Patent ID: 7072701

Claim:
A method for non-invasively determining a blood oxygen saturation level within a subject's tissue using a near infrared spectrophotometric sensor, said method comprising the steps of: transmitting a light signal into the subject's tissue using the sensor, wherein the transmitted light signal includes a first wavelength, a second wavelength, and a third wavelength; sensing a first intensity and a second intensity of the light signal, using the sensor, along the first, second, and third wavelengths after the light signal travels through the subject at a first predetermined distance and a second predetermined distance; wherein the sensor is calibrated using empirical data that relates to the subject's tissue that is sensed by the sensor to account for light signal attenuation resulting from light signal scattering within the subject's tissue; determining an attenuation of the light signal for each of the first, second, and third wavelengths using the sensed first intensity and sensed second intensity of the first, second, and third wavelengths; determining a difference in attenuation of the light signal between the first wavelength and the second wavelength, and between the first wavelength and the third wavelength; determining the blood oxygen saturation level within the subject's tissue using the difference in attenuation between the first wavelength and the second wavelength, and the difference in attenuation between the first wavelength and the third wavelength.