxic ions (e.g., na+, h+, bicarbonate (HCO 3-) and acetate).

There is therefore a great need for a hemodialysis system that is easy to transport, light in weight, easy to use, patient friendly and thus can be used in a clinic or home.

Furthermore, it is desirable to provide a hemodialysis system that does not present a single point of failure in the pump, motor, tubing or electronics that would endanger the patient.

Further, it is desirable to provide a hemodialysis system that can be used in multiple modes (e.g., with or without a filter to purify dialysate).

Furthermore, it is desirable to operate the hemodialysis system in a manner that maximizes the lifetime of the adsorption filter.

The various aspects of the present invention fulfill these needs and provide further related advantages as described in the summary section below.

Disclosure of Invention

According to a first aspect of the present invention, there is provided a hemodialysis system comprising: an arterial blood line for connection to an artery of a patient to collect blood from the patient; a venous blood line for connection to a vein of a patient to return blood to the patient; reusable dialysis machines; a disposable dialyzer.

The arterial and venous blood lines may have typical structures known to those skilled in the art. For example, the arterial blood line may be a conventional flexible hollow tube connected to a needle for collecting blood from an artery of a patient. Similarly, the venous blood line may be a conventional flexible tube and needle for returning blood to the patient's vein. Various structures and surgical procedures may be employed to access the patient's blood, including intravenous catheters, arteriovenous fistulae, or synthetic grafts.

Preferably, the disposable dialyzer has a construction and design known to those skilled in the art, including a blood flow path and a dialysate flow path. The term "flow path" is intended to refer to one or more fluid conduits, also referred to as channels, for carrying a fluid. The catheter may be constructed in any manner determinable by one of skill in the art, including, for example, a flexible medical tubing or a non-flexible hollow metal or plastic housing. The blood flow path carries blood in a closed loop system by being connected to an arterial blood line and a venous blood line for carrying blood from the patient to the dialyzer and back to the patient. At the same time, the dialysate flow path carries dialysate from the dialysate supply to the dialyzer and back to the dialysate supply in a closed loop system. Both the blood flow path and the dialysate flow path pass through the dialyzer, but these flow paths are separated by the semipermeable membrane of the dialyzer.

Preferably, the hemodialysis system comprises a reservoir for holding dialysate. The reservoir is connected to a dialysate flow path of the hemodialysis system to form a closed loop system for transporting dialysate from the reservoir to a dialyzer of the hemodialysis system and back to the reservoir. Alternatively, the hemodialysis system has two (or more) dialysate reservoirs, which can be placed alternately in the dialysate flow path. When one reservoir is carrying contaminated dialysate, the dialysis treatment can be continued using the other reservoir while the reservoir with contaminated dialysate is emptied and refilled. The reservoir may be of any size desired by the clinician to perform the appropriate hemodialysis treatment. Preferably, however, both reservoirs are of the same size and small enough to make the dialysis machine easy to carry. Acceptable reservoir capacities are 0.5 liters to 6.0 liters. In the case of a hemodialysis system comprising only one reservoir, the acceptable reservoir capacity is 12.0 liters.

The hemodialysis system preferably has one or more heaters thermally coupled to the reservoir for heating the dialysate stored within the reservoir. In addition, the hemodialysis system includes a temperature sensor for measuring the temperature of the dialysate within the reservoir. The hemodialysis system preferably has a level sensor for detecting the level of liquid in the reservoir. The level sensor may be any type of sensor for determining the amount of fluid within the reservoir. Acceptable level sensors include magnetic or mechanical float-type sensors, conductivity sensors, ultrasonic sensors, optical interfaces, and weight measurement sensors, such as scales or weighing sensors for measuring the weight of dialysate in the reservoir.

Preferably, the dialysis comprises three main pumps. The first and second "dialysate" pumps are connected to the dialysate flow path for pumping dialysate from the reservoir to the dialyzer and back to the reservoir through the dialysate flow path. Preferably, the first pump is located in the dialysate flow path "upstream" (meaning before in the flow path) of the dialyzer, and the second pump is located in the dialysate flow path "downstream" (meaning after in the flow path). Meanwhile, a third main pump of the hemodialysis system is connected to the blood flow path. The "blood" pump pumps blood from the patient through arterial, dialyzer and venous blood lines to return to the patient. Preferably, the third pump is located in the blood flow path upstream of the dialyzer.

The hemodialysis system may also contain one or more adsorption filters for removing toxins from the plasma that permeate through the semipermeable membrane to the dialysate. Filter materials for use in filters are well known to those skilled in the art. For example, suitable materials include resin beds, including zirconium-based resins. Acceptable materials are also described in U.S. patent No. 8,647,506 and U.S. patent publication No. 2014/0001112.

In a first embodiment, an adsorption filter is connected in the dialysate flow path downstream of the dialyzer to remove toxins from the dialysate before the dialysate is transported back to the reservoir. In a second embodiment, the filter is located outside of the closed loop dialysate flow path, but within a separate closed loop "filter" flow path that is selectively connected to either of the two dialysate reservoirs. For this embodiment, the hemodialysis system preferably comprises an additional fluid pump for pumping contaminated dialysate through the filter flow path and its filters.

Preferably, the hemodialysis system includes two additional flow paths in the form of a "drain" flow path and a "fresh dialysate" flow path. The drain path includes one or more fluid drain lines for draining the reservoir of contaminated dialysate, while the fresh dialysate flow path includes one or more fluid fill lines for transporting fresh dialysate from the fresh dialysate supply to the reservoir. One or more fluid pumps may be connected to the drain path and/or the fresh dialysate flow path to deliver the fluids to their intended destinations.

Further, the hemodialysis system includes a plurality of fluid valve assemblies for controlling the flow of blood through the blood flow path, for controlling the flow of dialysate through the dialysate flow path, and for controlling the flow of spent dialysate through the filter flow path. The valve assembly may be any type of electromechanical fluid valve structure as may be determined by one skilled in the art, including, but not limited to, conventional electromechanical two-way fluid valves and three-way fluid valves. A two-way valve is any type of valve having two ports, including an inlet port and an outlet port, wherein the valve simply allows or blocks the flow of fluid through a fluid path. In contrast, a three-way valve has three ports and is used to close fluid flow in one fluid path while opening fluid flow in another path. In addition, the valve assembly of the dialysis machine can include a safety pinch valve, such as a pinch valve connected to the venous blood line, for selectively allowing or preventing blood flow through the venous blood line. A pinch valve is provided to pinch the venous blood line in the event an unsafe condition is detected, thereby preventing blood from flowing back into the patient.

Preferably, the hemodialysis system comprises a sensor for monitoring hemodialysis. For this purpose, the dialysis machine preferably has at least one flow sensor connected to the dialysate flow path for detecting the fluid flow (volume and/or speed) in the dialysate flow path. Further, it is preferred that the dialysis machine comprises one or more pressure sensors for detecting the pressure in the dialysate flow path, or at least one occlusion sensor for detecting whether the dialysate flow path is occluded. Preferably, the dialysis machine also has one or more sensors for measuring pressure and/or fluid flow within the blood flow path. The pressure and flow sensors may be separate components or a single sensor may be used to measure both pressure and flow.

