111111
`
`1111111111111111111111111111111111111111111111111111111111111111111111111111
`US 20050209516Al
`
`(19) United States
`(12) Patent Application Publication
`Fraden
`
`(10) Pub. No.: US 2005/0209516 Al
`Sep. 22, 2005
`(43) Pub. Date:
`
`(54) VITAL SIGNS PROBE
`
`(76)
`
`Inventor:
`
`.Jacob Fraden, Ja Jolla, CA (US)
`
`Correspondence Add ress:
`J acob Fraden
`Sui te M
`6266 Ferris Sq.
`San Diego, CA 92121 (US)
`
`(21) Appl. No.:
`
`10/806,766
`
`(22) Filed:
`
`Mar. 22, 2004
`
`P ublication C lassification
`
`Int. C l.7 ....................................................... A61B 5/ 00
`(51)
`(52) U.S. C l. . ........................................... 600/323; 600/549
`
`ABSTRACT
`(57)
`A combination of a patient core temperatu re sensor and the
`dual-wavelength optical sensors in an ear probe or a body
`surface probe improves performance and allows for accurate
`computa tion of various vital sig ns from the photo-plethys(cid:173)
`mographic signal, such as arterial blood oxygenation (pulse
`oximetry), blood pressure, and others. A core body tempera(cid:173)
`ture is measured by two sensors, where the fi rst 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 assembly against ear canal walls. T he second tem(cid:173)
`perature sensor provides a reference signal to a heater that is
`warmed up close to the body core temperature. T be beater is
`connected to a common heat equalizer for the temperatu re
`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 v ia a contact illumina tor, while a light transparent ear
`plug cond ucts the reflected lJghts back to the light detector.
`
`----~
`'
`'
`'
`',,
`' ' \
`
`/
`
`/
`
`I
`
`I
`I
`I
`I
`
`,
`
`I
`
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`f
`I
`I
`I
`
`I
`\
`\
`\
`\
`\
`\
`
`'
`'
`
`2
`
`\
`
`/
`
`I
`
`I
`I
`
`I
`
`:::;;...-'
`
`~
`~
`~ :.:::::::
`::=:;::;
`:::::::;
`::=::::::
`
`:::::::: -
`
`15
`
`\
`
`I
`
`I
`
`' .......
`
`' '-
`
`._ - -
`
`/
`
`I
`
`001
`
`Apple Inc.
`APL1028
`U.S. Patent No. 9,289,135
`
`

`

`Patent Application Publication Sep. 22, 2005 Sheet 1 of 7
`
`US 2005/0209516 A1
`
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`1
`
`\
`\
`\
`\
`\
`
`r--.
`
`2
`
`/
`
`I
`
`,.----~
`
`,-......
`,
`
`I
`
`'
`
`'
`
`I
`I
`I
`I
`I
`I
`
`I
`I
`'\
`'-.)
`I
`\
`\
`\
`'
`
`7
`
`'
`
`'
`
`.--"
`1
`I
`
`/
`
`I
`' ·
`I
`'-
`
`I 15
`I
`1
`\
`
`I
`
`'..._
`
`I
`
`~-I
`
`!J:i. 2
`
`002
`
`

`

`Patent Application Publication Sep. 22, 2005 Sheet 2 of 7
`
`US 2005/0209516 Al
`
`32
`
`24
`
`30
`
`2
`
`40,
`
`41,
`
`I I
`
`v
`
`·----
`current
`
`28
`
`29
`
`controller
`
`receiver
`
`!!Jij. 6
`
`003
`
`

`

`Patent Application Publication Sep. 22, 2005 Sheet 3 of 7
`
`US 2005/0209516 Al
`
`-----/4
`' ' / _,
`' .,_,
`
`'
`
`/
`I
`
`\
`I
`
`,'\ ____
`
`'
`
`/--- -~60
`
`-
`
`,
`
`\
`
`\
`
`'
`
`I
`'v 65
`I
`I
`
`-L--- - v=
`
`/
`
`I
`I
`1
`I
`I
`I
`I
`I
`I
`I
`I
`I
`
`70
`
`62
`
`I
`
`' I
`
`I
`I
`\
`' ',
`
`63
`
`l!Jij. 6
`
`I
`
`I
`
`' .....
`
`67
`
`62 /
`
`85
`76
`
`81 82
`
`l!Jij. 7
`
`"-63
`
`004
`
`

`

`Patent Application Publication Sep. 22, 2005 Sheet 4 of 7
`
`US 2005/0209516 Al
`
`4
`
`86
`
`95
`0----f-- -----,
`{-
`96 ~ r----- ----~
`{
`
`~.8
`
`22
`
`21
`
`005
`
`

`

`Patent Application Publication Sep. 22, 2005 Sheet 5 of 7
`
`US 2005/0209516 Al
`
`71
`
`60
`
`~· 10
`
`122
`
`"'120
`
`~.II
`
`006
`
`

`

`Patent Application Publication Sep. 22, 2005 Sheet 6 of 7
`
`US 2005/0209516 Al
`
`68
`
`-= = ~:,:: = =:::
`-· --_.;:.: ::: = ::: : :: :.~ ::: ::;; ::: ::: :::: :·
`-- - ---<;--- --
`- - - - ~,- - - - - - - - -- -- ..
`- - ·- ·- ·-· ·-' ·"'-' -· ·- 00-- -· -H - ~
`:: :::- : ::: ::: :::: ::: :.'34,_:
`-· -· -· .
`- -- .......... - ..... ·- - -·· - ....
`
`112
`
`103
`
`g:;. 12
`
`252
`230
`~.14
`
`220
`
`Yi· i /5
`
`265
`
`I
`I
`I
`I
`215 ~l/214
`
`270
`
`007
`
`

`

`Patent Application Publication Sep. 22, 2005 Sheet 7 of 7
`
`US 2005/0209516 Al
`
`!!!
`:::>
`t::
`Q) c.
`·E
`21----
`
`201
`
`time
`
`207
`
`red~
`YJi. 17
`
`\:::204
`
`YJi. /8
`
`210
`
`~.20
`
`008
`
`

`

`US 2005/0209516 Al
`
`Sep.22,2005
`
`1
`
`VITAL SIGNS PROBE
`
`FIELD OF INVENTION
`
`[0001) This invention relates to devices for moni toring
`physiological variables of a patient and in particular to a
`device fo r mo nitoring arterial pulse oximetry and tempera(cid:173)
`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(cid:173)
`in tbe operating, critical care, recovery rooms, pediatric
`tal-
`depa rt ments, general floor. etc. If accuracy is not compro(cid:173)
`mised, tbe preference is always given to non-invasive meth(cid:173)
`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 efficient
`for the following reasons: various sensors may require
`different body s ites, different sensors may interfere with
`each other functionality, a combined packaging may be more
`susceptible to motion and o ther artifacts and the size and
`cost ma y be prohibiting.
`
`[0003) An example of a combined vital signs sensor is
`U.S. Pat. No. 5,673,692 issued toScbultzc ct al. wbcrc ao car
`infra red temperature sensing assembly (a tympanic ther(cid:173)
`mometer) is combined wi th a blood pulse oximeter. While
`an ear is an excellent location for the temperature monitor(cid:173)
`ing and an infrared probe may be very accurate when used
`intermittently, it doesn' t lend itself to a continuous moni(cid:173)
`toring due to its strong sensitivity to a correct placement,
`motion artifacts, and adverse effects of the ear canal tem(cid:173)
`perature on tbe infrared sensing assembly. A device covered
`by U.S. patent application Ser. No. 09/927,179 fi led o n Aug.
`8, 2001, offers a better way for a continuous monitoring of
`the body core temperature tbrougb the ear canal. It is based
`on a contact (non-infrared) metbod wbere a temperature
`g radient is measured across the ear canal and the external
`heater brings this gradient to a minimal value. As a result,
`ibe beater temperature becomes close to tbat of an internal
`body (co re) temperature.
`
`[0004) Concerning other vita l sig ns that potentially can be
`monitored th rough an ear canal, an arterial pu.lse oxim etry is
`a good candidate as demonstrated by the above men tioned
`patent issued to Schultze et al. 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(cid:173)
`ation through the ear canal is a relatively low blood perfu(cid:173)
`sion of the ear canal lining. A good method of improving
`blood perfusion is to elevate temperature of tbe oximeter
`sensing device, as exemplified by U.S. Pat. No. 6,466,808
`issued to Cbin et al.
`
`[0005) The degree of oxygen saturation of hemoglobin,
`Sp02 , in arterial blood is often a vital index of a medical
`condition of a patient. As blood is pulsed through the lungs
`by tbe heart ac tion, a certain percentage of the deoxybemo(cid:173)
`globin, RHb, picks up oxygen so as to become oxyhemo(cid:173)
`globin, Hb02 • From the lungs, the blood passes th rough the
`
`arterial system until it reaches the capillaries at wbicb point
`a portion of the Hb02 gives up its oxygen to support the life
`processes in adjacent cells.
`
`[0006) By medical definition, the oxygen saturation level
`is tbe percentage of Hb02 divided by tbe total bemoglobin.
`Therefore,
`
`(ll
`
`[0007) The saturation value is a very important pbysi(cid:173)
`ological number. A healthy conscious person will have an
`oxygen saturation of app roximately 96 to 98%. A person can
`lose consciousness or suffer permanent brain damage if that
`person's oxygen saturation val ue fa lls to very low levels for
`extended periods of time. Because of the importance of the
`oxygen saturation value pulse oximetry bas been recom(cid:173)
`mended as a standard of care for every general anestbetic.
`
`[0008] The pulse oximetry works as follows. An oximeter
`determines tbe saturation value by analyzing tbe cbange in
`color of the blood. When radian t energy interacts wit h a
`liquid, certain wavelengths may be selectively absorbed by
`particles which are dissolved tberein. For a g iven patb lengtb
`that the light traverses through the liquid, Beer's law (the
`Beer-Lambert or Bouguer-Beer relation) indicates that the
`relative reduction io rad iation power (P/Po) at a g:ive11
`wavelength is an inverse logarithmic function of the con(cid:173)
`centration of tbe solute in the liquid that absorbs that
`wavelength.
`
`[0009]
`In general, met hods for noninvasively measuring
`oxygen saturation in arterial blood utilize tbe relative dif(cid:173)
`ference between tbe electromagnetic radiation absorption
`coefficient of deoxyhemoglobin, RHb, and tbat of oxybe(cid:173)
`moglobin, Hb02 • The electromagnetic radiation absorption
`coefficients of RHb and Hb02 are cbaracteristically tied to
`the wavelength of the e lectromagnetic radia tion traveling
`through them.
`
`[0010) A standard method of monitoring non-invasively
`oxygen saturation of hemoglobin in the arterial blood is
`based on a ratiometric measurement of absorp tion of two
`wavelengths of light. One wavelength is in the infrared
`spectral range ( typically fro m 805 to 940 nm) and the other
`is in red (typically between 650 and 750 om). Other wave(cid:173)
`lengtbs, for example in tbe green spectral range, are used
`occasionally as taught by U.S. Pat. No. 5,830,137 issued to
`Scharf.
`
`[OOll)
`In its standard fom1, pulse oximetry is used in the
`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 s ide of a finger
`clamp after trans-illumination tbrougb tbe living tissue per(cid:173)
`fused wit b arterial blood. Separation of the signals from the
`two wavelength bands is performed by alternating the cur(cid:173)
`rent drive to the respective light emiuing diode (time divi(cid:173)
`sion), and by use of the time windows in tbe detector
`circuitry o r software. Both the static signal, representing the
`intensity of the transmitted light through the linger or ear
`
`009
`
`

`

`US 2005/0209516 Al
`
`Sep.22,2005
`
`2
`
`lobe and the signal synchronous to the heart beat, i.e., the
`signal component caused by the artery flow, is being moni(cid:173)
`tored.
`[OOU) One problem that is associated with use of a pulse
`oximetry 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 effects of ambient light.
`Numerous methods of data processing have been proposed
`to minimize motion artifacts. Yet, obviously the best method
`would be to place a probe at such a body site that is much
`less affected 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(cid:173)
`tioned U.S. Pat. No. 5,673,692 describes a pulse oximeter
`sensor installed into an ear canal probe. Tllis indeed is a
`move in a right direction. I lowever, the design bas all optical
`components positioned inside the ear canal and tha t my not
`lead itself to a practical and cost-effective device.
`
`[0013] Another important vital sign that needs to be non(cid:173)
`invasivcly 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 o n a plethysmography which can be either electro(cid:173)
`plethysmography (EPG) which measures tissue electrical
`resistance or photo-plethysmography (PPG) which measures
`the tissue optical density. T he plethysmography in combi(cid:173)
`nation with an electrocardiographic (EKG) wave can yield a
`number that is related to the arterial blood pressure (see for
`example K. Meigas eL a!. Continuous Blood Pressure moni(cid:173)
`toring Using Pulse Delay. Proc. of 23rd Annual EMBS
`International Conf 2001, Oct. 25-28, lstanbuf). It s hould be
`noted that PPG and pulse oximetry are based on tbe same
`type of a sensor-a combination of a light emitting device
`and light sensing device.
`[0014) Thus, it is a goal of this invention to provide a
`combined sensing assembly for various physiological vari(cid:173)
`ables that is Jess sensitive to motion artifacts;
`[0015)
`It is another goal of this invention to provide an
`blood pulse oximetry probe suitable for placement inside the
`ear canal;
`[0016]
`II is also a goal of this invention to provide an
`accurate vital sign probe for the ear canal to provide con(cid:173)
`tinuous monitoring of pulse oximetry and body core tem(cid:173)
`perature;
`[0017]
`It is also a goal of the invention to provide a
`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) A combination 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(cid:173)
`plethysmograp hic 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 car 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 assembly against ear canal walls. The second tem(cid:173)
`perature sensor provides a reference signal to a beater that is
`warmed up close to the body core temperature. The beater is
`connected to a common heat equalizer for the temperature
`sensor and tbe 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 tbe reflected ligbts back to the light detector.
`
`BRIEF DESCRIPTION OF DRAWINGS
`
`[0020] FIG. 1 is a general view of the combined sensing
`assembly with a rigid optical extension positioned inside the
`ear canal
`[0021) FIG. 2 shows insertion of the ear plug into tbe
`sensing bead
`[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 b lock 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 tbe probe and the
`ear sensing plug in a disconnected position
`[0027] FIG. 8 is a block diagram of tbe ear canal pulse
`oximete r
`[0028] FIG. 9 depicts the c ut-o ut view of the probe with
`an illuminator permanentl y attached to the probe
`[0029) FIG.10 is the cut-out view of the sensing assembly
`positioned inside the ear canal
`
`[0030] FIG. 11 is a cros.5-sectional view of the optical
`sensor with a separated ear plug
`
`[0031] FIG. L2 is a frontal view of the opticaVtemperature
`sensor
`
`[0032) FIG. 13 is a cros.5-sectional view of tbe 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 skin sensor
`with a disposable sensing c up
`
`[0035) FIG. 16 is shows a time dependence of the tem(cid:173)
`perature detectors
`
`[0036) FIG. 17 depict combination of infTared and red
`PPG waves
`
`[0037) FIG. 18 sbows variations in the decayi ng slope of
`the PPG wave
`
`010
`
`

