Patent Description:
Automated Peritoneal Dialysis ("APD") is a natural evolution of Continuous Ambulatory Peritoneal Dialysis ("CAPD"), in which the patient introduces the entire contents of a dialysate solution bag into his/her peritoneum and allows the volume to dwell for three to six hours. After the dwell period, the fluid is drained using gravity. The above process is typically repeated three or four times each day as necessary. Working adults may perform an exchange at home before leaving for work, one at work during their lunch hour, one when the patient arrives home from work and one just before the patient goes to bed. Some school-aged patients follow a similar routine except they perform their mid-day exchange at school.

APD machines (sometimes called "cyclers") perform sequential exchanges during the night when the patient is sleeping, making APD a more convenient therapy. Also, the treatment is carried out in the privacy of the patient's home, so that others do not have to know that the patient is on dialysis. It is no surprise that most patients would prefer APD over CAPD.

However, there are some important differences between CAPD and APD. CAPD is typically performed with the patient sitting upright in a chair, whereas APD is performed with the patient lying down. The patient's internal catheter may work its way down into the bottom of the patient's peritoneal cavity (pelvic area) during the day when the patient is up and about so that it is not in an optimum position for draining when the patient is in a prone or sleeping position. Even with the catheter in the correct position, a supine or sitting position is generally better for draining than is the prone or sleeping position. Thus APD treatments can experience incomplete drains.

Continuous Cycling Peritoneal Dialysis ("CCPD") is one popular APD therapy because it performs a full drain after every dwell, minimizing the potential for overfill due to the fluid that is ultrafiltered from the patient's body. CCPD can however present a challenge when a patient does not drain well. In a night therapy, the patient cannot be awakened every <NUM> hours, so that the patient can sit up and ensure a complete drain.

Accordingly, APD cyclers in some instances advance from drain to fill after a minimum percentage of the patient's previous fill volume has been drained, for example, when the drain flow rate has slowed down to a point that time is being wasted that could be used for therapeutic benefit. Alarms will typically be posted if the drain flow rate slows to a certain rate before the minimum drain percentage has been exceeded. The HomeChoice/Pro® APD cycler, provided by the assignee of the present disclosure, is considered one of the best draining cyclers on the market, producing fewer alarms when compared to its competitors. Even still, low drain volume alarms occur relatively frequently.

<CIT> discloses a peritoneal dialysis device with a graphical interface for displaying a plurality of parameters and any values currently assigned to the parameters. A user can select a displayed parameter and is then able to input a value to be assigned to that parameter. A value is set for a number of fills parameter or a dwell time parameter based on the value received from the user.

An APD cycler with improved drain control is needed accordingly.

The present invention provides a system for performing a peritoneal dialysis therapy according to claim <NUM>.

As discussed above, automated Peritoneal Dialysis ("APD") cyclers perform sequential exchanges during the night making APD a convenient dialysis therapy. An alternative PD therapy, continuous ambulatory peritoneal dialysis ("CAPD") is performed during the day, making CAPD more life intrusive. During CAPD, however, the patient is awake and can move around and sit up during drains, allowing drains to be performed completely.

At night, when the patient is performing APD, the patient is lying down. The patient's internal catheter may have shifted during the day, making the patient susceptible to an incomplete drain. The APD system of the present disclosure is programmed to advance to a fill if a drain flow rate slows to a certain point and a minimum drain volume has been achieved. If the drain has not reached this minimum volume, which is often based upon a certain percentage of the programmed fill, the system will alarm. When an alarm occurs, the patient is awakened, which is not desirable. The system of the present disclosure greatly reduces the number of low drain alarms.

Another therapy concern enhancing the low drain problem is a limit placed on how full the patient can be filled. Multiple incomplete drains leave an ever increasing residual volume of fluid in the patient. If the residual volume increases to a certain point, the next fill may push the patient's intra-peritoneal volume ("IPV") past an allowable limit. The subsequent fill may therefore be shorted to prevent overfilling, but this may cause the treatment not to use all of the fluid for treatment.

To remedy the above, in one embodiment, the system begins a CCPD treatment that attempts to drain the patient completely after each drain. When performed properly, the CCPD therapy is quite effective. The patient's initial drain (at night, just before bed) and final drain (in the morning, after waking) should be relatively if not totally complete because the patient can sit-up and move around to help move the patient's catheter into areas of his/her peritoneum that are pocketing fluid.

It is the intermediate drains that may be difficult to complete especially considering that the therapy needs to move along and cannot wait while a low drain flow rate occurs while attempting to drain the patient completely. When the low flow rate is sensed, the system determines that it is time to move to the next fill. If the previous drain was almost complete, e.g., <NUM>% of prescribed, the system in one embodiment continues to provide the prescribed CCPD therapy. If all subsequent drains are complete, the final drain can remove the additional, e.g., <NUM>%, fluid from the delinquent drain.

If multiple "almost complete" drains occur, the patient can begin to build a substantial residual volume due to the cumulative effects of the incomplete drains. If the system determines that a next fill will increase the patient's intra-peritoneal volume ("IPV") past an allowable volume, e.g., <NUM> times the prescribed fill volume, the system switches to a tidal therapy that reduces the prescribed drain to a tidal volume, increasing the likelihood of the system having a subsequent successful drain. The tidal therapy also reduces succeeding fills, such that the patient's IPV does not exceed the allowable limit.

The now tidal therapy may add one or more cycle if needed to use all of the prescribed fresh solution. A logic flow diagram is shown below with various equations for determining when the one or more additional cycle is needed. Whether or not a cycle is added, the system divides the remaining unused therapy fluid and the remaining therapy time evenly over the number of remaining cycles.

The switch to tidal therapy attempts to reduce low drain alarms that occur if the actual drain does not meet a threshold percentage, e.g., <NUM>%, of the prescribed drain. The tidal therapy allows for a larger residual volume to reside within the patient at the end of a drain, increasing the likelihood that a flow rate at the end of the drain will be high and that the drain will not be ended early due to a low drain flow rate. The tidal therapy uses all of the remaining fresh dialysate, so that the patient is not deprived of any therapeutic benefit. The tidal therapy is also completed on time and ensures that the patient is not overfilled with dialysis fluid at any time.

In one embodiment, a dialysis system is provided, the dialysis system including at least one dialysis fluid pump configured to pump a dialysis fluid to and from a patient over a treatment, the dialysis system also including a logic implementer configured to control the dialysis fluid pumped by the at least one dialysis fluid pump to and from a patient over the treatment, the logic implementer configured to use at least one trended ultrafiltration ("UF") data point for the patient to determine an amount of effluent dialysis fluid to remove from the patient during at least one patient drain.

In another embodiment, the dialysis system includes at least one dialysis fluid pump to pump a dialysis fluid to and from a patient over a treatment, the dialysis system also including a logic implementer configured to control the dialysis fluid pumped by the at least one dialysis fluid pump to and from a patient over the treatment, the logic implementer configured to (i) store a trend of ultrafiltration data points for the patient, and (ii) use at least one of the UF data points to predict the patient's intra-peritoneal volume ("IPV") at an end of at least one dwell.

In yet another embodiment, a dialysis system includes at least one dialysis fluid pump configured to pump a dialysis fluid to and from a patient over a treatment, the system also including a logic implementer configured to control the dialysis fluid pumped by the at least one dialysis fluid pump to and from a patient over the treatment, the logic implementer configured to (i) store a trend of ultrafiltration data points for the patient, and (ii) use one of the UF data points in a tidal treatment to predict a residual volume of effluent fluid left in the patient's peritoneum after at least one drain.

In one embodiment, a tidal therapy is provided in which a predicted amount of patient UF for each cycle is obtained from a trend of a UF values for the patient, for the tidal therapy, and for a particular dialysate, having a particular osmotic agent or dextrose level. In this manner, UF can be predicted very accurately.

Knowing predicted UF accurately allows the system to predict the patient's intraperitoneal volume or IPV very accurately. For example, assuming that the patient's initial drain is a successful complete drain (patient awake), the patient is then filled to a known level. The subsequent dwell will remove an amount of UF from the patient that should closely approximate the predicted removal of UF. Thus the actual IPV at the end of the dwell should closely approach the actual fill amount (which is known) plus a predicted UF removed (which is based on trended UF).

The UF trend is stored and updated in one embodiment at the cycler or automated peritoneal dialysis ("APD") machine. The patient can recall the trend at any time to view same including historical trending data. The APD machine can be linked via a data network, such as an internet, so that a dialysis clinician or doctor can also view the patient's UF trend remotely. In an alternative embodiment, the UF trend is stored and updated on a remote server, which the patient can access via the data network.

