METHOD FOR ENHANCING PULSE OXIMETRY CALCULATIONS IN THE PRESENCE OF CORRELATED ARTIFACTS

• US 20140343385A1
• Filed: 08/04/2014
• Published: 11/20/2014
• Est. Priority Date: 03/03/2005
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Baker, Clark R. Jr.
• Granted Patent: US 9,351,674 B2
• Time in Patent Office: Days
• US Class Current: 600/336
• 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 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7214 using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths

Abstract

Methods and systems for determining a physiological parameter in the presence of correlated artifact are provided. One method includes receiving two waveforms corresponding to two different wavelengths of light from a patient. Each of the two waveforms includes a correlated artifact. The method also includes combining the two waveforms to form a plurality of weighted difference waveforms, wherein the plurality of weighted difference waveforms vary from one another by a value of a multiplier. The method further includes identifying one of the weighted difference waveforms from the plurality of weighted difference waveforms using a characteristic of one or more of the plurality of weighted difference waveforms and determining a characteristic of the correlated artifact based at least in part on the identified weighted difference waveform.

Claims

1. A medical monitor, comprising:

a light drive configured to drive one or more light emitters;

circuitry configured to receive signals from one or more photodetectors, wherein the signals comprise a correlated artifact;

a memory storing instructions configured to;

combine the plurality of received signals to form a plurality of weighted difference waveforms;

identify a weighted difference waveform from the plurality of weighted difference waveforms that most or least closely resembles a plethysmographic waveform; and

determine a physiological parameter based at least in part on the identified weighted difference waveform; and

a processor configured to execute the instructions.

2. The medical monitor of claim 1, wherein the memory stores instructions configured to identify a weighted difference waveforms from the plurality of weighted difference waveforms by identifying the waveform that least closely resembles a plethysmographic waveform.

3. The medical monitor of claim 2, wherein the memory stores instructions configured to determine a least representative physiological parameter based at least in part on the waveform that least closely resembles a plethysmographic waveform.

4. The medical monitor of claim 3, wherein the memory stores instructions configured to identify physiological parameter measurements that are associated with the correlated artifact.

5. The medical monitor of claim 4, wherein the memory stores instructions configured to disregard physiological parameter measurements that are associated with the correlated artifact when determining the physiological parameter.

6. The medical monitor of claim 1, wherein the correlated artifact comprises an artifact caused by patient motion, a respiratory artifact, an electronic interference artifact, or a combination thereof.

20. The medical monitor of claim 3, wherein the memory stores instructions configured to identify physiological parameter measurements that are associated with the correlated artifact.

7. A pulse oximetry system comprising:

a sensor configured to detect electromagnetic radiation signals corresponding to different wavelengths of light; and

a processor configured to;

receive the signals corresponding to the different wavelengths of light from the sensor;

combine the signals to form a plurality of weighted difference waveforms that vary by a multiplier;

determine a physiological parameter measurement based at least in part on the signals; and

determine that the physiological parameter is valid based on its association with a waveform of the plurality of weighted difference waveforms that most closely resembles a plethysmographic waveform.

8. The system of claim 7, wherein the processor is configured to determine the physiological parameter is invalid based on its association with a waveform of the plurality of weighted difference waveforms that least closely resembles a plethysmographic waveform.

9. The system of claim 8, wherein the waveform of the plurality of weighted difference waveforms that least closely resembles a plethysmographic waveform has a characteristic skew associated with an artifact.

10. The system of claim 7, wherein the waveform of the plurality of weighted difference waveforms that most closely resembles a plethysmographic waveform has a skew associated with a pulse.

11. The system of claim 7, wherein the waveform of the plurality of weighted difference waveforms that most closely resembles a plethysmographic waveform has a derivative skew associated with a pulse.

12. The system of claim 7, wherein the waveform of the plurality of weighted difference waveforms that most closely resembles a plethysmographic waveform has a pulse amplitude associated with a pulse.

13. The system of claim 7, wherein the waveform of the plurality of weighted difference waveforms that most closely resembles a plethysmographic waveform has a ratio of ratios variability associated with a pulse.

14. The system of claim 7, wherein the waveform of the plurality of weighted difference waveforms that most closely resembles a plethysmographic waveform has a pulse amplitude variability associated with a pulse.

15. A medical monitor, comprising:

a light drive configured to drive one or more light emitters;

circuitry configured to receive a signal from one or more photodetectors;

a memory storing instructions configured to;

determine a pulse shape of the signal based on a min-max-min indicator, wherein the min-max-min indicator for a pulse corresponds to a time from max-min over a time from min-max;

determine if the pulse shape is associated with a valid pulse; and

determine a physiological parameter measurement based at least in part on the signal when the signal is associated with the valid pulse; and

a processor configured to execute the instructions.

16. The medical monitor of claim 15, wherein the pulse shape is not associated with a valid pulse when a pulse rise time is greater than a pulse fall time such that the min-max-min indicator is less than 1.

17. The medical monitor of claim 15, wherein the pulse shape is associated with a valid pulse when a pulse rise time is less than a pulse fall time such that the min-max-min indicator is greater than 1.

18. The medical monitor of claim 15, wherein the memory stores instructions configured to identify physiological parameter measurements that are associated with the correlated artifact.

19. The medical monitor of claim 15, wherein the memory stores instructions configured to disregard the signal when the signal is not associated with the valid pulse.