Apparatus and method for measuring oxygen saturation in blood and apparatus and method for measuring concentration of light-absorbing materials in blood

• US 5,690,104 A
• Filed: 06/10/1996
• Issued: 11/25/1997
• Est. Priority Date: 06/02/1994
• Status: Expired due to Term

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: Kobayashi, Naoki, Aoyagi, Takuo, Kanemoto, Michio
• Primary Examiner(s): Bahr, Jennifer
• Assistant Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US08/661,169
• Time in Patent Office: 533 Days
• Field of Search: 128/633, 128/664, 128/665, 128/666, 356/39, 356/41
• US Class Current: 600/323
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips

Abstract

Intensities of light of two different wavelengths transmitted through a tissue of a living body are measured during a first time period. A data processor determines a first regression line using logarithmically processed data corresponding to the light intensities measured during the first time period. An operator injects a dye into the living body and measurements of intensities of light at the two different wavelengths are made during a later time period. The data processor determines a second regression line using logarithmically processed data corresponding to the light intensities measured during the later time period. The data processor finds an intersection of the two regression lines and uses the intersection to determine a bloodless level point. The processor then forms a dye dilution curve incorporating the bloodless level point data.

Claims

1. An apparatus for measuring the concentration of light-absorbing materials in blood comprising:

light generating means for projecting light beams of two different wavelengths to a living body;

photo sensing means for receiving light beams transmitted through the living body and for converting received light beams into electrical signals;

regression line computing means for forming at least two regression lines for at least two periods, using values, at a plurality of time points, of said electrical signals output from said photo sensing means, wherein coordinates of points on said at least two regression lines refer to an ordinate and an abscissa which represent the magnitudes of said electrical signals;

bloodless level computing means for computing a bloodless level of said received light beams using intersections of extensions of said at least two regression lines;

absorbance calculating means for computing a blood absorbance of said received light beams of different wavelengths by using said bloodless level computed by said bloodless level computing means and said electrical signals; and

concentration computing means for computing the concentration of light absorbing materials in blood using said absorbance computed by said absorbance calculating means.

2. The apparatus as claimed in claim 1, wherein said bloodless level computing means is arranged to successively detect intersections of said at least two regression lines, one of said at least two regression lines being obtained during a period before dye injection, and the other of said at least two regression lines being obtained during period after dye injection, and when a dispersion of said intersections is determined to be within a predetermined range, said bloodless level computing means determines that a center of the distribution of said intersections represents a bloodless level.

3. A method for measuring the concentration of light-absorbing materials in blood comprising the steps of:

projecting light beams of two different wavelengths to a living body;

receiving light beams transmitted through the living body and converting received light beams into electrical signals;

forming at least two regression lines for at least two periods, using values, at a plurality of time points, of said electrical signals output from a photo sensing means, where coordinates of points on said at least two regression lines include a value of an ordinate and an abscissa representing the magnitudes of said electrical signals;

calculating a bloodless level of said received light beams using intersections of extensions of said at least two regression lines obtained by a regression line computing means;

calculating a blood absorbance of said received light beams of different wavelengths by using said bloodless level computed by a bloodless level computing means and said electrical signals output from said photo sensing means; and

computing the concentration of light absorbing materials in blood using said blood absorbance.

4. The method as claimed in claim 3, wherein said step of calculating said bloodless level includes the steps of:

successively obtaining intersections of said at least two regression lines, one of said at least two regression lines being obtained during a period before dye injection, and the other of said at least two regression lines being obtained during period after dye injection; and

determining the center of the distribution of intersections as representing a bloodless level when a dispersion of the intersections lies within a predetermined range.