Patent Document

PRIORITY CLAIM 
     This application is a continuation of U.S. patent application Ser. No. 10/446,068, filed May 27, 2003, entitled “Method And Apparatus For Monitoring And Controlling Peritoneal Dialysis Therapy,” which is a divisional application of U.S. patent application Ser. No. 10/078,568, filed Feb. 14, 2002, having the same title as above, issued as U.S. Pat. No. 6,592,542, which is a continuation of U.S. patent application Ser. No. 09/501,778, filed Feb. 10, 2000, having the same title as above, issued as U.S. Pat. No. 6,497,676. Both disclosures are hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     The present invention relates generally to the treatment of end stage renal disease. More specifically, the present invention relates to methods and apparatus for monitoring the performance of peritoneal dialysis. 
     Using dialysis to support a patient whose renal function has decreased to the point where the kidneys no longer sufficiently function is known. Two principal dialysis methods are utilized: hemodialysis; and peritoneal dialysis. 
     In hemodialysis, the patient&#39;s blood is passed through an artificial kidney dialysis machine. A membrane in the machine acts as an artificial kidney for cleansing the blood. Because it is an extracorporeal treatment that requires special machinery, certain inherent disadvantages exist with hemodialysis. 
     To overcome the disadvantages associated with hemodialysis, peritoneal dialysis was developed. Peritoneal dialysis utilizes the patient&#39;s own peritoneum as a semi-permeable membrane. The peritoneum is a membranous lining of the abdominal body cavity. Due to good perfusion; the peritoneum is capable of acting as a natural semi-permeable membrane. 
     Peritoneal dialysis periodically infuses sterile aqueous solution into the peritoneal cavity. This solution is called peritoneal dialysis solution, or dialysate. Diffusion and osmosis exchanges take place between the solution and the blood stream across the natural body membranes. These exchanges remove the waste products that the kidneys normally excrete. The waste products typically consist of solutes like urea and creatinine. The kidneys also maintain the levels of other substances such as sodium and water which need to be regulated by dialysis. The diffusion of water and solutes across the peritoneal membrane during dialysis is called ultrafiltration. 
     In continuous ambulatory peritoneal dialysis, a dialysis solution is introduced into the peritoneal cavity utilizing a catheter. An exchange of solutes between the dialysate and the blood is achieved by diffusion. Further removal is achieved by providing a suitable osmotic gradient from the blood to the dialysate to permit water outflow from the blood. This allows a proper acid-base, electrolyte and fluid balance to be achieved in the body. The dialysis solution is simply drained from the body cavity through the catheter. 
     Peritoneal dialysis raises a number of concerns including: the danger of peritonitis; a lower efficiency and therefore increased duration of dialysis hours compared to hemodialysis; and costs incurred when automated equipment is utilized. 
     A number of variations on peritoneal dialysis have been explored. One such variation is automated peritoneal dialysis (“APD”). APD uses a machine, called a cycler, to automatically infuse, dwell, and drain peritoneal dialysis solution to and from the patient&#39;s peritoneal cavity. APD is particularly attractive to a peritoneal dialysis patient, because it can be performed at night while the patient is asleep. This frees the patient from the day-to-day demands of continuous ambulatory peritoneal dialysis during his/her waking and working hours. 
     The APD sequence typically lasts for several hours. It often begins with an initial drain cycle to empty the peritoneal cavity of spent dialysate. The APD sequence then proceeds through a succession of fill, dwell, and drain phases that follow one after the other. Each fill/dwell/drain sequence is called a cycle. APD can be and is practiced in a number of different ways. 
