Measurement of cardiac output and blood volume by non-invasive detection of indicator dilution

• US 20040215093A1
• Filed: 05/17/2004
• Published: 10/28/2004
• Est. Priority Date: 05/22/2001
• Status: Active Grant

• Current Assignee: The Alfred E. Mann Institute For Biomedical Engineering At The University Of Southern California (University of Southern California)
• Original Assignee: Alfred E MANN Institute For Biomedical Engineering At The University of Southern California
• Inventors: Rubenstein, Eduardo H., Holschneider, Daniel P., Maarek, Jean-Michel I., Scremin, Oscar V.
• Granted Patent: US 7,590,437 B2
• Time in Patent Office: Days
• US Class Current: 600/526
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0275 using tracers, e.g. dye dilution
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence

Abstract

A system for evaluating the cardiovascular system parameters using indicator dilution and non-invasive or minimally invasive detection methods is disclosed. Intravascular indicators are stimulated, and emissions patterns detected for computation of cardiac output, cardiac index, blood volume and other indicators of cardiovascular health.

Claims

1. A method of measuring in absolute physical units at least one parameter of the cardiovascular system of a subject comprising:

administering to the cardiovascular system of a subject a detectable amount of at least one indicator;

applying a first wavelength of light for exciting the indicator within the cardiovascular system and causing the indicator to emit a second wavelength of light,

measuring the intensity of the second wavelength of light emitted from the indicator in the circulatory system using at least one photodetector proximately located to a detection area of the subject;

determining the magnitude of the at least one parameter of the cardiovascular system in absolute physical units based on the measured intensity of the second wavelength of light.

2. The method of claim 1 wherein the second wavelength of light emitted from the indicator is caused by fluorescence of the indicator.

3. The method of claim 1 wherein the measured parameter of the cardiovascular system is cardiac output and wherein the method further comprises detecting the magnitude of intensity of the second wavelength of light emitted from the indicator over a time period, forming a magnitude of intensity curve for the time period, and wherein the mathematical analysis of cardiac output comprises at least one of curve fitting to a model equation or numerical integration.

4. The method of claim 3 further comprising calculating the cardiac index by expressing the cardiac output as a function of either the subject'"'"'s weight or the subject'"'"'s surface area.

5. The method of claim 1 wherein the measured parameter of the cardiovascular system is circulating blood volume and wherein the method further comprises detecting the magnitude of intensity of the second wavelength of light emitted from the indicator over a time period, forming a magnitude of intensity curve for the time period, and wherein the mathematical analysis of blood volume comprises back extrapolating a slow phase of the intensity curve to determine circulating blood volume.

6. The method of claim 1, wherein the photodetector is placed in at least one of a transdermal detection area, a subdermal detection area, a perivascular detection area or an endovascular detection area.

7. The method of claim 1, wherein the detecting is performed in either transmission mode or reflection mode.

8. The method of claim 1, wherein steps a-d are repeated at a time interval to determine if the cardiovascular value for the subject has changed.

9. The method of claim 1, further comprising treating the patient with a stimulus and wherein steps a-d are repeated at a time interval to determine if the cardiovascular value for the subject has changed after exposure to the stimulus.

10. The method of claim 1 wherein the detection area is arterialized by application of heat or pharmacologically prior to detecting the second wavelength of light at the detection area.

11. The method of claim 1 wherein the first wavelength of light is within the range of about 750 nm to about 1000 nm.

12. The method of claim 1 wherein the indicator is a chromophore or fluorophore emitting the second wavelength of light in a range from about 400 nm to about 1000 nm.

13. The method of claim 1 wherein the fluorophores are selected from the group comprising indocyanine green, fluorescein and rhodamine.

24. The method of claim 1 further including:

removing a blood sample containing indicator from the cardiovascular system; and

determining the concentration of the indicator in the removed blood sample.

14. A system for measuring in absolute physical units at least one parameters of the cardiovascular system of a subject comprising:

an illumination source configured to be positioned proximately to at least one blood vessel of the cardiovascular system for providing a first wavelength of light for exciting an indicator within the cardiovascular system and causing the indicator to emit a second wavelength of light;

a photodetector configured to be positioned proximate to at least one blood vessel of the cardiovascular system of the subject for detecting the magnitude of intensity of the second wavelength of light emitted from the indicator in the cardiovascular system and to generate electronic signals to indicative of the detected magnitude of intensity of the second wavelength of light;

a computing system configured to receive the electronic signals and to compute the magnitude of the at least one parameter of the cardiovascular system of the subject in absolute physical units based on the electronic signals.

15. The system of claim 14 further comprising at least one fiber optic probe operably connected to the illumination source for guiding the first wavelength of light from the illumination source to the detection area.

16. The system of claim 14 further comprising at least one fiber optic probe operably connected to the photodetector for guiding the second wavelength of light from the detection area to the photodetector.

17. The system of claim 14 further comprising at least one lock-in amplifier operably connected to the illumination source for modulating the first wavelength of light at a selected frequency, and operably connected to the photodetector for filtering the detection of the second wavelength of light at the selected frequency.

18. The system of claim 14 wherein the measured parameter of the cardiovascular system is cardiac output and wherein the method further comprises detecting the magnitude of intensity of the second wavelength of light emitted from the indicator over a time period, forming a magnitude of intensity curve for the time period, and wherein the mathematical analysis of cardiac output comprises at least one of curve fitting to a model equation or numerical integration.

19. The method of claim 18 further comprising calculating the cardiac index by expressing the cardiac output as a function of either the subject'"'"'s weight or the subject'"'"'s surface area.

20. The method of claim 14 wherein the measured parameter of the cardiovascular system is circulating blood volume and wherein the method further comprises detecting the magnitude of intensity of the second wavelength of light emitted from the indicator over a time period, forming a magnitude of intensity curve for the time period, and wherein the mathematical analysis of blood volume comprises back extrapolating a slow phase of the intensity curve to determine circulating blood volume.

21. The system of claim 14, wherein the photodetector is configured for placement in at least one of a transdermal detection area, a subdermal detection area, a perivascular detection area or an endovascular detection area.

22. The system of claim 14 wherein the first wavelength of light is in the range of about 750 nm to about 1000 nm.

23. The system of claim 14 wherein the indicator is a chromophore or fluorophore capable of emitting the second wavelength of light in a range from about 400 nm to about 1000 nm.

25. A method of measuring cardiac output of a subject comprising:

administering a detectable amount of at least one indicator to the cardiovascular system of a subject;

applying a first wavelength of light for exciting the indicator within the cardiovascular system and causing the indicator to emit a second wavelength of light;

measuring the intensity of the second wavelength of light emitted from the indicator in the circulatory system using at least one photodetector proximately located to a detection area of the subject; and

determining the magnitude of the cardiac output based on the measured intensity of the second wavelength of light.

26. The method of claim 25 wherein greater measured intensities cause determinations of smaller cardiac output.

27. A method of measuring blood volume in a subject comprising:

administering a detectable amount of at least one indicator to the cardiovascular system of a subject;

applying a first wavelength of light for exciting the indicator within the cardiovascular system and causing the indicator to emit a second wavelength of light;

measuring the intensity of the second wavelength of light emitted from the indicator in the circulatory system using at least one photodetector proximately located to a detection area of the subject; and

determining the magnitude of the blood volume based on the measured intensity of the second wavelength of light.

28. The method of claim 27 wherein greater measured intensities cause determinations of smaller blood volume.