Signal processing for pulse oximetry
First Claim
1. A method of processing a pulse oximetry input signal, the method comprising the steps of:
- comparing the input signal at each of a plurality of different time shifts to each member of a set of functions, wherein the set includes functions with a plurality of different frequencies between 30 to 240 cycles per minute;
selecting, based on results obtained in the comparing step, a function from the set that best matches the input signal;
identifying a rising portion of the input signal based on an alignment in time with a rising portion of the selected function; and
calculating an oxygen saturation level based on one or more samples taken from the portion of the input signal that was identified in the identifying step.
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Abstract
A signal processing technique for estimating the frequency of a pulsatile signal (including but not limited to pulse oximetry signals) is disclosed. Each of the functions contained within a pre-selected set of functions is compared to the input signal at many different time-shifts, and the function/time-shift combination that best matches the input signal is selected. The frequency of the best-matching function is then used as the best estimate of the frequency of the input signal. Optionally, once a function has been selected, the rising portion of the selected function can be correlated in time to the rising portion of the input signal. Improved results can then be obtained by basing the oxygen saturation level calculations on samples taken from the rising portion of the input signal.
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Citations
13 Claims
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1. A method of processing a pulse oximetry input signal, the method comprising the steps of:
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comparing the input signal at each of a plurality of different time shifts to each member of a set of functions, wherein the set includes functions with a plurality of different frequencies between 30 to 240 cycles per minute; selecting, based on results obtained in the comparing step, a function from the set that best matches the input signal; identifying a rising portion of the input signal based on an alignment in time with a rising portion of the selected function; and calculating an oxygen saturation level based on one or more samples taken from the portion of the input signal that was identified in the identifying step. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification