Aliquot correction for feeding set degradation

Abstract

A peristaltic pump is able to deliver accurate volumes over the life of a pump set that is operated on by the pump to drive the flow of fluid. The pump delivers fluid in small volumes or aliquots. In order to deliver fluid at any particular selected flow rate, the pump determines how often the rotor will rotate. The pump is able to calculate aliquot volume based on selected flow rate, but also on a factor that compensates for changes in the dimensions of the pump set over its life.

1 . A pumping apparatus for use with a pump set to deliver fluid through the pump set, the pumping apparatus comprising:
 a pumping device capable of acting on the pump set to produce a fluid flow within the pump set, the pumping device producing said fluid flow in a series of aliquots;   a housing capable of receiving at least a portion of the pump set to be acted upon by the pumping device;   a controller programmed to control an electrical signal to the pumping device, the controller including a pump set degradation compensator for changing the electrical signal thereby altering operation of the pumping device whereby the fluid flow rate delivered by the pumping apparatus is more accurate over the useful life of the pump set, the pump set degradation compensator including a volume compensation element which is a function of the entire time the pump set has been in use on the pumping device.   
   
   
       2 . A pumping apparatus as in  claim 1  further comprising an actuator having at least one pump set engaging member for engaging the pump set to force fluid to flow in the pump set. 
   
   
       3 . A pumping apparatus as in  claim 2  wherein the actuator comprises a rotor adapted to receive a portion of the pump set into engagement with the rotor. 
   
   
       4 . A pumping apparatus as in  claim 3 , wherein there are plural engaging members, each engaging member comprising a roller for engaging the pump set and generating an aliquot of fluid flow. 
   
   
       5 . A pumping apparatus as in  claim 1 , wherein the controller includes a memory and a microprocessor in communication with the memory, wherein said memory contains the pump set degradation compensator. 
   
   
       6 . A pumping apparatus as in  claim 5 , wherein the memory is selected from a group consisting of: random access memory, flash, EEPROM, PROM, or disk. 
   
   
       7 . A pumping apparatus as in  claim 5 , wherein the pump set degradation compensator is a software program operating in said memory, the microprocessor being adapted to run the software program. 
   
   
       8 . A pumping apparatus as in  claim 7 , wherein the pump set degradation compensator corrects the aliquot volume as a function of feed rate selected and time of use of the pump set; the pump set degradation compensator is an equation stored in the memory of the controller; the equation is H i (x)=G i (x)+T*F i (x) where G i (x) is the established aliquot volume as a function of flow rate selected; T is time of pump set use; F i (x) is pump set flow compensation of volume as a function of flow rate selected; x is a user selected flow rate and H i (x) is the corrected aliquot volume as a function of flow rate selected and time of use of the pump set. 
   
   
       9 . A pumping apparatus as in  claim 8  wherein G i (x) is one of a constant and a polynomial equation. 
   
   
       10 . A pumping apparatus as in  claim 8 , wherein the established aliquot volume G i (x) is at least one of: (i) a constant, the constant being B and stored in a lookup table; the table being indexed by user selected flow rate x; (ii) a linear function mx+B of the user selected flow rate; and (iii) a nonlinear equation Lx 2 +mx+B, wherein L is an empirically established constant for a user selected flow rate x, the value of L for a plural of flow rate x are stored in a table in the memory. 
   
   
       11 . A pumping apparatus as in  claim 10 , wherein the constant B is an empirically established constant for the user selected flow rate x or a range thereof and stored in a table in the memory. 
   
   
       12 . A pumping apparatus as in  claim 10  further comprising an input device operatively connected to the memory communicates user inputs for x. 
   
   
       13 . A pumping apparatus as in  claim 10 , wherein m in the linear function is an empirically established constant for a user selected flow rate x; the values of m for a plurality of user flow rates x are stored in a table in the memory. 
   
   
       14 . A pumping apparatus as in  claim 8  wherein F i (x) is one of a constant and a polynomial. 
   
   
       15 . A pumping apparatus as in  claim 14  wherein the F i (x) is a linear function Ax+N, where A is a coefficient and N is a constant selected from the memory based on the flow rate x selected by a user. 
   
   
       16 . A pumping apparatus as in  claim 1  in combination with the pump set, and wherein the pump set is disposable. 
   
   
       17 . A pumping apparatus as in  claim 1  in combination with the pump set, wherein the pump set includes at least two tube sections. 
   
   
       18 . A method of delivering accurate flow rates of fluid using a pumping apparatus that acts on a pump set attached to the pumping apparatus to produce flow of fluid in aliquots, the method comprising:
 determining the amount of time the pump set has been in use in the pumping apparatus;   calculating the volume of fluid in each aliquot delivered by the pumping apparatus including executing instructions that are capable of correcting the aliquot volume based on the amount of time the pump set has been in use in the pumping apparatus, wherein said calculating the volume of the fluid in each aliquot is calculated as a function of the time the pump set has been in use;   operating the pumping apparatus to deliver a number of aliquots having the aliquot volume determined in the preceding step to maintain a selected flow rate.   
   
   
       19 . A method as in  claim 18  further comprising inputting the flow rate of fluid to be delivered into memory associated with the pumping apparatus. 
   
   
       20 . A method as in  claim 19  wherein calculating the volume of fluid in each aliquot is further based on the selected flow rate inputted into the pumping apparatus memory. 
   
   
       21 . A method as in  claim 20  wherein calculating the volume of fluid in each aliquot comprises establishing a range in which the selected flow rate lies. 
   
   
       22 . A method as in  claim 21  wherein calculating the volume of fluid in each aliquot further comprises using an equation corresponding to the selected flow rate range to calculate a volume correction factor based on the selected flow rate and multiplying the correction factor by the amount of time the pump set has been in use. 
   
   
       23 . A method as in  claim 22  wherein the step of calculating the volume of the fluid in each aliquot is determined according to the following equation:
     H   i ( x )= G   i ( x )+ T*F   i ( x )   
     where G i (x) is the established volume as a function of flow rate selected; T is the amount of time of pump set use; F i (x) is pump set flow compensation of volume as a function of flow rate selected; x is flow rate and H i (x) is the corrected aliquot volume as a function of flow rate selected and time. 
   
   
       24 . A method as in  claim 23  wherein G i (x) is one of a constant and a polynomial. 
   
   
       25 . A method as in  claim 24  wherein G i (x) is at least one of: (i) a linear function of selected flow rate G i (x)=mx+B, where m is a coefficient and B is a constant; (ii) a constant B; and (iii) a nonlinear function of selected flow rate G i (x)=Lx 2 +mx+B, where L and m are coefficients corresponding to particular selected flow rate and stored in memory and B is a constant corresponding to a particular flow rate and stored in memory. 
   
   
       26 . A method as in  claim 23  wherein F i (x) is one of a constant and a polynomial. 
   
   
       27 . A method as in  claim 26  wherein F i (x) is a linear function F i (x)=Ax+N, where A is a coefficient and N is a constant selected from the memory based on the flow rate x selected by a user. 
   
   
       28 . A method as in  claim 18  wherein one or more computer-readable media have computer executable instructions for performing the method of  claim 18 .