a2, United States Patent
`US 6,580,086 B1
`(10) Patent No.:
`Jun. 17, 2003
`(45) Date of Patent:
`Schulz et al.
`
`US006580086B1
`
`(54) SHIELDED OPTICAL PROBE AND METHOD
`
`(75)
`
`Inventors: Christian E. Schulz, Rancho Santa
`Margarita; Eugene E. Mason, La
`Mirada; AmmarAIAli, Tustin, all of
`CA (US)
`
`(73) Assignee: Masimo Corporation, Irvine, CA (US)
`
`(*) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`US.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/420,544
`
`(22)
`
`Filed:
`
`Oct. 19, 1999
`
`(60)
`
`Related U.S. Application Data
`Provisional application No. 60/150,922, filed on Aug. 26,
`1999,
`
`(SL) Ute C0 eee eecessesscsseeseesseseeneeneeneens G06K 15/00
`?
`?
`52) US. Ch oo 250/557; 250/461.2; 128/633
`(58) Field of Search ......0... cee 250/557, 227.14,
`250/221, 214.1, 573, 461.2, 338.5, 239;
`356/41, 39; 128/633, 665-667
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`........ 128/633
`4,685,464 A
`8/1987 Goldbergeret al.
`5,247,931 A
`9/1993 Norwood......
`w. 128/633
`5,313,940 A
`5/1994 Fuseet al.
`.. 128/633
`« 128/633
`.
`.........
`5,438,986 A
`8/1995 Disch et al.
`+. 128/633
`5,490,523 A *
`2/1996 Isaacsonetal.
`5,939,609 A
`8/1999 Knapp et al.
`-.sseseessseee- 73/101
`FOREIGN PATENT DOCUMENTS
`
`....
`
`Ep
`EP
`EP
`EP
`JP
`JP
`
`262 779
`481 612
`745 348
`0 832598 A2
`02017462
`10314149
`
`4/1988
`10/1990
`12/1996
`4/1998
`1/1990
`12/1998
`
`JP
`JP
`wo
`
`2/1999
`11053662
`7/1999
`11185193
`7/1997
`97/23159
`OTHER PUBLICATIONS
`
`“Pulse Oximeter 3 and 3,” Minolta, hitp://www.minoltausa-
`.com/eprise/main/MinoltaUSA/MUSAContent/ISD/De-
`tailPage?canam, 1 page downloaded and printed from the
`World Wide Web on Aug. 7, 2002.
`“PULSOX Sensors,” Minolta, http://www.pulsoxminolta.ch/
`probeslhim, 4 pages downloaded and printed from the World
`Wide Web on Aug. 7, 2002.
`
`* cited by examiner
`
`Primary Examiner—Que T. Le
`(74) Attorney, Agent, or Firm—Knobbe, Martens, Olson &
`Bear, LLP
`
`(57)
`
`ABSTRACT
`
`An optical probe, which is particularly suited to for use in
`Pp
`measurements on tissue material of a
`patient.
`In one
`embodiment, the probe comprises upper and lower housing
`elements incorporating a light energy source and corre-
`sponding detector. The tissue material of the patient
`is
`disposed between the upper and lower housing elements
`such that the light energy emitted by the source passes
`throughthe tissue material to the detector. A plurality of light
`shields are attached to one or both of the housing elements
`to reduce the amount of ambient andreflected light reaching
`the detector. Additionally, various portions of the upper and
`lower housing elements and shields utilize light absorbent
`coloration and/or coatings which further mitigate the effects
`of undesired ambient and reflected light, thereby reducing
`noise generated within the instrument and increasing its
`accuracy. In one embodiment, the light shields are made
`removable from the optical probe,
`thereby facilitating
`replacement. A circuit for monitoring the condition of the
`probe, and indicating when replacement of the probe is
`desirable,
`is also disclosed.
