Pressure detector for fluid circuits

• US 7,337,674 B2
• Filed: 06/29/2005
• Issued: 03/04/2008
• Est. Priority Date: 06/29/2005
• Status: Active Grant

• Current Assignee: Nxstage Medical Incorporated (Fresenius SE & Co. KGaA)
• Original Assignee: Nxstage Medical Incorporated (Fresenius SE & Co. KGaA)
• Inventors: Brugger, James M., Treu, Dennis M., Burbank, Jeffrey H., McDowell, Christopher
• Primary Examiner(s): Lefkowitz; Edward
• Assistant Examiner(s): Kirkland, III; Freddie
• Application Number:
  US11/160,586
• Publication Number:
  US 20070000333A1
• Time in Patent Office: 979 Days
• Field of Search: 737/14, 737/23, 737/25, 737/26, 737/27, 738/620.41, 600/562, 600/573, 600/584, 604/131, 604/207
• US Class Current: 73/714
• CPC Class Codes: A61M 1/36222 Details related to the interface between cassette and machine
• CPC Class Codes: A61M 1/362227 the interface providing means for actuating on functional elements of the cassette, e.g. plungers
• CPC Class Codes: A61M 1/36224 with sensing means or components thereof
• CPC Class Codes: A61M 1/3639 Blood pressure control, pressure transducers specially adapted therefor
• CPC Class Codes: G01L 7/024 with mechanical transmitting or indicating means G01L7/043, G01L7/063, G01L7/084, G01L7/104, G01L7/166, G01L7/185 take precedence

Abstract

A pressure measurement device usable for monitoring pressure of fluids such as blood, waste, and replacement fluid in a blood treatment system provides a reliable signal and other benefits by virtue of a number of features of the various embodiments disclosed. The pressure of fluid carried by a vessel or tube is measured by measuring a change in shape of the vessel or tube via a sensor element contacting it. Materials, shape, and mechanical support cooperatively ensure that the little inelastic strain occurs and pressure measurements are repeatable. The embodiments are compatible with the use of disposable vessels and tubes.

Claims

1. A pressure measurement device, comprising:

a fluid circuit for conducting a fluid in support of renal replacement therapy;

said fluid circuit having a tubular part with a sensor portion;

a mechanism adjacent said sensor portion configured to detecting pressure from said sensor portion responsive to changes in pressure of a fluid within an interior thereof;

said sensor portion having a non-circular cross-section, at least said sensor portion being configured such that it suffers substantially no non-elastic tensile strain in a wall thereof as a result of a change in pressure within whereby hysteresis in a signal from said sensor element is avoided.

2. A device as in claim 1, wherein said mechanism includes a first support positioned to support a fixed portion of said sensor portion.

3. A device as in claim 1, wherein said mechanism includes a first support with a fixed surface positioned to support a fixed portion of said sensor portion and a displacement sensor to detect deformation of a non-fixed portion of said sensor portion by detecting displacement thereof.

4. A device as in claim 3, wherein said displacement sensor includes a movable element with a movable surface substantially coplanar with said fixed surface.

5. A device as in claim 4, wherein said fixed and movable surfaces engage said sensor portion to preload said sensor portion such that said sensor portion remains open, whereby said non-fixed portion is displaced by changes in pressure of said interior in a negative range of gage pressures.

6. A device as in claim 5, wherein a load generated by preloading is borne at least in part by a spring.

7. A device as in claim 1, wherein said sensor portion is a flattened portion of said tubular part.

8. A device as in claim 7, wherein said mechanism includes a first support positioned to support a fixed portion of said sensor portion.

9. A device as in claim 7, wherein said mechanism includes a first support with a fixed surface positioned to support a fixed portion of said sensor portion and a displacement sensor to detect deformation of a non-fixed portion of said sensor portion by detecting displacement thereof.

10. A device as in claim 9, wherein said displacement sensor includes a movable element with a movable surface substantially coplanar with said fixed surface.