I IIIII
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`US 20090105556Al
`
`(19) United States
`(12) Patent Application Publication
`Fricke et al.
`
`(10) Pub. No.: US 2009/0105556 Al
`Apr. 23, 2009
`(43) Pub. Date:
`
`(54) MEASUREMENT OF PHYSIOLOGICAL
`SIGNALS
`
`(75)
`
`Inventors:
`
`John Robe1.·t Fricke, Lexington.
`MA (US); Matthew Corbin
`W iggins, Concord, MA (US)
`
`Correspondence Address:
`OCCillUTJ ROilLlCEK & TSAO, LLP
`10 FAWCETT STREET
`CAMBRIDGE, MA 02138 (US)
`
`(73) Assignee:
`
`Tiax LLC. Crunbridge, MA (US)
`
`(21) Appl. No.:
`
`12/240,651
`
`(22) Filed:
`
`Sep. 29,2008
`
`Related U.S. Applica tion Data
`
`(60) Provisional application No. 60/995.723. filed on Sep.
`28.2007.
`
`Publication Classification
`
`(51)
`
`lot. C l.
`(2006.01)
`A61B 5100
`(2006.01)
`A 61B 511455
`(52) U.S. Cl . ......................................... 600/301:600/310
`ABSTRACT
`(57)
`
`A system includes au optical sensor and a signal processing
`module. The optical sensor is cont1gured to be positioned on
`an area of skin of a patient. The optical sensor includes a light
`source for illuminating a capillary bed in the area of skin and
`a photodetector. "D1e phorodet(;:ctor is configured to receive an
`opt ical signal from the capillary bed resulting from the illu(cid:173)
`mination and to convert the optical signal into an electrical
`signal, the optical signal characterizing a fluctuation in a level
`of blood in the capillary bed. The signal processing module is
`configured to process the electric signal using a nonstationary
`frequency estimation method to obtain a processed signal
`related to at least one of a heart rate and a respiration rate of
`the patient. Another aspect relates to obtaining a quantity
`related to the blood pressure of the patient in addition to or
`instead of obtaining a processed signal related to at least one
`of the heart rate and the respiration rate of the patient.
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`Patent Application Publication Apr. 23, 2009 Sheet 4 of 20
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`Patent Application Publication Apr. 23, 2009 Sheet 10 of20
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`US 2009/0105556 Al
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`PatentApplication Publication Apr. 23, 2009 Sheet 12 of20
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`
`.
`
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`
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`
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`
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`
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`
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`~
`''\.
`
`.,
`~<-
`
`_.
`_,
`
`-i::-·Systolic BP (cuff measurement}
`
`4~==~======~=====:======c,----~
`Inter-beat Interval, and Blood Pressure Trend Cofl1)arison
`
`.
`
`Photoplethysmograph Pulse Width, Height,
`
`--Jnter-be3tlnterval,lnverse (earclip me3surement)
`--PPG Pulse W'idth. Inverse (earelip measurement)
`
`~
`
`;
`E
`5 3 -Pulse Height, Inverse [eouclip measurement)
`
`Me"n Arteri"l Pressure {cuff measurement}
`
`1402
`
`1400
`
`Interval
`Inter-beat
`
`015
`
`

`

`0 ..,
`
`U1
`
`0
`N
`
`1502
`
`1500
`
`Log file
`
`Data Storage
`
`Signal Processing
`
`System Control
`
`and
`
`front-end
`Analog
`
`Control
`
`To Sensors
`
`Fig. 15
`
`1512
`
`1510
`
`Battery and Power Management
`
`Power Subsystem
`
`e.g. data download
`Communication ~~•To laptop,
`
`PDA
`
`1506
`
`Sensor Interface
`
`Portable Electronics Unit
`
`1505
`
`016
`
`

`

`Estimate #3
`
`Respiration Rate
`
`1636
`
`r--.
`
`Frequency (RR}
`Instantaneous
`
`1626
`
`.
`.
`
`1634
`
`Transform
`Analytic
`
`1624
`
`Estimate #2
`
`Respiration Rate
`
`!-----.
`
`Frequency (RR)
`Instantaneous
`
`Transform
`Analytic
`
`..
`
`l 21
`
`1616
`
`Height)
`
`Signal Envelope (Pulse
`
`1614
`
`Estimate #1
`
`Respiration Rate
`
`~
`
`Frequency (RR)
`Instantaneous
`
`..
`
`Transform
`Analytic
`
`Fig. 16
`
`1632
`
`(fRR)
`
`Band-pass Filter
`
`.
`
`1622
`
`(fRR)
`
`Band-pass Filter
`
`L
`
`1612
`
`(fRR)
`
`Band-pass Filter
`
`L
`
`Estimate
`Heart Rate
`
`~..-
`
`1606
`
`Frequency (HR)
`Instantaneous
`
`1604
`
`Transform
`Analytic
`
`1602
`
`(fHR)
`
`Band-pass Filter
`
`1600
`PPG
`
`017
`
`

