ESTIMATION OF BLOOD FLOW AND HEMODYNAMIC PARAMETERS FROM A SINGLE CHEST-WORN SENSOR, AND OTHER CIRCUITS, DEVICES AND PROCESSES

• US 20110066042A1
• Filed: 08/24/2010
• Published: 03/17/2011
• Est. Priority Date: 09/15/2009
• Status: Abandoned Application

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Cole, Edwin Randolph, Ravindran, Sourabh, Pandia, Keya R.
• Application Number:
  US12/861,888
• Publication Number:
  US 20110066042A1
• Time in Patent Office: Days
• US Class Current: 600/484
• CPC Class Codes: A61B 2505/07 Home care
• CPC Class Codes: A61B 2560/0475 Special features of memory means, e.g. removable memory cards
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• 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 5/1102 Ballistocardiography
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• 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 7/00 Instruments for auscultation
• CPC Class Codes: A61B 7/008 Detecting noise of gastric tract, e.g. caused by voiding

Abstract

An electronic monitoring device includes an electronic processor (520) having at least one signal input for body monitoring, and a memory (530) holding instructions for the electronic processor coupled to the electronic processor so that the electronic processor is operable to isolate a cardiac signal including cardiac pulses combined with other cardiac signal variations, and the electronic processor further operable to execute a filter (730) that separates a varying blood flow signal from the cardiac pulses and to output information (790) based on at least the varying blood flow signal. Other devices, sensor assemblies, electronic circuit units, and processes are also disclosed.

Claims

1. An electronic monitoring device comprising:

an electronic processor having at least one signal input for body monitoring; and

a memory holding instructions for said electronic processor coupled to said electronic processor so that said electronic processor is operable to isolate a cardiac signal including cardiac pulses combined with other cardiac signal variations, and said electronic processor further operable to execute a filter that separates a varying blood flow signal from the cardiac pulses and to output information based on at least the varying blood flow signal.

2. The electronic monitoring device claimed in claim 1 wherein said electronic processor is operable to also separate cardiac pulses from the cardiac signal and produce an electronic representation of a time interval between a selected cardiac pulse and an event on the varying blood flow signal.

3. The electronic monitoring device claimed in claim 2 wherein the selected cardiac pulse is an S1 pulse.

4. The electronic monitoring device claimed in claim 2 wherein the event is a peak in the varying blood flow signal after the selected cardiac pulse.

5. The electronic monitoring device claimed in claim 2 wherein said electronic processor is operable to produce a measurement of jitter across heart beats of the time interval.

6. The electronic monitoring device claimed in claim 1 wherein said electronic processor is operable to output an electronic representation of iso-volumic contraction interval using the varying blood flow signal.

7. The electronic monitoring device claimed in claim 6 wherein said electronic processor is operable to produce an electronic representation of contractility using the iso-volumic contraction interval.

8. The electronic monitoring device claimed in claim 1 wherein the filter for said blood flow signal passes an oscillatory cardiac signal component and substantially rejects cardiac S1 and S2 signal peaks, thereby to separate the varying blood flow signal.

9. The electronic monitoring device claimed in claim 1 wherein the filter for said blood flow signal smoothes the cardiac signal using a low-order polynomial filter with a time window approximately comparable in size to a period of oscillation of the varying blood flow signal.

10. The electronic monitoring device claimed in claim 9 wherein said electronic processor is operable to subtract from the cardiac signal the result of the smoothing filter to deliver a residue signal primarily featuring the cardiac pulses separated from the cardiac signal.

11. The electronic monitoring device claimed in claim 10 wherein said electronic processor is operable to count the cardiac pulses to deliver a heart rate signal.

12. The electronic monitoring device claimed in claim 1 wherein the filter for said blood flow signal smooths the cardiac signal using an approximately-4th order Savitzky-Golay polynomial filter with a window size approximately 200 milliseconds.

13. The electronic monitoring device claimed in claim 1 wherein said electronic processor is operable to digitally low pass filter an input thereof with a cutoff lower than a power line frequency to isolate the cardiac signal.

14. The electronic monitoring device claimed in claim 1 further comprising at least two analog signal paths coupled to said electronic processor, each analog signal path including an AC coupled amplifier feeding a low pass anti-alias filter feeding a sampling analog-to-digital converter coupled to said electronic processor.

15. The electronic monitoring device claimed in claim 1 wherein the filter for said blood flow signal smoothes the cardiac signal using a low-order polynomial filter to obtain the varying blood flow signal, and said electronic processor instructions also define a substantially higher-order polynomial filter concurrently operable to deliver a residue signal having cardiac pulses.

16. The electronic monitoring device claimed in claim 1 wherein the electronic processor is further operable to perform electronic peak detection on the varying blood flow signal to identify a flow peak amplitude and a time location F1 of that peak.

17. The electronic monitoring device claimed in claim 16 wherein the electronic processor is further operable to separate the cardiac pulses and identify their first peak location in time P1 for a same heart beat as applies to the time location F1.

18. The electronic monitoring device claimed in claim 17 wherein the electronic processor is further operable to generate a hemodynamic parameter based on the time difference between time P1 and the time F1.

19. The electronic monitoring device claimed in claim 17 wherein the electronic processor is further operable to generate beat-by-beat values of the time difference between time P1 of the peak of an S1 cardiac pulse and the time F1 of the peak of the varying blood flow signal.

