Acoustic detection of respiratory conditions

• US 6,443,907 B1
• Filed: 10/06/2000
• Issued: 09/03/2002
• Est. Priority Date: 10/06/2000
• Status: Expired due to Term

• Current Assignee: Biomedical Acoustic Research Corporation
• Original Assignee: Biomedical Acoustic Research Corporation
• Inventors: Sandler, Richard H., Mansy, Hussein A.
• Primary Examiner(s): Shaver, Kevin
• Assistant Examiner(s): Natnithithadha, Navin
• Application Number:
  US09/684,068
• Time in Patent Office: 697 Days
• Field of Search: 600/529, 600/586, 600/587, 600/552, 600/553, 600/530, 600/531, 600/532, 600/533, 600/534, 600/535, 600/538, 600/437, 600/438
• US Class Current: 600/529
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R

Abstract

Diagnostic techniques are provided to enable the detection of a respiratory condition within a patient'"'"'s body. The diagnostic techniques compare the acoustic generation and transmission characteristics of the patient'"'"'s chest and lungs to reference acoustic characteristics and/or predetermined threshold values to determine if an abnormal respiratory condition is present within the patient. The diagnostic techniques process sound waves or vibrations that have interacted with a respiratory condition within a patient and which impinge on the chest wall of the patient. The sound waves or vibrations may be initiated by a speaker that emits sounds waves into the mouth and trachea of the patient or may be indigenous sounds. Alternatively, the sounds waves or vibrations may be initiated using percussive inputs to the chest wall of the patient. In processing the sound waves, the diagnostic techniques calculate energy ratios using energy values within high and low frequency bands, signal time delays, and/or dominant frequencies and compare the calculated values to predetermined reference thresholds to generate outputs indicative of the respiratory condition within the patient.

Claims

1. A method of detecting a respiratory condition within a body, the method comprising the steps of:

emitting sound waves into an opening of the body;

receiving the emitted sound waves;

converting the emitted sound waves into a first electrical signal;

receiving vibrations resulting from the sound waves interacting with the respiratory condition and impinging on a location of the body;

converting the received vibrations into a second electrical signal; and

using the first and second electrical signals to calculate a value indicative of the respiratory condition.

2. The method of claim 1, wherein the step of using the first and second electrical signals to calculate the value indicative of the respiratory condition includes the steps of:

generating a first set of frequency data using the first electrical signal;

generating a second set of frequency data using the second electrical signal;

calculating transfer function data using the first and second sets of frequency data; and

using the transfer function data to calculate an energy ratio indicative of the respiratory condition.

3. The method of claim 2, wherein the step of using the transfer function data to calculate the energy ratio indicative of the respiratory condition includes the step of calculating the energy ratio indicative of the respiratory condition based on a first energy within a first band of frequencies and a second energy within a second band of frequencies.

4. The method of claim 3, wherein the step of calculating the energy ratio based on the first energy within the first band of frequencies and the second energy within the second band of frequencies includes the step of defining the first band of frequencies to include higher frequency components than the second band of frequencies.

5. The method of claim 2, wherein the steps of generating the first and second sets of frequency data include the step of using a fast Fourier transform.

6. The method of claim 1, wherein the step of receiving the vibrations resulting from the sound waves interacting with the respiratory condition and impinging on the location of the body includes the step of receiving the vibrations adjacent to a surface of the body.

7. The method of claim 6, wherein the step of receiving the vibrations adjacent to the surface of the body includes the step of receiving the vibrations adjacent to a chest wall of the body.

8. The method of claim 1, wherein the step of emitting the sound waves into the opening of the body includes the step of emitting broadband noise into the opening of the body.

9. The method of claim 1, wherein the step of emitting the sound waves into the opening of the body includes the step of emitting the sound waves into a mouth portion of the body.

10. The method of claim 2, further comprising the steps of comparing the energy ratio indicative of the respiratory condition to a reference threshold and generating an output indicative of the comparison.