     Current APD systems do not monitor the patient intraperitoneal pressure during a therapy session. Current systems simply limit the external pressure (or suction) that a pump can apply to the line or lumen that is attached to the patient catheter. If the patient is located below the system, sometimes referred to as a cycler, a gravity head will add to the positive fill pressure that the cycler can apply to the patient catheter. Conversely, if the patient is located above the cycler, the gravity head will decrease from the positive fill pressure that the cycler can apply to the patient catheter. 
     The monitoring of intraperitoneal pressure would be useful because cyclers will sometimes not fully drain a patient between cycles. Specifically, currently-available cyclers are unable to determine whether a patient absorbed some fluid or whether some fluid is simply not able to be drained out because of the position of the patient or the catheter. 
     As a result, some currently-available systems utilize a minimum drain threshold to determine the amount of fluid that should be delivered to the patient during the next fill. For example, if 85% of the fill volume has been drained when the cycler determines that the patient is “empty”, the next fill volume will be 100%. If only 80% were drained, the next fill volume would be limited to 95%. 
     A negative ultrafiltrate (uF) alarm will sound when the patient has retained more than a predetermined percentage of the fill volume. The predetermined percentage can typically be either 50% or 100% of the fill volume. However, the patient can override this alarm if he/she does not feel overfull. The number of times the patients can override the uF alarm during a single therapy may be limited by the software of the cycler. However, the uF alarm typically does not consider the actual ultrafiltrate that may also accumulate in the peritoneal cavity along with the dialysate. 
     Currently-available cyclers fill the patient to a specific, preprogrammed volume during each cycle. The doctor prescribes this fill volume based upon the patient&#39;s size, weight and other factors. However, because currently-available cyclers cannot monitor intraperitoneal pressure, the doctor cannot take this factor into account when formulating the prescription. It is also known that intraperitoneal pressure (IPP) has an effect on ultrafiltration (UF). 
       FIGS. 1-3  provide schematic illustrations of current APD cyclers. None of them attempt to monitor intraperitoneal pressure. 
     Referring to  FIG. 1 , a cycler  10   a  is illustrated which includes a dialysate container  11 , a patient  12  and a drain container  13  are illustrated schematically. The infusion of dialysate from the container  11  into the patient  12  is caused by the gravitational head indicated at  14  while the draining of used dialysate from the patient  12  to the drain container  13  is caused by the drain head indicated at  15 . The cycler  10   a  includes no sensors for monitoring the pressure inside the peritoneum of the patient  12 . A single lumen  16  connects both the dialysate container  11  and drain container  13  to the patient  12 . Valves  17 ,  18  operated by the cycler  10   a  control the flow of either dialysate from the container  11  to the patient  12  or waste material from the patient  12  to the drain container  13 . 
     Turning to  FIG. 2 , in the cycler  10   b , the drain container  13  and dialysate container  11  are contained within a pressurized chamber  19 . The chamber  19  can be pressurized or evacuated to either fill or drain the patient. Again, the selective operation of valves  17 ,  18  control whether dialysate is being transferred to or from the patient  12 . Again, no sensors are provided for detecting or monitoring intraperitoneal pressure of the patient  12 . 
