Dialysis system with thermoelectric heating

Abstract

The medical fluid system includes a medical fluid pump configured to pump a medical fluid; electronics associated with the medical fluid pump or other components of the medical fluid system; a thermoelectric heater positioned and arranged to heat the medical fluid pumped by the medical fluid pump, the thermoelectric heater including a heated side and a cooled side; a heat exchanger through which the medical fluid pumped by the medical fluid pump is heated, the heat exchanger positioned and arranged in thermal communication with the heated side of the thermoelectric heater; and a mounting plate, the electronics supported by the mounting plate and positioned and arranged in thermal communication with the cooled side of the thermoelectric heater.

Description

[Technical field]

[0001] (Related Applications) This application claims priority to U.S. Provisional Patent Application No. 63 / 323,334, entitled "DIALYSIS SYSTEM HAVING THERMOELECTRIC HEATING," filed March 24, 2022, the entire contents of which are incorporated herein by reference and relied upon. [Background technology]

[0002] FIELD OF THE DISCLOSURE The present disclosure relates generally to medical fluid treatments, and more particularly to dialysis fluid treatments that require fluid heating.

[0003] Due to a variety of causes, a person's renal system can fail. Renal failure results in several physiological disorders: it is no longer possible to balance fluid and minerals or to excrete the daily metabolic load. Toxic end products of metabolism such as urea, creatinine, uric acid, and others can accumulate in the patient's blood and tissues.

[0004] Reduced kidney function, especially kidney failure, is treated with dialysis. Dialysis removes waste products, toxins, and excess water from the body that normally functioning kidneys would otherwise remove. Dialysis treatment for replacement of kidney function is important for many people because the treatment is life-saving.

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

[0006] Hemofiltration ("HF") is an alternative renal replacement therapy that relies on convective transport of toxins from the patient's blood. HF is accomplished by adding a substitute or replacement fluid to the extracorporeal circuit during treatment. The substitute fluid, and fluid accumulated by the patient during treatment, is ultrafiltered over the course of HF treatment, providing a convective transport mechanism that is particularly beneficial in removing medium and large molecules.

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

[0008] Most HD, HF, and HDF treatments occur in a facility. Today, there is a trend toward home hemodialysis ("HHD"), in part because HHD can be performed daily and provides therapeutic benefits over in-center hemodialysis treatments, which typically occur two or three times a week. Studies have shown that more frequent treatments remove more toxins and waste products and result in less interdialytic fluid overload than patients who receive less frequent, but perhaps longer, treatments. Patients who receive more frequent treatments do not suffer as much downcycling (fluctuations in fluids and toxins) as in-center patients who build up two or three days' worth of toxins prior to treatment. In some areas, the nearest dialysis facility is many miles away from the patient's home, causing round-trip treatment times to consume a large portion of the patient's day. In-center treatments closer to the patient's home may also consume a large portion of the patient's day. HHD may occur over the night or during the day while the patient is relaxing, working, or otherwise productive.

[0009] Another type of renal failure therapy is peritoneal dialysis ("PD"), in which a dialysis solution, also called dialysis fluid, is infused through a catheter into a patient's peritoneal cavity. The dialysis fluid contacts the peritoneal membrane within the patient's peritoneal cavity. Waste, toxins, and excess water pass from the patient's bloodstream through capillaries in the peritoneal membrane into the dialysis fluid due to diffusion and osmosis, i.e., an osmotic gradient is created across the membrane. Osmotic agents in the PD dialysis fluid provide the osmotic gradient. The used, or spent, dialysis fluid is pumped out of the patient, removing the waste, toxins, and excess water from the patient. This cycle is repeated, for example, multiple times.

[0010] 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, allowing used, i.e., spent, dialysis fluid to be drained from the peritoneal cavity. The patient then switches the fluid communication so that the patient catheter is in communication with a bag of fresh dialysis fluid and infuses the fresh dialysis fluid through the catheter and into the patient. The patient disconnects the catheter from the fresh dialysis fluid bag, allowing the dialysis fluid to dwell in the peritoneal cavity, resulting in the transport of waste, toxins, and excess water. After a dwell period, the patient repeats the manual dialysis procedure, for example, four times per day. Manual peritoneal dialysis requires a significant amount of time and effort from the patient, leaving ample room for improvement.

[0011] Automated peritoneal dialysis ("APD") is similar to CAPD in that the dialysis treatment includes drain, fill, and dwell cycles. However, APD machines typically perform the cycles automatically while the patient sleeps. APD machines relieve the patient from the need to manually perform the treatment cycles and from the need to transport consumables during the day. APD machines fluidly connect to an implanted catheter, to a source or bag of fresh dialysis fluid, and to a fluid drain. The APD machine pumps fresh dialysis fluid from the dialysis fluid source, through the catheter, and into the patient's peritoneal cavity. APD machines also allow the dialysis fluid to dwell in a chamber, allowing transport of waste, toxins, and excess water to occur. The source may contain several liters of dialysis fluid, including several solution bags.

[0012] APD machines pump used, or spent, dialysate from the patient's peritoneal cavity, through a catheter, and to a drain. As with the manual process, several drain, fill, 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 cavity until the start of the next treatment, or may be manually emptied at some point during the day.

[0013] Each of the above identified dialysis modalities, except for CAPD (which typically does not involve machinery), heats the dialysis fluid prior to use to treat a patient. On-line HD, on-line HF, and on-line HDF each prepare the associated dialysis and / or substitution fluid in a corresponding machine, which is heated by an in-line heater prior to delivery to the dialysis machine or blood line. Acute HD, HF, and HDF, performed in a continuous renal replacement ("CRRT") machine, typically employ bagged dialysis and substitution fluids, which are nevertheless heated by an in-line heater prior to delivery to the dialysis machine or blood line.

[0014] APD systems in many instances use batch heating of the PD fluid prior to delivery to the patient. However, it is known to use in-line heating for APD. One such system is described in U.S. Patent No. 7,153,285, entitled "Medical Fluid Heater Using Radiant Energy," which is assigned to the assignee of the present disclosure.

