Optical device

• US 20050101850A1
• Filed: 11/22/2004
• Published: 05/12/2005
• Est. Priority Date: 08/13/1998
• Status: Active Grant

• Current Assignee: Whitland Research Ltd. (Edwards Lifesciences Corporation)
• Original Assignee: Edwards Lifesciences LLC (Edwards Lifesciences Corporation)
• Inventors: Parker, Dawood
• Granted Patent: US 7,236,813 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/1491 Heated applicators

Abstract

There is described a sensor device which comprises light source means for emitting a light beam, photodetector means for receiving the light beam after passing through or being reflected within living tissue and arranged to provide signals corresponding to the intensities of the respective wavelength of light received by the photodetector means characterised in that the sensor device measures blood oxygen saturation. The device can be used in conjunction with a conventional pulse oximeter. There is also described a method of measuring blood oxygen saturation.

Claims

1-32. -32. (canceled)

33. A method for SO₂ monitoring, coring the steps of:

calculating an estimate of SO₂ in blood to be monitored; and

,

correcting said estimate of SO₂ in blood by a scaling factor.

34. The method for SO₂ monitoring according to claim 33, further comprising the steps of:

transmitting light containing a plurality of wavelengths into the blood;

measuring a remitted spectrum over the plurality of wavelengths;

calculating a measured blood absorption spectrum from the remitted spectrum;

estimating local rates of change in the measured blood absorption spectrum at a plurality of the wavelengths, including at least one isobestic wavelength; and

,

calculating the estimate of SO₂ as a function of absolute values of the local rates of change of the measured blood absorption spectrum.

35. The method for SO₂ monitoring according to claim 34, wherein before said step of calculating the estimate of SO₂, further comprising the steps of:

removing effects of light scattering from the measured blood absorption spectrum;

calculating an area under the measured blood absorption spectrum after said step of removing effects of light scattering, and,

normalizing the measured blood absorption spectrum by the area under the measured blood absorption spectrum determined during said step of calculating.

36. The method for SO₂ monitoring according to claim 34, further comprising the step of applying a Kubelka Monk transformation to the measured blood absorption spectrum.

37. The method for SO₂ monitoring according to claim 34, wherein the step of calculating the estimate of SO₂ comprises the steps of:

computing a hemoglobin index value as a function of absolute values of the local rates of change of the measured blood absorption spectrum between a plurality of pairs of isobestic points, whereby the hemoglobin index value is independent of blood oxygenation;

computing an oxygenation parameter as a function of absolute values of the local rates of change of the measured blood absorption spectrum between a plurality of isobestic points and at least one non-isobestic point, whereby the oxygenation parameter is dependent on blood oxygenation;

normalizing the oxygenation parameter by the hemoglobin index value; and

,

estimating SO₂ as a measure of the level of the normalized oxygenation parameter relative to a predetermined fully deoxygenated reference value and a fully oxygenated reference value.

38. The method for SO₂ monitoring according to claim 34, further comprising the steps in the order of:

transmitting light containing a plurality of wavelengths into the blood;

measuring the remitted spectrum over the plurality of wavelengths;

calculating the measured blood absorption spectrum from the remitted spectrum;

estimating the local rates of change in the measured blood absorption spectrum at a plurality of the wavelengths, including at least one isobestic wavelength; and

,

calculating the estimate of SO₂ as a function of absolute values of the local rates of change of the measured blood absorption spectrum.