Further, preferably, the hemodialysis system includes a blood leak detector ("BLD") that monitors the flow of dialysate through the dialysate flow path and detects whether blood has inappropriately diffused into the dialysate flow path through the semi-permeable membrane of the dialyzer. In a preferred embodiment, the hemodialysis system includes a blood leak sensor assembly that includes a light source that emits light through the dialysate flow path and a light sensor that receives light emitted through the dialysate flow path. After passing through the dialysate flow path, the received light is next analyzed to determine whether the light has changed to reflect possible blood in the dialysate.

The dialysis machine preferably includes additional sensors, including an ammonia sensor and a pH sensor, for detecting the level of ammonia and pH within the dialysate. Preferably, the ammonia sensor and the pH sensor are located in the dialysate flow path immediately downstream of the filter. Further, the dialysis machine has a bubble sensor connected to the arterial blood line and a bubble sensor connected to the venous blood line for detecting whether bubbles have formed in the blood flow path.

The hemodialysis system has a processor that contains dedicated electronics for controlling the hemodialysis system. The processor contains power management and control circuitry connected to the pump motor, valves, and dialysis machine sensors for controlling the proper operation of the hemodialysis system.

It has been found that decreasing the flow of dialysate through the dialysate flow path increases the ability of the zirconium phosphate of the adsorption filter to capture ammonium from urea. Because urea is high at the beginning of a patient treatment and then cleared during the course of the treatment, a constant urea concentration needs to start at a high flow rate and decrease the urea concentration during the treatment. Advantageously, any urea removal loss due to reduced dialysate flow can be compensated for by extending the duration of the dialysis treatment. Thus, in a preferred embodiment, the processor of the hemodialysis system includes a memory that stores one or more patient treatment plans for treating a patient. The dialysate flow through the dialysate flow path is not static throughout the treatment process according to the patient treatment plan. Conversely, dialysate flow can decrease throughout the treatment of the patient. The decrease in dialysate flow can be incremental. Alternatively, the dialysate flow can be reduced in any manner, such as linearly, exponentially, inversely, polynomials, or other relationships that provide for a reduction in dialysate flow over time.

Specifically, each patient treatment plan includes a total time period "T (total)" for treating the patient, which in turn includes a plurality of time slices including time slice T1, time slice T2, time slice T3, and so on. The patient treatment plan also includes a plurality of flows, including high flows that operate at least during time segment T1, time segment T2, time segment T3, and so on. As will be appreciated by those skilled in the art, if the decrease in dialysate flow varies slowly, e.g., in a linear or polynomial fashion, the time period of each time segment may be very small.

Preferably, the dialysis treatment starts with a higher dialysate flow rate of between 400 and 800 ml/min and ends with a lower flow rate of between 100 and 500 ml/min. More preferably, the dialysis treatment starts with a higher dialysate flow rate of between 450 and 800 ml/min and ends with a lower flow rate of between 100 and 450 ml/min. In a preferred embodiment, the patient treatment plan lasts 2-6 hours and starts treatment with a dialysate flow rate of about 400 to 600 ml/min and decreases linearly until ending with a flow rate of between 200 to 300 ml/min. In yet a more preferred embodiment, the patient treatment plan begins treatment at a dialysate flow rate of about 500 ml/min and drops linearly for four hours until ending at a flow rate of 250 ml/min.

The dialysis machine provides a hemodialysis system that is easy to transport, lightweight, easy to use, patient friendly, and capable of being used at home.

In addition, the hemodialysis system provides a great deal of control and monitoring that the hemodialysis system has not previously provided, thereby providing enhanced patient safety.

In addition, the hemodialysis system maximizes the amount of urea that can be removed by the adsorption filter.

Other features and advantages of the present invention will be appreciated by those skilled in the art upon reading the following detailed description in conjunction with the accompanying drawings.

Drawings

FIG. 1 is a flow chart illustrating a first embodiment of a hemodialysis system;

FIG. 2 is the flow chart of FIG. 1, illustrating an embodiment in which dialysate bypasses the filter through the bypass flow path;

FIG. 3 is the flow chart of FIG. 1, illustrating an embodiment in which dialysate flows through a filter in a closed-loop dialysate flow path that incorporates a first reservoir;

FIG. 4 is the flow chart of FIG. 1, illustrating an embodiment in which dialysate flows through a filter in a closed-loop dialysate flow path that incorporates a second reservoir;

FIG. 5 is a flow chart illustrating a second embodiment of a hemodialysis system that includes a closed-loop filter flow path that filters fluid in a first reservoir;

FIG. 6 is a flow chart illustrating a second embodiment of the hemodialysis system shown in FIG. 5 in which the filter flow path filters fluid in the second reservoir;

FIG. 7 is a flow chart illustrating one embodiment of a hemodialysis system in which dialysate from an external source is supplied to one of the reservoirs of the system and spent dialysate is directed to a reservoir bag or drain;

FIG. 8 is a flow chart illustrating an embodiment of the hemodialysis system of FIG. 7 in which an adsorption filter has been introduced into the system to provide closed loop operation;

FIG. 9 is a block diagram illustrating a blood pump, a dialysate pump, and a flow sensor connected to a hemodialysis system processor; and

FIG. 10 is a chart illustrating a patient treatment plan with reduced dialysate flow;

FIG. 11 is a chart illustrating a second patient treatment plan with reduced dialysate flow;

FIG. 12 is a chart illustrating a third patient treatment plan with reduced dialysate flow; and

fig. 13 is a chart illustrating a fourth patient treatment plan with reduced dialysate flow.

Detailed Description

While the present invention is susceptible of embodiment in various forms, as shown in the drawings, there will hereinafter be described a presently preferred embodiment of the invention, with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiment illustrated.

As best shown in fig. 1-8, the hemodialysis system includes a blood flow path 53 and a dialysate flow path 54. The hemodialysis system also includes a reusable dialysis machine and a disposable assembly for performing hemodialysis. The blood flow path 53 includes an arterial blood line 1 for connection to an artery of a patient to collect blood from the patient and a venous blood line 14 for connection to a vein of the patient to return blood to the patient. The arterial blood line 1 and the venous blood line 14 may have typical structures known to those skilled in the art.

The blood flow path 53 carries blood to the patient in a closed loop system by connection to the arterial blood line 1 and the venous blood line 14 for carrying blood from the patient through the dialyzer 8 and back to the patient. Preferably, the hemodialysis system includes a heparin supply 6 and a heparin pump connected to the blood flow path 1. Heparin pumps deliver small amounts of heparin anticoagulant into the blood stream to reduce the risk of blood clotting in the machine. The heparin pump may take the form of a linear actuated syringe pump, or the heparin pump may be a bag connected to a small peristaltic pump or infusion pump.