[0015] In-line heating and associated heaters have several disadvantages. In-line heaters can be expensive, require large printed circuit control boards, and require a large internal space so that the heat produced by the heater does not overheat the surrounding electronics. The larger internal volume can adversely affect the design and size of the machine, its usability for travel, storage, and shipping costs. The heat generated by in-line heaters can also require the dialysis machine to be equipped with vents, creating openings for dust and insects to enter. The heat generated can also require the use of high temperature grade components, which increases the cost of the dialysis machine. Additionally, the expected life of the associated and surrounding electronics decreases with increased ambient temperatures.

[0016] Improved methods for heating the different dialysis treatment fluids and any of the other medical fluids described herein are therefore needed. Summary of the Invention [Means for solving the problem]

[0017] The present disclosure describes medical fluid systems, such as automated peritoneal dialysis ("APD") systems, that provide improved dialysis fluid heating. Although the present systems are primarily described in connection with peritoneal dialysis, the improved dialysis fluid heating of the present disclosure applies to machines used for any of the dialysis modalities described herein, such as online HD, HF, HDF, and acute HD, HF, HDF, etc. The improved medical fluid heating of the present disclosure also applies to any medical fluid system in which therapy or patient fluids are heated (e.g., patient blood warming).

[0018] In an APD embodiment, the system includes a PD machine or cycler. The PD machine can deliver fresh heated PD fluid to the patient, for example at 14 kPa (2.0 psig) or higher. The PD machine can remove used PD fluid or waste fluid from the patient at a negative pressure, for example at -9 kPa (-1.3 psig) or even higher. The resulting PD fluid flow rate to or from the patient depends on several factors, including the height at which the patient is positioned relative to the pumping portion of the PD machine, the patient's sleep position (assuming overnight treatment), and the amount of waste fluid remaining in the patient's peritoneal cavity relative to the patient drain. Fresh PD fluid delivered to the patient is first heated to body fluid temperature, for example 37°C.

[0019] The PD machine of the disclosed system employs a thermoelectric heater, which may employ, for example, a Peltier module. The thermoelectric heater is considered a Class II device, and the Peltier module is electrically insulated, for example, via a ceramic plate. The thermoelectric heater may form a solid-state active heat pump that transfers heat from one side of the heater element to the other, creating a heated side and a cooled side, depending on the consumption of electrical energy. The heated and cooled sides are determined by the direction of the electrical current flowing through the thermoelectric heater.

[0020] The heated side of the thermoelectric heater is used to heat the dialysis fluid prior to use for treatment, while the cooled side, in one embodiment, is placed in close proximity to the electronic components of the PD machine to help keep those components cool. As discussed in detail herein, the heated side, in one embodiment, is placed in direct thermal contact with a heat exchanger that carries the medical fluid to be heated, e.g., PD fluid. Heat is exchanged from the heated side of the thermoelectric heater to the PD fluid flowing through the heat exchanger. In one embodiment, the cooled side of the thermoelectric heater is mounted to one or more mounting plates for the surrounding electrical components. The material of the one or more mounting plates may be selected for its ability to conduct thermal energy well, such as aluminum, since it does not contact the medical fluid. The electrical components that would benefit most from thermoelectric refrigeration, e.g., medical or dialysis fluid pumps, medical fluid valves, and associated electronics, are mounted to the one or more mounting plates. One or more heat fins may be provided extending from the one or more mounting plates for convective cooling of electrical components that cannot be mounted to the one or more mounting plates. The one or more cooled heat fins receive convective heat from adjacent electrical components via air circulation therebetween. If desired, a fan may be provided to help transfer heat from the electrical components to the one or more heat fins.

[0021] Cooling electronics also allows lower rated and less expensive electrical components to be used. In some embodiments, lower temperature rated electrolytic capacitors may be used when cooling electronics, lowering component costs. In addition, cooling electronics extends the life of electrical components. One accepted industry rule for electrolytic capacitors (and semiconductors as well) is that for every 10° C. increase in temperature, component life is reduced by half.

[0022] In addition to component cooling by the cooled side, the energy flow (Qh) associated with the heated side of the thermoelectric heater can be modeled as the energy flow on the cooled side (Qc) plus the power added to the module, i.e., the voltage supplied times the current supplied (V×I). The heated side energy flow (Qh) used to heat the PD fluid therefore exceeds the power added to the module (V×I) by the amount of cooled side energy flow (Qc), which is relatively large at the beginning of a medical fluid heating session, which gradually drops until the temperature difference between the heated and cooled sides becomes too large and Qc drops to zero.

[0023] One exemplary Peltier module that can be used with the thermoelectric heater of the present disclosure can handle a heated side to cooled side temperature difference of 75° C., meaning that Qc will be above zero as long as the source (cooled side) from which energy is removed is greater than the medical or dialysis fluid temperature exiting the heat exchanger. The PD fluid temperature exiting the heat exchanger, in one embodiment, is body fluid temperature, e.g., 37° C., such that additional heat (Qc) from the cold side is provided as long as the cold side remains warmer than −38° C., which is highly likely, especially considering that the cold side exchanges heat with surrounding electrical components, cooling such components.

[0024] The solid-state nature of the thermoelectric heater of the present disclosure provides a quiet solution since there is no internal switching. Powering the thermoelectric heater is also advantageous since the heater uses direct current ("DC") power, which may be supplied by a backup battery instead of or in addition to DC power from the main power supply. Battery power may be provided in addition and intermittently, for example, during maximum power consumption and high heating power modes, so as not to overload the main power supply. Clean DC power also reduces electromagnetic interference ("EMI") and radio frequency ("RF") noise compared to 115 / 230VAC heater elements. Even if a pulse width modulation ("PWM") driver is used to drive the thermoelectric heater, as envisioned, EMF and RF noise are lower due to switching at significantly lower voltages. The use of DC power also reduces leakage currents and flicker because the power is gradually controlled and large resistive loads are not switched on and off, as is the case with many resistive in-line heaters.

[0025] Also, the polarity of the power delivered to the thermoelectric heater may be reversed so that when the cooled side temperature approaches a temperature that is considered too low, such as the dew point temperature, the goal here is to prevent condensation from forming on the cold side of the module. To this end, an inexpensive humidity / temperature sensor integrated circuit may be provided on a printed circuit board on the control unit of the system, the sensor and integrated circuit configured to calculate the dew point temperature. Another reason for switching the polarity, and therefore the heated and cooled sides of the thermoelectric heater, is in the case of a no medical fluid flow situation, where the polarity is reversed to avoid medical fluid overheating and reduce the amount of medical fluid wasted.

