Abstract:
A portable peritoneal dialysis system having a dual voltage heating system that automatically reconfigures the heating circuit depending upon detection of either 110 VAC or 220 VAC to deliver the same wattage for heating PD solution before delivery to the patient, thus facilitating use of the same machine in the United States and Europe.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to peritoneal dialysis systems and related methods. 
       BACKGROUND 
       [0002]    The present invention relates generally to apparatus for performing peritoneal dialysis on patients with insufficient kidney function, and in particular to heating circuitry for peritoneal dialysis machines designed to accommodate different line or mains voltages, including 10 volts AC (VAC) in the United States and 220 VAC in Europe. 
         [0003]    Peritoneal dialysis (“PD”) utilizes the patient&#39;s own peritoneum (a membranous lining of the abdominal body cavity) acting as a natural semi-permeable membrane. In PD the abdominal or peritoneal cavity of the patient is filled or infused with a sterile aqueous solution called PD solution which is removed or drained after a period of time. PD solution is analogous to dialysate used in hemodialysis; but there are significant differences in the formulations as well as in the process itself. In PD exchanges take place via diffusion and osmosis between the blood stream, i.e., the arterial and venous capillary beds in or near the peritoneum, and the resident reservoir of PD solution itself in the abdomen. Several exchanges may be performed, in a fill-dwell-drain cycle. These exchanges remove toxic waste products, such as urea and creatinine, that each kidney normally excretes into the ureter along with excess water that has built up in the patient&#39;s blood stream in the absence of normal kidney function. The kidneys also function to maintain the proper levels of other substances, such as sodium, which are regulated by dialysis to attempt to maintain the proper balance of electrolytes. The diffusion of water and solutes across the peritoneal membrane during dialysis is sometimes called ultrafiltration. 
         [0004]    In continuous ambulatory PD (CAPD), a dialysis solution is introduced into the peritoneal cavity utilizing a special permanent catheter inserted through the abdominal wall. After filling, the solution is left in place to accomplish dialysis for a dwell period typically on the order of one or more hours, and then removed by draining it out through the same catheter. The process is repeatable. 
         [0005]    Automated PD machines called PD cyclers are designed to control the entire process so that it can be performed at home usually overnight without clinical staff in attendance. This process is termed continuous cycler-assisted PD (CCPD). The cyclers are designed to manage a number of solution bags each typically containing up to 5 liters of PD solution, which the machine pumps or, in so-called gravity systems, allows to flow through a patient line to the patient. But, to avoid thermal shock, the PD solution always has to be heated first to near the patient&#39;s body temperature before infusion. 
         [0006]    One technique for heating the PD solution is to place a dedicated heater bag on top of a heater tray, equipped with heating coils and a temperature sensor. In this arrangement all fluid going to the patient must come from the heater bag. During the dwell period, the heater bag can be refilled from one of several PD solution bags connected to the machine and warmed so that it will be ready to supply the next fill to the patient. 
         [0007]    Accommodating varying line voltages encountered world-wide presents a special challenge for the heating circuitry that the present invention is designed to overcome. 
       SUMMARY 
       [0008]    Briefly, in one aspect the invention relates to an apparatus for pumping pre-heated fluids between a peritoneal dialysis machine and a patient in order to perform peritoneal dialysis and in particular to an automatic system for detecting 110 or 220 line voltage and safely reconfiguring the connections to the PD solution heater elements in a peritoneal dialysis machine. 
         [0009]    The invention may include a portable peritoneal dialysis machine, comprising a source of PD solution, a patient line for passing PD solution to and from the patient&#39;s abdominal cavity, a cycler for delivering a predetermined quantity of PD solution to the patient&#39;s abdomen via the patient line, a heater including a series connected heating elements for heating the PD solution before delivering it to the patient, a voltage detection circuit connected to detect the line voltage and produce an output indicative of the line voltage to a switch circuit that applies 220 VAC across both elements in series or 110 VAC through the elements in parallel. This arrangement assures that approximately the same wattage is automatically produced by the heater under either 220 VAC or 110 VAC so that the PD solution is heated at approximately the same rate under either voltage. 