`;
`
`36 Claims, 11 Drawing Sheets
`
`108
`
`102
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`t- 1500
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`108
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`14507
`
`FOO
`15a
`
`APPLE 1067
`Apple v. Masimo
`IPR2022-01291
`
`APPLE 1067
`Apple v. Masimo
`IPR2022-01291
`
`1
`
`

`

`U.S. Patent
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`Jun. 17, 2003
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`Sheet 1 of 11
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`FIG.1A
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`FIG.1B
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`US 6,580,086 B1
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`US 6,580,086 B1
`
`1
`SHIELDED OPTICAL PROBE AND METHOD
`
`This application claims the benefit of earlier filed provi-
`sional patent application Ser. No. 60/150,922,filed Aug. 26,
`1999,
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates to low-noise optical probes
`which maybe used to sense optical energy passed through
`or reflected from a medium to determine the characteristics
`of the medium.
`
`2. Description of the Related Art
`The physical characteristics of a given medium mayoften
`be determined by transmitting electromagnetic or acoustic
`energy through, or reflected energy from, portions of the
`medium. For example, in the context of medical diagnosis,
`light or sound energy may be directed onto a portion of a
`patient’s body, and the fraction of that energy transmitted
`through (or reflected by) the patient’s body measured to
`determine information about the various physical attributes
`of the patient. This type of non-invasive measurementis
`both more comfortable for and less deleterious to the patient
`than invasive techniques, and can generally be performed
`more quickly.
`Non-invasive physiological monitoring of bodily function
`is often required. For example, during surgery, blood oxygen
`saturation (oximetry) is often continuously monitored. Mea-
`surements such as these are often performed with non-
`invasive techniques where assessments are made by mea-
`suring the ratio of incident to transmitted (or reflected) light
`through an accessible part of the body such as a finger or an
`earlobe. A typical
`transmissive non-invasive monitoring
`device includes a light source such as a light-emitting diode
`(LED) placed on one side of the body part, while a photo-
`detector is placed on an opposite side of the body part. Light
`energy generated by the LED is transmitted through the
`tissue, blood, and other portions of the body part, and
`detected by the photodetector on the other side.
`Alternatively, in a reflective device, the detector is placed on
`the same side of the body part as the light source, and the
`amountoflight energy reflected by the body part measured.
`The transmission of optical energy passing through the
`body is strongly dependent on the thickness of the material
`through which the light passes (the optical path length).
`Many portions of a patient’s body are typically soft and
`compressible. For example, a finger comprises a numberof
`components including skin, muscle,tissue, bone, and blood.
`Although the bone is relatively incompressible, the tissue,
`muscle, and skin are easily compressible or deformed with
`pressure applied to the finger, as often occurs when the
`finger is bent. Thus, if optical energy is made incident on a
`patient’s finger, and the patient moves in a manner which
`distorts or compresses the finger,
`the optical properties,
`including optical path length, may change. Since a patient
`generally movesin anerratic fashion, the compression of the
`fingeris erratic and unpredictable. This causes the change in
`optical path length to be erratic, making the absorption of
`incident light energy erratic, and resulting in a measured
`signal which can be difficult to interpret. Similarly, move-
`ment of the patient during a reflective measurement can
`dramatically affect the quality of the signal obtained there-
`from.
`
`In addition to the typical problem of patient movement,
`the presence of unwanted ambient and/or reflected light
`energy interferes with the measurement of the intensity of
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`the light transmitted through or reflected by the body part.
`Optical transmission/reflection systems as described above
`utilize a light energy detector which measures,inter alia, the
`intensity of light transmitted to or reflected from the body
`part being analyzed. Since ambient light incident on the
`detector affects the intensity measurement, noise or error is
`introduced into the measured signal by such ambientlight.
`Similarly,
`light generated by the light source within the
`measuring device (typically, an LED) which is not trans-
`mitted through or reflected by the body part under exami-
`nation will also result in signal error if such light is received
`by the detector. These “secondary” reflections arise when
`light emitted by the light source is reflected by structures
`within the optical probe onto the detector. Accordingly, to
`increase the accuracy of the measurement process, both
`ambient light and “secondary” reflections from the light
`source should be mitigated.
`FIG. 1a illustrates an ideal signal waveform obtained
`from an optical probe system. FIG. 1b illustrates an actual
`spectra obtained from a typical optical probes not corrected
`for the effects of patient motion or ambient/reflected light.
