Abstract:
A peritoneal dialysis device displays on a graphical interface a plurality of parameters and any values currently assigned to the parameters, and in response to a user selecting one of the displayed parameters, allows the user to input a value to be assigned to one of the parameters. A value is set for a number of fills parameter or a dwell time parameter based on the value received from the user.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of and claims priority to U.S. application Ser. No. 11/648,154, filed on Dec. 29, 2006, which is incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates to peritoneal dialysis therapy validation. 
       BACKGROUND 
       [0003]    Peritoneal dialysis is a treatment for kidney failure that involves filling a patient&#39;s peritoneal cavity with a dialysis solution that aids in removing waste products from the body and later draining that solution. The filling and draining is handled by a device known as a cycler, such as the Newton™ IQ and the forthcoming Liberty™ Cycler from Fresenius Medical Care N.A. and the HomeChoice™ from Baxter Healthcare. Four types of peritoneal dialysis are discussed in this disclosure: continuous cycling peritoneal dialysis, intermittent peritoneal dialysis, PD plus, and tidal peritoneal dialysis. 
         [0004]    Continuous cycling peritoneal dialysis (CCPD) is a continuous therapy. CCPD is the most common cycling therapy prescribed. With CCPD, the patient has dialysis solution in peritoneum at all times but the exchanges are done only at night by the cycler. Several exchanges are done during sleep. The last thing that the cycler will do is fill for the day. When reconnecting to the cycler, the dialysate that has been dwelling in the patient during the day first has to be drained. 
         [0005]    Intermittent peritoneal dialysis (IPD), as its name suggests, is an interrupted or intermittent therapy. With IPD, the patient will receive exchanges every night from the cycler while sleeping, but will not have any dialysis solution in peritoneum during the day. 
         [0006]    PD plus therapy (PD+) is a continuous therapy in which one or more exchanges are received during the day from the cycler, in addition to the nighttime exchanges. These daytime exchanges are called pause exchanges. With PD plus therapy, the patient carries dialysis solution in peritoneum during the day. This allows for continuous waste product and fluid removal. 
         [0007]    Tidal peritoneal dialysis (Tidal) differs from other dialysis therapies in the way that dialysis solution is delivered during the nighttime. With Tidal the patient is filled with a prescribed amount of solution, then only a portion is drained and refilled with each exchange. Depending on the prescription, the treatment may end with a fill or a drain. 
       SUMMARY 
       [0008]    In general, in one aspect, parameter values are set in a peritoneal dialysis device by receiving from a user a selection of a therapy type, a value for an input parameter is received from the user, and a value is set for a number of fills parameter or a dwell time parameter based on the value received from the user. 
         [0009]    Implementation may include one or more of the following features. Setting a value for the number of fills or dwell time parameter includes calculating a value for the number of fills or dwell time, and assigning the calculated value to the parameter. Setting a value for the number of fills or dwell time parameter includes calculating an updated value for the number of fills or dwell time, determining that the updated value does not meet a criterion, and assigning a value to a third parameter. Calculating an updated value for the number of fills or dwell time based on the value assigned to the third parameter, and assigning the updated value to the number of fills or dwell time parameter. The criterion is that the updated value is within a pre-set range. The criterion is that the updated value has a specified relationship to a fourth parameter. Communicating the value set for the number of fills or dwell time parameter to the user, and communicating to the user a relationship between the value received from the user and the value set for the number of fills or dwell time parameter. 
         [0010]    In general, in one aspect, parameter values are set in a peritoneal dialysis device by receiving from a user a selection of a therapy type, receiving from a user values for a plurality of parameters, calculating a value for a plurality of additional parameters based on the values received from the user, the plurality of additional parameters comprising a number of fills parameter or a dwell time parameter, determining that values for one or more of the plurality of parameters or one or more of the additional parameters do not meet one or more criteria, and updating one or more of the values received from the user so that all of the values for the plurality of parameters and the additional parameters meet all the criteria. 
         [0011]    In general, in one aspect, parameter values are set in a peritoneal dialysis device by displaying on a graphical interface a plurality of parameters and any values currently assigned to the parameters, in response to a user selecting one of the displayed parameters, allowing the user to input a value to be assigned to the parameter, calculating updated values for one or more parameters based on the value input by the user and assigning the updated values to the corresponding parameters, determining whether values assigned to one or more of the parameters meet one or more criteria, and, if the values do not meet the criteria, calculating one or more also updated values for other parameter values that will cause a value that does not meet a criterion to meet the criterion and assigning the also updated values to the corresponding parameters. 
