METHODS AND SYSTEMS FOR QUALIFYING PHYSIOLOGICAL VALUES BASED ON SEGMENTS FROM A CROSS-CORRELATION SEQUENCE

• US 20140073963A1
• Filed: 09/11/2012
• Published: 03/13/2014
• Est. Priority Date: 09/11/2012
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Engelbrecht, Pirow, Rodriguez-Llorente, Fernando, Wooder, Nicholas James
• Granted Patent: US 9,392,974 B2
• Time in Patent Office: Days
• US Class Current: 600/479
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02444 Details of sensor A61B5/02427 takes precedence
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A physiological monitoring system may process a physiological signal such a photoplethysmograph signal from a subject. The system may determine physiological information, such as a physiological rate, from the physiological signal. The system may use search techniques and qualification techniques to determine one or more initialization parameters. The initialization parameters may be used to calculate and qualify a physiological rate. The system may use signal conditioning to reduce noise in the physiological signal and to improve the determination of physiological information. The system may use qualification techniques to confirm determined physiological parameters. The system may also use autocorrelation techniques, cross-correlation techniques, fast start techniques, and/or reference waveforms when processing the physiological signal.

Claims

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

a sensor configured to generate an intensity signal, wherein the sensor detects light attenuated by the subject; and

processing equipment coupled to the sensor, wherein the processing equipment is configured to;

determine a value indicative of a physiological rate of the subject;

perform a cross-correlation sequence based on the intensity signal and a reference waveform;

select two segments from the cross-correlation sequence; and

determine whether to qualify the value indicative of the physiological rate of the subject based on the two segments.

2. The system of claim 1, wherein the two segment are approximately the same size, wherein the starting points of the two segments are offset by a quarter of a period, wherein the period is associated with the value indicative of the physiological rate, and wherein the size is approximately equal to or greater than the period.

3. The system of claim 1, wherein the processing equipment is further configured to calculate differences based on the two segments, wherein the calculation of each difference is based on a value from a first of the two segments and a value from a second of the two segments.

4. The system of claim 3, wherein the processing equipment is further configured to determine whether to qualify the value indicative of the physiological rate based on a maximum and a minimum of the differences.

5. The system of claim 1, wherein the processing equipment is further configured to calculate angles based on the two segments, wherein the calculation of each angle is based on a value from a first of the two segments and a value from a second of the two segments.

6. The system of claim 5, wherein the processing equipment is further configured to determine whether to qualify the value indicative of the physiological rate based on an angle sum of the angles.

7. The system of claim 1, wherein the processing equipment is further configured to not use the value indicative of the physiological rate in calculating a display rate when the value is not qualified.

8. The system of claim 1, wherein the processing equipment is further configured to filter the value indicative of the physiological rate in a rate filter, wherein a filter weight associated with the value is decreased when the value is not qualified.

9. The system of claim 1, wherein the intensity signal is a photoplethysmograph signal and wherein the value indicative of the physiological rate is a value indicative of a pulse rate.

10. A processing module for determining physiological information of a subject, wherein the processing module is configured to:

receive an intensity signal from a detector, wherein the detector detects light attenuated by the subject;

determine a value indicative of a physiological rate of the subject;

perform a cross-correlation sequence based on the intensity signal and a reference waveform;

select two segments from the cross-correlation sequence; and

determine whether to qualify the value indicative of the physiological rate of the subject based on the two segments.

11. The processing module of claim 10, wherein the two segment are approximately the same size, wherein the starting points of the two segments are offset by a quarter of a period, wherein the period is associated with the value indicative of the physiological rate, and wherein the size is approximately equal to or greater than the period.

12. The processing module of claim 10, further configured to calculate differences based on the two segments, wherein the calculation of each difference is based on a value from a first of the two segments and a value from a second of the two segments.

13. The processing module of claim 12, further configured to determine whether to qualify the value indicative of the physiological rate based on a maximum and a minimum of the differences.

14. The processing module of claim 10, further configured to calculate angles based on the two segments, wherein the calculation of each angle is based on a value from a first of the two segments and a value from a second of the two segments.

15. The processing module of claim 14, further configured to determine whether to qualify the value indicative of the physiological rate based on an angle sum of the angles.