         [0010]    In one embodiment the heater coils, preferably resistive heating coils, are paired so that under 110 VAC the line voltage is applied to the center tap. The voltage detection circuit preferably has two complementary mutually exclusive logic outputs, one indicating the presence of 220 VAC line current when in one state and the other indicating the presence of 110 VAC line current when in one state. 
         [0011]    In one embodiment, the PD solution is heated in a heater bag mounted on a tray on the cycler, the heater being juxtaposed with the tray, for example by embedding resistive heating coils in the tray, to warm the heater bag. 
         [0012]    In another embodiment a set of auxiliary heating elements also connected in series and the switch circuit applies 220 VAC across the auxiliary as well as the main heating elements in series or 110 VAC through the auxiliary as well as the main heating elements in parallel. In one embodiment the switch circuit includes a plurality, e.g., four, power switches controlled by a switch control circuit that is responsive to a separately generated control signal that causes the switches to connect the line voltage and neutral to the heating elements to start or stop warming the PD solution. The plurality of switches may include first, second, third and fourth switches, the first switch connecting 220 line voltage when closed to the end of one of the heating elements, the second switch connecting the end of the of the heating elements to neutral when closed, the third switch connecting line voltage to the center tap when closed and the fourth switch connecting the end of the other heating element to neutral when closed, the switch control circuit closing the second, third and fourth switches when the output of the voltage detection circuit indicates that line voltage is 110 VAC, and closing the first and fourth switches when the output of the voltage detection circuit indicates that line voltage is 220 VAC. 
         [0013]    Another aspect of the invention includes a method of performing peritoneal dialysis, comprising providing a plurality of interconnected heating elements arranged to heat the PD solution prior to infusion, automatically detecting the line voltage and reconfiguring the connection between a plurality of interconnected heating elements with the line voltage and neutral in response to the detected line voltage to supply the same wattage for heating the PD solution under at least two substantially different line voltages, heating the PD solution with the reconfigured heating elements, and then infusing the patient with the warmed PD solution. Preferably, the reconfiguring step automatically applies line voltage across the heating elements in series at one line voltage and in parallel at another line voltage. 
         [0014]    Advantages of the invention include the following. Automatic voltage detection and switching between heater circuits makes it possible to supply and distribute the same PD cycler in all places having voltages in a wide range without modification of the circuitry. One of the advantages of PD cyclers is their portability. Patients do occasionally travel with them. Thus, for example, a dialysis patient is free to travel from the United States to Europe, or vice versa, with his or her regular PD cycler equipped with the heater circuitry of the present invention and not have to worry about the voltage, except possibly for a plug adapter or carrying an alternate power cord. 
         [0015]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
     
       DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is a perspective view of a PD cycler on a special cart with a heater bag on the heater tray and additional PD solution bags for more exchanges hanging off the cart. 
           [0017]      FIG. 2  is a perspective top view showing the heater tray of the PD cycler of  FIG. 1 . 
           [0018]      FIG. 3  is a rear view of the PD cycler of  FIG. 1  showing the ON/OFF switch and power cord. 
           [0019]      FIG. 4  is a block diagram with an overview of the AC voltage heater control circuit associated with the heater tray of the PD cycler of  FIGS. 1-3 . 
           [0020]      FIG. 5  is a block diagram of the heater control circuit of  FIG. 4  in the 110 VAC mode. 
           [0021]      FIG. 6  is a block diagram of the heater control circuit of  FIG. 4  in the 220 VAC mode. 
           [0022]      FIG. 7  is a top level block diagram of a specific embodiment of the AC distribution board for implementing the heater circuit system of  FIGS. 4-6 . 
           [0023]      FIG. 8  is a detailed electrical schematic diagram of the power line interface with voltage detector for the board of  FIG. 7 .  FIG. 8  is divided into three subfigures,  FIGS. 8A ,  8 B and  8 C, whose interrelationship is indicated by the diagram in  FIG. 8  and by the circled letters designating lines that interconnect across two subfigures. The same protocol is used for  FIGS. 9 and 10 . 
           [0024]      FIG. 9  is a detailed electrical schematic diagram of the heater control logic for the board of  FIG. 7 . 