[0026] It is contemplated to use the thermoelectric heater of the present disclosure as a replacement for a typical resistive in-line heater. It is also contemplated to use the thermoelectric heater in combination with a smaller typical resistive in-line heater, which mitigates its shortcomings, such as heater cost, heat generation, spacing requirements, and expensive electrical components. In an embodiment, the thermoelectric heater is placed upstream of the smaller resistive in-line heater so that the thermoelectric heater is maximized. The smaller resistive in-line heater may then be used more or less as a backup heater, providing any heating delta required for the medical or dialysis fluid to reach a desired treatment temperature only as needed. However, it is also expressly contemplated to reverse the order of the thermoelectric heater and the smaller resistive in-line heater, such that the resistive heater is placed upstream of the thermoelectric heater and the polarity of the thermoelectric heater is reversed, for example, to cool the overheated medical fluid exiting the resistive heater.

[0027] In light of the disclosure described herein, which may be combined with any other aspect or portion thereof without limiting the disclosure in any way, a medical fluid system includes a medical fluid pump configured to pump a medical fluid; a thermoelectric heater positioned and arranged to heat the medical fluid pumped by the medical fluid pump, the thermoelectric heater including a heated side and a cooled side, a heat exchanger through which the medical fluid pumped by the medical fluid pump is heated, the heat exchanger positioned and arranged in thermal communication with the heated side of the thermoelectric heater, and a mounting plate, where the medical fluid pump or other components of the medical fluid system are supported by the mounting plate and positioned and arranged in thermal communication with the cooled side of the thermoelectric heater.

[0028] In a second aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the heat exchanger in thermal communication with the heated side of the thermoelectric heater includes directly contacting the heated side.

[0029] In a third aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a heat exchanger includes a conductive heat exchanger block and a conductive serpentine path supported by the conductive heat exchanger block.

[0030] In a fourth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the conductive heat exchanger block is made from aluminum or copper and the conductive serpentine path is made from stainless steel.

[0031] In a fifth aspect of the present disclosure that may be combined with any other aspect or portion thereof, a medical fluid system includes a temperature sensor located on or inside a conductive heat exchanger block.

[0032] In a sixth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the mounting plate being in thermal communication with the cooled side of the thermoelectric heater includes being in direct contact with the cooled side.

[0033] In a seventh aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the medical fluid pump or other component of the medical fluid system being supported by a mounting plate includes the medical fluid pump or other component of the medical fluid system being mounted to the mounting plate.

[0034] In an eighth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the other components include at least one of (i) at least one valve, (ii) at least one temperature sensor, (iii) at least one pressure sensor, or (iv) a flow sensor or flow switch, and electronics associated with the other components.

[0035] In a ninth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a medical fluid system includes at least one heat pipe extending from at least one of the medical fluid pumps or other components of the medical fluid system to a mounting plate for conducting heat to the mounting plate.

[0036] In a tenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a mounting plate is attached or formed to have at least one thermal fin for convectively transferring heat from at least one component of the medical fluid system to the mounting plate, the at least one component being located adjacent to the at least one thermal fin.

[0037] In an eleventh aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a medical fluid system includes at least one fan positioned and arranged to blow air between at least one thermal fin and at least one convection cooling component of the medical fluid system.

[0038] In a twelfth aspect of the present disclosure that may be combined with any other aspect or portion thereof, a thermoelectric heater includes a plurality of semiconductors extending between a heated side and a cooled side.

[0039] In a thirteenth aspect of the present disclosure that may be combined with any other aspect or portion thereof, a medical fluid system includes a plurality of conductive leads positioned between a plurality of semiconductors and a heated and cooled side.

[0040] In a fourteenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the plurality of conductive leads are positioned and arranged such that the plurality of semiconductors operate electrically in series.

[0041] In a fifteenth aspect of the present disclosure that may be combined with any other aspect or a portion thereof, the multiple semiconductors operate in thermal parallel.

[0042] In a sixteenth aspect of the present disclosure that may be combined with any other aspect or portion thereof, a medical fluid system includes a resistive in-line heater located in fluid series with a thermoelectric heater.

[0043] In a seventeenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a medical fluid system includes a control unit, wherein the thermoelectric heater and the resistive in-line heater are under the control of the control unit, and the control unit is configured to power the resistive in-line heater as needed to assist the thermoelectric heater in heating the medical fluid to a desired temperature.

[0044] In an eighteenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a medical fluid system includes a control unit, the control unit configured to reverse the polarity of power to the thermoelectric heater so that the heated side becomes the cooled side of the thermoelectric heater, and a heat exchanger is then positioned and arranged to be in thermal communication with the cooled side.

[0045] In a nineteenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the medical fluid system includes a humidity sensor positioned and arranged to measure humidity adjacent to the mounting plate, and the control unit is further configured to use an output from the humidity sensor to determine when to reverse the polarity of power to the thermoelectric heater to prevent the mounting plate from reaching a dew point temperature.

[0046] In a twentieth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a method for heating a medical fluid includes supplying electrical energy to a thermoelectric heater to create a heated side and a cooled side of the thermoelectric heater, the thermoelectric heater being provided as part of a medical fluid machine; positioning a heat exchanger such that medical fluid flowing through the heat exchanger receives heat from the heated side of the thermoelectric heater; and positioning at least one component of the medical fluid machine such that heat generated by the at least one component is received by the cooled side of the thermoelectric heater, the heat received by the cooled side of the thermoelectric heater being added to the heat available in the heated side of the thermoelectric heater generated via the supply of electrical energy.

[0047] In a twenty-first aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a medical fluid transfer heat exchanger is provided as part of a reusable or disposable medical fluid transfer set.

[0048] In a twenty-second aspect of the present disclosure, which may be combined with any other aspect or portion thereof, positioning the heat exchanger includes positioning the heat exchanger within a medical fluid machine or as part of a working surface of the medical fluid machine.

[0049] In a twenty-third aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a method of heating a medical fluid includes reversing polarity of electrical energy to a thermoelectric heater and reversing the heated and cooled sides of the thermoelectric heater, wherein the medical fluid flowing within the heat exchanger delivers heat to the cooled side of the thermoelectric heater.

