DISCRIMINATION OF CHEYNE-STOKES BREATHING PATTERNS BY USE OF OXIMETRY SIGNALS

• US 20120016218A1
• Filed: 04/15/2010
• Published: 01/19/2012
• Est. Priority Date: 04/20/2009
• Status: Abandoned Application

• Current Assignee: Resmed Limited (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Lau, Chun Yui, Armitstead, Jeffrey Peter
• Application Number:
  US13/259,649
• Publication Number:
  US 20120016218A1
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: G16H 50/70 for mining of medical data, e.g. analysing previous cases of other patients

Abstract

Methods and apparatus provide Cheyne-Stokes respiration (“CSR”) detection based on a blood gas measurements such as oximetry. In some embodiments, a duration, such as a mean duration of contiguous periods of changing saturation or re-saturation occurring in an epoch taken from a processed oximetry signal, is determined. An occurrence of CSR may be detected from a comparison of the duration and a threshold derived to differentiate saturation changes due to CSR respiration and saturation changes due to obstructive sleep apnea. The threshold may be a discriminant function derived as a classifier by an automated training method. The discriminant function may be further implemented to characterize the epoch for CSR based on a frequency analysis of the oximetry data. Distance from the discriminant function may be utilized to generate probability values for the CSR detection.

Claims

1. A method for indicating the presence of Cheyne-Stokes respiration from blood oxygen saturation levels measured by an oximetry signal comprising:

identifying and removing artifactual oximetry periods from the oximetry signal to produce a second signal; and

with a processor, determining a mean length of contiguous periods of resaturation in the second signal and generating a positive indication of Cheyne-Stokes respiration based on an extent of the determined mean length.

2. The method of claim 1 wherein the positive indication is generated when the extent of the determined mean length is greater than a predetermined threshold.

3. The method of claim 1, further comprising filtering the second signal to remove high frequencies.

4. The method of claim 3, further comprising performing frequency analysis on the second signal to determine an extent of oscillation in the oxygen saturation level, and wherein a positive indication of Cheyne-Stokes respiration is generated for oscillations over longer cycle times.

5. The method of claim 4, wherein the second signal is Fourier analyzed to determine the extent of oscillation in the oxygen saturation level and wherein a positive indication of Cheyne-Stokes respiration is generated for peaks in the Fourier-based spectrum at about 0.02 Hz.

6. The method of claim 4, wherein the second signal is wavelet analyzed to determine the extent of oscillation in the oxygen saturation level and wherein a positive indication of Cheyne-Stokes respiration is generated for oscillations over longer cycle times.

7. A method for indicating the presence of Cheyne-Stokes respiration from blood oxygen saturation levels measured by an oximetry signal and a ventilation flow signal comprising:

determining with a processor a delay of blood oxygen saturation level data compared to ventilation flow level data having either an apnea or hypopnea and an hyperpnoea; and

generating a positive indication of Cheyne-Stokes respiration for determined delays above a predetermined threshold.

8. A method for training a classifier to discriminate Cheyne-Stokes respiration from blood oxygen saturation levels measured by an oximetry signal comprising:

pre-classifying polysomnographic data to obtain non-overlapping epochs each with a specified class of dominating event;

with a processor, segmenting oximetry and flow recordings into non-overlapping epochs of data having a predetermined length of time; and

forming a decision boundary with a processor to discriminate Cheyne-Stokes respiration and non-Cheyne-Stokes respiration classes of events with the epochs.

9. The method of claim 8 wherein the predetermined length of time is greater than five minutes.

10. The method of claim 8, wherein the predetermined length of time is approximately 30 minutes.

11. The method of claim 8 further comprising:

determining distance from the decision boundary for each event and normalizing the distance to a probability value for each epoch.

12. The method of claim 11, wherein the predetermined length of time is approximately 30 minutes.

13. The method of claim 12, wherein the equal length epochs are as long as the recordings.

14. The method of claim 13, wherein the epoch length is approximately the length of a representative hypopnoea-hyperpnoea sequence.

15. A device for detecting the presence of Cheyne-Stokes respiration from an oximetry signal and a ventilation flow signal, wherein said device identifies and removes artifactal oximetry periods from the oximetry signal to produce an second signal;

and wherein the device determines the mean length of contiguous periods of re-saturation in the second signal and returns a positive indication of Cheyne-Stokes respiration, if said mean length is greater than a predetermined threshold.

