ADJUSTING PARAMETERS USED IN PULSE OXIMETRY ANALYSIS

• US 20090253971A1
• Filed: 06/12/2009
• Published: 10/08/2009
• Est. Priority Date: 10/28/2005
• 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 8,238,994 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence

Abstract

Adjusting a pulse qualification criterion includes receiving a signal representing a plurality of pulses, where the signal is generated in response to detecting light scattered from blood perfused tissue. A characteristic is determined. A pulse qualification criterion used for qualifying a pulse is adjusted in accordance with the characteristic. The pulses are evaluated according to the pulse qualification criterion.

Claims

1. A method for adjusting a weight of a saturation filtering process, comprising:

receiving a signal from a sensor representing one or more pulses, the signal generated in response to detecting light scattered from blood perfused tissue, the light comprising a first wavelength and a second wavelength; and

using a processor;

determining a ratio-of-ratios variability metric indicating the variation of a ratio-of-ratios, a ratio-of-ratios representing the ratio of absorbances of the first wavelength and the second wavelength;

determining a pulse quality metric indicating the quality of the one or more pulses; and

adjusting a saturation weight in accordance with the ratio-of-ratios variability metric and the pulse quality metric, the saturation weight representing a weight used for a filtering process operable to filter a saturation estimate of the blood perfused tissue.

2. The method of claim 1, comprising:

establishing that the filtering process is in a predetermined response mode.

3. The method of claim 1, wherein adjusting a saturation weight in accordance with the ratio-of-ratios variability metric and the pulse quality metric further comprises:

modifying a noise variance in accordance with the pulse quality metric; and

adjusting the saturation weight in accordance with the modified noise variance.

4. The method of claim 1, wherein the saturation weight is calculated by a Kalman filter.

5. A method for calculating saturation, comprising:

receiving a signal from a sensor representing one or more pulses, the signal generated in response to detecting light scattered from blood perfused tissue, the light comprising a first wavelength and a second wavelength;

using a processor;

determining a pulse quality metric indicating the quality of the one or more pulses;

determining a ratio-of-ratios variability metric indicating the variation of a ratio-of-ratios, a ratio-of-ratios representing the ratio of absorbances of the first wavelength and the second wavelength;

establishing a ratio-of-ratios weight in accordance with the ratio-of-ratios variability metric and the pulse quality metric;

filtering the ratio-of-ratios in accordance with the ratio-of-ratios weight; and

calculating saturation according to the filtered ratio-of ratios; and

displaying the saturation on a display.

6. The method of claim 5, comprising:

establishing that the filtering process is in a predetermined response mode.

7. A system operable to adjust a weight of a saturation filtering process, comprising:

an interface operable to;

receive a signal representing one or more pulses, the signal generated in response to detecting light scattered from blood perfused tissue, the light comprising a first wavelength and a second wavelength; and

a processor operable to;

determine a ratio-of-ratios variability metric indicating the variation of a ratio-of-ratios, a ratio-of-ratios representing the ratio of absorbances of the first wavelength and the second wavelength;

determine a pulse quality metric indicating the quality of the one or more pulses; and

adjust a saturation weight in accordance with the ratio-of-ratios variability metric and the pulse quality metric, a saturation weight representing a weight used for a filtering process operable to filter the saturation estimate of the blood perfused tissue.

8. The system of claim 7, the processor further operable to:

establish that the filtering process is in a predetermined response mode.

9. The system of claim 7, the processor further operable to adjust a saturation weight in accordance with the ratio-of-ratios variability metric and the pulse quality metric by:

modifying a noise variance in accordance with the pulse quality metric; and

adjusting the saturation weight in accordance with the modified noise variance.

10. The system of claim 7, wherein the saturation weight is calculated by a Kalman filter.

11. A system for adjusting a weight of a saturation filtering process, comprising:

an interface operable to;

receive a signal representing one or more pulses, the signal generated in response to detecting light scattered from blood perfused tissue, the light comprising a first wavelength and a second wavelength; and

a processor operable to;

determine a pulse quality metric indicating the quality of the one or more pulses;

determine a ratio-of-ratios variability metric indicating the variation of a ratio-of-ratios, a ratio-of-ratios representing the ratio of absorbances of the first wavelength and the second wavelength;

establish a ratio-of-ratios weight in accordance with the ratio-of-ratios variability metric and the pulse quality metric;

filter the ratio-of-ratios in accordance with the ratio-of-ratios weight; and

calculate saturation according to the filtered ratio-of ratios.

12. The system of claim 11, the processor further operable to establish that the filtering process is in a predetermined response mode.

13. A system for adjusting a weight of a saturation filtering process, comprising:

means for receiving a signal representing one or more pulses, the signal generated in response to detecting light scattered from blood perfused tissue, the light comprising a first wavelength and a second wavelength;

means for determining a ratio-of-ratios variability metric indicating the variation of a ratio-of-ratios, a ratio-of-ratios representing the ratio of absorbances of the first wavelength and the second wavelength;

means for determining a pulse quality metric indicating the quality of the one or more pulses; and

means for adjusting a saturation weight in accordance with the ratio-of-ratios variability metric and the pulse quality metric, the saturation weight representing a weight used for a filtering process operable to filter a saturation estimate of the blood perfused tissue.

14. A system operable to adjust a weight of a saturation filtering process, comprising:

an interface operable to;

receive a signal representing one or more pulses, the signal generated in response to detecting light scattered from blood perfused tissue, the light comprising a first wavelength and a second wavelength; and

a processor operable to;

determine a ratio-of-ratios variability metric indicating the variation of a ratio-of-ratios, a ratio-of-ratios representing the ratio of absorbances of the first wavelength and the second wavelength;

determine a pulse quality metric indicating the quality of the one or more pulses;

establish that the filtering process is in a predetermined response mode; and

adjust a saturation weight in accordance with the ratio-of-ratios variability metric and the pulse quality metric, the saturation weight representing a weight used for a filtering process operable to filter a saturation estimate of the blood perfused tissue, the saturation weight calculated by a Kalman filter, the saturation weight adjusted by;

modifying a noise variance in accordance with the pulse quality metric; and

adjusting the saturation weight in accordance with the modified noise variance.

15. A system, comprising:

a sensor comprising;

one or more light sources adapted to emit light at a first wavelength and a second wavelength into blood perfused tissue; and

a photodetector adapted to detect the light scattered from the blood perfused tissue; and

a monitor comprising;

an interface adapted to couple the sensor to the monitor, the interface operable to receive a signal representing one or more pulses based on the detected light; and

a processor operable to;

determine a ratio-of-ratios variability metric indicating the variation of a ratio-of-ratios, a ratio-of-ratios representing the ratio of absorbances of the first wavelength and the second wavelength;

determine a pulse quality metric indicating the quality of the one or more pulses; and

adjust a saturation weight in accordance with the ratio-of-ratios variability metric and the pulse quality metric, a saturation weight representing a weight used for a filtering process operable to filter the saturation estimate of the blood perfused tissue.

16. The system of claim 15, the processor further operable to adjust a saturation weight in accordance with the ratio-of-ratios variability metric and the pulse quality metric by:

modifying a noise variance in accordance with the pulse quality metric; and

adjusting the saturation weight in accordance with the modified noise variance.

17. The system of claim 15, wherein the saturation weight is calculated by a Kalman filter.

18. A system, comprising:

a sensor comprising;

one or more light sources adapted to emit light at a first wavelength and a second wavelength into blood perfused tissue; and

a photodetector adapted to detect the light scattered from the blood perfused tissue; and

a monitor comprising;

an interface adapted to couple the sensor to the monitor, the interface operable to receive a signal representing one or more pulses based on the detected light;

a processor operable to;

determine a pulse quality metric indicating the quality of the one or more pulses;

determine a ratio-of-ratios variability metric indicating the variation of a ratio-of-ratios, a ratio-of-ratios representing the ratio of absorbances of the first wavelength and the second wavelength;

establish a ratio-of-ratios weight in accordance with the ratio-of-ratios variability metric and the pulse quality metric;

filter the ratio-of-ratios in accordance with the ratio-of-ratios weight; and

calculate saturation according to the filtered ratio-of ratios; and

a display operable to display the calculated saturation.

19. The system of claim 18, the processor further operable to:

establish that the filtering process is in a predetermined response mode.