Pressure based refill status monitor for implantable pumps

• US 9,814,833 B2
• Filed: 08/22/2016
• Issued: 11/14/2017
• 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:
  US15/242,766
• Publication Number:
  US 20160354540A1
• Time in Patent Office: 449 Days
• 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. An implantable infusion device comprising:

a housing;

a port assembly defining a port chamber, the port assembly being disposed in the housing such that the chamber is accessible by a needle inserted through the exterior of the housing;

a re-fillable reservoir in communication with the port chamber;

a pressure sensor in fluid communication with the port chamber and configured to sense a rate of change of pressure as fluid is added to the reservoir via the port chamber; and

electronics disposed in the housing and operably coupled to the pressure sensor, the electronics operated to determine a fluid flow rate into the reservoir based on the rate of change of the pressure, determine a total volume of fluid added to the reservoir by integrating the fluid flow rate over the time when fluid is added to the reservoir, 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 implantable infusion device of claim 1, wherein the pressure sensor is in the reservoir.

3. The implantable infusion device of claim 1, wherein the pressure sensor is upstream of the reservoir.

4. The implantable infusion device of claim 3, wherein the electronics are operated to calculate the reservoir pressure based on a known fluidic restriction between the upstream pressure sensor and the reservoir.

5. The implantable infusion device of claim 1, wherein the electronics are further operated to determine the known starting volume by subtracting the fluid volume pumped from the implantable medical device since the last time point at which the reservoir was full.

6. The implantable infusion device of claim 5, wherein the electronics are operated to determine the volume pumped from the implantable medical device by multiplying the number of strokes of the pump by the volume of fluid pumped per stroke.

7. The implantable infusion device of claim 1, wherein the electronics are further operated to determine a fluid flow rate out of the reservoir based on the rate of change of the pressure when fluid is removed from the reservoir via the port chamber.

8. The implantable infusion device of claim 7, wherein the electronics are further operated to determine a total volume of fluid removed from the reservoir via the port chamber by integrating the fluid flow rate over the time when fluid is removed from the reservoir via the port chamber.

9. An implantable infusion device comprising:

a housing;

a port assembly defining a port chamber, the port assembly being disposed in the housing such that the chamber is accessible by a needle inserted through the exterior of the housing;

a re-fillable reservoir in communication with the port chamber;

a pressure sensor in fluid communication with the port chamber and configured to sense a rate of change of pressure as fluid is added to the reservoir via the port chamber; and

electronics disposed in the housing and operably coupled to the pressure sensor, the electronics operated to determine a fluid flow rate out of the reservoir based on the rate of change of the pressure, determine a total volume of fluid removed from the reservoir by integrating the fluid flow rate over the time when fluid is removed from the reservoir, and subtracting the total volume of fluid removed from the reservoir from a known starting volume of fluid in the reservoir to determine a volume of fluid in the reservoir.

10. The implantable infusion device of claim 9, wherein the electronics are further operated to determine the known starting volume by subtracting the fluid volume pumped from the implantable medical device since the last time point at which the reservoir was full.

11. The implantable infusion device of claim 10, wherein the electronics are operated to determine the volume pumped from the implantable medical device by multiplying the number of strokes of the pump by the volume of fluid pumped per stroke.

12. A method for calculating a fill status of a reservoir in an implantable medical device during a procedure to refill the reservoir, the method, carried out by electronics of the implantable medical device, comprising:

sensing a pressure differential between the reservoir and a fill port using a pressure sensor as fluid is introduced into the reservoir via the fill port;

determining a rate of change of the pressure differential as the fluid is introduced into the reservoir;

determining a fluid rate at which the fluid is introduced to the reservoir based upon the rate of change of the pressure differential and a known fluidic constant for the medical device;

determining a total volume of fluid added to the reservoir by integrating the fluid rate over the time in which fluid is introduced into the reservoir; and

combining the total volume of fluid added to the reservoir with a known starting volume of the reservoir to determine the fill status.

13. The method of claim 12 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 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.

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