Acoustic respiratory monitoring systems and methods

• US 10,463,340 B2
• Filed: 10/14/2010
• Issued: 11/05/2019
• Est. Priority Date: 10/15/2009
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Telfort, Valery G., Wylie, Mark
• Primary Examiner(s): Jang, Christian
• Assistant Examiner(s): Alter, Mitchell
• Application Number:
  US12/904,789
• Publication Number:
  US 20110125060A1
• Time in Patent Office: 3,309 Days
• Field of Search: 600586, 381 67, 704500
• CPC Class Codes: A61B 7/003 Detecting lung or respiration noise

Abstract

An acoustic sensor is provided according to certain aspects for non-invasively detecting physiological acoustic vibrations indicative of one or more physiological parameters of a medical patient. The sensor can include an acoustic sensing element configured to generate a first signal in response to acoustic vibrations from a medical patient. The sensor can also include front-end circuitry configured to receive an input signal that is based at least in part on the first signal and to produce an amplified signal in response to the input signal. In some embodiments, the sensor further includes a compression module in communication with the front-end circuitry and configured to compress portions of at least one of the input signal and the amplified signal according to a first compression scheme, the compressed portions corresponding to portions of the first signal having a magnitude greater than a predetermined threshold level.

Claims

1. An acoustic sensor configured to non-invasively detect physiological acoustic vibrations indicative of one or more physiological parameters of a medical patient, comprising:

a piezoelectric membrane configured to generate an initial signal in response to acoustic vibrations from a medical patient, the initial signal having an amplitude;

front-end circuitry configured to receive an input signal that is based at least in part on the initial signal and to produce an amplified signal in response to the input signal; and

a compression module in communication with the front-end circuitry and configured to;

select a first compression scheme of a plurality of dynamic range compression schemes, wherein different dynamic range compression schemes of the plurality of dynamic range compression schemes correspond to different modifications to signals;

compress a first portion of the initial signal according to the first compression scheme to generate a first compressed portion, the first portion of the initial signal having a magnitude of the amplitude that is greater than a predetermined threshold level,

wherein a second portion of the initial signal remains uncompressed by the compression module, the second portion corresponding to a portion of the initial signal having a magnitude of the amplitude that is less than the predetermined threshold level,

wherein the first compressed portion corresponds to a physiological sound louder than breathing, and

wherein the second portion corresponds to a breathing sound;

detect a characteristic of the initial signal;

select a second compression scheme of the plurality of dynamic range compression schemes based at least on the characteristic of the initial signal, wherein the second compression scheme is different from the first compression scheme; and

compress a third portion of the initial signal according to the second compression scheme to generate a compressed third portion; and

provide the input signal to the front-end circuitry, wherein the input signal comprises at least the first compressed portion, the second portion, and the third compressed portion.

2. The acoustic sensor of claim 1, wherein the third portion of the initial signal has a magnitude of the amplitude that is greater than a second predetermined threshold level different from the predetermined threshold level, wherein the magnitude of the amplitude of the first portion of the initial signal is less than the second predetermined threshold level.

3. The acoustic sensor of claim 1, wherein the first compression scheme is selected to increase a dynamic range of the acoustic sensor.

4. The acoustic sensor of claim 1, wherein the first compression scheme is selected based on a dynamic range of the front-end circuitry.

5. The acoustic sensor of claim 1, wherein the first compression scheme is selected such that the acoustic sensor does not produce a distorted output when high-amplitude physiological sounds are detected by the piezoelectric membrane, the high-amplitude physiological sounds corresponding to a portion of the initial signal having a magnitude of the amplitude corresponding to a saturation level of the front-end circuitry.

6. The acoustic sensor of claim 1, wherein the front-end circuitry comprises a preamplifier.

7. The acoustic sensor of claim 1, wherein the first compression scheme comprises executing a logarithmic function.

8. The acoustic sensor of claim 1, wherein the first compression scheme comprises executing a linear function.

9. The acoustic sensor of claim 8, wherein the linear function comprises a piece-wise linear function.

10. The acoustic sensor of claim 1, wherein the first compression scheme comprises executing a non-linear function.

21. The acoustic sensor of claim 1, wherein the characteristic of the initial signal comprises at least one of:

a type of sound represented by the initial signal;

an intensity, for a time period, of a sound represented by the initial signal;

or a saturation of a component of the acoustic sensor by the initial signal.

24. The acoustic sensor of claim 1, further comprising a decompression module configured to modify the amplified signal to reduce an effect of the compression module on the amplified signal.

