US5746206A - Isolated Layer Pulse Oximetry - Google Patents

Another disadvantage is that the calculated oxygen saturation worth is influenced by pulsatile signal contributions from many differing tissue layers, BloodVitals including the pores and 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 mixture. Specifically, the current invention allows for pulsed oximetry measurement which isolates arterial saturation levels for explicit ranges of tissue layers which rejects saturation levels of the tissue above or below the tissue of curiosity by using multiple spaced detectors and/or emitters. FIG. 4 is an overall block diagram displaying the foremost parts of an operational system employing the current invention. FIG. 6 is a graph of absorptivity vs. FIG. 7 is a graph comprising calculated oxygen saturation values utilizing the ideas of the invention for deep and shallow tissue measurements, and values obtained with out utilizing the ideas of the invention. FIG. 1A is a schematic diagram exhibiting the rules of operation of the present invention.

10 at subdermal tissue stage 12 having light 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 stage 14 having light absorption properties u a . It is deemed desirable to measure arterial oxygen saturation within the tissue layer 12 or the tissue layer 14 independently. Sixteen transmits electromagnetic radiation within the seen and near infrared area at two predetermined wavelengths (e.g. 660 nm and 905 nm). Emitter 16 is shown as a single entity in this example. However, totally different emitters could also be used for the different predetermined wavelengths, BloodVitals SPO2 if desired. If more than one emitter is used, it is most convenient that they be co-positioned to simulate a single level source. LED's are a most popular type of emitter. Sixteen travel usually alongside path 18 to a first detector 20 and along path 22 to a second detector 24 as proven.

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 skin layer 14 twice. Furthermore, as a result of paths 18 and 22 traverse skin layer 14 utilizing approximately the same angle, the first distinction between paths 22 and 18 is the difference between length L 2 and BloodVitals SPO2 length L 1 traversing subdermal layer 12, which is the tissue layer of interest. Therefore, it may be assumed that the distinction in absorption between path L 2 and path L 1 is straight attributable to subdermal layer 12, the tissue layer of curiosity, corresponding to the completely different spacings r 2 and r 1 . 12 could also be represented by l and the deeper path via the subdermal tissue by L 1 and L 2 , depending on which detector is taken into account.

Equation eight is equivalent 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 ) needs to be bigger than several times 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 no less than have equivalent counterparts influencing the two detectors. If the detectors are too close to each other, ⁇ FIG. 1B is a schematic diagram, much like FIG. 1A, showing the current invention using a number of emitters sixteen and 17 and BloodVitals SPO2 a single detector 24. Those of talent within the artwork will appreciate that the operation is similar to that described above. FIG. 2 is a perspective view of the preferred mode of affected person interface device 26 using the current invention. Planar floor 28 is positioned into contact with the skin of the patient throughout monitoring and measurement.

If fascinating, this position could also be maintained through adhesive or other mechanical means known in the art. Further, BloodVitals SPO2 if fascinating, floor 28 might have a curvature, and could also 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 features. FIG. Three is a partially sectioned view displaying patient interface machine 26 in operational place. Cable 32 conducts the electrical alerts to and from the monitoring circuitry as described below. All different elements are as previously described. FIG. Four is a block diagram displaying your entire monitoring and measurement system using the present invention. 36 and two wavelength driver 34 alternately turn on the red 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 within the artwork and could possibly be used, if desired.