           [0025]      FIG. 10  is a detailed electrical schematic diagram of the set of heater relays (triac line switches) for the board of  FIG. 7 . 
           [0026]      FIG. 11  is a representative electrical schematic diagram of one of the triac solid state relays of  FIG. 10 . 
       
    
    
       [0027]    Like reference symbols in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0028]    The heater circuit embodiment described below is specifically designed for PD cyclers of the type disclosed in U.S. patent application Ser. No. 11/069,195, filed Feb. 28, 2005, entitled “Portable Apparatus for Peritoneal Dialysis Therapy,” which is incorporated by reference herein in its entirety. The foregoing application is assigned to the same assignee and describes certain details of an embodiment of the PD cycler shown in  FIG. 1 . 
       The Cycler 
       [0029]    In  FIG. 1 , a portable PD cycler  10  is shown seated on top of a cart  12  designed to accommodate the PD solution bags and associated tubing. The front of the cycler  10  includes a control panel  12  that furnishes a user interface designed to be operated by the patient along with a pressurized cassette compartment behind a hinged door  14 . The cassette (not shown) includes channels, flexible valve domes and diaphragm covered pumping chambers that are actuated by mating pneumatic valves and pistons interfacing with the cassette compartment to route the flow of PD solution from the bags through the cycler and to the patient and from the patient to a drain. The cassette and cassette compartment are disclosed in more detail in the above-referenced application Ser. No. 11/069,195. The cassette itself has tubing connectors  16  arrayed along its bottom edge. The connectors extend beneath the door  14  and are connected to tubing as shown in  FIG. 1 . 
         [0030]    PD solution bags  18  are suspended from fingers on the sides of the cart  12  as shown. A heater bag  20  is shown lying in a shallow concave depression forming the heater tray  22 , which is sized and shaped to accommodate a typical 5 L bag of PD solution. The heater tray  22  has a plurality of heating coils (not shown) embedded below the surface. The surface of the tray  22 , as better shown in  FIG. 2 , is slightly inclined downward to the right to assist in emptying the heater bag which is arranged so that the outlet of the heater bag is also at the right side, adjacent to a temperature sensor  24  positioned in the surface of the heater tray  22  to track the temperature of the solution in the heater bag for a thermostatic control circuit that turns the heating coils on and off as needed to maintain the PD solution at the desired temperature. The heater tray  22  is also mounted internally on a support equipped with a load cell (not shown) to provide an electrical signal indicating the weight of the contents of the PD solution bag to tell the cycler control system how full the heater bag is with PD solution. 
         [0031]    As shown in  FIG. 3 , the rear panel  26  of the cycler  10  carries a power cord socket  28  for a detachable power cord  30  with a three prong grounded plug, shown here as an American 110 VAC plug. For use in Europe, a similar power cord with a plug designed for use with 220 VAC line current would ordinarily be simply substituted. Absent the cord one could simply use a suitable 3-prong plug adapter as well. Above the socket  28  is the ON/OFF master power switch  32  for the cycler  10 . The rear panel also can include a fan vent  34  and various data ports, for example. 
       The Heater Circuit 
       [0032]      FIGS. 4-6  represent an overview of the general operation of the heater circuit under either 110 or 220 VAC,  FIGS. 7-11  being detailed schematics of an implementation or embodiment of the circuitry for purposes of illustration. 
         [0033]    As shown in the upper right portion of  FIG. 4 , incoming AC line voltage is delivered via a voltage-agnostic power entry module  40  to the AC distribution board  42 . Preferably, the circuitry may be designed to handle any voltage between 85 and 265 VAC at 50 to 60 Hz. The AC distribution board includes a 110 v/220 v detector  44  whose output it a binary logic value for which one level indicates that the line current is 110 VAC and the other level indicates that it is 220 VAC. As shown in  FIG. 4  the output of the voltage detector  44  can be passed to the 110 v mode controller  46 . The output of the voltage detector  44  is also passed via an inverter  48  to a 220 v mode controller circuit  50  to insure that only one mode,  110  or  220 , can be activated at a time. The output of the active mode controller  46  or  50  energizes a heater control circuit  52  that gates current through the heating coils of the heater tray  56 , in different ways depending on the line voltage, in response to ON/OFF signals from the I/O board heater ON/OFF controller  54 . Controller  54  is responsive to the temperature sensor  24  to control the ON/OFF cycling of the heater coils to maintain a set temperature in the heater bag while also under the command of the cycler control system to start and stop temperature control in an appropriate energy-efficient manner. For example, once the last bag has been warmed and dispensed to the patient, the heater ON output from the I/O board could be disabled by the cycler control system. 
