Method and apparatus for measuring blood volume

• US 8,603,000 B2
• Filed: 05/07/2012
• Issued: 12/10/2013
• Est. Priority Date: 04/24/2007
• Status: Active Grant

• Current Assignee: Transonic Scisense Incorporated
• Original Assignee: Transonic Scisense Incorporated
• Inventors: Wood, Kim, Hodgson, P. Chad, Plouf, Peter
• Primary Examiner(s): Minnifield, Nita M
• Application Number:
  US13/465,796
• Publication Number:
  US 20120220886A1
• Time in Patent Office: 582 Days
• Field of Search: None
• US Class Current: 600/507
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2560/0252 using ambient temperature
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/02055 Simultaneously evaluating both cardiovascular condition and temperature
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/6852 Catheters
• CPC Class Codes: G01F 22/00 Methods or apparatus for measuring volume of fluids or fluent solid material, not otherwise provided for

Abstract

In one aspect, a conductance catheter is provided for measuring the volume of a fluid. The conductance catheter comprises a series of electrodes and a circuit to compensate for variations in sensitivity of the electrodes in the catheter. In another aspect, a resistivity sensor is provided for determining the resistivity of a fluid. The sensor comprises a series of electrodes spaced such that the total distance between endmost electrodes does not exceed the diameter of the catheter deploying the sensor.

Claims

1. A method for positioning a sensing tip disposed in a ventricle, the method comprising:

obtaining an excitation waveform generated by one pair of electrodes disposed on said sensing tip;

obtaining a conductance waveform sensed by another pair of electrodes disposed on said sensing tip;

enabling said waveforms to be compared to determine a phase shift between said waveforms; and

identifying when said phase shift is deemed acceptable due to adjustment of said positioning.

2. The method according to claim 1 wherein said enabling comprises superimposing said waveforms to provide a visual indication of said phase shift.

3. The method according to claim 1 further comprising determining said phase shift by comparing zero-crossings of said waveforms.

4. The method according to claim 1 performed in real time while said sensing tip is measuring volume of fluid in said ventricle.

5. The method according to claim 1 performed during a calibration operation.

6. A non-transitory computer readable medium for facilitating positioning a sensing tip disposed in a ventricle, the computer readable medium comprising computer executable instructions for:

obtaining an excitation waveform generated by one pair of electrodes disposed on said sensing tip;

obtaining a conductance waveform sensed by another pair of electrodes disposed on said sensing tip;

enabling said waveforms to be compared to determine a phase shift between said waveforms; and

identifying when said phase shift is deemed acceptable due to adjustment of said positioning.

7. The computer readable medium according to claim 6 wherein said enabling comprises superimposing said waveforms to provide a visual indication of said phase shift.

8. The computer readable medium according to claim 6, further comprising computer executable instructions for determining said phase shift by comparing zero-crossings of said waveforms.

9. The computer readable medium according to claim 6 further comprising computer executable instructions for performing said obtaining said excitation waveform, said obtaining said conductance waveform, said enabling and said identifying, in real time while said sensing tip is measuring volume of fluid in said ventricle.

10. The computer readable medium according to claim 6 further comprising computer executable instructions for performing said obtaining said excitation waveform, said obtaining said conductance waveform, said enabling and said identifying, during a calibration operation.