Variable indication estimator

• US 7,499,835 B2
• Filed: 03/14/2006
• Issued: 03/03/2009
• Est. Priority Date: 06/05/2000
• Status: Expired due to Fees

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Cazzoll, Lorenzo, Weber, Walter M., Al-Ali, Ammar
• Primary Examiner(s): TSAI, CAROL S W
• Application Number:
  US11/375,662
• Publication Number:
  US 20060161389A1
• Time in Patent Office: 1,085 Days
• Field of Search: 702/182, 702/185, 702/119, 702/189, 702/190, 600/300, 600/310, 600322-326, 600/330, 600/336, 340/511, 340/521, 340/573.1, 340/573, 700/14, 700/79
• US Class Current: 702/185
• 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 oxygen saturation (SpO₂) value for a set of input SpO₂ values, the signal processor comprising:

a buffer which stores a window of input SpO₂ values determined using a signal representative of one or more signals attenuated after emission into tissue at a measurement site;

a signal confidence indicator;

and

a processor which receives the signal confidence indicator and which accesses the buffer to receive the input SpO₂ values, wherein the processor is configured to determine output SpO₂ values for the window of input SpO₂ values by adjusting the output SpO₂ values between smoothing characteristics and tracking characteristics, the tracking characteristics indicating a trend of the input SpO₂ values, wherein the adjustment is based on the signal confidence indicator.

2. The signal processor of claim 1, wherein the processor is also configured to segment the window of input SpO₂ values and wherein the output SpO₂ values include segment SpO₂ values, where each segment SpO₂ value is derived from the input SpO₂ values corresponding to a respective segment.

3. The signal processor of claim 2, wherein the output SpO₂ values correspond to an interpolation between the one or more segment SpO₂ values.

4. The signal processor of claim 1, wherein the signal confidence indicator operates as a mode input.

5. The signal processor of claim 1, wherein the signal confidence indicator corresponds to a level of confidence that one or more of the input SpO₂ values represent a value of a desired signal.

6. The signal processor of claim 1, wherein the signal confidence indicator is adjustable based on a characteristic associated with the input SpO₂ values.

7. The signal processor of claim 6, wherein the output SpO₂ value approximates a smoother when the signal confidence indicator is low.

8. The signal processor of claim 6, wherein the output SpO₂ value approximates a tracker when the signal confidence indicator is high.

9. The signal processor of claim 6, wherein the output SpO₂ value includes a faster response to the input SpO₂ values when the signal confidence indicator is high.

10. The signal processor of claim 6, wherein the output SpO₂ value includes a more accurate response to the input SpO₂ values when the signal confidence indicator is high.

11. The signal processor of claim 1, wherein the processor is configured to activate an alarm when the output SpO₂ value is below a threshold value, and wherein the processor lowers an amount of false alarms through adjustment of the signal confidence indicator.

12. The signal processor of claim 1, wherein the processor is configured to activate an alarm when the output SpO₂ value is below a threshold value, and wherein the output SpO₂ values more accurately reflect an extent of an event within the window of input SpO₂ values through adjustment of the signal confidence indicator.

13. The signal processor of claim 1, wherein the signal includes a desired signal portion indicative of SpO₂ and can include other signal artifacts.

14. A method of generating an output oxygen saturation (SpO₂) value representative of a desired signal from a set of input (SpO₂) values, the method comprising:

accessing a set of input (SpO₂) values of a signal, wherein the signal includes a desired signal indicative of an accurate SpO₂ and may include other signal artifacts;

accessing a measure of signal confidence;

and determining an output (SpO₂) values adjusting the output SpO₂ values between smoothing characteristics and tracking characteristics, the tracking characteristics indicating atrend of the input SpO₂ values, wherein adjusting is based on the measure of signal confidence.

15. The method of claim 14, wherein the measurement of signal confidence is based on whether the most recent input (SpO₂) values represent values of the desired signal.

16. The method of claim 14, wherein the determining the output SpO₂ values comprises segmenting the set of input (SpO₂) values into segments and generating estimates from each segment.

17. The method of claim 16, wherein the determining the output (SpO₂) value further includes interpolating between the estimates from each segment.

18. The method of claim 14, further comprising:

activating an alarm when the output (SpO₂) value is below a threshold value;

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

19. The method of claim 14, further comprising:

activating an alarm when the output (SpO₂) values are below a threshold value;

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