The UF trend in one embodiment plots patient single day UF data. If the patient removes <NUM> of UF on day X, <NUM> is recorded for day X. And the daily UF in one embodiment is the UF removed over the nightly treatment, that is, the UF removed after the initial drain (from previous days last fill or from day exchange) and prior to the last fill, if provided. Here, the daily UF is that removed over the course of multiple tidal dwells. This total UF can be measured accurately because the patient is drained completely on the initial drain. The measured UF, which is entered into the trend is then the total amount of drained fluid, not including the initial drain, but including the last drain, which is typically a complete drain with the patient awake, less the total amount of fresh dialysis fluid pumped to the patient, but not including the final fill. The APD machine can measure each of these values accurately to provide a true UF data point.

In an alternative embodiment, the trended UF data is averaged UF data for a particular therapy using a particular dialysate glucose level. The average can for example be a rolling seven or thirty day average that averages the last seven or thirty day's UF entries, respectively, for each dialysate glucose solution used by the patient, to form a rolling average UF volume for such glucose level solution. Such averaging tends to smooth UF anomalies for treatments that may have undergone unusual events, such as alarms or other stoppage.

In view of the above embodiments, it is accordingly an advantage of the present disclosure to provide improved Continuous Cycling Peritoneal Dialysis ("CCPD") and tidal automated peritoneal dialysis ("APD") therapies.

Another advantage of the system of the present disclosure is to provide an APD therapy that tends to limit low drain alarms.

A further advantage of the system of the present disclosure is to provide an APD therapy that tends to limit patient overfilling.

Yet another advantage of the system of the present disclosure is to provide an APD therapy that tends use all available fresh dialysis fluid over the course of treatment.

A further advantage of the system of the present disclosure is to provide an APD therapy that adjusts to an incomplete drain to prevent a patient overfill.

Still another advantage of the system of the present disclosure is to provide an APD therapy that reacts to an incomplete drain to ensure that all available treatment fluid is used over the course of treatment.

Still a further advantage of the system of the present disclosure is to provide an APD therapy that employs ultrafiltration ("UF") trending to provide trending data that allows for accurate prediction of UF and overall intra-peritoneal volume ("IPV").

Additional features and advantages are described herein, and will be apparent from the following Detailed Description and the figures.

Referring now to the drawings and in particular to <FIG>, a renal failure therapy system <NUM> is provided. System <NUM> is applicable generally to any type of automated peritoneal dialysis ("APD") system. System <NUM> in the illustrated embodiment includes a dialysis instrument <NUM>. Dialysis instrument <NUM> is configured for the type of APD therapy system provided. Dialysis instrument <NUM> includes a central processing unit ("CPU") and memory, and may include one or more additional processor and memory (e.g., safety, valve, heater, pump, video and audio (e.g., voice guidance) controllers) operable with the CPU, the totality of which may be called a logic implementer. The logic implementer operates with a user interface ("UI") such as a graphical user-machine interface ("GUI"), e.g., via a video controller component of the logic implementer. The GUI includes a video monitor <NUM> and one or more types of input devices <NUM>, such as a touch screen or electromechanical input device (e.g., a membrane switch).

The logic implementer in cooperation with video monitor <NUM> provides therapy instructions and setup confirmation to the patient or caregiver visually via characters/graphics. For example, characters/graphics can be displayed to (i) provide instructions regarding placement of a distal end of the patient line onto instrument <NUM> (discussed below) for priming and/or (ii) inform the patient when the patient line has been primed fully. Additionally or alternatively, a voice guidance controller of the logic implementer in cooperation with speakers <NUM> provides (i) and/or (ii) listed above.

As seen in <FIG>, dialysis instrument <NUM> accepts and operates with a disposable set <NUM>. Disposable set <NUM> includes one or more supply bag 32a to 32c (referred to herein collectively as supply bags <NUM> or individually, generally as supply bag <NUM>), shown here as dual-chamber supply bags separating two fluids via a peel or frangible seal <NUM>. Disposable set <NUM> also includes a drain bag (not illustrated), a warmer bag <NUM>, and patient tubes 38a to 38d, respectively (referred to herein collectively as tubing or tubes <NUM> or individually, generally as tube <NUM>) and a disposable pumping/valve cassette <NUM> (<FIG>).

Warmer bag <NUM> is used in a batch heating operation in which the top of instrument <NUM> batch heats fluid within bag <NUM>. System <NUM> can also pump spent fluid to a house drain, such as a bathtub, a toilet or sink, instead of to a drain bag, in which case the drain bag is not needed.

While three supply bags <NUM> are shown, system <NUM> can employ any suitable number of supply bags. Supply bags <NUM> are shown having multiple chambers 42a and 42b, separated by frangible seal <NUM>, which hold different solutions depending on the type of therapy employed. For example, chambers 42a and 42b can hold buffer and glucose for an overall PD dialysate having a desired glucose level. Supply bags <NUM> are alternatively single chamber bags, which hold a single premixed solution, such as premixed PD dialysate having a desired glucose level.

As seen in <FIG> and <FIG>, a disposable cassette <NUM> connects to supply bags <NUM>, drain bag and warmer bag <NUM> via tubes 38a, 38b and 38c, respectively. Tube 38d runs from cassette <NUM> to a patient connection <NUM>. Cassette <NUM> in one embodiment includes a rigid structure having rigid outer walls <NUM> and a middle, base wall (not shown) from which pump chambers (60a and 60b as shown in <FIG>), valve chambers (e.g., volcano valve chambers) and rigid fluid pathways extend. Rigid fluid ports <NUM> extend from a side wall <NUM> and communicate fluidly with the rigid cassette pathways and connect sealingly to tubing <NUM>. Tubing <NUM> can be fixed to ports <NUM>, in which case the bags <NUM> are spiked to allow fluid from the bags to flow through tubing <NUM> into cassette <NUM>. Alternatively, tubing <NUM> is fixed to bags <NUM>, in which case ports <NUM> are spiked to allow fluid from the bags <NUM> and tubing <NUM> into cassette <NUM>.

A pair of flexible membranes or sheets <NUM> (only one shown) is sealed to outer rigid walls <NUM> of the cassette. Cassette <NUM> is sealed within instrument <NUM> such that sheeting <NUM> forms the outer surfaces of the rigid fluid pathways of the cassette. One of the sheets is moved to pump fluid through pump chambers (60a and 60b) and to open and close the cassette valves.

Instrument <NUM> can actuate the pump and valve chambers of cassette <NUM> pneumatically, mechanically or both. The illustrated embodiment uses pneumatic actuation. The HomeChoice® APD system uses a pneumatic system described in <CIT> ("the '<NUM> Patent"). As seen in <FIG>, instrument <NUM> includes a flexible membrane <NUM>, which creates different sealed areas with cassette sheeting <NUM> at each of the pump and valve chambers of cassette <NUM>. Membrane <NUM> moves with the sheeting <NUM> in those areas to either open/close a valve chamber or pump fluid through (into and out of) a pump chamber. An interface plate (not shown) is located behind membrane <NUM> and includes first and second chamber halves (not shown) that mate with chamber halves 60a and 60b of cassette <NUM> to form a pair of fixed volume pump chambers.

Instrument <NUM> in the illustrated embodiment includes a door <NUM>, which closes against cassette <NUM>. Door <NUM> includes a press plate <NUM>, which can be operated mechanically (e.g., via the closing of the door) and/or pneumatically (e.g., via an inflatable bladder located in the door behind the press plate). Pressing plate <NUM> against cassette <NUM> in turn presses cassette <NUM> against pumping membrane <NUM>, which cooperates with sheeting <NUM> of cassette <NUM> to pump fluid through chambers 60a and 60b and to open and close the cassette valve chambers.

The cassette interface plate is located behind membrane <NUM>. Cassette interface plate is configured to apply positive or negative pressure to the cooperating membrane <NUM> and cassette sheeting <NUM> at the different valve and pump areas. For example, positive pressure is applied to membrane <NUM>/sheeting <NUM> at areas of the membrane/sheeting located within the internal walls of cassette <NUM> that define pump chambers 60a and 60b to push fluid out of the pump chambers and within the chamber halves of the interface plate (not shown). Negative pressure is applied to membrane <NUM>/sheeting <NUM> at those same areas to pull fluid into the pump chambers. Likewise, positive pressure is applied to membrane <NUM>/sheeting <NUM> at areas of the sheeting within the internal walls of cassette <NUM> and the interface plate defining the valve chambers to close outlet ports of the valve chambers. Negative pressure is applied to membrane <NUM>/sheeting <NUM> at those same areas to open the outlets of the valve chambers.

<CIT> ("the '<NUM> patent") assigned to the assignee of the present disclosure, discloses a pumping mechanism in connection with Figs. 17A and 17B and associated written description, which uses a combination of pneumatic and mechanical actuation. <FIG>, 16A and 16B of the '<NUM> Patent and associated written description, teach the use of mechanically actuated valves. One or both of these mechanisms can be used instead of the purely pneumatic system of the HomeChoice® machine.

