METHOD AND SYSTEM FOR ESTIMATING EXERCISE CAPACITY

• US 20100191127A1
• Filed: 02/21/2008
• Published: 07/29/2010
• Est. Priority Date: 02/23/2007
• Status: Active Grant

• Current Assignee: Baxter Healthcare SA (Baxter International Inc.), Baxter International Inc.
• Original Assignee: Cheetah Medical, Inc. (Baxter International Inc.)
• Inventors: Squara, Pierre, Burkhoff, Daniel, Avidor, Yoav, Keren, Hanan
• Granted Patent: US 8,876,725 B2
• Time in Patent Office: Days
• US Class Current: 600/484
• 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 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• 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 5/0295 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
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/4869 Determining body composition

Abstract

A method of estimating exercise capacity of a subject is disclosed. The method uses output radiofrequency signals transmitted to the subject during exercise and input radiofrequency signals received from the subject during exercise. The method comprises: determining a phase shift of the input radiofrequency signals relative to the output radiofrequency signals; calculating cardiac output based on the phase shift; and using the cardiac output for estimating the exercise capacity of the subject.

Claims

1. A method of estimating exercise capacity of a subject using output radiofrequency signals transmitted to the subject during exercise and input radiofrequency signals received from the subject during exercise, the method comprising:

determining a phase shift of the input radiofrequency signals relative to the output radiofrequency signals;

calculating cardiac output based on said phase shift; and

using said cardiac output for estimating the exercise capacity of the subject.

2. The method of claim 1, further comprising obtaining at least one CPX measure pertaining to a cardiopulmonary exercise testing, and combining said cardiac output with said at least one CPX measure to estimate the exercise capacity of the subject.

3. A method of estimating exercise capacity of a subject, comprising:

transmitting output radiofrequency signals to the subject during exercise;

receiving input radiofrequency signals from the subject during exercise; and

executing the method of claim 1.

4. The method of claim 1, further comprising reducing or eliminating amplitude modulation of said input radiofrequency signals so as to provide input radiofrequency signals of substantially constant envelope.

5. The method of claim 1, further comprising mixing said output radiofrequency signals and said input radiofrequency signals so as to provide a mixed radiofrequency signal, and filtering out a portion of said mixed radiofrequency signal so as to substantially increase a signal-to-noise ratio of a remaining portion of said mixed radiofrequency signal.

6. The method of claim 3, further comprising performing a cardiopulmonary exercise testing to provide at least one CPX measure and combining said cardiac output with said at least one CPX measure to estimate the exercise capacity of the subject.

7. The method of claim 1, further comprising applying a dynamically variable filter.

15. The method of claim 1, wherein said cardiac output is calculated using a linear relationship between said phase shift and said cardiac output.

16. The method of claim 7, wherein said dynamically variable filter is adapted in response to a change in a physiological condition of the subject.

17. The method of claim 16, wherein said physiological condition is a heart rate of the subject.

18. The method of claim 17, wherein a lower frequency bound characterizing said filter is about 0.9*(HR/60) Hz at all times, wherein said HR is said heart rate in units of beats per minute.

19. The method of claim 17, wherein an upper frequency bound characterizing said filter is about 6+1.5*[(HR/60)−

1] Hz at all times, wherein said HR is said heart rate in units of beats per minute.

20. The method of claim 2, wherein said at least one CPX measure comprises ratio of ventilation efficiency to carbon dioxide production rate.

21. The method of claim 2, wherein said at least one CPX measure comprises oxygen uptake efficiency slope.

8. Apparatus for estimating exercise capacity of a subject using output radiofrequency signals transmitted to the subject during exercise and input radiofrequency signals received from the subject during exercise, the apparatus comprising:

a phase shift determinator configured for determining a phase shift of the input radiofrequency signals relative to the output radiofrequency signals;

a cardiac output calculator configured for calculating cardiac output based on said phase shift; and

an exercise capacity estimator configured for using said cardiac output for estimating the exercise capacity of the subject.

9. The apparatus of claim 8, wherein said exercise capacity estimator is configured for combining said cardiac output with at least one CPX measure to estimate the exercise capacity of the subject.

10. A system for estimating exercise capacity of a subject, comprising:

a radiofrequency generator for generating output radiofrequency signals;

a plurality of electrodes designed for transmitting said output radiofrequency signals to the subject and for sensing input radiofrequency signals from the subject; and

the apparatus of claim 8.

11. The system of claim 10, further comprising a cardiopulmonary exercise testing system configured to provide at least one CPX measure, wherein said exercise capacity estimator is configured for combining said cardiac output with at least one CPX measure to estimate the exercise capacity of the subject.

12. The apparatus of claim 8, wherein the apparatus further comprises an envelope elimination unit designed and configured for reducing or eliminating amplitude modulation of said input radiofrequency signals so as to provide input radiofrequency signals of substantially constant envelope.

13. The apparatus of claim 8, wherein the apparatus further comprises:

a mixer configured for mixing said output radiofrequency signals and said input radiofrequency signals, to provide a mixed radiofrequency signal; and

a radiofrequency filter for filtering out a portion of said mixed radiofrequency signal so as to substantially increase a signal-to-noise ratio of a remaining portion of said mixed radiofrequency signal.

14. The apparatus of claim 8, wherein the apparatus further comprises a filtering unit configured for filtering said input signals using dynamically variable filter.