Signal processing apparatus

• US 7,530,955 B2
• Filed: 05/04/2004
• Issued: 05/12/2009
• Est. Priority Date: 03/07/1991
• Status: Expired due to Fees

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Elfadel, Ibrahim M., Weber, Walter M., Diab, Mohamed K., Kiani-Azarbayjany, Esmaiel, Smith, Robert A., McCarthy, Rex J.
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US10/838,814
• Publication Number:
  US 20040210146A1
• Time in Patent Office: 1,834 Days
• Field of Search: 600/310, 600/322, 600/323, 600/330, 600/336, 600/502, 600/324
• US Class Current: 600/502
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02154 by optical transmission
• 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 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• 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 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/4821 Determining level or depth of anaesthesia A61B5/1106 takes precedence
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• 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
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7253 characterised by using transforms
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61B 6/00 : Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment instruments measuring radiation intensity for application in the field of nuclear medicine, e.g. in vivo counting, G01T1/161; apparatus for taking X-ray photographs G03B42/02
• CPC Class Codes: A61B 8/00 : Diagnosis using ultrasonic, sonic or infrasonic waves imaging of objects using sonar G01S15/00
• CPC Class Codes: A61B 8/5276 : due to motion
• CPC Class Codes: G01N 2021/3144 : for oxymetry
• CPC Class Codes: G06F 2218/04 : Denoising
• CPC Class Codes: H04B 1/123 : using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H

Abstract

The present invention involves method and apparatus for analyzing measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients in order to find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.

Claims

1. A method of determining pulse rate comprising:

receiving first and second intensity signals from a light-sensitive detector which detects light of at least first and second wavelengths attenuated by body tissue carrying pulsing blood;

electronically determining using one or more signal processing devices of a patient monitor, at least two values corresponding to pulse rate based upon at least two different methods of processing the physiological signals; and

electronically determining using one or more signal processing devices of a patient monitor, a resulting value for pulse rate from the at least two values corresponding to pulse rate, wherein one of the different methods of processing comprises a self optimizing algorithm.

2. The method of claim 1, wherein the self optimizing algorithm comprises a least squares algorithm.

3. The method of claim 1, comprising outputting a measurement of pulse rate indicative of said resulting value of said pulse rate.

4. The method of claim 3, wherein said outputting comprises outputting to a display device said measurement of said pulse rate.

5. A method of determining pulse rate comprising:

sensing physiological signals resulting from the attenuation of light of at least first and second wavelengths by body tissue carrying pulsing blood;

electronically determining using one or more signal processing devices of a patient monitor, at least two values corresponding to pulse rate based upon at least two alternative methods of processing the sensed physiological signals from at least one of the first and second wavelengths; and

electronically determining using one or more signal processing devices of a patient monitor, a resulting value for pulse rate from the at least two values corresponding to pulse rate, wherein the step of determining comprises selecting at least one of the at least two values based on a determination of confidence in the accuracy of physiological signals.

6. The method of claim 5, comprising outputting a measurement of pulse rate indicative of said resulting value of said pulse rate.

7. The method of claim 6, wherein said outputting comprises outputting to a display device said measurement of said pulse rate.

8. A method of determining pulse rate comprising:

sensing physiological signals resulting from the attenuation of light of at least first and second wavelengths by body tissue carrying pulsing blood;

electronically determining using one or more signal processing devices of a patient monitor, at least two values corresponding to pulse rate based upon at least two alternative methods of processing the sensed physiological signals from at least one of the first and second wavelengths; and

electronically determining using one or more signal processing devices of a patient monitor, a resulting value for pulse rate from the at least two values corresponding to pulse rate, wherein determining a resulting value comprises averaging the at least two values and wherein said step of averaging comprises averaging over a time window, wherein said window is increased for potential of said physiological parameter having a lower confidence of accuracy and decreased for potential values of said physiological parameter having a higher confidence of accuracy.

9. The method of claim 8, comprising outputting a measurement of pulse rate indicative of said resulting value of said pulse rate.

10. The method of claim 9, wherein said outputting comprises outputting to a display device said measurement of said pulse rate.