US5746206A - Isolated Layer Pulse Oximetry - Google Patents

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Another drawback is that the calculated oxygen saturation value is influenced by pulsatile sign contributions from many differing tissue layers, including the skin or floor tissue layer. U.S. Pat. No. 5,188,108 issued to Secker suggests the use of a plurality of emitters and/or receivers to provide multiple emitter/receiver mixture. Specifically, the current invention allows for pulsed oximetry measurement which isolates arterial saturation ranges for specific ranges of tissue layers which rejects saturation levels of the tissue above or beneath the tissue of interest by using a number of spaced detectors and/or emitters. FIG. Four is an total block diagram displaying the major elements 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 using the rules of the invention for deep and shallow tissue measurements, and values obtained with out using the rules of the invention. FIG. 1A is a schematic diagram exhibiting the principles of operation of the current invention.



10 at subdermal tissue level 12 having mild absorption properties u b . 14 Interposed between the non-invasive monitoring and measurement system (not proven) and subdermal tissue stage 12, is skin or surface tissue level 14 having light absorption properties u a . It is deemed fascinating to measure arterial oxygen saturation within the tissue layer 12 or the tissue layer 14 independently. 16 transmits electromagnetic radiation in the visible and near infrared region at two predetermined wavelengths (e.g. 660 nm and 905 nm). Emitter sixteen is shown as a single entity in this instance. However, totally different emitters may be used for the different predetermined wavelengths, if desired. If a couple of emitter is used, it is most convenient that they be co-positioned to simulate a single level source. LED's are a preferred sort of emitter. Sixteen journey typically alongside path 18 to a primary detector 20 and BloodVitals device along 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 16 and detector 24 is spaced at a distance of r 2 . 18 and path 22 traverse pores and skin layer 14 twice. Furthermore, because paths 18 and 22 traverse pores and skin layer 14 using roughly the identical angle, the first distinction between paths 22 and 18 is the distinction between size L 2 and length L 1 traversing subdermal layer 12, which is the tissue layer of interest. Therefore, it can be assumed that the distinction in absorption between path L 2 and path L 1 is instantly 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 means of the subdermal tissue by L 1 and L 2 , relying on which detector is considered.



Equation eight is equal to conventional pulse oximetry if the second detector BloodVitals device 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 occasions the pores and skin thickness (i.e. r 1 ,r 2 much higher than d) so that the four occurrences of are all approximately equal, or not less than have equivalent counterparts influencing the two detectors. If the detectors are too close to each other, ⁇ FIG. 1B is a schematic diagram, similar to FIG. 1A, displaying the present invention employing multiple emitters 16 and BloodVitals SPO2 17 and a single detector 24. Those of skill within the artwork will admire that the operation is much like that described above. FIG. 2 is a perspective view of the preferred mode of patient interface system 26 using the present invention. Planar floor 28 is positioned into contact with the pores and skin of the patient throughout monitoring and measurement.



If desirable, this place may be maintained by way of adhesive or different mechanical means known within the artwork. Further, if fascinating, surface 28 might have a curvature, and may be both versatile or rigid. 16, detector 20, and detector 24 are as previously discussed. Wiring electrically couples emitter 16, detector 20, and BloodVitals SPO2 detector 24 to the circuitry which performs the monitoring capabilities. FIG. Three is a partially sectioned view displaying patient interface system 26 in operational position. Cable 32 conducts the electrical alerts to and from the monitoring circuitry as described below. All different components are as previously described. FIG. 4 is a block diagram displaying your complete monitoring and measurement system using the current invention. 36 and two wavelength driver 34 alternately turn on the purple and infrared LED's sixteen 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 incorporated herein by reference. Alternate control electronics are recognized in the art and may very well be used, BloodVitals device if desired.

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