Two stage calibration and analyte measurement scheme for spectrophotomeric analysis

A method for determining regression coefficients for a photoplethysmographic analyte measurement system, comprising:

• first collecting noninvasive photoplethysmographic data from a plurality of test subjects using a predetermined number of light emitters, each said light emitter providing a distinct spectral content of light;
• second collecting invasive concentration measurements for each of a plurality of blood analytes from each of the test subjects;
• determining a first set of regression coefficients, wherein said first set:
• (A) has regression coefficients for each analyte of a first collection of said plurality of analytes, said first collection including at least a first analyte;
• and
• (B) is determined using at least one of:
• (a) said noninvasive photoplethysmographic data, and (b) at least some of said invasive concentration measurements;
• determining a second set of regression coefficients, said second set having regression coefficients for each analyte of a second collection of said remaining analytes not in said first collection, wherein (a) said second set is determined using at least a subcollection of said noninvasive photoplethysmographic data, and (b) said subcollection satisfies a predetermined constraint related to a concentration measurement of said first analyte obtained in said second collecting step;
• and
• determining a third set of regression coefficients, said third set having regression coefficients for each analyte of said second collection using substantially all of said noninvasive photoplethysmographic data.

A method for photoplethysmographic determination of analyte concentrations in a tissue comprising:

• directing a plurality of beams of light through the tissue wherein each beam of light is characterized by a distinct spectral content;
• measuring the light transmitted through the tissue;
• estimating concentrations for at least one analyte in a first collection of a plurality of analytes using said light measurements;
• comparing said estimated concentrations for the at least one analyte in said first collection with a predetermined criteria for said estimated initial concentrations;
• if said estimated concentrations of said first collection of analytes satisfies said criteria then estimating a concentration for each of the remaining analytes not in said first collection of analytes using said light measurements and said estimated concentrations of said first collection of analytes as a substantially accurate estimate of the actual analyte concentration.