Patent ID: 7512431

Claim:
A method for accurately estimating an oxygen saturation metric for a volume of blood by an optical sensor measurement, comprising: deploying a dual wavelength optical sensor into fluid communication with a volume of blood, wherein said volume of blood is characterized by a blood flow rate condition, said flow rate condition comprising one of: relatively low, stasis, substantially stagnant; determining a tissue overgrowth correction factor (K) for a first and a second wavelength of optical radiation in the dual wavelength optical sensor, wherein said first wavelength of optical radiation is substantially proportional to an amount of saturated oxygen present in said volume of blood and said second wavelength of radiation is substantially independent of the amount of saturated oxygen present in the volume of blood; determining a nominal time interval for detecting the second wavelength of optical radiation (T2) after it is directed to a volume of blood having known optical properties; determining a pair of calibration constants (A,B) for said first and said second wavelength of optical radiation; 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 blood; and calculating a saturation metric for the saturated oxygen 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.