Method of assesing blood volume using photoelectric plethysmography

• US 20070032732A1
• Filed: 01/02/2004
• Published: 02/08/2007
• Est. Priority Date: 03/12/2003
• Status: Active Grant

• Current Assignee: Adam J. Shelley, David G. Silverman, Kirk H. Shelley
• Original Assignee: Yale University
• Inventors: Silverman, David, Shelley, Adam, Stout, Robert, Shelley, Kirk
• Granted Patent: US 8,251,912 B2
• Time in Patent Office: Days
• US Class Current: 600/504
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• 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 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• 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 5/7405 using sound
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes 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
• CPC Class Codes: G16H 10/40 for data related to laboratory analysis, e.g. patient specimen analysis
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

A method and system for assessing blood volume within a subject includes generating a cardiovascular waveform representing physiological characteristics of a subject and determining blood volume of the subject by analyzing the cardiovascular waveform. The step of analyzing includes generating a first trace of the per heart-beat maximums of the cardiovascular waveform, which is representative of the systolic pressure upon the cardiovascular signal, generating a second trace of the per heart-beat minimums of the cardiovascular waveform, which is representative of the diastolic pressure upon the cardiovascular signal, and comparing the respective first trace and the second trace to generate an estimate of relative blood volume within the subject. In accordance with an alternate method of analyzing harmonic analysis is applied to the cardiovascular waveform, extracting a frequency signal created by ventilation and applying the extracted frequency signal in determining blood volume of the subject.

Claims

1. A method for assessing blood volume within a subject, comprising:

generating a cardiovascular waveform representing physiological characteristics of a subject;

determining blood volume of the subject by analyzing the cardiovascular waveform, wherein the step of analyzing includes;

generating a first trace of the per heart-beat maximums of the cardiovascular waveform, which is representative of the systolic pressure upon the cardiovascular signal;

generating a second trace of the per heart-beat minimums of the cardiovascular waveform, which is representative of the diastolic pressure upon the cardiovascular signal;

comparing the respective first trace and the second trace to generate an estimate of relative blood volume within the subject.

2. The method according to claim 1, wherein the cardiac waveform is a pulse oximeter waveform representing effective blood volume.

3. The method according to claim 1, wherein the step of comparing includes comparing the amplitude or phase shift of the respective first trace and the second trace to generate an estimate of blood volume within the subject.

4. The method according to claim 1, wherein the cardiovascular waveform is a photoelectric plethysmographic waveform.

5. The method according to claim 1, wherein the oscillations of the cardiovascular waveform are representative of ventilatory fluctuations in the subject.

6. The method according to claim 1, wherein the first trace and the second trace are generated by respectively recording the per heart-beat maximums and per heart-beat minimums of the cardiovascular waveform during ventilation by the subject.

7. The method according to claim 1, wherein a determination that the first trace and the second trace are in-phase with low amplitude is indicative of no blood loss.

8. The method according to claim 1, wherein the degree of phase shift between the first trace and the second trace is indicative of increased blood loss.

9. The method according to claim 1, wherein amplitudes of the first trace and the second trace increase proportionally with the degree of blood loss.

10. The method according to claim 1, wherein the step of comparing includes taking an average between the per heart-beat minimums and the per heart-beat maximums as an indicator of an effect upon the arterial system.

11. The method according to claim 1, wherein the step of comparing includes studying the phase shift between the first trace and the second trace to determine a degree of ventilatory augmentation as compared to dampening of cardiac output.

12. The method according to claim 1, wherein subject ventilation is controlled at a constant rate by mechanical ventilation.

13. The method according to claim 1, wherein subject ventilation is controlled by manually squeezing of a ventilation bag.

14. The method according to claim 1, wherein subject ventilation is synchronized with a metronome.

15. A method for assessing blood volume within a subject, comprising:

generating a cardiovascular waveform representing physiological characteristics of a subject;

determining effective blood volume of the subject by analyzing the cardiovascular waveform, wherein the step of analyzing includes;

applying harmonic analysis to the cardiovascular waveform;

extracting a frequency signal created by ventilation; and

applying the extracted frequency signal in determining blood volume of the subject.

16. The method according to claim 15, wherein the cardiovascular waveform is a pulse oximeter waveform.

17. The method according to claim 15, wherein the harmonic analysis is Fourier analysis.

18. The method according to claim 15, wherein the Fourier analysis is joint time-frequency analysis.

19. The method according to claim 18, wherein the joint time-frequency analysis is a short-time Fourier transformation.

20. The method according to claim 15, wherein the extraction of the frequency signal is achieved using a peak detection algorithm.

21. The method according to claim 20, wherein the peak detection algorithm is applied in the frequency range of ventilation.

22. The method according to claim 15, wherein the cardiovascular waveform is a photoelectric plethysmographic waveform of a pulse oximeter.

23. The method according to claim 15, wherein the oscillations of the cardiovascular waveform are representative of ventilatory fluctuations in the subject.

24. The method according to claim 15, wherein the step of determining blood volume includes monitoring the respiratory frequency to ascertain changes in the venous component of blood volume.

25. The method according to claim 15, wherein the step of determining blood volume includes monitoring the development of secondary harmonics surrounding a pulse harmonic to ascertain changes in the arterial component of the blood volume.

26. The method according to claim 15, wherein subject ventilation is synchronized with a metronome.

27. A method for assessing a cardiovascular waveform, comprising:

generating a first trace of the per heart-beat maximums of the cardiovascular waveform;

generating a second trace of the per heart-beat minimums of the cardiovascular waveform;

comparing the respective first trace and the second trace to generate physiological characteristics of a subject.