     Turning to  FIG. 3 , in the system  10   c , a dialysate container  11  is connected to a pump  21  which, in turn, connects the dialysate container  11  to a common lumen or catheter  16  which is connected to the patient. A fluid flow control valve is provided at  23  and is controlled by the cycler  10   c . The drain container  13  is also connected to a pump  24  which, in turn, connects the drain container  13  to the lumen  16 . A control valve is again provided at  25 . 
     The drain and fill rates of the cyclers  10   a - 10   c  illustrated in  FIGS. 1-3  are determined by the gravitational head (see  FIG. 1 ) or the suction or pressure (see  FIGS. 2 and 3 ) applied to the patient line  16 . Typically, the cyclers  10   a - 10   c  fail to optimize either the fill rate or the drain rate because the pressure is either fixed by the gravitational head or the pressure or suction applied by the chamber  10   b  of  FIG. 2  which occurs at the opposing end of the patient line  16 . Thus, without measuring the intraperitoneal pressure or having a way to estimate the same, it is difficult to optimize either the drain or fill rate. In the case of the cycler  10   c  in  FIG. 3 , optimizing the drain or fill rate is guesswork due to the lack of any pressure reading at all. 
     Accordingly, there is a need for an improved cycler that measures patient intraperitoneal pressure during a therapy session, including both during the drain and the fill as well as the dwell. Further, there is a need for an improved cycler that measures intraperitoneal pressure and which would use that data to more completely drain a patient between cycles. Further, there is a need for an improved cycler which would accurately measure intraperitoneal pressure to avoid overfilling a patient. Finally, there is a need for an improved cycler which would monitor intraperitoneal pressure during both the fill and drain cycles to optimize the speed at which the patient is filled and drained and to therefore increase the dwell portion of a therapy session. 
     SUMMARY 
     The present invention satisfies the aforenoted needs by providing a system for providing peritoneal dialysis to a patient which comprises a dialysate container connected to the patient with a first pressure sensor connected in-line herebetween, and a drain container connected to the patient with a second pressure sensor connected in-line therebetween. 
     In an embodiment, the system further comprises a first pump disposed in-line between the dialysate container and the first pressure sensor. 
     In an embodiment, the dialysate flows from the dialysate container into the patient under a hydrostatic head. 
     In an embodiment, a second pump is disposed in-line between the drain container and the second pressure sensor. 
     In an embodiment, the dialysate flows from the patient to the drain container under a hydrostatic head. 
     In an embodiment, the second pressure sensor measures an intraperitoneal pressure of the patient while dialysate flows from the dialysate container to the patient. 
     In an embodiment, the first pressure sensor measures an intraperitoneal pressure of the patient while dialysate flows from the patient to the drain container. 
     In an embodiment, the system further comprises a first lumen connecting the dialysate container to the first sensor and the first sensor to a catheter, and a second lumen connecting the drain container to the second sensor and the second sensor to the catheter, the catheter being connected to the patient, a flow of dialysate from the patient to the drain container evacuating dialysate from the first lumen and causing said dialysate from the first lumen to flow through the second lumen and to the drain container. 
     In an embodiment, the catheter is a dual lumen catheter. 
     In an embodiment, the first and second sensors are redundant in-line pressure/vacuum sensors. 
