Patent Publication Number: US-2021170088-A1

Title: Renal failure therapy system and method for electrically safe treatment

Description:
PRIORITY CLAIM 
     The present application is a continuation of U.S. application Ser. No. 15/766,185, filed Apr. 5, 2018, which is a National Phase of International Application No. PCT/EP2016/074710, filed Oct. 14, 2016, which claims priority to Swedish Application No. 1551325-2, filed Oct. 14, 2015. The entire contents of each are incorporated herein by reference and relied upon. 
    
    
     BACKGROUND 
     The present disclosure relates generally to medical systems. More specifically, the present disclosure relates to medical systems that allow a patient to safely power an external electronic device during treatment. 
     Hemodialysis (“HD”) in general uses diffusion to remove waste products from a patient&#39;s blood. A diffusive gradient that occurs across the semi-permeable dialyzer between the blood and an electrolyte solution called dialysis fluid causes diffusion. Hemofiltration (“HF”) is an alternative renal replacement therapy that relies on a convective transport of toxins from the patient&#39;s blood. This therapy is accomplished by adding substitution or replacement fluid to the extracorporeal circuit during treatment (typically ten to ninety liters of such fluid). The substitution fluid and the fluid accumulated by the patient in between treatments is ultrafiltered over the course of the HF treatment, providing a convective transport mechanism, which is particularly beneficial in removing middle and large molecules (in hemodialysis there is a small amount of waste removed along with the fluid gained between dialysis sessions, however, the solute drag from the removal of that ultrafiltrate is typically not enough to provide convective clearance). 
     Hemodiafiltration (“HDF”) is a treatment modality that combines convective and diffusive clearances. HDF flows dialysis fluid through a dialyzer, similar to standard hemodialysis, providing diffusive clearance. In addition, substitution solution is provided directly to the extracorporeal circuit, providing convective clearance. These modalities are administered by a dialysis machine. The machines may be provided in a center or in a patient&#39;s home. Dialysis machines provided in a center are used multiple times a day for multiple patients and therefore must be cleaned between treatments. Dialysis machines use multiple components, including electrical components. 
     Outside electrical devices have the potential to expose people to the risk of spurious electric currents. In the case of medical electrical equipment (and dialysis machines in particular), the risk is potentially greater how depending upon the equipment is connected to the patient. Patients connected to present dialysis machines may be poorly safeguarded against leakage current due to contact with external electrical equipment, such as bed lamps, electrically adjustable beds or treatment chairs, lap tops, phones connected to chargers, and other electrical equipment that is in turn connected to a mains electrical power source. Poor quality chargers are especially dangerous as their electrical insulation may break down, leading to fault currents that may run to the patient. It is accordingly advisable for dialysis clinics to ask that patients during treatment not plug their electronic devices into an external power source, which may be inconvenient for patients undergoing a treatment that may last for hours. 
     It is accordingly desirable to provide a system that allows a patient to use and power an external electronic device during treatment safely. 
     SUMMARY 
     The present disclosure provides a renal failure therapy system and method that performs hemodialysis (“HD”), hemofiltration (“HF”) and hemodiafiltration (“HDF”). Accordingly, “renal failure therapy” as used herein is meant to include any one, or more, or all of HD, HF and/or HDF. 
     The renal failure therapy system and method of the present disclosure includes a machine providing at least one electrically insulated electrical socket, which enables a patient undergoing treatment to power an external device, such as a smartphone, personal computer, reading lamp and the like. The goal of the electrical insulation is to provide an extra galvanic separation between the patient and the machine to minimize leakage or fault currents. For AC current sockets, the electrical insulation may include a transformer that provides galvanic isolation forming an open circuit, which prevents propagation of fault currents. The transformer has an input coil separated physically from an output coil. The input coil magnetically induces a desired AC voltage in the output coil. The desired AC output voltage charges or powers the user&#39;s electrical device, such as a computer. 
     For DC sockets, the electrical insulation may take multiple forms. One form of DC insulation uses DC to AC conversion. The DC input voltage is converted to an AC input voltage, which then powers an input coil. The AC input coil magnetically induces an AC output voltage in an output coil as described above. Here, however, the AC output voltage is converted into a desired DC voltage, typically 5 VDC, 12 VDC or 24 VDC, for powering and/or charging the user&#39;s electrical device. Other DC insulation providing galvanic protection for low voltages may include optical means. 
     The machine may have multiple electrically insulated sockets, for example, providing an array of desirable output voltages of 5 VDC, 12 VDC, 24 VDC, 120 VAC, and/or 220 VAC. It is contemplated to provide banks of electrically insulated sockets of the same output voltage, for example, a bank of sockets providing output voltages of 5 VDC. Where coiled transformers are used, the banks may have a single primary coil for multiple secondary coils, or a single primary coil for each secondary coil. 
     The electrically insulated electrical sockets may be located on the front of the renal failure therapy machine, or at another location on the machine that is readily accessible to the patient and/or nurse. It is ensured that the electrically insulated electrical sockets are well made, so that they provide robust electrical insulation. Indeed, the sockets may provide two layers of electrical insulation (or double insulation). In this manner, it is assured that the patient may safely plug his or her electrical device into the renal failure therapy machine during treatment for operation and/or charging. 
     As discussed, the electrically insulated sockets allow the user to safely power their external electrical devices during treatment. To make treatment even safer, it is contemplated to combine the electrically insulated sockets with other electrical insulation, which protects the patient electrically towards a fluid path in the renal failure therapy machine. That is, one may think of the patient as being placed electrically between the external electrical device connected to the clinic&#39;s mains power system and electrical earth via a path that runs through the blood lines, the patient, the conductive dialysis fluid lines in the machine, and outside the machine through an external used dialysate drain line. The electrically insulated sockets place a layer (or double layer) of electrical protection between the patient and the clinic&#39;s mains power system. It is also contemplated to place a layer of electrical protection between the patient and electrical earth via the conductive fluidic pathway through the renal failure therapy machine. 