[0050] In a twenty-fourth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, any of the features, functionality, and alternatives described in connection with any one or more of Figures 1-3 may be combined with any of the features, functionality, and alternatives described in connection with any other of Figures 1-3.

[0051] In light of the above aspects and the present disclosure described herein, it is an advantage of the present disclosure to provide a medical fluid heating system with thermoelectric cooling.

[0052] Another advantage of the present disclosure is to provide a medical fluid heating system that reduces electrical component damage due to overheating via heat from the medical fluid heater, reduces thermal stresses through a more uniform temperature profile for the electrical components over the course of treatment and post-treatment disinfection, and helps extend the mean time between failures ("MTBF") of the electrical components.

[0053] A further advantage of the present disclosure is to provide a medical fluid heating system that is capable of cooling surrounding electrical components, which improves component reliability and in some cases allows less expensive electrical components to be used.

[0054] Moreover, an advantage of the present disclosure is to provide a medical fluid heating system that is capable of using heat from surrounding electronics to increase the heating potential of the medical fluid heater.

[0055] Yet another advantage of the present disclosure is providing a medical fluid heating system that operates quietly.

[0056] A still further advantage of the present disclosure is to provide a medical fluid heating system that is capable of switching the heated and cooled sides of the thermoelectric heating module in the event of a no medical fluid flow situation, avoiding medical fluid overheating and reducing the amount of wasted medical fluid.

[0057] A still further advantage of the present disclosure is to provide a medical fluid heating system that reduces at least one of electromagnetic interference ("EMI"), radio frequency ("RF") noise, leakage currents, and flicker relative to that produced by VAC voltage resistive heater elements.

[0058] Additional features and advantages will be described in and become apparent from the following detailed description and figures. The features and advantages described herein are not exhaustive, and many additional features and advantages will become apparent to those skilled in the art, particularly in light of the figures and description. Also, any particular embodiment need not have all of the advantages enumerated herein, and each advantageous embodiment is expressly contemplated to be separately claimed. Furthermore, it should be noted that the language used in this specification has been selected primarily for readability and instructional purposes, and is not intended to limit the scope of the inventive subject matter. [Brief description of the drawings]

[0059] [Figure 1]FIG. 1 is a fluid flow schematic of one embodiment of a medical fluid, eg, PD fluid, system having thermoelectric heating of the present disclosure.

[0060] [Diagram 2] FIG. 2 is an elevational view showing the inside of a medical fluid, eg, PD fluid, machine having an embodiment for employing thermoelectric heating of the present disclosure.

[0061] [Diagram 3] FIG. 3 is a perspective view of one embodiment for a medical fluid transport heat exchanger usable with the thermoelectric heating of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] Detailed Description Referring now to the drawings, and in particular to FIG. 1 , an exemplary medical fluid system that may employ thermoelectric heating of the present disclosure is illustrated by a peritoneal dialysis ("PD") system 10. System 10 includes a PD machine or cycler 20 and a control unit 100 having one or more processors 102, one or more memories 104, a video controller 106, and a user interface 108. The control unit 100 controls all electrical fluid flow and heating components of system 10 and receives outputs from all sensors of system 10. System 10, in the illustrated embodiment, includes durable and reusable components that come into contact with medical fluids, such as PD fluids, which necessitates that the PD machine or cycler 20 be sanitized between treatments, for example, via thermal disinfection.

[0063] System 10 in FIG. 1 includes an in-line thermoelectric heater 150 (discussed in detail below), reusable supply lines or tubes 52a1-52a4 and 52b, an air trap 60 in conjunction with separate upper and lower level sensors 62a and 62b, an air trap valve 54d, a vent valve 54e located along vent line 52e, reusable line or tubing 52c, a dialysis fluid pump 70, temperature sensors 58a and 58b, reusable line or tubing 52d, and a pressure sensor 78. a, 78b1, 78b2, and 78c, reusable patient tubing or lines 52f and 52g with respective valves 54f and 54g, a dual lumen reusable patient line 28, a hose reel 80 for retracting the patient line 28, reusable drain tubing or line 52i extending to drain line connector 34 and having drain line valve 54i, and reusable recirculation disinfection tubing or lines 52r1 and 52r2 in conjunction with respective disinfection valves 54r1 and 54r2. A third recirculation or disinfection tubing or line 52r3 extends between disinfection connectors 30a and 30b for use during disinfection. A fourth recirculation or disinfection tubing or line 52r4 extends between disinfection connectors 30c and 30d for use during disinfection.

[0064] System 10 further includes PD fluid containers or bags 38a-38c (e.g., holding the same or different formulations of PD fluid), which connect to distal ends 24d of reusable PD fluid lines 24a-24c, respectively. System 10d further includes a fourth PD fluid container or bag 38d, which connects to distal end 24d of reusable PD fluid line 24e. Fourth PD fluid container or bag 38d may hold the same or a different type of PD fluid (e.g., icodextrin) as provided in PD fluid containers or bags 38a-38c. Reusable PD fluid lines 24a-24c and 24e extend through openings (not shown), which in one embodiment are defined or provided by housing 22 of cycler 20.

[0065] System 10, in the illustrated embodiment, includes four disinfection connectors 30a-30d for connecting to distal ends 24d of reusable PD fluid lines 24a-24c and 24e, respectively, during disinfection. System 10 also provides a patient line connector 32, including an internal lumen, e.g., a U-shaped lumen, that directs fresh or used dialysis fluid from one PD fluid lumen into the other PD fluid lumen of dual lumen reusable patient line 28. Reusable supply tubing or lines 52a1-52a4 communicate with reusable supply lines 24a-24c and 24e, respectively. Reusable supply tubing or lines 52a1-52a3 interface with valves 54a-54c, respectively, to allow PD fluid from the desired PD fluid containers or bags 38a-38c to be drawn into cycler 20. Three-way valve 94a, in the illustrated example, allows control unit 100 to select between (i) 2.27% (or other) glucose dialysis fluid from container or bag 38b or 38c, and (ii) icodextrin from container or bag 38d. In the illustrated embodiment, icodextrin from container or bag 38d is connected to a normally closed port of three-way valve 94a.

