US 6,104,938 A · Procedure, apparatus and detector for the determination of fractional oxygen saturation

Abstract

The invention relates to a procedure for determining the relative concentration or composition of different kinds of haemoglobin, such as oxyhaemoglobin, deoxyhaemoglobin and dyshaemoglobins, and/or dye components contained in blood in a non-invasive manner using the light absorption caused by different haemoglobin varieties and/or dye components, in which procedure light signals are transmitted at at least two predetermined wavelengths to a tissue comprised in the patient's blood circulation, the light signal transmitted through the target under measurement and/or reflected from it is received and the proportion of the intensity of the pulsating light signal received at each wavelength is determined in relation to the total intensity of the light transmitted through the tissue or reflected from the tissue. In the procedure, the effective extinction coefficients of blood haemoglobin derivatives and/or dye components in the tissue are determined for each light signal and/or light signal pair via a mathematical transformation from blood dye component extinction coefficients consistent with the Lambert-Beer theory and the proportion of specific blood haemoglobin derivatives and/or dye components in relation to the total amount of haemoglobin contained in the blood is determined by means of the intensity of the signals received in different wavelength ranges.

Claims50

Dependent claims

A method for non-invasively determining the amount of a light absorbing substance in the blood of a subject, the blood having at least two light absorbing substances, said method comprising the steps of:

(A) applying light of a first wavelength to tissue of the subject containing blood to obtain a first transmitted light quantity, the first transmitted light quantity having a pulsatile component and a non-pulsatile component;
(B) applying light of a second wavelength to tissue of the subject containing blood to obtain a second transmitted light quantity, the second transmitted light quantity having a pulsatile component and a non-pulsatile component;
(C) ratioing the pulsatile component of the first transmitted light quantity to the total first transmitted light quantity and ratioing the pulsatile component of the second light quantity to the total second transmitted light quantity to obtain first and second percentage modulation quantities (% mod 1, 2 . . . );
(D) ratioing the first and second percentage modulation quantities (% mod 1, 2 . . . ) to obtain a modulation ratio quantity (Z');
(E) formulating substance concentration determining equations (Eq 8, 9) for wavelengths corresponding to the first and second light wavelengths;
(F) altering one of a modulation ratio term (Z', Z) or extinction coefficient terms (.epsilon.', .epsilon.) in the equations in accordance with the percentage modulation quantities to account for the application of the light of the first and second wavelengths to the tissue as well as the blood of the subject;
(G) solving the equations for at least one selected substance present in the blood;
and
(H) determining, from the solution of the equations, the amount of the selected substance in the blood.

6 more elements

Dependencies are inferred from the claim text.

Procedure, apparatus and detector for the determination of fractional oxygen saturation

Life of this patent

Procedure, apparatus and detector for the determination of fractional oxygen saturation

Life of this patent

Abstract

Claims50