Selection of Ensemble Averaging Weights for a Pulse Oximeter Based on Signal Quality Metrics

• US 20110092785A1
• Filed: 12/28/2010
• Published: 04/21/2011
• Est. Priority Date: 03/08/2004
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Baker, Clark R. JR.
• Granted Patent: US 8,560,036 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• 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 pulse oximeter, comprising:

a signal processing architecture comprising;

a signal conditioner configured to receive light waveforms and provide conditioned light waveforms with attenuated low frequencies associated with motion artifact and emphasized high frequencies associate with a human plethysmograph;

a signal metrics calculator configured to compute signal quality metrics of the light waveforms based on characteristics of the light waveforms and based on the conditioned light waveforms;

an ensemble averager configured to ensemble average the conditioned light waveforms with continuously variable ensemble averaging weights based on the signal quality metrics to provide filtered light waveforms; and

a filtered pulse identifier and qualifier configured to receive the filtered light waveforms and identify qualified pulse periods based on the filtered light waveforms.

2. The pulse oximeter of claim 1, wherein the signal processing architecture comprises a pulse rate calculator configured to receive data regarding the qualified pulse periods and calculate a pulse rate and average pulse period.

3. The pulse oximeter of claim 1, wherein the signal processing architecture comprises a low pass filter configured to receive and low pass filter the conditioned light waveforms with continuously variable low pass filter weights based on the signal quality metrics.

4. The pulse oximeter of claim 1, wherein the signal metrics calculator is configured to provide an indication of whether the light waveforms are degraded based on the characteristics.

5. The pulse oximeter of claim 4, wherein the characteristics comprise pulse shape, period variability, pulse amplitude, pulse variability, ratio of ratios variability, frequency content relative to pulse rate, or any combination thereof.

6. The pulse oximeter of claim 4, wherein the continuously variable ensemble averaging weights are devalued when the light waveforms are indicated as degraded.

7. The pulse oximeter of claim 1, wherein the signal conditioner is configured to receive digitized red light waveforms and digitized infrared light waveforms.

8. The pulse oximeter of claim 1, wherein the ensemble averager is configured to track an age of the light waveforms and/or an accumulated amount of filtering.

9. The pulse oximeter of claim 8, wherein the ensemble averager is configured to flag data associated with light waveforms with an age value that exceeds a threshold.

10. A pulse oximeter system, comprising:

a processor and circuitry 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 to provide a pulse rate calculation or blood oxygenation calculation.

11. The pulse oximeter system of claim 10, comprising the sensor, wherein the sensor is configured receive first and second light waveforms from tissue, and wherein the first and second light waveforms correspond to two different wavelengths of light.

12. The pulse oximeter system of claim 11, wherein the first light waveform corresponds to a red wavelength and the second light waveform corresponds to an infrared wavelength.

13. The pulse oximeter system of claim 10, wherein the processor and circuitry are configured to measure a degree of variability of a ratio of ratios of the light waveforms to determine the at least one signal quality metric.

14. The pulse oximeter system of claim 10, wherein the signal quality metric determination is based on pulse shape, period variability, pulse amplitude, pulse variability, ratio of ratios variability, frequency content relative to pulse rate, or any combination thereof.

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

receiving light waveforms from a sensor into a signal processor of a pulse oximeter;

determining at least one signal quality metric for the light waveforms with the signal processor;

calculating at least one weight with the signal processor using a continuously variable weighting function based on the at least one signal quality metric; and

ensemble averaging the light waveforms with the signal processor using the at least one calculated weight to provide a pulse rate calculation or blood oxygenation calculation.

16. The method of claim 15, comprising emitting light waveforms from an emitter of a sensor and detecting the light waveforms with a detector of the sensor.

17. The method of claim 15, wherein determining the at least one signal quality metric comprises identifying whether at least a portion of the light waveforms are noise.

18. The method of claim 15, wherein determining the at least one signal quality metric comprises analyzing frequency, shape, and/or rise time of the light waveforms.

19. The method of claim 15, comprising identifying pulses based on the light waveforms and analyzing the pulses to determine whether the pulses are arterial pulses.

20. The method of claim 15, comprising monitoring an age of the light waveforms and flagging data associated with light waveforms over a certain age.