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

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 and a second pathway different from the first pathway;

detecting emitted light scattered by a volume of tissue delivered along a third pathway and a fourth pathway different from the third pathway;

determining a first uniformity corresponding to the emitted light detected along the first pathway and the second pathway;

determining a second uniformity corresponding to the emitted light detected along third pathway and the fourth pathway;

determining a total uniformity in response to the determined first uniformity and the determined second uniformity; and

altering sensing by the device in response to the determined total uniformity.

2. The method of claim 1 , further comprising comparing the first uniformity and the second uniformity and altering sensing by the device in response to the comparing.

3. The method of claim 1 , further comprising:

determining whether a first 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;

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

determining the total uniformity in response to the determined first difference and the determined second difference.

4. The method of claim 3 , wherein determining the total uniformity comprises:

determining whether the first difference and the second difference are both less than the predetermined threshold; and

determining if both one of the first difference and the second difference is less than the threshold and the other of the first difference and the second difference is not less than the predetermined threshold.

5. The method of claim 4 , wherein altering sensing by the device comprises:

changing the functionality of the device in response to both one of the first difference and the second difference being less than the threshold and the other of the first difference and the second difference not being less than the predetermined threshold; and

disabling sensing by the device in response to determining both the first difference and the second difference not being less than the predetermined threshold.

6. The method of claim 4 , further comprising detecting a change in uniformity in response to the determined total uniformity, and wherein altering sensing by the device comprises generating an alert in response to the detected change.

7. The method of claim 1 , wherein determining a first uniformity comprises:

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

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

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

8. The method of claim 7 , 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.

9. 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 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.

10. 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 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.

11. A medical device for detecting signals, comprising:

a first portion to detect emitted light scattered by a volume of tissue delivered along a first pathway and a second pathway different from the first pathway;

a second portion to detect emitted light scattered by a volume of tissue delivered along a third pathway and a fourth pathway different from the third pathway; and

a processor configured to determine a first uniformity corresponding to the emitted light detected along the first pathway and the second pathway, determine a second uniformity corresponding to the emitted light detected along third pathway and the fourth pathway; determine a total uniformity in response to the determined first uniformity and the determined second uniformity, and alter sensing by the device in response to the determined total uniformity.

12. The device of claim 11 , wherein the processor is further configured to compare the first uniformity and the second uniformity and altering sensing by the device in response to the comparing.

13. The device of claim 11 , wherein the processor is further configured to determine whether a first 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, determine whether a second difference between the emitted light detected along the third pathway and the emitted light detected along the fourth pathway is greater than a predetermined threshold, and determine the total uniformity in response to the determined first difference and the determined second difference.

14. The device of claim 13 , wherein determining the total uniformity comprises:

determining whether the first difference and the second difference are both less than the predetermined threshold; and

determining if both one of the first difference and the second difference is less than the threshold and the other of the first difference and the second difference is not less than the predetermined threshold.

15. The device of claim 14 , wherein altering sensing by the device comprises:

changing the functionality of the device in response to both one of the first difference and the second difference being less than the threshold and the other of the first difference and the second difference not being less than the predetermined threshold; and

disabling sensing by the device in response to determining both the first difference and the second difference not being less than the predetermined threshold.

16. The device of claim 14 , wherein the processor is further configured to:

detect a change in uniformity in response to the determined total uniformity, and generate an alert in response to the detected change.

17. The device of claim 11 , wherein the processor is further configured to detect emitted light scattered by the volume of tissue delivered along the first pathway to generate corresponding first detected light intensity output signals, detect emitted light scattered by the volume of tissue delivered along the second pathway to generate corresponding second detected light intensity output signals, and determine whether a difference between the light emitted along the first pathway and the light emitted along the second pathway is greater than a predetermined threshold.

18. The device of claim 17 , further comprising a monitoring module couple to the processor and configured to determine 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 determine 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 the processor is further configured to compare the first and second oxygen saturation measurement and determine 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.

19. The device of claim 17 , wherein the monitoring module is further configured to determine 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, determine 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, determine 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, determine 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, and determine 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, wherein the processor is further configured to compare the first and second oxygen saturation measurement.

20. The method of claim 17 , wherein the monitoring module is further configured to determine 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, determine 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, determine 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, determine 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, determine 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, determine 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, and determine 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, wherein the processor is further configured to compare the first and second oxygen saturation measurement.

21. 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 and a second pathway different from the first pathway;

detecting emitted light scattered by a volume of tissue delivered along a third pathway and a fourth pathway different from the third pathway;

determining a first uniformity corresponding to the emitted light detected along the first pathway and the second pathway;

determining a second uniformity corresponding to the emitted light detected along third pathway and the fourth pathway;

determining a total uniformity in response to the determined first uniformity and the determined second uniformity; and

altering sensing by the device in response to the determined total uniformity.