PHYSIOLOGICAL PARAMETER MONITORING WITH A MOBILE COMMUNICATION DEVICE

• US 20120190947A1
• Filed: 01/20/2012
• Published: 07/26/2012
• Est. Priority Date: 01/21/2011
• Status: Active Grant

• Current Assignee: Worcester Polytechnic Institute
• Original Assignee: Worcester Polytechnic Institute
• Inventors: Chon, Ki H., Lee, Jinseok, Selvaraj, Nandakumar
• Granted Patent: US 9,713,428 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts

Abstract

Systems and methods that enable physiological monitoring with a mobile communication device and that allow detection of motion artifacts so that the results reported are of acceptable quality are disclosed.

Claims

1. A method for physiological parameter monitoring, the method comprising:

providing a physiological indicator signal to a mobile communication device;

analyzing, using the mobile communications device, the physiological indicator signal to obtain measurements of one or more physiological parameters; and

detecting, using the mobile communications device, effects of motion artifacts in the measurements of the one or more physiological parameters and deciding whether to retain the measurements.

2. The method of claim 1 wherein the step of detecting effects of motion artifacts in the measurements comprises:

a. preprocessing a segment from the measurement of one physiological parameter;

b. obtaining a value of at least one indicator of volatility for the preprocessed segment;

c. including the segment in analyses of physiological measurements, if comparison of the value of the at least one indicator of volatility with a predetermined threshold indicates noise/motion artifacts are not present; and

d. selecting another segment of the signal from the physiological measurement and proceeding to step (a), if the value of the at least one indicator of volatility is less than a predetermined threshold and another segment is available.

3. The method of claim 2 wherein said at least one indicator of volatility comprises kurtosis.

4. The method of claim 2 wherein said at least one indicator of volatility comprises Shannon entropy.

5. The method of claim 2 wherein said at least one measure of volatility comprises kurtosis and Shannon entropy.

6. The method of claim 2 wherein the predetermined threshold is determined using receiver operator characteristic (ROC) analysis.

7. The method of claim 1 wherein providing a physiological indicator signal comprises:

placing a portion of a subject'"'"'s body over an objective lens of a camera in a mobile communication device; and

obtaining video images of the portion of the subject'"'"'s body.

8. The method of claim 1 wherein providing a physiological indicator signal comprises obtaining a signal from a physiological monitoring sensor.

9. The method of claim 8 wherein the physiological monitoring sensor is a photoplethysmographic (PPG) sensor or an electrocardiogram sensor.

10. The method of claim 1 wherein the one or more physiological measurements comprise heart rate and heart rate variability.

11. The method of claim 10 wherein obtaining measurements of heart rate and heart rate variability comprise:

determining beats for the physiological indicator signal;

determining beat to beat intervals; and

applying a cubic spline algorithm to obtain a substantially continuous beat to beat interval signal indicative of heart rate.

12. The method of claim 1 wherein the one or more physiological measurements comprise respiratory rate.

13. The method of claim 12 wherein measurement of respiratory rate comprises:

obtaining time-frequency spectrum of the physiological indicator signal utilizing variable frequency complex demodulation (VFCDM); and

obtaining respiratory rates by extracting a frequency component that has a largest amplitude for each time point at a heart rate frequency band.

14. The method of claim 1 wherein the one or more physiological measurements comprise a measure of oxygen saturation.

15. The method of claim 14 wherein providing a physiological indicator signal comprises:

placing a portion of a subject'"'"'s body over an objective lens of a camera in a mobile communication device; and

obtaining video images of the portion of the subject'"'"'s body, and

wherein obtaining the measure of oxygen saturation comprises;

obtaining an average intensity of a red component and a blue component of the video images of the portion of the subject'"'"'s body;

the average intensity of the red component and the average intensity of the blue component constituting DC_RED and DC_BLUE respectively;

obtaining a standard deviation of the red component and the blue component;

the standard deviation of the red component and the blue component constituting AC_RED and AC_BLUE respectively; and

obtaining the measure of oxygen saturation (SpO2) by

16. The method of claim 1 wherein the one or more physiological measurements comprise a measure of blood loss.

17. The method of claim 16 wherein obtaining the measure of blood loss comprises:

obtaining time-frequency spectrum of the physiological indicator signal utilizing variable frequency complex demodulation (VFCDM);

obtaining the amplitude modulation (AM) series from a set of the largest instantaneous amplitude at each time sample within the heart rate frequency band of the time-frequency spectrum; and

determining whether the amplitude modulation decreases;

a decrease in the amplitude modulation indicating blood volume loss in subject.

18. The method of claim 1 wherein the one or more physiological measurements comprise a measure of atrial fibrillation.

19. The method of claim 18 wherein obtaining the measure of atrial fibrillation comprises:

obtaining a time-varying coherence function by multiplying two time-varying transfer functions (TVFTs), the two time-varying transfer functions obtained using two adjacent data segments with one data segment as input signal and the other data segment as output to produce the first TVTF;

the second TVTF is produced by reversing the input and output signals; and

determining whether the time-varying coherence function is less than a predetermined quantity.

