Device and method for monitoring of absolute oxygen saturation and tissue hemoglobin concentration

• US 8,634,890 B2
• Filed: 06/10/2010
• Issued: 01/21/2014
• Est. Priority Date: 06/10/2009
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Kuhn, Jonathan L., Cinbis, Can, Carney, James K.
• Primary Examiner(s): Laballe, Clayton E
• Assistant Examiner(s): Fenwick, Warren K
• Application Number:
  US12/797,744
• Publication Number:
  US 20100317938A1
• Time in Patent Office: 1,321 Days
• Field of Search: 600/310, 600/323
• US Class Current: 600/323
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/36557 controlled by chemical substances in blood

Abstract

A method and medical device for detecting signals that detects emitted light scattered by a volume of tissue delivered along a first pathway at a plurality of wavelengths to generate corresponding first detected light intensity output signals, detects emitted light scattered by the volume of tissue delivered along a second pathway different from the first pathway at a plurality of wavelengths to generate corresponding second detected light intensity output signals, determines whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a predetermined threshold, and alters sensing by the device in response to the determining whether a difference is greater than the predetermined threshold.

Claims

1. A method of detecting signals in a medical device, comprising:

detecting emitted light scattered by a volume of tissue delivered along a first pathway to generate corresponding first detected light intensity output signals;

detecting emitted light scattered by the volume of tissue delivered along a second pathway different from the first pathway to generate corresponding second detected light intensity output signals;

determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a predetermined threshold; and

altering sensing by the device in response to the determining whether a difference is greater than the predetermined threshold.

2. The method of claim 1, further comprising:

determining a first oxygen saturation measurement corresponding to detected light emitted along the first pathway in response to the first detected light intensity output signals; and

determining a second oxygen saturation measurement corresponding to detected light emitted along the second pathway in response to the second detected light intensity output signals, wherein determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a predetermined threshold comprises comparing the first and second oxygen saturation measurement.

3. The method of claim 2, wherein altering sensing by the device comprises selecting between the first pathway and the second pathway.

4. The method of claim 2, wherein determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a predetermined threshold comprises determining levels of uniformity of the volume of tissue.

5. The method of claim 4, wherein determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a predetermined threshold comprises:

determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is less than a first level threshold;

identifying the volume of tissue as having a first tissue uniformity in response the difference being less than the first level threshold;

determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a second level threshold different from the first level threshold; and

identifying the volume of tissue as having a second tissue uniformity in response the difference being both less than the second level threshold and not less than the first level threshold.

6. The method of claim 5, wherein altering sensing by the device comprises selecting between the first pathway and the second pathway in response to the identifying.

7. The method of claim 1, wherein determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a predetermined threshold comprises:

determining an attenuation measurement for each wavelength of a plurality of wavelengths of the first pathway and the second pathway in response to the first and second detected light intensity output signals;

determining a second derivative of the attenuation measurement for a first wavelength and a second wavelength of a plurality of wavelengths corresponding to the first pathway in response to only the first detected light intensity output signals;

determining a second derivative of the attenuation measurement for a first wavelength and a second wavelength of a plurality of wavelengths corresponding to the second pathway in response to only the second detected light intensity output signals;

determining a first oxygen saturation measurement corresponding to detected light emitted along the first pathway in response to the determined second derivative associated with the first pathway;

determining a second oxygen saturation measurement corresponding to detected light emitted along the second pathway in response to the determined second derivative associated with the second pathway; and

comparing the first and second oxygen saturation measurement.

8. The method of claim 7, wherein determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a predetermined threshold comprises determining levels of uniformity of the volume of tissue.

9. The method of claim 8, wherein determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a predetermined threshold comprises:

determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is less than a first level threshold;

identifying the volume of tissue as having a first tissue uniformity in response the difference being less than the first level threshold;

determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a second level threshold different from the first level threshold; and

identifying the volume of tissue as having a second tissue uniformity in response the difference being both less than the second level threshold and not less than the first level threshold.

10. The method of claim 9, wherein altering sensing by the device comprises selecting between the first pathway and the second pathway in response to the identifying.

11. The method of claim 1, wherein determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a predetermined threshold comprises:

determining an attenuation measurement for each wavelength of a plurality of wavelengths of the first pathway and the second pathway in response to the first and second detected light intensity output signals;

determining a second derivative of the attenuation measurement for a first wavelength and a second wavelength of a plurality of wavelengths corresponding to the first pathway in response to only the first detected light intensity output signals;

determining a second derivative of the attenuation measurement for a first wavelength and a second wavelength of a plurality of wavelengths corresponding to the second pathway in response to only the second detected light intensity output signals;

determining a scaled second derivative of the attenuation measurement of the first wavelength for the first pathway using the determined second derivative of the attenuation of the second wavelength for the first pathway;

determining a first oxygen saturation measurement corresponding to detected light emitted along the first pathway in response to the determined scaled second derivative for the first pathway;

determining a scaled second derivative of the attenuation measurement of the first wavelength for the second pathway using the determined second derivative of the attenuation of the second wavelength for the second pathway;

determining a second oxygen saturation measurement corresponding to detected light emitted along the first pathway in response to the determined scaled second derivative for the second pathway; and

comparing the first and second oxygen saturation measurement.

12. A non-transitory computer readable medium having computer executable instructions for performing a method comprising:

detecting emitted light scattered by a volume of tissue delivered along a first pathway at a plurality of wavelengths to generate corresponding first detected light intensity output signals;

detecting emitted light scattered by the volume of tissue delivered along a second pathway different from the first pathway at a plurality of wavelengths to generate corresponding second detected light intensity output signals;

determining whether a difference between the emitted light detected along the first pathway and the emitted light detected along the second pathway is greater than a predetermined threshold; and

altering sensing by the device in response to the determining whether a difference is greater than the predetermined threshold.