     In an embodiment, the present invention provides a method for dialyzing a patient comprising the steps of: placing a catheter in a peritoneum of the patient; providing at least one dialysate container; connecting the dialysate container to the catheter with a first lumen that includes a first pressure sensor disposed in-line and between the catheter and the dialysate container; providing at least one drain container; connecting the drain container to the catheter with a second lumen that includes a second pressure sensor disposed in-line and between the catheter and the drain container; transferring dialysate from the dialysate container to the peritoneum of the patient and monitoring an intraperitoneal pressure of the patient with the second pressure sensor; and transferring dialysate from the peritoneum of the patient to the drain container and monitoring the intraperitoneal pressure of the patient with the first pressure sensor. 
     In an embodiment, the step of transferring dialysate from the dialysate container to the peritoneum of the patient further comprises pumping dialysate from the dialysate container to the patient with a first pump disposed in-line between the dialysate container and the first pressure sensor. 
     In an embodiment, the step of transferring dialysate from the peritoneum of the patient to the drain container further comprises pumping dialysate from the peritoneum of the patient to the drain container with a second pump disposed in-line between the drain container and the second pressure sensor. 
     In an embodiment, the dialysate container is disposed vertically above the peritoneum of the patient and the step of transferring dialysate from the dialysate container to the peritoneum of the patient further comprises flowing dialysate from the dialysate container to the patient under a hydrostatic head. 
     In an embodiment, the drain container is disposed vertically below the peritoneum of the patient and the step of transferring dialysate from the peritoneum of the patient to the drain container further comprises flowing dialysate from the peritoneum of the patient to the drain container under a hydrostatic head. 
     Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  illustrates, schematically, a prior art automated peritoneal dialysis system; 
         FIG. 2  illustrates, schematically, a prior art automated peritoneal dialysis system; 
         FIG. 3  illustrates, schematically, a prior art automated peritoneal dialysis system; 
         FIG. 4  illustrates, schematically, an automated peritoneal dialysis system made in accordance with the present invention; 
         FIG. 5  illustrates, schematically, a second embodiment of an automated peritoneal dialysis system made in accordance with the present invention; 
         FIG. 6  illustrates, schematically, a third embodiment of an automated peritoneal dialysis system made in accordance with the present invention; 
         FIG. 7  illustrates, schematically, a fourth embodiment of an automated peritoneal dialysis system made in accordance with the present invention; 
         FIG. 8  illustrates a pressure sensor made in accordance with the present invention; 
         FIG. 9  illustrates a fifth embodiment incorporating dual pumping chambers and pressure sensors made in accordance with the present invention; 
         FIG. 10  illustrates, schematically, a dual lumen catheter that can be utilized with the present invention; 
         FIG. 11  is a sectional view taken substantially along line  11 - 11  of  FIG. 10 ;  FIG. 12  illustrates, graphically, the urea concentration in blood and the urea concentration in a dialysate during a multiple dwell dialysis session; 
         FIG. 13  illustrates, graphically, the concentration of urea in a patient&#39;s bloodstream versus the concentration of urea in a dialysate solution for an automated peritoneal dialysis solution practiced in accordance with the prior art; and 
         FIG. 14  illustrates, graphically, the concentration of urea in a patient&#39;s bloodstream versus the concentration of urea in a dialysate for an automated peritoneal dialysis therapy session carried out in accordance with the present invention. 
       It should be understood that the drawings are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein. 
     