20. The method of claim 19 wherein determining whether the time-varying coherence function is less than the predetermined quantity comprises:

obtaining one or more indicators of atrial fibrillation; and

determining whether the one or more indicators of atrial fibrillation exceed predetermined thresholds.

21. The method of claim 20 wherein the one or more indicators of atrial fibrillation comprise a variance of the time-varying coherence function.

22. The method of claim 21 wherein the one or more indicators of atrial fibrillation also comprise Shannon entropy.

23. The method of claim 20 wherein the predetermined thresholds are determined using receiver operator characteristic (ROC) analysis.

24. A system for physiological parameter monitoring, the system comprising:

a physiological indicator signal sensing component; and

a mobile communication device comprising;

an analysis component analyzing the physiological indicator signal to obtain measurements of one or more physiological parameters; and

a motion artifact detection component detecting effects of motion artifacts in the measurements of the one or more physiological parameters.

25. The system of claim 24 wherein the mobile communications device comprises:

at least one processor; and

at least one computer usable medium, the computer usable medium having computer readable code embodied therein, the computer readable code causing the at least one processor to;

analyze the physiological indicator signal to obtain measurements of one or more physiological parameters; and

detect effects of motion artifacts in the measurements of the one or more physiological parameters.

26. The system of claim 25 wherein the computer readable code, in causing the at least one processor to detect effects of motion artifacts, causes the at least one processor to:

a. preprocess a segment from the measurement of one physiological parameter;

b. obtain a value of at least one indicator of volatility for the preprocessed segment;

c. include the segment in analyses of physiological measurements, if comparison of the value of the at least one indicator of volatility with a predetermined threshold indicates noise/motion artifacts are not present;

d. select another segment of the signal from the physiological measurement and proceeding to step (a), if the value of the at least one indicator of volatility is less than a predetermined threshold and another segment is available.

27. The system of claim 26 wherein said at least one indicator of volatility comprises kurtosis.

28. The system of claim 26 wherein said at least one indicator of volatility comprises Shannon entropy.

29. The system of claim 26 wherein said at least one measure of volatility comprises kurtosis and Shannon entropy.

30. The system of claim 26 wherein the predetermined threshold is determined using receiver operator characteristic (ROC) analysis.

31. The system of claim 24 wherein the physiological indicator signal sensing component comprises an image acquisition component, said acquisition component capable of acquiring a number of frames, each frame acquired at a predetermined time.

32. The system of claim 31 wherein the mobile communications device comprises said image acquisition component.

33. The system of claim 24 wherein the physiological indicator signal sensing component comprises a physiological monitoring sensor.

34. The system of claim 33 wherein the physiological monitoring sensor is a photoplethysmographic (PPG) sensor or an electrocardiogram sensor.

35. The system of claim 25 wherein the physiological indicator signal sensing component comprises an image acquisition component, said acquisition component capable of acquiring a number of frames, each frame acquired at a predetermined time;

wherein said image acquisition component acquires a color image having red, green and blue components;

wherein one or more physiological measurements comprise a measure of oxygen saturation; and

wherein the computer readable code, in causing the at least one processor to analyze the physiological indicator signal, causes the at least one processor to;

obtain an average intensity of a red component and a blue component of the images of a portion of a subject'"'"'s body;

the average intensity of the red component and the average intensity of the blue component constituting DC_RED and DC_BLUE respectively;

obtain a standard deviation of the red component and the blue component;

the standard deviation of the red component and the blue component constituting AC_RED and AC_BLUE respectively; and

obtain the measure of oxygen saturation by

36. The system of claim 25 wherein the one or more physiological measurements comprise heart rate and heart rate variability;

and wherein the computer readable code, in causing the at least one processor to analyze the physiological indicator signal, causes the at least one processor to;

determine beats for the physiological indicator signal;

determine beat to beat intervals; and

apply a cubic spline algorithm to obtain a substantially continuous beat to beat interval signal indicative of heart rate.

37. The system of claim 25 wherein the one or more physiological measurements comprise respiratory rate;

and wherein the computer readable code, in causing the at least one processor to analyze the physiological indicator signal, causes the at least one processor to;

obtain time-frequency spectrum of the physiological indicator signal utilizing variable frequency complex demodulation (VFCDM); and

obtain respiratory rates by extracting a frequency component that has a largest amplitude for each time point at a heart rate frequency band.

38. The system of claim 25 wherein the one or more physiological measurements comprise a measure of blood loss;

and wherein the computer readable code, in causing the at least one processor to analyze the physiological indicator signal, causes the at least one processor to;

obtain time-frequency spectrum of the physiological indicator signal utilizing variable frequency complex demodulation (VFCDM);

obtain the amplitude modulation (AM) series from set of the largest instantaneous amplitude at each time sample within the heart rate frequency band of the time-frequency spectrum; and

determine whether the amplitude modulation decreases;

a decrease in the amplitude modulation indicating blood volume loss in subject.

