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

• US 20090082651A1
• Filed: 12/03/2008
• Published: 03/26/2009
• Est. Priority Date: 03/08/2004
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc), Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Baker, Clark R. JR.
• Granted Patent: US 7,890,154 B2
• Time in Patent Office: Days
• US Class Current: 600/324
• 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 method and a system for ensemble averaging signals in a pulse oximeter, including receiving first and second electromagnetic radiation signals from a blood perfused tissue portion corresponding to two different wavelengths of light, obtaining an assessment of the signal quality of the electromagnetic signals, selecting weights for an ensemble averager using the assessment of signal quality, and ensemble averaging the electromagnetic signals using the ensemble averager.

Claims

1. A method of ensemble averaging signals in a pulse oximeter, comprising:

receiving, via a sensor, first and second electromagnetic radiation signals from a blood perfused tissue portion corresponding to two different wavelengths of light; and

using an oximeter,

obtaining an assessment of the signal quality of the electromagnetic signals;

calculating weights for an ensemble averager from a continuous weighting function based at least in part upon the assessment of signal quality; and

ensemble averaging the electromagnetic signals using the ensemble averager.

2. The method of claim 1, wherein the obtaining an assessment of the signal quality comprises obtaining a measure of a degree of arrhythmia of the signals.

3. The method of claim 2, wherein the obtaining an assessment of the signal quality further comprises obtaining a measure of a degree of similarity or correlation between the first and second electromagnetic radiation signals.

4. The method of claim 1, wherein the obtaining an assessment of the signal quality comprises obtaining a measure of a degree of motion artifact present in the signals.

5. The method of claim 4, wherein the obtaining a measure of the degree of motion artifact comprises obtaining a ratio of a current pulse amplitude to a long-term average pulse amplitude of the signals.

6. The method of claim 1, wherein the obtaining an assessment of the signal quality comprises obtaining a ratio of a current pulse amplitude to a previous pulse amplitude of the signal.

7. The method of claim 1, wherein the obtaining an assessment of the signal quality comprises obtaining a measure of a degree of the overall signal quality metric for a single pulse, which comprises a combination of other metrics.

8. The method of claim 1, wherein the obtaining an assessment of the signal quality comprises obtaining a ratio of a current pulse period to an average pulse period of the signals.

9. The method of claim 1, wherein the calculating weights comprises forming a combination of one or more parameters comprising a measure of a degree of arrhythmia of the signals, a measure of the degree of similarity or correlation between the first and second electromagnetic radiation signals, a measure of a degree of motion artifact by obtaining a ratio of a current pulse amplitude to a long-term average pulse amplitude of the signals, a ratio of a current pulse amplitude to a previous pulse amplitude of the signal, and/or a ratio of a current pulse period to an average pulse period of the signals.

14. The pulse oximetry system of claim 1, wherein the first weight is based at least in part upon a pulse qualification score.

10. A pulse oximetry system, comprising:

a sensor capable of receiving first and second electromagnetic signals from a blood perfused tissue portion corresponding to two different wavelengths of light; and

a pulse oximeter capable of;

obtaining an assessment of a signal quality of the first and second electromagnetic signals;

calculating a first weight associated with the first and second electromagnetic signals for an oxygen saturation ensemble averager and/or calculating a second weight associated with the first and second electromagnetic signals for a pulse rate ensemble averager using at least one continuously variable weighting function based at least in part upon the assessment of the signal quality; and

calculating an oxygen saturation value with an oxygen saturation averager based on the first weight and the first and second electromagnetic signals and/or calculating a pulse rate value with the pulse rate ensemble averager based at least in part upon the second weight and the first and second electromagnetic signals.

11. The pulse oximetry system of claim 10, wherein the pulse oximeter is capable of obtaining the assessment of the signal quality at least in part by determining a correlation between the first and second electromagnetic radiation signals.

12. The pulse oximetry system of claim 10, wherein the pulse oximeter is capable of measuring a degree of variability of a ratio-of-ratios of the first and second electromagnetic signals to obtain the assessment of the signal quality.

13. The pulse oximetry system of claim 10, wherein the first weight is based at least in part upon a variability of a ratio-of-ratios over a time.

15. The pulse oximetry system of claim 10, wherein the pulse oximeter is capable of normalizing the first and second electromagnetic signals.

16. The pulse oximetry system of claim 10, comprising a filter capable of low pass filtering the first and second electromagnetic signals.

17. A pulse oximetry system, comprising:

a sensor capable of receiving first and second electromagnetic signals from a blood perfused tissue portion corresponding to two different wavelengths of light; and

a pulse oximeter capable of;

obtaining an assessment of a signal quality of the first and second electromagnetic signals, wherein the assessment comprises a determination of whether arrhythmia is present;

calculating a weight associated with the first and second electromagnetic signals for an ensemble averager using at least one continuously variable weighting function based at least in part upon the assessment of the signal quality; and

calculating an oxygen saturation value with the ensemble averager based at least in part upon the determination of whether arrhythmia is present, the weight, and the first and second electromagnetic signals.

18. The pulse oximetry system of claim 17, wherein the pulse oximetry system is capable of reducing a degree of ensemble-averaging when arrhythmia is present.

19. The pulse oximetry system of claim 17, wherein the ensemble averager comprises a pulse rate ensemble averager and/or an oxygen saturation ensemble averager.

20. The pulse oximetry system of claim 17, wherein the weight is based in part on a variability of a ratio-of-ratios over a time.