[0066] 1 also illustrates that system 10 includes and uses a disposable filter set 40, which is in fluid communication with the new and used PD fluid lumens of the dual lumen reusable patient line 28. The disposable filter set 40 includes a disposable connector 42 that connects to the distal end 28d of the reusable patient line 28. The disposable filter set 40 includes a connector 48 that connects to a patient transfer set. The disposable filter set 40 further includes a sterilizing grade filter membrane 46 that further filters the new PD fluid.

[0067] System 10, in one embodiment, is constructed such that drain line 52i is fluidly connected downstream of dialysis fluid pump 70 during fill. In this manner, if drain valve 54i fails or somehow leaks during patient fill of patient P, fresh PD fluid is pushed down disposable drain line 36 instead of potentially used PD fluid being drawn into pump 70. Disposable drain line 36, in one embodiment, is removed for sanitization while drain line connector 34 is capped via cap 34c.

[0068] System 10 further includes a leak detection pan 82 located at the bottom of housing 22 of cycler 20 and a corresponding leak detection sensor 84 that outputs to control unit 100. In the illustrated embodiment, system 10 includes an additional pressure sensor 78c located upstream of dialysis fluid pump 70, which allows measurement of the pressure intake of pump 70 and helps control unit 100 to more accurately determine pump volume. The additional pressure sensor 78c, in the illustrated embodiment, is located along vent line 52e, which may be filled with air or a mixture of air and PD fluid, but which should nevertheless be at the same negative pressure as the PD fluid located in PD fluid line 52c.

[0069] System 10, in the example of FIG. 1, includes redundant pressure sensors 78b1 and 78b2, one of which is used for pump control as discussed herein while the output of the other pressure sensor is a safety or watchdog output to ensure that the control pressure sensor is reading accurately. Pressure sensors 78b1 and 78b2 are located along a line that includes third recirculation valve 54r3. In still further examples, system 10 may employ one or more intersections, marked via X in FIG. 1, which may (i) reduce the overall amount and volume of internal reusable tubing, (ii) reduce the number of valves required, and (iii) allow the portion of the fluid network shared by both new and used PD fluid to be minimized.

[0070] The system 10 further includes a source of acid, such as a citric acid container or bag 66 in the example of FIG. 1. The citric acid container or bag 66 is in selective fluid communication with the second three-way valve 94b via a citric acid valve 54m located along the citric acid line 52m. The citric acid line 52m is, in one embodiment, connected to a normally closed port of the second three-way valve 94b to provide a redundant valve between the citric acid container or bag 66 and the PD fluid circuit during treatment. The redundant valve ensures that citric (or other) acid does not reach the treatment fluid line during treatment. Citric (or other) acid is used instead during disinfection.

[0071] FIG. 1 illustrates that in an optional embodiment, the thermoelectric heater 150 is used in combination with a smaller, typically resistive in-line heater 152 (shown in phantom as optional), also under the control of the control unit 100, which mitigates the disadvantages of such an in-line heater, such as heater cost, heat generation, ventilation space, and expensive electrical components. In the illustrated embodiment, the thermoelectric heater 150 is placed upstream of the smaller resistive in-line heater 152 so that the thermoelectric heater is maximized. The smaller resistive in-line heater 152 may then be used as a backup heater, providing any heating delta only as needed so that the medical or dialysis fluid reaches the desired treatment temperature. However, it is also expressly contemplated (not shown) to reverse the order of the thermoelectric heater 150 and the smaller resistive in-line heater 152 as shown in FIG. 1, such that the resistive heater 152 is placed upstream of the thermoelectric heater 150. In a sequence not shown, where the resistive heater 152 is placed upstream of the thermoelectric heater 150, it is contemplated that the control unit 100 will reverse the polarity of the thermoelectric heater 150, if needed, to cool the overheated medical fluid exiting the resistive heater 152. In one embodiment, it is now contemplated that under normal circumstances the smaller resistive in-line heater 152 will run at a lower duty cycle to pre-warm the medical fluid, which reduces the burden on the downstream thermoelectric heater 150 in heating the medical fluid to the desired therapeutic temperature.

[0072] Although not shown, it is contemplated that a temperature sensor, outputting to the control unit 100, may be placed between the thermoelectric heater 150 and the in-line heater 152 (either in the order of thermoelectric heater 150 first or in-line heater 152 first). The additional temperature sensor senses the amount of heat delivered by the thermoelectric heater 150. The control unit 100 may then use the output from the additional temperature sensor to determine when and how much (e.g., duty cycle) to power the in-line heater 152. In alternative situations in which the in-line heater 152 is used continuously or nearly continuously in combination with the continuous use of the thermoelectric heater 150, the additional temperature sensor may not be required and the output from the temperature sensor 58a may be used as feedback, for example, in a proportional, integral, derivative ("PID") routine to control both the thermoelectric heater 150 and the in-line heater 152.

[0073] It should be understood that system 10 is not required to (i) be a dialysis system or (ii) use redundant or durable components that are sanitized between uses in order to employ the sensor thermoelectric heating of the present disclosure. System 10 may instead be any type of medical fluid system and may employ a disposable set having a disposable pumping portion that contacts the corresponding medical fluid. In the primary embodiment described herein, thermoelectric heater 150 is described to operate in conjunction with a PD machine or cycler 20 for which the PD fluid heat exchanger is a reusable or durable component that is sanitized between treatments.

[0074] 2, an embodiment for providing a thermoelectric heater 150 in the PD machine or cycler 20 of the system 10 is illustrated. The thermoelectric heater 150, in one embodiment, operates according to the Peltier effect and therefore may be referred to herein as a Peltier module 150. The thermoelectric heater 150 includes two sides or plates 154 and 156, in FIG. 2, which, in one embodiment, are separated by an n-type semiconductor 158n and a p-type semiconductor 158p. When a direct current ("DC") voltage, such as 5VDC, 12VDC, or 24VDC, supplied by a power supply 110, depending on the type of thermoelectric heater 150, is applied to and flows through the sides 154, 156 and the semiconductors 158n, 158p, heat is conducted from the cooled side or plate 156 to the heated side or plate 154. The power supply 110, in one embodiment, is under the control of the control unit 100. The polarity of the DC voltages applied to sides 154, 156 and semiconductors 158n, 158p may be reversed by the control unit 100 so that heat is instead conducted from side or plate 154 to side or plate 156.

