Signal quality metrics design for qualifying data for a physiological monitor

• US 20060135860A1
• Filed: 12/02/2005
• Published: 06/22/2006
• Est. Priority Date: 01/10/2003
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Baker, Clark R. Jr., Richards, Edward M.
• Granted Patent: US 8,095,192 B2
• Time in Patent Office: Days
• US Class Current: 600/310
• 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 5/145 Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissuemeasuring of blood pressure or blood flow A61B5/02; non-radiation detecting or locating of foreign bodies in blood A61B5/06
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

A method and a device for determining the quality of signal used for measuring a physiological parameter. One embodiment of the present invention is directed towards a pulse oximeter, where the measured physiological parameter includes a patient'"'"'s pulse rate and blood oxygen saturation. The signal quality, which is indicative of the accuracy and reliability of the measured physiological parameter, is calculated by combining a plurality of signal quality indicators, each of which is an indicator of a quality of the measured signal. The value of the signal quality metric is compared to a threshold and based on this comparison various decisions are made by the medical device. One decision is directed towards deciding whether or not to display the measured physiological parameter, to ensure that only accurate measured values are displayed. Another decision is directed towards providing feedback to guide the clinician to adjust the location of the sensor to a more suitable tissue location.

Claims

1. A method for evaluating a signal, comprising:

obtaining a signal quality metric based on a measured physiological parameter;

comparing the signal quality metric to a first threshold;

comparing the signal quality metric to second threshold if the processed signal quality metric is less than the first threshold; and

providing an indication of poor signal quality if the signal quality metric is less than the first threshold and the second threshold.

2. The method, as set forth by claim 1, comprising obtaining the signal quality metric from one or more signal quality indicators acquired with the measured physiological parameter.

3. The method, as set forth by claim 2, wherein the signal quality indicators comprise a similarity overlap between a first and a second electromagnetic signal, wherein the first and second electromagnetic signals differ in frequency.

4. The method, as set forth by claim 2, wherein the signal quality indicators comprise a measure based on a shape of an arterial pulse.

5. The method, as set forth by claim 2, wherein the signal quality indicators comprise a frequency content of a pulse waveform relative to pulse rate.

6. The method, as set forth by claim 1, comprising processing the signal quality metric using one or more of proportional (P), integral (I), or derivative (D) control operations.

7. The method, as set forth by claim 1, wherein the measured physiological parameter comprises pulse oximetry measurements.

8. The method, as set forth by claim 1, comprising remeasuring the physiological parameter if the signal quality metric is less than the first threshold and greater than the second threshold.

9. The method, as set forth by claim 1, wherein the indication comprises a text message indicating the poor signal quality.

10. The method, as set forth by claim 1, wherein the indication comprises an alarm indicating the poor signal quality.

11. A method for evaluating a physiological measurement, comprising the acts of:

obtaining a signal quality metric based on a physiological parameter acquired by a physiological sensor; and

directing an operator to reposition the physiological sensor if the signal quality metric is below a threshold value.

12. The method, as set forth by claim 11, wherein the sensor is a pulse oximetry sensor.

13. The method, as set forth by claim 11, comprising comparing the signal quality metric to the threshold value after the signal quality metric is processed by one or more of proportional (P), integral (I), or derivative (D) control operations.

14. The method, as set forth by claim 11, wherein directing the operator comprises providing one or more of a visual, audible, or temporal indication of signal quality.

15. The method, as set forth by claim 11, wherein the signal quality metric corresponds to dislocations of the sensor.

17. The tangible machine readable medium, as set forth by claim 11 comprising code configured to obtain the signal quality metric from one or more signal quality indicators acquired with the measured physiological parameter.

18. The tangible machine readable medium, as set forth by claim 17, comprising code configured to obtaining a measure based on the shape of an arterial pulse as one of the signal quality indicators.

19. The tangible machine readable medium, as set forth by claim 17, comprising code configured to obtain a frequency content of a pulse waveform relative to pulse rate as one of the signal quality indicators.

20. The tangible machine readable medium, as set forth by claim 17, comprising code configured to process the signal quality metric using one or more of proportional (P), integral (I), or derivative (D) control operations.

22. The tangible machine readable medium, as set forth by claim 17, comprising code configured to compare the signal quality metric to the threshold value after the signal quality metric is processed by one or more of proportional (P), integral (I), or derivative (D) control operations.

23. The tangible machine readable medium, as set forth by claim 17, comprising code configured to provide one or more of a visual, audible, or temporal indication of signal quality.

16. A tangible machine readable medium configured to evaluate a signal, comprising:

code configured to obtain a signal quality metric based on a measured physiological parameter;

code configured to compare the signal quality metric to a first threshold;

code configured to compare the signal quality metric to a second threshold if the processed signal quality metric is less than the first threshold; and

code configured to provide an indication of poor signal quality if the signal quality metric is less than the first threshold and the second threshold.

21. A tangible machine readable medium configured to evaluate a physiological measurement, comprising:

code configured to obtain a signal quality metric based on a physiological parameter acquired by a physiological sensor; and

code configured to direct an operator to reposition the physiological sensor if the signal quality metric is below a threshold value.

24. A system for evaluating a signal comprising:

a sensor adapted to acquire a physiological parameter;

a signal processor adapted to obtain a signal quality metric based on the physiological parameter, to compare the signal quality metric to a first threshold, and to compare the signal quality metric to a second threshold if the processed signal quality metric is less than the first threshold; and

a device adapted to provide an indication of poor signal quality if the signal quality metric is less than the first threshold and the second threshold.

25. The system, as set forth by claim 24, wherein the sensor is a pulse oximetry sensor.

26. The system, as set forth by claim 24, wherein the signal processor is adapted to execute one or more of proportional (P), integral (I), or derivative (D) control operations.

27. The system, as set forth by claim 24, wherein the device is a monitor.

28. The system, as set forth by claim 24, wherein the device is an audible device.

29. A system for evaluating a physiological measurement, comprising:

a sensor adapted to acquire a physiological parameter;

a signal processor adapted to obtain a signal quality metric based on a physiological parameter and to compare the signal quality metric to a threshold value; and

an interface device configured to direct an operator to reposition the sensor if the signal quality metric is below the threshold value.

30. The system, as set forth by claim 29, wherein the physiological parameter is derived from pulse oximetry.

31. The system, as set forth by claim 29, wherein the processor is adapted to obtain the signal quality metric from signal quality indicators.

32. The system, as set forth by claim 29, wherein the interface device comprises at least one of a display or a speaker.

33. A method for evaluating a signal comprising:

obtaining signal quality indicators associated with the measurement of a physiological parameter; and

obtaining a signal quality metric associated with the signal quality indicators by non-neural network processes.