Non-Invasive Method And Device For Measuring Cardiac Output

• US 20100022900A1
• Filed: 01/05/2009
• Published: 01/28/2010
• Est. Priority Date: 01/04/2008
• Status: Active Grant

• Current Assignee: SARCOS LC (Sarcos Technology & Robotics Corp.)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Peterson, Stephen C., Jacobsen, Stephen C., Petelenz, Tomasz J.
• Granted Patent: US 8,721,559 B2
• Time in Patent Office: Days
• US Class Current: 600/508
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/0507 using microwaves or terahertz waves

Abstract

A system comprising a housing containing a signal generator coupled to an antenna and a dielectric material disposed about the antenna. The device is adapted to generate and direct a plurality of signals towards the heart of the person and measure a magnitude of a signal returned from the heart. The device further comprises a processor to compare differences between a magnitude of a signal propagated and the magnitude of the signal returned off the heart and determine a signal frequency having a maximum return loss value based on those differences. The processor also estimates a change in the amplitude of motion of a portion of a wall of the heart based on the differences between the magnitude of the signal propagated by the device and the magnitude of the signal returned off of the portion of the heart.

Claims

1. A method for measuring cardiac output of a person, comprising:

(a) placing a device about the center of the chest of the person at the mid-sternum position, said device comprising a RF signal generator coupled to an antenna, said antenna having a dielectric material disposed about the exterior of the antenna;

(b) propagating a first signal having a predetermined frequency towards the heart of the person;

(c) receiving and measuring a portion of the first signal returned from the heart of the person with the device;

(d) comparing the magnitude of the first signal propagated into the heart of the person to the magnitude of the portion of the first signal returned from the heart of the person and calculating a return loss of the signal;

(e) propagating an additional signal into a portion of the heart of the person using the device, wherein said additional signal has a frequency different from the first signal;

(f) receiving and measuring a portion of the signal returned from the heart of the person with the device;

(g) comparing the magnitude of the signal propagated into the heart to the person to the magnitude of the additional signal returned from the heart of the person and calculating a return loss of the additional signal;

(h) comparing the return loss of the first signal to the return loss of the additional signal;

(i) repeating steps (e) through (h) while incrementally varying the frequency of the signal with each repetitive step; and

(j) determining a maximum return loss value of the signals propagated into the heart of the person over the utilized frequency range; and

(k) determining the frequency of the maximum return loss signal.

2. The method of claim 1, wherein the signal comprises a radio frequency signal.

3. The method of claim 1, wherein the dielectric material is selected from the group consisting of ceramics, glass, liquids, gels and other polymeric materials.

4. The method of claim 1, further comprising estimating the amplitude of motion of the portion of a wall of the heart.

5. The method of claim 4, further comprising estimating a change in the amplitude of motion of the portion of the wall of the heart.

6. The method of claim 5, further comprising estimating a stroke volume of the heart based on the change in the amplitude of motion of the portion of the wall of the heart.

7. The method of claim 5, further comprising determining the timing of a QRS complex of the heart based on the change in the amplitude of motion of the wall of the heart.

8. The method of claim 5, further comprising determining the timing of a QRS complex of the heart based on the change in frequency of the maximum return loss.

9. The method of claim 1, wherein the portion of the heart comprises a right ventricle of the heart.

10. A system for measuring the cardiac output of the heart of a person, comprising:

a device comprising a housing containing a signal generator coupled to an antenna and a dielectric material disposed about the antenna, wherein said hand-held device is adapted to generate a plurality of radio frequency signals and direct said signals towards the heart of the person and measure a magnitude of a signal returned off the heart of the person;

a processor contained within said housing, said processor being adapted to compare differences between a magnitude of a signal propagated into the heart of the person and the magnitude of the signal reflected from the heart, said processor being further adapted to determine a signal frequency having a maximum return loss value based on the differences between the magnitude of the signal propagated into the heart of the person and the magnitude of the signal returned from the heart of the person; and

said processor being further adapted to estimate a change in the amplitude of motion of a portion of a wall of the heart based on the differences between the magnitude of the signal propagated by the device and the magnitude of the signal returned off of the portion of the heart.

11. The system of claim 10, wherein said processor is further adapted to calculate the cardiac output of the person;

and further comprising a display disposed about the hand-held device adapted to display the measured signals and that can be calibrated to display the estimated stroke volume of the person.

12. The system of claim 11, wherein said processor is further adapted to calculate the cardiac output of the person based on an estimated stroke volume of the person.

13. The system of claim 10, wherein said device is adapted to generate a signal at a frequency and magnitude having a determined maximum return loss value into the portion of the heart and receive a portion of the signal propagated into the portion of the heart.

14. The system of claim 10, wherein the dielectric material is selected from the group consisting of ceramics, glass, liquids, gels and other polymeric materials.

15. The system of claim 12, wherein said processor is further adapted to estimate the stroke volume of the heart based on a change in of the amplitude of motion of the portion of the wall of the heart.

16. The system of claim 15, wherein said processor is adapted to further comprise the step of estimating a QRS complex of the heart based on the change of the amplitude of motion of the portion of the wall of the heart.

17. The system of claim 15, wherein said processor is further adapted to further comprise the step of estimating a QRS complex of the heart based on the change of the frequency of the maximum return loss of the signal propagated towards the portion of the wall of the heart.

18. The system of claim 10, wherein the dielectric material has a predetermined thickness and a predetermined dielectric constant such that a substantial portion of a near field component of the signal propagated towards the heart of the person is contained within said dielectric material.

19. The system of claim 10, wherein the dielectric material has a predetermined thickness and a predetermined dielectric constant such that substantially an entire near field component of the signal propagated towards the heart of the person is contained within said dielectric material.