     In one embodiment, the layer of electrical protection between the patient and electrical earth includes an electrically floating fluid pathway. Generally, an electrically floating fluid pathway is one that is not connected to electrical earth. As used herein, electrically floating fluid pathway in one embodiment means instead that there is no pathway to electrical earth within the blood lines, dialysis fluid lines either inside the machine or outside the machine towards the dialyzer, concentrate lines, or even the water lines (e.g., if the water is non-deionized). That is, electrically floating fluid pathway may mean a fluid pathway which, when carrying an electrically conductive fluid therein, would itself render the conductive fluid electrically floating relative to an electrical potential, such as electrical earth, provided to the dialysis machine through the mains and/or through earthed parts connected to the dialysis machine (e.g. drain and external water lines). The electrically floating fluid pathway may include the entire or one or several portion(s) of the blood lines, (fresh and/or used) dialysis fluid lines, concentrate lines, and/or water lines as well as components, such as sensors and pumps, connected to the above mention fluid lines. The only pathway to electrical earth is via the used dialysis fluid traveling outside the machine through an external drain line to electrical earth, for example, at the clinic&#39;s house drain. Making any fault voltages generated at the patient travel all the way to electrical earth at the house drain increases the naturally occurring impedances within the fluid lines that the fault voltage sees, thereby minimizing the current generated by the fault voltage. 
     There are a number of structural modifications made to allow the machine to operate with an electrically floating fluid pathway. First, dialysis machines typically intentionally connect various flow components to protective earth. For example, sensing equipment is typically connected to a signal ground to divert fault currents away from the sensing equipment to prevent false readings. The signal ground may be connected to protected earth in the dialysis machine directly or indirectly via the dialysis fluid. The electrically floating pathway of the present disclosure cannot exist with such connections to protective earth. Instead, the sensitive equipment is here provided with electrical bypassing, which bypasses fault currents around the equipment, through the electrically floating fluid pathway and through an external used dialysate drain line, to electrical earth at the house drain. 
     Second, certain flow components, such as the sensing equipment, have probes or other conductive structures that contact the medical fluid, such as dialysis fluid. Any such component becomes a potential pathway to electrical earth due to its wiring. In the present disclosure, the wiring of any such component is electrically isolated with a single or double layer of electrical insulation in the same manner as the electrically insulated electrical sockets discussed herein. 
     The above-described combination of electrical insulation prevents or reduces fault voltages generated due to the powering of a patient&#39;s external personal electrical equipment (a notoriously large source of fault voltages) from occurring. The combination also forces any fault voltages that don&#39;t occur at the patient or somewhere within the machine to dissipate along a relatively high impedance fluid path, through the electrically floating fluid pathway and through an external used dialysate drain line, to the electrical earth at the house drain. 
     In light of the technical features set forth herein, and without limitation, in a first aspect, a renal failure therapy system includes: a dialyzer; a blood circuit in fluid communication with the dialyzer; a dialysis fluid circuit in fluid communication with the dialyzer; a housing supporting the dialyzer, the blood circuit and the dialysis fluid circuit; and at least one electrical socket held by the housing, the electrical socket providing a voltage output dedicated to a particular voltage type of external electrical device for powering or charging the external electrical device, the at least one electrical socket including electrical insulation for protecting a patient while powering the external electrical device. 
     In a second aspect, which may be used in combination with any other aspect described herein unless specified otherwise, the voltage output dedicated to a particular voltage type of external electrical device is a USB voltage output. 
     In a third aspect, which may be used in combination with any other aspect described herein unless specified otherwise, the voltage output dedicated to a particular voltage type of personal external device is a 5, 10 or 24 VDC output. 
     In a fourth aspect, which may be used in combination with any other aspect described herein unless specified otherwise, the voltage output dedicated to a particular voltage type of personal external device is a 120 or 240 VAC output. 
     In a fifth aspect, which may be used in combination with any other aspect described herein unless specified otherwise, the electrical insulation of the at least one electrical socket includes a transformer. 
     In a sixth aspect, which may be used in combination with any other aspect described herein unless specified otherwise, the electrical insulation of the at least one electrically insulated electrical socket includes a DC to DC converter. 
     In a seventh aspect, which may be used with the sixth aspect in combination with any other aspect described herein unless specified otherwise, the DC to DC converter includes an input conductively insulated from an output. 
     In an eighth aspect, which may be used in combination with any other aspect described herein unless specified otherwise, the electrical insulation of the at least one electrical socket includes a transformer in combination with (i) an AC to DC converter or (ii) a DC to AC converter and an AC to DC converter. 
     In a ninth aspect, which may be used in combination with any other aspect described herein unless specified otherwise, the renal failure therapy system includes a bank of electrical sockets providing a first voltage output dedicated to a same particular voltage type of the external electrical device. 
     In a tenth aspect, which may be used with the ninth aspect in combination with any other aspect described herein unless specified otherwise, the bank is a first bank, and which includes a second bank of electrical sockets providing a second voltage output dedicated to a same particular voltage type of second external electrical device, the second voltage different from the first voltage. 
     In an eleventh ninth aspect, which may be used in combination with any other aspect described herein unless specified otherwise, the renal failure therapy system includes an electrically floating fluid pathway provided in at least a portion of the blood circuit and at least a portion of the dialysis fluid circuit, wherein the only electrical path to ground is via used dialysis fluid traveling through the machine to electrical earth. 