11. The method of claim 10, wherein the step of providing the output indicative of the comparison includes the step of generating an output indicative of a pneumothorax condition.

12. The method of claim 10, wherein the step of providing the output indicative of the comparison includes the step of generating an output indicative of a misplaced endotracheal tube.

13. The method of claim 2, further comprising the steps of using the first and second electrical signals to calculate a time delay and using a neural network to process the time delay and the energy ratio to generate an output indicative of the respiratory condition.

14. The method of claim 13, wherein the step of using the neural network to process the time delay and the energy ratio to generate the output indicative of the respiratory condition includes the step of generating an output indicative of a pneumothorax condition.

15. The method of claim 13, wherein the step of using the neural network to process the time delay and the energy ratio to generate the output indicative of the respiratory condition includes the step of generating an output indicative of a misplaced endotracheal tube.

16. The method of claim 1, wherein the step of using the first and second electrical signals to calculate the value indicative of the respiratory condition includes the steps of calculating a signal time delay between the first and second electrical signals and comparing the signal time delay to a predetermined threshold value.

17. The method of claim 16, wherein the step of comparing the signal time delay to the predetermined threshold value includes the step of using a predetermined threshold value associated with a pneumothorax condition.

18. The method of claim 16, wherein the step of comparing the signal time delay to the predetermined threshold value includes the step of using a predetermined threshold value associated with a misplaced endotracheal tube.

19. A system for use in detecting a respiratory condition within a body, the system comprising:

a source of sound waves that emits sound waves into an opening of the body;

a first transducer that converts the sound waves emitted into the opening of the body into a first electrical signal;

a second transducer adjacent to a location on the body that receives vibrations resulting from the sound waves interacting with the respiratory condition and impinging on the location on the body and converts the received vibrations into a second electrical signal; and

a processing unit that uses the first and second electrical signals to calculate a value indicative of the respiratory condition.

20. The system of claim 19, wherein the first transducer is a microphone.

21. The system of claim 19, wherein the second transducer is a vibration sensor.

22. The system of claim 19, wherein the source of sound waves is a speaker.

23. The system of claim 19, wherein the respiratory condition is pneumothorax.

24. The system of claim 19, wherein the respiratory condition is a misplaced endotracheal tube.

25. The system of claim 19, wherein the processing unit:

generates a first set of frequency data using the first electrical signal;

generates a second set of frequency data using the second electrical signal;

calculates transfer function data using the first and second sets of frequency data; and

uses the transfer function data to calculate an energy ratio indicative of the respiratory condition.

26. The system of claim 25, wherein the processing unit calculates the energy ratio indicative of the respiratory condition based on a first energy within a first band of frequencies and a second energy within a second band of frequencies.

27. The system of claim 26, wherein the first band of frequencies includes higher frequency components than the second band of frequencies.

28. The system of claim 19, wherein the processing unit calculates a signal time delay between the first and second electrical signals and compares the signal time delay to a predetermined threshold value.

29. A system for use in an apparatus having a processor that emits sound waves into an opening of a body to detect a respiratory condition within the body, the system comprising:

a computer readable medium;

a plurality of routines stored on the computer readable medium and adapted to be executed by the processor, wherein the plurality of routines comprises;

a first routine that is adapted to convert the sound waves emitted into the opening of the body into a first electrical signal;

a second routine that is adapted to convert vibrations resulting from the emitted sound waves interacting with the respiratory condition and impinging on a location of the body into a second electrical signal; and

a third routine that is adapted to use the first and second electrical signals to calculate a value indicative of the respiratory condition.

30. The system of claim 29, wherein the third routine is further adapted to:

generate a first set of frequency data using the first electrical signal;

generate a second set of frequency data using the second electrical signal;

calculate transfer function data using the first and second sets of frequency data; and

use the transfer function data to calculate an energy ratio indicative of the respiratory condition.

31. The system of claim 30, wherein the third routine is further adapted to calculate the energy ratio based on a first energy within a first band of frequencies and a second energy within a second band of frequencies.

