Aliquot correction for feeding set degradation
View Patent ↗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 each having an aliquot volume;
a controller programmed to control an electrical signal to the pumping device, the controller including a program comprising a pump set degradation compensator for changing the electrical signal thereby altering operation of the pumping device, the pump set degradation compensator including a volume compensation element that adjusts the aliquot volume solely as a function of time and selected flow rate based at least on the relationship: T*F i (x); where T is a time of pump set use; F i (x) is a pump set flow compensation function based on a user selected flow rate; and x is the user selected flow rate.
2. The pumping apparatus as in claim 1 , wherein T includes time during which fluid is not delivered through the pump set.
3. The pumping apparatus as in claim 1 , wherein T includes time during which a tube section of the pump set is stretched around and operatively coupled to the pumping device.
4. The 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, and wherein the pump set degradation compensator is a software program operating in said memory, the microprocessor being adapted to run the software program.
5. The pumping apparatus as in claim 4 , wherein the memory is selected from a group consisting of: random access memory, flash, EEPROM, PROM, and disk.
6. The pumping apparatus as in claim 4 , wherein the pump set degradation compensator adjusts the aliquot volume based on the equation:
H i (x)=G i (x)+T*F i (x), where G i (x) is an established aliquot volume function based on the user selected flow rate, and H i (x) is a corrected aliquot volume.
7. The pumping apparatus as in claim 6 wherein G i (x) is one of a constant and a polynomial function.
8. The pumping apparatus as in claim 6 , wherein the established aliquot volume function 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 the user selected flow rate x; (ii) a linear function mx+B; and (iii) a nonlinear function Lx 2 +mx+B, wherein L is an empirically established coefficient based on the user selected flow rate x, the values of L for a plurality of flow rates x are stored in the memory, and wherein m is an empirically established coefficient based on the user selected flow rate x.
9. The pumping apparatus as in claim 8 , wherein the constant B is an empirically established constant for the user selected flow rate x or a range thereof, and wherein the lookup table is stored in the memory.
10. The pumping apparatus as in claim 8 further comprising an input device operatively connected to the memory and communicates user inputs for x.
11. The pumping apparatus as in claim 8 , wherein m in the linear function is an empirically established constant for the user selected flow rate x, and wherein the values of m for a plurality of user flow rates x are stored in the memory.
12. The pumping apparatus as in claim 1 , wherein F i (x) is one of a constant and a polynomial function.
13. The pumping apparatus as in claim 12 wherein F i (x) is a linear function Ax+N, where A is a coefficient and N is a constant based on the user selected flow rate x.
14. The pumping apparatus as in claim 1 , wherein F i (x) is 0 if the user selected flow rate is less than or equal to a first predetermined value, F i (x) is Ax+B if the user selected flow rate is greater than the first predetermined value and less than or equal to a second predetermined value, and F i (x) is Lx 2 +mx+B if the user selected flow rate is greater than the second predetermined value, where each of A, L, and m are empirically determined coefficients and B is an empirically determined constant.
15. A method of facilitating delivery of a fluid through a pump set that is operatively coupled to a pumping apparatus having a controller, the method comprising providing a memory device having computer readable instructions stored thereon that are executable by the controller, the instructions providing an aliquot adjustment factor that adjusts a flow rate of the fluid delivered through the pump set solely as a function of time and selected flow rate based at least on the relationship, T*F i (x), where T is an amount of time the pump set is installed in the pumping apparatus, F i (x) is a pump set flow compensation function that is based on a user selected flow rate through the pump set, x is the user selected flow rate through the pump set.
16. The method as in claim 15 , wherein F i (x) is 0 if the user selected flow rate is less than or equal to a first predetermined value, F i (x) is Ax+B if the user selected flow rate is greater than the first predetermined value and less than or equal to a second predetermined value, and F i (x) is Lx 2 +mx+B if the user selected flow rate is greater than the second predetermined value, where each of A, L, and m are empirically determined coefficients and B is an empirically determined constant.
17. A method of delivering fluid using a pumping apparatus that acts on a pump set attached to the pumping apparatus to produce a flow of fluid in aliquots, each aliquot having a volume, the method comprising:
determining an amount of time the pump set is installed in the pumping apparatus;
determining an aliquot volume adjustment factor as a function of a group of variables consisting of time and selected flow rate based at least on the relationship, T*F i (x), where T is the determined amount of time the pump set is installed in the pumping apparatus, F i (x) is a pump set flow compensation function based on a user selected flow rate, and x is the user selected flow rate; and
adjusting a flow rate of the fluid through the pump set with the determined aliquot volume adjustment factor.
18. The method as in claim 17 , wherein the determined amount of time the pump set is installed in the pumping apparatus, T, includes time when fluid is not delivered through the pump set.
19. The method as in claim 18 , further comprising installing the pump set in the pumping apparatus by stretching the pump set.
20. The method as in claim 17 , further comprising calculating the volume of fluid in each aliquot based on the user selected flow rate of fluid to be delivered.
21. The method as in claim 20 wherein adjusting the flow rate comprises adjusting the volume of fluid in each aliquot.
22. The method as in claim 17 , wherein F i (x) is 0 if the user selected flow rate is less than or equal to a first predetermined value, F i (x) is Ax+B if the user selected flow rate is greater than the first predetermined value and less than or equal to a second predetermined value, and F i (x) is Lx 2 +mx+B if the user selected flow rate is greater than the second predetermined value, where each of A, L, and m are empirically determined coefficients and B is an empirically determined constant.
23. The method as in claim 22 , further comprising determining a corrected volume of the fluid in each aliquot according to the following equation:
H i ( x )= G i ( x )+ T*F i ( x ),
where G i (x) is an established aliquot volume function and H i (x) is a corrected aliquot volume.
24. The method as in claim 23 , wherein G i (x) is one of a constant and a polynomial function.