Bioimpedance measurement system and method

• US 7,842,031 B2
• Filed: 11/18/2005
• Issued: 11/30/2010
• Est. Priority Date: 11/18/2005
• Status: Expired due to Fees

• Current Assignee: Medtronic CryoCath LP (Medtronic Plc)
• Original Assignee: Medtronic CryoCath LP (Medtronic Plc)
• Inventors: Harmouche, Chadi, Asmar, Johnny Al, Abboud, Marwan
• Primary Examiner(s): Hindenburg; Max
• Assistant Examiner(s): Pani; John
• Application Number:
  US11/283,057
• Publication Number:
  US 20070255162A1
• Time in Patent Office: 1,838 Days
• Field of Search: 600/506, 600/547, 600 24- 26, 606/20, 606/21, 606/23, 324/605
• US Class Current: 606/20
• CPC Class Codes: A61B 18/02 by cooling, e.g. cryogenic techniques devices for cooling specific reflex points of the body within cell-life limits A61H39/06
• CPC Class Codes: A61B 2017/00026 Conductivity or impedance, e.g. of tissue
• CPC Class Codes: A61B 2018/0022 Balloons
• CPC Class Codes: A61B 2018/0212 using an instrument inserted into a body lumen, e.g. catheter
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content

Abstract

Methods and systems for detecting fluid egress, assessing lesion quality, determining tissue composition or structure, determining ice coverage of catheter tip and providing tissue contact assessment, by providing a catheter having a shaft with a proximal end portion and a distal end portion, the proximal end portion and the distal end portion define at least one fluid pathway therebetween with the shaft having a plurality of electrodes, positioning the catheter at a tissue treatment site, applying an electrical current between at least two of the plurality of electrodes, measuring impedance voltage between the at least two of the plurality of electrodes and, processing the measured impedance voltage caused by the applied electrical current to determine if fluid egress is present, to assess lesion quality, to determine tissue composition, ice cover of catheter tip, and to provide contact assessment. The system may have a control unit, a microprocessor, an impedance measuring device or the like to perform processing of impedance data.

Claims

1. A method for determining fluid egress comprising:

positioning a catheter at a tissue treatment site, the catheter comprising;

a shaft having a proximal portion, a distal tip, and at least one fluid pathway therebetween;

an expandable element defining a cooling chamber therein in fluid communication with the at least one fluid pathway;

a first electrode located on an exterior surface of the shaft between the proximal portion and the expandable element; and

a second electrode located on the exterior surface of the shaft between the expandable element and the distal tip;

applying an electrical current between the first and second electrodes to form an electrical field about the expandable element;

measuring impedance between the first and second electrodes; and

correlating the measured impedance to a condition of fluid egress from the cooling chamber to a point exterior to the catheter, and generating a signal indicating the condition of fluid egress from the cooling chamber to the point exterior to the catheter.

2. The method of claim 1, wherein correlating the measured impedance includes:

establishing a normal impedance range;

comparing the measured impedance to the normal impedance range; and

generating a signal if the measured impedance is outside of the normal impedance range.

3. The method of claim 1, wherein the electrical current is a low frequency signal.

4. The method of claim 1, wherein correlating the measured impedance is performed by a microprocessor.

5. The method of claim 1, wherein measuring impedance is performed by an impedance measuring circuit.