USOO5?9734 IA
`5,797,841
`[11] Patent Number:
`[191
`United States Patent
`
`Delonzor et al.
`[45] Date of Patent:
`Aug. 25, I998
`
`[54]
`
`SHUNT BARRIER IN PULSE OXIMETER
`SENSQR
`
`[75] mwnmm; Russ ]}e[onzm»_ Union City; paul D_
`Mannheimer. Danvillc: Michael E.
`Fain. Mountain View: Don Hannula.
`San Luis Obispo. all of Calif.
`
`[73] Assignee: Nellcor Puritan Bennett Incorporated.
`PlC3SflI110|1- C8111
`
`[21] Appl. No.: 611,151
`
`[22]
`
`Filed:
`
`Mar. 5, 1996
`
`Int. CL6
`[51]
`[521 U.S. CI.
`
`A61}! 5390
`6001323; 6001322; 600344;
`6001310; 250x221
`1231533. 664-'1‘;
`[531 Field of Search
`3553941; 255,E27_1l_ 2043.‘ 221; 500,-319_
`323 323‘ 325_ 344
`
`[56]
`
`Rgfgmmgs Cited
`U.S. PA'I‘ENT DOCUMENTS
`
`5.090.-H0
`5.099.842
`5.285383
`
`231992 Saper el al_
`31'I99‘2 Mannheirner et a1.
`211994 Seeker
`
`5.-1»(D.7'}".-'
`
`411995 Warring el al.
`
`..
`
`
`128.1633
`123E633
`128F633
`
`1283633
`
`FOREIGN PATENT DOCUMENTS
`0I2?94':'
`1231984
`European Pat. Ofl'.
`...............
`
`IZSIG33
`
`Pnimarjy Elzamfner-—Jenni.fer Bahr
`Assistant EJcaminer—Bryan K. Yamell
`.4!wme_\; Agent. or Firm—'I'ownscnd and Townsend and
`Crew LLP
`
`[57]
`
`ABSTRACT
`
`A pulse oximetcr sensor having an emitl;cr(s} and a detector.
`with a layer having a firs! portion over Ihe emitter and a
`second portion of layer over the detector is provided. A
`banier is included behveen the first and second porfions of
`the overlying layer to substantially block radiation of the
`wavelengths emitted by the ern.itter(s). Preferably. me barrier
`reduces the radiation shunted to less than 10% of the
`radiation detected. and more preferably to less than 1% of
`the radiation detected.
`
`3.'I69.9T4
`
`1111973 Smart et al.
`
`1281633
`
`9 Claims, 6 Drawing Sheets
`
`91
`
`92
`
`96
`
`94
`
`I
`
`91
`
`93
`
`100
`
`0001
`
`U.S. Patent No. 8,989,830
`
`Apple Inc.
`APL1010
`
`0001
`
`Apple Inc.
`APL1010
`U.S. Patent No. 8,989,830
`
`

`
`U.S. Patent
`
`Aug. 25, 1998
`
`Sheet 1 of 45
`
`5,797,841
`
`PR1ORART
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`0002
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`0002
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`

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`U.S. Patent
`
`Aug. 25, 1993
`
`Sheet 2 of 6
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`5,797,841
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`FIG.3A
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`FIG. 4
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`0003
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`0003
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`

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`U.S. Patent
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`Aug. 25, 1993
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`Sheet 3 of 6
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`5,797,841
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`0004
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`0004
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`

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`U.S. Patent
`
`Aug. 25, 1993
`
`Sheet 4 of6
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`5,797,841
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`72
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`79
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`0005
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`0005
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`U.S. Patent
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`Aug. 25, 1993
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`Sheet 5 of6
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`5,797,841
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`{ill
`.\\.
`\\§\\\\\\\\\\\\\\\s
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`I...I
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`..\\\\\\\\\\k
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`4.!9
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`92
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`94
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`M%
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`100
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`FIG. 9
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`FIG. 10
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`113
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`116
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`0006
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`0006
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`

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`U.S. Patent
`
`Aug. 25, 1993
`
`Sheet 6 of 6
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`5,797,841
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`133
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`130
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`134
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`138
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`132
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`136
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`0007
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`0007
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`5.797.841
`
`1
`SHUNT BARRIER IN PULSE OXIMETER
`SENSOR
`
`BACKGROUND OF THE INVENTION
`
`5
`
`The present invention relates to pulse oximcter sensors.