`Note the significant increase in noise (and resulting loss of
`signal clarity) in FIG. 1b due to these effects.
`Prior optical probes have successfully addressed the issue
`of ease of use and patient motion during measurement. See,
`for example, U.S. Pat. No. 5,638,818 entitled “Low Noise
`Optical Probe,” assigned to the Applicant herein, which
`discloses a system utilizing a chamber whichisolates that
`portion of the patient’s tissue under examination from
`compression or movement by the patient. The device is
`attached to the finger of a patient,
`thereby readily and
`accurately positioning the tissue of the patient’s finger over
`the chamber.
`
`However, attempts at limiting the effects of ambient and
`“secondary” reflected light have been less successful, not
`due to their ineffectiveness, but rather due to their obtru-
`siveness and relative complexity of use. A need exists,
`especially in the health care context, for a simple, fast,
`unobtrusive, and largely error-free means of non-invasive
`measurementof a patient’s physical parameters. Especially
`critical is the attribute that such meansbe easily adapted to
`a variety of different patient types and characteristics with
`little or no adjustment, as is the device disclosed in the
`aforementioned patent. Prior art methods of mitigating
`ambient andreflected light interference have involved cov-
`erings or shrouds which substantially envelop the optical
`probe and tissue, thereby requiring substantial sizing and
`adjustment of the covering for each different patient being
`measured. Another disadvantage of such methodsis that the
`placement of the patient’s appendage (such as a finger) in
`relation to the light source and detector can not be reliably
`verified by the person administering the measurement unless
`the probeis first placed on the appendage, and the covering
`installed thereafter, or alternatively, unless the patient is
`queried. This necessitates additional time and effort on the
`part of the patient and the person making the measurement.
`Anotherfactor relating to the efficacy of an optical probe
`is force distribution on the body partor tissue material being
`measured. Specifically, if force is distributed on the tissue
`material being measured unevenly or disproportionately,
`varying degrees of compression of the tissue may result,
`thereby producing a broader range of optical path lengths in
`the region of the light source and detector. Furthermore,if
`the force that the probe exerts on the tissue material is highly
`localized,
`the ability of the patient
`to move the tissue
`material with respect to the source/detector is enhanced,
`thereby leading to potentially increased noise levels within
`the signal generated by the probe.
`
`13
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`

`

`US 6,580,086 B1
`
`3
`Yet another consideration relating to non-invasive optical
`probe measurement
`involves cost.
`In recent
`times,
`the
`demandhasincreased significantly for both disposable and
`reusable optical probes which are suitably constructed to
`provide accurate, low-noise measurements. The aforemen-
`tioned prior art methods of attenuating ambientand reflected
`light employing coverings or shrouds carry with them a
`significant cost, especially if the probe (or components
`thereof) must be replaced on a frequent basis. Therefore, in
`many applications, it would be useful to have a low-cost
`reusable optical probe capable of attenuating ambient and
`reflected light, with only the degradable components being
`easily and cost-effectively replaced as required, without
`necessitating the replacementof the entire probe. Similarly,
`it would be useful to have a disposable probe capable of
`attenuating ambient and reflected light, which could be
`routinely replaced in its entirety a cost-effective manner.
`Finally, existing optical probes do not include an easy to
`use and reliable means for determining whento replace the
`probe. At present, the probe operator or health care provider
`must keep a record or log of the date of installation of a
`given probe, and replace it at a given periodicity or simply
`replace the probe when it seems worn out. This approach is
`problematic, however, not only from the standpoint of
`additional
`time and effort consumed in maintaining the
`record, but more significantly from the perspective that the
`measurementof installed time is not necessarily represen-
`tative of the wear on the probe. For example, two probes
`installed on the same date may experience significantly
`different levels of wear, depending on the level of use.
`Alternatively, the operator could keep a log of usage, but this
`is too burdensome and time consuming.