16. The device of claim 15, wherein the device filters high frequencies from the second signal.

17. The device of claim 15, wherein said oximetry signal is compared to a first set of threshold values by a first classifier, and said ventilation flow signal is compared to a second set of threshold values by a second classifier.

18. A computer implemented method of detecting an occurrence of Cheyne-Stokes respiration with one or more programmed processors comprising:

accessing blood gas data representing a measured blood gas signal;

determining a duration of one or more contiguous periods of changing saturation of a blood gas from the blood gas data;

detecting the occurrence of Cheyne-Stokes respiration from a comparison of the determined duration and a threshold derived to differentiate saturation changes due to Cheyne-Stokes respiration and saturation changes due to obstructive sleep apnea.

19. The method of claim 18 wherein the one or more contiguous periods of changing saturation comprises re-saturation periods and the measured blood gas signal comprises an oximetry signal.

20. The method of claim 19 wherein the determined duration comprises a mean period length and wherein the detecting indicates an occurrence when the mean period length exceeds the threshold.

21. The method of claim 20 wherein the threshold comprises a discriminant function.

22. The method of claim 21 wherein the detecting the occurrence further comprises determining a distance from the threshold and comparing the distance to a further threshold.

23. The method of claim 21 further comprising determining a presence of a peak in a predetermined frequency range for de-saturation and re-saturation cycles of the blood gas data and comparing the determined presence to the discriminant function.

24. The method of claim 23 further comprising processing the blood gas data to remove artifact data.

25. The method of claim 24 further comprising measuring the blood gas with an oximeter.

26. An apparatus to detect an occurrence of Cheyne-Stokes breathing, the apparatus comprising:

a memory for blood gas data representing a measured blood gas signal;

a processor coupled with the memory, the processor being configured (a) to determine a duration of one or more contiguous periods of changing saturation of a blood gas from the blood gas data and (b) to detect an occurrence of Cheyne-Stokes respiration from a comparison of the determined duration and a threshold derived to differentiate saturation changes due to Cheyne-Stokes respiration and saturation changes due to obstructive sleep apnea.

27. The apparatus of claim 26 wherein the one or more contiguous periods of changing saturation comprises re-saturation periods and the measured blood gas signal comprises an oximetery signal.

28. The apparatus of claim 27 wherein the determined duration comprises a mean period length and wherein the detecting indicates an occurrence when the mean period length exceeds the threshold.

29. The apparatus of claim 28 wherein the threshold comprises a discriminant function.

30. The apparatus of claim 29 wherein the processor is configured to detect the occurrence by further determining a distance from the discriminant function and comparing the distance to a further threshold.

31. The apparatus of claim 29 wherein the processor is further configured to determine a presence of a peak in a predetermined frequency range for de-saturation and re-saturation cycles of the blood gas data and comparing the determined presence to the discriminant function.

32. The apparatus of claim 31 wherein the processor is further configured to process the blood gas data to remove artifact data.

33. The apparatus of claim 32 further comprising an oximeter, coupled with the processor, to generate the blood gas signal.

34. An apparatus for indicating the presence of Cheyne-Stokes respiration from blood oxygen saturation levels measured by an oximetry signal comprising:

means for identifying and removing artifactual oximetry periods from the oximetry signal to produce a second signal; and

means for determining a mean length of contiguous periods of re-saturation in the second signal and generating a positive indication of Cheyne-Stokes respiration based on an extent of the determined mean length.

35. An apparatus for indicating the presence of Cheyne-Stokes respiration from blood oxygen saturation levels measured by an oximetry signal and a ventilation flow signal comprising:

means for determining a delay of blood oxygen saturation level data compared to ventilation flow level data having either an apnea or hypopnea and an hyperpnoea; and

means for generating a positive indication of Cheyne-Stokes respiration for determined delays above a predetermined threshold.

36. An apparatus for detecting an occurrence of Cheyne-Stokes respiration comprising:

means for accessing blood gas data representing a measured blood gas signal;

means for determining a duration of one or more contiguous periods of changing saturation of a blood gas from the blood gas data;

means for detecting the occurrence of Cheyne-Stokes respiration from a comparison of the determined duration and a threshold derived to differentiate saturation changes due to Cheyne-Stokes respiration and saturation changes due to obstructive sleep apnea.