Pressure based refill status monitor for implantable pumps

• US 9,421,325 B2
• Filed: 11/16/2009
• Issued: 08/23/2016
• Est. Priority Date: 11/20/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Kalpin, Scott L.
• Primary Examiner(s): Mehta, Bhisma
• Assistant Examiner(s): Zhang, Jenna
• Application Number:
  US12/619,145
• Publication Number:
  US 20100125246A1
• Time in Patent Office: 2,472 Days
• Field of Search: 604503-505, 702/55, 702/156
• US Class Current: 1/1
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 2205/3389 Continuous level detection A61M2205/3393 takes precedence
• CPC Class Codes: A61M 2205/3396 Reservoirs being alternately filled and emptied for measuring flow rate or delivered volume
• CPC Class Codes: A61M 2205/3592 using telemetric means, e.g. radio or optical transmission
• CPC Class Codes: A61M 2205/502 User interfaces, e.g. screens or keyboards
• CPC Class Codes: A61M 2205/702 automatically during use
• CPC Class Codes: A61M 2209/045 for filling, e.g. for filling reservoirs
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: A61M 5/16809 by repeated filling and emptying of an intermediate volume pressure infusion using positive displacement pumps A61M5/142
• CPC Class Codes: A61M 5/1684 by detecting the amount of infusate remaining, e.g. signalling end of infusion
• CPC Class Codes: G01F 23/14 by measurement of pressure

Abstract

The present invention includes systems and methods for detecting fluid flow into or out of a port chamber or a reservoir of an implantable medical device utilizing a pressure sensor and calculating the fluid status of the reservoir. The system detects characteristic pressure profiles associated with fluid flowing into the medical device, out of the medical device, and also whether one or both of the port chamber or reservoir are substantially empty or substantially full. In addition, the present invention may generate a sensory cue to a clinician to indicate the fluid status.

Claims

1. A method for calculating a fill status of a reservoir in an implantable medical device during a procedure to refill the reservoir, the method comprising:

determining a rate of change of the pressure as fluid is added to the reservoir via a fill port assembly in communication with the reservoir;

determining a fluid flow rate into the reservoir based on the rate of change of the pressure;

determining a total volume of fluid added to the reservoir by integrating the fluid flow rate over the time when fluid is added in which the pressure is sensed using the pressure sensor; and

combining the total volume of fluid added to the reservoir with a known starting volume of fluid in the reservoir to determine a volume of fluid in the reservoir during the refill procedure.

2. The method of claim 1 wherein combining the total volume of fluid added to the reservoir with the known starting volume of fluid in the reservoir is performed by a logic circuit.

3. The method of claim 1 wherein the fluid flow rate is positive when fluid is being added to the reservoir and negative when fluid is being removed from the reservoir.

4. The method of claim 1 further comprising determining the known starting volume by subtracting a fluid volume pumped from the implantable medical device since the last time point at which the reservoir was full.

5. The method of claim 4 wherein the volume pumped from the implantable medical device is determined from multiplying the number of strokes of the pump by the volume of fluid pumped per stroke.

6. The method of claim 1 wherein the pressure sensor is in the reservoir.

7. The method of claim 1 wherein sensing the reservoir pressure further comprises:

sensing a pressure upstream of the reservoir using the pressure sensor; and

calculating the reservoir pressure based on a known fluidic restriction between the upstream pressure sensor and the reservoir.

8. The method of claim 1 further comprising:

determining a rate of change of the pressure as fluid is removed from the reservoir via the fill port assembly in fluid communication with the reservoir;

determining a fluid flow rate out of the reservoir based on the rate of change of the pressure;

determining a total volume of fluid removed from the reservoir by integrating the fluid flow rate over the time when fluid is removed in which the pressure is sensed using the pressure sensor; and

combining the total volume of fluid removed from the reservoir with the known starting volume of fluid in the reservoir to determine the volume of fluid in the reservoir.

9. A method for displaying a fluid status of a reservoir of an implantable medical device during a procedure to refill the reservoir, comprising:

determining a rate of change of the pressure as fluid is added to the reservoir via a fill port assembly in communication with the reservoir;

determining a fluid flow rate into the reservoir based on the rate of change;

determining a total volume of fluid added to the reservoir by integrating the fluid flow rate over a time when fluid is added in which the pressure is sensed using the pressure sensor;

combining the total volume of fluid added to the reservoir with a known starting volume of fluid in the reservoir to determine a volume of fluid in the reservoir during the refill procedure; and

displaying the determined volume of fluid in the reservoir on a programmer.

10. The method of claim 9 further comprising updating the determined volume of fluid in the reservoir on a continuous basis.

11. The method of claim 9 wherein displaying the determined volume of fluid in the reservoir fluid status on the programmer includes displaying the determined volume of fluid in the reservoir on a gauge.

12. The method of claim 9 wherein combining the total volume of fluid added to the reservoir with the known starting volume of fluid in the reservoir is performed by a logic circuit.

13. The method of claim 9 wherein the fluid flow rate is positive when fluid is being added to the reservoir and negative when fluid is being removed from the reservoir.

14. The method of claim 9 wherein the pressure sensor is in the reservoir.

15. The method of claim 9 wherein sensing the reservoir pressure further comprises:

sensing a pressure upstream of the reservoir using the pressure sensor; and

calculating the reservoir pressure based on a known fluidic restriction between the upstream pressure sensor and the reservoir.

16. The method of claim 9 further comprising:

determining a rate of change of the pressure as fluid is removed from the reservoir via the fill port assembly in communication with the reservoir;

determining a fluid flow rate out of the reservoir based on the rate of change of the pressure;

determining a total volume of fluid removed from the reservoir by integrating the fluid flow rate over the time when fluid is removed in which the pressure is sensed using the pressure sensor; and

combining the total volume of fluid removed from the reservoir with the known starting volume of fluid in the reservoir to determine the volume of fluid in the reservoir.