The '<NUM> Patent and the '<NUM> patent also teach different systems and methods, of knowing and controlling the amount of fresh dialysate delivered to the patient, the amount of effluent dialysate removed from the patient, and thus the amount of additional fluid or ultrafiltrate ("UF") removed from the patient. UF is the blood water that the patient accumulates between treatments due to the patient's failed kidneys. The dialysis treatment removes this blood water as UF in an attempt to bring the patient back to his or her dry weight. Either of the systems and method of the '<NUM> Patent and the '<NUM> patent can be used as described below for controlling the fill and drain volumes according to the methods of system <NUM>.

Referring now to <FIG>, one example plot of the intra-peritoneal patient volume ("IPV") versus time over an ideal CCPD for system <NUM> is illustrated. Here, each drain empties completely the fluid from the patient's peritoneum, including the previous fill volume plus any UF that has occurred during the previous dwell period. As seen in <FIG>, therapy starts with an initial drain to empty, followed by a number of identical cycles consisting of a fill to a prescribed volume, a dwell of a prescribed duration, and a drain that removes the original fill volume plus all of the UF that has been absorbed from the patient. <FIG> illustrates a five cycle therapy having a <NUM> fill volume and <NUM>/cycle UF volume. The initial drain recovers all of the fluid from the previous day's last fill that has remained in the patient's peritoneal cavity throughout the day.

Patients sometimes pocket fluid so that a drain that is supposed to be to empty does not remove all of the previous fill volume. System <NUM> in one embodiment sets a minimum drain percentage that must be obtained when the fluid flow slows or stops. If the minimum drain volume is not met, system <NUM> posts a low drain volume alarm. In such a case, the therapy does not advance to fill, that is, if the drain volume is not equal to or greater than the minimum drain percentage. In <FIG>, system <NUM> fills the patient to the prescribed fill volume in each fill because the minimum drain percentage for each drain has been met. One example minimum drain percentage for system <NUM> is about <NUM>% of the fill volume.

System <NUM> in one embodiment calculates the amount of UF obtained at the end of the drain phase of each cycle as follows:
<MAT>.

The initial drain and last fills are not included in the UF calculation. Calculated UF will be positive as long as more spent fluid drained than fresh dialysis fluid filled. A zero UF value means that the volume drained after any number of cycles is equal to the volume filled during those cycles. A drain that does not recover all of the fluid that was delivered to the patient during the previous fill results in a negative UF determination. Unless the patient is absorbing fluid, a negative UF implies that the patient's intra-peritoneal volume is in excess of a prescribed fill volume.

It is normal for the intra-peritoneal volume to exceed the prescribed fill volume. The intra-peritoneal volume during a CCPD dwell phase consists of the following volumes: intra-peritoneal volume ("IPV") = prescribed fill volume + residual volume at end of a previous drain + UF from dwell. It is also not unusual for the residual volume in the patient's peritoneum to equal <NUM> to <NUM>% of the prescribed fill volume at the end of a drain cycle.

The UF that has accumulated during a dwell will depend upon the osmotic gradient (a function of the dextrose level of the dialysate), the time in dwell and the transport characteristics of the patient's peritoneum. UF can range from zero to <NUM>% of the prescribed fill volume. Thus, it is not unusual for the intra-peritoneal volume reach about <NUM>% of the prescribed fill volume. In practice, it is expected that the IPV will vary between <NUM> and <NUM>% of the prescribed fill volume.

When the residual volume at the end of drain increases, e.g., to more than five or ten percent of the prescribed fill volume, the patient's intra-peritoneal volume increases accordingly during the next fill and dwell. If system <NUM> sets an <NUM>% minimum drain percentage limit, the increase in residual volume is limited to <NUM>% per cycle plus the actual UF obtained during the cycle. Successive fill cycles after successive drains just meeting the <NUM>% minimum drain percentage requirement will cause the patient's intra-peritoneal volume to increase at each successive cycle. System <NUM> also tracks cumulative UF and places a limit on the maximum negative UF value allowed. If this value is exceeded at any time during a therapy, system <NUM> will not advance from drain phase to the next fill phase even if the minimum drain percentage has been met when the drain ends. System <NUM> in one embodiment allows the patient or caregiver, in certain instances, to override the negative UF alarm and allow the therapy to advance to the next fill.

<FIG> illustrates a therapy in which successive drains just meet the minimum <NUM>% drain volume and system <NUM> advances the therapy in each case to the next full fill. System <NUM> allows the intra-peritoneal volume to increase past the <NUM>% of prescribed fill volume limit (<NUM>, after third fill), through the <NUM>% of prescribed fill volume limit (<NUM>, after fourth fill) and into the <NUM>% of prescribed fill volume limit (<NUM>, after fifth fill). The actual UF per cycle in the therapy of <FIG> is <NUM> per cycle which equals <NUM>% of the <NUM> fill volume.

System <NUM> in <FIG> posts a negative UF alarm when drain <NUM> ends with the minimum drain percentage just met because the cumulative negative UF has reached its limit, e.g., <NUM> (four drains x <NUM>% of <NUM>). The patient or caregiver in the illustrated example elects to bypass the negative UF alarm, so that system <NUM> advances to the fifth full fill, in which case the patient's intra-peritoneal volume exceeds a <NUM>% of the fill volume limit (<NUM> x <NUM> = <NUM>).

The therapy illustrated by <FIG> fills the patient with <NUM> of fluid during each of the night fills using all <NUM>,<NUM> of solution available for use during therapy. However, during this therapy, the patient's IPV reaches <NUM>, which is <NUM>% of the prescribed fill volume. Furthermore, the patient encounters and has to address an alarm (negative UF) that interrupts his/her sleep.

<FIG> is illustrative of a therapy per the first step in an embodiment in which the patient volume stays below <NUM>% of the prescribed fill volume. The patient does not encounter any alarms during the night. As seen, the therapy of <FIG> encounters the same drain issues as the therapy illustrated in <FIG>. Drains <NUM> through <NUM> each end with only <NUM>% of the preceding fill volume recovered. Cumulative negative UF increases in <NUM>% steps to <NUM>% at the end of drain <NUM>.

System <NUM> in the example of <FIG> places a <NUM>% limit on negative UF (as opposed to <NUM>% (= <NUM>/<NUM> in <FIG>), so that system <NUM> causes Fill <NUM> to be shorted by <NUM>%, limiting the negative UF at <NUM>%. System <NUM> shorts Fill <NUM> by <NUM>% because Drain <NUM> was also <NUM>% short. The maximum value for the IPV is <NUM> (<NUM>% of prescribed fill volume) during this therapy. The <NUM>% negative UF limit could have been set to a lower value, such as <NUM>%, limiting the maximum IPV to <NUM>.

The therapy illustrated in <FIG> prevented the IPV from exceeding <NUM>% of the prescribed fill volume but did allow the IPV to exceed <NUM>% of the prescribed fill volume. The therapy of <FIG> used only <NUM>,<NUM> of the <NUM>,<NUM> of dialysis fluid that was available. Assuming the fluid could have been used to its maximum potential, the therapy illustrated in <FIG> was <NUM>% effective in delivering the maximum possible therapeutic benefit. The therapies illustrated in <FIG> and <FIG>, on the other hand, were <NUM>% effective.

The therapies illustrated in <FIG> and <FIG> are considered to be CCPD therapies because all drains are prescribed to go to empty. The only drains that actually made it to empty, however, were the initial drain and the last drain in which the patient was awake and could move around, or sit up, to drain fully. The CCPD therapies are accordingly pseudo-tidal in nature. If they had been programmed as tidal therapies with a tidal percent of <NUM>%, all of the drains in <FIG> and <FIG> would have ended when <NUM>% of the programmed fill volume plus expected UF had been drained. The following fills would have brought the patient volume back to <NUM>% of the programmed fill volume.

<FIG> and <FIG> demonstrate the operation of steps <NUM> and <NUM> of a method of one embodiment, with respectively, <NUM>% and <NUM>% tidal volumes, rather than the <NUM>% discussed above with respect to <FIG>. In <FIG>, the operation of a <NUM>% tidal system is depicted, each with an additional cycle as compared to <FIG>. In <FIG>, the system operates as intended, and in this case, an "ideal" patient responds as intended. In <FIG>, <NUM> is used for the first, <NUM>% fill, and all drains except the first and the last are about <NUM>. This represents <NUM>% of a <NUM> fill volume and a calculated <NUM> UF. Note that <NUM> cycles with <NUM> of UF would remove a total of about <NUM> ultrafiltrate over the duration of the nocturnal therapy. The patient volume does not appear to reach even <NUM>, i.e., does not even reach <NUM>% over the initial patient volume (IPV). As seen in <FIG>, each cycle lasts about <NUM> hours and there are a total of six cycles, for a <NUM>-hour therapy, from about <NUM>:<NUM> pm to about <NUM>:<NUM> the next morning.