`Based on the foregoing, a need exists for an improved
`low-noise optical probe which (i) is simple in design and
`easy to use undera variety ofdifferent operating conditions;
`(ii) is capable of attenuating ambient and reflected light
`without necessitating probe adjustment or fitting to each
`different patient; (iii) is capable of alerting the operator when
`replacement is required; and (iv) is cost effective. Such an
`improved probe would also ideally shield against noise
`caused by electromagnetic interference (EMI).
`
`SUMMARYOF THE INVENTION
`
`The present invention satisfies the foregoing needs by
`providing an improved optical probe for use in non-invasive
`energy absorption or reflection measurements, as well as a
`method of using the same.
`In a first aspect of the invention, an improved shielded
`optical probe assembly is disclosed which incorporates a
`light energy source and light energy detector embedded
`within a multi-part housing adapted to receive and clamp
`onto tissue material from the patient. When the probe is
`operating,
`light energy is directed from the light energy
`source through a first aperture formed within a first element
`of the housing and onto the tissue material of the patient,
`whichis received within the probe. A portion of this lightis
`transmitted through (or reflected from) the tissue material
`onto the detector via a second aperture. In this fashion, a
`light generated by the light source and transmitted through
`or reflected from the tissue material at a localized point is
`received by the detector. A light shield is fitted to the housing
`so as to partially surround the tissue material when it is
`received within the housing, thereby attenuating ambient
`light incident on the optical probe. In one embodiment, the
`light shield is made removable in order to facilitate its
`replacement after degradation and wear. Additionally, por-
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`tions of the shield and housing are colored and/or coated
`such that light incident on these portions is absorbed or
`attenuated. The foregoing light attenuation features act to
`reduce the effects of noise induced within the detector (and
`associated processing circuitry) due to light energy not
`transmitted directly through or reflected from the tissue
`material from the light source. The probe is also optionally
`fitted with a diffraction grating and Faraday shield to miti-
`gate the effects of unwanted optical modes and electromag-
`netic interference on probe accuracy.
`In a second aspect of the invention, the foregoing optical
`probe includes a mechanism for equalizing the force applied
`to the tissue of the patient when the probe is clamped
`thereon. In one embodiment, a series of elongated apertures
`each receive hinge pins which are biased apart by springs
`wound around the axis of the pins. When the housing
`elements of the probe are grasped and compressed together
`by the user, the hinge pins are forced against one edge of the
`elongated apertures, thereby providing a fulcrum for open-
`ing the probe. After the probe is opened, and the patient’s
`finger inserted, the compressing force is removed, thereby
`allowing the housing elements to clamp onto the finger. As
`the compression force is removed, the spring bias allows the
`previously compressed ends of the housing elements apart,
`and urging the pins to the opposite edge of the elongated
`apertures, and “leveling” the housing elements into a more
`parallel orientation. This parallel orientation distributes
`force on the patient’s finger more evenly.
`In a third aspect of the invention, a monitoring device is
`disclosed whichis integrated with the optical probe circuitry
`in orderto assist the operator in determining whento replace
`the probe. In one embodiment, the monitoring device is a
`counter which counts the numberofelectrical pulses gen-
`erated by the detector circuitry, and correlates this number to
`the time of actual probe operation and percent of useful
`lifetime. A light emitting diode visible on the exterior of the
`probe is used to alert the operator to the need for probe
`replacement.
`In another aspect of the invention, a method of measuring
`the amount of light transmitted or reflected by the tissue
`material of a patient using the aforementioned optical probe
`is disclosed. In one embodiment of the method, the tissue
`material is inserted into the shielded probe housing,andlight
`generated by the light source of the probeis transmitted via
`the first aperture into the tissue material. Light energy
`transmitted (or reflected) by the tissue material
`is then
`detected by the detector via the second aperture, and a signal
`relating to the intensity of the detector generated. Ambient
`light incident on the probe, and light generated by the light
`source and scattered off components other than the tissue
`material, are attenuated or absorbed by the shield and
`absorptive coating(s) during detection and signal generation
`in order to reduce any noise component associated there-
`with. The operating time of the probe is also counted in order
`to monitor probe remaining lifetime.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1a illustrates an ideal optical transmittance signal
`that would be measured by a typical prior art optical probe
`when utilized for blood oximetry.
