US5746206A - Isolated Layer Pulse Oximetry - Google Patents

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Another disadvantage is that the calculated oxygen saturation value is influenced by pulsatile signal contributions from many differing tissue layers, together with the skin or floor tissue layer. U.S. Pat. No. 5,188,108 issued to Secker suggests the usage of a plurality of emitters and/or receivers to supply a number of emitter/receiver combination. Specifically, the current invention permits for pulsed oximetry measurement which isolates arterial saturation levels for specific ranges of tissue layers which rejects saturation levels of the tissue above or under the tissue of curiosity by using a number of spaced detectors and/or emitters. FIG. 4 is an overall block diagram displaying the key components of an operational system employing the present invention. FIG. 6 is a graph of absorptivity vs. FIG. 7 is a graph comprising calculated oxygen saturation values utilizing the principles of the invention for deep and shallow tissue measurements, and values obtained without utilizing the principles of the invention. FIG. 1A is a schematic diagram showing the ideas of operation of the present invention.



10 at subdermal tissue stage 12 having mild absorption properties u b . 14 Interposed between the non-invasive monitoring and measurement system (not shown) and subdermal tissue degree 12, is pores and skin or floor tissue degree 14 having mild absorption properties u a . It is deemed fascinating to measure arterial oxygen saturation in the tissue layer 12 or the tissue layer 14 independently. 16 transmits electromagnetic radiation in the seen and close to infrared region at two predetermined wavelengths (e.g. 660 nm and 905 nm). Emitter 16 is proven as a single entity in this example. However, totally different emitters may be used for the totally different predetermined wavelengths, if desired. If multiple emitter is used, it's most handy that they be co-situated to simulate a single level source. LED's are a most popular sort of emitter. 16 travel usually along path 18 to a first detector 20 and alongside path 22 to a second detector 24 as shown.



18 within layer 12 (with absorption u b ) is proven as L 1 and the length of path 22 within layer 12 is shown as L 2 . Detector 20 is spaced a distance of r 1 from emitter sixteen and detector 24 is spaced at a distance of r 2 . 18 and path 22 traverse pores and skin layer 14 twice. Furthermore, as a result of paths 18 and 22 traverse skin layer 14 utilizing approximately the same angle, the primary distinction between paths 22 and 18 is the distinction between length L 2 and BloodVitals health size L 1 traversing subdermal layer 12, which is the tissue layer of interest. Therefore, it can be assumed that the difference in absorption between path L 2 and path L 1 is straight attributable to subdermal layer 12, the tissue layer of interest, corresponding to the completely different spacings r 2 and r 1 . 12 may be represented by l and the deeper path by way of the subdermal tissue by L 1 and L 2 , relying on which detector is taken into account.



Equation eight is equal to standard pulse oximetry if the second detector is eliminated. 16,20 (i.e. r 1 ) and the second emitter/detector pair 16,24 (i.e. r 2 ) should be larger than several times the skin thickness (i.e. r 1 ,r 2 much better than d) in order that the 4 occurrences of are all roughly equal, or not less than have equivalent counterparts influencing the 2 detectors. If the detectors are too close to each other, ⁇ FIG. 1B is a schematic diagram, similar to FIG. 1A, displaying the present invention using a number of emitters sixteen and 17 and a single detector 24. Those of skill within the art will admire that the operation is much like that described above. FIG. 2 is a perspective view of the popular mode of patient interface device 26 using the present invention. Planar surface 28 is placed into contact with the pores and skin of the patient during monitoring and measurement.



If desirable, this place could also be maintained by way of adhesive or other mechanical means identified within the art. Further, if fascinating, surface 28 could have a curvature, BloodVitals health and may be both flexible or rigid. 16, detector 20, and detector 24 are as previously discussed. Wiring electrically couples emitter 16, detector 20, and detector 24 to the circuitry which performs the monitoring functions. FIG. 3 is a partially sectioned view showing affected person interface machine 26 in operational position. Cable 32 conducts the electrical indicators to and from the monitoring circuitry as described under. All different elements are as previously described. FIG. 4 is a block diagram exhibiting the whole monitoring and measurement system employing the current invention. 36 and two wavelength driver 34 alternately turn on the red and infrared LED's 16 at a desired chop frequency (e.g. 1,600 hz). CPU forty eight for calculating arterial oxygen saturation. PCT/US94/03546, the disclosure of which is integrated herein by reference. Alternate management electronics are known within the art and may very well be used, if desired.