         [0034]      FIGS. 5 and 6  show the result of the detection of 110 or 220 line voltage, respectively, on the connections between the power line and the heating coils.  FIG. 5  corresponds to the regime when the available line current is 110 VAC. The heater tray  56  includes, by way of illustration, a pair of matched 50 ohm heating coils  60  and  62 , connected in series via a center tap  64 . Power enters the AC distribution board  42  on two wires or rails, line voltage and neutral. In  FIG. 5  the 10 VAC line is shown at the top and the neutral line or rail is shown at the bottom. Line and neutral connections to the heating coils are accomplished via a set of four switches, numbered the same for illustration in  FIGS. 5 and 6  as switches Nos.  1 ,  2 ,  3  and  4  that can either be open (non-conducting) or closed (conducting) depending on signals from the heater switch control  52 . To illuminate the different modes, the output lines from the heater switch control  52  in both  FIGS. 5 and 6  are only indicated for closure of the switches, not for opening. Switch # 1  is the 220 v line switch and is open in the 10 mode ( FIG. 5 ). Switch # 2  is the 110 v neutral switch and is closed in the 110 mode. Switch # 3  is the 110 v line switch. In 110 v mode, corresponding line switch # 3  is closed (conducting). The last switch # 4  is the neutral isolation switch which is closed in both 110 and 220 modes. Thus, in the 110 VAC mode ( FIG. 5 ) when the I/O board heater controller  54  applies a heater ON signal to the heater control  52  indicating that the cycler control system is commanding the heater to warm up the heater bag and the sensed temperature is below the desired set point, switches Nos.  2 ,  3  and  4  are closed and switch # 1  is opened. This switch configuration accomplishes the following in the 110 v mode: the 10 VAC line is connected to the center tap  64  via switch # 3  while then distal ends of the heater coils  60  and  62  are both connected to neutral via switches Nos.  2  and  4 . This configuration passes full  10  VAC current in opposite directions through the respective 50 ohm coils to produce approximately 500 watts of power at 118 VAC. Accordingly when in the 110 v mode, switch # 3  closes becoming the center tap/line voltage and switches  2  and  4  close, becoming the neutral return paths, also thereby putting the heater coils  60  and  62  in parallel. 
         [0035]    Alternatively, as shown in  FIG. 6 , in the 220 v mode, switches Nos.  1  and  4  are closed by the heater switch control  52 . Switch # 1  supplies line voltage to the end of coil  60  and switch # 4  connects the opposite end of the other coil  62  to neutral return, thus putting line voltage across both heater coils in series, i.e., the 220 VAC current (in one direction) flows through coil  60  then through coil  62  and then returns to neutral (ground). This configuration can generate approximately 475 watts at 220 VAC. 
         [0036]      FIGS. 7-11  illustrate a preferred specific embodiment of an AC distribution board for the PD heater tray voltage-switched control system developed for a specific heater coil arrangement consisting of two pairs of coils, one designated as an optional auxiliary heater coil pair, for example, of lesser resistance for finer control of the heater bag temperature.  FIG. 7  is a top level block diagram of the AC distribution board showing the relationship and signal paths between the three major functional blocks of the circuitry. First, power line circuit  70  filters the AC line, detects the line voltage and provides low voltage DC supply power at 5 and 18 VDC for internal circuit operation. The middle block heater control logic  72  corresponds to heater mode control  52  in  FIGS. 4-6 , taking its cue from the detected voltage level to provide logical outputs to operate the switches to make the series or parallel connection of the heater coils to line voltage and neutral. The last block, shown on the right in  FIG. 7 , comprises the heater relays that, under control of the heater control logic block  72 , pass current to either the center tap or one end of the series connected coils. But first current must pass through a circuit breaker built into the heater coil assembly (not shown). An additional protective ground is provided which is connected to the longer grounding pin on the standard three-prong plug on power cord  30  ( FIG. 3 ) 
         [0037]    As shown in  FIG. 8  the power line interface connects via connector J 2  to the power cord  30 . LINE and NEUTRAL are connected via protective Zener breakdown diode as shown to furnish the HEATER LINE and NEUTRAL LINE which are fed to both the heater control logic circuit  72  and the relay control circuit  74  by which they are connected directly to the heating coils. LINE is tapped by line A (circled) in  FIGS. 8A and 8B  for the voltage detector  76  and line frequency CLK  78  circuits in  FIG. 8B  and the 5 and 18 volt DC power supplies  79  in  FIG. 8C . The heart of the voltage detector  76  is an integrated circuit U 1  that produces the output designated DET — 120V_N whose logic value is low when LINE is 110 VAC. 
