System for measuring respiratory function

• US 6,287,264 B1
• Filed: 04/23/1999
• Issued: 09/11/2001
• Est. Priority Date: 04/23/1999
• Status: Active Grant

• Current Assignee: Trustees of Tufts College
• Original Assignee: Trustees of Tufts College
• Inventors: Hoffman, Andrew
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US09/298,352
• Time in Patent Office: 872 Days
• Field of Search: 600/529, 600/534, 600/538
• US Class Current: 600/538
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/085 Measuring impedance of respiratory organs or lung elasticity
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/1135 by monitoring thoracic expansion
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61D 99/00 Subject matter not provided for in other groups of this subclass

Abstract

The present invention relates to a system for measuring respiratory function of living organisms. More particularly, signals indicative of the effort, defined as active and passive work, required to breathe and the airflow through the respiratory system of the living organism are obtained and processed as waveforms to provide a signal indicative of the respiratory restriction. The methods of the present invention measure clinical forms of airway obstruction and airway reactivity and may be used to continuously or intermittently monitor patients with compromised respiratory function.

Claims

1. A method for measuring respiration function of a living organism, comprising the steps:

obtaining a first input signal from a first sensor indicative of a change in lung volume during breathing by said living organism;

obtaining a second input signal from a second sensor indicative of airflow through the respiratory system of said living organism during the change in lung volume; and

processing said first input signal and said second input signal to calculate a third signal indicative of respiratory restriction of said living organism.

2. The method according to claim 1, wherein the processing step comprises the step of comparing said first input signal to said second input signal.

3. The method according to claim 2, wherein the step of comparing said first and second input signals comprises analyzing phase and magnitude differences between said first and second signals in the same time domain.

4. The method according to claim 3, further comprises determining the location of respiratory restriction by analyzing whether the phase and magnitude differences occur in one of an inspiratory portion of said first and second signals and an expiratory portion of said first and second signals.

5. The method according to claim 4, wherein the phase and magnitude differences in the inspiratory portion of said first and second signals indicate a proximal respiration restriction in a region such as the upper airways of the organism.

6. The method according to claim 4, wherein the phase and magnitude differences in the expiratory portion of said first and second signals indicate a distal respiration restriction in a region such as the lower airways of the organism.

7. The method according to claim 3, wherein the step of comparing said first and second input signals further comprises the step of subtracting said second input signal from said first input signal in the same time-domain.

8. The method according to claim 1, further comprising of obtaining the first input signal through use of respiratory induction plethysmography.

9. The method according to claim 1, further comprising of obtaining the first input signal through use of a piezoelectric device.

10. The method according to claim 1, further comprising of obtaining the second input signal through use of a pneumotachographic measurement device.

11. The method according to claim 1, further comprising the step of calibrating first input signal.

12. The method according to claim 1, further comprising the step of displaying said first input signal and said first second input signal as digital waveforms.

13. The method according to claim 1, further comprising the steps of:

obtaining a signal through respiratory inductance plethysmography of a chest of said living organism;

obtaining a signal through respiratory inductance plethysmography of an abdomen of said living organism;

summing said chest signal and said abdomen signal to form said first input signal;

converting said first input signal from an analog signal to a digital signal;

taking the derivative of said digital first input signal;

converting said second signal from an analog to a digital signal; and

subtracting said second input signal from said digital derivative of first input signal to obtain said third signal.

14. The method according to claim 13, wherein the steps of converting, an input signal from analog to digital signal, taking the derivative of, converting signal from an analog to digital signal and subtracting said second input signal from digital derivative of first input signal, uses at least one of the signal of the chest, the signal of the abdomen or the first input signal indicative of the sum of the chest and abdomen signal.

15. An apparatus for obtaining a signal indicative of respiration of a living organism, comprising:

a first sensor device that obtains a first input signal indicative of a change in lung volume during breathing by said living organism, the first sensor device including a sensor adapted to be positioned on an external surface of the living organism;

a second sensor device that obtains a second input signal indicative of actual airflow through the respiratory system of said living organism; and

a processing device that processes said first input signal and said second input signal to calculate a third signal indicative of respiration restriction of said living organism.

16. The apparatus according to claim 15, wherein said processing device compares said first input signal from said second input signal to analyze phase and magnitude differences between said input signals.

17. The apparatus according to claim 15, wherein said first device comprises a respiratory inductance plethysmography measurement device.

18. The apparatus according to claim 15, wherein said first device comprises a piezoelectric measurement device.

19. The apparatus according to claim 15, wherein said first device comprises an impedance plethysmography measurement device.

20. The apparatus according to claim 15, wherein said second device comprises a pneumotachographic measurement device.

21. The apparatus according to claim 15, wherein said second device comprises an ultrasonic measurement device.

22. The apparatus according to claim 15, wherein said second device comprises a thermistor measurement device.

23. The apparatus according to claim 15, further comprising a calibration device for calibrating said first input signal.