     In a twelfth aspect, which may be used with the eleventh aspect in combination with any other aspect described herein unless specified otherwise, at least one electrically sensitive component in the at least portion of the dialysis fluid circuit of the electrically floating fluid pathway is electrically bypassed. 
     In a thirteenth aspect, which may be used with the twelfth in combination with any other aspect described herein unless specified otherwise, the at least one electrically sensitive component is electrically insulated from its power and signal input wires. 
     In a fourteenth aspect, which may be used with the eleventh aspect in combination with any other aspect described herein unless specified otherwise, the renal failure therapy system includes an external drain line and a drain having an electrical earth, and wherein the electrically floating fluid pathway leads to the external drain line, which leads to the drain. 
     In a fifteenth aspect, which may be used in combination with any other aspect described herein unless specified otherwise, a renal failure therapy machine for providing treatment to a patient using an external electrical device includes: a dialyzer; a blood circuit in fluid communication with the dialyzer; a dialysis fluid circuit in fluid communication with the dialyzer; a housing supporting the dialyzer, the blood circuit and the dialysis fluid circuit; and an electrical socket held by the housing, the electrical socket providing a voltage output dedicated to a voltage of the external electrical device for powering or charging the external electrical device, the electrical socket including electrical insulation for protecting a patient while powering the external electrical device. 
     In a sixteenth aspect, which may be used with the fifteenth aspect in combination with any other aspect described herein unless specified otherwise, there is no protective earth connection within or on the housing to any fluid flowing within the dialysis fluid circuit. 
     In a seventeenth aspect, which may be used with the fifteenth aspect in combination with any other aspect described herein unless specified otherwise, there is no protective earth connection within or on the housing to any fluid flowing within the blood circuit or dialyzer. 
     In an eighteenth aspect, which may be used with the fifteenth aspect in combination with any other aspect described herein unless specified otherwise, the electrical socket is a first socket and the voltage output is a first voltage output, and wherein the housing supports a second electrical socket providing a second voltage output different than the first voltage output. 
     In a nineteenth aspect, which may be used with any other aspect described herein unless specified otherwise, the electrical insulation is or includes double electrical insulation. 
     In a twentieth aspect, any of the features, functionality and alternatives described in connection with any one or more of  FIGS. 1 to 7  may be combined with any of the features, functionality and alternatives described in connection with any of the other one or more of  FIGS. 1 to 7 . 
     It is therefore an advantage of the present disclosure to provide a hemodialysis, hemofiltration or hemodiafiltration system and method having electrically insulated electrical sockets. 
     It is another advantage of the present disclosure to provide a hemodialysis, hemofiltration or hemodiafiltration system and method having electrically insulated electrical sockets in combination with electrically insulated input lines to the socket to provide double insulated electrical sockets. 
     It is another advantage of the present disclosure to provide a hemodialysis, hemofiltration or hemodiafiltration system and method having electrical sockets that enable a patient to safely power and/or charge an external electrical device during treatment. 
     It is a further advantage of the present disclosure to provide a hemodialysis, hemofiltration or hemodiafiltration system and method having electrically insulated electrical sockets provided in combination with fluid lines that are additionally electrically insulated. 
     It is yet another advantage of the present disclosure to provide a hemodialysis, hemofiltration or hemodiafiltration system and method having electrically insulated electrical sockets provided in combination with fluid lines that are electrically floating within the blood tubing and the renal failure treatment machine. 
     It is yet a further advantage of the present disclosure to provide a hemodialysis, hemofiltration or hemodiafiltration system and method having electrical sockets that enable a patient to safely power and/or charge an external electrical device during treatment in combination with electrical insulation that mitigates the effects of fault voltages that may still be generated at the patient, in the blood lines, or in the dialysis fluid lines. 
     The advantages discussed herein may be found in one, or some, and perhaps not all of the embodiments disclosed herein. Additional features and advantages of the present invention are described in, and will be apparent from, the following Detailed Description of the Invention and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  illustrates one example of a potential electrical insulation problem with existing renal failure therapy machines. 
         FIG. 2  is a side elevation view of one embodiment of an electrically insulated renal failure therapy machine of the present disclosure. 
         FIGS. 3A and 3B  are exploded side and front elevation views, respectively, illustrating one example of the insulated electrical sockets of the present disclosure. 
         FIG. 4  is a side exploded view illustrating another example of the insulated electrical sockets of the present disclosure. 
         FIG. 5  is a schematic view illustrating various types of electrical conversion and isolation suitable for use with the insulated electrical sockets of the present disclosure. 
         FIG. 6  illustrates one embodiment of a dialysis fluid circuit forming part of an electrically floating fluid pathway, which may be used with the insulated electrical sockets of the present disclosure. 
         FIG. 7  illustrates one embodiment of a blood fluid circuit forming part of an electrically floating fluid pathway, which may be used with the insulated electrical sockets of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings and in particular to  FIG. 1 , a known dialysis machine  8  connected to a patient  116  illustrates a potential electrical insulation problem. Known machine  8  is connected within its housing to machine protective earth  27  in multiple places to protect various components, such as conductivity sensors, which may read improperly when subjected to currents due to fault voltages. The system&#39;s protective earth connections take the fault currents instead to protective earth  27 , protecting the sensing equipment. Machine  8  is also connected outside its housing to electrical earth  28 . 
     Protective earth  27  for known machine  8  is also intended to ensure that the patient is safe from an internal electrical failure occurring within machine  8 . However, an electrical risk to patient  116  is created because the patient is electrically connected via conductive dialysis fluid to protective earth  27 . If patient  116  touches a faulty piece of electrical equipment having an electrical potential relative to protective earth, a potentially dangerous current may flow from the faulty equipment through patient  116 , to protective earth  27 . 
