Method and Apparatus For Detecting Ineffective Inspiratory Efforts and Improving Patient-Ventilator Interaction

• US 20080110461A1
• Filed: 10/20/2005
• Published: 05/15/2008
• Est. Priority Date: 10/20/2004
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Mulqueeny, Qestra Camille, Nava, Stefano
• Granted Patent: US 8,603,006 B2
• Time in Patent Office: Days
• US Class Current: 128/204.23
• CPC Class Codes: A61B 5/0871 Peak expiratory flowmeters
• CPC Class Codes: A61B 5/4205 Evaluating swallowing
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/026 specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase

Abstract

A method and system for detecting an ineffective effort of a patient being mechanically ventilated by a ventilator comprises (i) monitoring a respiratory flow of air of the patient after said ventilator has cycled; (ii) creating a signal indicative of said flow; (iii) removing artefact from said signal; (iv) monitoring said signal for perturbations; and (v) determining that an ineffective effort has occurred when said perturbation is significant.

Claims

1. A method of detecting an ineffective effort of a patient being mechanically ventilated by a ventilator comprising the steps of:

(i) monitoring a respiratory flow of air of the patient after said ventilator has cycled;

(ii) creating a signal indicative of said flow;

(iii) removing artefact from said signal;

(iv) monitoring said signal for perturbations; and

(v) determining that an ineffective effort has occurred when said perturbation is significant.

2. A method as claimed in claim 1 whereby said step of removing artefact from said signal comprises the step of removing a signal representative of cardiogenic oscillation.

3. A method as claimed in claim 1 whereby said step of removing artefact from said signal comprises the step of determining whether a cough has occurred.

4. A method as claimed in claim 1 whereby said step of removing artefact from said signal comprises the step of removing signals indicative of secretions.

5. A method as claimed in claim 1 whereby said step of removing artefact from said signal comprises the step of passing said flow signal through a noise filter.

6. A method as claimed in claim 1 whereby said step of monitoring said signal for perturbations comprises the step of detecting a local maximum.

7. A method as claimed in claim 1 whereby said step of monitoring said signal for perturbations includes the step of detecting a declivity.

8. A method as claimed in claim 1 further including the step of determining whether a potential swallow has occurred.

9. A method as claimed in claim 8 further including the step of determining the time elapsed since the onset of a potential swallow.

10. The method of claim 1 further including the step of determining a peak expiratory flow (PEF) of the patient.

11. The method of claim 10 further including the step of determining that a cough has occurred when PEF exceeds a threshold.

12. The method of claim 11 whereby said threshold is approximately 200 L per minute.

13. The method of claim 6 further comprising the step of determining the flow that occurs at said local maximum.

14. The method of claim 13 further including the step of determining that a potential swallow has occurred when the flow that occurs at said local maximum is near zero.

15. The method of claim 14 further including the step of starting a swallow timer when the flow that occurs at said local maximum is near zero.

16. The method of claim 15 further including the step of determining that a swallow has occurred when said swallow timer is greater than about 500 ms.

17. A method as claimed in claim 7 whereby a significant declivity is determined to have occurred when the second derivative of flow is greater than a negative threshold.

18. The method of claim 17 whereby said threshold is a percentage of the standard deviation.

19. The method of claim 18 whereby said percentage is approximately 33%.

20. The method of claim 2 whereby said step of removing a signal representative of cardiogenic oscillation comprises down-sampling or noise-filtering.

21. The method of claim 2 whereby said step of removing a signal representative of cardiogenic oscillation comprises distinguishing cardiogenic oscillation on the basis of amplitude.

22. The method of claim 21 whereby cardiogenic signals are assumed to have an amplitude of less than approximately 4 L per minute.

23. The method of claim 7 further including the step of determining the end of the declivity by detecting a local minimum.

24. The method of claim 23 further including the step of determining the amplitude of the declivity.

25. The method of claim 23 whereby said step of determining the amplitude of the declivity comprises subtracting the values of flow at said local minimum from the value of flow at said local maximum.

26. The method of claim 24 further including the step of determining that cough has occurred when the amplitude of the declivity is greater than a threshold.

27. The method of claim 26 further including the step of determining a peak expiratory flow (PEF) of the patient.

28. The method of claim 27 whereby said threshold is the PEF.

29. The method of claim 27 whereby said threshold is approximately 200 L/min.

63. A system as claimed in claim 1 wherein said processor is configured to monitor said signal for perturbations by detecting a declivity.