39. The system of claim 25 wherein the one or more physiological measurements comprise a measure of atrial fibrillation;

and wherein the computer readable code, in causing the at least one processor to analyze the physiological indicator signal, causes the at least one processor to;

obtain a time-varying coherence function by multiplying two time-varying transfer functions (TVFTs), the two time-varying transfer functions obtained using two adjacent data segments with one data segment as input signal and the other data segment as output to produce the first TVTF;

the second TVTF is produced by reversing the input and output signals; and

determine whether the time-varying coherence function is less than a predetermined quantity.

40. The system of claim 39 wherein the computer readable code, in causing the at least one processor to determine whether the time-varying coherence function is less than the predetermined quantity, causes the at least one processor to:

obtain one or more indicators of atrial fibrillation; and

determine whether the one or more indicators of atrial fibrillation exceed predetermined thresholds.

41. The system of claim 40 wherein the one or more indicators of atrial fibrillation comprise a variance of the time-varying coherence function.

42. The system of claim 41 wherein the one or more indicators of atrial fibrillation also comprise Shannon entropy.

43. The system of claim 41 wherein the predetermined thresholds are determined using receiver operator characteristic (ROC) analysis.

44. A computer usable medium having computer readable code embodied therein, the computer readable code causing at least one processor to:

analyze a physiological indicator signal to obtain measurements of one or more physiological parameters; and

detect effects of motion artifacts in the measurements of the one or more physiological parameters.

45. The computer usable medium of claim 44 wherein the physiological indicator signal comprises a video color image having red, green and blue components, the video color image being an image obtained from of a portion of a subject'"'"'s body;

wherein the measurements of one or more physiological parameters comprise a measure of oxygen saturation; and

wherein the computer readable code, in causing the at least one processor to analyze the physiological indicator signal, causes the at least one processor to;

obtain an average intensity of the red component and a blue component of the video color image of a portion of a subject'"'"'s body;

the average intensity of the red component and the average intensity of the blue component constituting DC_RED and DC_BLUE respectively;

obtain a standard deviation of the red component and the blue component;

the standard deviation of the red component and the blue component constituting AC_RED and AC_BLUE respectively; and

obtain the measure of oxygen saturation by

46. The computer usable medium of claim 44 wherein the one or more physiological measurements comprise heart rate and heart rate variability;

and wherein the computer readable code, in causing the at least one processor to analyze the physiological indicator signal, causes the at least one processor to;

determine beats for the physiological indicator signal;

determine beat to beat intervals; and

apply a cubic spline algorithm to obtain a substantially continuous beat to beat interval signal indicative of heart rate.

47. The computer usable medium of claim 44 wherein the one or more physiological measurements comprise respiratory rate;

and wherein the computer readable code, in causing the at least one processor to analyze the physiological indicator signal, causes the at least one processor to;

obtain time-frequency spectrum of the physiological indicator signal utilizing variable frequency complex demodulation (VFCDM); and

obtain respiratory rates by extracting a frequency component that has a largest amplitude for each time point at a heart rate frequency band.

48. The computer usable medium of claim 44 wherein the one or more physiological measurements comprise a measure of blood loss;

and wherein the computer readable code, in causing the at least one processor to analyze the physiological indicator signal, causes the at least one processor to;

obtain time-frequency spectrum of the physiological indicator signal utilizing variable frequency complex demodulation (VFCDM);

obtain the amplitude modulation (AM) series from set of the largest instantaneous amplitude at each time sample within the heart rate frequency band of the time-frequency spectrum; and

determine'"'"'whether the amplitude modulation decreases;

a decrease in the amplitude modulation indicating blood volume loss in subject.

49. The computer usable medium of claim 44 wherein the one or more physiological measurements comprise a measure of atrial fibrillation;

and wherein the computer readable code, in causing the at least one processor to analyze the physiological indicator signal, causes the at least one processor to;

obtain a time-varying coherence function by multiplying two time-varying transfer functions (TVFTs), the two time-varying transfer functions obtained using two adjacent data segments with one data segment as input signal and the other data segment as output to produce the first TVTF;

the second TVTF is produced by reversing the input and output signals; and

determine whether the time-varying coherence function is less than a predetermined quantity.

50. The computer usable medium of claim 44 wherein the computer readable code, in causing the at least one processor to determine whether the time-varying coherence function is less than the predetermined quantity, causes the at least one processor to:

obtain one or more indicators of atrial fibrillation;

determine whether the one or more indicators of atrial fibrillation exceed predetermined thresholds.

51. The computer usable medium of claim 50 wherein the one or more indicators of atrial fibrillation comprise a variance of the time-varying coherence function.

52. The computer usable medium of claim 51 wherein the one or more indicators of atrial fibrillation also comprise Shannon entropy.

53. The computer usable medium of claim 50 wherein the predetermined thresholds are determined using receiver operator characteristic (ROC) analysis.