         [0012]    In general, in one aspect, parameter values are set in a peritoneal dialysis device by receiving an instruction from a user to change a value of a parameter to a new value, determining whether the new value is greater than a maximum value for the parameter, if the new value is greater than the maximum value, rejecting the new value, if the new value is less than the maximum value, determining whether the new value is less than a minimum value for the parameter, and if the new value is less than the minimum value, rejecting the new value. 
         [0013]    Implementations may include, calculating an updated value for a second parameter based on the new value if the new value is greater than the minimum value, calculating a total fill volume, determining whether the total fill volume is greater than a total treatment volume, if the total fill volume is greater than the total treatment volume, rejecting the new value, and if the total fill volume is less than the total treatment volume, changing the value of the parameter to the new value. 
         [0014]    In general, in some aspects, a peritoneal dialysis device displays on a graphical interface a plurality of parameters and any values currently assigned to the parameters, and in response to a user selecting one of the displayed parameters, allows the user to input a value to be assigned to one of the parameters. The device calculates updated values for one or more additional parameters based on the value input by the user and assigns the updated values to the corresponding parameters, determines whether values assigned to one or more of the additional parameters meet one or more criteria, and if the values do not meet the criteria, calculates one or more further updated values for other parameter values that will cause a value that does not meet a criterion to meet the criterion and assign the further updated values to the corresponding parameters 
         [0015]    Implementations may include one or more of the following features. The device displays the updated values on the graphical interface. The device determines that values assigned to one or more of the additional parameters do not meet one or more criteria, and informs the user that the input value is rejected. The device performs peritoneal dialysis fills and drains based on the values assigned to the parameters. The device determines that the value input by the user does not meet one or more criteria, and informs the user that the input value is rejected. The graphical interface is part of the peritoneal dialysis device. The graphical interface includes a touch-sensitive display screen. 
         [0016]    Other features and advantages of the invention will be apparent from the description and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0017]      FIGS. 1A  and B are perspective views of a cycler. 
           [0018]      FIG. 2  is a plan view of a cycler cartridge. 
           [0019]      FIG. 3  is a block diagram of a control computer for a cycler. 
           [0020]      FIGS. 4A-F  show user interface screens. 
           [0021]      FIGS. 5A-B  and  6 A-B are flow charts of a parameter update process. 
           [0022]      FIGS. 7A-D  are graphs of dialysis solution amounts. 
           [0023]      FIGS. 8A-B  are tables of validation rules. 
           [0024]      FIG. 9  is a block diagram of validation relationships. 
           [0025]      FIGS. 10A-10D  are flow charts of a validation process. 
           [0026]      FIGS. 11A-11B  are tables of parameter values. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    In current dialysis machines, the therapies are not customized to the specific dialysis type, e.g., CCPD, IPD, PD+, or Tidal. The user creates a therapy scenario himself based on values he chooses for such parameters as the total volume of solution to use, how much to use per fill, or how many pauses to have. Setting large numbers of parameters and keeping track of their interdependencies can be overwhelming. Some of this difficulty can be overcome by providing a user interface that enables a user to select from one of the pre-defined therapy types and then customize it to his prescription, with the system updating dependent and interdependent values as the user changes the ones under his control. 
         [0028]    The following description relates to a prototype of the Liberty™ Cycler shown in more detail in U.S. patent application Ser. No. 11/515,359 filed Aug. 31, 2006, entitled “Improved Cassette System for Peritoneal Dialysis Machine,” which is incorporated here by reference in its entirety. Such a cycler is shown in  FIGS. 1A and 1B . In use, a cycler  10  is connected to a number of bags  12  containing dialysis solution. The cycler  10  has a display screen  14 , buttons  16 , and a cartridge compartment  18 . The display screen  14  may be a touch screen, and is used to present a user interface  100  ( FIGS. 4A-F ). The cartridge compartment  18  accommodates a cartridge  20 , shown in  FIG. 2 , which is connected to a number of tubes  22  which in turn connect to the bags  12 , the patient (not shown), or a drain (not shown). 
         [0029]    The cycler  10  is controlled by a computer  30 , as shown in  FIG. 3 . The computer has a microcontroller  32 , a memory  34 , and an input/output connection  36  to the buttons  16  and display screen  14 . A sensor interface  38  connects the microcontroller to sensors  40 , a pump interface connects the microcontroller to pumps  44 , and a valve interface  46  connects the microcontroller to valves. These three interfaces  38 ,  42 , and  46  allow the computer  30  to operate the cycler  10  according to software and treatment parameters stored in the memory  34 . 