16. The processing module of claim 10, further configured to not use the value indicative of the physiological rate in calculating a display rate when the value is not qualified.

17. The processing module of claim 10, further configured to filter the value indicative of the physiological rate in a rate filter, wherein a filter weight associated with the value is decreased when the value is not qualified.

18. The processing module of claim 10, wherein the intensity signal is a photoplethysmograph signal and wherein the value indicative of the physiological rate is a value indicative of a pulse rate.

19. A method for processing physiological information of a subject, comprising:

receiving an intensity signal from a detector, which detects light attenuated by the subject;

determining a value indicative of a physiological rate of the subject;

performing a cross-correlation sequence based on the intensity signal and a reference waveform;

selecting two segments from the cross-correlation sequence; and

determining, using processing equipment, whether to qualify the value indicative of the physiological rate of the subject based on the two segments.

20. The method of claim 19, wherein the two segment are approximately the same size, wherein the starting points of the two segments are offset by a quarter of a period, wherein the period is associated with the value indicative of the physiological rate, and wherein the size is approximately equal to or greater than the period.

21. The method of claim 19, further comprising calculating differences based on the two segments, wherein the calculation of each difference is based on a value from a first of the two segments and a value from a second of the two segments.

22. The method of claim 21, wherein the determining whether to qualify the value indicative of the physiological rate comprises determining whether to qualify the value indicative of the physiological rate based on a maximum and a minimum of the differences.

23. The method of claim 19, further comprising calculating angles based on the two segments, wherein the calculation of each angle is based on a value from a first of the two segments and a value from a second of the two segments.

24. The method of claim 23, wherein the determining whether to qualify the value indicative of the physiological rate comprises determining whether to qualify the value indicative of the physiological rate based on an angle sum of the angles.

25. The method of claim 19, further comprising not using the value indicative of the physiological rate in calculating a display rate when the value is not qualified.

26. The method of claim 19, further comprising filtering the value indicative of the physiological rate in a rate filter, wherein a filter weight associated with the value is decreased when the value is not qualified.

27. The method of claim 19, wherein the intensity signal is a photoplethysmograph signal and wherein the value indicative of the physiological rate is a value indicative of a pulse rate.

28. A computer-readable medium for use in determining physiological information of a subject, the computer-readable medium having computer program instructions recorded thereon for:

receiving an intensity signal from a detector, which detects light attenuated by the subject;

determining a value indicative of a physiological rate of the subject;

performing a cross-correlation sequence based on the intensity signal and a reference waveform;

selecting two segments from the cross-correlation sequence; and

determining whether to qualify the value indicative of the physiological rate of the subject based on the two segments.

29. The computer-readable medium of claim 28, wherein the two segment are approximately the same size, wherein the starting points of the two segments are offset by a quarter of a period, wherein the period is associated with the value indicative of the physiological rate, and wherein the size is approximately equal to or greater than the period.

30. The computer-readable medium of claim 28, having further computer program instructions recorded thereon for calculating differences based on the two segments, wherein the calculation of each difference is based on a value from a first of the two segments and a value from a second of the two segments.

31. The computer-readable medium of claim 30, having further computer program instructions recorded thereon for determining whether to qualify the value indicative of the physiological rate based on a maximum and a minimum of the differences.

32. The computer-readable medium of claim 28, having further computer program instructions recorded thereon for calculating angles based on the two segments, wherein the calculation of each angle is based on a value from a first of the two segments and a value from a second of the two segments.

33. The computer-readable medium of claim 32, having further computer program instructions recorded thereon for determining whether to qualify the value indicative of the physiological rate based on an angle sum of the angles.

34. The computer-readable medium of claim 28, having further computer program instructions recorded thereon for not using the value indicative of the physiological rate in calculating a display rate when the value is not qualified.

35. The computer-readable medium of claim 28, having further computer program instructions recorded thereon for filtering the value indicative of the physiological rate in a rate filter, wherein a filter weight associated with the value is decreased when the value is not qualified.

36. The computer-readable medium of claim 28, wherein the intensity signal is a photoplethysmograph signal and wherein the value indicative of the physiological rate is a value indicative of a pulse rate.