Patent ID: 6662031
Filing Date: 2003-12-09
Classification: A61B,G01N

Abstract:
A method for the non-invasive determination of hemoglobin concentration and hematocrit value in human tissue, said method comprising the steps of:(a) setting the temperature of an area of skin of a body part to a first temperature, said first temperature being below the core temperature of the body, (b) performing an optical measurement in which at least one light introduction site on the surface of said skin is illuminated by a light beam at a plurality of wavelengths and the light re-emitted from the underlying dermal layers is collected at at least one light collection site, the at least one light introduction site and the at least one light collection site being separated by at least one sampling distance, the at least one sampling distance between said at least one light introduction site and said at least one collection site being selected to restrict the sampling depth of said body part to within the epidermis layer and dermis layer only, whereby contributions from light re-emitted from adipose tissue and muscle tissue are minimized and contributions from light re-emitted from the epidermis and dermis layers are collected, said temperature being maintained at a constant value during said optical measurement, (c) setting the temperature of said area of said skin of said body part to at least a second temperature that is within the physiological temperature range, (d) repeating step (b) at said at least second temperature, (e) determining a plurality of optical parameters at each temperature and determining the dependence of at least one of said aforementioned optical parameters on temperature, (f) establishing a calibration relationship that relates (1) at least one of said plurality of optical parameters at a given temperature and (2) the dependence of at least one of said plurality of optical parameters on temperature with the concentration of hemoglobin or the hematocrit value measured independently, and (g) determining the concentration of hemoglobin or the hematocrit value by means of a subsequent determination of the plurality of optical parameters at a given temperature and the dependence of the at least one of said aforementioned optical parameters on temperature and the calibration relationship established in step (f), wherein said biological sample comprises intake human tissue.