Patent ID: 7848891

Claim:
A method of detecting a blood characteristic in a patient, comprising: identifying a plurality of first modulating signal values with a processor based on detecting a first modulating signal at a first wavelength with a detector over a time period; identifying a plurality of second modulating signal values with the processor based on detecting a second modulating signal at a second wavelength with the detector over the time period; and determining a relative amplitude of the first and second modulating signal values with the processor comprising: weighting the first and second modulating signal values with non-zero weighting factors such that more weighting is given to values identified later in the time period and less weighting is given to values identified earlier in the time period; and regressing the first and second modulating signal values relative to one another, wherein a first uncertainty value in the first modulating signal and a second uncertainty value in the second modulating signal are accommodated and the non-zero weighting factors are incorporated.