US 6,262,798 B1 · 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 blood without hemolysis or dilution. To overcome the complex optical properties of whole 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 (including an optical cuvette) all optical parameters, such as sample thickness, detector size and shape, sample-to-detector distance, wavelengths, monochromicity, and maximum angle of light capture by detector, are optimal values so as to minimize the contribution of light scattering to the total optical attenuation of unaltered whole blood and so as to maximize the contribution of true optical absorbance. After making measurements of a blood sample's optical density at each of the wavelengths, the invention makes corrections for the effects of light scattering by red blood cells, for light scattering produced by other causes, and (if necessary) for the effects of the finite bandwidth of the substantially monochromatic light.

Claims44

Dependent claims

A method of determining the concentrations of a plurality of constituent components of unaltered whole blood of unknown composition, 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 of unknown composition with said plurality of radiation wavelengths, through a depth of said sample chosen to minimize radiation scattering by unaltered whole 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 concentrations of said constituent components;
and
calculating concentrations of said plurality of constituent components of said sample of unaltered whole blood corrected for the effects of radiation scattering, 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 plurality of radiation wavelengths.

2 more elements

A method of determining the concentrations of a plurality of k constituent components of unaltered whole blood, k being an integer, comprising:

generating a plurality of n different substantially monochromatic radiation wavelengths, where n is an integer and n>k, k of said n wavelengths having been selected to measure radiation absorption by said k constituent components, and n-k of said n wavelengths having been selected to compensate for errors due to n-k scattering factors in unaltered whole blood;
irradiating a sample of unaltered whole blood with said n radiation wavelengths;
detecting intensities of said n radiation wavelengths after passing through said sample of unaltered whole blood;
and
calculating concentrations of said k constituent components of said sample of unaltered whole blood, corrected for the effects of radiation scattering, as a function of said detected intensities of said n radiation wavelengths.

2 more elements

Dependencies are inferred from the claim text.

Method and apparatus for direct spectrophotometric measurements in unaltered whole blood

Life of this patent

Method and apparatus for direct spectrophotometric measurements in unaltered whole blood

Life of this patent

Abstract

Claims44