`and in particular to methods and apparatus for preventing the
`shunting of light between the emitter and detector without
`passing through blood-perfused tissue.
`Pulse oxirnetry is typically used to measure various blood
`flow characteristics including. but not limited to. the blood«
`oxygen saturation of hemoglobin in arterial blood.
`the
`volume of individual blood pulsations supplying the tissue.
`and the rate of blood pulsations corresponding to each
`heartbeat of a patient. Measurement of these characteristics
`has been accomplished by use of a non-invasive sensor
`which scatters light through a portion of the patient‘s tissue
`where blood perfuses the tissue. and photoelectrically senses
`the absorption of light in such tissue. The amount of light
`absorbed is then used to calculate the amount of blood
`constituent being measured
`The light scattered through the tissue is selected to be of
`one or more wavelengths that are absorbed by the blood in
`an amount representative of the amount of the blood con-
`SI.i‘IJ.lcllt present in the blood. The amount of transmitted light
`scattered through the tissue will vary in accordance with the
`changing amount of blood constituent in the tissue and the
`related light absorption. For measuring blood oxygen level.
`such sensors have typically been provided with a light
`source that
`is adapted to generate light of at least two
`dijferent wavelengths. and with photodetectors sensitive to
`both of those wavelengths. in accordance with known tech-
`niques for measuring blood oxygen saturation.
`Known non-invasive sensors include devices that are
`secured to a portion of the body. such as a finger. an ear or
`the scalp. In animals and humans. the tissue of these body
`portions is perfused with blood and the tissue surface is
`readily accessible to the sensor.
`One problem with such sensors is the detection of ambient
`light by the photodetector. which can distort the signal.
`Another problem is the shunting of light directly from the
`photocmitter to the photodetector without passing through
`blood-perfused tissue. FIG. 1 illustrates two different types
`of light shunting that can intafere with proper detection of
`oxygen saturation levels. As shown in FIG. 1. a sensor 10 is
`wrapped around the tip of a finger 11 The sensor includes
`a light emitter 14 and a light detector 16. Preferably. light
`from emitter 14 passes through finger 12 to be detected at
`detector 16. except for amounts absorbed by the blood
`perfused tissue.
`A fi.l.'Sl type of shunting. referred to as type 1 shunting. is
`shunting inside the sensor body as illustrated by light path
`18. shown as a wavy line in FIG. 1. Light shunts through the
`sensor body with the sensor body acting like a light guide or
`light pipe. directing light from the emitter to the detector.
`A second type of shunting. referred to as type 2 shunting.
`is illustrated by line 20 in FIG. I. This type of light exits the
`sensor
`itself. but reaches the detector without passing
`through the finger. In the embodiment shown. the light can
`go around the side of the finger. perhaps by being piped by
`the sensor body to the edges of the sensor and thenjurnping
`through the air gap between the two edges which are
`wrapped around the side of the finger.
`The problem of light shunting can be exacerbated by
`layers placed over the emitter and detector. Often.
`it
`is
`desirable not to have the emitter and detector in direct
`
`35
`
`45
`
`55
`
`2
`contact with the patient‘s skin because motion artifacts can
`be reduced by placing a thin layer of adhesive between these
`components and the slcin. Thus. the emitter and detector are
`typically covered with a clear layer which isolates them
`from the patient. but allows light to transmit through. The
`feature of allowing light to transmit through the layer also
`provides the capability for the clear layer to provide a wave
`guide effect to shunt light around the finger to the detector.
`Such layers covering the emitter and detector can be
`originally included in the sensor. or can be added during a
`reinforcing or modifying procedtne. or during a remanuiac-
`ture of the sensor. In a remanufactute of a sensor. a sensor
`which has been used may have its outer. adhesive transpar-
`ent layer removed. Such a layer is shown in FIG. 2 as a
`transparent
`layer 22 over a sensor 10. Layer 2 is an
`adhesive. transparent layer placed over a substrate layer 24.
`upon which emitter 14 and detector 16 are mounted. along
`with any other associated electronics. Layer 2 thus serves
`both to protect the emitter and detector from the patient. and
`to adhere the sensor to the patient. During remanufacture.
`this layer can be stripped oft‘. and a new layer placed thereon.
`Alternately. layer 22 may be left in place. Such a sensor.