         [0030]    In some examples, as shown in  FIGS. 4A-F , the user interface  100  includes a series of screens that indicate available options. A first “My Settings” screen,  FIG. 4A , is selected by pressing a button  116  and provides a tab  101   a  that allows the user to select which therapy type  102  he requires. In the screen shown, CCPD is selected, as indicated by a highlighted box  104 , and the other available types are indicated by other boxes  106 ,  108 ,  110 ,  112 . Pediatric peritoneal dialysis is beyond the scope of this disclosure. Other buttons  114  and  118  and tabs  101   b - d  allow the user to configure other sets of settings, some of which are discussed below and others of which are beyond the scope of this disclosure. 
         [0031]    When the user chooses the type of therapy, a screen,  FIG. 4B , showing only the parameters corresponding to the selected therapy (CCPD in  FIG. 4B ) is displayed. This screen includes a settings box  120  that makes available the parameters that the user can change for the selected therapy type, in boxes  122   a - d , and additional parameters, in boxes  124   a - b , that are simply calculated from the values the user enters. In  FIG. 4B , the boxes for either direct or calculated parameter entry and display are differentiated based on their shape, but in practice could be differentiated by color, shading, or other standard user-interface features.  FIGS. 4C ,  4 D, and  4 E-F show corresponding screens for IPD, PD+, and Tidal treatment, respectively. As shown in  FIG. 4C , IPD treatment has two additional user-configurable parameters, entered in boxes  122   e - f , but does not have the last fill volume  122   d  of CCPD treatment. In  FIG. 4D , PD+ has both the pause parameters  122   e - f  and the last fill volume  122   d . In  FIG. 4E , Tidal treatment adds a first fill volume,  122   g , and a tidal fill volume  122   h , but does not have a per-fill volume  122   c . Tidal treatment also has a second screen,  FIG. 4F , for entering the tidal drain volume  122   i  and the last fill volume  122   d . In each of the screens, a back button  126  returns the user to the previous screen—the therapy selection screen of  FIG. 4A  for  FIGS. 4B-4E , and the first Tidal screen for  FIG. 4F . In  FIG. 4E , a forward button  128  takes to user to the second Tidal screen of  FIG. 4F . 
         [0032]    When a user changes the value of any one parameter, the other parameters that are affected by it can be seen instantly. All the parameter values on the screen are updated “on the fly.” A comprehensive algorithm can be used to calculate the values as discussed below. This algorithm can be executed in software programmed in the cycler&#39;s memory. Validations can be used to make sure that none of the values are out of range and that all the dependencies are satisfied. For example, when the fill volume  122   c  is changed, the number of fills  124   a  and the dwell time  124   b  update automatically according to the calculations. Validation makes sure that, for example, the last fill volume  122   d  is &lt;=150% of fill volume  122   c  in treatments that have a fill volume setting. When fill volume  122   c  is decreased to a value that violates this condition, last fill volume  122   d  also decreases automatically to ensure that it is always &lt;=150% of fill volume  122   c . In the user interface, when the value of a parameter goes out of range, it can be locked so that the user cannot exceed the limits. For example, the minimum value for total volume  122   a  may be 50 ml. If a user tries to decrease it below 50 ml, then the value locks at 50 ml and allows the user only to increase it and not decrease it. In another example, a check is made to ensure that there is enough sleep time  122   b  for the treatment. If the total sleep time  122   b  is not long enough, then the total therapy volume  122   a  is locked and cannot be increased unless the total therapy time is increased. This may include locking other settings that would increase total volume  122   a , for example, fill volume  122   c . Alternatively, if a user decreases the total sleep time  122   b , the system could automatically reduce the fill volume  122   c  and total volume  122   a  to accommodate the new sleep time. 
         [0033]    This “on the fly” updating gives the user a clear idea of how each parameter value reflects on the others. The user may not be aware of the dependencies but he can still be confident that he is not entering any bad values. 
         [0034]    In some examples, parameters for CCPD, IPD, and PD+ are calculated using the process  200  shown in  FIGS. 5A and 5B . After the therapy type is selected ( 202 ), the remaining volume (the volume that will be used during the regular fills) is calculated ( 204 ) based on user inputs of total volume  206 , last fill volume  208 , the number of pauses  210 , and the pause volume. Since not all therapies have pauses, the calculation  204  could be modified accordingly, or the appropriate inputs may be set to zero when not relevant. 
