Time-segmented pulse oximetry and pulse oximeter performing the same

• US 20070049812A1
• Filed: 08/29/2006
• Published: 03/01/2007
• Est. Priority Date: 08/30/2005
• Status: Active Grant

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: Kobayashi, Naoki, Fuse, Masayoshi, Aoyagi, Takuo
• Granted Patent: US 8,024,021 B2
• Time in Patent Office: Days
• US Class Current: 600/336
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts

Abstract

In order to measure an oxygen saturation in blood of a subject, a living tissue of the subject is irradiated with a first light beam having a first wavelength and a second light beam having a second wavelength different from the first wavelength. A first electrical signal is generated from the first light beam reflected from or transmitted through the living tissue. A second electrical signal is generated from the second light beam reflected from or transmitted through the living tissue. The first electrical signal is divided into a plurality of first segments each of which includes a part of the first electrical signal for a predetermined time period. The second electrical signal is divided into a plurality of second segments each of which includes a part of the second electrical signal for the predetermined time period. It is calculated a gradient of a regression line between every one of the first segments and an associated one of the second segments, thereby obtaining a plurality of gradients.

Claims

1. A method of measuring an oxygen saturation in blood of a subject, comprising:

irradiating a living tissue of the subject with a first light beam having a first wavelength and a second light beam having a second wavelength different from the first wavelength;

generating a first electrical signal from the first light beam reflected from or transmitted through the living tissue;

generating a second electrical signal from the second light beam reflected from or transmitted through the living tissue;

dividing the first electrical signal into a plurality of first segments each of which includes a part of the first electrical signal for a predetermined time period;

dividing the second electrical signal into a plurality of second segments each of which includes a part of the second electrical signal for the predetermined time period; and

calculating a gradient of a regression line between every one of the first segments and an associated one of the second segments, thereby obtaining a plurality of gradients.

2. The method as set forth in claim 1, further comprising:

calculating an arterial oxygen saturation from every one of the gradients, thereby obtaining a plurality of arterial oxygen saturations;

smoothing the arterial oxygen saturations to obtain a smoothed arterial oxygen saturation; and

calculating an oxygen saturation in blood based on the smoothed arterial oxygen saturation.

3. The method as set forth in claim 1, further comprising:

smoothing the gradients to obtain a smoothed gradient;

calculating an arterial oxygen saturation from the smoothed gradient; and

calculating an oxygen saturation in blood based on the arterial oxygen saturation.

4. A pulse oximeter operable to measure an oxygen saturation in blood of a subject, comprising:

a light emitter, adapted to irradiate a living tissue of the subject with a first light beam having a first wavelength and a second light beam having a second wavelength different from the first wavelength;

a signal generator, operable to generate a first electrical signal from the first light beam reflected from or transmitted through the living tissue, and operable to generate a second electrical signal from the second light beam reflected from or transmitted through the living tissue;

a processor, operable to;

divide the first electrical signal into a plurality of first segments each of which includes a part of the first electrical signal for a predetermined time period;

divide the second electrical signal into a plurality of second segments each of which includes a part of the second electrical signal for the predetermined time period; and

calculate a gradient of a regression line between every one of the first segments and an associated one of the second segments, thereby obtaining a plurality of gradients.

5. The pulse oximeter as set forth in claim 4, wherein:

the processor is operable to;

calculate an arterial oxygen saturation from every one of the gradients, thereby obtaining a plurality of arterial oxygen saturations;

smooth the arterial oxygen saturations to obtain a smoothed arterial oxygen saturation; and

calculate an oxygen saturation in blood based on the smoothed arterial oxygen saturation.

6. The pulse oximeter as set forth in claim 4, wherein:

the processor is operable to;

smooth the gradients to obtain a smoothed gradient;

calculate an arterial oxygen saturation from the smoothed gradient; and

calculate an oxygen saturation in blood based on the arterial oxygen saturation.