Patent ID: 6714805
Filing Date: 2004-03-30
Classification: A61B

Abstract:
A method for noninvasively monitoring hemoglobin concentration and oxygen saturation comprising:(a) selecting at least two wavelengths from a region of wavelengths in which an extinction coefficient for water is smaller than an extinction coefficient for hemoglobin, the at least two wavelengths including at least two isobestic wavelengths; (b) sequentially radiating incident light beams having the selected wavelengths onto a predetermined site of a body that includes a blood vessel, wherein the predetermined site includes the blood vessel whose thickness varies with pulses no greater than a predetermined value; (c) receiving, at another site of the body, light beams sequentially transmitted through the predetermined site and converting the received light beams into electrical signals; (d) calculating the light attenuation variation caused by pulses of blood for the respective wavelengths from the electrical signals; (e) obtaining at least one ratio of the light attenuation variation between the selected wavelengths; and (f) calculating the hemoglobin concentration CHb in blood using the calculated at least one ratio of the light attenuation variation between the wavelengths.