SYSTEM AND METHOD FOR MEASURING LIQUID VISCOSITY IN A FLUID DELIVERY SYSTEM

• US 20090113996A1
• Filed: 10/02/2008
• Published: 05/07/2009
• Est. Priority Date: 10/04/2007
• Status: Active Grant

• Current Assignee: Baxter Healthcare SA (Baxter International Inc.), Baxter International Inc.
• Original Assignee: Baxter Healthcare SA (Baxter International Inc.), Baxter International Inc.
• Inventors: DESAI, SIDDHARTH B., WANG, JONG H.
• Granted Patent: US 8,215,157 B2
• Time in Patent Office: Days
• US Class Current: 73/54.430
• CPC Class Codes: A61M 5/1413 Modular systems comprising interconnecting elements
• CPC Class Codes: A61M 5/16813 by controlling the degree of opening of the flow line
• CPC Class Codes: G01N 11/08 by measuring pressure required to produce a known flow

Abstract

The present invention includes systems and methods for determining the viscosity of a fluid within a fluid flow path. Such method may comprise flowing fluid through the fluid flow path and past a fixed flow restriction therein. The method may also comprise first sensing of a fluid pressure within the fluid flow path at a selected location upstream of the flow restriction. The method may also include limiting fluid flow in the fluid flow path upstream of such selected location. The method may further comprise second sensing of a fluid pressure within the fluid flow path at such selected location after such limiting. Such method includes determining the viscosity of the fluid based, at least in part, on any pressure difference from such first and second sensing.

Claims

1. A medical fluid delivery system for determining viscosity of a fluid, the system comprising:

a fluid flow path for communicating between a source and a patient;

a fixed flow restriction in the fluid flow path;

a flow valve operatively associated with the fluid flow path upstream of the fixed flow restriction, such valve being movable between a first position, which allows fluid flow through the path, and a second position, which limits fluid flow through the fluid flow path; and

a control module operatively associated with the fluid flow path for sensing a fluid pressure difference within the fluid flow path at a selected location upstream of the flow restriction when the valve moves from the first position to the second position and for determining viscosity of the fluid based at least in part on such fluid pressure difference.

2. The system of claim 1 wherein the control module is operatively associated with the fluid flow path for determining an actual fluid flow rate in the fluid flow path based, at least in part, on the determined viscosity of the fluid.

3. The system of claim 1 further comprising a flow sensor for sensing the fluid pressure difference.

4. The system of claim 3 wherein the fluid pressure difference is measured between a first sensing at a first time at the selected location and a second sensing at a later second time at the selected location and the control module determines viscosity based, at least in part, on any pressure difference at such selected location that occurs in the time interval between such first and second sensing.

5. The system of claim 1 wherein the flow path has a selected size upstream of the flow restriction and the flow restriction defines a flow path size smaller than the selected size such that the flow restriction defines a reduced flow path area.

6. The system of claim 5 wherein the flow restriction has a known flow area.

7. The system of claim 1 wherein the fluid pressure difference is measured during movement of the valve from the first position to the second position and the second position includes stopping fluid flow through the fluid flow path upstream of such selected location.

8. The system of claim 1 wherein the fluid flow path is defined, at least in part, by tubing and flow through such tubing is limited by applying pressure to the exterior of the tubing to reduce the fluid flow path size.

9. The system of claim 1 further comprising a temperature sensor for sensing the temperature of the fluid.

10. A method for determining the viscosity of a fluid within a fluid flow path, the method comprising:

flowing fluid through the fluid flow path and past a fixed flow restriction therein;

first sensing of a fluid pressure within the fluid flow path at a selected location upstream of the flow restriction;

limiting fluid flow in the fluid flow path upstream of such selected location;

second sensing of a fluid pressure within the fluid flow path at such selected location after such limiting; and

determining the viscosity of the fluid based, at least in part, on any pressure difference from such first and second sensing.

11. The method of claim 10 further comprising determining an actual fluid flow rate in the fluid flow path based, at least in part, on the determined viscosity of the fluid.

12. The method of claim 10 wherein the first sensing occurs at a first time and the second sensing occurs at a later second time and the determining is based, at least in part, on any pressure difference at such selected location that occurs in the time interval between such first and second sensing.

13. The method of claim 10 wherein the determining is based, at least in part, on the rate of pressure change at said selected location between such first and second sensing.

14. The method of claim 10 wherein the flow path has a selected size upstream of the flow restriction and the flow restriction defines a flow path size smaller than the selected size such that the flow restriction defines a reduced flow path area.

15. The method of claim 14 wherein the flow restriction has a known flow area.

16. The method of claim 10 further comprising providing a flow valve operatively associated with the fluid flow path, wherein the limiting includes moving the valve to a position which limits fluid flow through the fluid flow path.

17. The method of claim 10 wherein the limiting includes stopping fluid flow through the fluid flow path upstream of such selected location.

18. The method of claim 10 wherein the fluid flow path is defined, at least in part, by tubing and wherein the limited includes applying pressure to the exterior of the tubing to reduce the fluid flow path size.

19. The method of claim 10 wherein the first and second sensing is performed at known fluid temperatures.

20. The method of claim 10 wherein the determining is based, at least in part, on a time interval between sensing of the pressure before and after such limiting.

21. The method of claim 10 wherein determining is performed automatically without manual input from a user.