[0075] The input voltage level for the thermoelectric heater 150 (e.g., 5VDC, 12VDC, or 24VDC) may be based on its maximum current rating and should not exceed it. Because the resistive thermoelectric heater 150 is relatively fixed (with some variation with temperature), the applied voltage is adjusted to provide a current that, in one embodiment, is less than the maximum current rating. The adjustment of the voltage is performed, in one embodiment, by the control unit 100 via feedback control using the output from the temperature sensor 58a, which sets the input voltage to a level that keeps the resulting current below a maximum threshold.

[0076] The heated side or plate 154 and the cooled side or plate 156 are ceramic in one embodiment, but may be made of other conductive materials and combinations thereof. A unique n-type and one p-type semiconductor 158n, 158p may be used because they provide different electron densities. Alternating n-type and p-type pillars of semiconductors 158n, 158p are placed in thermal parallel to one another and in electrical series to one another in one embodiment. The n-type and p-type semiconductors 158n, 158p may be electrically connected in series with the heated side 154 and the cooled side 156 via conductive leads 162, e.g., aluminum or copper leads, located between the ends of the semiconductor pillars and the inside of the heated side 154 and the cooled side 156.

[0077] When the power supply 110 of the machine 20 applies a DC voltage to the free ends of the n-type and p-type semiconductors 158n, 158p, DC current flows across the semiconductors and the conductive leads 162 that connect them in series, causing a temperature difference between the heated side 154 and the cooled side 156. The cooled side 156 absorbs heat, which is then transported by the semiconductors 158n, 158p to the heated side 154. The heating capacity of the thermoelectric heater 150, in one embodiment, is proportional to the combined total cross-sectional area of ​​the pillars of each semiconductor 158n, 158p (e.g., electrically connected in series, reducing the supply current). The length of the pillar semiconductors 158n, 158p is selected in one embodiment based on a balance between (i) a longer pillar having a greater thermal resistance between the sides 154, 156 but producing more resistive heating, and (ii) a shorter pillar having greater electrical efficiency but causing more heat leakage from the hot side to the cold side by thermal conduction. Although the system 10 illustrates a single thermoelectric heater 150, multiple thermoelectric heaters or Peltier modules 150, each in communication with a medical fluid heat exchanger 170, may alternatively be provided. Here, the power supply 110 powers each thermoelectric heater or Peltier module 150 separately.

[0078] The thermoelectric heater 150 may be considered a Class II device, with the Peltier module being electrically insulated, for example, via the ceramic sides or plates 154, 156, to limit electrical creepage. The thermoelectric heater 150 forms a solid-state active heat pump that transfers heat from the cooled side 156 to the heated side 154. It should be appreciated that the control unit 100 and power supply 110 are configured, in one embodiment, to be capable of reversing the polarity of the applied DC power to switch the thermal polarity, such that side 154 becomes the cooled side and side 156 becomes the heated side. The heated and cooled sides are thus determined by the direction of the electrical current flowing through the thermoelectric heater 150.

[0079] The system 10 illustrates in FIG. 2 that the heated side 154 of the thermoelectric heater 150 is used to heat a medical fluid, such as a dialysis fluid, prior to use for treatment, while the cooled side 156 is placed in proximity to electronic components of the medical fluid machine 20 to help keep those components cooled. As illustrated in FIG. 2, the heated side 154, in one embodiment, is placed in direct thermal contact with a heat exchanger 170, which carries the medical fluid to be heated, e.g., a PD fluid. Heat is exchanged from the heated side 154 of the thermoelectric heater 150 to the PD fluid flowing through the heat exchanger 170. FIG. 2 illustrates the heat exchanger 170 diagrammatically, while FIG. 3 illustrates one implementation for the heat exchanger 170. FIGS. 2 and 3 illustrate that the heat exchanger 170, in one embodiment, includes a heat exchange block 172, which may be a conductive metal block, such as aluminum, copper, or stainless steel. The heat exchange block 172 does not contact the medical fluid, therefore, its material may be optimized for thermal conductivity.

[0080] 3 illustrates that the heat exchanger 170 includes a conductive serpentine path 174 that carries a medical fluid, such as a dialysis fluid. The conductive serpentine path 174 is therefore made from medical fluid safe stainless steel in one embodiment. The serpentine path 174 allows the medical fluid to travel back and forth multiple times along the heated side 154 and the heat exchange block 172. In the system 10 of FIG. 2, heat is thus conducted from the heated side 154 to the heat exchange block 172, from the heat exchange block 172 to the serpentine path 174, and from the serpentine path 174 to the medical fluid. The serpentine path 174 includes a medical fluid inlet 176 and a medical fluid outlet 178, which extends to other fluid components as illustrated in FIG. 1. In an alternative embodiment, the serpentine path is formed directly into the heat exchange block 172, which may include two seals and machined stainless steel halves that form the serpentine path, or may be formed via an additive process to have a serpentine path. In a further alternative embodiment, the heat exchange block 172 is not provided and the conductive serpentine path 174 is instead abutted directly against the heated side 154 of the thermoelectric heater 150.

[0081] It is contemplated to mount temperature sensor 58a (FIG. 1) or additional temperature sensors on or within block 172, the output of which may be used for temperature control of the medical fluid, e.g., PD fluid, and to allow block 172 to be preheated to a desired temperature prior to treatment. Such preheating reduces start-up time and minimizes the chance of having cold fluid initially. The output of temperature sensor 58a (FIG. 1) or additional temperature sensors located on or within block 172 (FIG. 3) may additionally be used to allow block 172 to be cooled to a desired temperature. Being able to cool block 172, and thus the overheated medical fluid, allows the overheated medical fluid to be cooled and then delivered for treatment, whereas in many resistive in-line heater applications the overheated medical fluid is instead delivered to a drain, wasting such fluid.