32. The system of claim 31, wherein the third routine is further adapted to define the first band of frequencies to include higher frequency components than the second band of frequencies.

33. The system of claim 30, wherein the plurality of routines further comprises a fourth routine that is adapted to compare the energy ratio indicative of the respiratory condition to a reference threshold and generate an output indicative of the comparison.

34. The system of claim 33, wherein the fourth routine is further adapted to generate an output indicative of a pneumothorax condition.

35. The system of claim 33, wherein the fourth routine is further adapted to generate an output indicative of a misplaced endotracheal tube.

36. The system of claim 30, wherein the plurality of routines further comprises a fourth routine that is adapted to use the first and second electrical signals to calculate a time delay and to use a neural network to process the time delay and the energy ratio indicative of the respiratory condition to generate an output indicative of the respiratory condition.

37. The system of claim 36, wherein the fourth routine is further adapted to generate an output indicative of a pneumothorax condition.

38. The system of claim 36, wherein the fourth routine is further adapted to generate an output indicative of a misplaced endotracheal tube.

39. The system of claim 29, wherein the third routine is further adapted to calculate a signal time delay between the first and second electrical signals and compare the signal time delay to a predetermined threshold value.

40. A method of detecting a respiratory condition within a body, the method comprising the steps of:

receiving indigenous respiratory sounds adjacent to a first location on the body at a first time;

converting the indigenous respiratory sounds received at the first time into a first electrical signal;

generating a first set of frequency data using the first electrical signal; and

using the first set of frequency data to calculate an energy ratio indicative of the respiratory condition.

41. The method of claim 40, wherein the step of using the first set of frequency data to calculate the energy ratio indicative of the respiratory condition includes the step of calculating the energy ratio indicative of the respiratory condition based on a first energy within a first band of frequencies and a second energy within a second band of frequencies.

42. The method of claim 41, wherein the step of calculating the energy ratio based on the first energy within the first band of frequencies and the second energy within the second band of frequencies includes the step of defining the first band of frequencies to include higher frequency components than the second band of frequencies.

43. The method of claim 40, further comprising the steps of:

receiving indigenous respiratory sounds adjacent to the first location on body at a second time,

converting the indigenous respiratory sounds received at the second time into a second electrical signal;

generating a second set of frequency data using the second electrical signal; and

using the second set of frequency data to calculate the energy ratio indicative of the respiratory condition.

44. The method of claim 43, wherein the step of receiving the indigenous respiratory sounds adjacent to the first location on the body at the first and second times includes the step of receiving respiratory sounds associated with one of a pair of lungs within the body.

45. The method of claim 43, wherein the step of receiving the indigenous respiratory sounds adjacent to the first location on body at the second time includes the step of receiving indigenous respiratory sounds prior to the existence of the respiratory condition.

46. The method of claim 40, further comprising the steps of:

receiving indigenous respiratory sounds adjacent to a second location on body;

converting the indigenous respiratory sounds received adjacent to the second location into a second electrical signal;

generating a second set of frequency data using the second electrical signal; and

using the second set of frequency data to calculate the energy ratio indicative of the respiratory condition.

47. The method of claim 46, wherein the step of receiving indigenous respiratory sounds adjacent to the first location on the body at the first time includes the step of receiving respiratory sounds associated with one of a pair of lungs within the body, and wherein the step of receiving indigenous respiratory sounds adjacent to the second location on the body includes the step of receiving respiratory sounds associated with the other one of the pair of lungs within the body.

48. A system for use in detecting a respiratory condition within a body, the system comprising:

a first transducer that converts indigenous respiratory sounds received adjacent to a first location on the body into a first electrical signal; and

a processing unit that generates a first set of frequency data using the first electrical signal and that uses the first set of frequency data to calculate an energy ratio indicative of the respiratory condition.

49. The system of claim 48, wherein the processing unit calculates the energy ratio indicative of the respiratory condition based on a first energy within a first band of frequencies and a second energy within a second band of frequencies.

