Apparatus for determining concentrations of light absorbing substances in blood

• US 7,313,426 B2
• Filed: 03/28/2005
• Issued: 12/25/2007
• Est. Priority Date: 03/29/2004
• Status: Active Grant

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: Kubota, Hiroshi, Kobayashi, Naoki, Takeda, Sunao
• Primary Examiner(s): Winakur; Eric
• Assistant Examiner(s): Berhanu; Etsub D
• Application Number:
  US11/090,239
• Publication Number:
  US 20050250997A1
• Time in Patent Office: 1,002 Days
• Field of Search: 600/300, 600/310, 600/322, 600/323
• US Class Current: 600/322
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14551 for measuring blood gases

Abstract

In an apparatus for determining a concentration of a light absorbing substance in blood, a plurality of photo emitters are adapted to emit light beams having different wavelengths toward a living tissue including a blood vessel. A photo receiver is adapted to receive the light beams which have been transmitted through or reflected from the living tissue. A driver inputs driving currents for causing the respective photo emitters to emit the light beams. An optimizer obtains values of AC components of the light beams received by the photo receiver, and adjusts values of the driving currents such that the values of the AC components fall within a predetermined range.

Claims

1. An apparatus for determining a concentration of a light absorbing substance in blood, comprising:

a plurality of photo emitters, adapted to emit light beams having different wavelengths toward a living tissue including a blood vessel;

a photo receiver, adapted to receive the light beams which have been transmitted through or reflected from the living tissue;

a driver, which inputs driving currents for causing the respective photo emitters to emit the light beams; and

an optimizer, which obtains values of AC components of the light beams received by the photo receiver, and adjusts values of the driving currents such that the values of the AC components fall within a predetermined range.

2. The apparatus as set forth in claim 1, wherein the optimizer comprises:

a first calculator, which further obtains values of DC components of the light beans received by the photo receiver, and calculates values of pulsation ratios which are ratios of the values of the AC components to the values of the DC components;

a second calculator, which calculates, based on the values of the DC components and the values of the pulsation ratios, optimized current values corresponding to minimum expected values of the AC components which are inherent in the apparatus; and

a controller, which causes the values of the driving currents to coincide with the optimized current values.