Apparatus and method for measuring transit time of oxygen in blood

• US 20060173258A1
• Filed: 01/30/2006
• Published: 08/03/2006
• Est. Priority Date: 01/28/2005
• Status: Active Grant

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: Kubota, Hiroshi, Kobayashi, Naoki
• Granted Patent: US 7,376,452 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/14551 for measuring blood gases

Abstract

In order to measure a transit time of oxygen in blood, at least one sensor is attached to at least one prescribed position on a subject. The sensor is adapted to detect a light absorption of arterial blood at the prescribed position. An oxygen saturation of the arterial blood at the prescribed position is calculated based on the detected light absorption. An amount of oxygen inspired into the subject is varied at a reference time point. A change in the calculated oxygen saturation at the prescribed position is detected. A time period from the reference time point to a time point at which the oxygen saturation changes is measured.

Claims

1. A method for measuring a transit time of oxygen in blood, comprising:

attaching at least one sensor to at least one prescribed position on a subject, the sensor being adapted to detect a light absorption of arterial blood at the prescribed position;

calculating an oxygen saturation of the arterial blood at the prescribed position, based on the detected light absorption;

varying an amount of oxygen inspired into the subject at a reference time point;

detecting a change in the calculated oxygen saturation at the prescribed position; and

measuring a time period from the reference time point to a time point at which the oxygen saturation changes.

2. The measuring method as set forth in claim 1, wherein the inspired amount of oxygen is varied by causing the subject to perform at least one of a deep breathing and a breath hold.

3. The measuring method as set forth in claim 1, wherein the inspired amount of oxygen is varied by varying a concentration of oxygen to be inspired.

4. The measuring method as set forth in claim 1, wherein the oxygen saturation is obtained by a pulse oximeter.

5. The measuring method as set forth in claim 1, wherein:

a plurality of sensors are attached to a plurality of prescribed positions on the subject;

each of the sensors is adapted to detect the light absorption at each of the prescribed positions;

the oxygen saturation is calculated at each of the prescribed positions, based on the light absorption detected by each of the sensors;

the change in the calculated oxygen saturation is detected at each of the prescribed positions; and

the time period is measured for each of the prescribed positions.

6. The measuring method as set forth in claim 5, further comprising determining a difference between time periods measured at prescribed positions.

7. The measuring method as set forth in claim 6, further comprising:

obtaining a cross-correlation coefficient between attenuation rates or oxygen saturations measured by the sensors; and

determining the difference based on a time period from the reference time point to a time point at which the cross-correlation coefficient becomes maximum.

8. An apparatus for measuring a transit time of oxygen in blood, comprising:

at least one sensor, adapted to be attached to at least one prescribed position on a subject, the sensor being operable to detect a light absorption of arterial blood at the prescribed position;

a first calculator, adapted to calculate an oxygen saturation of the arterial blood at the prescribed position, based on the detected light absorption;

a first detector, adapted to detect a first time point at which an amount of oxygen inspired into the subject is varied; and

a second detector, adapted to detect a second time point at which the calculated oxygen saturation changes to determine a time period from the first time point to the second time point.

9. The measuring apparatus as set forth in claim 8, wherein the first detector is a flow sensor adapted to detect that the inspired amount of oxygen is varied.

10. The measuring apparatus as set forth in claim 8, further comprising a valve operable to vary a concentration of oxygen to be inspired.

11. The measuring apparatus as set forth in claim 8, wherein the oxygen saturation is obtained by a pulse oximeter.

12. The measuring apparatus as set forth in claim 8, wherein:

a plurality of sensors are attached to a plurality of prescribed positions on the subject;

each of the sensors is adapted to detect the light absorption at each of the prescribed positions;

the oxygen saturation is calculated at each of the prescribed positions, based on the light absorption detected by each of the sensors;

the change In the calculated oxygen saturation is detected at each of the prescribed positions; and

the time period is measured for each of the prescribed positions.

13. The measuring apparatus as set forth in claim 12, further comprising a second calculator, operable to determine a difference between time periods measured at prescribed positions.

14. The measuring apparatus as set forth in claim 13, further comprising a third calculator, operable to obtain a cross-correlation coefficient between attenuation rates or oxygen saturations measured by the sensors,

wherein the difference is determined based on a time period from the reference time point to a time point at which the cross-correlation coefficient becomes maximum.