METHODS AND APPARATUS FOR DETERMINING BREATHING EFFORT CHARACTERISTIC MEASURES

• US 20110004081A1
• Filed: 07/02/2009
• Published: 01/06/2011
• Est. Priority Date: 10/03/2008
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Cassidy, Andrew M., Addison, Paul Stanley, Watson, James N.
• Granted Patent: US 9,011,347 B2
• Time in Patent Office: Days
• US Class Current: 600/322
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

One or more respiratory characteristics of a patient are measured by coupling patient monitor apparatus (e.g., a photoplethysmograph (“PPG”)) to the patient in order to produce a patient monitor signal that includes signal indicia indicative of effort the patient is exerting to breathe. A breathing or respiratory effort signal for the patient is extracted from the patient monitor signal. A respiratory characteristic signal is extracted (at least in part) from the effort signal. This may be done, for example, on the basis of an amplitude feature of the effort signal and a relative time of occurrence of that amplitude feature. Alternatively, the respiratory characteristic signal may be based on a relationship between two amplitude features of the effort signal, with or without regard for specifics of the times of occurrence of those amplitude features. A breath air flow meter may also be coupled to the patient, if desired, in order to produce a flow signal. One or more of the respiratory characteristic measures may also be partly based on the flow signal.

Claims

1. Apparatus for determining a respiratory characteristic of a patient comprising:

apparatus coupled to the patient for producing a patient monitor signal containing signal information indicative of effort the patient is exerting to breathe;

first circuitry for extracting from the patient monitor signal a breathing effort signal indicative of the patient'"'"'s exertion of effort in order to breathe; and

second circuitry for extracting from the effort signal a respiratory characteristic signal for the patient that is based on at least one amplitude feature of the effort signal and a relative time of occurrence of that amplitude feature.

2. The apparatus defined in claim 1 wherein the respiratory characteristic signal is indicative of elapsed time from a minimum to a subsequent maximum in the amplitude of the effort signal.

3. The apparatus defined in claim 1 wherein the respiratory characteristic signal is indicative of elapsed time from one maximum to a next subsequent maximum in the amplitude of the effort signal.

4. The apparatus defined in claim 1 wherein the respiratory characteristic signal comprises a first precursor respiratory characteristic signal, wherein the second circuitry is further adapted to extract from the effort signal a second precursor respiratory characteristic signal for the patient that is based on at least one other amplitude feature of the effort signal, and wherein the second circuitry is still further adapted to produce a further respiratory characteristic signal for the patient that is indicative of a ratio between the first and second precursor respiratory characteristic signals.

5. The apparatus defined in claim 4 wherein the first precursor signal is indicative of elapsed time from a minimum to a subsequent maximum in the amplitude of the effort signal, and wherein the second precursor signal is indicative of elapsed time from one maximum to a next subsequent maximum in the amplitude of the effort signal.

6. The apparatus defined in claim 4 wherein the first precursor signal is indicative of an elapsed time between two amplitude features of the effort signal, and wherein the second precursor signal is indicative of a magnitude of an amplitude feature of the effort signal.

7. The apparatus defined in claim 1 further comprising:

a flow meter coupled to the patient for producing a breathing air flow signal for the patient, wherein the flow signal is applied to the second circuitry, and wherein the respiratory characteristic signal is additionally based on at least one amplitude feature of the flow signal and a relative time of occurrence of that flow signal amplitude feature.

8. The apparatus defined in claim 7 wherein the amplitude feature of the flow signal indicates cessation of effective breathing by the patient, and wherein the amplitude feature of the effort signal indicates commencement of an increase in breathing effort by the patient.

9. The apparatus defined in claim 8 wherein the respiratory characteristic signal indicates elapsed time between said cessation and said commencement.

10. The apparatus defined in claim 7 wherein the respiratory characteristic signal comprises a first precursor respiratory characteristic signal, wherein the second circuitry is further adapted to extract a second precursor respiratory characteristic signal, at least in part, from the flow signal, and wherein the second circuitry is still further adapted to produce a further respiratory characteristic signal for the patient that is indicative of a ratio between the first and second precursor respiratory characteristic signals.

11. The apparatus defined in claim 10 wherein the first precursor signal indicates elapsed time between two successive maximum amplitude features in the effort signal.

12. The apparatus defined in claim 11 wherein the second precursor signal indicates elapsed time between (1) cessation of effective breathing by the patient as indicated by the flow signal, and

(2) commencement of an increase in breathing effort by the patient as indicated by the effort signal.

13. The apparatus defined in claim 7 wherein the respiratory characteristic signal comprises a first precursor respiratory characteristic signal which the second circuitry additionally bases in part on the flow signal, wherein the second circuitry is further adapted to extract a second precursor respiratory characteristic signal from the flow signal, and wherein the second circuitry is still further adapted to produce a further respiratory characteristic signal for the patient that is indicative of a ratio between the first and second precursor respiratory characteristic signals.

14. The apparatus defined in claim 13 wherein the first precursor signal indicates elapsed time between (1) cessation of effective breathing by the patient as indicated by the flow signal, and (2) commencement of an increase in breathing effort by the patient as indicated by the effort signal.

15. The apparatus defined in claim 14 wherein the second precursor signal indicates duration of a period of effective breathing by the patient as indicated by the flow signal.

16. The apparatus defined in claim 1 wherein the first circuitry comprises:

scalogram circuitry for producing scalogram signals indicative of the patient monitor signal; and

breathing effort extraction circuitry for extracting the effort signal from the scalogram signals.

17. The apparatus defined in claim 1 wherein the apparatus coupled to the patient comprises:

photoplethysmograph (“

PPG”

) apparatus coupled to the patient for producing a PPG signal as the patient monitor signal.

18. Apparatus for determining a respiratory characteristic of a patient comprising:

apparatus coupled to the patient for producing a patient monitor signal containing signal information indicative of effort the patient is exerting to breathe;

first circuitry for extracting from the patient monitor signal a breathing effort signal indicative of the patient'"'"'s exertion of effort in order to breathe; and

second circuitry for extracting from the effort signal a respiratory characteristic signal for the patient that is based on at least two amplitude features of the effort signal.

19. A method of determining a respiratory characteristic of a patient comprising:

coupling patient monitor circuitry to the patient in order to produce a patient monitor signal containing signal information indicative of effort the patient is exerting to breathe;

extracting from the patient monitor signal a breathing effort signal indicative of the patient'"'"'s exertion of effort in order to breathe; and

extracting from the effort signal a respiratory characteristic signal for the patient that is based on at least one amplitude feature of the effort signal and a relative time of occurrence of that amplitude feature.

20. The method defined in claim 19 wherein the coupling comprises:

coupling photoplethysmograph (“

PPG”

) circuitry to the patient in order to produce a PPG signal as the patient monitor signal.