     Patient  116  in the illustrated embodiment is handling an external electrical device  200 , which may be any type of electrical device, such as a reading lamp, heating pad, etc. In many cases, external electrical device  200  will be a personal communication/computing device (“PCD”), such as a smart phone, tablet, or personal computer. In any case, the external electrical device  200  is connected to mains power in  FIG. 1 . 
     Many PCD&#39;s are provided with cheaply made chargers, which are prone to failure. When the chargers fail, a very real potential for a fault voltage is created. When a fault voltage is created, if there is a path to electrical earth  28 , a fault current will be generated. The system&#39;s connections to protective earth  27  within known machine  8 , which provide low impedance paths to protect the sensing equipment, also provide a low impedance path for the fault current. 
     In many instances, needle access to patient  116  is into a vein in one of the patient&#39;s arms.  FIG. 1  illustrates an alternative needle access established in which a central venous catheter (“CVC”) is inserted into vein very close to the patient&#39;s heart. In this scenario, fault voltages, such as those just described, present a heightened risk due to the proximity to the patient&#39;s heart. 
     It is advisable for dialysis clinics to prevent the patient from powering an external electrical device  200  using the clinic&#39;s mains pour during treatment. It is difficult to ensure however that every clinic will follow this procedure for every treatment. Certain patients, perhaps not understanding the risk, may disobey the rules and plug their device  200  into the mains power system when left unattended. Moreover, chronic kidney failure treatments may last hours, leading to an ever-increasing desire for the patients to want to power their PCD&#39;s  200 . 
     Referring now to  FIG. 2 , system  10  having renal failure therapy machine  12  provides a solution to the above described problem. Machine  12  provides a renal failure therapy to patient  116 . The components of machine  12  are discussed in detail below. For now, it is enough to know that machine  12  may include internal components that prepare a dialysis fluid, and pump such dialysis fluid along a fresh dialysis fluid line  76  to a dialyzer  102 . The internal components of machine  12  also pump used dialysis fluid from dialyzer  102  along a used dialysis fluid line  56  to an external drain line  57  and to drain  60 . 
     Machine  12  also includes a blood pump that pumps blood from patient  116  along an arterial line  106  and pushes the blood through dialyzer  102  and venous line  108 , back to patient  116 . The blood pump  120 , dialyzer  102 , arterial line  106  and venous line  108  are typically located at the front  12   a  of machine  12 . Machine front  12   a  is accordingly generally open and accessible to the nurse and patient and provides a convenient location  160  for one or more electrically insulated electrical socket  170 . In alternative embodiments, insulated socket location  160  is provided on any one or more of machine top  12   b,  machine sides  12   c  and  12   d  ( 12   d  not viewable in  FIG. 2 ), or machine backside  12   e.    
     In the illustrated embodiment, location  160  includes differently rated insulated electrical sockets  170   a,    170   b,  and  170   c  (referred to herein collectively as sockets  170  and generally, individually as socket  170 ). Sockets  170  may for example be dedicated to Universal Serial Bus (“USB”) charging  170   a,  12 VDC or 24 VDC charging  170   b,  or 120 VAC or 220 VAC charging  170   c.  Each socket  170   a,    170   b,  and  170   c  is accordingly dedicated to a particular voltage type of external electrical device  200 . The side section view of  FIG. 2  is only able to show a single (“USB”) socket  170   a,  a single 12 VDC or 24 VDC socket  170   b,  and a single 120 VAC or 220 VAC socket  170   c.  It should be appreciated that there may be a bank  162  of multiple (“USB”) sockets  170   a,  a bank  164  of multiple 12 VDC or 24 VDC sockets  170   b,  and a bank  166  of 120 VAC or 220 VAC sockets  170   c.    
     Referring now to  FIG. 3A , an exploded view of the socket bank location  160  of  FIG. 2  is illustrated. For ease of illustration, each of USB sockets  170   a,  12 VDC or 24 VDC sockets  170   b,  and 120 VAC or 220 VAC sockets  170   c  is illustrated as having a transformer  172  having a primary coil  174  and a secondary coil  176 . Each primary coil  174  is separated from a secondary coil  176  by an isolation barrier  178 , which may be air gap or gap filled with electrically resistive potting material. Isolation barrier  178  provides a conductive break, which conductively isolates components “downstream” from secondary coil  176 , including patient  116 , from any electrically connected component upstream of primary coil  174 , including mains voltage illustrated in  FIG. 2 . Primary coil  174  and secondary coil  176  are magnetically coupled, such that primary coil  174  induces a desired AC voltage in secondary coil  176 . 
     Primary coil  174  and secondary coil  176  of transformer  172  is one preferred way of isolating 120 VAC or 220 VAC sockets  170   c  and for providing the desired AC voltage for the power sockets. Patient  116  may use 120 VAC or 220 VAC sockets  170   c  for example to power a personal computer  200  using the patient&#39;s existing computer power cord. Computer power cords typically provide their own transformers, which output a desired voltage to the computer  200 . The transformers may provide their own electrical insulation, which in certain instances is unreliable. 120 VAC or 220 VAC sockets  170   c  provide reliable electrical insulation, which protects the patient even if the insulation of the computer cord transformer is faulty. 