`

`> io-'
`
`Q\
`Ul
`Ul
`Ul
`0
`io-'
`
`0
`0
`N
`(J'J
`c:
`
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`
`0
`N
`
`Q ....
`"""'
`....
`(J'J =-
`
`-.....)
`
`('I)
`('!)
`
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`0
`0
`N
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`>
`=
`-· Q
`= -
`a' -;::;·
`c
`.,
`Q =
`~ 'e :::: n = :t.
`('!) = ...
`-,:1 = ....
`
`PPG Out
`L)
`Line Out
`Delay
`c=)
`
`Rate
`Heart
`
`Estimated
`
`lnst. Freq
`Filtered
`
`-0-0.2 H
`
`LPF
`
`Integer Delay4
`
`•I -1
`
`z
`
`1610
`
`Integer Delay3
`
`•I 03
`
`z
`
`Tsz
`K (z-1}
`
`~
`
`)\
`1606
`
`Approximation
`Hilbert Transform
`
`A
`1604
`
`(
`
`Fig. 17
`
`~I;' I
`
`Integer Delay2
`
`-0.5-2.3 Hz
`
`BPF
`
`Line In
`Delay
`
`018
`
`

`

`Heart Rate Out
`
`.--.c=)
`
`Delay Line Out
`
`..----.(!)
`
`-0-0.03 Hz
`
`Respiration Rate
`
`·
`
`LPF
`
`-~
`
`Fig_ 18
`
`1620
`
`Integer Delay4
`
`Integer Oelay3
`
`1 ______ ____...._, /
`
`Approximation
`Hilbert Transform
`
`-0.08-0.6 Hz
`
`BPF
`
`-~Ieger Oelay2
`Ll-i75 .-1 __..I :a ~---
`r
`....____,t---.-.1~ tntege~~tayt
`
`~~">I "&I bJ?: 1"1 K,!~~l ~~~Tool~---.~si:at2
`
`1618
`
`'\
`
`(
`
`omp ex
`c
`eal-lmag to Complex to Unwrap Discrete Derivative
`
`Angle
`
`1
`
`A __ _
`1616
`
`,.-----'A
`1614
`
`.-.. ( ~ \
`
`019
`
`

`

`lay Line Out
`Q:J
`
`'
`\ ( ____ _,/\.._ . __ _
`
`1626
`
`J.
`
`..-_____ A.__
`
`1624
`
`(,
`
`1630
`
`(---~A ___ _ '
`
`1602
`
`Fig. 19
`
`In
`Line
`Delay
`
`In
`PPG
`
`020
`
`

`

`1640
`
`Integer Delay41nteger Del ~
`
`PPG Out
`
`Integer Delay3
`
`Integer Delay2
`
`~I -il' ~---1 _.~I :o t--1 ------...... ~ ~L-z----11
`
`Approximation
`Hilbert Transform
`
`-0-0.03 Hz
`
`Rate
`
`LPF
`
`Angle
`
`Complex
`eal-lmag to Complex to Unwrap Discrete Derivative 1------' Respiration
`
`I ,., ~ Estimated
`
`0
`
`j:J=j .. ~~to:.~~ K*') L..~Tool
`
`_
`
`L:J,.,
`
`1638
`
`1632
`
`(
`\
`~----~~----~ ---------~---------
`
`1636
`
`1634
`
`\(
`
`Fig. 20
`
`In
`
`021
`
`