[0082] In the illustrated embodiment of Fig. 2, the cooled side 156 of the thermoelectric heater 150 is mounted or otherwise abutted against one or more mounting plates 160 for mounting to electrical components 164a, which may be any of the components illustrated in Fig. 1. The material of the one or more mounting plates 160 may be selected for its ability to conduct thermal energy well, such as aluminum, since it does not contact the medical fluid. Any electrical components 164a that benefit from the cooling of the thermoelectric heater 150, such as the medical or dialysis fluid pump 70, medical fluid valves 54a-54g, 54i, 54m, 54r1-54r3, 94a, 94b, flow sensor or flow switch 26, temperature sensors 58a, 58b, pressure sensors 78a, 78b1, 78b2, 78c, any associated electronics, and any other electronics of the medical fluid machine 20, may be mounted to the one or more mounting plates 160. Any electrical component 164a whose mounting surface is not thermally conductive may be thermally assisted, for example, if insulation is provided, via one or more heat pipes 164p extending from a conductive portion of the component 164a to one or more mounting plates 160. The heat pipes 164p may be made of any thermally conductive material, such as aluminum or copper.

[0083] FIG. 2 further illustrates that one or more heat fins 166 may be attached to or formed with one or more mounting plates 160 to convectively cool electrical components 164b (e.g., any of the components listed above, associated electronics, or other electronics) that cannot be mounted to one or more mounting plates for any reason. The one or more cooled heat fins 166 receive heat from adjacent electrical components 164b via air circulation therebetween. If desired, a fan 168 may be provided under the control of the control unit 100 to help convect heat from the electrical components 164b to the one or more heat fins 166. The fan 168 or a different fan may also be oriented and run at a low speed under the control of the control unit 100 to cool the environment on the dry side of the medical fluid machine 20, e.g., to the right of the mounting plate 160 in FIG. 2. Fan 168 or a different fan may also be directed to cool a desired surface of medical fluid machine 20 under the control of control unit 100. Additionally, any fan, such as fan 168, may be mounted in an opening provided in a surface of medical fluid machine 20 to draw in ambient air. Additionally, any fan, such as fan 168, may be mounted on an exterior surface of medical fluid machine 20, assuming Class II certification of medical fluid machine 20 can be met, which may be accomplished by electrically isolating the surface of medical fluid machine 20 used for mounting from all medical fluid flow paths and electronics of medical fluid machine 20 (examples enumerated herein).

[0084] The energy flow (Qh) associated with the heated side 154 of the thermoelectric heater 150 may be modeled as the energy flow (Qc) on the cooled side 156 plus the power added to the module 150, i.e., the voltage supplied times the current supplied (V×I). The energy flow (Qh) on the heated side 154 used to heat the medical or PD fluid therefore exceeds the power added to the module (V×I) by the amount of the energy flow (Qc) on the cooled side 156, which is relatively large at the beginning of a medical fluid heating session, which gradually drops until the temperature difference between the heated side 154 and cooled side 156 becomes too large and Qc drops to zero.

[0085] One exemplary Peltier module that can be used with the thermoelectric heater 150 of the present disclosure is capable of handling a heated side 154 to cooled side 156 temperature difference of 75° C. For a PD fluid treatment in which the PD fluid exits the heat exchanger at, for example, 37° C., Qc will contribute energy from the cold side 156 as long as the cold side remains warmer than −38° C. (as long as the temperature difference between the heated side 154 and cooled side 156 is not too large). This is highly likely, especially considering that the cold side 156 exchanges heat with the surrounding electrical components 164a, 164b, cooling such components.

[0086] A sample calculation of energy removed from the surrounding environment, including electrical components 164a, 164b, operating under standard conditions may be as follows, with the following assumptions made regarding mass and specific heat for certain components: Mounting plate 160, aluminum, 0.5kg, 900J / (kg×℃) Printed circuit board (“PCB”), 0.5kg, 390J / (kg×℃) Valve, each 0.25kg, 400J / (kg×℃) Water, 2 kg, 4,180 J / (kg x ℃) (approximate to medical fluids) If it is assumed that 2 kg of water (medical fluid) is heated from 15° C. to 37° C. during patient fill, then 4,180 J / (kg×° C.)×2 kg×(37-15° C.)=183,920 J of energy is required. If it is assumed that the medical fluid machine 20 keeps the medical fluid at 23° C. at the start of the patient fill (the fluid is now at room temperature) and energy from the mounting plate 160 and components 164a, 164b is allowed to be used down to 8° C., then the following amount of energy is provided: (900 J / (kg×° C.)×0.5 kg+390 J / (kg×° C.)×0.5 kg+400 J / (kg×° C.)×0.25 kg×10 valves (for example))×15° C.=24,675 J. 24,675 J is the energy removed from the PD machine or cycler 20 and provided to the thermoelectric heater 150 during patient fill, in one embodiment. A fully loaded medical fluid machine 20 will have more mass than the small amounts listed above (e.g., about 10 kg) so that the amount of actual energy that can be borrowed from the medical fluid machine 20 will be higher. The pure thermal mass of the machine 20 should provide at least 24,675 / 183,920 or 13% of the energy required. The active components 164a, 164b (valves and dialysis fluid pump 70) also generate heat while operating, thus increasing the available energy.

[0087] The solid-state nature of the thermoelectric heater 150 of the present disclosure provides a quiet solution since there is no internal switching. Powering the thermoelectric heater 150 is also advantageous since the heater uses DC power, which may be supplied by a backup battery 112 (FIG. 2) instead of or in addition to DC power from the primary power supply 110. Power from the backup battery 112 may be provided in addition to and intermittently, for example, during maximum power consumption and high heating power modes, so as not to overload the primary power supply 110. Also, the polarity of the power delivered to the thermoelectric heater 150 may be reversed, so that the control unit 100 is contemplated to reverse the polarity of the power from the supply 110 when the temperature of the cooled side 156 approaches the dew point temperature, the goal here being to prevent condensation from forming on the cold side of the module 150. To this end, a low cost humidity / temperature sensor integrated circuit (not shown) may be provided on the printed circuit board of the control unit 100, the sensor and integrated circuit being configured to calculate the dew point temperature.

[0088] It is contemplated to use a pulse width modulated ("PWM") driver to control the input power to the thermoelectric heater 150. Still, electromagnetic interference ("EMI") and radio frequency ("RF") noise is lower than with resistive heaters running at 115 / 230VAC due to switching at a significantly lower DC voltage. The use of DC power also reduces leakage currents and flicker because the power is gradually controlled and a large resistive load is not switched on and off, as is the case with many resistive in-line heaters.