28. The method according to claim 27, wherein the step of comparing includes comparing the amplitude and phase shift of the respective first trace and the second trace.

29. The method according to claim 27, wherein the oscillations of the cardiovascular waveform are representative of ventilatory impact on the subject.

30. The method according to claim 27, wherein the first trace and the second trace are generated by respectively recording the per heart-beat maximums and per heart-beat minimums of the cardiovascular waveform during ventilation by the subject.

31. The method according to claim 27, wherein a determination that the first trace and the second trace are in-phase with low amplitude is indicative of no blood loss.

32. The method according to claim 27, wherein the degree of phase shift between the first trace and the second trace is indicative of increased blood loss.

33. The method according to claim 27, wherein amplitudes of the first trace and the second trace increase proportionally with the degree of blood loss.

34. The method according to claim 27, wherein the step of comparing includes ting an average between the per heart-beat minimums and the per heart-beat maximums as an indicator of an effect upon the arterial system.

35. The method according to claim 27, wherein the step of comparing includes studying the phase shift between the first trace and the second trace to determine a degree of ventilatory augmentation as compared to dampening of cardiac output.

36. The method according to claim 27, wherein subject ventilation is synchronized with a metronome.

37. A method for assessing a cardiovascular waveform, comprising:

applying harmonic analysis to the cardiovascular waveform;

extracting a frequency signal created by ventilation; and

applying the extracted frequency signal in determining physiological characteristics of a subject.

38. The method according to claim 37, wherein the harmonic analysis is Fourier analysis.

39. The method according to claim 38, wherein the Fourier analysis is joint time-frequency analysis.

40. The method according to claim 39, wherein the joint time-frequency analysis is a short-time Fourier transformation.

41. The method according to claim 37, wherein the extraction of the frequency signal is achieved using a peak detection algorithm.

42. The method according to claim 41, wherein the peak detection algorithm is applied in the frequency range of ventilation.

43. The method according to claim 37, wherein the cardiovascular waveform is a photoelectric plethysmographic waveform.

44. The method according to claim 37, wherein the oscillations of pulse oximeter waveform are representative of ventilatory fluctuation in the subject.

45. The method according to claim 37, wherein subject ventilation is synchronized with a metronome.

46. A system for assessing blood volume within a subject, comprising:

a probe adapted for retrieving cardiovascular waveforms of a subject; and

a processor associated with the probe for analyzing the retrieved cardiovascular waveforms, the processor including means for determining blood volume of the subject by analyzing the cardiovascular waveform, wherein the step of analyzing includes;

generating a first trace of the per heart-beat maximums of the cardiovascular waveform, which is representative of the systolic pressure upon the cardiovascular signal;

generating a second trace of the per heart-beat minimums of the cardiovascular waveform, which is representative of the diastolic pressure upon the cardiovascular signal;

comparing the respective first trace and the second trace to generate an estimate of relative blood volume within the subject.

47. The system according to claim 46, wherein the probe is a pulse oximeter probe and the cardiac waveform is a pulse oximeter waveform representing effective blood volume.

48. The system according to claim 46, wherein the step of comparing includes comparing the amplitude and phase shift of the respective first trace and the second trace to generate an estimate of blood volume within the subject.

49. The system according to claim 46, wherein the first trace and the second trace are generated by respectively recording the per heart-beat maximums and per heart-beat minimums of the pulse oximeter waveform during ventilation by the subject.

50. The system according to claim 46, wherein a determination that the first trace and the second trace are in-phase with low amplitude is indicative of no blood loss.

51. The system according to claim 46, wherein the degree of phase shift between the first trace and the second trace is indicative of increased blood loss.

52. The system according to claim 46, wherein amplitudes of the first trace and the second trace increase proportionally with the degree of blood loss.

53. The system according to claim 46, wherein the step of comparing includes taking an average between the per heart-beat minimums and the per heart-beat maximums as an indicator of an affect upon the arterial system.

54. The system according to claim 46, wherein the step of comparing includes studying the phase shift between the first trace and the second trace to determine a degree of ventilatory augmentation as compared to dampening of cardiac output.

55. The system according to claim 46, wherein subject ventilation is synchronized with a metronome.

56. A system for assessing blood volume within a subject, comprising:

a probe adapted for retrieving cardiovascular waveforms of a subject; and

a processor associated with the probe for analyzing the retrieved cardiovascular waveforms, the processor including means for determining blood volume of the subject by analyzing the cardiovascular waveform, wherein the step of analyzing includes;

applying harmonic analysis to the cardiovascular waveform;

extracting a frequency signal created by ventilation; and

applying the extracted frequency signal in determining blood volume of the subject.

57. The system according to claim 56, wherein the probe is a pulse oximeter probe and the cardiovascular waveform is a pulse oximeter waveform.

58. The system according to claim 56, wherein the harmonic analysis is Fourier analysis.

59. The system according to claim 58, wherein the Fourier analysis is joint time-frequency analysis.

60. The system according to claim 59, wherein the joint time-frequency analysis is a short-time Fourier transformation.

61. The system according to claim 56, wherein the extraction of the frequency signal is achieved using a peak detection algorithm.

62. The system according to claim 61, wherein the peak detection algorithm is applied in the frequency range of ventilation.

63. The system according to claim 56, wherein the step of determining blood volume includes monitoring the respiratory frequency to ascertain changes in the venous component of blood volume.

64. The system according to claim 56, wherein the step of determining blood volume includes monitoring the development of secondary harmonics surrounding a pulse harmonic to ascertain changes in the arterial component of the blood volume.

65. The system according to claim 56, wherein subject ventilation is synchronized with a metronome.