68. The system of claim 63, wherein the processor is configured to determine the flow that occurs at said local maximum.

69. The system of claim 68, wherein the processor is configured to determine that a potential swallow has occurred when the flow that occurs at said local maximum is near zero.

70. The system of claim 69, wherein the processor is configured to start a swallow timer when the flow that occurs at said local maximum is near zero.

71. The system of claim 70, wherein the processor is configured to determine that a swallow has occurred when said swallow timer is greater than about 500 ms.

72. A system as claimed in claim 63 whereby a significant declivity is determined to have occurred when the second derivative of flow is greater than a negative threshold.

73. The system of claim 72 whereby said threshold is a percentage of the standard deviation.

74. The system of claim 73 whereby said percentage is approximately 33%.

78. The system of claim 63, wherein the processor is configured to determine the end of the declivity by detecting a local minimum.

79. The system of claim 78, wherein the processor is configured to determine the amplitude of the declivity.

80. The system of claim 78, wherein the processor is configured to determine the amplitude of the declivity comprises by subtracting the values of flow at said local minimum from the value of flow at said local maximum.

81. The system as claimed in claim 79, wherein the processor is configured to determine that a cough has occurred when the amplitude of the declivity is greater than a threshold.

82. The system as claimed in claim 78, wherein the processor is configured to determine a peak expiratory flow (PEF) of the patient.

83. The system of claim 82 whereby said threshold is the PEF.

84. The system of claim 82 whereby said threshold is approximately 200 L/min.

30. A system for detecting an ineffective effort of a patient being mechanically ventilated by a ventilator comprising:

(i) means for monitoring a respiratory flow of air of the patient after said ventilator has cycled;

(ii) means for creating a signal indicative of said flow;

iii) means for removing artefact from said signal;

iv) means for monitoring said signal for perturbations; and

v) means for determining that an ineffective effort has occurred when said perturbation is significant.

31. A system as claimed in claim 30 whereby said means for removing artefact from said signal includes means for removing a signal representative of cardiogenic oscillation.

32. A system as claimed in claim 30 whereby said means for removing artefact from said signal comprises means for determining whether a cough has occurred.

33. A system as claimed in claim 30 whereby said means for removing artefact from said signal comprises means for removing signals indicative of secretions.

34. A system as claimed in claim 30 whereby said means for removing artefact from said signal comprises means for passing said flow signal through a noise filter.

35. A system as claimed in claim 30 whereby said means for monitoring said signal for perturbations comprises means for detecting a local maximum.

36. A system as claimed in claim 30 whereby said means for monitoring said signal for perturbations includes means for detecting a declivity.

37. A system as claimed in claim 30 further including means for determining whether a potential swallow has occurred.

38. A system as claimed in claim 37 further including means for determining the time elapsed since the onset of a potential swallow.

39. The system of claim 30 further including means for determining a peak expiratory flow (PEF) of the patient.

40. The system of claim 39 further including means for determining that a cough has occurred when PEF exceeds a threshold.

41. The system of claim 40 whereby said threshold is approximately 200 L per minute.

42. The system of claim 35 further comprising means for determining the flow that occurs at said local maximum.

43. The system of claim 42 further including means for determining that a potential swallow has occurred when the flow that occurs at said local maximum is near zero.

44. The system of claim 43 further including means for starting a swallow timer when the flow that occurs at said local maximum is near zero.

45. The system of claim 44 further including means for determining that a swallow has occurred when said swallow timer is greater than about 500 ms.

46. A system as claimed in claim 37 whereby a significant declivity is determined to have occurred when the second derivative of flow is greater than a negative threshold.

47. The system of claim 46 whereby said threshold is a percentage of the standard deviation.

48. The system of claim 47 whereby said percentage is approximately 33%.

49. The system of claim 31 whereby said means for removing a signal representative of cardiogenic oscillation comprises means for down-sampling or noise-filtering.

50. The system of claim 31 whereby said means for removing a signal representative of cardiogenic oscillation comprises means for distinguishing cardiogenic oscillation on the basis of amplitude.

51. The system of claim 50 whereby cardiogenic signals are assumed to have an amplitude of less than approximately 4 L per minute.

52. The system of claim 37 further including means for determining the end of the declivity by detecting a local minimum.

53. The system of claim 52 further including means for determining the amplitude of the declivity.

54. The system of claim 52 whereby said means for determining the amplitude of the declivity comprises means for subtracting the values of flow at said local minimum from the value of flow at said local maximum.