`FIG. 1b illustrates a non-ideal optical transmittance signal
`measured by a typical prior art optical probe when utilized
`for blood oximetry.
`FIG. 2 is an exploded perspective view of a first embodi-
`ment of the optical probe of the present invention, config-
`ured to measure optical transmission.
`
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`

`US 6,580,086 B1
`
`5
`FIG. 2a is a perspective view of the optical probe of FIG.
`2 when assembled.
`
`FIG. 2b is a perspective view of an upper support surface
`element of the optical probe of the present invention with a
`nonreflecting portion depicted with shading.
`FIG. 2c is a perspective view of the lower support surface
`element shown in FIG. 2 with a nonreflecting portion
`depicted with shading.
`FIG. 3 is a cross-sectional view of the optical probe of
`FIG. 2 when assembled, taken along line 3—3 thereof.
`FIG. 4 is a cross-sectional view of the optical probe of
`FIG. 2 when assembled, taken along line 44 thereof.
`FIG. 5 is a perspective view of the detector shield of the
`present invention, shown during assembly.
`FIG. 6 a perspective view of a second embodimentof the
`optical probe of the present invention configured to measure
`optical transmission.
`FIG. 6a is a detail plan view of the removable shield
`elements and channels of the optical probe of FIG. 6.
`FIG. 7 is a cross-sectional view of a third embodiment of
`the optical probe of the present invention configured to
`measure optical reflectance.
`FIG. 8 is a block diagram illustrating one embodimentof
`a monitoring device circuit according to the present inven-
`tion.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`The invention is described in detail below with reference
`
`to the figures, wherein like elements are referenced with like
`numerals throughout.
`It is noted that the term “tissue material” as used herein
`includes, without
`limitation,
`the skin,
`tissue, blood,
`cartilage, ligaments, tendons, muscle, or bone of a given
`portion of a patient’s body, such as the distal end ofa finger,
`or any portion thereof.
`The term “light energy” as used herein refers to any type
`of electromagnetic radiation or energy, whether comprised
`of a narrow, discrete frequency or multiple frequencies.
`Examples of light energy include visible light,
`infrared
`radiation, and ultraviolet radiation. While described as an
`“optical” probe,
`the invention disclosed herein may also
`feasibly be used in conjunction with other forms of energy
`or radiation, whether optically visible or not.
`As shown in FIGS. 2 and 3, a first embodiment of the
`improved optical probe of the present invention is described.
`As shown in FIGS. 2 and 3, the present embodimentof the
`probe 100 generally comprises a two-piece housing 102, a
`light energy source 103, and a light energy detector 105, and
`an electrical supply and signal cable 107. The housing 102
`consists of a first (upper) housing element 104 and a second
`(lower) housing element 106, which are rotatably attached to
`one another via a pivot element 108. The light source 103 is
`disposed within the upper housing element 104, while the
`detector is disposed within the lower housing element 106.
`The housing 102 of the present embodiment is adapted to
`receive the distal end of a finger 112 as shownin FIG. 3, with
`the “upper” housing element 104 engaging the upper surface
`113 of the finger 112, and the “lower” housing element 106
`engaging the lower surface 118 of the finger 112. It will be
`recognized, however, that the probe 100 may be used in any
`orientation, such as with the first housing element 104 being
`located below the second housing element 106.
`Furthermore,
`the light source 103 may alternatively be
`placed in the lower housing element 106, and the detector in
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`the upper housing element 104 if desired, subject to modi-
`fication of other probe components as described further
`below. It is also noted that while the following discussion
`describes a series of exemplary embodiments based on
`measuring the optical characteristics of a finger 112, the
`present invention may be adapted for use with any number
`of other body parts, such as earlobes or loose skin, with
`equal success. Hence, the specific embodiments described
`herein are merely illustrative of the broader invention.
