Systems and methods for detecting vascular access disconnection

• US 11,033,671 B2
• Filed: 06/18/2018
• Issued: 06/15/2021
• Est. Priority Date: 05/24/2011
• Status: Active Grant

• Current Assignee: Deka Products Limited Partnership
• Original Assignee: Deka Products Limited Partnership
• Inventors: van der Merwe, Dirk A., Norris, Michael G., Baker, Michael A., Ballantyne, Todd A., Wilt, Michael J.
• Primary Examiner(s): Klein, Benjamin J
• Application Number:
  US16/011,294
• Publication Number:
  US 20180296746A1
• Time in Patent Office: 1,093 Days
• CPC Class Codes: A61M 1/362227 the interface providing means for actuating on functional elements of the cassette, e.g. plungers
• CPC Class Codes: A61M 1/36224 with sensing means or components thereof
• CPC Class Codes: A61M 1/36225 with blood pumping means or components thereof
• CPC Class Codes: A61M 1/362263 Details of incorporated filters
• CPC Class Codes: A61M 1/362265 Details of valves
• CPC Class Codes: A61M 1/362266 Means for adding solutions or substances to the blood
• CPC Class Codes: A61M 1/3656 Monitoring patency or flow at connection sites; Detecting disconnections
• CPC Class Codes: A61M 2205/128 with incorporated valves
• CPC Class Codes: A61M 2205/14 Detection of the presence or absence of a tube, a connector or a container in an apparatus
• CPC Class Codes: A61M 2205/33 Controlling, regulating or measuring
• CPC Class Codes: A61M 2205/3317 Electromagnetic, inductive or dielectric measuring means

Abstract

A system for detecting whether a vascular access has been interrupted in an arrangement in which two catheters or needles are present in a blood vessel, fistula or graft. A fluid line leading to a pump is connected via a first connector to a first indwelling catheter, and a fluid line leading from a pump is connected via a second connector to a second indwelling catheter. Each connector is equipped with an electrode in contact with the lumen of the connector, the electrodes electrically connected to an electronic circuit that measures the impedance or conductivity of fluid between the first connector and second connectors via a fluid path through the blood vessel, fistula or graft. An electronic controller receives the impedance or conductivity data and processes the data to determine whether a vascular access disconnection has occurred. The processing may involve filtering the signal received by the controller, and/or setting provisional flags for a disconnection event that may be cleared if the signal changes before the expiration of a counter.

Claims

1. A system for detecting replacement of blood by dialysate solution in a blood tubing set of a hemodialysis apparatus in which dialysate is pumped from a dialysate side to a blood side of a dialyzer, the system comprising:

a first fluid line fluidly connecting a first catheter or needle in a blood vessel, fistula or graft to an inlet of a blood pump;

a second fluid line fluidly connecting a second catheter or needle in the blood vessel, fistula or graft to an outlet of the blood pump;

a first connector connecting the first fluid line to the first catheter or needle, and a second connector connecting the second fluid line to the second catheter or needle, the first connector having a first electrode in fluid communication with a fluid carrying lumen of said first connector, and the second connector having a second electrode in fluid communication with a fluid carrying lumen of said second connector;

an electronic circuit having a first terminal electrically connected to the first electrode and a second terminal electrically connected to the second electrode, and configured to measure electrical impedance of fluid between the first connector and the second connector via a conductive path through the blood vessel, fistula or graft;

a controller configured to receive a series of sampled electrical impedance values from the electronic circuit, and to process the electrical impedance values as a signal;

wherein the controller is configured to;

measure the signal or a filtered form of the signal as dialysate is pumped through the dialyzer to the blood tubing set;

determine whether the signal or a filtered form of the signal has a first value equal to an expected value of the signal for blood in the first and second fluid lines, or has a second value equal to an expected value of the signal for dialysate solution in the first and second fluid lines;

determine a point in time when the signal or a filtered form of the signal changes from the first value to the second value; and

provide a first notification to a user if the controller detects a change from the first value to the second value, or provide a second notification to the user if the controller detects a change from the first value that is less than the second value within a pre-determined period of time.

2. The system of claim 1, wherein the controller is configured to associate the change from the first value to the second value with a change in hematocrit of blood in the first and second fluid lines.

3. The system of claim 2, wherein the controller is configured to detect an attenuation of the change of the hematocrit, and to declare an occlusion if the attenuation is greater than a pre-determined amount.

4. The system of claim 3, wherein the controller is configured to declare an occlusion if the pre-determined amount of attenuation corresponds to a percentage of the first value.

5. The system of claim 4, wherein the percentage is 99%.

6. The system of claim 4, wherein the percentage is within a range of 93-97%.

7. The system of claim 1, wherein the controller is configured to set the first value to correspond to the highest impedance value during the first 12 seconds of a rinseback process in which dialysate solution is pumped into the blood tubing set.

8. The system of claim 7, wherein the percentage is not less than 97% of the first value.

9. The system of claim 1, wherein the filtered form of the signal comprises a difference between the measured electrical impedance filtered using a first time constant and the measured electrical impedance filtered using a second smaller time constant.

10. The system of claim 9, wherein the controller is configured to adjust the filtered form of the signal to vary in proportion to a change in a value of the electrical impedance filtered using the first time constant.

11. The system of claim 1, wherein the filtered form of the signal comprises a ratio between the measured electrical impedance filtered using a first time constant and the measured electrical impedance using a second smaller time constant.