Signal processing apparatus

• US 7,469,157 B2
• Filed: 02/13/2004
• Issued: 12/23/2008
• Est. Priority Date: 03/07/1991
• Status: Expired due to Fees

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Weber, Walter M., Diab, Mohamed K., Kiani-Azarbayjany, Esmaiel
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US10/779,033
• Publication Number:
  US 20040236196A1
• Time in Patent Office: 1,775 Days
• Field of Search: 600/310, 600/322, 600/323, 600/330, 600/336
• US Class Current: 600/336
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• 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 5/726 using Wavelet transforms
• 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

A signal processor which acquires a first signal, including a first primary signal portion and a first secondary signal portion, and a second signal, including a second primary signal portion and a second secondary signal portion, wherein the first and second primary signal portions are correlated. The signals may be acquired by propagating energy through a medium and measuring an attenuated signal after transmission or reflection. Alternatively, the signals may be acquired by measuring energy generated by the medium. A processor of the present invention generates a primary or secondary reference signal which is a combination, respectively, of only the primary or secondary signal portions. The secondary reference signal is then used to remove the secondary portion of each of the first and second measured signals via a correlation canceler, such as an adaptive noise canceler, preferably of the joint process estimator type. The primary reference signal is used to remove the primary portion of each of the first and second measured signals via a correlation canceler. The processor of the present invention may be employed in conjunction with a correlation canceler in physiological monitors wherein the known properties of energy attenuation through a medium are used to determine physiological characteristics of the medium. Many physiological conditions, such as the pulse, or blood pressure of a patient or the concentration of a constituent in a medium, can be determined from the primary or secondary portions of the signal after other signal portion is removed.

Claims

1. An apparatus for computing arterial signals in living tissue, said apparatus comprising:

a detector configured to receive a first signal which travels along a first propagation path and a second signal which travels along a second propagation path, at least a portion of said first and second propagation paths being located in a propagation medium, wherein said first signal has an arterial signal portion that is indicative of arterial blood and another signal portion that is indicative of motion induced noise, and said second signal has an arterial signal portion that is indicative of arterial blood and another signal portion that is indicative of motion induced noise, said detector also configured to output a detector signal responsive to said first and second signals; and

a signal processor responsive to representations of the detector signal and configured to generate therefrom a signal which is primarily a function of said arterial portions of said first and said second signals without significant interference from said motion induced noise.

2. The apparatus recited in claim 1, wherein the other signal portion of each of said first and second signals includes an indication of human respiration.

3. A method of determining blood oxygen saturation, the method comprising:

receiving in a patient monitor a plurality of intensity signals representative of light of at least three wavelengths attenuated by body tissue carrying pulsing blood wherein the signals include a portion that is indicative of motion induced noise;

processing with a processor of the patient monitor ratiometric data related to the plurality of intensity signals to significantly reduce an effect of motion induced noise in the at least one of the plurality of intensity signals; and

,

determining with the processor a value of oxygen saturation from the at least one of the plurality of intensity signals with the effect of motion induced noise significantly reduced.

4. The method of claim 3, wherein at least two of the at least three wavelengths corresponds to substantially red light.

5. The method of claim 3, wherein at least one of the at least three wavelengths corresponds to substantially infrared light.