Method and apparatus for identifying the presence of noise in a time division multiplexed oximeter
First Claim
1. A pulse oximetry system using time division multiplexing, said system comprising:
- means for transmitting light of a first wavelength through an appendage of a test subject to create a first transmitted light signal;
means for transmitting light of a second wavelength through said appendage to create a second transmitted light signal, wherein said second wavelength is different from said first wavelength;
means for creating a multiplexed signal using said first transmitted light signal and said second transmitted light signal;
first signal processing means for processing said multiplexed signal to determine an oxygen saturation value for said test subject'"'"'s arterial blood, said first signal processing means having a predetermined passband;
means for displaying said oxygen saturation value to an operator;
means for determining whether an AC noise component in said multiplexed signal has corrupted said oxygen saturation value determined by said first signal processing means; and
,means for notifying said operator when said oxygen saturation value is corrupted.
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Accused Products
Abstract
Noise content in the output signal of a system using time division multiplexing (TDM) is measured to determine whether the output signal represents a reliable measurement. A "dark" channel in a TDM input signal may be used to isolate noise which is present in the input signal from desired informational content in the signal. The noise is processed to determine if any component of the noise will be "imaged" into the passband of the system. Any such components are then processed in a manner approximating the system transfer function to produce a noise signal indicative of the noise content of the system output signal. In one embodiment of the invention, the noise signal is used to remove noise from the output signal of the system.
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Citations
27 Claims
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1. A pulse oximetry system using time division multiplexing, said system comprising:
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means for transmitting light of a first wavelength through an appendage of a test subject to create a first transmitted light signal; means for transmitting light of a second wavelength through said appendage to create a second transmitted light signal, wherein said second wavelength is different from said first wavelength; means for creating a multiplexed signal using said first transmitted light signal and said second transmitted light signal; first signal processing means for processing said multiplexed signal to determine an oxygen saturation value for said test subject'"'"'s arterial blood, said first signal processing means having a predetermined passband; means for displaying said oxygen saturation value to an operator; means for determining whether an AC noise component in said multiplexed signal has corrupted said oxygen saturation value determined by said first signal processing means; and
,means for notifying said operator when said oxygen saturation value is corrupted. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A self-diagnostic pulse oximetry system, comprising:
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means for receiving a time division multiplexed (TDM) input signal, said TDM input signal having a first portion carrying both information and noise and a second portion carrying only noise; means for processing said first portion according to a first transfer function to create a first output signal indicative of the oxygen saturation of a test subject'"'"'s arterial blood; means for displaying said first output signal to a system operator; means for processing said second portion according to a second transfer function which approximates said first transfer function to create a second output signal indicative of the noise content of said first output signal; means for determining whether said first output signal has been corrupted by noise, based on said second output signal; and means for notifying said system operator when said first output signal has been corrupted by noise. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. In a time division multiplexed oximetry system for non-invasively determining a percentage of oxygen saturation in a test subject'"'"'s blood, a method for determining whether an output signal has been corrupted by noise, said method comprising the steps of:
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providing a system having a predetermined transfer function; providing a multiplexed input signal to said system, said input signal having a plurality of separate time slots including a first time slot carrying a first signal having an information portion and a noise portion and a second time slot carrying a second signal having only a noise portion; processing said first signal in said system according to said predetermined transfer function to produce a first output signal; providing signal processing means for approximating said predetermined transfer function; processing said second signal using said signal processing means to produce a second output signal; determining whether said first output signal has been corrupted by noise based on said second output signal; and notifying a system operator when said first output signal has been corrupted by noise. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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Specification