         [0035]    Next, in step  214 , the remaining volume is divided by the fill volume  216 , and the quotient is added to the number of pauses (if any) to determine the number of fills  217 . In step  218 , the fill volume  216  is divided by the fill rate and drain rate, read from a stored setting  220 , to compute the fill time and drain time respectively. If there are no pauses ( 222 ), then the pause fill time and drain time are set ( 224 ) to zero, otherwise they are computed ( 226 ) by dividing the pause volume  212  by the fill rate and drain rate accordingly. Process  200  continues in  FIG. 5B . 
         [0036]    If there is no last fill ( 230 ) (i.e., the treatment is IPD), the number of dwells is the number of fills minus the number of pauses ( 232 ), the number if drains is one more than the number of fills ( 234 ), the last fill Boolean is zero (false) ( 236 ), and the last fill and first drain times are zero ( 238 ,  240 ). If there is a last fill ( 230 ) (i.e., the treatment is CCPD or PD+), the previously calculated number of fills  217  is incremented ( 242 ), the number of dwells is set to one less than the number of fills minus the number of pauses ( 244 ), the number of drains is set to equal the number or fills ( 246 ), the “last fill” Boolean is one (true) ( 248 ), and the last fill and first drain times are equal to the last fill volume divided by the fill rate and drain rate, respectively ( 250 ,  252 ). 
         [0037]    The time needed for each of the fills and drains is subtracted ( 256 ) from the total sleep time  254 , to find the total dwell time, which is divided ( 258 ) by the number of dwells to find and output the dwell time  260 . 
         [0038]    A similar process  300 , as shown in  FIGS. 6A and 6B , can be used to compute parameters for Tidal therapy. Most of the inputs, steps, and outputs are the same, but a few are modified or reordered, and a few additional inputs and steps are added. The remaining volume calculation  204   b  subtracts the first fill volume  306  from the total volume in addition to the last fill volume and the total pause volume as before. As a preliminary step to calculating the number of fills ( 214 ), the number of tidal fills is calculated ( 302 ) based on the remaining volume and the tidal fill volume  310 . The tidal fill volume  310  and tidal drain volume  312  are used to calculate the fill time and drain time in step  218   b , rather than using a single fill volume for both. An additional step  304  increments the number of fills after the fill time and drain time are calculated, and a first fill time and last drain time are calculated ( 314 ) based on the first fill volume  306 . 
         [0039]    The remaining calculations are the same as in process  200 , with the exception of the calculation  256   b  of total dwell time ( FIG. 6B ), which uses the number of tidal fills to find the fill time and drain time rather than subtracting the number of pauses and last fill from the number of fills and drains, and additionally subtracts the first drain time and first fill time. 
         [0040]    Example parameter calculations for each of the therapy types are described below.  FIG. 7A  shows a graph of the volume of solution in a patient during a CCPD treatment. Upward-sloping segments F 1   a -F 5   a  are fills, horizontal segments DW 1   a -DW 5   a  are dwells, and downward-sloping segments DR 0   a -DR 5   a  are drains, where DR 0   a  is an initial drain to remove any fluid the patient may have from a day time exchange. In a simple example, the user enters the following parameters on box  120  of the screen in  FIG. 4B : total sleep time 90 minutes, total volume 5000 ml, and fill volume 1000 ml, with no last fill or pauses (note these are not the values shown in  FIG. 4B ). Using process  200 , the remaining volume is calculated in step  204  as 5000 ml−0−(0×0)=5000 ml. This is divided in step  214  by fill volume, 1000 ml, giving number of fills  217 =5. If the fill rate is 300 ml/min and the drain rate is 200 ml/min, step  218  gives a fill time of 4 minutes (rounding up to whole minutes) and a drain time of 5 minutes. The number of pauses is zero ( 222 ) so the pause fill and drain times are zero ( 224 ). Because there is no last fill, decision  230  directs the process  200  to the left-hand branch in  FIG. 5B . The number of dwells equals the number of fills, 5 (minus zero), in step  232 , and the number of drains is therefore set to 6 in step  234 , to account for the DR 0   a  drain. The last fill is false (zero), and last fill and first drain times are zero (if a first drain is necessary, it is not counted in the total dwell time of the treatment). This gives a total dwell time of 90−5×4−6×5=40 min in step  256  and a dwell time  260  of 8 min when that is divided over the 5 dwells in step  258 . 