         [0038]    In the heater control logic of  FIG. 9 , a heater control and status isolated interface  80  is provided by the four opto-couplers shown in  FIG. 9A . The HEATER_BKR input to the operational amplifier U 4 D comes via the rectified output of the circuit breaker in the heater tray from  FIG. 10A  of the relay control circuit. The portion of the heater control logic shown in  FIG. 9B  is designed to reset the flip-flop U 3 A on power up and inhibit output on low voltage. This circuit takes as inputs the DET — 120_N output of the voltage detector and LINE_CLK of  FIG. 8 . Flip-flop U 3 A stores the state of the voltage until reset. The output of flip-flop U 3 A is applied via flip-flop U 6  to a set of three gates U 7 A, U 7 B and U 7 C that produce the basic inputs to the relay circuit  74 , namely 240V_ON, 110V_ON and AUX_ON. The 240V_ON and 110V_ON signals are gated by HEATER_ON signals generated by the I/O board heater ON/OFF controller  54  ( FIG. 4-6 ) and passed from the connector J 3  via the opto-coupler  80  in  FIG. 9A . The AUX_ON signal, if used, is generated by the I/O board heater controller as well and passed from connector J 3  via the opto-coupler as called for by the cycler control system. 
         [0039]    The relay signals  82  for the auxiliary heater relays and signals  84  for the 120 v line relays and  86  for the 220 v line relays are shown in  FIG. 9C , along with their associated service LED&#39;s. 
         [0040]    The relay control signals generated by the logic circuit of  FIG. 9  are passed to the triac solid state switch array shown in  FIG. 10A . Connections to the heater coils are indicated in  FIG. 10B  via the lines with the circled letters A-H. Note the heater plate assembly includes thermal circuit breaker with terminals  1  and  2 . Thermal Bkr 1  is connected directly to HEATER_LINE (i.e., line current from the power cord  30 ) and Thermal Bkr  2  in  FIG. 10B  is connected directly to the 220 v and 110 v line switches in  FIG. 10A  via line C. Thus current flows from the HEATER_LINE through the circuit breaker and back through either the 10 or 220 V Line switch before going to the center tap or end of the coil pair, depending on the state of the relays depending on line voltage, then through the coils and then returning to neutral through HTR Neutral in  FIG. 10B . 
         [0041]    The optional auxiliary heater coils, if activated by AUX_ON ( FIG. 9B ), operate the same way in parallel but have lower resistance than the main heater coils. 
         [0042]    The invention has been described in terms of particular embodiments. Other embodiments are within the scope of the following claims. For example, while coil pairs are disclosed for the heater, any plurality of series connected coils which can be energized alternately in series or in parallel can be implemented. In addition, while the embodiments shown above involve a heater bag standing on a heater tray, a solution bag can empty its contents through an on-the-fly heater en route to the patient line, for example taking several maze like turns around a heating plate. The same solution for dual voltage adjustment can accommodate this flow through heating system as well as the stationary heater bag. Further, the above described embodiments are designed to be used with a PD cycler. However, the invention can be used on any type of peritoneal dialysis machine that preheats PD solution before infusion. The terms 110 VAC and 220 VAC used herein are intended to designate voltages within the ranges commonly encountered today as line current in the United States and Europe, respectively. 
         [0043]    A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.