Signal processing apparatus

• US 20060089549A1
• Filed: 12/03/2004
• Published: 04/27/2006
• Est. Priority Date: 03/07/1991
• Status: Active Grant

• Current Assignee: Esmaiel Kiani-Azarbayjany, Ibrahim M. Elfadel, Mohamed K. Diab, Rex J. Mccarthy, Robert A. Smith, Walter M. Weber
• Original Assignee: Esmaiel Kiani-Azarbayjany, Ibrahim M. Elfadel, Mohamed K. Diab, Rex J. Mccarthy, Robert A. Smith, Walter M. Weber
• Inventors: Elfadel, Ibrahim M., Weber, Walter M., Diab, Mohamed K., Kiani-Azarbayjany, Esmaiel, Smith, Robert A., McCarthy, Rex J.
• Granted Patent: US 7,383,070 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• 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 a method and an apparatus for analyzing measured signals, including the determination of a measurement of correlation in the measured signals during a calculation of a physiological parameter of a monitored patient. Use of this invention is described in particular detail with respect to blood oximetry measurements.

Claims

1. A method for use in a system comprising a sensor for acquiring photo-plethysmographic data of a patient and a signal processing system for removing a plurality of motion artifacts from said photo-plethysmographic data and for obtaining a measure of at least one physiological parameter from said photo-plethysmographic data, the method comprising:

acquiring said photo-plethysmographic data;

transforming said photo-plethysmographic data;

analyzing said transformed photo-plethysmographic data to locate candidate spectral peaks;

reconstructing a clean photo-plethysmographic signal; and

determining said measure of said at least one physiological parameter.

2. The method of claim 1, wherein the clean photo-plethysmographic signal is substantially free of effects of the plurality of motion artifacts.

3. The method of claim 1, wherein the at least one physiological parameter comprises blood oxygen saturation.

4. The method of claim 1, wherein the at least one physiological parameter comprises pulse rate.

5. The method of claim 4, wherein the determining said measure is based on at least the clean photo-plethysmographic signal.

6. A pulse oximetry system for the determination of a physiological parameter capable of removing motion artifacts from physiological signals, the pulse oximetry system comprising a hardware subsystem and a software subsystem,

wherein said hardware subsystem comprises:

an optical sensor unit for providing said pulse oximetry system with a patient'"'"'s photo-plethysmographic data, wherein said sensor comprises a light emitting diode for emitting light, a photo-detector for detecting said light, wherein said detected light contains information on the photo-plethysmographic data,

a processor for processing the photo-plethysmographic data, and

a memory unit, wherein said memory unit is operably coupled to said processor, and

wherein the software subsystem performs a method comprising the steps of;

acquiring said photo-plethysmographic data from the sensor;

conditioning said photo-plethysmographic data for signal processing;

transforming the conditioned data into a frequency domain;

analyzing the frequency domain data to locate candidate spectral peaks;

reconstructing a clean photo-plethysmographic signal; and

determining said physiological parameter.

7. The pulse oximetry system of claim 6, wherein the clean photo-plethysmographic signal is substantially free of effects of motion artifacts.

8. The pulse oximetry system of claim 6, wherein the physiological parameter comprises blood oxygen saturation.

9. The pulse oximetry system of claim 6, wherein the physiological parameter comprises pulse rate.

10. The pulse oximetry system of claim 9, wherein the determining said physiological parameter is based on at least the clean photo-plethysmographic signal.