In <FIG>, the same <NUM> fill volume is used, but in this case, the patient does not drain as expected. The same drain volume, about <NUM>, is expected, but does not occur in every drain cycle. In the first drain cycle, only about <NUM> is drained. In addition, drains <NUM> and <NUM> are also short, as can be seen by observing the increasing patient volume fill. Even in this situation, however, the peak patient fill volume appears to reach about <NUM>, i.e., about <NUM>% of IPV, which is not ideal but is considerably less than the <NUM>% required for a "moderate excess" intraperitoneal volume and is far less than the previous situation seen in <FIG> or <FIG>.

The total prescribed therapy volume is also used in the therapy depicted in <FIG>. In <FIG>, cycles <NUM>, <NUM>, <NUM> and <NUM> have short drains, as seen by the increasing patient fill volume over the six cycles, rising to almost <NUM>. The tidal therapy shown in <FIG> shorts the last fill by about <NUM> in order to limit the IPV to <NUM>% of the prescribed fill volume. This reduces the effectiveness of the <NUM>,<NUM> night therapy by about <NUM>% based upon the actual fluid volume used, (<NUM>-<NUM>)/<NUM> = <NUM>%. Note that no alarms were necessary in any of the therapies depicted in <FIG>.

If a fluid volume exceeding a predetermined limit remains unused nearly every day, a switch can be made from a <NUM>% tidal therapy to a <NUM>% tidal therapy allowing the based residual volume to increase by another <NUM>%. <FIG> illustrate how such a therapy would limit the IPV while using all of the available fluid and maintaining the predicted dwell times. The patient would seldom get a low drain volume alarm or a negative UF alarm when the base therapy is assumed to be tidal instead of CCPD. In <FIG>, the therapy is now <NUM>% tidal therapy, with <NUM> additional cycles over those of <FIG> required in order to use the total prescribed therapy volume. <FIG> depicts a relatively ideal situation, in which a patient has all drains, except the first and the last, at about <NUM>, representing <NUM>% of <NUM> of fill volume and <NUM> UF (<NUM> UF over <NUM> cycles would remove about <NUM> UF). Each cycle is now a little shorter, about <NUM> hour and <NUM> minutes, for a total therapy time of about <NUM> hours and <NUM> minutes. In this idealized situation, the patient fill volume does not exceed <NUM>, that is, does not go over about <NUM>% of the prescribed fill volume.

The patient response in <FIG> is somewhat less ideal, with the first drain about <NUM> short (about <NUM>% less than expected). Each drain is expected to be about <NUM>, with <NUM>% of <NUM> fill volume (<NUM>) and <NUM> UF. While the first drain is short, the remaining drains are on target until the last drain, which is about <NUM>. This therapy is still very well-behaved, with no alarms and patient IPV not exceeding the negligible excess level (less than <NUM>% IPV). In <FIG>, however, several drains are short, e.g., the first and second drains are about <NUM> short. The tidal therapy is offset each time by the <NUM> drain shortage, i.e., the tidal therapy volume increases by about <NUM>. Nevertheless, since the patient volume does not exceed the negligible excess level, the subsequent fills on cycles <NUM> and <NUM> are not shorted. Thus, the total therapy volume is used and the patient is still not upset by unnecessary alarms during the nocturnal therapy. Of course, if the volume were to exceed one of the thresholds, the controls could be programmed to short one or more of the cycle fill volumes.

<FIG> depicts another patient therapy with some of the same shortcomings as <FIG>. As in <FIG>, there are two additional cycles and two short drains, drains <NUM> and <NUM>, as seen by the increase in IPV at cycles <NUM> and <NUM>. The negligible excess level is not exceeded, and as before, there are no alarms since the IPV level does not exceed the negligible excess level of less than <NUM>% of patient volume. The total therapy volume is also used in this situation. <FIG> depicts another therapy performance. In this depiction, the first, second and fourth drains are each short by about <NUM>. Thus, the total patient volume rises by about <NUM>, which is still within the negligible excess IPV limit.

The therapies of <FIG> and <FIG> limit the maximum patient fill volume while using all the dialysis solution that is prescribed and available. At the same time, the therapy may be programmed to withhold therapy volume if the patient drain is much less than expected and the patient fill volume would cross an unacceptable threshold. Extra cycles may be added, each cycle an appropriate amount shorter, so that each fill is as effective as possible, the available solution is used, the available time is used, and alarms that disturb and disrupt a patient are kept to a minimum.

If drains continue to be shorted beyond the three shown in <FIG>, however, such that maximum IPV grows (or is predicted to grow) to <NUM> or greater (thirty percent or greater than initial fill volume), system <NUM> will stop offsetting the base patient volume and will short the next fill. The offset of the base patient volume is limited to <NUM>% of the initial fill volume less the expected UF per cycle. System <NUM> in one embodiment posts a low drain volume alarm if ending the drain would result in an IPV on the next fill that would exceed <NUM>% of the programmed fill volume not including UF. In one embodiment, system <NUM> limits the maximum IPV to <NUM>% of the programmed fill volume (initial fill volume for tidal therapies). The offset limit can be adjusted to a value other than <NUM>% if necessary, for example from <NUM>% to <NUM>%. The offset limit with tidal is similar to the negative UF limit that was imposed on the CCPD Therapy.

The method disclosed herein may progress gradually from an <NUM>% CCPD (pseudo tidal) therapy to a <NUM>% tidal therapy to a <NUM>% tidal therapy and even to a <NUM>% tidal therapy as it seeks to use all of the available dialysis solution, minimize the increased intra peritoneal volume and minimize the number of low drain alarms. Patient volume offsets will be allowed as long as they do not exceed a predetermined programmable limit that will be defaulted to <NUM>%. Cycles will be added each time the tidal percentage decreases so that all of the dialysis solution volume is used. The base patient fill volume may also be adjusted up or down <NUM>-<NUM>% during this process so that no fluid volume is wasted.

As discussed in more detail below, in one embodiment, system <NUM> trends UF based upon the dialysis solution used. For example, for a particular patient, the expected UF per therapy might be <NUM> with <NUM>% dextrose, <NUM> with <NUM>% dextrose, <NUM> with <NUM>% dextrose and <NUM> with <NUM>% dextrose. System <NUM> in one embodiment is programmed to notify the patient if the programmed total UF at the beginning of treatment differs by more than <NUM>% from the trended UF for the particular dextrose concentration being used.

It is believed that system <NUM> will encounter fewer low drain volume alarms and virtually no negative UF alarms when compared to current CCPD therapies. The system will consistently use the total dialysate volume available and will not allow the patient's IPV to exceed <NUM>% of the programmed fill volume.

<FIG> shows that the occurrence of non-initial drain alarms that are posted during a therapy would be expected to decrease to less than half (<NUM>/. <NUM>) its current number if the minimum drain percentage were decreased from <NUM>% to <NUM>%. The alarm decrease would be to about <NUM>/<NUM> (<NUM>/<NUM>) if the minimum drain percentage were decreased to <NUM>% from <NUM>%.

System <NUM> in one embodiment also averages both the per cycle fill volume and per cycle dwell time after manual drains or bypasses in fill that alter the volume of fluid remaining, as will be explained below for <FIG>. System <NUM> recalculates the therapy after such manual drain or bypass in fill that alters the volume of fluid remaining, calculating a revised average dwell time for each the remaining cycles. System <NUM> also calculates a revised (potentially) remaining number of cycles, which is calculated by dividing the total remaining therapy fluid volume less a "last fill" or "wet day" fill volume by the prescribed fill volume: <MAT>.

System <NUM> in one implementation rounds up a fractional portion of a cycle if it is greater than <NUM> and divides both the total remaining therapy volume and therapy time equally over the rounded-up number of cycles remaining. Otherwise, the calculated number of cycles is truncated, and system <NUM> divides both the total remaining therapy volume and therapy time equally over the truncated number of cycles remaining.

<FIG> illustrate how cycles can be added or at least not dropped in order to use all of the available fluid. The same concept carries over into drains when cycles are added. The principle is to use as much fluid as possible so as to give the maximum benefit to the patient while wasting as little fluid as possible.

<FIG> illustrates a treatment in which the first fill uses less fluid than normal because of a bypass of the fill. For example, if a user feels full and uses a manual drain or does not use a full fill. As a result, <NUM>, <NUM> or <NUM> of fluid (out of <NUM>) was used in the first fill. System <NUM> spreads the remaining volume evenly over the remaining cycles, which are increased in <FIG> from three to four. If the full <NUM> is used in the first fill then the top or highest fill line shows that the therapy proceeds with three additional <NUM> fills for total of <NUM>. If only <NUM> is used in the first fill then the second or next highest fill line shows that the four fills at about <NUM> are performed to use the total <NUM>. If only <NUM> is used in the first fill then the third line shows that the four fills of about <NUM> are performed to use the total <NUM>. If only <NUM> is used in the first fill then the lowest of the four fill lines shows that the four fills at about <NUM> are performed to use the total <NUM>. The result again is a more effective therapy.