    
    
     DETAILED DESCRIPTION 
     Turning to  FIG. 4 , a cycler  30  includes a dialysate container  11  connected to a pump  31 . The pump  31  is connected to a pressure sensor  32 . The pump  31  and pressure sensor  32  are disposed in-line in a lumen  33  that connects the dialysate container  11  to a catheter  34 . Control valves are provided at  35 ,  199 . A drain container  13  is also connected to a pump  36  which is connected to a sensor  37 . The pump  36  and sensor  37  are also connected in-line to a lumen  38  which connects the drain container  13  to the catheter  34 . Control valves are again provided at  41 ,  42 . During the fill, the pump  31  pumps dialystate from the container  11  through the lumen  33  and catheter  34  into the peritoneum (not shown) of the patient  12 . During this time, the sensor  37  monitors and measures the intraperitoneal pressure. A signal is sent to the controller of the cycler  30  shown schematically at  43 . A control panel is indicated generally at  44 . 
     During the drain, the sensor  32  can accurately monitor and measure the intraperitoneal pressure of the patient  12 . In the embodiment illustrated in  FIG. 4 , no pumps or control valves are disposed between the sensor  32  and the patient  12 . 
     Turning to  FIG. 5 , a cycler  50  is illustrated which includes reversible pumping chambers  51 ,  52  with sensors  53 ,  54  disposed between the reversible pumping chambers  51 ,  52  and the patient  12  respectively. Control valves  55  and  56  are disposed on another side of the reversible pumping chamber  51  and the sensor  53  and control valves  57 ,  58  are provided on either side of the reversible pumping chamber  52  and sensor  54 . The sensors  53 ,  54  actually measure the pressure on the diaphragms of the reversible pumping chambers  51 ,  52 . 
     Turning to  FIG. 6 , a cycler  60  is illustrated with a chamber  61  for accommodating the drain container  13  and a chamber  62  for accommodating the dialysate container  11 . Each chamber  61 ,  62  is equipped with an integrated valve assembly and pressure sensor shown at  63 ,  64 . In the embodiment  60  shown in  FIG. 6 , the chamber  61  must be capable of being evacuated. Dialysate may flow from the dialysate container  11  by way of gravity or pressure fill. Again, the sensors of the valve assembly/sensor combinations  63 ,  64  monitor the intraperitoneal pressure of the patient  12  as discussed above. 
     In the embodiment  70  illustrated in  FIG. 7 , the dialysate container  11  and drain container  13  are both connected to integrated control valves and pressure sensors  71 ,  72 . Each of the integrated control valves and pressure sensors  71 ,  72  are connected to lumens  73 ,  74  respectively which are connected to the catheter  75   a  by way of a Y-connection. The details of all the Y-connections and clamps are not shown but are known to those skilled in the art. Flow from the dialysate container  11  to the patient is carried out under the gravitational head shown at  75  while flow from the patient to the drain container  13  is carried out under the gravitational head shown at  76 . 
       FIG. 8  illustrates one in-line pressure sensor  80  that is suitable for use with the present invention. Redundant load cells  81 ,  82  are connected to the flexible pressure sensing membrane  83  by a vacuum connected by the line  84 ,  85 . A lumen connecting the cycler to the patient is shown at  86 . 
       FIG. 9  illustrates a dual-pumping chamber cassette  87  which includes an output line  88  which connects the cassette  87  to the patient and an input line  89  connecting the patient to the cassette  87 . The line  90  connects the cassette  87  to the dialysate container (not shown). Each pumping chamber  91 ,  92  are in communication with all three lines  88 ,  89  and  90 . Thus, every line can be connected to either pumping chamber  91 ,  92 . The pumping chambers  91 ,  92  are bound on one side by a common diaphragm shown at  93 . Flow is controlled by the use of diaphragm valves shown at  94 ,  95 ,  96  and  97 . Pressure sensors are shown at  120 ,  121 ,  122 ,  123 ,  124 ,  125 . However, pressure sensors  123  and  120  are the sensors used to measure intraperitoneal pressure in accordance with the present invention. The remaining sensors  121 ,  122 ,  124 ,  125  are used to monitor the operation of the pumps  126 ,  127 . 
     When the left diaphragm pump  126  is pushing dialysate to the patient, the sensor  123  can measure the intraperitoneal pressure through the line  89 . When the left diaphragm pump  126  is draining fluid from the patient through the line  89 , the sensor  120  can measure intraperitoneal pressure through the line  88  and while the right pump  127  is pumping fluid to the drain container (not shown) through the drain line shown schematically at  128 . When the right diaphragm pump  127  is being used to drain fluid from the patient, the sensor  120  can measure intraperitoneal pressure while the left diaphragm pump  126  is pumping fluid to the drain container (not shown) through the drain line shown schematically at  129 . 
       FIGS. 10 and 11  illustrate a dual-lumen catheter  100  which includes separate passageways  101 ,  102 . The employment of a dual lumen catheter  100  as compared to a dual lumen patient line can move the point at which the pressure is measured to within the peritoneum itself by way of communication through the separate flowpaths  101 ,  102 . The dual lumen catheter  100  installs like a single lumen catheter, yet will function either as a flow through or a standard catheter. Both fluid pathways  101 ,  102  are used to withdraw and deliver fluid during the drain and fill. While one pathway delivers fluid, the other pathway drains. The end section, shown generally at  103 , is perforated. 
     A comparison of an APD therapy for a prior art APD cyclers and one manufactured in accordance with the present invention are summarized as follows: 
     