         [0041]      FIG. 7B  shows a graph of the volume of solution in a patient during an IPD treatment including a pause but no final fill. Fills F 1   b -F 5   b , drains DR 1   b -DR 5   b , and dwells DW 1   b -DW 4   b  are as in  FIG. 7A , and segment P 1   b  represents the pause. The difference between the pause and the dwells, as far as the calculations are concerned, is that it doesn&#39;t count toward the total dwell time. Modifying the CCPD example above, the pause fill volume is set to 500 ml, and the number of pauses is set to 1. This gives a remaining volume of 4500 in step  204  and a number of fills of 4500/1000+1=5.5 in step  214 . The partial fill is dropped, giving 5 fills for the remaining calculations (see the discussion of parameter validation, below). The fill time is the same as above, and the pause fill and drain times are 500/300=2 minutes and 500/200=3 min (rounding up) per step  226 . Again following the left branch in  FIG. 2B , the number of dwells is 5−1=4, and the number of drains in 5+1=6. The total dwell time is 90−(5−1)×4−(6−1)×5−1×2−1×3=44 min, giving a dwell time  260  of 11 min. 
         [0042]      FIG. 7C  shows a graph of the volume of solution in a patient during an PD+ treatment including both a pause and a final fill. The notations follow the same pattern as in the above examples. For this example, the sleep time, total volume, and fill volume remain the same, but pause volume is set to 600 ml and the last fill volume is 1200 ml. Again using process  200 , this gives a remaining volume of 3200 ml (step  204 ) and 3200/1000+1=4 fills  217  at step  214 . Fill time and drain time are again 4 min and 5 min (step  218 ), and pause fill and drain time are again 2 min and 3 min (this time without rounding). Now following the right-hand branch in  FIG. 5B , the number of fills  217  is incremented to 5 (step  242 ) to account for the last fill. The number of dwells is 6−1−1=3, per step  244 , and the number of drains is 5. The last fill is set true (one—step  248 ), the last fill time is 1200/300=4 min ( 250 ), and the first drain time is 1200/200=6 min ( 252 ). These values give a total dwell time of 90−(5−1−1)×4−(5−1−1)×5−1×2−1×3−4−6=48 min ( 256 ) and a dwell time  260  of 48/3=16 min ( 258 ). 
         [0043]    An example tidal treatment is shown in  FIG. 7D . The notations are as above, but note that the downward-sloping drain segments DR 1   d -DR 3   d  and upward-sloping fill segments F 2   d -F 4   d  don&#39;t reach zero between dwells. For this example, total sleep time and total volume are as above. Tidal fill volume is set to 900 ml, with tidal drain volume set to 950 ml. The first fill volume is 1000 ml and the last fill volume is 500 ml. Applying process  300 , the remaining volume is 5000−500−1000−0×0=3500 ml ( 204   b ) giving a number of tidal fills of 3500/900=3 in step  302 . Tidal fill time is 900/300=3 min, while tidal drain time is 950/200=5 min ( 218   b ). The number of fills  217  is incremented by 1 to account for the tidal fill F 1   d  in step  304 . The first fill and last drain times are calculated in step  314  as 1000/300=4 min and 1000/200=5 min, respectively. Following the right-hand branch in  FIG. 6B , the number of fills  217  is incremented again to account for the last fill ( 242 ). The number of dwells is 5−0−1=4 ( 244 ) and the number of drains is 5 ( 246 ). The last fill Boolean is set to true (one, step  248 ), and the last fill and first drain times are calculated as 500/300=2 min ( 250 ) and 500/200=3 min ( 252 ), respectively. This all amounts to a total dwell time of 90−3×3−3×5−0−0−2−3−4−5=52 min ( 256 ) and a dwell time  260  of 52/4=13 min ( 258 ). 
         [0044]    In addition to calculating the number of fills and the dwell time, the system is able to evaluate the validity of each of the input parameters whenever one of them is changed, as mentioned above. A validation table  500  in  FIG. 8A  lists several parameter validation relationships. Additional or alternative validations for tidal therapy are shown in  FIG. 8B . The validation relationships between values in tables  500  and  550  are shown graphically in  FIG. 9 . In  FIG. 9 , user inputs are shown in rounded boxes, and internally computed values are shown in rectangles. Arrows indicate dependency. Elements shown without any arrows into them, e.g., fill time  516  and drain time  518 , depend on fixed validation values but not on other input or computed values. Elements that do have arrows in to them may depend on other values, fixed values, or both, as indicated in the validation table  500 . 