     DC sockets  170   a  and  170   b  and their corresponding electrical isolation may be provided in a variety of different ways. In one embodiment the input DC voltage is converted to an input AC voltage using a DC to AC converter (illustrated in  FIG. 5 ). The input AC voltage is conductively isolated from an AC output voltage via a transformer  172  and its isolation barrier  178  as illustrated in  FIG. 3A , wherein primary coil  174  induces a desired AC output voltage in secondary coil  176 . An AC to DC converter (illustrated in  FIG. 5 ) is provided on the output side of transformer  172  to convert the induced AC output voltage to a desired DC output, e.g., 5 VDC, 12 VDC or 24 VDC. 
       FIG. 3B  shows a front view of  FIG. 3A , better illustrating banks  162 ,  164 , and  166  of electrically insulated sockets  170   a  to  170   c.  As illustrated, for example, there may be nine total sockets, with a bank  162  of three USB sockets  170   a,  a bank  164  of multiple 12 VDC or 24 VDC sockets  170   b,  and a bank  166  of 120 VAC or 220 VAC sockets  170   c.  Or perhaps there are multiple USB sockets  170   a,  multiple 12 VDC or 24 VDC sockets  170   b,  but only a single 120 VAC or 220 VAC socket. The combination of sockets may be chosen as desired to meet the most likely demand. 
     Referring now to  FIG. 4 , an alternative embodiment for providing DC sockets  170   a  and  170   b  is illustrated. Here, a DC to DC converter  180  receives system DC power, e.g., 24 VDC, via system power and power ground wires  182  and  184 , respectively. An input  180   a  of DC to DC converter  180  receives DC input power (e.g., 24 VDC) from system power and power ground wires  182  and  184 . Input  180   a  charges output  180   b  while being conductively isolated from output  180   b.  DC to DC converter  180  may perform the isolated charging in different ways as discussed below. 
     In any of the embodiments discussed above, transformer  172  may include a dedicated primary coil  174  for each output coil  176 . Alternatively, there may be a single primary coil  174  for multiple output coils  176 , where the output coils  176  may be of the same or different output voltage (e.g., different output coils may have different winding sizes and/or turns ratios to produce a different output voltage). For DC to DC conversion, a DC input voltage may be converted to an AC input voltage using a DC to AC converter, where the AC input voltage powers a common coil for multiple output coils, which each produce an AC output voltage. To this end, transformer  172  can have multiple windings or windings with several connection points (taps) on both the primary and secondary or output sides of transformer  172 . An AC to DC converter may also be provided for each AC output voltage to produce multiple DC output voltages each having a desired DC output level. For desired DC outputs, it is also contemplated to begin with an AC input voltage, induce an AC output voltage on output coil  176 , and convert the AC output voltage to a desired one or more DC output voltage. 
       FIG. 5  summarizes that machine  12  of system  10  may provide electrical insulation for any combination of electrically insulated sockets  170   a  to  170   c  via any combination of (i) straight AC to AC transformers  172 , (ii) straight DC to DC converters  180 , (iii) AC to AC transformers  172  in combination with AC to DC conversion  192 , (iv) AC to AC transformers  172  in combination with DC to AC conversion  194  and AC to DC conversion  192 , (v) AC to DC conversion  192  in combination with DC to DC conversion 180 , and (vi) DC to AC conversion  194  in combination with AC to DC conversion  192  without a transformer  172 . Other options providing galvanic separation for the patient include capacitive coupling for AC power, Hall effect sensors, and optical devices for DC power. 
       FIGS. 3A, 3B and 4  show in detail a first layer of electrical insulation between patient  116  and mains power provided by electrically insulated sockets  170   a,    170   b  and  170   c.    FIG. 2  illustrates a second layer of electrical insulation between patient  116  and mains power, namely, a mains transformer  152  having a mains input coil  154  and a mains output coil  156  separated by an isolation barrier  158 . Mains transformer  152  is located between mains power and the input or inputs to electrically insulated sockets  170   a,    170   b  and  170   c.  Isolation barrier  158  prevents the conducting of electricity, while input coil  154  induces a desired voltage in output coil  156 , as has been described above. 
       FIG. 2  illustrates that output coil  156  of mains transformer  152  powers the input sides of each of the transformers of electrically insulated sockets  170   a,    170   b  and  170   c.  This may occur if, for example, the output AC voltages at output coils  176  of the transformers  172  of DC sockets  170   b  and  170   c  are converted within the sockets using AC to DC converters  152  ( FIG. 5 ) to the desired DC voltages. Alternatively, output coil  156  of mains transformer  152  is split into an AC power circuit and one or more DC power circuit (not illustrated) using one or more AC to DC converter. Here, the output of the AC power circuit powers the inputs of electrically insulated AC socket  170   a,  while the one or more DC power circuit powers the inputs of electrically insulated DC sockets  170   b  and  170   c,  e.g., using isolated DC to DC. 
       FIG. 2  illustrates the double electrical insulation between external electrical device  200  and mains power as has just been described. Again, the double insulation helps to prevent the patient from being subjected to stray or fault voltages due for example to a faulty external electrical device  200 .  FIG. 2  also illustrates that system  10  provides additional electrical insulation, which helps to mitigate the effects of a stray or fault voltage that does occur due for example to a faulty external electrical device  200 . As illustrated in  FIG. 2 , machine impedance M imp  is made to be as large as possible so as to reduce the current resulting from a fault or stray voltage as much as possible. To do so, no connection is made between (ai) the blood in blood set, (aii) the dialysis fluid in fresh or used dialysis fluid lines, (aiii) the concentrates in concentrate lines, and (aiv) water in water lines (which may not be properly deionized, each of (ai) to (aiv) is considered to be at least somewhat conductive) and (b) machine or electrical earth  28 . As illustrated in  FIG. 1 , prior art machines are typically connected to protective earth  27  at multiple places, for example, in the used dialysis line just downstream of the dialyzer. Configured as described above, there is no physical connection to electrical earth  28  within the fluid pathways of system  10 , such that the pathways within the machine are said to be electrically floating, causing any fault or stray currents to flow through the increased machine impedance M imp  and through an external drain line  57  to electrical earth  28  at drain  60  located outside of machine  12 , thereby reducing the fault or stray current. 