The hemodialysis system includes a dialyzer 8 in a dialysate flow path 54, which has a construction and design known to those skilled in the art. Preferably, the dialyzer 8 comprises a plurality of hollow fibers forming a semipermeable membrane. Suitable dialyzers are available from Fresenius healthcare, baxter International, nipro medical and other hollow fiber dialyzer manufacturers. Both the blood flow path and the dialysate flow path span a dialyzer 8, such dialyzer 8 having an inlet for receiving dialysate, an outlet for discharging dialysate, an inlet for receiving blood from the patient, and an outlet for returning blood to the patient. Preferably, the dialysate flows in a direction opposite to blood flowing through the dialyzer, wherein the dialysate flow path is separated from the blood flow path by a semi-permeable membrane (not shown). As shown in fig. 1-6 and explained in more detail below, the dialysate flow path 54 carries dialysate in a closed loop system, wherein dialysate is pumped from the reservoir (17 or 20) to the dialyzer 8 and back to the reservoir (17 or 20). Both the blood flow path 53 and the dialysate flow path 54 pass through the dialyzer 8 but are separated by the semipermeable membrane of the dialyzer.

Preferably, the hemodialysis system comprises three main pumps (5, 26 and 33) for pumping blood and dialysate. For purposes herein, the term "pump" refers to both a pump actuator that uses suction or pressure to move a fluid and a pump motor for mechanically moving the actuator. Suitable pump actuators may include impellers, pistons, diaphragms, lobe pump blades, screw of a screw pump, rollers or linearly moving fingers of a peristaltic pump, or any other mechanical structure for moving fluid as may be determined by one of skill in the art. Meanwhile, the motor of the pump is an electromechanical device that actuates the actuator. The motor may be connected to the pump actuator by a shaft or the like. In a preferred embodiment, the dialysate and/or blood flows through a conventional flexible tubing and each pump actuator is comprised of a peristaltic pump mechanism, wherein each pump actuator includes a rotor having a plurality of cams attached to the outer circumference of the rotor in the form of "rollers", "shoes", "wipers" or "blades" that compress the flexible tubing. As the rotor turns, the pressurized portion of the tube is squeezed shut (or "blocked") forcing fluid to be pumped through the tube. In addition, when the tube cam opens to its natural state after passing, fluid flow is induced through the tube.

The first and second main pumps (26 and 33) are connected to the dialysate flow path for pumping dialysate from the reservoir (17 or 20) to the dialyzer 8 and back to the reservoir (17 or 20) through the dialysate flow path. The first pump 26 is connected to the dialysate flow path "upstream" (meaning front in the flow path) of the dialyzer 8, while the second pump 33 is connected to the dialysate flow path "downstream" (meaning rear in the flow path) of the dialyzer 8. Meanwhile, the third main pump 6 of the hemodialysis system is connected to the blood flow path. A third pump 6, also called a blood pump, pumps blood from the patient through an arterial blood line, through a dialyzer 8, and through a venous blood line to return to the patient. The third pump 6 is preferably connected to the blood flow path upstream of the dialyzer. The hemodialysis system may contain more or less than three main pumps. For example, only a single pump may be used to pump the dialysate through the dialyzer 8. However, it is preferred that the hemodialysis system comprises two pumps, including a first pump 26 upstream of the dialyzer 8 and a second pump 33 downstream of the dialyzer 8.

Preferably, the hemodialysis system comprises one or more reservoirs (17 and 20) for holding dialysate. Where the system includes two reservoirs, both reservoirs (17 and 20) may be connected to the dialysate flow path 54 at the same time to form one large dialysate source. Alternatively, the hemodialysis system includes a valve assembly 21 for introducing either one, but not both, of the two reservoirs (17 or 20) into the dialysate flow path 54 to form a closed loop system for transporting dialysate from one of the two reservoirs to the dialyzer and back to that reservoir. After the dialysate in the first reservoir 17 has been used, is no longer sufficiently clean or has no appropriate chemistry, the valve 21 of the hemodialysis system is controlled to remove the first reservoir 17 from the dialysate flow path and replace the second reservoir 20 with fresh dialysate 75 to the dialysate flow path. Thus, when one reservoir has contaminated dialysate 76 and the reservoir needs to be emptied and refilled with fresh dialysate 75, dialysis treatment can continue using the other reservoir.

In this way, the hemodialysis system can be switched between each reservoir 17 and 20 times during the course of treatment. Furthermore, the presence of two reservoirs opposite one allows to measure the flow for pump calibration or ultrafiltration measurement while isolating the other reservoir when it is emptied or filled. Although the reservoir may have any size desired by the clinician for proper hemodialysis treatment, a preferred reservoir has a volume of between 0.5 liters and 5.0 liters.

The hemodialysis system also includes an adsorption filter (also referred to herein as a "filter") connected to the dialysate flow path 54 for removing toxins that have permeated from plasma through the semipermeable membrane into the dialysate. In the first embodiment, the filter 36 is connected to the dialysate flow path 54 downstream of the dialyzer to remove toxins transferred into the dialysate by the dialyzer prior to transporting the dialysate to the reservoir. Filter materials for dialysis machines are well known to those skilled in the art. For example, suitable materials include resin beds, including zirconium-based resins. Preferably, the filter has a housing comprising a zirconia layer, a zirconium phosphate layer and a carbon layer. Acceptable materials are described in U.S. patent No. 8,647,506 and U.S. patent application publication No. 2014/0001112. Other acceptable filter materials can be developed and used by those skilled in the art without undue experimentation. The filter housing may or may not include a vapor membrane capable of releasing gas but not liquid, in particular, dialysate flowing through the filter.

Where the hemodialysis system has an adsorption filter, the dialysis flow path 54 preferably contains safety features in the form of an ammonium sensor 37 and a pH sensor 38. These sensors may be located directly downstream of the adsorption cartridge 36, or immediately downstream of one or more reservoirs. When the adsorption filter 36 has been exhausted, the filter 36 may begin to release ammonium ions due to the filtering chemistry. At certain levels, ammonium ions in the dialysate can harm the patient. Preferably, the ammonium ion sensor 37 measures the amount of ammonium ions in parts per million (ppm). When the measured value reaches a range of about 5 to 20ppm, a warning state will be activated and the treatment with the dialysis fluid is stopped. The dialysate can be drained and the dialysis treatment can be continued by using fresh dialysate in place of the reservoir. Similarly, the pH sensor 38 also serves as a safety feature and supports the measurement of ammonium ions. As the pH of the dialysate changes, the equilibrium state of ammonia (NH 3) and ammonium ions (nh4+) changes. If the pH of the dialysate is measured to be outside of the pH range of about 6.4 to 7.8, a warning state may be activated and the dialysate in use may be discharged.