         [0045]    In the example shown, the last fill volume  508  depends on the fill volume  506  according to rule  11  in table  500 , that is, last fill volume  508  must be less than 150% of fill volume  506 . Similarly, the pause volume  510  must be less than 150% of fill volume  506  according to rule  12 . Pause volume is also validated against the number of pauses  512 , as pause volume can only have non-zero values when the number of pauses  512  is also non-zero. The number of pauses  512  in turn is validated against the number of fills  520 , as its maximum value is one less than the number of fills  520  according to rule  10 . The total volume  504  must be less than the total fill volume  524  per rule  13 . The total fill volume  524  is not used in the process  200 , but is used to validate the total volume input. It is calculated from the fill volume  506 , last fill volume  508 , pause volume  510 , and number of pauses  512  and fills  520  according to rules  13   a, b , and  c , depending on whether last fill or pauses are enabled (i.e., last fill volume&gt;0 or number of pauses&gt;0). The dwell time  514  depends on the fill time  516  and number of dwells  522  according to rule  2 . Each of the parameters in  FIG. 9  is also validated against numerical limits per the other rules in table  500 . 
         [0046]    Applying these tables  500  and  550  to the example tidal therapy calculation above, the total sleep time, total volume, last fill volume, pause volume, and number of fills are all within the fixed numeric ranges of rules  1 ,  5 ,  7 ,  8 , and  9 . The dwell time is greater than the fill time per rule  2 . As for the tidal-specific parameters, the first fill volume, tidal fill volume, tidal drain volume, and number of pauses are all within the ranges of tidal rules  1 - 4 . (The number of pauses also meets the general rule  10  in table  500  as it is zero.) The total volume meets tidal rule  5 - a , having a last fill but no pauses, as the total fill volume is 3×900+1000+500=3300 ml, and this is less than the total volume of 5000 ml. 
         [0047]    In some examples, a process shown in  FIGS. 10A-10D  is used to validate parameters as they are entered and assure that they fall within valid ranges. A process  600  in  FIGS. 10A and 10B  is used for CCPD, IPD, and PD+ treatments, while a process  700  in  FIGS. 10C and 10D  is used for Tidal treatment. The process  600  is entered when the user selects  602  one of CCPD, IPD, or PD+ treatments and changes  604  the value of any parameter. The process then checks  606  whether the new value is greater than a set maximum value. If it is, the change is not allowed ( 608 ). If the new value is less than the maximum, then the process checks  610  whether it is less than a minimum value. Again, if the new value is too low, the change is not allowed ( 608 ). A list of minimum and maximum values that may be used by the process  600 , based on the rules in table  500  ( FIG. 8A ), are shown in table  650  in  FIG. 11A . 
         [0048]    If the new value is between the minimum and maximum values, then the process  600  calculates  612  all the other parameters based on that new value, using the process  200  ( FIGS. 5A &amp; 5B ) discussed above. If only a last fill is enabled ( 614 ), the process  600  calculates  616  the total fill volume based on the number of fills, the fill volume, and the last fill volume. If only a pause is enabled ( 618 ), the fill volume is calculated  620  based on the number of fills, number of pauses, fill volume, and pause volume. In either case, the process  600  proceeds (link D) to step  630  discussed below. If both conditions  614  and  618  are not true, the process  600  proceeds (link C) to step  622 . If both last fill and pause are enabled, the total fill volume is calculated  624  based on the number of fills and pauses, the fill volume and pause volume, and the last fill volume. If neither last fill nor pause are enabled ( 626 ), then the total fill volume is calculated  628  based only on the number of fills and the fill volume. After the total fill volume is calculated in steps  616 ,  620 ,  624 , or  628 , it is compared  630  to the total volume entered by the user. If the total fill volume would be larger than the total volume, the change is not allowed ( 632 ). If the total fill volume is less than the total volume, the value is changed ( 634 ). The process  700  is essentially the same, with steps  616 ,  620 ,  624 , and  628  replaced by steps  702 ,  704 ,  706 , and  708  to calculate the total fill volume based on the number of tidal fills, tidal fill volume, and first fill volume. Minimum and maximum values for use by process  700  are shown in table  750   a  and  750   b  in  FIG. 11B . 
         [0049]    Other implementations are within the scope of the following claims and other claims to which the applicant may be entitled.