Signal processing apparatus

• US 7,254,433 B2
• Filed: 09/30/2003
• Issued: 08/07/2007
• 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:
  US10/676,534
• Publication Number:
  US 20040064020A1
• Time in Patent Office: 1,407 Days
• Field of Search: 600/310, 600/322, 600/323, 600/330, 600/336, 600/502
• US Class Current: 600/336
• 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 of reducing an effect of unwanted signal portions from one or more signals usable to determine a physiological characteristic of pulsing blood, the method 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, wherein the first and second intensity signals each include wanted and unwanted signal portions;

shaping at least some of the unwanted signal portions in the first and second intensity signals away from wanted frequencies;

removing at least some of the shaped unwanted signal portions from the shaped first and second intensity signals; and

calculating a physiological characteristic of the pulsing blood from remaining portions of at least one of shaped first and second intensity signals.

2. The method of claim 1, wherein the shaping is performed with a noise shaping converter which shifts the unwanted signal portions.

3. The method of claim 2, wherein the noise shaping converter comprises a delta sigma converter.

4. The method of claim 3, wherein the delta sigma converter comprises a single channel converter.

5. The method of claim 3, wherein the delta sigma converter comprises a dual channel converter.

6. The method of claim 1, wherein the physiological characteristic comprises oxygen saturation of the pulsing blood.

7. The method of claim 1, wherein the physiological characteristic comprises a pulse rate of the pulsing blood.

8. The method of claim 1, determining a plethysmographic waveform representative of the physiological characteristic.

9. The method of claim 1, wherein the shaping comprises shifting the at least some of the unwanted signal portions to higher frequencies.

10. A physiological monitor which uses a noise shaping converter to remove unwanted portions of signals usable to determine one or more physiological characteristics, the physiological monitor comprising:

at least one conductive element capable of 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, wherein the first and second intensity signals each include wanted and unwanted signal portions;

a noise shaping converter which shapes at least some of the unwanted signal portions away from wanted frequencies;

means for removing from the first or second intensity signals at least some of the shaped unwanted signal portions; and

means for calculating a physiological characteristic of the pulsing blood from remaining portions of at least one of shaped first and second intensity signals.

11. The method of claim 10, wherein the noise shaping converter comprises a delta sigma converter.

12. The method of claim 11, wherein the delta sigma converter comprises a single channel converter.

13. The method of claim 11, wherein the delta sigma converter comprises a dual channel converter.

14. The method of claim 10, wherein the physiological characteristic comprises oxygen saturation of the pulsing blood.

15. The method of claim 10, wherein the physiological characteristic comprises a pulse rate of the pulsing blood.

16. The method of claim 10, comprising means for determining a plethysmographic waveform representative of the physiological characteristic.

17. The method of claim 10, wherein the noise shaping converter shapes the unwanted signal portions by shifting the at least some of the unwanted signal portions to higher frequencies.

18. A method of processing physiological signals in a pulse oximeter, the method 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;

processing the intensity signals with a delta-sigma converter; and

calculating a physiological characteristic of the pulsing blood from the processed first and second intensity signals.

19. The method of claim 18, wherein the intensity signals each include wanted and unwanted signal portions, and wherein the processing reduces an influence of the unwanted signal portions.

20. The method of claim 19, wherein the delta signal converter shifts the unwanted signal portions.

21. The method of claim 19, wherein the unwanted signal portions comprise motion induces noise.

22. The method of claim 19, wherein the delta signal converter shapes at least some of the unwanted signal portions by shifting the at least some of the unwanted signal portions to higher frequencies.

23. The method of claim 18, wherein the delta sigma converter comprises a single channel converter.

24. The method of claim 18, wherein the delta sigma converter comprises a dual channel converter.

25. The method of claim 18, wherein the physiological characteristic comprises oxygen saturation of the pulsing blood.

26. The method of claim 18, wherein the physiological characteristic comprises a pulse rate of the pulsing blood.

27. The method of claim 18, comprising determining a plethysmographic waveform representative of the physiological characteristic.