It is also preferred that the hemodialysis system has a reagent bag 39 and a pump 40 for introducing reagent into the dialysate flow path 54 immediately after the adsorption filter 36. The reagent bag 39 contains a concentrated solution of salt and ions to re-filter the dialysate. The adsorption filter 36 also removes beneficial ions, such as calcium and salts, from the dialysate by filtering the waste. Before the filtered dialysate can be recycled, calcium and salt must be refilled so that the dialysate does not extract these beneficial ions from the patient's blood. Preferably, the reagent bag 39 will contain 1 to 3 liters of concentrated reagent. The reagent pump 40 may be any type of pump, such as a peristaltic pump or a diaphragm pump. To ensure that the hemodialysis system introduces the proper amounts of salts and ions into the dialysate, a conductivity sensor 41 can be placed in the dialysate flow path 54 immediately after the reagent bag 39. The conductivity sensor 41 serves as a safety feature to measure the total dissolved solids of the regenerated dialysate. In the event that total dissolved solids are detected to be outside of the prescribed range, the operation of pump 40 may be increased or decreased, or the treatment may be stopped altogether. For example, if a fault condition is detected in the dialysate, the fluid may be redirected through the bypass path 30 via the three-way valves 29 and 32 so that the dialysate does not encounter the patient's blood in the dialyzer. More specifically, three-way valve 29 directs dialysate to the inlet of the dialyzer and three-way valve 32 directs dialysate from the dialysate outlet back through dialysate flow path 54. However, if a fault condition is detected in the dialysate, e.g. too low a temperature or too much ammonium ions in the dialysate, the dialysate is redirected by the three-way valves 29 and 32, bypassing the dialyzer 8 through the bypass path 30.

For the embodiment shown in fig. 1-4, the hemodialysis system includes a drain path 55 to treat spent dialysate from the reservoirs (17 and 20). In the embodiment shown in fig. 1-4, the drain path 55 is connected to both reservoirs (17 and 20). The spent dialysate can be discharged through the drain path 5 by gravity feed, and the hemodialysis system can also include any type of pump 44 that can be selected by one skilled in the art to pump the spent dialysate into, for example, a conventional building sewer line 45.

For the embodiment shown in fig. 1-4, the hemodialysis system preferably includes a dialysate source 46 to replenish each reservoir 17 and 20. Preferably, the dialysate source includes a source of clean water 46 mixed with reagents (48 and 50) to provide dialysate of desired characteristics. In a preferred embodiment, the clean water source 46 is provided by a reverse osmosis ("RO") machine located near the apparatus that produces clean water and then adds chemical concentrate to produce dialysate. Fluid is supplied to the reservoirs (17 and 20) through a "fresh dialysate" flow path 56. Preferably, the hemodialysis system also includes a concentrated reagent source (48 and 50) that can be stored in a disposable bag. Preferably, the concentrated reagent contains one or more of the following solutions: carbonate solution, bicarbonate solution, acid solution, lactate solution, and salt solution. It is necessary to divide some of the reagents into two bags (48 and 50) to prevent unwanted interactions or solute precipitation. Concentrated reagent sources (48 and 50) are connected to supply line 46 by pumps (47 and 49). Actuation of pumps (47 and 49) will introduce concentrated reagent into the water source to provide dialysate (17 and 20) to the reservoir.

As an alternative to using the adsorption filter 36, the hemodialysis system includes an auxiliary "bypass" flow path 35 that selectively carries dialysate around the adsorption filter 36. The bypass flow path includes a three-way valve 34 upstream of the filter. The three-way valve 34 is switched to direct the dialysate through the adsorption filter 36, or the three-way valve 34 is switched to direct the dialysate through the bypass flow path 35 to avoid the adsorption filter 36. For example, if the adsorption filter is not available, or if the adsorption filter has failed, or if the adsorption filter is not needed for a particular patient treatment, the three-way valve 34 is switched to direct the dialysate to the bypass flow path 35.

In an alternative embodiment shown in fig. 5 and 6, the adsorption filter 71 is located outside the closed loop dialysate flow path. The hemodialysis system includes a separate closed loop "filter" flow path 57 that is selectively connected to either of the two dialysate reservoirs 17 or 20, and a filter 71 is located in series in the closed loop filter flow path 57. Preferably, the dialysis machine includes an additional fluid pump 58 for pumping contaminated dialysate through the filter flow path and filter 71. Referring to fig. 5 and 6, the preferred filter flow path 57 includes a three-way valve 43 that determines which reservoir is empty of contaminated dialysate. For example, fig. 5 illustrates a three-way valve 43 connecting reservoir 20 to a filter flow path 57 instead of reservoir 17. Fig. 6 illustrates a three-way valve 43 connecting reservoir 17 to a filter flow path 57 instead of reservoir 20. The filter flow path may include a pump 58 or the dialysate may be gravity fed to dispense contaminated dialysate from the reservoir 17 or 20. Further, preferably, the filter flow path 57 includes a pressure sensor 59, a check valve 60, an ammonium sensor 69, and a pH sensor 70.

This embodiment of the hemodialysis machine includes a system for introducing a reagent into the filter flow path. As shown in fig. 5 and 6, the filter flow path 57 may include a first reagent source 61 comprising a salt and a second reagent source 65 comprising a bicarbonate and lactic acid solution. These reagents are introduced into the filter flow path using pumps 62 and 66 and mixers 63 and 67. Preferably, the filter flow path further has: a safety feature in the form of an ammonium sensor 69 to ensure that the filter 71 is not depleted and does not introduce unacceptable ammonium ions into the dialysate; and conductivity sensors 64 and 68 that monitor whether reagents have been properly introduced into the cleaned dialysate to provide the appropriate amount of beneficial ions. Finally, the filter flow path 57 includes a pair of check valves 51 and 52 that are opened or closed to ensure that the now cleaned dialysate is returned to the reservoir from which contaminated dialysate has been emptied.

Fig. 7 illustrates an embodiment of a hemodialysis system in which the system is operated in a single pass mode. Dialysate is introduced into the machine through a fresh dialysate flow path from the dialysate source 46, which is maintained at a desired temperature by the heater 23, to the reservoir 17. For this treatment, the dialysate from the first reservoir 17 is circulated through the dialyzer 8 using pumps 26 and 33. The spent dialysate is then directed to a container for holding wastewater 55, or waste drain. Load cells 81 and 82 and/or level sensor 15 may be provided to measure dialysate source 46 and the resulting wastewater 55. Further, the dialysate flow path can include a flow sensor 25, a pressure sensor 27, and a sample port 79.

Fig. 8 shows yet another embodiment of a hemodialysis system that operates in a recirculation mode in which dialysate flows through the adsorption filter 36 in a closed-loop system. As with the other embodiments, the blood flow path 53 conveys blood to the patient in a closed loop system by connecting to the arterial blood line 1 and the venous blood line 14 to convey blood from the patient to the dialyzer and back to the patient. The dialysate is held in a reservoir 17, the level of the dialysate in the reservoir 17 is measured by the level sensor 15 and the load cell 19, and the temperature of the dialysate is maintained by the heater 23. The dialysate is recirculated through the dialyzer 8 and the adsorption cartridge 36 using pumps 26 and 33. Thereafter, the dialysate is returned to the same reservoir 17 through the dialysate flow path 54.

