Selection of ensemble averaging weights for a pulse oximeter based on signal quality metrics

• US 9,211,090 B2
• Filed: 10/01/2013
• Issued: 12/15/2015
• Est. Priority Date: 03/08/2004
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Baker, Clark R. Jr.
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US14/043,560
• Publication Number:
  US 20140031652A1
• Time in Patent Office: 805 Days
• US Class Current: 1/1
• 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 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence

Abstract

A pulse oximeter system is presently disclosed. The pulse oximeter system includes a processor and circuitry. The processor and circuitry are configured to receive light waveforms from a sensor, determine at least one signal quality metric for the light waveforms, calculate at least one weight using a continuously variable weighting function based on the at least one signal quality metric, and ensemble average the light waveforms using the at least one calculated weight.

Claims

1. A method for monitoring a physiological status of a patient, comprising:

receiving first and second intensity signals representative of an intensity of light of first and second wavelengths, respectively, after attenuation by a patient'"'"'s tissue;

identifying and qualifying a first sample of the first or second intensity signal related to a first cardiac pulse;

averaging the first sample with a previous sample based on a first weight to provide an averaged sample;

identifying and qualifying a second sample of the first or second intensity signal related to a second cardiac pulse, the second sample being subsequent in time to the first sample;

averaging the second sample with the first averaged sample based on a second weight, to provide a second averaged sample; and

calculating a physiological parameter based on the second averaged sample, wherein the first and second weights are based at least in part on a degree of correlation between the first and second intensity signals.

2. The method of claim 1, comprising attenuating a low frequency component of the first sample prior to averaging the first sample with the previous sample.

3. The method of claim 1, wherein the physiological parameter comprises an oxygen saturation of the patient'"'"'s tissue.

4. The method of claim 1, wherein the first and second weights are continuously variable.

5. The method of claim 1, wherein the first and second weights are adjusted based on a frequency, a shape, a derivative skew, a period variability, an amplitude variability, a ratio of a current amplitude to a long-term average amplitude, a ratio of the current amplitude to a previous amplitude, or a ratio of a current pulse period to an average pulse period, or any combination thereof, of one or more of the first or the second intensity signals.

6. The method of claim 1, wherein the first and second weights are adjusted based on a degree of arrhythmia of one or more of the first or the second intensity signals.

7. The method of claim 1, comprising tracking an accumulated amount of averaging and providing an indicator when the accumulated amount passes a threshold.

8. The method of claim 1, wherein the first and second weights are adjusted based on the degree of correlation between the first and second intensity signals over a period of time.

9. The method of claim 8, wherein the period of time is about three seconds.

10. The method of claim 1, wherein the first and second wavelengths are different.

11. The method of claim 1, wherein identifying the first or second sample related to the cardiac pulse comprises examining an amplitude, a shape, or a frequency of the first or second intensity signals.

12. The method of claim 1, wherein the light of first and second wavelengths is emitted via one or more emitters of a sensor, and wherein the method comprises determining whether the sensor is positioned off of a surface of the patient'"'"'s tissue based at least in part on one or more quality metrics of the first or second intensity signals.

13. A method for monitoring a patient, comprising:

receiving first and second intensity signals representative of an intensity of light of first and second wavelengths, respectively, after attenuation by a patient'"'"'s tissue, wherein the light of first and second wavelengths is emitted via one or more emitters of a sensor;

determining one or more quality metrics of the first or second intensity signal;

identifying and qualifying a first sample of the first or second intensity signal related to a first cardiac pulse;

averaging the first sample with a previous sample based on a first weight to provide an averaged sample, wherein the first weight is based on the one or more quality metrics;

calculating a physiological parameter based on the first averaged sample; and

evaluating the one or more quality metrics to determine whether the sensor is positioned off of a surface of the patient'"'"'s tissue.

14. The method of claim 13, comprising identifying a second sample of the first or second intensity signal related to a second cardiac pulse, the second sample being subsequent in time to the first sample.

15. The method of claim 14, comprising discarding the second sample if it is determined that the sensor is positioned off of the surface of the patient'"'"'s tissue.

16. The method of claim 14, comprising averaging the second sample with the first averaged sample based on a second weight, to provide a second averaged sample, if it is determined that the sensor is not positioned off of the surface of the patient'"'"'s tissue.

17. The method of claim 13, wherein the first weight is based on the degree of correlation between the first and second intensity signals.

18. The method of claim 13, wherein the first weight is continuously variable.

19. The method of claim 13, wherein the one or more quality metrics comprise a frequency, a shape, a derivative skew, a period variability, an amplitude variability, a ratio of a current amplitude to a long-term average amplitude, a ratio of the current amplitude to a previous amplitude, or a ratio of a current pulse period to an average pulse period, or any combination thereof.

20. The method of claim 13, wherein the first and second wavelengths are different.