SIGNAL PROCESSING APPARATUS

• US 20120165631A1
• Filed: 02/22/2012
• Published: 06/28/2012
• Est. Priority Date: 10/07/1994
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Kiani-Azarbayjany, Esmaiel, Elfadel, Ibrahim M., McCarthy, Rex J., Smith, Robert A., Diab, Mohamed K., Weber, Walter M.
• Granted Patent: US 8,755,856 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• 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 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• 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 5/7214 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 5/7246 using correlation, e.g. template matching or determination of similarity
• 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: 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 disclosure describes a method and an apparatus for analyzing measured signals using various processing techniques. In certain embodiments, the measured signals are physiological signals. In certain embodiments, the measurements relate to blood constituent measurements including blood oxygen saturation.

Claims

1. In a signal processor, a method of determining a measurement of a characteristic of arterial blood, the method comprising:

transforming first and second time-domain signals into respective first and second frequency-domain signals, the first and second time-domain signals being indicative of light that has been attenuated by body tissue carrying arterial blood;

determining one or more values for a plurality of non-zero frequency components of the first and second frequency-domain signals that are indicative of the strength of one or more frequency components of the first frequency-domain signal versus the strength of one or more corresponding frequency components in the second frequency-domain signal;

selecting one or more frequency components that exhibit physiological characteristics of arterial blood using, at least in part, the corresponding one or more values; and

determining the measurement for the characteristic of arterial blood using the selected one or more frequency components.

2. The method of claim 1, wherein the characteristic of arterial blood comprises the oxygen saturation thereof.

3. The method of claim 2, wherein selecting one or more frequency components that exhibit physiological characteristics of arterial blood comprises calculating a plurality of possible oxygen saturation values.

4. The method of claim 3, wherein selecting one or more frequency components that exhibit physiological characteristics of arterial blood further comprises analyzing a histogram of the plurality of possible oxygen saturation values.

5. The method of claim 1, wherein the plurality of non-zero frequency components span a range of frequencies that includes one or more harmonics of the pulse rate of the pulsing blood.

6. The method of claim 1, wherein each value comprises a ratio of the strength of one or more frequency components in the first frequency-domain signal to the strength of the corresponding one or more frequency components in the second frequency-domain signal.

7. The method of claim 6, wherein the first and second frequency-domain signals respectively comprise first and second Fourier-transformed signals.

8. The method of claim 7, wherein the strength of the one or more frequency components in the first and second Fourier-transformed signals respectively comprises the magnitude of the first and second Fourier-transformed transform signals for the one or more frequency components.

9. A signal processor apparatus for determining a measurement value for a characteristic of arterial blood, the signal processor apparatus comprising:

a processor programmed to perform a method comprising,

transforming first and second time-domain signals into respective first and second frequency-domain signals, the first and second time-domain signals being indicative of light that has been attenuated by body tissue carrying arterial blood;

determining one or more values for a plurality of non-zero frequency components of the first and second frequency-domain signals that are indicative of the strength of one or more frequency components of the first frequency-domain signal versus the strength of one or more corresponding frequency components in the second frequency-domain signal;

selecting one or more frequency components that exhibit physiological characteristics of arterial blood using, at least in part, the corresponding one or more values; and

determining the measurement for the characteristic of arterial blood using the selected one or more frequency components.

10. The signal processor apparatus of claim 9, wherein the characteristic of arterial blood comprises the oxygen saturation thereof.

11. The signal processor apparatus of claim 10, wherein selecting one or more frequency components that exhibit physiological characteristics of arterial blood comprises calculating a plurality of possible oxygen saturation values.

12. The signal processor apparatus of claim 11, wherein selecting one or more frequency components that exhibit physiological characteristics of arterial blood further comprises analyzing a histogram of the plurality of possible oxygen saturation values.

13. The signal processor apparatus of claim 9, wherein the plurality of non-zero frequency components span a range of frequencies that includes one or more harmonics of the pulse rate of the pulsing blood.

14. The signal processor apparatus of claim 9, wherein each value comprises a ratio of the strength of one or more frequency components in the first frequency-domain signal to the strength of the corresponding one or more frequency components in the second frequency-domain signal.

15. The signal processor apparatus of claim 14, wherein the first and second frequency-domain signals respectively comprise first and second Fourier-transformed signals.

16. The signal processor apparatus of claim 15, wherein the strength of the one or more frequency components in the first and second Fourier-transformed signals respectively comprises the magnitude of the first and second Fourier-transformed transform signals for the one or more frequency components.