In the embodiment shown in fig. 8, the dialysate flow path includes a deaerator 80 located downstream of the adsorption filter 36. The adsorption filter 36 in turn has an air inlet with a filter 36a, a pressure sensor and a pump 44. The adsorption regeneration deaeration may be accomplished by passing an air stream (which is substantially free of CO ₂ ) Introduction into the regenerated dialysate through the air inlet is accomplished. Preferably, the pump 44 directs the air flow into the adsorption filter 36 at approximately the same flow rate as the liquid through the dialysate flow path. The combined gas-liquid fluid may then be exposed to a hydrophobic membrane within deaerator 80, wherein the gas may freely leave the system, but the liquid continues to flow through the dialysate flow path.

In the embodiment shown in fig. 8, chemical concentrate sources 48 and 50 are provided that can be added to the fluid exiting the adsorption filter as needed to maintain the proper chemicals in the dialysate. Preferably, the first reagent source 48 comprises a salt and the second reagent source 50 comprises bicarbonate or carbonate and lactate solutions. Chemical concentrate is introduced into the dialysate flow path using chemical concentrate pumps 47 and 49, wherein the cleaning water and chemical concentrate are mixed with mixers 63 and 67. Likewise, the dialysate flow path can include a flow sensor 25, a pressure sensor 27, and a sample port 79. Preferably, the dialysate flow path further comprises a conductivity sensor 41 located between the second mixer 67 and the reservoir 17, and comprises an ammonia sensor 37, a pH sensor 38 and a combined conductivity/temperature sensor 24 located between the reservoir 17 and the dialyzer 8. The control processor is connected to the various sensors and pumps to control the hemodialysis treatment. Referring also to fig. 9-13, the control processor preferably causes the flow of dialysate to be reduced throughout the treatment process, as described below.

Still referring to fig. 1-8, the hemodialysis system preferably has a heater 23 that is heat-conductively coupled to a dialysate flow path or reservoir for heating the dialysate to a desired temperature. For example, in the embodiment shown in fig. 1-6, a single heater 23 is thermally coupled to the dialysate flow path downstream of the two reservoirs (17 and 20). However, hemodialysis may include additional heaters, and one or more of the heaters may be in different locations. For example, in an alternative embodiment, the hemodialysis system includes two heaters, with a single heater thermally coupled to each reservoir. The one or more heaters are preferably electrically activated and include a resistor that generates heat as current passes.

Furthermore, hemodialysis systems have various sensors for monitoring hemodialysis, in particular a dialysate flow path and a blood flow path. To this end, the hemodialysis system preferably has one or more flow sensors 25 connected to the dialysate flow path for detecting fluid flow (volume and/or velocity) within the dialysate flow path. Furthermore, it is preferred that the hemodialysis system comprises one or more pressure or occlusion sensors (9 and 27) for detecting the pressure in the dialysate flow path. Preferably, the hemodialysis system also has one or more sensors for measuring the pressure (4 and 7) and/or the fluid flow 11 within the blood flow path.

Preferably, the hemodialysis system includes temperature sensors (22, 24, and 28) for measuring dialysate temperature throughout the dialysate flow path. Furthermore, the hemodialysis system has a liquid level sensor for detecting the liquid level in the reservoirs (17 and 20). The preferred level sensor may comprise a capacitive fluid level sensor (15 and 18) embodiment, with a level sensor (16 or 19) connected to the processor measuring the weight of each reservoir 17 and 20 and thus the level of the dialysate.

Further, it is preferable that the hemodialysis system includes a blood leak detector 31 that monitors the flow of dialysate through the dialysate flow path and detects whether blood has inappropriately diffused into the dialysate flow path through the semipermeable membrane of the dialyzer.

Preferably, the hemodialysis system also comprises: a first pinch valve 2 connected to the arterial blood line 1 for selectively allowing or blocking blood flow through the arterial blood line; and a second pinch valve 13 connected to the venous blood line 14 for selectively allowing or impeding the flow of blood through the venous blood line. Pinch valves are provided to pinch the arterial blood line 1 and the venous blood line 14 to prevent blood from flowing back into the patient in the event that any sensor detects an unsafe condition. The hemodialysis system also provides additional safety features, including blood line bubble sensors (3 and 12) to detect if a bubble is moving backwards along an arterial line (blood leak sensor 3) or a venous line (blood leak sensor 12). Furthermore, the blood flow path 53 may include a bubble trap 10, the bubble trap 10 having a pressurized air pocket within a plastic housing. The bubbles rise to the top of the bubble trap while blood continues to flow to the lower outlet of the trap. This assembly reduces the risk of air bubbles entering the patient's blood.

In order to control the flow and direction of blood and dialysate through the hemodialysis system, the hemodialysis system includes various fluid valves for controlling the flow of fluid through the various flow paths of the hemodialysis system. The various valves include pinch valves and two-way valves that must be opened or closed, as well as three-way valves that allow dialysate to be transferred as desired through the desired flow path. In addition to the above-mentioned valves, the hemodialysis system also includes a three-way valve 21 at the outlet of the reservoir, which determines from which reservoir (17 or 20) the dialysate flows through the dialyzer 8. The further three-way valve 42 determines to which reservoir the spent dialysis fluid is to be sent. Finally, two-way valves 51 and 52 (which may be pinch valves) are located at the inlet of the reservoirs to allow or block the supply of fresh dialysate to the reservoirs (17 and 20). Of course, those skilled in the art may determine that alternative valves may be employed and the present invention is not intended to be limited to the particular two-way or three-way valves identified.

In addition, the hemodialysis system includes a processor 77 and a user interface (not shown). The processor contains dedicated electronics for controlling the hemodialysis system, including hardware and software, and power management circuitry connected to the pump motor, sensors, valves, and heaters for controlling the normal operation of the hemodialysis system. The processor monitors each of the various sensors to ensure that hemodialysis treatment is performed in accordance with a preprogrammed flow of medical personnel input user interfaces. The processor may be a general purpose computer or microprocessor, including hardware and software that can be determined by one skilled in the art to monitor the various sensors and provide automatic or directional control of the heater, pump, and pinch valves. The processor may be located within the electronics of the circuit board or within the aggregate processing of multiple circuit boards and memory cards.

Also not shown, the hemodialysis system includes a power supply for providing power to the processor, user interface, pump motor, valves, and sensors. The processor is connected by conventional circuitry to dialysis machine sensors including reservoir level sensors (15, 16, 18 and 19), blood leak sensor 31, ammonia sensor 37, pressure and flow sensors (4, 7, 9, 11, 25 and 27), temperature sensors (22, 24 and 28), vascular bubble sensors (3 and 12), pumps (5, 6, 26, 33, 40, 44, 47 and 49) and pinch valves (2 and 13).