       
         
               
               
               
             
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
               
               
               
             
               
               
               
               
               
             
               
               
               
             
           
               
                   
               
               
                 Therapy Parameter 
                 Current APD Cycler 
                 Cycler Using Invention 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Total Therapy Volume 
                 15 
                 liters 
                 15 
                 liters 
               
               
                 Fill Volume 
                 2.2 
                 liters 
                 2.5 
                 liters max 
               
             
          
           
               
                 Fill Pressure Limit 
                 not applicable 
                 14 
                 mm Hg max 
               
             
          
           
               
                 Total Therapy Time 
                 8 
                 hours 
                 8 
                 hours 
               
               
                 Last (Day) Fill Volume 
                 1,500 
                 ml 
                 1,500 
                 ml 
               
             
          
           
               
                 Last Fill Dextrose 
                 Same 
                 Same 
               
             
          
           
               
                 Initial Drain Alarm 
                 1,200 
                 ml 
                 1,200 
                 ml 
               
             
          
           
               
                 Drain X of N Alarm 
                 80% 
                 80% 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Comparison of Therapies for Current Cyders versus Cycler using Invention Method 
               
             
          
           
               
                 Therapy Phase 
                 Therapy Parameter 
                 Prior Art Cycler 1 
                 Prior Art Cycler 2 
                 Invention Cycler 3 
               
               
                   
               
             
          
           
               
                 Initial Drain 
                 Drain Volume 
                 1,200 
                 ml 
                 1,200 
                 ml 
                 1,200 
                 ml 
               
               
                   
                 Patient Volume 
                 300 
                 ml 
                 300 
                 ml 
                 300 
                 ml 
               
               
                 Fill I of 5 
                 Fill Volume 
                 2,200 
                 ml 
                 2,200 
                 ml 
                 2,500 
                 ml 
               
               
                   
                 Patient Volume 
                 2,500 
                   
                 2,500 
                   
                 2,800 
               
             
          
           
               
                   
                 Fill Pressure 
                 not applicable 
                 not applicable 
                 12 
                 mm Hg 
               
             
          
           
               
                 Drain 1 of 5 
                 Drain Volume 
                 1,800 
                 ml 
                 2,200 
                 ml 
                 2,200 
                 ml 
               
               
                   
                 Patient Volume 
                 700 
                 ml 
                 300 
                 ml 
                 600 
                 ml 
               
               
                 Fill 2 of 5 
                 Fill Volume 
                 2,200 
                 ml 
                 2,200 
                 ml 
                 2,400 
                 ml 
               
               
                   
                 Patient Volume 
                 2,900 
                 ml 
                 2,500 
                 ml 
                 3,000 
                 ml 
               
             
          
           
               
                   
                 Patient Pressure 
                 not applicable 
                 not applicable 
                 14 
                 mm Hg 
               
             
          
           
               
                 Drain 2 of 5 
                 Drain Volume 
                 1,800 
                 ml 
                 2,200 
                 ml 
                 2,200 
                 ml 
               
               
                   
                 Patient Volume 
                 1,100 
                 ml 
                 300 
                 ml 
                 800 
                 ml 
               
               
                 Fill 3 of 5 
                 Fill Volume 
                 2,200 
                 ml 
                 2,200 
                 ml 
                 2,200 
                 ml 
               
               
                   
                 Patient Volume 
                 3,300 
                 ml 
                 2,500 
                 ml 
                 3,000 
                 ml 
               
             
          
           
               
                   
                 Patient Pressure 
                 not applicable 
                 not applicable 
                 14 
                 mm Hg 
               
             
          
           
               
                 Drain 3 of 5 
                 Drain Volume 
                 1,801 
                 ml 
                 2,200 
                 ml 
                 2,200 
                 ml 
               
               
                   
                 Patient Volume 
                 1,499 
                 ml 
                 300 
                 ml 
                 800 
                 ml 
               
               
                 Fill 4 of 5 
                 Fill Volume 
                 2,200 
                 ml 
                 2,200 
                 ml 
                 2,200 
                 ml 
               
               
                   
                 Patient Volume 
                 3,699 
                 ml 
                 2,500 
                   
                 3.000 
                 ml 
               
             
          
           
               
                   
                 Patient Pressure 
                 not applicable 
                 not applicable 
                 3,000 
                 ml 
               
             
          
           
               
                 Drain 4 of 5 
                 I Drain Volume 
                 1,800 
                 ml 
                 2,200 
                 ml 
                 2,200 
                 ml 
               
