Detection of sensor off conditions in a pulse oximeter
First Claim
1. A method for use in detecting and responding to a sensor off condition in a pulse oximetry system, said pulse oximetry system including a first source for providing a first channel signal associated with a first wavelength and a second source for providing a second channel signal associated with a second wavelength, said method comprising the steps of:
- obtaining first and second detector signals associated with said first and second wavelengths, respectively;
monitoring said first and second detector signals over time period including a first time window and a second time window;
first determining a first correlation value relating to a first correlation between said first and second signals for said first time window;
second determining a second correlation value relating to a second correlation between said first and second signals for said second time window;
performing a comparison between said first and said second correlation values;
based on said comparison, determining a change value related to a change in said first correlation value relative to said second correlation value; and
identifying a sensor off condition based on said change value.
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Accused Products
Abstract
A system for detecting sensor off conditions in a pulse oximeter is disclosed. In one implementation, a detector off condition is identified based a volatility of a signal quality of a filtered detector signal. The detector signal is first filtered, for example, to reduce the effects of noise or to otherwise reduce or eliminate components extraneous to the signal of interest. The filtered signal is used to perform a volatility measurement. In this regard, a correlation coefficient may be computed relative to two channels of the filtered signal and a correlation coefficient may be monitored over a moving window to calculate variance values for the correlation coefficient. The resulting variance values may be used alone or in combination with other parameter values to identify a sensor off condition.
802 Citations
27 Claims
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1. A method for use in detecting and responding to a sensor off condition in a pulse oximetry system, said pulse oximetry system including a first source for providing a first channel signal associated with a first wavelength and a second source for providing a second channel signal associated with a second wavelength, said method comprising the steps of:
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obtaining first and second detector signals associated with said first and second wavelengths, respectively;
monitoring said first and second detector signals over time period including a first time window and a second time window;
first determining a first correlation value relating to a first correlation between said first and second signals for said first time window;
second determining a second correlation value relating to a second correlation between said first and second signals for said second time window;
performing a comparison between said first and said second correlation values;
based on said comparison, determining a change value related to a change in said first correlation value relative to said second correlation value; and
identifying a sensor off condition based on said change value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for use in detecting and responding to a sensor off conditions in a pulse oximetry system, said pulse oximetry system including a first source for providing a first channel signal associated with a first wavelength and a second source for providing a second channel signal associated with a second wavelength, comprising the steps of:
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defining a measure of signal quality for a detected signal based on a comparative analysis of said first and second channel signals;
monitoring said measure of signal quality over a moving time window of a predetermined temporal length;
first calculating a reference value for said measure of signal quality for said moving time window;
second calculating a value related to variance of said measure of signal quality relative to said reference value; and
identifying a sensor off condition based on said value related to variance. - View Dependent Claims (10, 11, 12, 13, 14)
comparison of data points from at least one of said first and second channels with said reference value associated with said moving time window; and
statistical comparison of at least one correlation value to said reference value associated with said moving time window.
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15. A method for use in detecting and responding to a sensor off conditions in a pulse oximetry system, said pulse oximetry system including a detector for receiving light signals modulated by tissue of a patient, said method comprising the steps of:
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obtaining first and second signals associated with first and second wavelengths of said light signals, respectively, from said detector;
filtering each said first and second signals to obtain a series of corresponding filtered values for each said wavelength, wherein filtering comprises performing a weighted average of at least a portion of each said signal over a moving time window associated with each said filtered value;
utilizing said corresponding filtered values for said first and second signals to determine a correlation value relating to a correlation between said first and second signals; and
using said correlation value to identify a sensor off condition. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A method for use in detecting and responding to a sensor off conditions in a pulse oximetry system, said method comprising the steps of:
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defining a measure of correlation between first and second channels for a detected signal;
monitoring said measure of correlation between said first and second channels over a time window of a predetermined length;
determining a first value related to a magnitude of at least one of said first and second channels for said detected signal relative to said time window;
determining a second value related to a variance of said measure of correlation between said first and second channels relative to a normalized correlation value for said time window; and
using said first value and said second value to identify a sensor off condition. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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Specification