20. The electronic monitoring device claimed in claim 19 wherein said electronic processor is further operable to derive a respiration-related signal from variations in the beat-by-beat values of the time difference.

21. The electronic monitoring device claimed in claim 1 wherein said electronic processor is further operable to perform electronic peak detection on the varying blood flow signal to identify a flow peak amplitude PAmp and generate a hemodynamic parameter as a function of the flow peak amplitude PAmp.

22. The electronic monitoring device claimed in claim 21 wherein said electronic processor is further operable to derive a signal, related to at least one of respiration, intrapleural pressure, and intrathoracic pressure, from variations in beat-by-beat values of the flow peak amplitude PAmp.

23. The electronic monitoring device claimed in claim 21 wherein said electronic processor is further operable to obtain the cardiac pulses and a heart rate HR therefrom, and further to generate a hemodynamic parameter as a function of the flow peak amplitude PAmp times the heart rate HR.

24. The electronic monitoring device claimed in claim 1 further comprising a modem coupled to said electronic processor.

25. The electronic monitoring device claimed in claim 24 wherein said modem is selected from the group consisting of:

1) cellular,

     2) Wi-Fi,

     3) wireline,

     4) telephone modem.

26. The electronic monitoring device claimed in claim 1 wherein said electronic processor is also operable to substantially filter out baseline-wander below about one-half Hertz from the blood flow signal.

27. An accelerometer sensor assembly having a broadside portion and comprising

an accelerometer sensor circuit having an axis of acceleration sensitivity parallel to the broad side and orientable on the chest to deliver an input signal representing a component of acceleration approximately parallel to a head-to-feet body axis and including heart pulses and other variations mixed together;

an electronic circuit responsive to said accelerometer sensor circuit and operable to execute a filter that delivers a varying blood flow signal from said input signal at least when that axis of acceleration sensitivity is approximately parallel to the head-to-feet body axis, the varying blood flow signal substantially freed of heart pulses; and

an output circuit operable to send information based on the varying blood flow signal.

28. The accelerometer sensor assembly claimed in claim 27 further comprising a display coupled to said electronic circuit.

29. The accelerometer sensor assembly claimed in claim 27 wherein said accelerometer sensor circuit has a second axis of acceleration sensitivity substantially perpendicular to the broad side and orientable on the chest to deliver a second input signal to said electronic circuit representing a component of acceleration approximately parallel to a dorsal-ventral direction.

30. The accelerometer sensor assembly claimed in claim 27 wherein said accelerometer sensor circuit has another axis of acceleration sensitivity substantially parallel to the broad side and substantially perpendicular to the first-recited axis of acceleration sensitivity, and the electronic circuit coupled to receive another input signal from said accelerometer sensor circuit representing that other axis of acceleration sensitivity.

31. The accelerometer sensor assembly claimed in claim 30 wherein said electronic circuit is operable to combine signals from said accelerometer sensor circuit representing at least both of those axes of acceleration sensitivity.

32. The accelerometer sensor assembly claimed in claim 27 further comprising an electrode for electrical skin contact and made physically part of the assembly.

33. The accelerometer sensor assembly claimed in claim 27 wherein said accelerometer sensor circuit includes at least two analog signal conditioning paths.

34. The accelerometer sensor assembly claimed in claim 27 wherein the varying blood flow signal has a spindle-shaped oscillatory waveform during each heartbeat and oscillating at a frequency higher than both a respiration frequency and a heart rate.

35. The accelerometer sensor assembly claimed in claim 27 wherein said output circuit includes a modem coupled to said electronic circuit.

36. The accelerometer sensor assembly claimed in claim 27 wherein said output circuit is selected from the group consisting of:

1) Bluetooth,

     2) Zigbee,

     3) serial interface.

37. The accelerometer sensor assembly claimed in claim 27 wherein said electronic circuit is operable to provide a hemodynamic parameter, a heart rate, and a respiration parameter, all based on said accelerometer sensor circuit.

38. An electronic monitoring process comprising:

electronically bandpassing digital signals representing living-body monitoring signals in a range selective for a cardiac signal; and

executing a filter that delivers a varying blood flow signal from the cardiac signal.

39. The electronic monitoring process claimed in claim 38 further comprising separating cardiac pulses from the cardiac signal and delivering an electronic representation of the time interval between a cardiac pulse and an event on the varying blood flow signal.

40. The electronic monitoring process claimed in claim 38 further comprising post-processing the varying blood flow signal as from a 2nd order system model.

41. The electronic monitoring process claimed in claim 38 further comprising post-processing the varying blood flow signal and the cardiac signal into electronically-represented displays of physiological function.

42. A hemodynamic monitoring device comprising:

an electronic processor having at least one signal input for body monitoring; and

a memory holding instructions for said electronic processor coupled to said electronic processor so that said electronic processor is operable to obtain a cardiac pulse signal having a varying amplitude, and said electronic processor further operable to post-process the cardiac pulse signal to provide a time-varying output representing an estimation for at least one hemodynamic parameter based on the amplitude and selected from the group consisting of stroke volume SV and cardiac output CO.

43. The hemodynamic monitoring device claimed in claim 42 wherein said electronic processor is also operable to separate a respiration signal also based on the amplitude from the cardiac pulse signal.

44. The hemodynamic monitoring device claimed in claim 42 further comprising a display coupled to said electronic processor to display the at least one hemodynamic parameter.