Patent ID: 6615064
Filing Date: 2003-09-02
Classification: A61B

Abstract:
A non-invasive method for measuring the concentration of a blood component in a subject's blood, said method comprising the steps of:a. providing at least one light source for directing light of at least two wavelengths through a tissue of the subject in which light absorbances by arterial blood can be detected by measuring changes in absorbance during pulsatile flow of blood; b. providing at least one detector for detecting the portion of the light transmitted through the tissue of the subject; c. providing at least one detector for detecting a physical dimension of the tissue of the subject near or at the location of the at least one light source; d. measuring the absorbance of the light at the first wavelength by the tissue at both the systolic and diastolic phases of the pulsatile flow; e. measuring the absorbance of the light at the second wavelength by the tissue at both the systolic and diastolic phases of the pulsatile flow; f. determining the rate of change over time of absorbance of light of the first wavelength during pulsatile flow; g. determining the rate of change over time of absorbance of light of the second wavelength during pulsatile flow; h. determining the rate of change over time in physical dimension during pulsatile flow at or near the location of the at least one light source; i. calculating a ratio of the rate of change in light absorbance over time divided by the rate of change over time in physical dimension for the first wave length; j. calculating a ratio of the rate of change in light absorbance over time divided by the rate of change over time in physical dimension for the second wave length; k. calculating the concentration of the blood component in said subject's blood by comparing the results of a formula employing the ratios determined in step i and j as independent variables to the results of the same formula in subjects with known blood component levels.