`with an adhesive outer layer. may be a disposable sensor.
`since it would not be desirable to have the same adhesive
`used from one patient to another. and an adhesive is difficult
`to clean without removing the adhesive. Accordingly. a
`modification of such a sensor may involve laminating sensor
`10 to cover over the adhesive. by adding an additional
`lamination layer 23 (shown partially broken away) over
`layer 22. The lamination layer is itself another layer for
`shunting light undesirably from the emitter to the detector.
`Once laminated. in one method. the sensor is then placed
`into a pocket 26 of a sheath 32. Sheath 32 includes a
`transparent cover 28 on an adhesive layer 30. Layer 30 is
`adhesive for attaching to a patient. Layer 28 may also
`optionally be adhesive-coated on the side which faces the
`patient. Such a modified sensor can be reused by using a new
`sheath 32. Transparent layer 28 forms yet another shunting
`path for the light
`A commercially available remanufactured sensor. similar
`in design to the sensor of FIG. 2. is available from Medical
`Taping Systems. Inc. Another example of a sheath or sleeve
`for a sensor is shown in U.S. Pat. No. 5.090.410. assigned
`to Datascope Investment Corp.
`In addition. when a sheath such as 32 is folded over the
`end of a patient’s finger. it has a tendency to form wrinkles.
`with small air gaps in—between the wrin.‘lr.led portions. The air
`gaps can actually exacerbate the shunting problem. with
`light jumping more easily through the air gaps from one
`portion of the transparent layer to another.
`Other types of sensors have not used a solid transparent
`layer 22 as shown in FIG. 2. For instance.
`the Nelloor
`Puritan Bennett R-lS 0x.isensot® and N-25 Neonatalmdult
`Oxisensor products use a whitecoloned substrate with sepa-
`rate transparent strips placed over the emitter and detector
`(such as strips 11 and 13 illustrated in FIG. I). The trans-
`parent strips are adhesive for adhering to the patient. Since
`two strips are used. an air gap {gap 15 in FIG. 1) occurs
`between the transparent layers. As noted above. light can
`jump such an air gap. and thus a gap by itself may not
`eliminate all shunting problems. The use of a darlt-colored
`substrate may reduce the amount of shunting. if the selected
`color is opaque to the wavelengths of interest from the
`emitter. 650 um red and 905 um infrared in a typical
`implementation. However. the white substrate typically used
`in the R-15 and N25 sensors is substantially translucent and
`thus has limited light blocking qualities.
`
`0008
`
`0008
`
`

`
`5.397.841
`
`3
`It has been found that shunted light can significantly afiect
`the accuracy of oxygen saturation readings using a pulse
`oximeter. Accordingly. there is a need to develop a barrier to
`such light. to improve the accuracy of pulse oximeter sen-
`sors.
`
`SUMMARY OF THE ]NVEN'I'ION
`
`The present invention provides a sensor having an emitter
`(s) and a detector. with a layer having a first portion over the
`emitter and a second portion over the detector. A shunt
`barrier is included between the first and second portions of
`the overlying layer to substantially block transmission of
`radiation of the wavelengths emitted by the emitter(s).
`Preferably. the shunt ba.t:rier reduces the radiation shunted to
`less than 10% of the total radiation detected. and more
`preferably to less than 1% of the total radiation detected.
`when the sensor is used on patients having the most opaque
`tissue of all patients in the target population.
`In particular for a remanufnctured or reinforced or modi-
`fied sensor. the barrier is added in at least one. and more
`preferably in all. of the extra layers added or replaced during
`the remanufacturing. reinforcing or modifying process.
`The barrier of the present invention may take a number of
`specific forms. In one embodiment. a woven or fiber mate-
`rial is included between the emitter and detector. In another
`embodiment. the layerin-between the emitter and detector is
`pigmented with a color which is substantially opaque for the
`wavelengths of interest. while the portion above the emitter
`and detector is substantially transparent.
`In another
`embodiment. the entire layer is partially opaque. but is thin
`enough so that light transmitted through is able to penetrate
`the partially opaque layer. while light travelling the length of
`the layer would have a greater distance to travel and would
`be substantially absorbed.
`Another shunt barrier is the insertion of perforations in the
`layer between the emitter and detector. The perforations may
`provide air gaps. which still will shunt some light. or may be
`filled with other material or have the insides of the perfo-
`rations colcred with an opaque color.