[0089] It should be understood that various changes and modifications to the presently preferred embodiment described herein will be apparent to those skilled in the art. Accordingly, such changes and modifications are intended to be covered by the appended claims. For example, as noted above, the system 10 need not use redundant or durable components, but may instead employ a disposable set having a disposable pumping portion that contacts the corresponding medical fluid. Here, the serpentine path 174 may be a disposable path formed as part of the disposable set, which is removably retained by the heat exchange block 172 during treatment, and removed from the heat exchange block 172 after treatment. Here, the heat exchange block 172 may be provided as part of the front (or top) working surface of the medical fluid machine 20, and the disposable serpentine path 174 may be retained in place within the heat exchange block 172 via a hinged door of the medical fluid machine 20. In an alternative disposable embodiment, the heat exchange block 172 and the serpentine path 174 are both formed as part of the disposable set. Here, the heated side 154 of the thermoelectric heater 150 may be provided as part of the front (or top) working surface of the medical fluid machine 20, and the disposable heat exchange block 172 and serpentine path 174 may be held in a fixed position relative to the heated side 154 via a hinged door of the medical fluid machine 20.

Claims

1. 1. A medical fluid system comprising: a medical fluid pump configured to pump a medical fluid; a thermoelectric heater positioned and arranged to heat medical fluid pumped by the medical fluid pump, the thermoelectric heater including a heated side and a cooled side; a heat exchanger through which medical fluid pumped by the medical fluid pump is heated, the heat exchanger being positioned and arranged in thermal communication with a heated side of the thermoelectric heater; a mounting plate, the medical fluid pump or other component of the medical fluid system being supported by the mounting plate, the mounting plate being positioned and arranged to be in thermal communication with the cooled side of the thermoelectric heater; A medical fluid system comprising:

2. 10. The medical fluid system of claim 1, wherein the heat exchanger in thermal communication with the heated side of the thermoelectric heater comprises directly contacting the heated side.

3. The medical fluid system of claim 1 , wherein the heat exchanger includes a conductive heat exchanger block and a conductive serpentine path supported by the conductive heat exchanger block.

4. The medical fluid system of claim 3 , wherein the conductive heat exchanger block is made from aluminum or copper and the conductive serpentine path is made from stainless steel.

5. The medical fluid system of claim 3 including a temperature sensor located on or within the conductive heat exchanger block.

6. 10. The medical fluid system of claim 1, wherein the mounting plate in thermal communication with the cooled side of the thermoelectric heater comprises directly contacting the cooled side.

7. 2. The medical fluid system of claim 1, wherein the medical fluid pump or other component of the medical fluid system is supported by the mounting plate includes the medical fluid pump or other component of the medical fluid system being mounted to the mounting plate.

8. 10. The medical fluid system of claim 1, wherein the other components include at least one of: (i) at least one valve; (ii) at least one temperature sensor; (iii) at least one pressure sensor; or (iv) a flow sensor or flow switch, and electronics associated with the other components.

9. 10. The medical fluid system of claim 1 including at least one heat pipe extending from at least one of the medical fluid pump or other components of the medical fluid system to the mounting plate for conducting heat to the mounting plate.

10. 10. The medical fluid system of claim 1, wherein the mounting plate is attached or formed with at least one thermal fin for convectively transferring heat from at least one component of the medical fluid system to the mounting plate, the at least one component being located adjacent to the at least one thermal fin.

11. 11. The medical fluid system of claim 10, including at least one fan positioned and arranged to blow air between the at least one heat fin and at least one convection-cooled component of the medical fluid system.

12. The medical fluid system of claim 1 , wherein the thermoelectric heater includes a plurality of semiconductors extending between the heated side and the cooled side.

13. The medical fluid system of claim 12 including a plurality of conductive leads located between the plurality of semiconductors and the heated and cooled sides.

14. 14. The medical fluid system of claim 13, wherein the plurality of conductive leads are positioned and arranged such that the plurality of semiconductors operate electrically in series.

15. The medical fluid system of claim 12 , wherein the semiconductors operate in thermal parallel.

16. The medical fluid system of claim 1 , further comprising a resistive in-line heater positioned in fluid series with the thermoelectric heater.

17. 17. The medical fluid system of claim 16, including a control unit, wherein the thermoelectric heater and the resistive in-line heater are under the control of the control unit, the control unit configured to power the resistive in-line heater as needed to assist the thermoelectric heater in heating the medical fluid to a desired temperature.

18. 10. The medical fluid system of claim 1, including a control unit configured to reverse a polarity of power to the thermoelectric heater so that the heated side becomes the cooled side of the thermoelectric heater, the heat exchanger then being positioned and arranged to be in thermal communication with the cooled side.

19. 20. The medical fluid system of claim 18, including a humidity sensor positioned and arranged to measure humidity adjacent the mounting plate, the control unit further configured to use an output from the humidity sensor to determine when to reverse polarity of power to the thermoelectric heater to prevent the mounting plate from reaching a dew point temperature.

20. 1. A method for heating a medical fluid, comprising: providing electrical energy to a thermoelectric heater to create a heated side and a cooled side of the thermoelectric heater, the thermoelectric heater being provided as part of a medical fluid machine; positioning the heat exchanger such that medical fluid flowing through the heat exchanger receives heat from a heated side of the thermoelectric heater; Positioning at least one component of the medical fluid machine such that heat generated by the at least one component is received by a cooled side of the thermoelectric heater, the heat received by the cooled side of the thermoelectric heater being added to the heat available at the heated side of the thermoelectric heater generated via the supply of electrical energy; A method comprising:

21. 21. The method of claim 20, wherein the medical fluid transfer heat exchanger is reusable or is provided as part of a disposable medical fluid transfer set.

22. 21. The method of claim 20, wherein positioning the heat exchanger includes positioning the heat exchanger within the medical fluid machine or as part of a working surface of the medical fluid machine.

23. reversing the polarity of electrical energy to the thermoelectric heater; reversing the heated and cooled sides of the thermoelectric heater, where the medical fluid flowing within the heat exchanger delivers heat to the cooled side of the thermoelectric heater; 21. The method of claim 20, further comprising:

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