Pressure-sensitive conductive composite contact sensor and method for contact sensing

• US 9,579,483 B2
• Filed: 12/29/2006
• Issued: 02/28/2017
• Est. Priority Date: 12/29/2006
• Status: Active Grant

• Current Assignee: St. Jude Medical, Atrial Fibrillation Division, Inc. (Abbott Laboratories)
• Original Assignee: St. Jude Medical, Atrial Fibrillation Division, Inc. (Abbott Laboratories)
• Inventors: Belhe, Kedar Ravindra, Paul, Saurav
• Primary Examiner(s): EISEMAN, ADAM JARED
• Application Number:
  US11/647,314
• Publication Number:
  US 20080161786A1
• Time in Patent Office: 3,714 Days
• Field of Search: 600/374, 600/486, 600/488, 600/547, 600/561, 606/32, 128/899, 737/79
• US Class Current: 1/1
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 2018/00083 low, i.e. electrically insulating
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/00988 Means for storing information, e.g. calibration constants, or for preventing excessive use, e.g. usage, service life counter
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 2090/065 for measuring contact or contact pressure
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61M 2025/0002 with a pressure sensor at the distal end
• CPC Class Codes: A61M 25/00 Catheters; Hollow probes dilators A61M29/00; peritoneal catheters A61M1/285; tracheal tubes A61M16/04; for drainage A61M27/00; for uterus, vagina or rectum A61M31/00 ; for measuring or testing A61B; materials for catheters A61L29/00
• CPC Class Codes: G01L 1/20 by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids of piezo-resistive materials G01L1/18; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress

Abstract

A catheter assembly for assessing contact between the catheter assembly and tissue is disclosed. The assembly includes a catheter shaft and a pressure sensitive conductive composite member whose electrical resistance varies with pressure applied to the catheter assembly. The assembly also includes at least one measurement terminal to permit the measurement of changes in the electrical characteristics of the pressure sensitive conductive composite member. The assembly may optionally include a measurement device to measure resistance, impedance and/or other electrical characteristics. The assembly may utilize a reference electrode secured to the patient'"'"'s tissue, which permits the measurement device to measure changes between the reference electrode and the at least one measurement terminal. Optionally, the assembly may include a conductive outer layer. Also disclosed are sensor assemblies, contact sensor, methods of contact sensing, and methods of manufacturing relating to the use of pressure sensitive conductive composites.

Claims

1. A sensor assembly for assessing contact between the sensor assembly and tissue, said assembly comprising:

a catheter shaft;

a conductive core having a first measurement terminal

a continuous layer of a pressure sensitive conductive composite in electrical contact with said conductive core, said layer including a tissue contact surface that may be placed in contact with tissue, wherein the continuous layer of pressure sensitive conductive composite consists essentially of a non-conductive polymer substrate having a plurality of conductive particles embedded therein, and wherein the pressure sensitive conductive composite has a resistance that varies anisotropically and inversely with pressure to less than one ohm; and

a measurement device coupled to the first measurement terminal such that said measurement device measures an electrical characteristic of the pressure sensitive conductive composite;

wherein when the tissue contact surface applies pressure to the tissue, the measurement device will measure a change in electrical characteristics of the pressure sensitive conductive composite and provide a user with information regarding a degree of contact between the sensor assembly and the tissue being contacted.

2. The catheter assembly of claim 1 further comprising:

a memory coupled to the measurement device for storing a plurality of electrical characteristic measurements; and

a processor coupled to the measurement device for assessing a degree of contact using a plurality of measurements stored in the memory.

3. The catheter assembly of claim 1 further comprising:

a conductive outer layer having a second measurement terminal, said conductive outer layer covering at least a portion of the layer of pressure sensitive conductive composite, and wherein the measurement device measures electrical characteristics of the layer of pressure sensitive conductive composite using the first measurement terminal and the second measurement terminal.

4. The catheter assembly of claim 3 further comprising:

a non-conductive outer layer covering at least a portion of the conductive outer layer.

5. The catheter assembly of claim 1 further comprising:

a reference electrode for electrically coupling to tissue, said reference electrode having a second measurement terminal;

wherein the measurement device measures electrical characteristics of the layer of pressure sensitive conductive composite using the first measurement terminal and the second measurement terminal.

6. A contact sensor assembly for assessing contact between the contact sensor assembly and tissue, said assembly comprising:

an elongate catheter body having a proximal end and a distal end;

a conductive core having a first measurement terminal, said conductive core extending at least a portion of the distal end;

a pressure sensitive conductive composite material electrically coupled to at least a portion of the conductive core located in the distal end of the catheter body, wherein the pressure sensitive conductive composite material consists essentially of a non-conductive polymer substrate having a plurality of conductive particles embedded therein, and wherein the pressure sensitive conductive composite material is an electrical insulator when in a quiescent state and has a resistance that varies anisotropically and inversely with pressure to less than one ohm;

a conductive layer having a second measurement terminal, said conductive layer covering at least a portion of the pressure sensitive conductive composite material, and said conductive layer extending at least a portion of the distal end of the catheter body;

wherein electrical characteristics of the pressure sensitive conductive composite material may be measured using the first measurement terminal and the second measurement terminal.

7. The contact sensor assembly of claim 6, further comprising:

a measurement device that measures a signal using the first and second measurement terminals and that generates an output signal that is indicative of the pressure being applied to the tissue by the distal end.