Method of processing thoracic reflected radio interrogation signals

• US 20090240134A1
• Filed: 03/23/2009
• Published: 09/24/2009
• Est. Priority Date: 09/21/2006
• Status: Abandoned Application

• Current Assignee: Seemedx Incorporated
• Original Assignee: Seemedx Incorporated
• Inventors: McCaughan, Ann K., Pal, Andrew
• Application Number:
  US12/383,362
• Publication Number:
  US 20090240134A1
• Time in Patent Office: Days
• US Class Current: 600/407
• CPC Class Codes: A61B 5/0044 for the heart
• 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 5/0261 using optical means, e.g. infrared light
• 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 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1102 Ballistocardiography
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B

Abstract

A method of evaluating or monitoring the medical state of a subject comprising the steps of: providing a radio frequency interrogation interference signal from a subject, the radio frequency interrogation interference signal being low frequency components of reflections of a radio interrogation signal transmitted into the thorax of the subject; and determining at least one cardiac or respiratory characteristic of the subject from radio frequency interrogation interference signal. The characteristic can be compared to predetermined values to assess current state or monitored for changes over time to assess change in condition of the subject.

Claims

1. A method of evaluating medical state of a subject comprising the steps of:

providing a radio frequency interrogation interference signal from a subject, the radio frequency interrogation interference signal being low frequency components of reflections of a radio interrogation signal transmitted into the thorax of the subject; and

determining at least one cardiac or respiratory characteristic of the subject from radio frequency interrogation interference signal.

2. The method of claim 1 wherein the determining step comprises the steps of:

identifying at least one cardiac or respiratory cycle of the subject in the radio frequency interrogation interference signal; and

identifying the at least one characteristic in the at least one cycle.

3. The method of claim 2 further comprising the steps of:

identifying the at least one characteristic from a subsequent cycle; and

comparing the characteristics to determine changes of the characteristic over time.

4. The method of claim 2 further comprising the steps of:

identifying the at least one characteristic from a subsequent cycle; and

averaging the characteristics.

5. The method of claim 2 wherein the determining step comprises the steps of:

dividing the radio frequency interrogation interference signal into time segments containing several cardiac cycles; and

identifying at least one respiratory event from changes amplitude of the radio frequency interrogation interference signal over the segment.

6. The method of claim 2 wherein the determining step comprises the steps of

dividing the radio frequency interrogation interference signal into time segments containing several cardiac cycles;

and

determining the at least one respiratory characteristic changes within each cardiac cycle.

7. The method of claim 1 wherein the determining step comprises the steps of:

identifying the at least one characteristic from changes in slope of the radio frequency interrogation interference signal over the at least one cycle.

8. The method of claim 1 wherein the determining step comprises the steps of:

dividing the radio frequency interrogation interference signal into time segments containing several cardiac cycles; and

extracting a respiratory cycle component from each of the cardiac cycles of a first segment to provide a resultant cardiac component of the radio frequency interrogation interference signal over the first segment; and

determining at least one cardiac characteristic from the resultant cardiac component of the first segment of the radio frequency interrogation interference signal.

9. The method of claim 7 further comprising the step of deriving at least one cardiac or respiratory characteristic from within each cardiac cycle of the resultant cardiac component of the first segment.

10. The method of claim 8 further comprising the steps of:

deriving the at least one characteristic from another cardiac component of a second segment of the radio frequency interrogation interference signal; and

comparing the derived characteristics from the first and second segments to identify changes.

11. The method of claim 8 further comprising the steps of:

dividing the radio frequency interrogation interference signal into time segments, each time segment containing at least one respiratory cycle; and

extracting a respiratory cycle component from a first segment of the radio frequency interrogation interference signal over the first segment; and

determining at least one cardiac or respiratory characteristic from the resultant respiratory component of the first segment of the radio frequency interrogation interference signal.

12. The method of claim 11 further comprising the steps of:

deriving the at least one characteristic from another respiratory component of a second segment of the radio frequency interrogation interference signal; and

comparing the derived characteristics from the first and second segments to identify changes.

13. The method of claim 1 wherein the determining step comprising calculating at least respiration rate from the radio frequency interrogation interference signal.

14. The method of claim 1 wherein the determining step comprises calculating heart rate of the subject from the radio frequency interrogation interference signal.

15. The method of claim 14, wherein the determining step further comprises the step of calculating a value representative of stroke volume of the subject from the radio frequency interrogation interference signal.

16. The method of claim 15, wherein the determining step further comprises the step of calculating a value representative of cardiac output of the subject from the heart rate and stroke volume.

17. The method of claim 15, further comprises the step of calculating a ratio of change in amplitude with respect to change in time between opposite, sequential extrema in one cardiac cycle of the radio frequency interrogation interference signal.

18. The method of claim 17, further comprising the steps of:

repeating the step of calculating the ratio with respect to several sequential cardiac cycles of the radio frequency interrogation interference; and

averaging the ratios.

19. The method of claim 1, further comprising the step of identifying at least one cardiac or respiratory characteristic within one cardiac cycle of the radio frequency interrogation interference signal.

20. The method of claim 1 further comprising the step of monitoring the characteristic for change over time to identify an overall condition or changes in overall condition or both of the subject.

21. The method of claim 20 further comprising the step of at least periodically outputting a signal related to overall condition to the subject.

22. The method of claim 20 further comprising the step of outputting an alarm signal when overall condition of the subject falls below a predetermined value.

23. The method of claim 20 further comprising the step of quantifying the overall condition of the subject based on the characteristic.

24. The method of claim 23 wherein the quantifying step comprises quantifying cardiac output, stroke volume, respiratory rate, heart rate, a cardiac wave event or other cardiac or respiratory characteristic or some combination of characteristics and further comprising the step of comparing the quantified values with prior values of the subject or with predetermined nominal values applicable widely to subjects.

25. A method of processing cardio-respiratory/pulmonary data obtained by transmission of a radio interrogation signal into a subject torso and capturing reflections of the radio interrogation signal from various tissue of the torso comprising the steps of:

extracting time varying components from the captured reflections of the radio interrogation signal as a radio interrogation impedance signal; and

extracting at least one cyclical cardio-respiratory component from the radio interrogation impedance signal.