Method and apparatus for direct spectrophotometric measurements in unaltered whole blood

Abstract

A method and apparatus that allows accurate spectrophotometric determination of the concentrations of various hemoglobin species in whole undiluted blood. The invention employs 1) an optical apparatus designed to maximize the true optical absorbance of whole blood and to minimize the effects of light scattering on the spectrophotometric measurements of the concentrations of various constituent components, and 2) methods to correct the hemoglobin concentration measurements for light scattering and for the effects of the finite bandwidth of the substantially monochromatic light. In the optical apparatus optical parameters, such as sample thickness, detector size, sample-to-detector distance, wavelengths, monochromicity, and maximum angle of light capture by detector, are selected so as to minimize the contribution of light scattering and to maximize the contribution of true optical absorbance. After making measurements of a blood sample's optical density at each of the wavelengths, corrections are made for the effects of light scattering.

1 . A method of determining the concentrations of a plurality of constituent components of unaltered whole blood, including: 
 generating a plurality of substantially monochromatic radiation wavelengths, each wavelength of an absorbance subset of said plurality of wavelengths having been selected by their ability to distinguish the constituent components and having been selected to minimize the effects of radiation scattering and to maximize radiation absorbance by said constituent components, and each wavelength of a scattering subset of said plurality of wavelengths having been selected to maximize the effects of radiation scattering by unaltered whole blood relative to the effects of radiation absorbance by unaltered whole blood;    irradiating a sample of unaltered whole blood with said plurality of radiation wavelengths, through a depth of said sample chosen to minimize radiation scattering by unaltered whole undiluted blood;    detecting intensities of said radiation wavelengths, after passing through said depth of said sample, at a distance from said sample, and over a detecting area, both chosen to minimize the effects of radiation scattering by unaltered whole blood on the determination of concentration of said constituent components; and    calculating concentrations of said plurality of constituent components of said sample of unaltered whole blood, based upon detected intensities of each of said plurality of radiation wavelengths, and based upon predetermined molar extinction coefficients for each of said constituent components at each of said radiation wavelengths of said absorbance subset.    
   
   
       2 - 33 . (canceled)