Patent ID: 6711425
Filing Date: 2004-03-23
Classification: A61B

Abstract:
A method for determining oxygen saturation in a pulse oximeter having a calibration stabilization process for reducing a deviation in calibration comprising the following steps:exposing a tissue site to a plurality of wavelengths of light generated by the pulse oximeter; defining a tissue site characteristic, other than oxygen saturation, which may influence the determination of oxygen saturation; defining a ratio wavelength set as a first subset of the plurality of wavelengths for calculation of an oxygen saturation value; defining a correction wavelength set as a second subset of the plurality of wavelengths for detection and correction of a deviation in the calibration of the oxygen saturation calculation over a specified range of oxygen saturation, due to a perturbation of the tissue site characteristic, and including selecting the correction wavelength set to optimize the correction of the deviations; detecting light of the plurality of wavelengths transmitted by or reflected from components of the tissue site and converting the detected light into a plurality of electrical signals; digitizing and conditioning the plurality of electrical signals in a signal data acquisition component of the pulse oximeter to yield a plurality of input signals; defining a set of correction function(s) operating upon the plurality of input signals and substantially removing deviations from the input signals corresponding to the ratio wavelength set; calculating a plurality of normalized pulse amplitudes from the plurality of input signals in a processing component of the pulse oximeter; detecting the deviation in input signals corresponding to the correction wavelength set, and if the deviation is present calculating a calibration deviation correction by applying the set of correction function(s) to the input signals corresponding to the correction wavelength set, and; calculating an oxygen saturation value from a ratio of normalized pulse amplitudes corresponding to the ratio wavelength set, and utilizing the calibration deviation correction.