<FIG> illustrates a scenario in which the first fill uses more fluid than normal because of a manual drain in the first fill. Here, system <NUM> averages the remaining therapy volume over the remaining four cycles instead of dropping a cycle and retaining the original fill volume. The result again is a more effective therapy.

Referring now to <FIG>, flow diagram <NUM> illustrates one embodiment of a system <NUM> which may be used in either CCPD or tidal mode. The method begins at oval <NUM>. At block <NUM>, the user sets a programmable negative UF limit that is used to determine when to use shorter fill volumes after one or more incomplete drains when running a CCPD therapy or a Tidal therapy. As seen in blocks <NUM>, <NUM>, the system <NUM> tracks UF and calls for a short fill if needed, in both CCPD mode and in Tidal mode.

At block <NUM>, system <NUM> performs an initial drain, followed by block <NUM> with a fill. Per block <NUM>, for drains after the initial drain, a shorter fill volume will be used, i.e., the fill is shorted, if the previous drain falls short of the target volume and the UF limit is exceeded. After the fill, a dwell at block <NUM> is performed, the dwell calculated as discussed below. After the dwell, a drain is performed at block <NUM>. Based on the drain, the number of remaining cycles and the dwell time is calculated at block <NUM>. The dwell time is calculated at block <NUM> to use all the allocated therapy time. In both the CCPD and tidal modes, system <NUM> tracks UF, offsets the residual patient volume and maintains the tidal fill volume if a tidal drain is incomplete as long as the sum of the increases in residual patient volume and expected UF do not exceed the negative UF Limit.

For CCPD therapies, system <NUM> calculates the remaining number of CCPD cycles using the equation: Cycles Remaining = (total remaining therapy volume - last fill volume (if any))/(programmed fill volume).

For Tidal therapies after an incomplete tidal drain, or after a complete full drain, system <NUM> calculates the remaining number of tidal cycles using the equation: Cycles Remaining = <NUM>+ (Remaining Therapy Volume - Fill Volume - Last Fill Volume)/(Tidal PerCent * Fill Volume).

For Tidal therapies after a complete tidal drain, system <NUM> calculates the remaining number of tidal cycles using the equation: Cycles Remaining = (Remaining Therapy Volume - Last Fill Volume)/(Tidal PerCent * Fill Volume).

At diamond <NUM>, if the fractional number of cycles exceeds <NUM>, the number of cycles is rounded up to the nearest integer, per block <NUM>. For example, if the fractional number of cycles remaining is <NUM>, the number of cycles remaining is rounded up to <NUM>; if the number of cycles remaining is <NUM>, the number of cycles remaining is rounded up to <NUM>. At diamond <NUM>, system <NUM> compares the number of remaining cycles to zero. If the number of cycles remaining is greater than zero, the next fill is performed, per block <NUM> and the process is repeated. If the number of cycles is zero, the therapy is complete, per block <NUM>.

Returning to diamond <NUM>, if the fractional number of cycles is less than <NUM>, the path moves to block <NUM>, where the number of cycles is rounded down or truncated. At the next step, at diamond <NUM>, system <NUM> compares the number of remaining cycles to zero. If the number of cycles remaining is greater than zero, the next fill is performed, per block <NUM> and the process is repeated. If the number of cycles is zero, the therapy is complete, per block <NUM>.

At block <NUM>, system <NUM> performs an initial drain, followed by a fill at block <NUM>. If the previous drain falls short of the target volume and the UF limit is exceeded, then per block <NUM>, for drains after the initial drain, a shorter fill volume will be used, i.e., the fill is shorted. After the fill, a dwell at block <NUM> is performed, the dwell calculated as discussed below. After the dwell, a drain is performed at block <NUM>. Based on the drain, the number of remaining cycles and the dwell time is calculated at block <NUM> in order to use all of the allocated therapy time. In both the CCPD and tidal modes, system <NUM> tracks UF, offsets the residual patient volume and maintains the tidal fill volume if a tidal drain is incomplete, as long as the sum of the increases in residual patient volume and expected UF do not exceed the negative UF Limit.

For CCPD therapies, system <NUM> calculates the remaining number of CCPD cycles using the equation: Cycles Remaining = (total remaining therapy volume - last fill volume (if any))/( programmed fill volume).

For Tidal therapies after a tidal drain that ends prematurely due to an empty patient, or after a tidal full drain, system <NUM> calculates the remaining number of tidal cycles using the equation: Cycles Remaining = <NUM>+ (Remaining Therapy Volume - Fill Volume - Last Fill Volume)/(Tidal PerCent * Fill Volume).

For Tidal therapies after a normal tidal drain, system <NUM> calculates the remaining number of tidal cycles using the equation: Cycles Remaining = (Remaining Therapy Volume - Last Fill Volume)/(Tidal PerCent * Fill Volume).

At diamond <NUM>, if the fractional number of cycles exceeds <NUM>, the number of cycles is rounded up to the nearest integer, per block <NUM>. For example, if the fractional number of cycles remaining is <NUM>, the number of cycles remaining is rounded up to <NUM>. At diamond <NUM>, system <NUM> compares the number of remaining cycles to zero. If the number of cycles remaining is greater than zero, the next fill is performed, per block <NUM> and the process is repeated. If the number of cycles is zero, the therapy is complete, per block <NUM>.

Returning to diamond <NUM>, if the fractional number of cycles is less than <NUM>, the process path moves to diamond <NUM>. At this point, the fractional number of cycles is compared to <NUM> (<NUM>% of a cycle). If the fractional number remaining is less than <NUM>, the number of cycles is rounded down, or truncated at block <NUM> and the process moves to diamond <NUM>, where the remaining number of cycles is compared to zero. If the number of cycles remaining is greater than zero, the next fill is performed, per block <NUM> and the process is repeated. If the number of cycles is zero, the therapy is complete, per block <NUM>.

Returning to diamond <NUM>, if the fractional number of cycles is greater than <NUM>, a new higher fill volume is calculated with a truncated number of cycles at block <NUM>. At diamond <NUM>, the ratio of Increased Fill to Prescribed Fill is calculated. If the ratio is not greater than <NUM>, i.e., the volume increase is less than <NUM>%, the increased fill volume is taken as the new set point at block <NUM>. The number of cycles is truncated at block <NUM>, and the number of remaining cycles is then compared to zero at diamond <NUM>. If no cycles remain, the therapy is completed at block <NUM>. If <NUM> or more cycles remains, the process advances to block <NUM> and is repeated.

Returning to diamond <NUM>, if the increase is greater than <NUM>%, a decreased fill volume is calculated, based on a rounded-up number of cycles at block <NUM>. The number of cycles is rounded up at block <NUM> and the set fill volume is reset to a decreased fill volume. The process then returns to diamond <NUM> for another cycle if appropriate.

Example for Patient A: Tables <NUM>, <NUM>, <NUM> and <NUM> contain system <NUM> drain volume/fill volume (DV/FV) ratios, UF/fill (UF/FV) volume and ratios of unused fluid volume/fill (Unused Fluid/FV) volume ratios for CCPD therapies for Patient A with the negative UF limits set to <NUM>%, <NUM>%, <NUM>% and <NUM>%, respectively. The average drain volume/fill volume ratio in Drain <NUM> of <NUM> decreases as the fraction of unused fluid volume increases when the negative UF limit decreases from <NUM>% to <NUM>%. The maximum drain/fill volume (DV/FV) ratio decreases from <NUM> to <NUM>.

Example for Patient B: Tables <NUM>, <NUM>, <NUM> and <NUM> contain system <NUM> drain volume/fill volume ratios, UF/fill volume ratios and unused fluid volume/fill volume ratios for CCPD therapies for Patient B with the negative UF limits set to <NUM>%, <NUM>%, <NUM>% and <NUM>%, respectively. The average drain volume/fill volume (DV/FV) ratio in Drain <NUM> of <NUM> decreases as the fraction of unused fluid volume increases when the negative UF Limit decreases from <NUM>% to <NUM>%. The maximum DV/FV ratio decreases from <NUM> to <NUM>, as seen in <FIG>.

With the negative UF Limit set at <NUM>%, neither Patient A nor Patient B encounters a drain/fill volume ratio that exceeds <NUM> during the course of the twenty therapies comprising data contained in Tables <NUM> and <NUM>, each therapy including five cycles. The unused fluid/fill volume ratio with the <NUM>% negative UF limit in Tables <NUM> and <NUM> averages <NUM>% and <NUM>%, which means that <NUM>% and <NUM>% of <NUM> (<NUM> to <NUM>) of dialysis solution is unused. Thus, system <NUM>, using the negative UF limit to determine when to short fill volumes without increasing the number of cycles, would reduce the effectiveness of the <NUM>,<NUM> therapy by around <NUM>% (<NUM>/<NUM>,<NUM> = <NUM>%, to <NUM>/<NUM>,<NUM> = <NUM>%).

Referring now to <FIG>, flow diagram <NUM> illustrates one embodiment of a system <NUM> in which CCPD therapy is intended and begun. In this embodiment, the therapy may be switched to tidal therapy if the drains are incomplete or if too much dialysis fluid is not being used. The method begins at oval <NUM>. At block <NUM>, the system <NUM> performs an initial drain, followed by block <NUM> with a fill. Per block <NUM>, for drains after the initial drain, a shorter fill volume will be used, i.e., the fill is shorted, if the previous drain falls short of the target volume and the UF limit is exceeded. The user sets a programmable negative UF limit, such as <NUM>% negative UF, that is used to determine when to use shorter fill volumes after one or more incomplete drains when running a CCPD therapy, or if a switch has been made, when running a Tidal therapy. Other limits may be used, as mentioned above for the processes of <FIG> and <FIG>.

After the fill, a dwell at block <NUM> is performed, the dwell calculated as previously discussed. After the dwell, a drain is performed at block <NUM>. Based on the drain, the ratio of the drain volume to fill volume is calculated, and the ratio for the last twenty drains is calculated and stored at block <NUM>. At diamond <NUM>, the system questions whether a short fill was enabled for the previous cycle. If not, the ratio for the previous twenty cycles is compared to determine whether any of the cycles had a ratio greater than <NUM> at diamond <NUM>. If not, the process continues to block <NUM> where the number of remaining cycles and the dwell time is calculated. If any of the previous twenty cycles had a ratio greater than <NUM>, then the process enables short fills at the set limit for negative UF, such as <NUM>% UF, at block <NUM>, and then proceeds to block <NUM>.

Returning to diamond <NUM>, if a short fill was enabled for a previous cycle, the process continues to diamond <NUM>. At this point, the ratios are analyzed to determine whether the ratio exceeded <NUM> for five of the twenty previous cycles. Other embodiments may use other benchmarks than five of the previous twenty cycles, for example, four or six of the previous ten cycles. If yes, the negative UF limit may be reset or lowered <NUM>% and the process continued to block <NUM>. If not, the process also continues to block <NUM>. At block <NUM>, the patient fill volume is reset to the negative UF limit minus the accumulated negative UF. For all the eventualities from blocks <NUM> and <NUM>, and diamonds <NUM>, <NUM> and <NUM>, the next step is block <NUM>, at which the remaining number of cycles and the dwell time for each is calculated.

For CCPD therapies, system <NUM> calculates the remaining number of CCPD cycles using the equation: Cycles Remaining = (total remaining therapy volume - last fill volume (if any))/( programmed fill volume). For Tidal therapies after an incomplete tidal drain, or after a complete full drain, system <NUM> calculates the remaining number of tidal cycles using the equation: Cycles Remaining = <NUM>+ (Remaining Therapy Volume - Fill Volume - Last Fill Volume)/(Tidal PerCent * Fill Volume). For Tidal therapies after a complete tidal drain, system <NUM> calculates the remaining number of tidal cycles using the equation: Cycles Remaining = (Remaining Therapy Volume - Last Fill Volume)/(Tidal PerCent * Fill Volume).

At diamond <NUM> if the fractional number of cycles exceeds <NUM>, the number of cycles is rounded up to the nearest integer, per block <NUM>. At diamond <NUM>, system <NUM> compares the number of remaining cycles to zero. If the number of cycles remaining is greater than zero, the next fill is performed, per block <NUM> and the process is repeated. If the number of cycles is zero, the decision tree proceeds to diamond <NUM>. If no additional cycles were required in ten or more of the previous twenty therapies, the therapy is complete, per block <NUM>. If additional cycles were required in ten or more of the previous twenty therapies, diamond <NUM> asks whether the current therapy is tidal (not CCPD). If the current therapy is tidal and is not CCPD, a recommendation is made for the next therapy to reduce the tidal volume by <NUM>% in block <NUM>. Therapy is adjudged complete for this particular therapy at block <NUM>. Returning to block <NUM>, if the patient is presently using CCPD therapy, and additional cycles were required in ten or more (half of more) of the previous twenty therapies, a switch to <NUM>% tidal therapy is recommended for the next therapy, after which the present therapy is complete.

Returning to diamond <NUM>, if the fractional number of cycles is less than <NUM>, the process moves to diamond <NUM>, and the number of fractional cycles is compared to <NUM>. If the fractional number of cycles is less than <NUM>, the remaining number of cycles is truncated at block <NUM> and the truncated or rounded down number of cycles is compared to zero at block <NUM>. If the number of remaining cycles is zero, the process follows the decision tree discussed above for diamond <NUM>. If the number of remaining cycles is an integer of <NUM> or more, the next fill is performed, per block <NUM>.

Returning to diamond <NUM>, if the fractional cycle remaining exceeds <NUM>, a truncated number or rounded down number of cycles is used to calculate an increased fill volume at block <NUM>. At block <NUM>, the increased fill volume based on the lower number of cycles is compared with the fill volume based on the present prescription. The fill volume is calculated to use the total therapy volume in the rounded down or truncated number of cycles. The volumes are calculated as follows: <MAT>.

If the ratio of the increased fill volume to prescribed fill volume based on the lower number cycles is less than <NUM> (i.e., the increase is less than <NUM>%), as seen at diamond <NUM>, system <NUM> resets the fill volume for the next fill to the calculated increased fill volume at block <NUM>. The system then uses the truncated number of cycles, per block <NUM>, and returns through comparison diamond <NUM> to the next fill at block <NUM> or the decision tree at block <NUM>. The ratio at block <NUM> may be greater than <NUM>, reflecting a significant increase in the fill volume of the next cycle compared with the most recent. In order to avoid such abrupt changes, the system <NUM> at block <NUM> then rounds up the previously-truncated number of cycles (from block <NUM>) and then calculates a decreased fill volume using the higher number of cycles. The calculation used is: <MAT>.

The system <NUM> then uses this rounded-up number and a decreased fill volume at block <NUM> for the next cycle. This decreased fill volume is noted and is tracked at block <NUM> as an added cycle. The added cycle is noted in comparison diamond <NUM>.

Example for Patient C, per Table <NUM> and <FIG>: The negative UF limit may be combined with the Unused fluid volume limit to better control the operation of system <NUM>, as seen in <FIG>. Table <NUM> contains four sub-tables, three similar to the others discussed above, and a fourth sub-table that depicts the actual fill volume/programmed fill volume (Actual FV/Programmed FV). This fourth sub-table demonstrates that the increased fill volume due to incomplete drains, in this case, does not exceed <NUM>% of the programmed fill volume, as was the case above in the Example for Patient A and Patient B. However, in this case, a cycle is added any time the Unused Fluid/Fill Volume ratio in any of columns <NUM> through <NUM> goes more negative than -<NUM>. In fifteen of the <NUM> therapies all of the available fluid is used (see column <NUM>, "<NUM>" unused fluid/FV ratio).

At the present time in <NUM>, most APD patients perform CCPD therapies and there is no UF limit that results in an automatic shorting of the next fill when a drain is not complete. Succeeding fills are always full if the minimum drain volume was achieved during the previous drain. A negative UF alarm is sounded if the accumulation of negative UF exceeds an alarm limit, typically set at <NUM>% of the programmed fill volume. The tracking of negative UF is based solely upon the volume drained less the volume filled and does not account for ultra-filtration across the peritoneal membrane. The method described herein tracks the ratio of the volume drained to the prescribed fill volume. Per the discussion above for <FIG>, if this ratio exceeds <NUM> once in every twenty drains, or if the ratio exceeds <NUM> five times in every twenty drains, the system will suggest that the user Enable the negative UF limit algorithm to limit fill volumes and add cycles as necessary to reduce the magnitude and incidence of increased intra-peritoneal volume.

<FIG> illustrates how the system monitors CCPD drain ratios and uses the results to suggest when the user should enable the negative UF limit algorithm to limit IIPV. The system will lower the UF threshold for shorting fills to limit the incidence of IIPV and low drain alarms. The system will also suggest when the user should switch to a tidal therapy.

As described above for block <NUM>, system <NUM> suggests activating the negative UF limit algorithm if a drain volume/fill volume ratio exceeds <NUM> during any of the Drains <NUM> through N drains (the last drain) in more than one per twenty therapies.

At block <NUM>, system <NUM> suggests lowering the negative UF limit setting if a drain/fill volume exceeds <NUM> during the first drain through N drains (the last drain) more than x occurrences in y therapies, e.g., more than five times in twenty therapies. Other embodiments may use other limits, for the drain volume/fill volume ratio, for the number of therapies in which a particular high ratio is encountered, or for both.