               
                   
                 Patient Volume 
                 1,899 
                 ml 
                 300 
                 ml 
                 800 
                 ml 
               
             
          
           
               
                 Fill 5 of 5 
                 Fill Volume 
                 uF Alarm Bypass 
                   
                   
                   
                   
               
             
          
           
               
                   
                   
                 2,200 
                 ml 
                 2,200 
                 ml 
                 2,200 
                 ml 
               
               
                 Patient Volume 
                 4,099 ml 
                 2,500 
                 ml 
                 3,00 
                 ml 
               
             
          
           
               
                   
                 Patient Pressure 
                 Patient Wakes 
                 not 
                 14 
                 mm Hg 
               
               
                   
                   
                 Overfull, 
                 applicable 
               
               
                   
                   
                 Manually Drains 
               
               
                   
                   
                 1,500 ml 
               
             
          
           
               
                 Drain 5 of 5 
                 Drain Volume 
                 1,800 
                 ml 
                 2,200 
                 ml 
                 2,200 
                 ml 
               
               
                   
                 Patient Volume 
                 799 
                 ml 
                 300 
                 ml 
                 800 
                 ml 
               
               
                 Final Fill 
                 Fill Volume 
                 1,500 
                 ml 
                 1,500 
                 ml 
                 1,500 
                 ml 
               
               
                   
               
             
          
         
       
     
     Inspection of Table 1 shows that cycler  1  woke the patient at around 4:30 in the morning with a negative uF alarm at the beginning of Fill  5 . The patient bypassed the alarm because he did not feel overfull and immediately fell back asleep. He woke up about minutes later when he had difficulty breathing and felt extremely overfull. He manually drained about 1500 ml but was unable to go back to sleep. He filed a formal product complaint with the manufacturer. 
     The data of Table I shows that cycler  2  ran a completely normal therapy but the total therapy clearance (calculated based upon the sum of the night patient volumes) was only 84.5% of that obtained by cycler  3 , which was using the cycler that used the method of the current invention. 
     The data of Table 1 shows that cycler  3  ran a completely normal therapy and that the fill volume was limited on one occasion by the maximum fill volume but on four occasions by the patient&#39;s intraperitoneal pressure. This patient never felt any discomfort and had no alarms during the night. The limit on the IPP prevented him from being overfilled even though he had successive drains that were not complete. The volume of fluid in his peritoneum never exceeded 3 liters. 
     The patient on cycler  1  had an intraperitoneal pressure in excess of 14 mm Hg during dwells  3  and  4 . His breathing may have been impaired and his heart may have had to work harder but the discomfort was not enough to wake him up from a sound sleep until it peaked at 4,099 ml during dwell  5 . 
     In conclusion, the method of the present invention provides for optimum fills and therefore more clearance while preventing overfills that bring discomfort and inhibit the function of vital body organs. A negative uF alarm would seldom occur because overfills of the required magnitude would be prevented by the IPP sensors. 
     CALCULATION OF INTRAPERITONEAL PRESSURE (IPP) 
     In order to calculate the IPP, one may first calculate the patient head height correction using conservation of energy:
 
Δ(½ ρV   2   +P−pa   g   h )+Frictional Losses=0
 
     The velocity V of fluid through the patient line is the same at both ends of the line as is the fluid density, so this equation can be written as
 
( P   2   −P   1 ) −pa   g ( h   2   h ,)+Frictional Losses=0
 
     which can be rearranged as 
     
       
         
           
             
               Δ 
               ⁢ 
               
                   
               
               ⁢ 
               h 
             
             = 
             
               
                 
                   ( 
                   
                     
                       P 
                       1 
                     
                     - 
                     
                       P 
                       2 
                     
                   
                   ) 
                 
                 - 
                 
                   Frictional 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   Losses 
                 
               
               
                 ρ 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   a 
                   g 
                 
               
             
           
         
       
     