`The first and second housing elements 104, 106 of the
`probe 100 of FIGS. 2 and 3 are generally rectangular in
`form, with the pivot element 108 being disposed near a
`common end 109 of each of the elongate housing elements
`104, 106. The housing elements 104, 106 are in the present
`embodiment formed from an opaque plastic using an injec-
`tion molding process of the type well knownin the polymer
`sciences, although other materials and formation techniques
`may be used. The first housing element 104 includes a
`monitoring light emitting diode (LED) 426 visible to the
`operator, as is described in greater detail below with respect
`to FIG. 8. The first and second housing elements 104, 106
`further each include support surface elements 114, 116, and
`one or more pairs of vertical risers 110a-110d with pin
`apertures 111a, 1114, the latter which are used to form the
`basis of the pivot element 108. The two housing elements
`104, 106 are biased around the rotational axis 123 of the
`pivot element 108 by a biasing element, in this case a hinge
`spring 133 as described further below.
`As shownin FIG. 2, the pivot element 108 of the present
`embodiment comprises a hinge, and includes the aforemen-
`tionedvertical risers 110a—110d, two hinge pins 125a, 1255,
`and biasing spring 133 located along the central axis 123 of
`the hinge pins 125a, 125b. The hinge pins 125a, 125b each
`include an outward retaining element 127,and are of a “split
`pin” design such that a ridge 141 located on the distal end
`144 of each pin 125 engages a corresponding edge 143 of the
`respective interior vertical riser 110c, 110d of the upper
`housing element 104 when each pin 125 is fully received
`within the probe 100, as shown in FIG. 4. This arrangement,
`specifically the ridges 141 of the pins 125 engaging the
`edges 143 of their respective vertical risers 110 under an
`outward biasing force generated by the split in the pin,
`permits the pins 125 to be readily “snapped” into the
`apertures 111 within the vertical risers 110, thereby forming
`a hinge with pivotor rotational axis for the upper and lower
`housing elements 104, 106. The biasing spring 133 fits
`around the pins 125a, 125b as shownin FIG. 4, the two free
`ends 145a, and the connecting section 1456 being received
`with respective holders 146a, 146b formed within the inte-
`rior surfaces of the upper and lower housing elements 104,
`106, respectively. Using this arrangement, the biasing spring
`133 is preloaded (i.e., partially wound) so as to bias the
`upper housing element 104 against the lower housing ele-
`ment 106. A pair of finger recesses 150a, 1505 are formed
`within the outward portion of each of the housing elements
`104, 106, at a location between the common end 109 of each
`housing element and the pivot axis 123, thereby permitting
`the user to grasp the probe 100 between his or her fingers
`using the recesses 150a, 1505 and separate the probe hous-
`ing elements 104, 106 by applying force counter to the
`spring biasing force. In this fashion, the user simply grasps
`the probe 100, opens it by applying a light force with the
`grasping fingers, and inserts the distal end of the patient’s
`finger 112 into the opened end 154 of the probe.
`As depicted in FIG. 2, the pin apertures 111 of the lower
`housing element 106 are somewhat elongated in the vertical
`direction (i.e.,
`in a direction normal to the plane of the
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`US 6,580,086 B1
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`7
`housing element 106). This feature has the practical effect of
`making the upper and lower housing elements 104, 106
`conform morereadily to the shape of the patient’s finger 112
`whenthelatter is received within the probe 100. Specifically,
`the elongated pin apertures allow the portion of the patient’s
`finger 112 inserted into the open end 154 of the probe (FIG.
`3) to act as a fulcrum for a “separating” force generated by
`the biasing springs 133 such that the common ends 109 of
`the upper and lower housing elements 104, 106 are forced
`apart by, inter alia, the bias spring separating force. This
`separating force is generated by the offset 160 of the bias
`spring ends 145a, and connecting section 1455 from the axis
`123 of the spring, as shown in FIG. 3. When the user grasps
`the recesses 150 of the housing elements 104, 106 and
`squeezes, the pins 125 are forced to the fully compressed
`position within the elongated pin apertures 111; that is, the
`pins are forced against the bottom edge of the elongated
`apertures 111 in order to allow the probe 100 to be opened.