`In another embodiment. the layer between the emitter and
`detector is made very thin. such as by embossing. welding
`or heat sealing. The thinness of the material will l.i.mit its
`effectiveness as a light pipe in the wavelengths of interest.
`red and infrared.
`In another embodiment. a deformable. opaque material.
`such as foam. is included between the emitter and detector.
`to be compressed upon application to a finger or other body
`part and tilt any gap that might otherwise form through
`wrinkles or otherwise upon application of the sensor.
`In another embodiment. an adhesive is applied in a gap
`between two layers over the etnitter and detector, to cause an
`underlying layer to come in contact with the patient. thus
`filling the air gap and preventing shunting along that path.
`While most of the illustrative examples given in this
`specification are shown as sensors adapted to be wrapped
`onto a digit. so that light is trans.t'n.'ttted through the digit. it
`will be clear to those skilled in the art that the design
`principles illustrated may be applied to any “transrnittance“
`or “reflectance” sensors for pulse oximetry. A typical reflec-
`tance sensor is the Nellcor Puritan Bennett RS~10.
`For a further understanding of the nature and advantages
`of the invention. reference should be made to the following
`description taken in conjunction with the accompanying
`drawings.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a diagram illustrating the shunting that occurs
`upon the placement of a sensor over a finger:
`
`4
`
`FIG. 2 is a diagram of a sensor being placed within a
`reusable sheath in a sensor modification operation;
`FIGS. 3A and 3B are diagrams of one embodiment of a
`shunt barrier showing an opaque film abutting both an air
`gap and another layer;
`FIG. 4 is a diagram of a sensor with a woven or fiber
`material for a shunt barrier’:
`
`I0
`
`FIG. 5 is a diagrain of a sensor with a partially opaque
`material for a shunt barrier. with a trade-off between trans-
`mission iulensity and preventing shunting:
`FIG. 6 is a diagram of a sensor using perforations as a
`shunt banier:
`
`is a diagram of a sensor with a thinned layer
`‘I’
`FIG.
`between emitter and detector as a shunt barrier;
`
`FIG. 8 is a diagram of a sensor using differential coloring
`as a shunt barrier;
`FIG. 9 is a diagram of a sensor using an adhesive in a gap
`between layers over the emitter and detector for a shunt
`barrier;
`FIG. 10 is a diagam ofa sensor usinga foam pad between
`the emitter and detector as a shunt barrier;
`FIG. 11 is a diagram of a sensor using a solid barrier as
`a shunt harder;
`
`FIG. 12 is a diagram of a sensor showing the use of
`overlapping layers as a shunt barrier;
`FIG. 13 is a diagram of a sensor using a barrier of metal
`traces forming a tortuous path between emitter and detector
`as a shunt barrier; and
`FIG. 14 is a diagram of a sheath incorporating a colored
`ring around the emitter and detector windows as a shunt
`barrier.
`
`DESCRIPTION OF THE PREFERRED
`EMIBODIMEN'I'
`
`FIGS. 3A and 3B illustrate the use of an opaque film
`adjacent another layer or an air gap to absorb shunting light.
`FIG. 3A shows the opaque film 34. before assembly being
`placed over layers 36. 36' separated by an air gap 38. Layers
`36. 36' may be mounted on a common substrate (not shown).
`I-[oles 4t! and 42 are shown for the emitter and detector.
`Alternately. these can be windows or simply a solid portion
`of a transparent layer. FIG. 3B shows the assembled Iowa
`layer and opaque film layer 34. As light attempts to shunt
`from emitter area 40 to detector area 42. either passing
`through the air gap 38 or through layers 36 and 36‘. it will
`bounce back and forth between the boundaries of the layer
`and tl'n'ough the air gap. Some of the light that would
`nomzally hit the top end of layer 36 or 36‘ and bounce back
`into the middle of the layer. will instead pass into and be
`absorbed by opaque layer 34. which is tightly coupled to die
`layers 36 and 36'.
`FIG. 4 illustrates the use of a woven or fiber material 44
`on layers 36 and 36'. and filling the air gap 38 of FIG. 3A.
`Fibers in the material will absorb light. thus attenuating light
`attempting to shout from emitter area 40 to detector area 42.
