Method and apparatus for detecting errors, fluid pressure, and occlusions in an ambulatory infusion pump

• US 20040085215A1
• Filed: 10/22/2003
• Published: 05/06/2004
• Est. Priority Date: 10/29/1998
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Moberg, Sheldon B., Hanson, Ian B.
• Granted Patent: US 7,193,521 B2
• Time in Patent Office: Days
• US Class Current: 340/679
• CPC Class Codes: A61M 2005/1623 Details of air intake
• CPC Class Codes: A61M 2005/16863 Occlusion detection
• CPC Class Codes: A61M 2205/332 Force measuring means
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 2205/581 by audible feedback
• CPC Class Codes: A61M 2205/582 by tactile feedback
• CPC Class Codes: A61M 39/10 Tube connectors; Tube couplings A61M39/02 takes precedence; connecting needles to syringes or hubs A61M5/34; connecting catheter tubes to hubs A61M25/0014
• CPC Class Codes: A61M 39/12 for joining a flexible tube to a rigid attachment
• CPC Class Codes: A61M 39/14 for connecting tubes having sealed ends needle sets A61M5/162; having valves closing automatically on disconnection of line A61M39/26
• CPC Class Codes: A61M 5/1452 pressurised by means of pistons
• CPC Class Codes: A61M 5/1456 with a replaceable reservoir comprising a piston rod to be moved into the reservoir, e.g. the piston rod is part of the removable reservoir
• CPC Class Codes: A61M 5/14566 with a replaceable reservoir for receiving a piston rod of the pump
• CPC Class Codes: A61M 5/162 Needle sets, i.e. connections by puncture between reservoir and tube ; Connections between reservoir and tube in jet-action syringes A61M5/30; connectors for tubes having sealed ends and a needle for piercing them A61M39/14
• CPC Class Codes: A61M 5/16831 Monitoring, detecting, signalling or eliminating infusion flow anomalies low-level float-valves causing cut-off A61M5/40; indicating or recording presence, absence or direction of flow in general G01P13/0066
• CPC Class Codes: A61M 5/16854 by monitoring line pressure

Abstract

An improved pump, reservoir and reservoir piston are provided for controlled delivery of fluids. A motor is operably coupled to a drive member, such as a drive screw, which is adapted to advance a plunger slide in response to operation of the motor. The plunger slide is removably coupled to the piston. A method, system, and an article of manufacture for automatically detecting a force sensor failure in a medication infusion pump is provided. The electrical current to an infusion pump is measured. Based on the current measurements, the infusion pump detects when the plunger slide is seated in the reservoir, and detects a problem with the force sensor when the force sensor independently fails to register a value indicating that the plunger slide is seated in the reservoir.

Claims

1. A method of detecting a malfunction with a force sensor in an infusion pump having a motor to drive a plunger slide into a reservoir, the method comprising:

taking current measurements to the motor;

detecting when the plunger slide is seated in the reservoir based on the current measurements; and

detecting a problem with the force sensor when the force sensor independently fails to register a value indicating that the plunger slide is seated in the reservoir.

2. The method of claim 1 further comprising:

measuring movement of the plunger slide by an encoder as encoder counts; and

using the encoder counts to confirm that the current measurements are correctly detecting movement of the plunger slide.

3. The method of claim 1 further comprising:

measuring movement of the plunger slide by an encoder as encoder counts; and

signaling an error with the force sensor when the force sensor independently fails to recognize that the plunger slide is seated in the reservoir after a preset encoder count threshold is exceeded.

4. The method of claim 1 further comprising:

measuring the time since the plunger slide was seated in the reservoir as indicated by the current measurements; and

signaling an error with the force sensor when the force sensor independently fails to recognize that the plunger slide is seated in the reservoir after a preset time threshold is exceeded.

5. The method of claim 1, wherein the step of detecting when the plunger slide is seated in the reservoir is comprised of:

calculating an average current based on the current measurements;

comparing the average current to a threshold current; and

detecting when the plunger slide is seated in the reservoir when the average current exceeds the threshold current.

6. The method of claim 5, wherein the step of calculating an average current uses the latest five current measurements.

7. The method of claim 5, wherein the step of calculating an average current discards a high current measurement and a low current measurement.

8. The method of claim 1, wherein the step of detecting a problem with the force sensor indicates the force sensor has failed.