     EXAMPLE 1 
     P1=1.25 psig=85060 (gram/cm)/(cm 2 -sec 2 ) 
     P2=0.9 psig=61240 (gram/cm)/(cm 2 -sec 2 ) 
     Frictional Losses=39130 (gram/cm)/(cm 2 -sec 2 ) with flow of 197 cm/min in a 4 mm ID line at a velocity of approximately 172 cm/sec, wherein 
     a g =981 cm/sec 2    
     ρ=1 gram/cm 3    
     
       
         
           
             
               Δ 
               ⁢ 
               
                   
               
               ⁢ 
               h 
             
             = 
             
               
                 
                   ( 
                   
                     
                       ( 
                       
                         85060 
                         - 
                         61240 
                       
                       ) 
                     
                     - 
                     39130 
                   
                   ) 
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   
                     ( 
                     
                       gram 
                       / 
                       cm 
                     
                     ) 
                   
                   / 
                   
                     ( 
                     
                       
                         cm 
                         2 
                       
                       - 
                       
                         sec 
                         2 
                       
                     
                     ) 
                   
                 
               
               
                 1 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   gram 
                   / 
                   cm 
                 
                 * 
                 981 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   cm 
                   / 
                   
                     sec 
                     2 
                   
                 
               
             
           
         
       
     
     Δh=−15.6 cm (The patient is 15.6 cm below the membrane) 
     EXAMPLE 2 
     PI=1.25 psig=85060 (gram/cm)/(cm 2 -sec 2 ) P2=0.45 psig=30620 (gram/cm)/(cm 2 -sec 2 ) 
     Frictional Losses=39130 (gram/cm)/(cm 2 -sec 2 ) with flow of 197 cmn/min in a 4 mm ID line at a velocity of approximately 172 cm/sec, wherein 
     a g =981 cm/sec 2    
     ρ=1 gram/cm 3    
     
       
         
           
             
               Δ 
               ⁢ 
               
                   
               
               ⁢ 
               h 
             
             = 
             
               
                 
                   ( 
                   
                     
                       ( 
                       
                         85060 
                         - 
                         30620 
                       
                       ) 
                     
                     - 
                     39130 
                   
                   ) 
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   
                     ( 
                     
                       gram 
                       / 
                       cm 
                     
                     ) 
                   
                   / 
                   
                     ( 
                     
                       
                         cm 
                         2 
                       
                       - 
                       
                         sec 
                         2 
                       
                     
                     ) 
                   
                 
               
               
                 1 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   gram 
                   / 
                   
                     cm 
                     3 
                   
                 
                 * 
                 981 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   cm 
                   / 
                   
                     sec 
                     2 
                   
                 
               
             
           
         
       
     
     Δh=+15.6 cm (The patient is 15.6 cm above the membrane) 
     The patient head height can be established at the beginning of each fill. Any changes in the head height that occur during the fill can be attributed to an increase in intraperitoneal pressure (IPP) since the patient is asleep. 
     Turning to  FIG. 12 , the concentration gradient between the urea concentration  110  in the patient&#39;s blood and the urea concentration  111  in the dialysate for typical APD cyclers is illustrated graphically. Comparing the results illustrated in  FIGS. 13 and 14 , it is evident that APD cyclers equipped with the sensors of the present invention provide superior results. Specifically, the data illustrated graphically in  FIG. 13  was obtained using a prior art APD cycler. The data obtained in  FIG. 14  was obtained using an APD cycler utilizing two sensors for monitoring intraperitoneal pressure. Note that the urea concentration  110  in the bloodstream is lower in  FIG. 14  than in  FIG. 13 . Further note, the dialysate volume or fill volume is lower for the therapy illustrated in  FIG. 14  than the therapy illustrated in  FIG. 13 . Thus, the present invention provides improved urea clearance with lower fill volumes. 
     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 attendant advantages. It is, therefore, intended that such changes and modifications be covered by the appended claims.

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