`An additional covet
`layer 46 may be placed over the
`assembly. and which will need to be at
`least partially
`transparent for light to escape and be detected. Layer 46 can
`function as another shunting layer. By abutting up against
`the woven or fiber material 44. light will be absorbed out of
`that layer in the same manner as the opaque film 34 of FIG.
`3A and B. Alternatcly. the fiber and woven material can be
`inserted into layer 46 between the emitter and detector.
`FIG. 5 shows an alternate embodiment in which a layer 50
`is used with an emitter 52 placed on top of it. Alternately.
`
`45
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`$5
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`0009
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`0009
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`

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`5397.84]
`
`6
`preferably no more than 0.025 mm. in order to limit its
`shunting effect.
`
`FIG. 8 shows a sensor having a layer 80 for an emitter 81
`and a detector 82. having n-ansparent windows 83 and 84.
`respectively. A substrate layer 85 supports the emitter and
`detector. with light being transmitted through transparent
`window 83 and received through window 84.
`In one
`embodiment. the entire layer 80 is opaque. leaving trans-
`ro parent portions 83 and M. Alternately. the entire layer 80
`may be transparent. or of one color with the windows of
`another or transparent. In addition. a portion 86 of layer 80
`between the emitter and detector may be colored a substan-
`tially opaque color to prevent the shunting of fight of the
`wavelengths of interest. In alternate embodiments. portion
`86 may be of different shapes. and may partially or totally
`enclose the windows for the emitter and detector.
`
`FIG. 6 shows another embodiment of the invention in
`which a layer 60 over an emitter 62 and detector 64 has a
`series of perforations 66. These perforations block the light
`path and scatter the light attempting to shunt between the
`emitter 62 and detector 64 through layer 60. Although light
`tends to jump air gaps. by providing multiple air gaps in
`different orientations. the light can be somewhat etfectively
`scattered. Alternately. the perforations could be fi.lled with a
`colored filling material or putty to block the light that might
`otherwise jump the air gaps. or could have the inside walls
`of the perforations colored. Alrernately. embossing (or other
`variations in thickness) could be used rather than perfora-
`tions.
`
`35
`
`5
`layer 50 could have holes 54 and 56 over the emitter and
`detector. with the emitter 52 being placed through hole 54
`onto an underlying layer. A partially opaque layer 58 is
`placed above emitter 52 in the embodiment shown. Layer 58
`may extend a portion of the way or all of the way over to
`where the detector is. The opacity of layer 58 is chosen in
`conjunction with its thickness to allow transmission of
`substantially all of the light from emitter 52 through the
`layer. while substantially reducing the amount of light
`shunted in a path transverse through the layer from the
`emitter to the detector. Layer 58 preferably attenuates the
`shunted light so that it is less than 10%. and more preferably
`less than 1% of the total light received by the detector.
`Additionally. of the.
`light detected by the detector and
`convened into electrical signal. the portion of the electrical
`signal due to shunted light is preferably less than 10% and
`more preferably less than 1% of the signal value.
`The layer may be made substantially opaque through
`coloring. One such color would be a grey createad by
`FIG. 9 shows another embodiment of a sensor according
`suspension ofmrbon black particles in the base material of 30 to the present
`invention mounted on a finger 90. TWO
`portions of a first layer. 91. 91' have the emitter 92 and
`the layer. ‘This would be substantially opaque to both red and
`infrared.
`detector 93. respectively. attached to them. A break between
`layers 91 and 91'
`is provided in between the ernittr: and
`detector. which will be at the tip of finger 9!. Normally. this
`gap would provide an air gap through which light can be
`shunted between the emitter and detector across the top of
`the finger. However. by using a backing layer 94. with an
`adhesive in the portion between layers 91 and 91'. this layer
`so can stick to the tip of finger 9!. removing the air gap and
`thus substantially preventing shunting between the layers.
`An alternate embodiment is shown in FIG. 10. with the
`finger 100 having a sensor with layers 91 and 91' and emitter
`92 and detector 93 as in FIG. 9. Here. however. a separate
`layer 94 is provided with a foam or other resilient or
`compressible pad 96 mounted on layer 94 between layers 91
`and 91'. This material will compress against the tip of the
`finger. thus also blocking the air gap and preventing the
`40 shunting of light if the matcaial is made of a substantially
`opaque material. such as a color that is substantially opaque
`to the wavelengths of interest (e.g.. red and infrared}. or is
`made of woven material or other material opaque to the
`45 '53“
`FIG. 11 is another embodiment of the present invention
`showing a layer 110 having an emitter 11.2 and a detector 114
`mounted thereon. A covering. transparent layer 116 provides
`a covering and a window for the transmission and detection
`50 of light. Shunting of light is prevented by crimping the
`layers with a metal or other critnp 118. 120. The metal or
`other material is substantially opaque to the shunted light of
`the wavelengths of interest. and completely penetrates the
`layer. or substantially penetrates the layer.