9. The method of claim 1, wherein the step of detecting a problem with the force sensor indicates the force sensor is marginal.

10. The method of claim 1, wherein the current measurements to the motor are taken every 70 milliseconds.

11. A system of detecting a malfunction with a force sensor in an infusion pump having a motor to drive a plunger slide into a reservoir, the method comprising:

means for taking current measurements to the motor;

means for detecting when the plunger slide is seated in the reservoir based on the current measurements; and

means for detecting a problem with the force sensor when the force sensor independently fails to register a value indicating that the plunger slide is seated in the reservoir.

12. The system of claim 11 further comprising:

means for measuring movement of the plunger slide by an encoder as encoder counts; and

means for using the encoder counts to confirm that the current measurements are correctly detecting movement of the plunger slide.

13. The system of claim 11 further comprising:

means for measuring movement of the plunger slide by an encoder as encoder counts; and

means for signaling an error with the force sensor when the force sensor independently fails to recognize that the plunger slide is seated in the reservoir after a preset encoder count threshold is exceeded.

14. The system of claim 11 further comprising:

means for measuring the time since the plunger slide was seated in the reservoir as indicated by the current measurements; and

means for signaling an error with the force sensor when the force sensor independently fails to recognize that the plunger slide is seated in the reservoir after a preset time threshold is exceeded.

15. The system of claim 11, wherein the step of detecting when the plunger slide is seated in the reservoir is comprised of:

means for calculating an average current based on the current measurements;

means for comparing the average current to a threshold current; and

means for detecting when the plunger slide is seated in the reservoir when the average current exceeds the threshold current.

16. The system of claim 15, wherein the step of calculating an average current uses the latest five current measurements.

17. The system of claim 15, wherein the step of calculating an average current discards a high current measurement and a low current measurement.

18. The system of claim 11, wherein the step of detecting a problem with the force sensor indicates the force sensor has failed.

19. The system of claim 11, wherein the step of detecting a problem with the force sensor indicates the force sensor is marginal.

20. The system of claim 11, wherein the current measurements to the motor are taken every 70 milliseconds.

21. An article of manufacture containing code for detecting a malfunction with a force sensor in an infusion pump having a motor to drive a plunger slide into a reservoir, comprising a computer usable media including at least one embedded computer program that is capable of causing at least one computer to perform:

taking current measurements to the motor;

detecting when the plunger slide is seated in the reservoir based on the current measurements; and

detecting a problem with the force sensor when the force sensor independently fails to register a value indicating that the plunger slide is seated in the reservoir.

22. The article of manufacture of claim 21 further comprising:

measuring movement of the plunger slide by an encoder as encoder counts; and

using the encoder counts to confirm that the current measurements are correctly detecting movement of the plunger slide.

23. The article of manufacture of claim 21 further comprising:

measuring movement of the plunger slide by an encoder as encoder counts; and

signaling an error with the force sensor when the force sensor independently fails to recognize that the plunger slide is seated in the reservoir after a preset encoder count threshold is exceeded.

24. The article of manufacture of claim 21 further comprising:

measuring the time since the plunger slide was seated in the reservoir as indicated by the current measurements; and

signaling an error with the force sensor when the force sensor independently fails to recognize that the plunger slide is seated in the reservoir after a preset time threshold is exceeded.

25. The article of manufacture of claim 21, wherein the step of detecting when the plunger slide is seated in the reservoir is comprised of:

calculating an average current based on the current measurements;

comparing the average current to a threshold current; and

detecting when the plunger slide is seated in the reservoir when the average current exceeds the threshold current.

26. The article of manufacture of claim 25, wherein the step of calculating an average current uses the latest five current measurements.

27. The article of manufacture of claim 25, wherein the step of calculating an average current discards a high current measurement and a low current measurement.

28. The article of manufacture of claim 21, wherein the step of detecting a problem with the force sensor indicates the force sensor has failed.

29. The article of manufacture of claim 21, wherein the step of detecting a problem with the force sensor indicates the force sensor is marginal.

30. The article of manufacture of claim 21, wherein the current measurements to the motor are taken every 70 milliseconds.

31. A method of using current measurements to a motor in an infusion pump to detect when a plunger slide is seated in a reservoir, the method comprising:

taking current measurements to the motor;

calculating an average current based on the current measurements;

comparing the average current to a threshold current; and

detecting when the plunger slide is seated in the reservoir when the average current exceeds the threshold current.