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`US 20050209516At
`
`tates
`
`(19] United S
`{12} Patent Application Publication (10) Pub. N0.: US 2005/0209516 A1
`(43) Pub. Date:
`lt‘raden
`Sep. 22, 2005
`
`(54} VITAL SIGNS
`
`PROBE
`
`(70]
`
`Inventor:
`
`.ltleo
`
`IJ Fradcn, J a Jolla, CA (US)
`
`Correspondence
`Jacob Fraden
`Suite M
`6266 Ferris Sq.
`San Diego, CA
`
`Address:
`
`92121 (US)
`
`Appl. No.:
`
`l0f806,766
`
`Filed:
`
`Mar. 22, 2004
`
`ABSTRACT
`(57]
`Aeornbination of a patient core temperature sensor and the
`dual—wavelength optical sensors in an ear probe or a body
`surface probe improvcsperformanee and allows for accurate
`computation of various vital signs from the photo-plethys-
`mographic signal, such as arterial blood oxygenation (pulse
`oximetry). blond prestaure. and othe rs. Acme body tempera-
`ture is measured by two sensors, where the first contact
`sensor positioned on a resilient ear plug and the second
`sensor is on the external portion of the probe. The ear plug
`changes it's geometry after being inserted into an ear canal
`and compress both the first
`temperature sensor and the
`optical assemny against ear canal walls. "l'he second tern-
`peralure sensor provides a reference signal to a heater that is
`warmed up close to the body core temperature. The heater is
`connected to a common heat equalizer for the temperature
`sensor and the pulse oximeter. Temperature of the heat
`equalizer enhances the tissue perfusion to improve the
`optical sensors response. A pilot light is conducted to the ear
`canal via a Contact illuminator. while a light transparent ear
`plug conducts the reflected lights hack to the light detector.
`
`US. Patent No. 8,923,941
`
`Publication Classification
`
`A611} 5/00
`600/323; 600.549
`
`Apple Inc.
`APLl 006
`
`Apple Inc.
`APL1006
`U.S. Patent No. 8,923,941
`
`001
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`Patent Application Publication Sep. 22, 2005 Sheet 1 of 7
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`am‘.wE
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`current
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`controlfer
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`receiver
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`Patent Application Publication Sep. 22, 2005 Sheet 7 of 7
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`uernperlure
`
`:«I
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`o._
`:IW
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`n.
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`mo
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`K
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`infrared
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`E E1
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`008
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`009
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`[0003] An example of a combined vital signs sensor is
`US. Pat. No. 5,673,692 issued to Schultze et al. where an ear
`infrared temperature sensing assembly (a tynipanic ther-
`mometer) is combined with a blood pulsr: oximeler. While
`an ear is an excellent location for the temperature monitor~
`ing and an infrared probe may be very accurate when used
`intermittently,
`it doesn’t lend itself to a continuous moni-
`toring due to its strong sensitivity to a correct placement,
`motion artifacts, and adverse effects of the ear canal tem—
`perature on the infrared sensing assembly. A device covered
`by US. patent application Ser. No. 091921179 tiled on Aug.
`8, 2001, ofi'ers a better way for a continuous monitoring of
`the body core temperature through the ear canal. It is based
`on a contact (nonuinfraredft method where a temperature
`gradient is measured across the ear canal and the external
`heater brings this gradient to a minimal value. As a result,
`the healer temperature becomes close to that of an internal
`body (core) temperature.
`
`VITAL SIGNS PROBE
`
`FIELD OF INVENTION
`
`[0001] This invention relates to devices for monitoring
`physiological variables of a patient and in particular to a
`device for monitoring arterial pulse oximetry and tempera—
`ture from an ear canal. This invention is based on the
`provisional patent application Ser. Nos. 60/449,113 and
`60/453,192.
`
`DESCRIPTION OF PRIOR ART
`
`[0002] Monitoring of vital signs continuously, rather than
`intermittently is important at various locations of a hospi-
`tal—in the operating, critical care, recovery rooms, pediatric
`departments, general floor. etc. If accuracy is not compro—
`mised, the preference is always given to nonvinvasive meth~
`ods as opposed to invasive. Also, a preference is given to a
`device that can provide multiple types of vital signs instead
`of receiving such information from many individual sensing
`devices attached to the patient. Just a mere packaging of
`various sensors in a single housing typically is not etftcient
`for
`the following reasons: various sensors may require
`difi‘erent body sites, different sensors may interfere with
`each other functionality, a combined packaging may be more
`susceptible to motion and other artifacts and the sin: and
`cost may he prohibiting.
`
`[0004] Concerning other vital signs that potentially can be
`monitored through an ear canal, an arterial pulse oximetry is
`a good candidate as demonstrated by the above mentioned
`patent issued to Schultze et at. Yet, presence of an infrared
`optical system in the ear canal results in extremely high
`motion artifacts during even minimal patient movements.
`Another problem associated with monitoring blood oxygen:
`ation through the ear canal is. a relatively low blood perfu-
`sion of the ear canal lining. A good method of improving
`blood perfusion is to elevate temperature of the oximeter
`sensing device, as exemplified by US. Pat. No. 6,466,808
`issued to Chin et a].
`
`[0005] The degree of oxygen saturation of hemoglobin.
`SpOz, in arterial blood is often a vital index of a medical
`condition of a patient. As blood is pulsed through the lungs
`by the heart action, a certain percentage of the deoxyhcmo—
`globin, Rl-lb, picks up oxygen so as to become oxyherrto-
`globin, Hbog. From the lungs, the blood passes through the
`
`US 2005/0209516 A1
`
`Sep. 22, 2005
`
`arterial system until it reaches the capillaries at which point
`a portion of the HbOl gives up its oxygen to support the life
`processes in adjacent cells.
`
`[0006] By medical definition, the oxygen saturation level
`is the percentage of HbO2 divided by the total hemoglobin.
`'l'herefore,
`
`HM):
`W: =m
`
`[0007] The saturation value is a very important physi-
`ological number. A healthy conscious person will have an
`oxygen saturation of approximately 96 to 98%. Aperson can
`lose consciousness or suffer permanent brain damage if that
`person's oxygen saturation value falls to very low levels for
`extended periods of time. Because of the importance of the
`oxygen saturation value pulse oximetry has been recom-
`mended as a standard of care for every general anesthetic.
`
`[0008] The pulse oximetry works as follows. An oximcter
`determines the saturation value by analyzing the change in
`color of the blood. When radiant energy interacts with a
`liquid, certain wavelengths may be selectively absorbed by
`particles which are dissolved therein. For a given path length
`that the light traverses through the liquid, Beer’s law (the
`Beer-Lambert or Bouguer-Beer relation) indicates that the
`relative reduction in radiation power (PfPo) at
`a given
`wavelength is an inverse logarithmic function of the con-
`centration of the solute in the liquid that absorbs that
`wavelength.
`
`In general, methods for noninvasiver measuring
`[0009]
`oxygen saturation in arterial blood utilize the relative dif-
`ference between the electromagnetic radiation absorption
`coefficient of deoxyhemoglobin, RHb. and that of oxyhe-
`moglnbin, HbOQ. The electromagnetic radiation absorption
`coefficients of RHb and HbO2 are characteristically tied to
`the wavelength ol‘ the electromagnetic radiation traveling
`through them.
`
`[0010] A standard method of monitoring non-invasiver
`oxygen saturation of hemoglobin in the arterial blood is
`based on a ratiometric measurement of absorption of two
`wavelengths of light. On: wavelength is in the infrared
`spectral range (typically from 805 to 940 um) and the other
`is in red (typically between 650 and 750 nm). Other wave
`lengths, for example in the green spectral range, are used
`occasionally as taught by US, Pat, No. 5,830,137 issued to
`Scharf.
`
`In its standard fon'n, pulse oximetry is used in the
`[0011]
`following manner: the infrared and red lights are emitted by
`two light emitting diodes (LEDs) placed at one side of a
`finger clamp or an ear lobe. The signals from each of the
`wavelengths ranges are detected by a photodiode at the
`opposing side of the ear lobe or at the same side of a finger
`clamp after trans—illumination through the living tissue per—
`fused with arterial blood. Separation of the signals from the
`two wavelength bands is performed by alternating the cur—
`rent drive to the respective light emitting diode (time divi~
`sion), and by use of the time windows in the detector
`circuitry or software. Both the static signal, representing the
`intensity of the transmitted light through the finger or car
`
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`Sep. 22, 2005
`
`the PPG wave
`
`[0013] Another important vital sign that needs to be non-
`invasively continuously monitored is arterial blood pressure.
`While a direct blood pressure can be continuously monitored
`by invasive catheters,
`the indirect blood pressure can be
`measured with help of an inflating cuff positioned over a
`limb or finger, or alternatively, by computing blood pressure
`from the pulsatile arterial blood volume. The last method is
`based on a plelhysmography which can be either electro—
`plethysmography (EPG) which measures tissue electrical
`resistance or photo-plethysmography (PPG) which measures
`the tissue optical density. The plethysmography in combi—
`nation with an clectrocardiographic (EKG) wave can yield a
`number that is related to the arterial blood pressure (see for
`example K. Mcr'gns at a}. C(mtimwns Blood Pressure mom'-
`rorr'ng Using Pulse Dainty. Proc. of 23". Annmti EMBS
`International C0an 2001. Oct. 25—23.!5tarttutf). It should be
`noted that PPG and pulse oximetry are based on the same
`type of a sensor—a combination of a light emitting device
`and light sensing device.
`
`lobe and the signal synchronous to the heart beat, i.e., the
`signal component caused by the artery flow, is being moni-
`tored.
`
`[0012] One problem that is associated with use of a pulse
`oximelry sensor on a digit (a finger or toe) or an extremity
`(ear lobe or helix, e.g.) or even on the body surface is a
`sensitivity to patient movements and reflects of ambient light.
`Numerous methods of data processing have been proposed
`to minimize motion artifacts. Yet. obviously the best method
`would he to place a probe at such a body site that is much
`less afiected by the patient movement and is naturally
`shielded from the ambient
`illumination so there will be
`easier to counteract the smaller artifacts. The above men-
`tioned U.S. Pat. No. 5,673,692 describes a pulse oximcter
`sensor installed into an ear canal probe. This indeed is a
`move in a right direction. However, the design has at! optical
`components positioned inside the ear canal and that my not
`lend itself to a practical and oost—cficctive device.
`
`is a goal of this invention to provide a
`it
`[0014] Thus,
`combined sensing assembly for various physiological vari—
`ables that is less sensitive to motion artifacts;
`
`It is another goal of this invention to provide an
`[0015]
`blood pulse oximetry probe suitable for placement inside the
`ear canal;
`
`is also 21 gm] of this invention to provide an
`It
`[0016]
`accurate vital sign probe for the ear canal to provide con—
`tinuous monitoring of pulse oximetry and body core tern“
`peralure;
`
`is also a goal of the invention to provide a
`It
`[0017]
`combined sensing assembly that can collect information on
`blood oxygenation along with body core temperature.
`
`[0018] And another goal of the invention is provide an ear
`probe that can be used for indirect measurement of arterial
`blood pressure.
`
`SUMMARY OF INVENTION
`
`[0019] Aeombination of a patient core temperature sensor
`and the dual~wavelength optical sensors in an ear probe or
`a body surface probe improves performance and allows for
`accurate computation of various vital signs from the photo-
`plethysmographic signal, such as arterial blood oxygenation
`
`(pulse oximetry), blood pressure, and others. A core body
`temperature is measured by two sensors, where the first
`contact sensor positioned on a resilient ear plug and the
`second SCH-SDI is on the external portion of the probe. The ear
`plug changes it’s geometry after being inserted into an ear
`canal and compress both the first temperature sensor and the
`optical assembly against ear canal walls. The second tem-
`perature sensor provides a reference signal to a heater that is
`warmed up close to the body core temperature. The heater is
`connected to a common heat equalizer for the temperature
`sensor and the pulse oximeter. Temperature of the heat
`equalizer enhances the tissue perfusion to improve the
`optical sensors response. A pilot light is conducted to the ear
`canal via a contact illuminator, while a light transparent ear
`plug conducts the reflected lights back to the light detector.
`
`BRIEF DESCRIPTION OF DRAWINGS
`
`[0020] FIG. 1 is a general view of the combined sensing
`assemny with a rigid optical extension positioned inside the
`ear canal
`
`[0021] FIG. 2 shows insertion of the ear plug into the
`sensing head
`
`[0022] FIG.3 is the cut out view of the sensing head with
`the ear plug attached
`
`[0023] FIG. 4 depicts positions of the light emitting
`diodes in a rigid extension
`
`[0024] FIG. 5 is a block diagram of the sensing device
`with thermocouple sensors
`
`[0025] FIG. 6 is a general view of the pulse oximetry
`probe positioned inside the ear canal
`
`[0026] FIG. 7 shows a cut-out view of the probe and the
`ear sensing plug in a disconnected position
`
`[0027] FIG. 8 is a block diagram of the ear canal pulse
`oximeter
`
`[0028] FIG. 9 depicts the cut-out view of the probe with
`an illuminalor permanently attached to the probe
`
`[0029] FIG. 10 is the cut-out view ot‘the sensing assembly
`positioned inside the ear canal
`
`[0030] FIG. 11 is a cross-sectional view of the optical
`sensor with a separated ear plug
`
`[0031] FIG. 12 is a frontal View ofthe optical/temperature
`Sensor
`
`[0032] FIG. 13 is a cross—sectional view of the probe with
`a dual ear plug.
`
`[0033] FIG. 14 shows a combination sensor for skin
`application
`
`[0034] FIG. 15 is a cross-sectional view of the skirt sensor
`with a disposable sensing cup
`
`[0035] FIG. 16 is shows a time dependence of the tem-
`perature detectors
`
`[0036] FIG. 17 depict combination of infrared and red
`PPG waves
`
`[0037] FIG. 18 showa variations in the decaying slope of
`
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`US 20030209516 A1
`
`Sep. 22. 2005
`
`011
`
`[0042] FIG. 1 shows plug 1 attached to ear probe 2. Probe
`2 has a sensing extension 3 that carries blood oximetry
`windows 5. Plug 1
`is fabricated of plaint,
`flexible and
`resilient material. such as silicone. Acomprcssible foam also
`may be used.
`[0043] Before the vital signs monitoring starts, plug I and
`extension 3 are inserted together into ear canal 4. This
`combination of extension 3 and a resilient car plug 1 allows
`for a secure and stable positioning of the optical windows 5
`against ear canal 4 watts. Extension 3 may be either rigid or
`somewhat flexible to accommodate variations of the ear
`canal shapes, while ear piug l
`is acting like a spring
`conforming its own contour to the ear canal shape and
`applying pressure on extension 3. pushing it against the ear
`canal wall. It should be appreciated that plug 1 has some-
`what tiilferent shapes before, during and after insertion into
`the ear canal. Its original shape (before insertion) may have
`many configurations. However, it appears that a shape with
`one or more extended ribs 7 (see also FIG. 2) provides a
`good spring action. WlfldDWS 5 typically consist of three
`windoWS (only two are visible in FIG. 1). Two of them emit
`light rays 14 from first and second windows 32 and 33 and
`one receives reflected rays 15 through a third window 34 as
`in FIG. 2. This assembly contains all components required
`for obtaining the photo-plethysmographic signals for further
`data processing to compute the arterial blood oxygenation.
`arterial pressure, etc.
`
`and 2. Plug I may be plugged into probe 2 as shown in FIG.
`2 where it moves in direction 9 along extension 3 until its
`lower portion 55 is inserted into receptacle 11. Plug 1 may
`have an internal hollow channel 13 that is placed over pin
`12. When temperature sensor 6 is carried by one of the ribs
`7, its two terminal wires are passing through the body of
`plug 1. One wire 10 is shown in FIG. 2. Upon insertion into
`probe 2. wire 10 makes electrical contact with a conductive
`wall of receptacle 11. The other wire (not shown) may be
`positioned inside channel 13 to make electrical contact with
`pin 12. To accommodate for the shape of extension 3, ribs
`7 may have cut—outs 8. Pin 12 may be hollow with bore 45
`passing though the entire probe 2 to the open atmosphere.
`This bore in combination with channel 13 allows for air
`pressure equalization between the ear canal interior and the
`outside.
`
`[0045] FIGJ further illustrates positions of various cont-
`poncnts in probe 2. The left side image is the front view of
`probe 2 without plug 1. while the right side image is a
`cross-sectional view of the assembly with plug I inserted
`into receptacle 1]. Wires 10 and 16 make the respective
`electrical contacts with walls of receptacle [1 and pin 12. In
`turn, receptacle 11 and pin 12 make contacts with circuit
`board 20.
`
`[0046] Wires [0 and 16 may he dissimilar metals Aand I}
`forming first thermocouple junction 24. To improve thermal
`contact with the ear canal 4 walls, the junction is thermally
`connected to an intermediate metal button 30 which may be
`fabricated of brass or other heat conducting material. Wires
`10 and 16 eventually make electrical contacts with the
`printed circuit board 20 that carries the second thermocouple
`junction 21 (also metals A and l?) incorporated into heat
`equalizer 19. One should not be limited with use of the
`thennocouple temperature sensor. Equally effective may be
`the thermistor or any other conventional temperature dctcc-
`tor.
`
`the same type (A in this
`[0047] Note that wires of
`exampie) make electrical connection to electronic compo-
`nents, such as pre-amplificr 25 in FIG. 5. The same heat
`equalizer also carries temperature sensor 22 and, through its
`portion that is a part of extension 3,
`it also carries light
`guides 17 and detector/emitters 18 (only one of each is
`shown in FIG. 3). Heat equalizer 19 is fabricated of metal
`having good thermal conductivity. such a aluminum. copper.
`zinc or other appropriate metal. Light guides 17 are termi-
`nated with windows 5 (only one is shown in FIG. 3). For the
`sanitary purposes. extension 3 and portion of probe 2 may be
`covered with a disposable probe cover 31. The probe cover
`may be fabricated of such material as polypropylene having
`thickness ranging from 0.0005 to 0.010“ and having an
`appropriate conforming shape to envelop components that
`may come in contact with the patient’s tissues.
`
`[0048] First, we describe operation of the temperature
`measurement components. Considering FIGS. 3 and 5 note
`that
`thermocouple junctions 24 and 21 provide electric
`signal that is nearly proportional to a temperature gradient A
`between button 30 and heat equalizer 19. That signal
`is
`amplified by prevamplificr 25 and channeled out of the probe
`via a communication link. for example cable 26. The abso
`lute temperature Tu of heat equalizer 19 is measured by an
`imhedded temperature sensor 22, for example a thermiston
`Thus, temperature sensor 22 also measures temperature of
`
`[0038] FIG. 19 illustrates a combination of EKG and PPG
`waves
`
`[0039] FIG. 20 shows arterial pressure as function of time
`delay.
`
`DESCRIPTION OF PREFERRED
`EMBODIMENTS
`
`invention provides for an optical
`[0040] The present
`photovplethysmographic assembly for an ear canal. The
`assembly can be funhcr supplemented by the deep body
`temperature monitoring components.
`'l‘hese components
`will improve quality of the photo-plethysmographic signals
`received from the optical assembly positioned inside the ear
`canal. A combined sensor has an improved performance as
`compared with the separately used devices. The invention
`solves two major issues related to placing a pulse oximetry
`sensor inside the ear canai. The first
`issue is a secure
`positioning that would minimize motion artifacts. The sec-
`ond issue is an improved blood perfusion of the earl canal
`lining, thus enhancing the detected signal. There are several
`embodiments of the invention. Each embodiment has its
`own advantages and limitations. The most
`important
`embodiments are described in detail below.
`
`[0041]
`
`First Embodiment
`
`To improve functionality of the probe by means of
`[0044]
`a temperature measurement function, plug 1 carries on or
`near its outer surface temperature sensor 6. That sensor is in
`an intimate thermal contact with ear canal 4 walls. Tern—
`peralure sensor 6 may be positioned on extension 3 (not
`shown) near windows 5. In that case, extension 3 should be
`fabricated of a material with low thermal conductivity,
`meaning that it should be thermally decoupled from probe
`2. Alternatively, temperature sensor 6 may he position on
`plug 1 at the opposite side from extension 3 as in FIGS. 1
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`[0051] Extension 3 that carries three windows 32, 33, and
`34 (FIG. 2) provides the photo-plethysmographic sensing
`function. Light guide 17 (FIG. 3) is optically connected to
`detectorslemitlers 18. There are three light guides 17 in
`extension 3 and detectorfemitters 18, but only one is shown
`for clarity. Alternatively, detectoriemitters 18 may be posi—
`tioned next to windows 5 thus eliminating a need for light
`guides 17. Detector/emitters 18 contain one of the following
`(see also FIG. 5):
`first
`light emitting diode (LED) 50
`operating at visible wavelength of about 660 nm, second
`LED 52 operating at near infrared wavelength of about 910
`nm, and light detector 51 covering both of the indicated
`wavelengths. Light guides 17 should be fabricated of mate—
`rial with low absorption in the wavelengths of operation,
`Examples of the materials are glass and polycarbonate resin.
`Windows 32 and 33 preferably should be aimed along axes
`forming an approximate 60° angle to each other (FIG. 4).
`Window 34 {not shown in FIG. 4) should form an angle of
`about 30° to each of them. All these components form an
`optical head of a pulse oximcter.
`It detects the photo—
`plethysmographic waves of the pu tsatile blood at two wave4
`lengths and pass them to module 27 for the signal process-
`mg.
`
`blood perfusion and enhance accuracy. The elevation may be
`few degrees less or more than the oore temperature. There-
`fore. temperature sensor 6 may be absent while heater 23
`and sensor 22 would keep temperature of the assembly
`above ambient and preferably close to the patient’s body, say
`37° C. Signals from a pulse oximeter module 27 and
`temperature controller 28 pass to receiver 29 that may be a
`vital sign monitor or data recorder. Naturally. a communi-
`cation linh that in FIG. 5 is shown as cable 26 can be of
`many conventional designs, such radio, infrared or
`
`[0054] Second Embodiment
`[0055]
`In this embodiment, photons oflight that are modu-
`lated by the pulsatile blood to produce the photo-plethys-
`mographic signals pass through a translucent ear plug. Thus.
`the essential component of this embodiment
`is a light
`transparent ear plug that alm may be used as a carrier of a
`temperature sensor. Contrary to the first embodiment, when
`the optical components WCIE incorporated into extension 3,
`the ability of an ear plug to transmit light allow» to keep
`most of the optical components outside of the ear canal and
`thus simplifies design and use of the device,
`
`[0056] Since the pulse oximetry data and indirect blood
`pressure monitoring can be accomplished from signals that
`are measured by the same optical probe, the same compo—
`nents that are used for the ear pulse oximetry are fully
`applicable for the indirect arterial blood pressure monitoring
`as well.
`
`[0057] The light emitting devices (for example, light emit—
`ting diodes—LED) are positioned inside probe 62 (FIG. 6)
`that is positioned outside of [be patient body, while only ear
`plug 64 is inserted into ear canal 4 of ear 60. llluminator 65
`is adjacent to the entrance of the ear Canal and shielded by
`shield 66 from a direct optical coupling with ear plug 64.
`Thus, light transmission assembly 63 is comprised of illu-
`minator 65, shield 66 and ear plug 64.111uminator 65 and car
`plug 64 should be substantially optically homogeneous and
`transparent in the wavelengths of the lights emitted by the
`LEDS. Yet, they not necessarily need to be fabricated of the
`same material. For example, illuminator 65 may be fabri-
`cated of acrylic resin while car plug 64 may be fabricated of
`clear silicone resin. It may be desirable, however, that the
`illuminator has certain flexibility and pliability for better
`conformation to and coupling with the ear canal entrance.
`Shield 66 may be fabricated of any material that is opaque
`for the used light. Each of these components (illuminator,
`shield and plug) may be either reusable or disposable.
`
`[0058] FIG. 7 illustrates the internal structure of oximetry
`sensor 67 where light transmission assembly 63 is discon—
`nected from probe 62. This ability to disconnect may be
`important for practical use as the entire light transmission
`assembly 63 may be made interchangeable and even (dis
`posablc. The probe 62 internal components are protected
`from the environment by encapsulation 78 and data are
`transmitted via cable 80. However, data may be transmitted
`by other means, for example via radio or optical communi-
`cation links. Intemal circuit board 68 supports holder 76.
`light coupler 72, two LED; 71 and 77, light detector 73 and
`heart rate indicating light 70. Heater 69 may be added to
`warm up the interior of probe 62 and portion of car plug 64
`to temperatures in the range of 37—40” C. which would aid
`in increasing blood perusing in the ear canal and, as a result,
`enhance a magnitude of the detected signal. Positions of the
`
`US 2005/0209516 A1
`
`Sep. 22, 2005
`
`second thermocouple junction 21. The internal core (deep
`body) temperature Tb can be computed from an equ ation that
`accounts for the temperature gradient A.
`r,:r,+(t+,u_m
`
`(2)
`
`[0049] where value of is not constant but is function of
`both Th and To. Its functional relationships shall be deter-
`mined experimentally.
`
`To further improve accuracy, value of :1 should be
`[0050]
`minimized. This can be achieved by adding a heater to heat
`equalizer 19. Prciamplifier’s 25 output signal 40 represent
`ing A and temperature signal 41 from temperature sensor 22
`pass to controller 28 that provides electric power to heater 2.3
`imbedded into heat equalizer 19. Controller 28 regulates
`healer in such a manner as to minimize temperature dilfer-
`ence A, preferably close to zero. Since button 30 that carries
`first
`junction 24 is attached to a wall of ear canal 4,
`temperature of heat equalizer 19 eventually becomes close
`to that of ear canal 4. After some relatively short time (few
`minutes) ear canal walls assume the inner temperature of the
`patient body.
`It
`is important, however that first 24 and
`second 21 thermocouple junctions are thermally separated
`from each other by some media 42 of low thermal conduc-
`tivity. Plug 1 being fabricated of low heat conducting resin,
`for example silicone rubber, acts as such media. Tempera—
`ture '1‘:‘ of heat equalizer 19 becomes close to the patient
`inner body core temperature T',,.
`
`[0052] There are many possible versions of operating
`LEDs 50, 52 and detector 51 and analyzing the photo
`plethysmographic waves that allow computation of the
`oxygen saturation of hemoglobin in arterial blood. ‘l‘hese
`methods are well known in art of pulse oximetry and thus
`not described here. Yet, an important contribution from the
`temperature side of probe 2 is that heat equalizer l9 elevates
`temperature '1', of extension 3 to the level that is close to a
`body core temperature. This increases blood perfusion in the
`ear canal walls that, in turn, improves signal-tn-noise ratio of
`a photo-plethysmographic pulse.
`[0053]
`it should be noted, that just a mere elevation of
`temperature of the pulse oximetry components may improve
`
`012
`
`FITBIT, Ex. 1006
`
`

`

`US 20030209516 A1
`
`Sep. 22, 2005
`
`013
`
`It should be noted that the purpose of illuminatol'
`[0061]
`65, light transmissive ear plug 64 and shield 66 is to separate
`the transmissive and receiving beams of light. Otherwise,
`the transmissive light would spuriously couple directly to
`light detector 73, thus bypassing biological tissue 103. There
`are many possible ways of separating the transmitting and
`receiving beams of light, but all involve the use of a light
`transparent ear plug As an illustration of another possible
`design, FIG. 14 shows duai ear plug 104, consisting of two
`light
`transmitting seclions—lirsl section 108 and second
`section 110. These sections are separated by light stopper
`109 that is not transparent for the used wavelengths of light.
`First and second LEDs (71 and 77) are coupled to first
`section 108, while detector 73 is coupled to second section
`110 by means of the intermediate light conducting rod 106.
`Two 1.130s (71 and 7'7) produce light in form of transmitting
`beam 112 that propagates toward tissue 103 and modulated
`by oxyhemoglobin, The modulated light in form of receiving
`light beam 111 passes toward detector 73. The separation of
`the light beams are performed by light stopper 109 and
`jacket 105 which is also opaque. Naturally, in this case there
`is no need for a separate illuminator as both transmission and
`reception of light is performed by dilTerent sections of the
`ear plug.
`
`light emitting and detecting components may be reversed if
`so desired for a particular design. That is, an “illuminator”
`may contain a detector and the ear plug may be coupled with
`the emitters. 'I‘his arrangement will not change the general
`operation of the device
`
`[0059] Light transmitting assembly 63 may be plugged
`into holder 76 so that butt 85, which is part ofear plug 64,
`comes in proximity with end 74 of light coupler 72. This
`would allow light to pass from the body of ear plug 64 via
`its bull 85 and light coupler 72 toward light detector 73. At
`the same time, illuminator 65 has at its end joint 82 that
`comes in proximity with lens 81 of second LED 77. The
`same is true for first LED 71. Thus, after installation of light
`transmission assembly 63 onto holder 76, both LEDs can
`send light through illuminalor 65. As in many conventional
`pulse oximeters. [.1305 can operate with a time division of
`light transmission to prevent sending two wavelengths at the
`same time. Note that shield 66 prevents light of any wave—
`length from going directly from illuminator 65 toward car
`plug 64. Since ear plug 64 is intended for insertion into an
`ear canal, to aid in this function, hollow bore 33 may be
`formed inside ear plug 64. Similar hole 75 (or other air
`passing channel) is formed in light coupler 72 and other
`components of probe 62 to vent air to the atmosphere. The
`bore and a hole will allow for air pressure equalization when
`car plug is inserted into an ear canal. Alternatively, the bore
`may be replaced with a groove positioned on the exterior of
`ear plug 64 (not shown).
`
`[0060] While FIG. 6 shows ear plug 64 having a smooth
`surface, FIG. 7 shows a variant of ear plug 64 with pro
`truding ribs 84 that are pliable, flexible and resilient. As seen
`in FIG. 10, when car plug 64 is inserted into ear canal 4, ribs
`84 flex and secure the plug inside the ear canal. While ear
`plug 64 may be rigid,
`it
`is more advantageous to have it
`flexible, pliant and resilient, so that it would conform to the
`shape of the ear canal.
`
`[0062] The entire sensing assembly works as folkth (see
`FIG. 10}. First LED 71 emits light that in form of first beam
`
`87 travels through the body of illuminator 65 which comes
`in physical contact 120 with the opening of the ear canal.
`This contact allows light (in form of second beam 88) to
`continue traveling into the biological tissue and be modu-
`lated by the oxyhcmoglobin and pulsatile blood volume. The
`scattered and modulated light (in form of third beam 113)
`enters the body of car plug 64 and propagates toward light
`detector 73 in form of fourth beam 90. The identical process
`is true for the light emitted by second LED 77 when it is
`activated,
`in turn. Both detected signals from the same
`detector 73 are processed in a conventional way to obtain
`inform