At diamond <NUM>, system <NUM> monitors the drain to fill volume ratio and also monitors the unused fluid/fill volume (FV) ratio and determines whether the unused fluid/FV exceeds a certain ratio in a number of cycles in a given therapy. For example, system <NUM> may set <NUM>% (a ratio of <NUM>) in any of cycles <NUM> through N-<NUM> of N (that is, the second-next-to last, e.g., cycles <NUM>-<NUM> in a five-cycle therapy or cycles <NUM>-<NUM> in a six-cycle therapy). In another example, the system may use <NUM>% (a ratio of <NUM>) in cycles <NUM> through N-<NUM> (next to last), e.g., cycles <NUM>-<NUM> in a five-cycle therapy or cycles <NUM>-<NUM> in a six-cycle therapy, for which an example is given in Table <NUM>. Note that in Table <NUM>, the UF/FV ratio for day <NUM> at cycle <NUM> is -<NUM>, which exceeds the negative <NUM>% limit that was used when generating Table <NUM>. Thus, the next cycle is shorted by <NUM>%, leading to an Unused Fluid/FV for day <NUM>, cycle <NUM>, of -<NUM>. At cycle <NUM>, the UF/FV ratio rises to -<NUM>, i.e., again negative UF. Cycle <NUM> is now shorted <NUM>% (-<NUM> = - <NUM> -<NUM> for Unused Fluid/FV at day <NUM>, cycle <NUM>, since -<NUM> - (-<NUM>) = -<NUM>). The result of Cycle <NUM> is still negative UF (-<NUM>) and cycle <NUM> is again shorted (-<NUM> Unused Fluid/FV). Since <NUM> exceeds <NUM> (<NUM>%), the number of cycles is increased by <NUM> (adding a sixth cycle) and the target patient fill volume is decreased, so that the remainder of the dialysis fluid is used in the sixth cycle.

At block <NUM>, using the <NUM>% example and if unused fluid/FV exceeds <NUM>%, system <NUM> increases the remaining number of cycles by <NUM> and distributes the remaining dwell time and remaining therapy volume evenly over the increased remaining number of cycles (see, e.g., in Table <NUM>, day <NUM>, number of cycles increased to six when the unused fluid/FV ratio exceeds <NUM> (actually <NUM>) in the column for cycle <NUM>. At blocks <NUM> and <NUM> after the next fill cycle, system <NUM> calculates the unused Fluid/FV ratio (remaining cycler fraction) to zero for a therapy with a cycle added.

Returning to diamond <NUM>, if the unused fluid/FV ratio is less than <NUM>%, the system instead moves to diamond <NUM> and through eventually to diamond <NUM> when all of the available fluid has been delivered. At diamond <NUM>, system <NUM> monitors the frequency at which an increased number of cycles is needed to prevent fluid loss in excess of a given percentage A (e.g., <NUM>%) of the fill volume. If the frequency is equal to or greater than <NUM>% of the time (e.g., ten times or more over twenty therapies), system <NUM> at block <NUM> suggests that the patient be converted to a tidal therapy since the patient is already in effect performing an <NUM>% tidal therapy. For example, switching to a <NUM>% tidal therapy may be a more effective use of the fluid volume that is available while minimizing the magnitude of excess intra-peritoneal volume and reducing the frequency of low drain volume alarms.

At block <NUM>, system <NUM> uses UF trending discussed below to monitor the <NUM>% (or current) tidal therapy. At diamond <NUM>, system <NUM> determines whether the frequency at which the patient's residual volume has to be offset over time is greater than a specified percentage of the time, e.g., <NUM>% percent of the time. If so, system <NUM> suggests switching to a lower percentage, e.g., <NUM>%, tidal therapy at block <NUM> for the next therapy. If the residual volume still has to be offset greater than a certain percentage, e.g., <NUM>%, of the time, as determined at diamond <NUM>, the loop continues to lower the tidal percentage until the residual drain volume is lowered to an acceptable level, at which time the method of logic flow diagram <NUM> ends. Tidal therapies are still effective with regard to solute removal for tidal percentages as low as about <NUM>%. Ultra-filtration can be maintained at tidal percentages lower than <NUM>%.

If a patient still has drain issues with a tidal percentage of around <NUM>%, the patient is a candidate for multi-pass continuous flow peritoneal dialysis (Multi-Pass CFPD) as discussed in <CIT>. Multi-Pass CFPD continuously fills and drains the patient using either a dual lumen catheter as discussed in <CIT> and <CIT>. Alternatively, two single lumen catheters may be used. The patient is only drained to below the prescribed fill volume prior to the start of the Multi-Pass CFPD therapy and at the end of the Multi-Pass CFPD therapy. Low drain volume alarms are virtually eliminated. Check Patient line alarms can still occur if the patient line becomes kinked.

As discussed above, there is a need for an automated peritoneal dialysis therapy that ensures the use of all of the prescribed dialysis solution, can finish on time, can minimize if not eliminate low drain volume alarms and can prevent the volume of fluid in the patient's peritoneum from exceeding the programmed fill volume by more than about the amount of expected ultrafiltration ("UF") obtained from the patient over one dwell cycle. Properly estimating a patient's UF for a given solution is therefore important. It is contemplated that system <NUM>, instead of using predicted UF values, uses recently trended UF values for the same type of treatment using the same type of PD solution.

Referring now to <FIG>, a trend for a <NUM>% tidal therapy with programmed UF based upon trending is shown for both <NUM>% and <NUM>% dextrose concentration dialysis solution types. The trended <NUM>% therapy for the patient shows that about <NUM> of UF is removed if that patient uses <NUM>% dextrose and <NUM> of UF is removed if that patient uses <NUM>% dextrose.

The total UF is then divided out over the number of night therapy cycles (fills/dwells/drains) to determine the UF per cycle, e.g., four cycles resulting in <NUM> UF for <NUM>% dextrose and <NUM> of UF for <NUM>% dextrose. The values of <NUM> and <NUM> are added to the prescribed fill volumes to determine a patient's maximum allowable IPV in one embodiment. The maximum IPV is then used to determine the volume of residual fluid that should remain in the patient's peritoneum after a drain. For example, if the patient's maximum IPV is <NUM> (<NUM> fill plus <NUM> UF), the residual volume for a fifty percent tidal drain should be <NUM>. Just as important, the cycler of system <NUM> will attempt to remove <NUM> over the drain.

<FIG> shows, for each dextrose level, each day's UF entry. System <NUM> in one embodiment determines the actual UF removed from the patient over the course of a night therapy (not counting last fill or day exchange). The actual UF measurement assumes a complete (to zero ml) drain prior to both the first fill and last or day fill (if performed). In this manner, System <NUM> knows how much fresh dialysate has been delivered to the patient and how much spent dialysate (including UF) has been removed from the patient over the nightly treatment. The difference is the night therapy UF, which is logged into data storage for the patient, the concentrate and therapy, and used to further update the trend. UF can be plotted as a single day (<FIG>) or as a rolling average (<FIG>). <CIT>, discloses different rolling average UF trends and trends using statistical process control ("SPC") for alarming/alerting. Such trends can be used alternatively or additionally to the single day trend shown in <FIG>.

<FIG>, <FIG>, <FIG> and <FIG> illustrate four different treatment scenarios. The continuous line indicates the volume of fluid that system <NUM> delivers and removes from the patient over time. The dashed line indicates the actual volume of fluid residing in the patient ("IPV") at any given point in time. The difference between the machine delivered/removed volume and the actual volume is the patient's UF. The dotted line indicates the actual UF removed from the patient over time.

<FIG> illustrates a <NUM>% tidal therapy using <NUM>% dextrose dialysate. The trended <NUM> total UF for such treatment is recalled from memory of system <NUM> and used to simulate the patient's actual IPV. The <NUM> UF is split amongst ten treatments, yielding <NUM> removed per cycle as shown in <FIG>. <FIG> illustrates a <NUM>% tidal therapy using <NUM>% dextrose dialysate. The trended <NUM> total UF for this treatment is recalled from memory of system <NUM> and used to simulate the patient's actual IPV. The <NUM> UF is also split amongst ten treatments, yielding <NUM> removed per cycle as shown in <FIG>.

<FIG> again illustrates a <NUM>% tidal therapy using <NUM>% dextrose dialysate. The trended <NUM> total UF for such treatment is recalled from memory of system <NUM> and used to simulate the patient's actual IPV. Here, however, the total UF removed is only <NUM>, short by <NUM>. The <NUM> UF is again split amongst ten treatments, yielding <NUM> removed per cycle as shown in <FIG>. Because the predicted UF from the patient's actual trend set a good starting place, and because the <NUM>% tidal therapy is forgiving in terms of having enough planned residual volume to accept lower than expected residual volumes (here due to less UF than expected), the treatment is able to use all of the prescribed solution, maintain the prescribed dwell times and finish therapy on time.

<FIG> again illustrates a <NUM>% tidal therapy using <NUM>% dextrose dialysate. The trended <NUM> total UF for such treatment is recalled from memory of system <NUM> and used to simulate the patient's actual IPV. Here, however, the total UF removed is more than expected, <NUM>, greater by <NUM>. The <NUM> UF is again split amongst ten treatments, yielding <NUM> removed per cycle as shown in <FIG>. Again, the predicted UF from the patient's actual trend set a good starting place. The <NUM>% tidal therapy is forgiving in terms of setting the planned residual volume high enough so that the planned drain can take place each cycle, which at least does not add to the effect of the additional UF. The treatment is thus able to use all of the prescribed solution, maintain prescribed dwell times, and finish therapy on time.