11. An acoustic sensor configured to non-invasively detect physiological acoustic vibrations indicative of one or more physiological parameters of a medical patient, comprising:

an acoustic sensing element configured to generate an initial signal in response to acoustic vibrations from a medical patient, the acoustic sensing element having an output dynamic range, and the initial signal having an amplitude;

front-end circuitry in communication with the acoustic sensing element and having a dynamic range, the dynamic range of the front-end circuitry being less than the output dynamic range of the acoustic sensing element, wherein the front end circuitry is configured to produce an amplified signal based at least partly on the initial signal; and

a dynamic range module configured to;

select a first compression scheme of a plurality of dynamic range compression schemes, wherein different dynamic range compression schemes of the plurality of dynamic range compression schemes correspond to different modifications to signals;

modify at least a first portion of the amplified signal to generate a modified first portion by compressing at least the first portion of the amplified signal according to the first compression scheme, the first portion of the amplified signal corresponding to a portion of the initial signal having a magnitude of the amplitude that is greater than a predetermined threshold level, wherein the modified first portion of the amplified signal corresponds to a physiological sound louder than breathing, wherein a second portion of the amplified signal remains unmodified by the dynamic range module, the second portion of the amplified signal corresponding to a portion of the initial signal having a magnitude of the amplitude that is less than the predetermined threshold level, wherein the second portion of the amplified signal corresponds to a breathing sound;

detect a characteristic of the amplified signal;

determine, based at least on the characteristic, to change from using the first compression scheme to using a second compression scheme of the plurality of dynamic range compression schemes; and

modify a third portion of the amplified signal according to the second compression scheme to generate a modified third portion, wherein output from the dynamic range module comprises at least the modified first portion, the second portion, and the modified third portion.

12. The acoustic sensor of claim 11, wherein the dynamic range of the front-end circuitry is an input dynamic range.

13. The acoustic sensor of claim 11, wherein the dynamic range module is configured to modify the first portion of the amplified signal to allow the sensor to process a desired range of physiological intensities without producing a distorted output.

14. The acoustic sensor of claim 11, wherein the dynamic range module performs logarithmic compression on at least the first portion of the amplified signal.

15. The acoustic sensor of claim 11, wherein the dynamic range module performs linear compression on at least the first portion of the amplified signal.

16. The acoustic sensor of claim 15, wherein the linear compression comprises piece-wise linear compression.

17. The acoustic sensor of claim 11, wherein the dynamic range module performs non-linear compression on at least the first portion of the amplified signal.

22. The acoustic sensor of claim 11, wherein the acoustic sensing element is further configured to:

transmit first acoustic vibrations to a measurement site of the medical patient;

sense second acoustic vibrations from the measurement site; and

determine, based at least partly on the second acoustic vibrations, a characteristic of a mechanical connection between the acoustic sensing element and the measurement site.

18. A method comprising:

outputting an initial AC signal using a first sensing element and in response to acoustic vibrations from a medical patient, the initial AC signal having an amplitude;

generating an amplified signal using front-end circuitry and in response to an input signal that is based at least in part on the initial AC signal;

selecting a first compression scheme of a plurality of dynamic range compression schemes, wherein different dynamic range compression schemes of the plurality of dynamic range compression schemes correspond to different modifications to signals;

compressing portions of the amplified signal according to the first compression scheme, wherein the initial AC signal varies in amplitude about a DC offset and the compressed portions correspond to portions of the initial AC Signal deviating in amplitude from the DC offset by greater than a predetermined threshold level, and at least a portion of the amplified signal corresponding to a breathing sound remains uncompressed and at least a portion of the amplified signal corresponding to a physiological sound louder than breathing is compressed;

detecting a characteristic of the amplified signal;

determining, based at least on the characteristic, to change from using the first compression scheme to using a second compression scheme of the plurality of dynamic range compression schemes; and

compressing additional portions of the amplified signal according to the second compression scheme.

19. The method of claim 18, wherein the initial AC signal comprises positive and negative peaks and wherein the compressed portions correspond to both positive and negative peaks of the initial AC signal which deviate from the DC offset by greater than the predetermined threshold.

20. The method of claim 18, wherein the compressed portions correspond to only positive peaks of the initial AC signal which deviate from the DC offset by greater than the predetermined threshold.

23. The method of claim 18, further comprising:

comparing a signal deviation of a second portion of at least one of the initial AC signal or the amplified signal to a first sound signature of a plurality of sound signatures, the first sound signature associated with a respiratory condition;

determining, based at least partly on comparing the signal deviation of the second portion to the first sound signature, that the second portion corresponds to the first sound signature; and

automatically initiating a communication regarding the respiratory condition.