       FIGS. 6 and 7  illustrate an embodiment of an electrically floating fluid pathway  140  of system  10 . System  10  in  FIG. 6  includes a machine  12  having an enclosure or housing. The housing may provide the insulated electrical socket  170  and described above. The housing of machine  12  holds the contents of a dialysis fluid or dialysis fluid circuit  30  described in detail below. The housing or machine  12  also supports a user interface  14 , which allows a nurse or other operator to interact with system  10 . User interface  14  may have a monitor screen operable with a touch screen overlay, electromechanical buttons, e.g., membrane switches, or a combination of both. User interface  14  is in electrical communication with at least one processor  16  and at least one memory  18 . At least one processor  16  and at least one memory  18  also electronically interact with, and where appropriate, control the pumps, valves and sensors described herein, e.g., those of dialysate circuit  30 . At least one processor  16  and at least one memory  18  are referred to collectively herein as a logic implementer  20 . The dashed lines extending from logic implementer  20  lead to pumps, valves, sensors, the heater and other electrical equipment, as indicated by like dashed lines leading from the pumps, valves, sensors, heater, etc. 
     Dialysis fluid circuit  30  includes a purified water line  32 , an A-concentrate line  34  and a bicarbonate B-concentrate line  36 . Purified water line  32  receives purified water from a purified water device or source  22 . The water may be purified using any one or more process, such as, reverse osmosis, carbon filtering, ultraviolet radiation, electrodeionization (“EDI”), and/or ultrafiltering. 
     An A-concentrate pump  38 , such as a peristaltic or piston pump, pumps A-concentrate from an A-concentrate source  24  into purified water line  32  via A-concentrate line  34 . Conductivity cell  40  measures the conductive effect of the A-concentrate on the purified water, sends a signal to logic implementer  20 , which uses the signal to properly proportion the A-concentrate by controlling A-concentrate pump  38 . The A-conductivity signal is temperature compensated via a reading from temperature sensor  42 . 
     A B-concentrate pump  44 , such as a peristaltic or piston pump, pumps B-concentrate from a B-concentrate source  26  into purified water line  32  via B-concentrate line  36 . Conductivity cell  46  measures the conductive effect of the B-concentrate on the purified water/A-concentrate mixture, sends a signal to logic implementer  20 , which uses the signal to properly proportion the B-concentrate by controlling B-concentrate pump  44 . The B-conductivity signal is also temperature compensated via a reading from temperature sensor  48 . 
     A water tank  50  holds purified water prior to receiving the concentrates, which has been degassed in a degassing chamber  51  via a degassing pump  53 , located below water tank  50 . A heater  52  controlled by logic implementer  20  heats the purified water for treatment to body temperature, e.g., 37° C. The fluid exiting conductivity cell  46  is therefore freshly prepared dialysis fluid, properly degassed and heated, and suitable for sending to dialyzer  102  for treatment. A fresh dialysis fluid pump  54 , such as a gear pump, delivers the fresh dialysis fluid to dialyzer  102 . Logic implementer  20  controls fresh dialysis fluid pump  54  to deliver fresh dialysis fluid to the dialyzer at a specified flowrate as described in more detail below. 
     A used dialysis fluid line  56  via a used dialysis fluid pump  58  returns used dialysis fluid from the dialyzer through an external drain line  57  to a drain  60 . Logic implementer  20  controls used dialysis fluid pump  58  to pull used dialysis fluid from dialyzer  102  at a specified flowrate. An air separator  62  separates air from the used dialysis fluid in used dialysis fluid line  56 . A pressure sensor  64  senses the pressure of used dialysis fluid within used dialysis fluid line  56  and sends a corresponding pressure signal to logic implementer  20 . 
     Conductivity cell  66  measures the conductivity of used fluid flowing through used dialysis fluid line  56  and sends a signal to logic implementer  20 . The conductivity signal of cell  66  is also temperature compensated via a reading from temperature sensor  68 . A blood leak detector  70 , such as an optical detector, looks for the presence of blood in used dialysis fluid line  56 , e.g., to detect if a dialyzer membrane has a tear or leak. A heat exchanger  72  recoups heat from the used dialysis fluid exiting dialysis fluid circuit  30  to drain  60 , preheating the purified water traveling towards heater  52  to conserve energy. 
     A fluid bypass line  74  allows fresh dialysis fluid to flow from fresh dialysis fluid line  76  to used dialysis fluid line  56  without contacting dialyzer  102 . A fresh dialysis fluid tube  78  extends from machine  12  and carries fresh dialysis fluid from fresh dialysis fluid line  76  to dialyzer  102 . A used dialysis fluid tube  80  also extends from machine  12  and carries used dialysis fluid from dialyzer  102  to used dialysis fluid line  56 . 
     Fresh dialysis fluid line  76  also includes a conductivity sensor or cell  82  that senses the conductivity of fresh dialysis fluid leaving a UF system  90  and sends a corresponding signal to logic implementer  20 . The conductivity signal of cell  82  is likewise temperature compensated via a reading from temperature sensor  84 . 
     An ultrafilter  86  further purifies the fresh dialysis fluid before being delivered via dialysis fluid line  76  and fresh dialysis fluid tube  78  to dialyzer  102 . Alternatively or additionally, one or more ultrafilter (additional ultrafilter is not illustrated) is used to purify the fresh dialysis fluid to the point where it may be used as substitution to perform from pre- or post-dilution hemofiltration or hemodiafiltration. 
