Methods and systems for qualifying a correlation lag value based on a correlation value at a different lag

• US 9,186,101 B2
• Filed: 09/11/2012
• Issued: 11/17/2015
• Est. Priority Date: 09/11/2012
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Rodriguez-Llorente, Fernando, Engelbrecht, Pirow, Wooder, Nicholas James
• Primary Examiner(s): Le, Long V
• Assistant Examiner(s): Negarestan, Farshad
• Application Number:
  US13/609,493
• Publication Number:
  US 20140073944A1
• Time in Patent Office: 1,162 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• 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: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A physiological monitoring system may determine physiological information, such as physiological rate information, from a physiological signal. The system may generate a correlation sequence using two segments of the physiological signal. The system may determine a first correlation lag value that corresponds to a peak in the correlation sequence, and also determine a second correlation lag value equal to a fraction of the first correlation lag value. The fraction may be, for example, one half. The system may qualify or disqualify the correlation lag value based on the correlation value at the second lag value. The system may compare the correlation value at the second lag value to a threshold, to the correlation sequence at the first lag value, or both.

Claims

1. A subject monitoring system for processing physiological information of a subject, comprising:

a pulse oximetry sensor configured to generate a physiological signal, wherein the pulse oximetry sensor detects light attenuated by the subject; and

a pulse oximeter coupled to the pulse oximetry sensor, wherein the pulse oximeter is configured to;

determine a first correlation lag value corresponding to a peak in a correlation sequence derived from the physiological signal;

determine a correlation value at a second correlation lag value equal to a fraction of the first correlation lag value;

qualify or disqualify the first correlation lag value as being indicative of a physiological rate of the subject based on the correlation value at the second correlation lag value;

determine the physiological rate of the subject based on the first correlation lag value when the first correlation lag value is qualified; and

display the physiological rate of the subject on a display.

2. The system of claim 1, wherein the second correlation lag value is equal to substantially one half of the first correlation lag value.

3. The system of claim 1, wherein the pulse oximeter is further configured to compare the correlation value at the second correlation lag value to a threshold.

4. The system of claim 1, wherein the pulse oximeter is further configured to compare the correlation value at the second correlation lag value to a value in the correlation sequence corresponding to the first correlation lag value.

5. The system of claim 1, wherein the physiological signal is a photoplethysmograph signal and wherein the first correlation lag value corresponds to a period associated with the physiological rate.

6. A processing module of a pulse oximeter for processing physiological information of a subject, wherein the processing module is configured to:

receive a physiological signal derived from an output of a detector of a pulse oximetry sensor, wherein the detector detects light attenuated by the subject;

determine a first correlation lag value corresponding to a peak in a correlation sequence derived from the physiological signal;

determine a correlation value at a second correlation lag value equal to a fraction of the first correlation lag value;

qualify or disqualify the first correlation lag value as being indicative of a physiological rate of the subject based on the correlation value at the second correlation lag value;

determine the physiological rate of the subject based on the first correlation lag value when the first correlation lag value is qualified; and

display the physiological rate of the subject on a display.

7. The processing module of claim 6, wherein the second correlation lag value is equal to substantially one half of the first correlation lag value.

8. The processing module of claim 6, further configured to compare the correlation value at the second correlation lag value to a threshold.

9. The processing module of claim 6, further configured to compare the correlation value at the second correlation lag value to a value in the correlation sequence corresponding to the first correlation lag value.

10. The processing module of claim 6, wherein the physiological signal is a photoplethysmograph signal and wherein the first correlation lag value corresponds to a period associated with the physiological rate.

11. A method for processing physiological information of a subject using a pulse oximeter, comprising:

receiving, using the pulse oximeter, a physiological signal derived from an output of a detector a pulse oximetry sensor, wherein the detector detects light attenuated by the subject;

determining, using the pulse oximeter, a first correlation lag value corresponding to a peak in a correlation sequence derived from the physiological signal;

determining, using the pulse oximeter, a correlation value at a second correlation lag value equal to a fraction of the first correlation lag value;

qualifying or disqualifying, using the pulse oximeter, the first correlation lag value as being indicative of a physiological rate of the subject based on the correlation value at the second correlation lag value;

determining, using the pulse oximeter, the physiological rate of the subject based on the first correlation lag value when the first correlation lag value is qualified; and

displaying, using the pulse oximeter, the physiological rate of the subject on a display.

12. The method of claim 11, wherein the second correlation lag value is equal to substantially one half of the first correlation lag value.

13. The method of claim 11, wherein qualifying or disqualifying the first correlation lag value comprises comparing the correlation value at the second correlation lag value to a threshold.

14. The method of claim 11, wherein qualifying or disqualifying the first correlation lag value comprises comparing the correlation value at the second correlation lag value to a value in the correlation sequence corresponding to the first correlation lag value.

15. The method of claim 11, wherein the physiological signal is a photoplethysmograph signal and wherein the first correlation lag value corresponds to a period associated with the physiological rate.

16. A non-transitory computer-readable medium for use in processing physiological information of a subject, the computer-readable medium comprising:

computer program instructions recorded thereon for causing a pulse oximeter to;

receive a physiological signal derived from an output of a detector of a pulse oximetry sensor, wherein the detector detects light attenuated by the subject;

determine a first correlation lag value corresponding to a peak in a correlation sequence derived from the physiological signal;

determine a correlation value at a second correlation lag value equal to a fraction of the first correlation lag value;

qualify or disqualify the first correlation lag value as being indicative of a physiological rate of the subject based on the correlation value at the second correlation lag value;

determine the physiological rate of the subject based on the first correlation lag value when the first correlation lag value is qualified; and

display the physiological rate of the subject on a display.

17. The non-transitory computer-readable medium of claim 16, wherein the second correlation lag value is equal to substantially one half of the first correlation lag value.

18. The non-transitory computer-readable medium of claim 16, comprising further computer program instructions recorded thereon for causing the pulse oximeter to compare the correlation value at the second correlation lag value to a threshold.

19. The non-transitory computer-readable medium of claim 16, comprising further computer program instructions recorded thereon for causing the pulse oximeter to compare the correlation value at the second correlation lag value to a value in the correlation sequence corresponding to the first correlation lag value.

20. The non-transitory computer-readable medium of claim 16, wherein the physiological signal is a photoplethysmograph signal and wherein the first correlation lag value corresponds to a period associated with a physiological rate.