`However, once the finger 112 is inserted into the probe, the
`disproportionate compression of the finger 112 (due to the
`interaction of the angled housing elements 104, 106 and the
`substantially cylindrical finger 112) and the aforementioned
`bias spring separating force, act to force the common end
`109 of the probe housing elements 104, 106 apart, thereby
`making upper and lower housing elements 104, 106 more
`parallel to each other as shownin FIG. 3. This “dislocation”
`of the upper element 104 with respect to the lower element
`106 allows moreof the surface area of the upper and lower
`support surface elements 114, 116 (described below) to
`contact the finger 112, and for more even pressure distribu-
`tion thereon.
`
`As previously discussed, the housing elements 104, 106
`are adapted to receive first (upper) and second (lower)
`support surface elements 114, 116, respectively, which pro-
`vide support and alignment for the tissue material, such as
`the finger 112 shown in FIG. 3, when the probe 100 is
`clamped thereon. When assembled as in FIGS. 2a and 3, the
`housing elements 104, 106 and support surface elements
`114, 116 form interior cavities 115a, 1155 within the upper
`and lower housing elements 104, 106, respectively, which
`contain, inter alia, the light source 103 and photodetector
`105 as described in greater detail below. The upper support
`surface element 114 is fashioned from a substantially pliable
`polymer such as silicone rubber, so as to permit some
`deformation of the element 114 when in contact with the
`
`fairly rigid upper portion 113 ofthe patient’s finger 112. In
`one embodiment, the upper element 114 is constructed as a
`membrane of polymer. The lower surface element 116 is
`fashioned from a substantially solid and rigid (i.e., higher
`durometer) polymer. This harder, solid polymeris used for
`the lower surface element 116 since the lower portion of the
`finger 112 is generally more fleshy and deformable, thereby
`allowing the skin and tissue material thereof to deform and
`contour to the shape of the inner region 122 of the lower
`surface element.
`
`The upper and lower surface elements 114, 116 also
`include first and second apertures 117, 119, respectively,
`which communicate with the patient’s tissue material when
`the finger 112 is inserted in the probe 100. The apertures
`allow for light energy to be transmitted between the light
`source 103 and tissue material, and similarly between the
`tissue material and detector 105. The first aperture 117 is
`also axially located with the second aperture 119 in the
`vertical dimension, such that when the probe 100 is in the
`closed configuration with the patient’s finger 112 disposed
`between the upper and lower surface support elements 114,
`116, light emitted by the light source 103 throughthe first
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`aperture 117 is transmitted through the finger 112 and the
`second aperture 119 and received by the detector 105.
`Hence,
`the light source 103, first aperture 117, second
`aperture 119, and detector 105 are substantially axial in this
`configuration.
`The lower support element 116 is further provided with a
`positioning element 196 disposed nearthe pivot element 108
`and common end 109 of the probe 100, as shown in FIGS.
`2 and 3. The positioning element 196 is oriented vertically
`with respect to the lower support element 116 so as to stop
`the distal end of the patient’s finger from being inserted into
`the probe past a certain point, thereby facilitating proper
`alignmentof the finger 112 within the probe 100, especially
`with respect to the source and detector apertures 117, 119.
`While the present embodiment uses a semi-circular tab as
`the positioning element 196,it will be recognized that other
`configurations and locations of the element 196 may be
`used. For example, the tab could be bifurcated with a portion
`being located on the upper support surface element 114, and
`a portion on the lower support surface element 116.
`Alternatively, the positioning element could be in the form
`of a tapered collar which receives, aligns, and restrains only
`the distal portion of the patient’s finger. Many suchalter-
`native embodimentsof the positioning elementare possible,
`and considered to be within the scope of the present inven-
`tion.
`
`As further described below, the lower surface element 116
`optionally includes a chamber 126 coincident with the
`second aperture 119 to assist in mitigating the effects of
`patient movement during light transmission or reflection.
`Thestructure of such chambersis described in detail in U.S.
`Pat. No. 5,638,818, entitled “Low Noise Optical Probe”,
`which is incorporated herein by reference. In general, the
`chamber 126 acts to isolate a portion of the tissue material
`directly over the chamber 126 and aperture 119, thereby
`reducing compression of that tissue during mov