PRESSURE BASED REFILL STATUS MONITOR FOR IMPLANTABLE PUMPS

• US 20100125246A1
• Filed: 11/16/2009
• Published: 05/20/2010
• 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.
• Granted Patent: US 9,421,325 B2
• Time in Patent Office: Days
• US Class Current: 604/151
• 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 the fill status of a reservoir in an implantable medical device, the method comprising:

sensing a pressure differential between the reservoir and a fill port using a pressure sensor;

calculating the fluid rate at which fluid is added to or removed from the reservoir based upon pressure differential and a known fluidic restriction constant for the medical device;

determining the total volume of fluid added to or removed from the reservoir by integrating the fluid rate over the time in which the sensed pressure change is detected; and

combining the fluid volume added to or removed from the reservoir with the known starting volume of the reservoir to determine the fill status.

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

3. The method of claim 1 wherein the fluid 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 the fluid volume pumped from the implantable medical device since the last 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. A method for displaying a fluid status of the reservoir of an implantable medical device comprising:

calculating the fluid status by sensing a pressure differential between the reservoir and a fill port using a pressure sensor;

calculating the fluid rate at which fluid is added to or removed from the reservoir based upon pressure differential and a known fluidic restriction constant for the medical device;

determining the total volume of fluid added to or removed from the reservoir by integrating the fluid rate over the time in which the sensed pressure change is detected; and

combining the fluid volume added to or removed from the reservoir with the known starting volume of the reservoir to determine the fill status; and

displaying the calculated fluid status on a programmer.

7. The method of claim 6 further comprising updating the calculated fluid status on a continuous basis.

8. The method of claim 6 wherein displaying the calculated fluid status on a programmer includes displaying the fluid status on a gauge.

9. The method of claim 6 wherein combining the fluid volume added to or removed from the reservoir with the known starting volume of the reservoir is performed by a logic circuit.

10. The method of claim 6 wherein the fluid rate is positive when fluid is being added to the reservoir and negative when fluid is being removed from the reservoir.

11. 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 pressure sensor in fluid communication with the port chamber; and

,

electronics disposed in the housing and operably coupled to the pressure sensor, the electronics including a computer readable medium containing instructions for calculating a fluid status of the reservoir.