Tube measurement technique using linear actuator and pressure sensor

• US 8,567,235 B2
• Filed: 06/29/2010
• Issued: 10/29/2013
• Est. Priority Date: 06/29/2010
• 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: Bojan, Peter M., Wang, Zhengyan, Rai, Surya, Olczak, Paul
• Primary Examiner(s): Williams, Hezron E
• Assistant Examiner(s): Frank, Rodney T
• Application Number:
  US12/826,192
• Publication Number:
  US 20110319823A1
• Time in Patent Office: 1,218 Days
• Field of Search: 73/37
• US Class Current: 73/37
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 5/142 Pressure infusion, e.g. using pumps
• CPC Class Codes: A61M 5/14212 Pumping with an aspiration and an expulsion action
• CPC Class Codes: G01B 3/205 provided with a counter for digital indication of the measured dimension
• CPC Class Codes: G01B 5/06 for measuring thickness

Abstract

An infusion pump uses sensors, movable members and a control unit to determine tubing thickness in a tube-loading section of the pump. The infusion pump utilizes sensors, such as a pressure sensor, to record forces imparted by a tube undergoing no pressure, a single pressure, or a pressure sweep, to determine thickness. Using these values, the tubing wall thickness can be determined. The infusion pump can also compress a tube using a movable member of the pump and records the distance traveled by the movable member to compress fully the tube. Using this distance, the tubing wall thickness can be determined.

Claims

1. A method of measuring tube wall thickness, the method comprising:

loading a tube between a stationary member and a movable member;

compressing the tube between the stationary member and the movable member;

receiving a signal indicative of an amount of compression of the tube while compressing the tube;

determining from the signal that the tube is fully compressed and stopping the compressing of the tube once the tube is fully compressed; and

determining a thickness of the tube wall based on the signal received indicating full compression.

2. The method of claim 1, wherein the stationary member and the movable member are part of an infusion pump.

3. The method of claim 1, wherein receiving the signal includes counting encoder pulses.

4. The method of claim 3, wherein determining that the tube is fully compressed includes determining that no new encoder pulses are being generated.

5. The method of claim 3, wherein determining that the tube is fully compressed includes determining a rate at which new encoder pulses have lessened.

6. The method of claim 1, wherein compressing the tube includes providing a constant current to a motor sufficient to allow the tube to be fully compressed without elastically compressing the tube.

7. The method of claim 1, wherein receiving the signal includes receiving a current draw signal and determining that the tubing is fully compressed includes sensing a current rise.

8. The method of claim 1, further comprising setting at least one infusion pump parameter based upon the determined tube thickness.

9. A method of measuring tube wall thickness, the method comprising:

providing a fixture having a loading portion and a pressure sensor, the pressure sensor located on a wall of the loading portion;

loading a tube into the loading portion such that the tube imparts a force on the pressure sensor that contacts an outside wall of the tube;

recording the force imparted on the pressure sensor by the outside wall of the tube; and

determining the thickness of the tube wall based on the force imparted by the tube on the pressure sensor.

10. The method of claim 9, wherein the step of determining the thickness of the tube includes comparing the force imparted by the tube with a plurality of force values, each force value corresponding to a specific tube having a predetermined thickness.

11. The method of claim 9, wherein the thickness of the tube is determined as a relative thickness selected from the group consisting of low tube thickness, moderate tube thickness and high tube thickness.

12. The method of claim 9, wherein the fixture is an infusion pump.

13. The method of claim 9, further comprising applying a positive pressure to the interior of the tube.

14. A method of measuring tube wall thickness, the method comprising:

providing a fixture having a loading portion and a sensor, the sensor located on a wall of the loading portion;

loading a tube into the loading portion, wherein the sensor contacts an outside wall of the tube;

applying a pressure sweep to the interior of the tube,

wherein the pressure sweep starts at a minimum value and ends at a maximum value;

recording a plurality of output values from the sensor, each output value recorded at step-wise increments during the pressure sweep; and

determining the thickness of the tube wall based on the output values recorded during the pressure sweep.

15. The method of claim 14, the method further comprising closing both ends of the tube before applying the pressure sweep to the tube.

16. The method of claim 14, wherein the minimum value is zero psig.

17. The method of claim 14, wherein the maximum value is 25 psig.

18. The method of claim 14, wherein the step-wise increments are at every one psig during the pressure sweep.

19. The method of claim 14, wherein the fixture is an infusion pump.

20. The method of claim 14, wherein the step of determining the thickness of the tube comprises:

plotting the plurality of output values along the pressure sweep to produce a sensor plot for the tube; and

comparing the sensor plot with a plurality of predetermined sensor plots, each predetermined sensor plot corresponding to a specific tube having a predetermined thickness.

21. A method of measuring tube wall thickness, the method comprising:

loading a tube between a stationary member and a movable member;

compressing the tube between the stationary member and the movable member;

receiving a signal indicative of an amount of compression of the tube while compressing the tube;

determining from the signal that the tube is fully compressed and stopping the compressing of the tube once the tube is fully compressed; and

determining a thickness of the tube wall based on the signal received indicating full compression, wherein receiving the signal includes receiving a current draw signal and determining that the tubing is fully compressed includes sensing a current rise.