Pulse oximeter

• US 20050049469A1
• Filed: 08/27/2004
• Published: 03/03/2005
• Est. Priority Date: 08/27/2003
• Status: Active Grant

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: Kobayashi, Naoki, Fuse, Masayoshi, Aoyagi, Takuo, Ukawa, Teiji
• Granted Patent: US 7,206,621 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14551 for measuring blood gases

Abstract

In a pulse oximeter for obtaining an oxygen saturation in a blood, a light emitter irradiates a living tissue with light beams having five different wavelengths. A light receiver receives respective light beams reflected from or transmitted through the living tissue, and converts the received light beams to electric signals. A first calculator calculates five attenuation changes of the living tissue based on fluctuations of the respective electric signals. A second calculator calculates at least four attenuation change ratios from the five attenuation changes. Each of the attenuation change ratios is defined by a ratio between any two of the five attenuation changes. A third calculator calculates the oxygen saturation based on the attenuation change ratios, while taking an oxygen saturation of arterial blood, an oxygen saturation of venous blood, a ratio between changes in arterial blood and venous blood, and a tissue term as four unknown values.

Claims

1. A pulse oximeter for obtaining an oxygen saturation in a blood, comprising:

a light emitter, adapted to irradiate a living tissue with light beams having five different wavelengths;

a light receiver, adapted to receive respective light beams reflected from or transmitted through the living tissue, and to convert the received light beams to electric signals;

a first calculator, which calculates five attenuation changes of the living tissue based on fluctuations of the respective electric signals;

a second calculator, which calculates at least four attenuation change ratios from the five attenuation changes, each of the attenuation change ratios being defined by a ratio between any two of the five attenuation changes; and

a third calculator, which calculates the oxygen saturation based on the attenuation change ratios, while taking an oxygen saturation of arterial blood, an oxygen saturation of venous blood, a ratio between changes in arterial blood and venous blood, and a tissue term as four unknown values.

2. A method of obtaining an oxygen saturation in a blood, comprising steps of:

irradiating a living tissue with light beams having five different wavelengths;

receiving respective light beams reflected from or transmitted through the living tissue;

converting the received light beams to electric signals;

calculating five attenuation changes of the living tissue based on fluctuations of the respective electric signals;

calculating at least four attenuation change ratios from the five attenuation changes, each of the attenuation change ratios being defined by a ratio between any two of the five attenuation changes; and

calculating the oxygen saturation based on the attenuation change ratios, while taking an oxygen saturation of arterial blood, an oxygen saturation of venous blood, a ratio between changes in arterial blood and venous blood, and a tissue term as four unknown values.