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Triggered flow measurement

Imported: 24 Feb '17 | Published: 06 Jan '04

Sauli Tulkki, Leif Smith

USPTO - Utility Patents

Abstract

When a bolus dose of cold saline is injected into a catheter where a wire, carrying a sensor unit and electrical leads for signal transmission, is located, the lead resistance is affected by the cold saline thereby altering the resistivity. However, by countering this effect and measuring the change needed to affect this countermeasure, a resistance variation curve can be generated. An accurate starting point for the determination of a transit time can be derived from the curve. Using conventional flow measurement calculations with the accurate starting point yields a better understanding of the flow profile in an artery based on the transit time.

Description

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an overview that shows a system wherein the novel method is performed;

FIGS. 2

a-d are graphs illustrating the resistivity profiles of the electrical leads during measurement;

FIG. 3 is a graph showing measurements on a patient during hyperemia;

FIG. 4 is a graph showing measurements on a patient during a resting period;

FIG. 5 is a graph showing the correlation between measurement data on patients according to the invention and a reference method;

FIG. 6 is a graph showing the correlation between another set of patient data according to the invention and a reference method;

FIG. 7 illustrates an indicator dilution curve obtained in a vascular network; and

FIG. 8 illustrates calculation of flow in an indicator solution;

FIG. 9 illustrates a curve used in determining the center of mass.

Claims

1. A method of triggering a time measurement in a system for the measurement of a transit time of a finite amount of an indicator first liquid injected in a flow of a second liquid in the course of a thermo-dilution measurement, wherein said flow of the second liquid has a different temperature than the temperature of said indicator first liquid, said system having a temperature sensitive part, said method of triggering comprising the steps of:

2. The method as claimed in claim 1, wherein said temperature sensitive part of said system is at least one electrical lead connecting an electrical measuring device, located in said flow of said second liquid, with externally located control equipment.

3. The method as claimed in claim 2, wherein said electrical resistance is the electrical resistance of said at least one lead.

4. The method as claimed in claim 3, wherein a resistance variation of said electrical lead is registered, and wherein said method comprises the further steps of:

5. The method as claimed in claim 4, wherein said point is selected by calculating the derivative of said resistance variation curve, and taking a point in time where said derivative exceeds a predetermined level as said starting point.

6. The method as claimed in claim 4, wherein said point is selected by calculating the second derivative of said resistance variation curve, and taking a point in time where said second derivative changes sign as said starting point.

7. The method as claimed in claim 4, wherein said point is selected by calculating the average between the point in time when the injection of said indicator liquid is started and the point in time when the injection is stopped.

8. The method as claimed in claim 2, wherein said electrical measuring device is a temperature sensor.

9. The method as claimed in claim 1, wherein the temperature of said indicator liquid is lower than the second liquid, and wherein the second liquid is blood.

10. A method of determining a transit time of a finite amount of an indicator first liquid injected in a flow of a second liquid in the course of a thermo-dilution measurement, wherein said indicator first liquid has a temperature which is lower than the prevailing temperature inside a blood vessel, said method comprising the steps of:

11. A method of determining a transit time of a finite amount of an indicator first liquid injected in a flow of a second liquid in the course of a thermo-dilution measurement, wherein said indicator first liquid has a temperature which is lower than the prevailing temperature inside a blood vessel, said method comprising the steps of:

12. An apparatus for determining a transit time of a finite amount of an indicator first liquid injected in a flow of a second liquid in the course of a thermo-dilution measurement, said apparatus comprising:

wherein the detection unit is adapted to switch between measuring the signal produced by the sensor and the resistivity of the wire, and wherein the detection unit uses the measurement of the resistivity of the wire to determine a starting point for the measurement of fluid flow.

13. The apparatus according to claim 12, wherein the sensor comprises a temperature sensor.

14. The apparatus according to claim 13, wherein the signal monitored by the sensor is the temperature of the second liquid.

15. The apparatus according to claim 13, wherein the sensor further comprises a pressure sensor.

16. The apparatus according to claim 12, wherein the syringe is connected to the guide catheter by a Luer lock.

17. The apparatus according to claim 12, wherein the indicator first liquid is saline.