     UF system  90  monitors the flowrate of fresh dialysis fluid flowing to dialyzer  102  (and/or as substitution fluid flowing directly to the blood set ( FIG. 2 )) and used fluid flowing from the dialyzer. UF system  90  includes fresh and used flow sensors Q 1   c  and Q 2   c,  respectively, which send signals to logic implementer  20  indicative of the fresh and used dialysis fluid flowrate, respectively. Logic implementer  20  uses the signals to set used dialysis fluid pump  58  to pump faster than fresh dialysis fluid pump  54  by a predetermined amount to remove a prescribed amount of ultrafiltration (“UF”) from the patient over the course of treatment. Fresh and used flow sensors Q 1   p  and Q 2   p  are redundant sensors that ensure UF system  90  is functioning properly. 
     System  10  provides plural valves  92  (referring collectively to valves  92   a  to  92   k ) under the control of logic implementer  20  to selectively control a prescribed treatment. In particular, valve  92   a  selectively opens and closes bypass line  68 , e.g., to allow disinfection fluid to flow from fresh dialysis fluid line  76  to used dialysis fluid line  56 . Valve  92   b  selectively opens and closes fresh dialysis fluid line  76 . Valve  92   c  selectively opens and closes used dialysis fluid line  56 . Valve  92   d  selectively opens and used dialysis fluid line  56  to external drain line  57  and drain  60 . Valve  92   e  selectively opens and closes purified water line  32  to purified water source  22 . Valves  92   f  and  92   g  control A- and B-concentrate flow, respectively. Valves  92   h  to  92   k  operate with UF system  90 . 
     It should be appreciated that the dialysis fluid circuit  30  is simplified and may include other structure (e.g., more valves) and functionality not illustrated. Also, dialysis fluid circuit illustrates a hemodialysis (“HD”) pathway. It is contemplated to provide an additional ultrafilter (not illustrated) in fresh dialysis fluid line  76  to create substitution fluid for hemofiltration (“HF”). It is also contemplated to provide one or more ultrafilter in one or more line(s) branching off of fresh dialysis fluid line  76  to create substitution fluid, in addition to the fresh dialysis fluid in line  76 , for hemodiafiltration (“HDF”). 
     Referring now to  FIG. 7 , blood circuit or set  100  illustrates one embodiment of a blood set that may be used with either system  10 . Blood circuit or set  100  includes a dialyzer  102  having many hollow fiber semi-permeable membranes  104 , which separate dialyzer  102  into a blood compartment and a dialysis fluid compartment. The dialysis fluid compartment during treatment is placed in fluid communication with a distal end of fresh dialysis fluid tube  78  and a distal end of used dialysis fluid tube  80 . For HF and HDF, a separate substitution tube, in addition to fresh dialysis fluid tube  78 , is placed during treatment in fluid communication with one or both of arterial line  106  extending from an arterial access  106   a  and venous line  108  extending to a venous access  108   a.  In HDF, dialysis fluid also flows through dialysis fluid tube  78  to dialyzer  102 , while for HF, dialysis fluid flow through tube  78  is blocked. 
     An arterial pressure pod  110  may be placed upstream of blood pump  120 , while venous line  108  includes a venous pressure pod  112 . Pressure pods  110  and  112  operate with blood pressure sensors (not illustrated) mounted on the machine housing, which send arterial and venous pressure signals, respectively, to logic implementer  20 . Venous line  108  includes a venous drip chamber  114 , which removes air from the patient&#39;s blood before the blood is returned to patient  116 . 
     Arterial line  106  of blood circuit or set  100  is operated by blood pump  120 , which is under the control of logic implementer  20  to pump blood at a desired flowrate. System  10  also provides multiple blood side electronic devices that send signals to and/or receive commands from logic implementer  20 . For example, logic implementer  20  commands pinch clamps  122   a  and  122   b  to selectively open or close arterial line  106  and venous line  108 , respectively. A blood volume sensor (“BVS”)  124  is located along arterial line  106  upstream of blood pump  120 . Air detector  126  looks for air in venous blood line  108 . 
     To create the electrically floating dialysis fluid circuit  30 , sensitive equipment, such as conductivity sensors  40 ,  46 ,  66  and  82 , which are normally connected directly or indirectly to protective earth  27 , are instead left floating with respect to protective earth  27  or other earth within machine  12 . Likewise, the flow sensors Q 1   c,  Q 2   c,  Q 1   p,  and Q 2   p  of UF system  90  are not connected to protective earth. In the illustrated embodiment, nowhere within machine  12  is electrically floating dialysis fluid circuit  30  or the floating blood set  100  physically connected to protective earth  27  or other electrical earth. Thus, dialysis fluid circuit  30  and the blood set  100  (including arterial line  106 , venous line  108 , and patient access or needles  106   a,    108   a ) with respect to machine  12  are said to be electrically floating. 
     The sensitive equipment, however, is in the prior art connected to protective earth  27  for a reason, namely, if not properly earthed, stray current from outside or inside the machine or a faulty component may cause the conductivity and flow sensors to read or output improperly. To combat this problem without connecting the sensors to protective earth  27 , the sensors of the present disclosure are provided with electrical bypass lines  150  as illustrated in  FIG. 6 . Bypass lines  150  electrically bypass the sensing equipment, from a point upstream of the sensors to a point downstream of the sensors, so that fault currents conduct from upstream to downstream of each sensor, or vice versa, through electrical bypasses  150  and not the sensing equipment. In doing so, bypass lines  150  electrically contact, or are otherwise in electrical communication with, fluid upstream of the sensors and fluid downstream of the sensors, creating a short circuit around the sensors. The short circuit causes stray currents to bypass the sensors, so that the stray currents do not affect the operation of the sensors. 