In operation, the processor is electrically connected to the first, second and third main pumps (5, 26 and 33) to control the actuation and rotational speed of the pump motor, which in turn controls the pump actuator, which in turn controls the pressure and fluid speed of blood through the blood flow path and the pressure and fluid speed of dialysate through the dialysate flow path. By independently controlling the operation of the dialysate pumps 26 and 33, the processor can maintain, increase, or decrease the pressure and/or fluid flow in the dialysate flow path in the dialyzer. Further, by controlling all three pumps independently, the processor can control the pressure differential across the dialyzer semipermeable membrane to maintain a predetermined pressure differential (zero, positive, or negative), or to maintain a predetermined pressure range. For example, most hemodialysis is performed with zero or near zero pressure differential across the semipermeable membrane, for which purpose the processor can monitor and control the pump to maintain such a desired zero or near zero pressure differential. Alternatively, the processor may monitor the pressure sensor and control the pump motor, and thus the pump actuator, to increase the pressure relative to the dialysate flow path within the dialyzer and maintain the positive pressure in the blood flow path within the dialyzer. Advantageously, the pressure differential may be affected by the processor to provide ultrafiltration and transfer of free water and dissolved solutes from the blood to the dialysate.

In a preferred embodiment, the processor monitors the blood flow sensor 11 to control the blood pump flow. It uses a dialysate flow sensor 25 to control the dialysate flow from the upstream dialysate pump. The processor then uses the reservoir level sensors (15, 16, 18, and 19) to control the flow from the downstream dialysate pump 33. The change in level (or volume) in the dialysate reservoir is the same as the change in patient volume. By monitoring and controlling the liquid level in the reservoir, forward, reverse or zero ultrafiltration can be achieved.

Referring to fig. 3, 4 and 8-13, in the event that the hemodialysis system is operating with the dialysate flowing through the adsorption filter 36 in a closed loop, the dialysate flow preferably decreases throughout the patient treatment period. More specifically, it has been found that if the duration of treatment is increased, more urea can be purged during treatment using the same adsorption cartridge 36. This is illustrated in table 1 below, which table 1 shows that the same spKt/V can be achieved with a lower dialysate flow rate as long as the treatment time is extended. The spkt_/V is a measure of dialysis adequacy based on urea clearance (K) over time (t) and human distributed urea volume (V). KDOQI2015 clinical practice guidelines for hemodialysis adequacy, 3.1, suggests that the minimum Kt/V for three times a week be 1.2. The "sp" portion of the spKt/V stands for "cell", meaning in practice that it is calculated by assuming the human body as if the liquid uniformly contained and released a single volume of urea. Such a measure of dialysis effectiveness is typically related to the initial and final blood urea nitrogen ("BUN") of the dialysis patient, wherein the final BUN is measured immediately after the dialysis is completed. Here, the same spKt/V as the treatment with a dialysate flow of 300 ml/min for 285 minutes can be achieved at 600 ml/min treatment for 240 minutes, wherein the percentage change in spKt/V is measured relative to the baseline number shown in the shaded box. However, during treatment operating at lower dialysate flow rates, the adsorption cartridge 36 is able to or absorbs more urea.

TABLE 1

Furthermore, as seen in the table below, which shows a linear decrease in dialysate flow (e.g., 500-300 ml/min for a 35L distributed urea volume patient), the spKt/V is 1.54. This is similar to 1.57spKt/V at a constant flow rate of 400 ml/min. Similarly, for a dialysate flow rate of 550-250 ml/min for a 35L distributed urea volume patient, the spKt/V is 1.52, which is still similar to 1.57spKt/V at a constant flow rate of 400 ml/min. This tells us that the average value of the dialysate flow is more important than increasing the effect of flow on urea removal.

Table 2: dialysis flow change and urea clearance 240 min treatment, 3L initial volume

But again the adsorption cartridge 36 is capable of absorbing more urea during treatment operating at reduced dialysate flow. It is also important that urea is typically released into the dialysate at the beginning of hemodialysis treatment at a higher level than at the end of the treatment. Therefore, it is preferable to have a higher dialysate flow at the beginning of the treatment. To balance these counteracting effects, it is preferred that the dialysate flow is at a high flow rate at the beginning of the patient treatment, but that the dialysate flow is reduced during the patient treatment.

In addition to optimizing urea removal in the adsorption filter, there are other reasons that can alter dialysate flow during treatment. The desired dialysate volume and treatment time for the treatment can be balanced by varying the dialysate flow rate during the treatment. When the urea concentration is high at the beginning of the treatment, the high dialysate flow rate helps to quickly remove urea from the blood. As the urea concentration decreases, the decreasing flow rate does not excessively change the urea that can be removed from the blood, but the amount of dialysis fluid consumed can be reduced.

To implement a patient treatment plan with reduced dialysate flow, the processor 77 is connected to the dialysate flow sensor 25 to monitor the flow of dialysate and the processor 77 is connected to the dialysate pumps 26 and 33 to control the rate at which the dialysate flows through the dialysate flow path. In addition, processor 77 includes a memory 78, memory 78 storing one or more patient treatment plans for treating the patient. The patient treatment plan includes the desired flow rates at which the dialysate is intended to flow during different times throughout the patient treatment period. As shown in fig. 10-13, dialysate flow decreases during patient treatment according to the patient treatment plan. The decrease in dialysate flow can be incremental as shown in fig. 11. Alternatively, the dialysate flow can be reduced in a linear fashion as shown in fig. 12. In additional alternative treatment plans, the reduction in dialysate flow can be exponential, inverse, polynomial, or other relationships that provide for reducing dialysate flow over time. For example, fig. 12 illustrates an acceptable polynomial treatment regimen in which the rate of change of the reduced flow (delta) is decreasing. In contrast, fig. 13 illustrates an acceptable polynomial treatment regimen, wherein the rate of change of the reduced flow (delta) is increasing.

Specifically, each patient treatment plan includes a total time period "T (total)" for treating the patient, which in turn includes a plurality of time slices including time slice T1, time slice T2, time slice T3, and so on. The patient treatment plan also includes a plurality of flows, including at least a high flow operating during time segment T1. The treatment plan also includes time segment T2, time segment T3, and so on. As will be appreciated by those skilled in the art, the time period of each time segment is considered to be very small in case the decrease in dialysate flow is changed continuously, e.g. in a linear or polynomial manner.

Preferably, the dialysis treatment starts with a higher dialysate flow rate (e.g. between 400 and 800 ml/min) and ends with a lower flow rate between 100 and 500 ml/min. However, dialysis treatment may even begin at a flow rate of greater than 800 ml/min and end at a flow rate of less than 100 ml/min. More preferably, the dialysis treatment starts with a higher dialysate flow rate of between 450 and 800 ml/min and ends with a lower flow rate of between 100 and 450 ml/min. However, another patient may require a different treatment regimen. For example, in another preferred embodiment, the patient treatment plan lasts four hours and starts treatment at a dialysate flow rate of about 400 to 600 ml/min and decreases linearly until ending at a flow rate of between 200 to 300 ml/min.