`

`US 2005/0209516 Al
`
`Sep.22,2005
`
`3
`
`[0038) FIG.19 illustrates a combination of EKG and PPG
`waves
`
`[0039) FIG. 20 shows arterial pressure as function of time
`delay.
`
`DESCIUPTION OF PREFERRED
`EMBODIMENTS
`
`[0040) The present inventio n provides for an oplical
`photo-plethysmographic assembly for an ear canal. The
`assembly can be further supplemented by the deep body
`temperature monitoring components. These components
`wi ll improve quality of the photo-plethysmographic signals
`received from the oplical assembly positioned inside the ear
`canal. A combined sensor bas 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 canal. The first issue is a secure
`positioning that would minimize motion artifacts. T he sec(cid:173)
`ond issue is an improved blood perfusion of the earl canal
`lining, Lhus enhancing the detected signal. There are several
`embodiments of the invention. Each embodiment has its
`own adva ntages and
`limitations . The most
`important
`embodiments are described in detail below.
`
`[0041] First Embodiment
`
`[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 fabrica ted of plaint, flexible and
`resilient material, such as silicone. A compressible foam aLso
`may be used.
`
`[0043) Before the vital signs mo nitoring s tarts, plug 1 and
`extension 3 are inserted toget her into ear canal 4. This
`combination of extension 3 and a resilient ear plug 1 allows
`for a secure and stable positioning of the optical windows 5
`against ear canal 4 walls. Extension 3 may be either rigid or
`somewhat flexible to accommodate variations of the ear
`canal s hapes, while ear plug 1 is acting like a spring
`conforming its own contour to the ear canal s hape and
`applying pressure on extension 3, pushing it against the ear
`canal wall. It should be appreciated that plug 1 bas some(cid:173)
`what different shapes before, during and after insertion into
`the ear canal. Its original s hape (before insertion) may have
`many configurations. However, it appears that a shape with
`ooe o r mo re extended ribs 7 (see also FIG. 2) provides a
`good spring action. Windows 5 typically consist of three
`windows (only two are visible in FIG. I). 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 . Tbis assembly contains all components required
`for obtaining the photo-plethysmographic signals for further
`data processing to compute the arte rial blood oxygenation,
`arterial pressure, etc.
`
`and 2. Plug 1 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 hoUow chan nel 13 that is placed over pin
`12. When temperature sensor 6 is carried by one of the ribs
`7, its two terminal wires arc 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 cbannel13 to make electrical contact with
`pin 12. To accommodate for tbe shape of extension 3 , ribs
`7 may have cut-outs 8. Pin 12 may be ho llow with bore 45
`passing tbougb the entire probe 2 to tbc open atmosphere.
`Tbis bore in combination with channel 13 allows for air
`pressure equalization between the ear canal interior and the
`outs ide.
`
`[0045) FIG. 3 further illustrates positions of va rious com(cid:173)
`ponents 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 1 inserted
`into receptacle 11. Wires 10 and 16 make the respective
`electrical contacts with walls of receptacle 11 and pia 12. In
`turn, receptacle ll and pin 12 make contacts with circuit
`board 20.
`
`[0046] Wires 10 and 16 may be dissimilar metals A and B
`forming first thermocouple junclion 24. To improve thermal
`contact with the ear canal 4 walls, the junction is thermally
`connected to an intermediate me tal bullon 30 which may be
`fabricated of brass or other beat 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 B) incorporated into beat
`equalizer 19. One should not be limited with use of the
`thermocouple temperature sensor. Equally etTective may be
`the thermistor or any other conventional temperature detec(cid:173)
`tor.
`
`[0047) No te tbat wires of the same type (A in this
`example) make electrical connection to electronic compo(cid:173)
`nents, such as pre-amplifier 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
`s hown in FIG. 3). Heat equalizer 19 is fabricated of metal
`having good thermal conductivity, such a aluminum, copper,
`zi nc or o ther appropriate metal. Light guides 17 are termi(cid:173)
`nated with windows 5 (only o ne 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. Tbe probe cover
`may be fabricated of such material as polypropylene having
`thickness ranging from 0.0005 to 0 .010" and having an
`appropria te conforming shape to envelop components that
`may come in contact witb the patient's tissues.
`
`[0044) To improve functionality of the probe by means of
`a temperature measurement function, plug 1 carries on or
`near its outer surface temperature sensor 6. That sensor is in
`ao intimate thermal contact with ear canal 4 walls. Tem(cid:173)
`perature sensor 6 may be positioned on extension 3 (not
`shown) near windows 5 . ln that case, extension 3 should be
`fabricated of a material with low thermal conductivity,
`meaning that it should be thermally de-coupled from probe
`2 . Alternatively, temperature sensor 6 may be position on
`plug 1 at the opposite s ide from extension 3 as in FIGS. 1
`
`[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 11
`between button 30 and heat equalizer 19. That signal is
`amplified by pre-amplifier 25 and channeled out of the probe
`via a communication link, for example cable 26. The abso(cid:173)
`lute temperature T 0 of beat equalizer 19 is measured by an
`imbedded temperature sensor 22, for example a thermistor.
`Thus, temperature sensor 22 also measures temperature of
`
`011
`
`

