A
pulse oximetry method and
system for improved
motion correction is disclosed. The method /
system provides for the use of a
detector output
signal to obtain a different plurality of
differential absorption data sets in corresponding relation to each of a succession of measurement, wherein each of the data sets includes
differential absorption values for light of a first
wavelength and light of a second
wavelength. The data sets are processed to obtain a
relative motion estimate value for each measurement. When the
relative motion estimate value for a given measurement falls within a predetermined range (i.e., corresponding with clinical motion), a corresponding blood
analyte indicator value is adjusted in a predetermined manner, wherein the corresponding adjusted blood
analyte indicator is employable to obtain at least one blood
analyte concentration value. In one embodiment, blood analyte indicator values may be readily multiplied by a predetermined adjustment factor (i.e., when clinical motion is identified). The
relative motion estimate value for a given measurement may be obtained by conducting a
principal component analysis of the corresponding plurality of data sets relative to a corresponding best fit function therefor to obtain corresponding variance values V1, V2. The variance value V1, and / or V2 for a given current measurement may be employed to obtain a current
motion estimate value. The current
motion estimate value and the relative
motion estimate value obtained for a prior low
motion measurement (i.e., for which no adjustment was necessary) may be used to compute the relative motion estimate value for the current measurement. The variance values V1 and / or V2 are also employable to compute an ongoing, updated motion probability factor, wherein such factor may be used to adjust relative motion estimates values in instances of rapid tissue
perfusion changes.