Variable indication estimator

• US 20060161389A1
• Filed: 03/14/2006
• Published: 07/20/2006
• Est. Priority Date: 06/05/2000
• Status: Active Grant

• Current Assignee: Ammar Al-Ali, Lorenzo Cazzoll, Walter M. Weber
• Original Assignee: Ammar Al-Ali, Lorenzo Cazzoll, Walter M. Weber
• Inventors: Weber, Walter M., Al-Ali, Ammar, Cazzoll, Lorenzo
• Granted Patent: US 7,499,835 B2
• Time in Patent Office: Days
• US Class Current: 702/182
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6829 Foot or ankle
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: A61B 5/72 Signal processing specially adapted for physiological signals or for diagnostic purposes character recognition, recognising digital ink, document-oriented image-based pattern recognition G06V30/00; recognition or understanding of postal images G06V30/424
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7271 Specific aspects of physiological measurement analysis A61B5/316, A61B5/349 and A61B5/374 take precedence
• CPC Class Codes: G06F 2218/04 Denoising

Abstract

A variable indication estimator which determines an output value representative of a set of input data. For example, the estimator can reduce input data to estimates of a desired signal, select a time, and determine an output value from the estimates and the time. In one embodiment, the time is selected using one or more adjustable signal confidence parameters determine where along the estimates the output value will be computed. By varying the parameters, the characteristics of the output value are variable. For example, when input signal confidence is low, the parameters are adjusted so that the output value is a smoothed representation of the input signal. When input signal confidence is high, the parameters are adjusted so that the output value has a faster and more accurate response to the input signal.

Claims

1. A signal processor which determines an output value for a set of input values, the signal processor comprising:

a buffer which stores a window of input values from a signal representative of one or more signals attenuated after emission into tissue at a measurement site;

a signal confidence indicator;

a memory storing an estimator; and

a processor which receives the signal confidence indicator and which accesses the buffer to receive the input values, wherein the processor is configured to execute the estimator using the input values to reduce the input values to a plurality of estimates, and is configured to determine an output value for the window of input values from the plurality of estimates based on a selected time associated with the signal confidence indicator.

2. The signal processor of claim 1, wherein the processor is also configured to segment the window of input values and wherein the plurality of estimates include segment estimates, where each segment estimate is derived from the input values corresponding to a respective segment.

3. The signal processor of claim 2, wherein the output value corresponds to an interpolation between the one or more segment estimates.

4. The signal processor of claim 1, wherein the estimator comprises one of a smoother, a filter, a forward predictor, and a backward predictor.

5. The signal processor of claim 1, wherein the estimator comprises a variable mode averager.

6. The signal processor of claim 5, wherein the variable mode averager uses the signal confidence indicator as a mode input.

7. The signal processor of claim 1, wherein the signal confidence indicator corresponds to a level of confidence that one or more of the input values represent a value of a desired signal.

8. The signal processor of claim 1, wherein the signal confidence indicator is adjustable based on a characteristic associated with the input values.

9. The signal processor of claim 8, wherein the output value approximates a smoother when the signal confidence indicator is low.

10. The signal processor of claim 8, wherein the output value approximates a filter when the signal confidence indicator is high.

11. The signal processor of claim 8, wherein the output value includes a faster response to the input values when the signal confidence indicator is high.

12. The signal processor of claim 8, wherein the output value includes a more accurate response to the input values when the signal confidence indicator is high.

13. The signal processor of claim 1, wherein the processor is configured to activate an alarm when the output value is below a threshold value, and wherein the processor lowers an amount of false alarms through adjustment of the signal confidence indicator.

14. The signal processor of claim 1, wherein the processor is configured to activate an alarm when the output value is below a threshold value, and wherein the output value more accurately reflects an extent of an event within the window of input values through adjustment of the signal confidence indicator.

15. The signal processor of claim 1, wherein the signal includes a desired signal portion representing a physiological parameter and can include other signal artifacts.

16. A method of generating an output value representative of a desired signal from a set of input values, the method comprising:

accessing a set of input values of a signal, wherein the signal includes a desired signal representing a physiological parameter and may include other signal artifacts;

accessing a measure of signal confidence;

estimating values of the desired signal from the input values; and

determining an output value based on the estimated values and on a time associated with the measure of signal confidence.

17. The method of claim 16, wherein the measurement of signal confidence is based on whether the most recent input values represent values of the desired signal.

18. The method of claim 16, wherein the generating an estimate comprises segmenting the set of input values into segments and generating the one or more estimates from each segment.

19. The method of claim 18, wherein the determining the output value further includes interpolating between the estimates from each segment.

20. The method of claim 16, further comprising:

activating an alarm when the output value is below a threshold value; and

reducing an amount of false alarms through adjustment of the measurement of signal confidence.

21. The method of claim 16, further comprising:

activating an alarm when the output value is below a threshold value; and

more accurately reflecting an extent of an event within the desired signal through adjustment of the measurement of signal confidence.

22. The method of claim 16, wherein the generating an estimate comprises applying one of a smoother, a filter, a forward predictor, and a backward predictor to the input values.

23. A method of generating an alarm corresponding to a physiological condition of a patient dropping below a threshold level, the method comprising:

determining a curve fit for a set of data points, wherein the data points correspond to a signal representative of a physiological condition of a patient;

selecting a point on the curve fit based on a confidence value; and

generating an alarm condition when a value corresponding to the selected point is outside a range of acceptable values.

24. A method of determining an output value for a set of input data, the method comprising:

reducing input data to estimates of a desired signal;

selecting a time using a characteristic of the input data; and

determining an output value based on the time and the estimates.

25. The method of claim 24, wherein the characteristic of the input data comprises a confidence that the input data represents the desired signal.