24. The apparatus according to claim 15, further comprising a calibration device for calibrating said second input signal.

25. The apparatus according to claim 15, further comprising an interface device for providing said first and second input signals to the processing device.

26. The apparatus according to claim 25, wherein the interface device further comprises a summer, a differentiator and a filter.

27. The apparatus according to claim 15, further comprising a device for displaying said first input signal and said second input signal as digital waveforms.

28. The apparatus according to claim 15, further comprising a device for displaying first input signal and said second input signal as analog waveforms.

29. The apparatus of claim 15, wherein the processing device comprises a programmable computer having a memory, the memory having stored referenced data.

30. The apparatus of claim 15, wherein the apparatus weighs less than fifteen (15) pounds.

31. A method for measuring respiration function of a living organism, comprising the steps:

obtaining a first input signal from a first sensor indicative of effort required to breathe by said living organism;

obtaining a second input signal from a second sensor indicative of airflow through the respiratory system of said living organism; and

comparing said first input signal and said second input signal by analyzing phase and magnitude differences between said first and second signals in the same time domain to form a third signal indicative of respiratory restriction of said living organism.

32. The method according to claim 31 further comprises determining the location of respiratory restriction by analyzing whether the phase and magnitude differences occur in one of an inspiratory portion of said first and second signals and an expiratory portion of said first and second signals.

33. The method according to claim 32 wherein the phase and magnitude differences in the expiratory portion of said first and second signals indicate a distal respiration restriction in a region such as the lower airways of the organism.

34. The method according to claim 31 wherein the phase and magnitude differences in the inspiratory portion of said first and second signals indicate a proximal respiration restriction in a region such as the upper airways of the organism.

35. The method according to claim 31 wherein the step of comparing said first and second input signals further comprises the step of subtracting said second input signal from said first input signal in the same time-domain.

36. The method according to claim 31 further comprising of obtaining the first input signal through use of respiratory induction plethysmography.

37. The method according to claim 31 further comprising of obtaining the first input signal through use of a piezoelectric device.

38. The method according to claim 31 further comprising of obtaining the second input signal through use of a pneumotachographic measurement device.

39. The method according to claim 31 further comprising the step of calibrating first input signal.

40. The method according to claim 31 further comprising the step of displaying said first input signal and said first second input signal as digital waveforms.

41. The method according to claim 31 further comprising the steps of.

obtaining a signal through respiratory inductance plethysmography of a chest of said living organism;

obtaining a signal through respiratory inductance plethysmography of an abdomen of said living organism;

summing said chest signal and said abdomen signal to form said first input signal;

converting said first input signal from an analog signal to a digital signal;

taking the derivative of said digital first input signal;

converting said second signal from an analog to a digital signal; and

subtracting said second input signal from said digital derivative of first input signal to obtain said third signal.

42. The method according to claim 41 wherein the steps of converting, an input signal from analog to digital signal, taking the derivative of, converting signal from an analog to digital signal and subtracting said second input signal from digital derivative of first input signal, uses at least one of the signal of the chest, the signal of the abdomen or the first input signal indicative of the sum of the chest and abdomen signal.

43. An apparatus for obtaining a signal indicative of respiration of a living organism, comprising:

a first device that obtains a first input signal indicative of effort required to breathe by said living organism;

a second device that obtains a second input signal indicative of actual airflow through the respiratory system of said living organism;

a processing device that compares said first input signal and said second input signal by analyzing phase and magnitude differences between said first input signal and said second input signal; and

forming a third signal indicative of respiration restriction of said living organism.

44. The apparatus according to claim 43 wherein said first device comprises a respiratory inductance plethysmography measurement device.

45. The apparatus according to claim 43 wherein said first device comprises a piezoelectric measurement device.

46. The apparatus according to claim 43 wherein said first device comprises an impedance plethysmography measurement device.

47. The apparatus according to claim 43 wherein said second device comprises a pneumotachographic measurement device.

48. The apparatus according to claim 43 wherein said second device comprises an ultrasonic measurement device.

49. The apparatus according to claim 43, wherein said second device comprises a thermistor measurement device.

50. The apparatus according to claim 43 further comprising a calibration device for calibrating said first input signal.

51. The apparatus according to claim 43 further comprising a calibration device for calibrating said second input signal.

52. The apparatus of claim 43 further comprising an interface device for providing said first and second input signals to the processing device.

53. The apparatus of claim 43 wherein the interface device further comprises a summer, a differentiator and a filter.

54. The apparatus of claim 43 further comprising a device for displaying said first input signal and said second input signal as digital waveforms.

55. The apparatus according to claim 43 further comprising a device for displaying first input signal and said second input signal as analog waveforms.

56. The apparatus of claim 43, wherein the processing device comprises a programmable computer having a memory, the memory having stored referenced data.

57. The apparatus of claim 43 wherein the apparatus weighs less than fifteen (15) pounds.