50. The system of claim 49, wherein the first band of frequencies includes higher frequency components than the second band of frequencies.

51. The system of claim 48, wherein first location on the body is associated with one of a pair of lungs within the body.

52. The system of claim 48, further comprising a second transducer that converts respiratory sounds received adjacent to a second location on the body into a second electrical signal, and wherein the processing unit generates a second set of frequency data using the second electrical signal and uses the second set of frequency data to calculate the energy ratio indicative of the respiratory condition.

53. The system of claim 52, wherein the first and second locations adjacent to the body are associated with first and second respective lungs within the body.

54. A method of detecting a respiratory condition within a body, the method comprising the steps of:

impacting a portion of the body;

receiving vibrations resulting from the impact interacting with the respiratory condition and the impacted portion of the body;

converting the received vibrations into an electrical signal; and

using the electrical signal to calculate a value indicative of the respiratory condition.

55. The method of claim 54, wherein the step of using the electrical signal to calculate the value indicative of the respiratory condition includes the steps of calculating an envelope of the electrical signal and using the envelope to calculate a characteristic of the envelope of the electrical signal.

56. The method of claim 55, wherein the step of using the envelope to calculate the characteristic of the envelope of the electrical signal includes the steps of:

identifying a temporal location associated with a maximum amplitude of the envelope of the electrical signal;

identifying a portion of the envelope of the electrical signal surrounding the temporal location associated with the maximum amplitude of the envelope of the electrical signal; and

calculating the characteristic of the envelope of the electrical using the identified portion of the envelope of the electrical signal.

57. The method of claim 56, wherein the step of calculating the characteristic of the envelope of the electrical signal using the identified portion of the envelope of the electrical signal includes the steps of calculating a first time associated with an attack portion of the identified portion of the envelope of the electrical signal and calculating a second time associated with a decay portion of the identified portion of the envelope of the electrical signal.

58. The method of claim 56, wherein the step of calculating the characteristic of the envelope of the electrical signal using the identified portion of the envelope of the electrical signal includes the steps of fitting a curve to the identified portion of the envelope of the electrical signal and calculating a slope of the curve.

59. The method of claim 56, wherein the step of calculating the characteristic of the envelope of the electrical signal using the identified portion of the envelope of the electrical signal includes the step of determining the dominant frequency of the electrical signal.

60. The method of claim 56, wherein the step of calculating the characteristic of the envelope of the electrical signal using the identified portion of the envelope of the electrical signal includes the step of calculating a characteristic value associated with a pneumothorax condition.

61. A system for use in detecting a respiratory condition within a body, the system comprising:

an impact device that impacts a portion of the body to produce vibrations within the body;

a transducer that converts vibrations resulting from impacts to the portion of the body after the vibrations have interacted with the respiratory condition in the impacted portion of the body into an electrical signal; and

a processing unit that uses the electrical signal to calculate a value indicative of the respiratory condition.

62. The system of claim 61, wherein the processing unit calculates an envelope of the electrical signal and uses the envelope of the electrical signal to calculate a characteristic of the envelope of the electrical signal.

63. The system of claim 62, wherein the processing unit:

identifies a temporal location associated with a maximum amplitude of the envelope of the electrical signal;

identifies a portion of the envelope of the electrical signal surrounding the temporal location associated with the maximum amplitude of the envelope of the electrical signal; and

calculates the characteristic of the envelope of the electrical using the identified portion of the envelope of the electrical signal.

64. The system of claim 62, wherein the processing unit calculates a first time associated with an attack portion of the identified portion of the envelope of the electrical signal and a second time associated with a decay portion of the identified portion of the envelope of the electrical signal.

65. The system of claim 62, wherein the processing unit fits a curve to the identified portion of the envelope of the electrical signal and calculates a slope of the curve.

66. The system of claim 62, wherein the processing unit determines the dominant frequency of the electrical signal.

67. The system of claim 62, wherein the processing unit calculates a characteristic value associated with a pneumothorax condition.