In the preferred embodiment shown in fig. 10-13, the patient treatment plan begins treatment at a dialysate flow rate of about 500 ml/min and drops linearly over two hours until ending at a flow rate of 250 ml/min. However, the treatment regimen may be different, such as a linear decrease (as shown in fig. 10) or a stepwise decrease (as shown in fig. 11). For example, for the embodiment shown in fig. 11, the patient is initially treated with a high dialysate flow rate (illustrated as 500 ml/min) of greater than 450 ml/min for a time period T1 of 1.0 hour, with an intermediate flow rate between 450-400 ml/min (illustrated as 417 ml/min) for a second time period T2 of 1.0 hour, with an intermediate flow rate between 350-300 ml/min (illustrated as 333 ml/min) for a third time period T3 of 1.0 hour, and with a low flow rate between 300-200 ml/min (illustrated as 250 ml/min) for a final time period T4 of 1.0 hour. In the alternative, to decrease the flow rate stepwise or linearly, the decrease in flow rate may decrease over time (- Δ) as shown in fig. 12, or the decrease in flow rate may increase over time (+Δ) as shown in fig. 13. For each of these examples shown in fig. 10-13, the dialysate flow starts at about 500 ml/min and drops for 4 hours until ending at a flow of 250 ml/min. In addition to the different methods of reducing dialysate flow, the total treatment time T (total) of the patient treatment plan can be determined on a per patient basis (e.g., 2-8 hours), as can the high flow (e.g., 800-400 ml/min) and low flow (500-200 ml/min).

To maintain proper treatment of the patient, the processor monitors all of the various sensors to ensure that the hemodialysis machine is operating effectively and safely, and in the event an unsafe or unspecified condition is detected, the processor corrects the defect or stops further hemodialysis treatment. For example, if venous blood line pressure sensor 9 indicates unsafe pressure or bubble sensor 12 detects a bubble in the venous blood line, the processor issues an alarm signal, deactivates the pump, and closes the pinch valve to prevent further blood flow back into the patient. Similarly, if the blood leak sensor 31 detects that blood has permeated the semipermeable membrane of the dialyzer, the processor issues an alarm and stops further hemodialysis treatment.

The user interface of the dialysis machine can include a keyboard or touch screen (not shown) for enabling the patient or medical personnel to enter commands regarding the treatment or for enabling the patient or medical personnel to monitor the performance of the hemodialysis system. Further, the processor may include a Wi-Fi or bluetooth connection for transmitting information or control to a remote location.

Hereinafter, the various components of the preferred hemodialysis system will be identified with reference numerals corresponding to the components shown in the figures.

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Hemodialysis systems provide increased treatment options based on the desired dialysis frequency, patient characteristics, dialysate or water availability, and desired portability of the dialysis machine. For all treatments, the blood flow path 53 delivers blood to the patient in a closed loop system by connecting to the arterial blood line 1 and the venous blood line 14 to deliver blood from the patient to the dialyzer and back to the patient.

Referring to fig. 2, the first method of using a hemodialysis system does not require the use of an adsorption filter 36. Water is introduced into the machine from a water source 46, such as water supplied by Reverse Osmosis (RO), through a fresh dialysate flow path 56. Chemical concentrates 48 and 50 are added to the cleaning water using chemical concentrate pumps 47 and 49, if desired. The mixed dialysate is then introduced into reservoirs 17 and 20. For this treatment, dialysate 75 from the first reservoir is recirculated through bypass path 35 through dialyzer 8 back to the same reservoir. When the volume of the reservoir has been recirculated once, the reservoir is emptied via the drain path 55 and refilled via the fresh dialysate flow path 56.

At the same time, hemodialysis treatment is continued using the second reservoir (17 or 20) while the first reservoir is emptied and refilled. As shown in fig. 2, once the processor determines that all of the dialysate has been recirculated once, or that the dialysate is contaminated, the processor switches all of the associated valves (21, 42, 43, 51 and 52) to remove the first reservoir 20 from patient treatment and inserts the second reservoir 17 into the dialysate flow path 54. Dialysate 75 from the second reservoir 17 is recirculated through the bypass path 35 through the dialyzer 8 and back to the same reservoir 17. This switching back and forth between reservoirs 17 and 20 continues until the dialysis treatment is completed. This operation is similar to a conventional single pass system but differs in that no adsorption filter is used.

In a second embodiment shown in fig. 3, the adsorption cartridge 36 filters the dialysate after it has passed through the dialyzer 8. To this end, the processor switches the three-way valve 34 to incorporate the adsorption cartridge 36 into the dialysate flow path 54, and the processor switches the various valve assemblies (21, 42, 43, 51 and 52) to utilize the reservoir 17 during the dialysis treatment. The clean dialysate 75 is recirculated through the dialyzer 8 and the adsorption cartridge 36, and then the dialysate is returned to the same reservoir 17 through the dialysate flow path 54. This recirculation continues as determined by the processor (including, but not limited to, because the adsorption cartridge has failed, or the dialysate is contaminated, or ultrafiltration has caused the reservoir 17 to become full and require emptying and refilling). Meanwhile, in the event that the fluid in reservoir 20 is contaminated, it is discharged through drain path 45 and then reservoir 20 is refilled with fresh dialysate flow path 56.

As shown in fig. 4, once it is determined that the processor is not suitable to continue using the reservoir 17 for dialysis treatment, the processor switches the various valve assemblies (21, 42, 43, 51, and 52) to remove the reservoir 17 from the dialysis flow path 54, but rather inserts the reservoir 20 into the dialysis flow path for dialysis treatment. The clean dialysate 75 is recirculated back to the same reservoir 20 through the dialyzer 8 and the adsorption filter 36. Again, this recirculation continues using reservoir 20 as determined by the processor until switching back to reservoir 17, or until the dialysis treatment is completed. While continuing the dialysis treatment using reservoir 20, contaminated fluid 76 in reservoir 17 is discharged through the drain path. Thereafter, the reservoir 17 is refilled using the fresh dialysate flow path 56. As with other treatments, this switching back and forth between reservoirs 17 and 20 continues until the dialysis treatment is completed.

In yet another embodiment illustrated in fig. 5 and 6, hemodialysis treatment is performed in a similar manner as shown in fig. 2, wherein the adsorption filter 36 is not used within the dialysate flow path 54. Although the filter 36 may be used within the dialysate flow path 54, it is preferred for this embodiment that the dialysate 75 is directed through the bypass path 35 so as to avoid the adsorption filter 36. During treatment, dialysate 75 from the first reservoir is recirculated through the bypass path 35 through the dialyzer 8 and directed back to the same reservoir. For this embodiment, even more preferably, the hemodialysis system does not include an adsorption filter 36. In contrast, referring to fig. 5 and 6, the hemodialysis system includes a single adsorption filter 71, which filter 71 is located within a separate closed-loop flow path, referred to herein as filter flow path 57. Although fig. 5 and 6 illustrate a hemodialysis system that includes two adsorption filters 36 and 71, the adsorption filter 36 within the dialysate flow path 54 is optional and need not be incorporated in this embodiment of the hemodialysis system.