`FIG. 12 shows an alternate embodiment in which a layer
`121 has an emitter 122 and a detector 124 (both shown in
`phantom) mounted thereon. Over the emitter area is a first
`transparent layer 126. with a second transparent layer 128
`over the detector 124. As can be seen. the two layers are
`60 overlapping. with the end 129 of layer 128 being on top of
`layer 126. Thus. instead of an air gap. any shunted light from
`layer 128 is deflected to be above layer 126. and vice versa.
`Alternately. since the light will originate from the emitter. it
`may be more preferable to have the layer overlaying die
`65 emitter be on top of the layer overlaying the detector. In the
`overlapping portion. a radiation blocking layer may be
`included. such as a colorded adhesive.
`
`FIG. 7 illustrates a layer 70 having an emitter 72 and
`detector 74. covered by another layer 76. Layer 76 may be
`partially transparent for light to exit from emitter 72 and
`re-enter to detector 74. Layer 76 has a thinned portion 78.
`and layer 70 has a corresponding thinned portion 79. ‘These
`portions make the layers thin in that area. thus limiting the
`amount of light that may be shunted. The layer oould be
`made thin by a number of techniques. such as embossing.
`welding or beat sealing. The width of the thinned area oould
`be varied. and the shape could be varied as desired. For
`instance. the thinned area oould extend around the sides of
`the crnitta and detector. to prevent shunting of light from the
`edges of the layers when they are wrapped around a finger.
`The thinness of the layer contributes to absorption of the
`light because light which is travelling in a thin layer will
`more often bounce off the layer boundaries than it would in
`a thick layer. This provides more chances to escape the layer
`and be lost or absorbed in an adjoining layer with absorption
`charaotc:ri.stics.
`
`The thickness is preferably less than 0.25 mm and more
`preferably no more than 0.025 mm. The length of the thin
`section is preferably greater than 1 mm and more preferably
`greater than 3 mm.
`
`The thin layer approach could be applied to a remanu-
`facture or other modification of a sensor which involves
`
`adding a layer over the emitter and detector. The entire layer
`could be made thin. preferably less than 0.25 mm. more
`
`55
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`0010
`
`0010
`
`

`
`5.797.841
`
`7
`FIG. 13 shows an alternate embodiment of the present
`invention in which a flexible circuit is printed onto a layer
`130. As shown. emitter 132 and detector 134 are mou nted on
`the flexible layer 130. A covering layer 133 is provided.
`Layers 130 and 133 may be partially or substantially opaque
`to prevent the shunting of light. In between the layers. metal
`traces 136 and 138 can be used to block the shunting of light.
`Instead of making these traces run lengthwise. leaving a
`clear path between the emitter and detector. they instead
`follow a tortuous path. This tortuous path not only goes
`lengthwise. but also goes across the width of the layer 130.
`thus providing a barrier to block shunting the light between
`the emitter and detector.
`FIG. 14 shows anothe: embodiment of the present inven-
`tion for modifying a sheath such as sheath 32 ofF1G. 2. FIG.
`14 shows a sheath 140 having a first. adhesive layer 142. and
`a second layer 144 being transparent and forming a pocket
`for the insertion of a sensor. Layer 144 has opaque colored
`rings 146 and 148 surrounding windows 14? and 149.
`respectively. These windows allow the transmission of light
`to and from the emitter and detector. while the opaque rings
`prevent the shunting of light through transparent layer 144.
`Altcrnately. more or less of the transparent layer 144 could
`be colored with an opaque color to prevent the shunting of
`light.
`Alternately. in the embodiment of FIG. 14. windows 14?
`and 149 could be one color. while areas 146 and 143. which
`may extend over the rest of the layer 144. could be of a
`second color. The second color would be chosen to prevent
`shunting. while the first color would be chosen to allow the
`transmission of light while also being of a color which is
`compatible with the calibration data for an oximeter sensor.