`

`US 2005/0209516 Al
`
`Sep.22, 2005
`
`4
`
`second thermocouple junction 21. The internal core (deep
`body) temperature T b can be computed from an equation that
`accounts for the temperature gradient l:J..
`
`Tb•T,+(l +JI)I\
`(2)
`[0049) where value of is not constant but is function of
`both T, and Tb. Its runctiooal relationships shall be deter(cid:173)
`mined experimenta lly.
`
`[0050) To rurthcr improve accuracy, value of l:J. should be
`minimized. This can be achieved by adding a beater to beat
`equaljzcr 19. Pre-amplifier's 25 output signal 40 represent(cid:173)
`ing l:J. and temperature s igna141 rrom temperature sensor 22
`pass to control lcr 28 that provides electric power to heater 23
`imbedded into heat equalizer 19. Controller 28 regulates
`heater in such a manner as to minimize temperature diJier(cid:173)
`ence l:J., preferably close to 7.cro. Since button 30 that carries
`first junction 24 is auached to a wall of car canal 4 ,
`temperature of beat equalizer 19 eventually becomes close
`to that of ear canal 4. After some relatively s hort 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 arc thermally separated
`rrom each other by some media 42 of low thermal conduc(cid:173)
`tjvity. Plug 1 being rabricated of low beat conducting resin,
`for example silicone rubber, acts as such meilia. Tempera(cid:173)
`ture T. of heat equalizer 19 becomes close to the patient
`inner body core temperature Tb.
`
`[0051) Extension 3 that carries three windows 32, 33, and
`34 ( FIG. 2) proviues the photo-plethysmographic sensing
`function . Light guide 17 (FIG. 3) is optically connected to
`detectors/cmiuers 18. 1l1erc arc three light guides 17 in
`extension 3 and detector/emitters 18, but o nly one is shown
`for clarity. Alternatively, detcctor/cmhtcrs 18 may be posi(cid:173)
`tioned next to windows 5 thus climffiating a need for light
`g uides 17. Detector/emitters 18 contain one o f the following
`(sec also FIG. 5): first lig ht emilling diode (LED) 50
`operating at visible wavelength of about 660 om, second
`LED 52 operating at ncar infrared wavelength of about 910
`nm, and light detector 5 1. covering both o( the indicated
`wavelengths. Lig ht guides 17 s hould be fabricated of mate(cid:173)
`rial with low absorption in the wavelengths of operation.
`Examples of the materials arc g lass 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 or them. All these components form an
`optkal bead of a pulse oximeter. It detects the photo(cid:173)
`plethysmographic waves of the pulsatile blood at two wave(cid:173)
`lengths and pass them to module 27 for the signal process(cid:173)
`ing.
`
`[0052) 111erc arc many possible versions of operating
`LEDs 50, 52 and detector 51 and analyzing the photo(cid:173)
`plethysmographic waves that allow computation of the
`oxygen saturation of hemoglobin in arterial blood. These
`methods arc 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 beat equalizer 19 elevates
`temperature T. of extension 3 to the level that is close to a
`body core temperature. This increases blood p erfusion in the
`ear canal walls that, in turn, improves signal-to-noise ratio of
`a photo-pleth ysmographic pu lse.
`
`[0053)
`It should be noted, that just a mere elevation of
`temperature o ft he pulse oximetry components ma y improve
`
`blood perfusion and enhance accuracy. The elevation may be
`few degrees less or more than the core temperature. There(cid:173)
`fore, temperature sensor 6 may be absent while beater 23
`and sensor 22 would keep temperature of the assembly
`above ambient and preferably close to the patieot'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(cid:173)
`cation link 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 of light that are modu(cid:173)