     Additionally, the sensors and any other flow component conductively touching liquid in the dialysis fluid circuit  30  and the blood set  100  is electrically insulated from the remainder of machine  12  via mechanical insulation. Mechanical insulation refers to the use of a non-conductive material, e.g., plastic, rubber, ceramic, and combinations thereof, placed between the fluid contacting component and the machine. The result may be an insulating pad located between the component and the machine chassis or other machine fixture to which the component is mounted. 
     Besides, the “mechanical” electrical insulation, to make the dialysis fluid circuit  30  and the blood set  100  floating, electrical power wires and electrical signal wires that conduct signals away from the sensor probes or other structures that contact the blood, dialysis fluid or concentrate, for example, need to be electrically isolated from the circuitry and computational devices that read and analyze the sensor signals, e.g., printed circuit boards, processing, memory (discussed above as logic implementer  20 ). To do so, each power and signal wire stemming from a sensor is in one embodiment isolated via a transformer (or any of the described above for electrically insulated sockets  170   a  to  170   c ) from a power or signal wire, respectively, that extends from the transformer or other electrically insulating device to logic implementer  20  or power source. The transformers or other electrically insulating devices pass along the information carried by the sensor signal wiring, while creating a physical break in the signal lines. The physical breaks prevent (i) stray currents from machine  12  from entering the electrically floating fluid pathway  140  via the sensor power or signal lines and (ii) stray currents within floating fluid pathway  140  from exiting out to machine  12  and its other components via the sensor power or signal lines. 
     So to make the dialysis fluid circuit  30  and the blood set  100  electrically floating within machine  12 , four features may be ensured: (i) no connection from a conductive fluid path to protective earth  27  or other electrical earth is made within machine  12  or in the blood set  100 , (ii) sensitive equipment that touches conductive water, concentrate, dialysis fluid and/or blood in dialysis fluid circuit  30  and blood in blood set  100  is electrically bypassed, (iii) components that contact liquid are “mechanically” electrically insulated when mounted, and (iv) signal wires to or from logic implementer  20  are electrically isolated. 
     The above-described combination of different electrical insulation provides a significantly safer renal failure therapy system  10  versus known systems. It should be appreciated that the insulated electrical sockets of the present disclosure do not have to be used with the electrically floating fluid pathway  140 , and vice versa, and that each make system  10  safer even if used alone. The present disclosure therefore does not require such combination. 
     ELEMENT NUMBER LISTING 
     
         
         known dialysis machine  8   
         renal failure therapy system  10   
         renal failure therapy machine  12   
         user interface  14 , 
         at least one processor  16 , 
         at least one memory  18 , 
         logic implementer  20 , 
         purified water device or source  22 , 
         A-concentrate source  24 , 
         B-concentrate source  26 , 
         machine protective earth  27 , 
         electrical earth  28 , 
         dialysis fluid circuit  30 , 
         purified water line  32 , 
         A-concentrate line  34 , 
         B-concentrate line  36 , 
         A-concentrate pump  38 , 
         conductivity cell  40 , 
         temperature sensor  42 , 
         B-concentrate pump  44 , 
         conductivity cell  46 , 
         temperature sensor  48 , 
         water tank  50 , 
         degassing chamber  51 , 
         dialysis fluid heater  52 , 
         degassing pump  53 , 
         fresh dialysis fluid pump  54 , 
         used dialysis fluid line  56 , 
         external drain line  57 , 
         used dialysis fluid pump  58 , 
         drain  60 , 
         air separator  62 , 
         pressure sensor  64 , 
         dialyzer  102 , 
         conductivity cell  66 , 
         temperature sensor  68 , 
         blood leak detector  70 , 
         heat exchanger  72 , 
         fluid bypass line  74 , 
         fresh dialysis fluid line  76 , 
         fresh dialysis fluid tube  78 , 
         used dialysis fluid tube  80 , 
         conductivity cell  82 , 
         temperature sensor  84 , 
         ultrafilter  86 , 
         UF system  90 , 
         plural valves  92  (collectively to valves  92   a  to  92   k ), 
         blood circuit or set  100 , 
         dialyzer  102 , 
         semi-permeable membranes  104 , 
         arterial line  106 , 
         arterial access or needle  106   a,    
         venous line  108 , 
         venous access or needle  108   a,    
         arterial pressure pod  110 , 
         venous pressure pod  112 , 
         venous drip chamber  114 , 
         patient  116 , 
         blood pump  120 , 
         pinch clamps  122   a  and  122   b,    
         blood volume sensor (“BVS”)  124 , 
         air detector  126 , 
         floating fluid pathway  140 , 
         electrical bypass lines  150 , 
         mains transformer  152 , 
         mains input coil  154 , 
         mains output coil  156 , 
         isolation barrier  158 , 
         location  160  for electrically insulated sockets  170 , 
         banks  162 ,  164 , and  166  of electrically insulated sockets  170 , 
         electrically insulated electrical sockets  170  (collectively to sockets  170   a  to  170   c ), 
         AC to AC transformer  172 , 
         primary coil  174 , 
         secondary coil  176 , 
         isolation barrier  178 , 
         DC to DC converter  180  having input  180   a  and output  180   b,    
         power wire  182 , 
         power ground wires  184 , 
         AC to DC conversion  192 , 
         DC to AC conversion  194   
         external electrical device  200   
       
    
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the present invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.