In the therapies of <FIG> and <FIG>, all of the dialysis solution is used, the dwell times are as prescribed, the potential for low drain alarms is minimized and the maximum patient volume is limited to less than that with CCPD therapies. The trending of the UF (based upon osmotic concentration) accordingly allows tidal treatments to be used in a very advantageous manner.

In one embodiment, system <NUM> trends a running average of the patient's UF and displays same for both the patient and clinician. The displayed trended time interval can be varied from a week to a month to multiple months (see also Trending Application). The user in one embodiment can scroll forward or may scroll backward to see the results for the preceding ninety days. System <NUM> in one embodiment enables the user to select the prescription ID axis (e.g., via input device <NUM> (<FIG>) or a touch screen operable with video monitor <NUM>), after which system <NUM> changes the display to that shown in <FIG>, in which two or more different prescriptions or dextrose levels are trended independently.

<FIG> shows which dialysate is used on a given day (prescription <NUM> or prescription <NUM>), the desired UF volume, and a trended rolling seven day average actual UF. System <NUM> can therefore use as its predicted UF the previous day's UF volume (if the same therapy and dialysate is used) or an averaged UF data point for the same dialysate/treatment. As discussed in the Trending Application, the UF trends, e.g., <FIG> and <FIG>, may be maintained at the logic implementer of the cycler <NUM> or at a remote server, e.g., located at a dialysis clinic or doctor's office. In either case, networked communication can allow any one or more of the patient, clinician and doctor to view the UF trend.

As discussed, using trended UF values allows the programmed UF to be withdrawn during the tidal therapy to be predicted quite accurately. The actual patient volume ("IPV") will likewise trend very close to the IPV that the APD cycler <NUM> expects to be in the patient's peritoneum as illustrated in <FIG>. System <NUM> in one embodiment is programmed such that if the UF trend changes by more than a preset percentage, the system alerts the user so that he/she can consult a PD doctor or clinician. System <NUM> in one embodiment automatically adjusts the UF that is programmed for the osmotic agent being used to use the most recent UF trended data point.

Alternatively, the machine alerts the patent to make a change to the programmed UF, so that the user knows of the change. To this end, each osmotic agent or dextrose level dialysate can be associated with a different dialysate ID or number, which the patient enters into the system. System <NUM> then calls up a screen for the particular dialysate, so that the patient can make the machine suggested change. The Trending Application referenced above describes situations in which the patient's doctor or clinician is notified when the patient's UF trends too far away from an expected level for a particular dialysate.

It is important to drain the patient fully at the start of any APD therapy. This holds true for the <NUM>% tidal therapy with UF based upon trending of multiple concentration osmotic agents. In the initial and final drains, however, the patient can be sitting up and will typically drain better, compared with draining when lying down in a supine position. The patient can also move around a little since he/she will be awake and is not inconvenienced when doing so.

System <NUM> in one embodiment knows how much fluid resides in the patient's peritoneum at the start of a therapy. The system remembers the type and volume that it filled the day before for a last fill. System <NUM> in one embodiment trends initial drain volumes and posts an alert if drain flow stops before the normal initial drain volume has been recovered knowing the previous day's last fill volume and dextrose level. System <NUM> can also query the user regarding any day exchange that the patient made the previous day not using machine <NUM> as a possible explanation for an abnormal initial drain.

<FIG> shows an alternative embodiment in which system <NUM> and machine <NUM> continuously remove UF during dwell so that the patient's IPV does not increase over the dwell. Here again, it is important to know the UF accurately for the patient and a particular dextrose level, in order to know how much fluid to remove from the patient over the dwell. The UF volume divided by the dwell time informs system <NUM> and cycler <NUM> of the proper flow rate at which to remove the UF volume from the patient.

While <NUM>% tidal percentage with trended UF provides one very suitable therapy (see predicted results for different patients below), the percentage can be varied if desired or if a different percentage is predicted for a particular patient to have better clearance. For patients that typically drain well, the percentage can be higher, e.g., <NUM>% or <NUM>% and still allow prevent the vast majority of low drain alarms, prevent short fills, and complete therapy on time with the prescribed amount of dwell. Percentages below <NUM>% are also possible.

Simulations were performed on APD Therapies (Tables <NUM> and <NUM>) using PD prediction software called Renalsoft™ , provided by the assignee of the present disclosure. The Trending Application referenced above discusses the prediction software in detail. The simulations were performed to show two different comparisons (i) <NUM>% tidal (using trended UF prediction) versus standard APD Therapy (complete drains, no shorting of fills) and (ii) <NUM>% tidal to simulate CCPD with <NUM>% shorted next fills versus standard APD Therapy (complete drains, no shorting of fills). The software compared the therapies for the three patient body sizes and the four different PET categories, yielding twelve different patient types shown in Table <NUM>.

As seen in Table <NUM>, in all instances, the <NUM>% tidal therapy resulted in higher creatinine clearances when compared to a standard CCPD therapy with full drains and no shorted fills. The results were consistent for both dry days and wet days. As shown, <NUM>% tidal therapy based upon actual patient UF trending with both <NUM>% and <NUM> % dextrose dialysate offer superior clearances. And as discussed herein, <NUM>% tidal therapy is shown to have fewer low drain volume alarms and better control of the volume of fluid in the patient when compared to conventional APD.

An alternative to the <NUM>% tidal therapy is to short a subsequent fill in a CCPD therapy that experiences an incomplete drain when attempting to bring the patient's IPV to zero. The subsequent fill can be shorted by the amount that the previous drain was short. In this manner, system <NUM> limits the amount that the patient can be overfilled to the amount of fluid that has been ultrafiltered from the patient. Assuming, for example, that each drain is <NUM>% short except for the last drain, the resulting change in creatinine clearance is shown in Table <NUM>. For most patients, the clearances are reduced primarily because there is unused fluid left in the supply/heater bags at the end of the therapy. In the example illustrated below, <NUM> out of a total therapy volume of <NUM> (Dry Day) or <NUM> (Wet Day) is not used.

The data in Table <NUM> predicts a reduced creatinine clearance when system <NUM> shorts succeeding fills by the amount that preceding drains fall short of recovering <NUM>% of the previous fill volume. This is to be expected because some of the fresh dialysis solution was not used. Tables <NUM> and <NUM> show that a <NUM>% tidal therapy is at least as effective as a properly performed APD CCPD therapy and does not run the risk of low drain alarms or fill shorts that the APD CCPD therapy runs.

Single lumen patient lines have a recirculation volume (volume of fluid left in the patient line at the end of drain and returned at the start of the next fill) that reduces the therapeutic affect of the therapy. For example, if the internal volume of the patient line 38d (<FIG>) is <NUM> and the fill volume is <NUM>, <NUM>/<NUM>*<NUM>% = <NUM>% of the available fluid is wasted. Patients with larger fill volumes can use longer patient lines 38d without losing a larger percentage of their dialysis fluid. Patients with smaller fill volumes sometimes have to use shorter patient lines 38d with smaller inside diameters to avoid wasting a higher percentage of their dialysis solution.

The <NUM>% tidal therapy discussed herein will drain and fill moving a smaller solution volume when compared to a standard APD therapy. A patient with a <NUM> fill volume on <NUM>% tidal is accordingly wasting the same percentage of dialysis solution as a patient with a <NUM> fill volume on full drain APD.

In one embodiment, system <NUM> addresses the recirculation issue by limiting the length of the standard patient line to about twenty-two feet instead of the thirty-three feet that currently can be used.

Claim 1:
A system (<NUM>) for performing a peritoneal dialysis therapy comprising:
at least one dialysis fluid pump (<NUM>, <NUM>); and
a logic implementer including a central processing unit ("CPU") and a pump controller operable with the CPU, the pump controller operable with the at least one dialysis fluid pump (<NUM>, <NUM>) to perform a plurality of peritoneal dialysis cycles, the cycles including a fill phase, a dwell phase and a drain phase, the logic implementer configured to:
(i) store a continuous cycling peritoneal dialysis ("CCPD") therapy having a total prescribed fresh dialysate fill volume delivered over n cycles during a total therapy duration;
(ii) during the CCPD therapy after at least some dialysis fluid has been pumped by the at least one dialysis fluid pump (<NUM>, <NUM>), determine one of (a) that a next fill phase will cause a patient's intra-peritoneal volume to exceed an allowable volume or (b) that at least one previous drain phase was incomplete; and
(iii) after determining (a) or (b) convert the CCPD therapy into a tidal peritoneal dialysis therapy having at least n+<NUM> cycles and using the total prescribed fresh dialysate fill volume.