Method and device for determining the segmental volume and electrical parallel conductance of a cardiac chamber or blood vessel

• US 20040024329A1
• Filed: 08/28/2003
• Published: 02/05/2004
• Est. Priority Date: 09/07/2000
• Status: Active Grant

• Current Assignee: Cardio Dynamics
• Original Assignee: Johannes J. Schreuder, Jozef R.C. Jansen
• Inventors: Schreuder, Johannes Jacobus, Jansen, Jozef Reinier Cornelis
• Granted Patent: US 7,069,072 B2
• Time in Patent Office: Days
• US Class Current: 600/526
• CPC Class Codes: A61B 5/0275 using tracers, e.g. dye dilution
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295

Abstract

The segment volume of a cardiac chamber or blood vessel of a patient is determined by injecting a first indicator in the blood stream of a patient, which influences the conductance of the blood. The electrical conductance in the cardiac chamber or blood vessel is measured. An injected quantity of indicator is determined and the development of the concentration of this indicator in the blood is measured wherein the cardiac output is calculated from the injected quantity of indicator and the development of the concentration in the blood. Subsequently, the segment volume and electrical parallel conductance of a cardiac chamber or blood vessel are calculated from the calculated cardiac output, the injected quantity of conductance indicator and the measured conductance.

Claims

1. Method for determining the segmental volume and the electrical parallel conductance of a cardiac chamber or a blood vessel of a patient, wherein a first indicator, which influences the conductance of the blood, is injected into the bloodstream of a patient, wherein the electrical conductance in said cardiac chamber or blood vessel is measured and wherein the sum of the segmental volume of said cardiac chamber or blood vessel and the electrical parallel conductance is calculated from said conductance, characterized in that an injected quantity of indicator is determined and the development of the concentration of this indicator in the blood is measured, wherein the cardiac output is calculated from the injected quantity of indicator and the development of the concentration thereof, and wherein the segmental volume and electrical parallel conductance of a cardiac chamber or a blood vessel are calculated from the calculated cardiac output, the injected quantity of conductance indicator and the measured conductance.

2. Method according to claim 1, wherein only one conductance indicator is injected and wherein the development of the concentration of the conductance indicator is measured for the purpose of calculating the cardiac output, wherein the development of the conductance, the temperature or the colour of the indicator is measured, for example.

3. Method according to claim 1, wherein a second indicator for measuring the development of the concentration is injected.

4. Method according to any one of the preceding claims, wherein the calculated parallel conductance is used as a correction value and wherein the segmental volume is determined exclusively from the conductance signal by means of said correction value.

5. Method according to any one of the preceding claims, wherein the period of the heartbeat is divided into equal time segments, and wherein the segmental volume and the electric parallel conductance of a cardiac chamber or a blood vessel within the heartbeat are monitored continuously.

13. Catheter for use in a method or an apparatus according to any one of the preceding claims, characterized by a first detector for measuring a conductance signal depending on the electrical conductance, and a second detector for measuring an indicator signal depending on a concentration of indicator in the blood.

14. Catheter according to claim 13, wherein said second detector comprises a number of parallel electrodes, which are preferably axially provided on the catheter.

15. Catheter according to claim 13 or 14, wherein said first detector is positioned near the distal end and said second detector is positioned some distance away from said distal end.

16. Catheter according to any one of the claims 13-15, wherein the catheter includes a lumen comprising at least one outlet opening between said first detector and said distal end.

17. Catheter according to any one of the claims 13-16, wherein said catheter comprises a third detector corresponding to said first detector, which is spaced from said distal end by such a distance that said third detector will be positioned in the aorta when said first detector is positioned in the heart.

6. Apparatus for determining the segmental volume of a cardiac chamber or a blood vessel of a patient, comprising a processing unit having a control output for initiating the injection of a first indicator into the bloodstream of the patient, which influences the conductance of the blood, a first detector to be placed in a cardiac chamber or blood vessel for measuring a conductance signal, which depends on the electrical conductance at the location of the detector, wherein said processing unit is arranged for calculating the segmental volume of the cardiac chamber or the blood vessel from said conductance signal, characterized by a second detector to be placed in the bloodstream for measuring an indicator signal depending on a concentration of indicator in the blood, wherein said processing unit is arranged for calculating the cardiac output from the injected quantity of indicator and the indicator signal, and calculating the segmental volume and electrical parallel conductance of a cardiac chamber or a blood vessel from the calculated cardiac output, the injected quantity of conductance indicator and the conductance signal.

7. Apparatus according to claim 6, wherein said second detector is adapted for measuring the concentration of said conductance indicator.

8. Apparatus according to claim 6, wherein said control output initiates the injection of a second indicator, wherein said second detector is adapted for measuring the concentration of said second indicator.

9. Apparatus according to any one of the preceding claims 6-8, wherein said control output controls at least one injector device for injecting an indicator.

10. Apparatus according to any one of the preceding claims 6-9, wherein said processing unit uses the calculated parallel conductance as a correction value for determining the segmental volume exclusively from said conductance signal.

11. Apparatus according to any one of the preceding claims 6-10, wherein said first and said second detector are housed in a common catheter.

12. Apparatus according to claim 11, wherein said catheter also includes a lumen for injecting an indicator.