`lated by the pulsatile blood to produce tbc photo-plethys(cid:173)
`mographic s ignals pass through a translucent ear plug. Tbus,
`the essential component o f this embodiment is a light
`transparent car plug that also ma y be used as a carrier of a
`temperature sensor. Contrary to the first embodjment, wben
`the optical components were incorporated into extension 3 ,
`the ability or an car plug to transmit lig ht allows to keep
`most of the optical components outside of the car canal and
`thus simplifies design and usc of the device.
`
`ince the pulse oximetry data and indirect blood
`[0056)
`pressure monitoring can be accompli.o;bed from signals that
`arc measured by the same optical probe, the same compo(cid:173)
`nents that arc used for the car pulse oximetry are fully
`applicable for the indirect arterial blood pressure monitoring
`as well.
`
`[0057) The Light emitting devices (for example, light emit(cid:173)
`ting diodes-LED) arc positioned inside probe 62 (FIG. 6)
`that is positioned outside of the patient body, while only ear
`plug 64 is inserted into car canal 4 of ear 60. IIJuminator 65
`is adjacent to the entrance of the ear canal and shie lded by
`shield 66 from a direct optical coupling with ear plug 64.
`Tbus, lig ht transmission assembly 63 is comprised of illu(cid:173)
`mina tor 65, shield 66 and car plug 64. Illuminator 65 and ear
`plug 64 should be s ubstantially optically homogeneous and
`transparent in the wavelengths of the lights emitted by the
`LEDs. Yet, they not necessarily need to be fab ricated of the
`same material. For example, illuminator 65 may be fabri(cid:173)
`cated of acrylic resin while car plug 64 may be fabricated of
`clear silicone resin. It may be desirable, however, tha t the
`illuminator has certain flexibility and pliability for beuer
`conformation to and coupling wi th 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 o r disposable.
`[0058) FIG. 7 illustrates the internal structure of oximetry
`sensor 67 where light transmission assembly 63 is discon(cid:173)
`nected rrom probe 62. This ability to disconnect may be
`important for practical usc as the entire light transmission
`assembly 63 may be made interchangeable and even (dis(cid:173)
`posable. The probe 62 internal components are protected
`from the environment by encapsulation 78 and data are
`transmitted via cable 80. llowever, dala may be transmillecl
`by other means, for example via radio or optical communj(cid:173)
`catioo Jinks. Internal circuit board 68 supports holder 76,
`light coupler 72, two LEDs 71 and 77, light detector 73 and
`heart rate indicating lig ht 70. lleater 69 may be added to
`warm up the interior of probe 62 and portion of ear 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 s ignal. Positions of the
`
`012
`
`

`

`US 2005/0209516 Al
`
`Sep.22,2005
`
`5
`
`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 emiuers. This arrangement will not change the general
`operation of the device.
`
`(0059) Light transmitting assembly 63 may be plugged
`into holder 76 so that bull 85, which is part of ear 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 bas 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 LEOs can
`send light through illuminator 65. As in many conventional
`pulse oximeters. LEOs 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(cid:173)
`length from going directly from illuminator 65 toward ear
`plug 64. Since car plug 64 is intended for insertion into an
`ear canal, to aid in this function, hollow bore 83 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
`ear 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(cid:173)
`truding ribs 84 that are pliable, flexible and resilient. As seen
`in FIG. 10, when