55. The system of claim 53 further including means for determining that cough has occurred when the amplitude of the declivity is greater than a threshold.

56. The system of claim 55 further including means for determining a peak expiratory flow (PEF) of the patient.

57. The system of claim 56 whereby said threshold is the PEF.

58. The system of claim 56 whereby said threshold is approximately 200 L/min.

59. A system for detecting an ineffective effort of a patient being mechanically ventilated by a ventilator comprising:

a flow sensor to monitor a respiratory flow of air of the patient after said ventilator has cycled and to generate a signal indicative of said flow; and

a processor to remove artefact from said signal, to monitor said signal for perturbations, and to determine that an ineffective effort has occurred when said perturbation is significant.

60. A system as claimed in claim 59, wherein said artefact includes at least one of a signal representative of cardiogenic oscillation, a cough, secretions, a cough and/or a swallow.

61. A system as claimed in claim 59, further comprising a noise filter to remove said artefact.

62. A system as claimed in claim 59, wherein said processor is configured to monitor said signal for perturbations by detecting a local maximum.

64. A system as claimed in claim 60, wherein the processor is configured to determine the time elapsed since the onset of a potential swallow.

65. The system of claim 59, wherein the processor is configured to determine a peak expiratory flow (PEF) of the patient.

66. The system of claim 65, wherein the processor is configured to determine that a cough has occurred when PEF exceeds a threshold.

67. The system of claim 66, whereby said threshold is approximately 200 L per minute.

75. The system of claim 60, wherein the processor is configured to remove a signal representative of cardiogenic oscillation by down-sampling or noise-filtering.

76. The system of claim 60, wherein the processor is configured to remove a signal representative of cardiogenic oscillation by distinguishing cardiogenic oscillation on the basis of amplitude.

77. The system of claim 76 whereby cardiogenic signals are assumed to have an amplitude of less than approximately 4 L per minute.

85. A ventilator system for a patient, comprising:

a blower to produce a source of pressurized breathable gas;

a patient interface to deliver the breathable gas to the patient'"'"'s airways;

and a system according to claim 59,

wherein the ventilator is at least partially controlled based on a measure of breathing effort of the patient as determined by the processor.

86. A system as claimed in claim 85 wherein a Positive End Expiratory Pressure (PEEP) is adjusted based on a measure of breathing effort of the patient as determined by the processor.

87. A system as claimed in claim 86 wherein when the patient has COPD said adjustment of PEEP is limited to 6 cm H2O.

88. A system as claimed in claim 86 further comprising a means for measuring oxygen saturation of the patient.

89. A system as claimed in claim 88 wherein the adjustment of PEEP is a function of the measured oxygen saturation.

91. A method of determining a measure of patient compliance with a mechanical ventilator comprising the steps of:

detecting ineffective efforts as claimed in claim 86;

recording a signal indicative of the said ineffective efforts over time;

calculating a parameter based on said signal;

determining a measure of patient compliance as a function of said parameter.

92. A method of detecting the onset of exacerbations of a mechanically ventilated patient'"'"'s condition comprising the steps of:

detecting the presence of ineffective efforts as claimed in claim 86;

monitoring the rate at which said ineffective efforts occur; and

determining that the onset of exacerbations have occurred when said rate changes.

93. A method of detecting the respiratory rate of a mechanically ventilated patient comprising the steps of:

detecting the presence of ineffective efforts as claimed in claim 86;

monitoring the rate at which said ineffective efforts occur;

monitoring the rate of breaths delivered by the ventilator and

determining the respiratory rate from the sum of the rate of ineffective efforts and the rate of breaths delivered by the ventilator.

90. A method of detecting an ineffective effort of a patient being mechanically ventilated by a ventilator comprising the steps of:

(i) monitoring a respiratory flow of air of the patient after said ventilator has cycled;

(ii) creating a signal indicative of said flow;

(iii) removing artefact from said signal;

(iv) monitoring said signal for perturbations;

(v) classifying a perturbation according to a classification system; and

(vi) determining that an ineffective effort has occurred when said classification system indicates perturbation is significant.

94. A method of detecting an ineffective effort of a patient being mechanically ventilated by a ventilator comprising the steps of:

(i) monitoring pressure at the entrance to the airways of the patient after said ventilator has cycled;

(ii) creating a signal indicative of said pressure;

(iii) removing artefact from said signal;

(iv) monitoring said signal for perturbations;

(v) classifying a perturbation according to a classification system; and

(vi) determining that an ineffective effort has occurred when said classification system indicates perturbation is significant.