As in the previous embodiments, dialysis treatment is achieved while switching back and forth between reservoirs 17 and 20. Referring to fig. 5, when the dialysis treatment uses the clean dialysate 75 in the reservoir 17, the various valve assemblies (21, 42, 43, 51 and 52) are switched to insert the second reservoir 20 into the closed-loop filter flow path 57. Sewage 76 is discharged from reservoir 20 by pump 58 and pressure sensor 59. Thereafter, the sewage 76 is filtered through the adsorption filter 71. Gravity feed or pumps 62 and 66 may be used to introduce reagents 61 and 65 into the filter flow path. The reagents are mixed in mixers 63 and 67 and then tested for compliance by conductivity testers 64 and 68, ammonium sensor 69 and pH sensor 70 for the now cleaned dialysate. If the test indicates that the water is now clean, it is directed back to the reservoir 20.

Referring to fig. 6, the processor continues to monitor the output of various sensors, including those within the dialysate flow path 54. Once the water in the reservoir 17 is contaminated, it is removed from the dialysate flow path and the reservoir 20 is replaced by switching again all relevant valve assemblies (21, 42, 43, 51 and 52). Dialysate 75 from the second reservoir 20 is recirculated through the dialyzer 8 in the closed loop dialysate flow path 54 and directed back to the same reservoir. At the same time, the now-existing sewage 76 in the reservoir 17 is discharged through the pump 58 and the pressure sensor 59 before being filtered through the adsorption filter 71. Likewise, reagents 61 and 65 may be introduced into the filter flow path 57, where the reagents are mixed in mixers 63 and 67. The now cleaned dialysate is tested for compliance by conductivity testers 64 and 68, ammonium sensor 69 and pH sensor 70 before filling reservoir 17. This process of alternating reservoirs continues until a prescribed hemodialysis treatment is completed or a failure is detected that requires cessation of treatment.

Similar to the embodiments shown in fig. 2, 3, 5 and 6, the embodiment shown in fig. 7 may operate in a single pass mode. Dialysate is introduced into the machine through a fresh dialysate flow path from the dialysate source 46 to the reservoir 17, through which the dialysate source 46 flows to the dialyzer 8. Thereafter, the spent dialysate is then directed to a container 55 for holding wastewater, or a sewage drain. Although the use of an adsorption filter is not required, this single pass mode typically requires 400-600 liters of water.

Conversely, the embodiment of the hemodialysis system shown in fig. 8 can be operated in a closed loop recirculation mode, wherein dialysate flows through the adsorption filter 36. The dialysate is held in reservoir 17 and recirculated through dialyzer 8 and adsorption cartridge 36. Chemical concentrates 48 and 50 are added to the filtered water as needed. Recirculation continues as determined by the processor until the process is complete, the cartridge has failed, the dialysate is contaminated or ultrafiltration has resulted in the reservoir 17 becoming full and requiring emptying and refilling.

Finally, with respect to the exemplary embodiments of the present invention as shown and described herein, it should be understood that a hemodialysis system is disclosed. The principles of the present invention may be practiced in a variety of configurations beyond those shown and described, and it is therefore to be understood that the invention is not limited to any of the exemplary embodiments, but is generally directed to hemodialysis systems and is capable of taking a variety of forms without departing from the spirit and scope of the present invention. It will also be appreciated by those of skill in the art that the invention is not limited to the particular geometries and materials of construction disclosed, but may require other functionally equivalent structures or materials now known or later developed without departing from the spirit and scope of the invention. Furthermore, the various features of each of the embodiments described above may be combined in any logical manner and are intended to be included within the scope of the present invention.

The grouping of alternative embodiments, elements or steps of the present invention should not be construed as limiting. Each group member may be referred to and claimed either alone or in any combination with other group members disclosed herein. For convenience and/or patentability reasons, it is contemplated that one or more members of a group may be included in or deleted from a group. When any such inclusion or deletion occurs, the specification is considered to contain the modified group.

Unless otherwise indicated, all numbers expressing features, articles, amounts, parameters, properties, times, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". As used herein, the term "about" refers to a range of plus or minus 10% of the value of a feature, item, quantity, parameter, property, or term so defined, above and below that feature, item, quantity, parameter, property, term. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical indication should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and values setting forth the broad scope of the invention are approximations, the numerical ranges and values set forth in the specific examples are reported as precisely as possible. Any numerical range or value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value of a numerical range is incorporated into the specification as if it were individually recited herein.

The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

The specific embodiments disclosed herein may be further limited to the use of claims that consist or consist essentially of the language. As used in a claim, the transitional term "consisting of … …" does not include any element, step or component not specified in the claim, whether submitted or added upon modification. The transitional term "consisting essentially of … …" limits the scope of the claims to materials or steps specified, as well as those that do not materially affect the basic and novel characteristics. The embodiments of the invention so claimed are inherently or explicitly described and enabled herein.

It should be understood that the logic code, programs, modules, processes, methods, and the order in which the individual elements of each method are performed are purely exemplary. Depending on the embodiment, they may be performed in any order or in parallel unless otherwise indicated in this disclosure. Furthermore, the logic code is not related or limited to any particular programming language and may include one or more modules executing on one or more processors in a distributed, non-distributed, or multi-processing environment.

While several particular forms of the invention have been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, the invention is not intended to be limited, except as by the following claims.

Claims (7)

1. A hemodialysis system with variable flow comprising:

a machine housing;

an arterial blood line for connecting an artery of a patient to collect blood from the patient;

a venous blood line for connecting a patient's vein to return blood to the patient;

a dialyzer;

a blood flow path connected to the arterial blood line and the venous blood line for transporting blood from the patient to the dialyzer and back to the patient;

A reservoir for holding a dialysate;

a dialysate flow path isolated from the blood flow path, connected to the reservoir and the dialyzer, for transporting dialysate from the reservoir to the dialyzer;

at least one dialysate pump for pumping dialysate through the dialysate flow path;

a blood pump for pumping blood through the blood flow path;

a dialysate flow sensor in the dialysate flow path that measures a flow rate of dialysate passing through the dialysate flow path;

a control processor connected to the dialysate flow sensor and the at least one dialysate pump, the control processor having a memory for storing a patient treatment plan by which a patient is treated, the patient treatment plan including dialysate flow during patient treatment, wherein dialysate flow decreases during a time period "T (total)" when the patient is treated.

2. The hemodialysis system of claim 1, wherein the dialysate flow comprises a high flow and a low flow, and wherein the low flow is less than 75% of the high flow.

3. The hemodialysis system with variable flow of claim 1, wherein the patient treatment plan includes decreasing dialysate flow in a linear manner.

4. The hemodialysis system of claim 1, wherein the dialysate flow is stepped down and comprises a high flow and a low flow.

5. The hemodialysis system of claim 1, wherein the dialysate flow rate includes a high flow rate of between 400 and 800 ml/min and a low flow rate of between 100 and 400 ml/min.

6. The hemodialysis system of claim 1, wherein the control processor causes the dialysate pump to pump dialysate through the dialysate flow path at a flow rate of between 400 and 800 milliliters per minute for at least 0.5 hours, and the control processor causes the dialysate pump to pump dialysate through the dialysate flow path at a rate of between 100 and 400 milliliters per minute for at least 0.5 hours.

7. The hemodialysis system with variable flow of claim 1, further comprising an adsorption filter connected to the dialysate flow path for removing uremic toxins from dialysate.