Patent ID: 6944488

Claim:
A method for accurately estimating a saturation metric for a metabolite of interest in a volume of fluid by an optical sensor measurement substantially independent of the presence of encapsulating tissue over all or a portion of a lens of the optical sensor, comprising: determining a tissue overgrowth correction factor (K) for a first and a second wavelength of optical radiation in a dual wavelength optical sensor, wherein said first wavelength of optical radiation is substantially proportional to an amount of a metabolite of interest present in a volume of fluid and said second wavelength of radiation is substantially independent to the amount of the metabolite present in the volume of fluid; determining a nominal time interval for detecting the second wavelength of optical radiation (T 2 ) after it is directed to a volume of fluid containing a material having known optical properties; determining a pair of calibration constants (A,B) for said first and said second wavelength of optical radiation; placing the dual wavelength optical sensor in a volume of fluid may contain an amount of the metabolite; measuring a first time interval for the first wavelength of radiation and a second time interval for the second wavelength of radiation when said first and second wavelengths of radiation are directed to the volume of fluid; and calculating a saturation metric for the metabolite of interest based upon the tissue overgrowth correction factor (K), the pair of calibration constants (A,B), the nominal time interval, the first time interval and the second time interval.