Method and system for reliable respiration parameter estimation from acoustic physiological signal

• US 20110295139A1
• Filed: 05/28/2010
• Published: 12/01/2011
• Est. Priority Date: 05/28/2010
• Status: Abandoned Application

• Current Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Fu, Yongji, Yang, Te-Chung Isaac
• Application Number:
  US12/802,044
• Publication Number:
  US 20110295139A1
• Time in Patent Office: Days
• US Class Current: 600/529
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61B 7/003 Detecting lung or respiration noise

Abstract

A method and system that reliably estimates a respiration parameter from an acoustic physiological signal without introducing undue complexity or intense computation. A median filter is applied to an energy envelope of the signal to remove heart sound “sparks” from the envelope and better isolate lung sounds. The median filter is followed by a low-pass filter that removes abrupt changes in the envelope caused by the median filter'"'"'s nonlinearity. Various peak cross-checks are performed on an autocorrelation result generated from the envelope to confirm the reliability of the signal before an estimate of a respiration parameter is generated from the autocorrelation result.

Claims

1. A respiratory monitoring system, comprising:

a transducer;

a processor communicatively coupled with the transducer; and

an output interface, wherein under control of the processor the system extracts an energy envelope of an acoustic physiological signal captured by the transducer, applies a median filter and a low-pass filter in sequence to the energy envelope, and generates an estimate of a respiration parameter using the sequentially filtered energy envelope, and wherein the estimate is outputted on the output interface.

2. The system of claim 1, wherein under control of the processor the energy envelope is extracted using a standard deviation method.

3. The system of claim 1, wherein under control of the processor an autocorrelation result is determined using the sequentially filtered energy envelope and the estimate is made using the autocorrelation result.

4. The system of claim 3, wherein the autocorrelation result is validated using peak cross-checks before the estimate is generated.

5. The system of claim 4, wherein the peak cross-checks comprise a determination that a time delay of a highest peak of the autocorrelation result conforms with a time delay of a second highest peak of the autocorrelation result.

6. The system of claim 4, wherein the peak cross-checks comprise a determination that a time delay of a highest peak of the autocorrelation result conforms with a previous estimate of a respiration parameter.

7. The system of claim 4, wherein the peak cross-checks comprise a determination that a time delay of a second highest peak of the autocorrelation result conforms with a previous estimate of a respiration parameter.

8. The system of claim 4, wherein the peak cross-checks comprise a determination that a time delay of a peak of the autocorrelation result conforms with a time delay of a peak of a previous autocorrelation result.

9. The system of claim 1, wherein the respiration parameter is respiration rate.

10. The system of claim 1, wherein the output interface comprises a user interface and the estimate is displayed on the user interface.

11. The system of claim 1, wherein the system is portable.

12. A respiratory monitoring system, comprising:

a transducer;

a processor communicatively coupled with the transducer; and

an output interface, wherein under control of the processor the system extracts an energy envelope of an acoustic physiological signal captured by the transducer, determines a autocorrelation result using the energy envelope, validates the autocorrelation result using peak cross-checks and generates an estimate of a respiration parameter using the validated autocorrelation result, and wherein the estimate is outputted on the output interface.

13. The system of claim 12, wherein the peak cross-checks comprise a determination that a time delay of a highest peak of the autocorrelation result conforms with a time delay of a second highest peak of the autocorrelation result.

14. The system of claim 12, wherein the peak cross-checks comprise a determination that a time delay of a highest peak of the autocorrelation result conforms with a previous estimate of a respiration parameter.

15. The system of claim 12, wherein the peak cross-checks comprise a determination that a time delay of a second highest peak of the autocorrelation result conforms with a previous estimate of a respiration parameter.

16. The system of claim 12, wherein the peak cross-checks comprise a determination that a time delay of a peak of the autocorrelation result conforms with a time delay of a peak of a previous autocorrelation result.

17. The system of claim 12, wherein a median filter and a low-pass filter are applied in sequence to the energy envelope before the autocorrelation result is determined.

18. The system of claim 12, wherein the output interface comprises a user interface and the estimate is displayed on the user interface.

19. A respiratory monitoring method, comprising the steps of:

capturing by a physiological monitoring system an acoustic physiological signal;

extracting by the system an energy envelope of the signal;

applying by the system a median filter and a low-pass filter in sequence to the energy envelope;

determining by the system a autocorrelation result using the sequentially filtered energy envelope;

validating by the system the autocorrelation result using peak cross-checks;

generating by the system an estimate of a respiration parameter using the validated autocorrelation result; and

outputting by the system the estimate.

20. The method of claim 19, wherein the estimate is displayed on a user interface.