`If the color over the emitter and detector is not chosen
`properly.
`it may interfere with the choice of a proper
`calibration curve in the cximeter sensor for the particular
`wavelength of the emitter being used. Typically. LEDs of
`slightly varying wavelengths are used. with a coding resistor
`indicating the exact wavelength. The coding resistor is used
`to choose a particular calibration ctn've of coelficients in the
`oximeter sensor. Thus. by using a ditfaentially-colored
`sheath or reinforcing laminate or other layer. with the layer
`near the emitter and detector chosen to be white. clear or
`other color which does not interfere with the calibration.
`shunting can be prevented while allowing the sensor to be
`used without alfccting its standard calibration. Preferably.
`the regions over the emitter and detector have a radius
`extending at least 2 mm. beyond the borders of the emitter
`and detector. and preferably at
`least 5 mm beyond the
`borders of the emitter and detector.
`
`Any of the shunt barriers described above could be
`incorporated into layer 144 of sheath 140 of FIG. 14.
`Altcrnately. or in addition.
`the shunt barriers could be
`incorporated into a lamination or other layer placed over a
`sensor in a modifying process. Such a modifying process
`may. for instance. place a non—adhesive layer over an adhe-
`sive layer to convert a disposable sensor into a reusable
`sensor. The shunt barriers described above may also be in an
`original layer in a sensor. or in a replacement layer added in
`a remanufacturing process for recycling disposable sensors.
`As will be understood by those of skill in the art. the
`present invention may be embodied in other specific forms
`without departing from the spirit or essential characteristics
`thereof. Accordingly. the foregoing description is intended
`to be illustrative. but not limiting. of the scope of the
`invention which is set forth in the following claims.
`
`I5
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`25
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`45
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`S5
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`What is claimed is:
`1. A sensor comprising:
`at least one emitter;
`a detector;
`
`a covering layer having :1 hrs! portion over the etnitter and
`a second portion over the detector‘.
`a shunt barrier positioned between said first and second
`portions of said covering layer to substantially block
`radiation of the wavelengths emitted by said emitter.
`such that less than 10% of the radiation detected by said
`detector is shunted radiation:
`wherein there is a break between said first and second
`portions of said covering layer. said shunt barrier
`comprising an underlying layer bridging said break and
`having an adhesive surface.
`2. The sensor of claim 1 wherein said shunt barrier blocks
`said shunted radiation such that less than 1% of the radiation
`detected by said detector is shunted radiation.
`3. ‘The sensor of claim 1 wherein said radiation comprises
`a first wavelength spectrtrm in the red wavelength range and
`a second wavelength spectrlrm in the infrared range.
`4. ‘me sensor of claim 1 wherein said sensor is a pulse
`oximeter sensor.
`
`5. Amodifted pulse oximeter sensor. having at least one
`new layer. comprising:
`a red wavelength spectrum emitter and an infrared wave-
`length spectrum ernitter;
`a detector;
`
`at new layer having a that portion over said emitters and
`a second portion over the detector;
`a shunt barrier positioned between said first and second
`portions of said new layer to substantially block radia-
`tion of the wavelengths emitted by said emitters. such
`that
`less than 5% of the radiation detected by said
`detector is shunted radiation:
`
`wherein said new layer is a laminated layer.
`6. The modified sensor of claim 5 wherein said new layer
`replaces a layer on an unmodified sensor.
`7. The modified sensor of claim 5 wherein said new layer
`is an additional layer added to said sensor.
`8. The modified senm of claim 5 wherein said shunt
`barrier blocks said shunted radiation such that less than 1%
`of the radiation detected by said detector is shunted radia-
`tion.
`
`9. A modified pulse oximeter sensor. having at least one
`new layer. comprising:
`a red wavelength spectrum em.itter and an infiared wave-
`length spectrtnn emitter;
`a detector:
`
`a new layer having a first portion over said emitters and
`a second portion over the detector;
`a shunt barrier positioned between said first and second
`portions of said new layer to substantially block radia-
`tion of the wavelengths emitted by said emitters. such
`that less than 5% of the radiation detected by said
`detector is shunted radiation;
`wherein there is a break between said first and second
`portions of said new layer. said shunt barrier compris-
`ing an underlying layer bridging said brealr and having
`an adhesive surface.
`
`3
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`3
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`$
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`-t
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`*
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`0011
`
`0011