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Abstract

Non-invasive in-vivo and in-vitro methods for determining a person's total hemoglobin concentration as well as the concentration of the hemoglobin species which contribute to this total concentration, i.e., oxy-, deoxy-, carboxy-, and methemoglobin are described. The measurement comprises a ratio formed by dividing absorbance data at analyte wavelengths by absorbance data at reference wavelengths. In a first embodiment the analyte wavelengths occur at a local maximum of each of the hemoglobin species in the visible region. The reference wavelengths include those in the short wavelength near-infrared region from 800 to 1300 nm. In order to determine the concentration of each hemoglobin species a dA/A treatment is utilized comprising a difference term of absorbance data in the region from 800 to 1300 nm divided by the absorbance at a local maximum for each species. These measurements at local maxima are then combined in a series of simultaneous equations which are then solved for the concentration of each species and the total concentration. In a second embodiment, analyte wavelengths are selected in the range of 480 nm to 630 nm, with separate analyte wavelengths for each hemoglobin species. The measurements are then combined in a series of simultaneous equations which are then solved for the concentration of each species and the total concentration of hemoglobin. In addition, a measurement for total hemoglobin concentration which uses a ratio of absorbance at a triple isosbestic point and the above described difference term is described.

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First Claim