`

`US 2009/0105556 A1
`
`Apr. 23, 2009
`
`1
`
`MEASUREMENT OF PHYSIOLOGICAL
`SIGNALS
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`(00011 This application claims priority to U.S. provisional
`application No. 60/995,723. filed Scp. 28, 2007, entitled
`"Method and Devices tor Measurement of Multi-modal
`Physiological Signals," wh1cb is incorporated hereiJ1 by ref(cid:173)
`erence.
`
`STATEMENT REGARDING FEDER..L\LLY
`SPONSORED RESEARCH
`
`(0002] TI1e subjeclmat1erdescribed in this applica tion was
`partially funded by the Government of the Uni ted States
`under Contract No. W91ZLK-04-P-0239 awarded by the
`U.S. Depanment of 1be Anny. The government has certain
`rights in the invention.
`
`FIELD OF TilE INVENTION
`( 0003 J The invention relates to measurement of phys iologi(cid:173)
`cal s ignals.
`
`BACKGROUND
`
`(0004) Physiological signals are important for monitoring a
`subject's physical and cognitive state. Often, heart rate
`parameters arc measured d irectly via electrocardiogram
`(ECG) measurements of a heart beat. Respiration rate data
`can be obtained from a respiration chest strap. Physiological
`signals can also be extrac ted from infrared (JR) photopletllys(cid:173)
`mographs (PPG). The signals of interest include heart rate.
`respiration rate, continuous blood pressure, and iJltrathoracic
`pressure. With resp<.-ct to blood pressure, there is technology
`related to collecting data at nvo locations on the body and
`using pulse transit time and other parameters as the basis of
`the pressure estimate.
`
`SUMMARY
`
`In a general aspect, a system includes an optical
`(0005)
`sensor and a signal processing module. The optical sensor is
`couJ'igured to be positioned on an area of skin of a patient. The
`optical sensor includes a light source for illuminating a cap(cid:173)
`illary bed in the area of skin and a photodetector. The photo(cid:173)
`detector is configured to receive an optical signal from the
`capillary bed resulting from the illumination and to convert
`the optical signal into an electrical signal, the optical signal
`characterizing a fluctuarion in a level of blood i.n the capillary
`bed. The signal processing module is configured to process
`the electric signal using a nonsiationary frequency estimation
`method to obtailt a processed signal related to at least one of
`a heart rate and a respiration rate of the patient.
`(0006] Embodiments may include one or more of the fol (cid:173)
`lowing. Tlte system includes an output for providing infor(cid:173)
`mation detenuined from the processed signal. The nonsta(cid:173)
`tionary frequency estimation method includes a Hilbert
`transform metl1od or an instantaneous frequency esti111ation
`method. The processed signal includes at least one of instan(cid:173)
`taneous heart rate, inter-beat interval. heart rate variability,
`high-low heart rate ratios, respiration rate, inter-breath inter(cid:173)
`val. and respiration rate variability.ll1e fluctuation in ti1e level
`ofblood in the capillary bed re lates to a change in at least one
`
`of volume and pressure of the thoracic cavity or to a chMge in
`at least one of voltune and pressure of au organ in the thoracic
`cavity.
`(0007] The system includes an auxiliary sensor configured
`to detect an ambient signal The auxiliary sensor includes at
`leastoueofaccelerometer. a pressure sensor, an optical detec(cid:173)
`tor, a temperature sensor, and a piezoelectric device. The
`signal processing module is conf}gured to remove an elTect of
`the ambient signal from the e lectrical signal. 11Je optical
`signal is a reflectance or a transmittance oft he capillary bed.
`ln another general aspect. a method includes illtuni(cid:173)
`[0008)
`nating a capillary bed in an area of skin of a patient, receiving
`an optical signal from the capillary bed resulting from the
`illumination, converting the optical signal into an electrical
`sigoal, and processing the electrical signal using a nonstation(cid:173)
`ary frequency estimationmedlOd to obtain a processed signal
`related to at least one of a heart rate and a respiration rate of
`the patiem. "llJe optical signal characterizes a nuctuation in a
`level of blood in the capillary bed.
`(0009] Embodiments may include one or more of the fol(cid:173)
`lowing. The method inc ludes outputting information deter(cid:173)
`mined from the processed signal. Processing the electrical
`signal using the nonstationary frequency estimation meti1od
`includes perJomting a Hilbert transform or processing the
`electrical signal using an instantaneous frequency estimation
`method. Processing the electrical signal usil1g the instanta(cid:173)
`neous frequency method inc! udes band pass filtering the elec(cid:173)
`trical signal, determjning an instamaneous frequency of the
`electrical signal, and using the instantaneous freqttency to
`t1btain ti1e processed signal.
`[0010] The method fu rther includes processing the electri(cid:173)
`cal s ignal using a model to obtain a blood pressure signal
`related to a blood pressure of the patient. The optical signal
`characterizes a capillary refi ll time in the capillary bed. Pro(cid:173)
`cessing the electrical signal includes processing the electrica I
`signal in real time.
`ln another aspec t, a method for monitOJmg blood
`[0011]
`pressure includes illuminating a capillary bed in an area of
`skin of a patient, receiving an optical signal from the capillary
`bed resulting Jiom the illumination, converting the optical
`signal into an electrical signal, and processing the electrical
`signal using a model characterizing a relationship of the fluc(cid:173)
`tuation in the level of blood and the blood pressure of the
`patient tu obtain a quantity related to the blood pressure of the
`patient. 1lte optical signal cbaracterizes a lluctuation in a
`level of blood in the capillary bed of the patient.
`[0012] Embodiments may include one or more of the fol(cid:173)
`lowing. The method includes outputting inJormation deter(cid:173)
`mined based on the quantity related to the blood pressure of
`tbe patient. Tile optical signal characterizes a capillary refill
`time. The method 1\.trther includes engaging a device to
`restrict circulation in the capillary bed of the patient and
`disengaging the device prior to receiving the optical signal
`from the capillary bed. ll1e disengaging of the device occurs
`gr.1dually. The device is an active clamping device.
`[0013] The quantity related to the blood pressure of the
`patient is a quantity related to the contiuuQus blood pressure
`of the patient. Applying the model includes applying a model
`including circuit elements or properties of the capillary bed.
`The method further includes calibrating the model on the
`basis of a blood pressure of the patient determined by using a
`blood pressure cuff.
`
`022
`
`

`

`US 2009/0105556 Al
`
`Apr. 23, 2009
`
`2
`
`(0014] Embodiments may include one or more of tl1e fol(cid:173)
`lowing advantages.
`( 0015] A system or method as described above can be used
`for both military and civilian applications. Combat casua liy
`care requires close monitoring of vital signs from the moment
`that a medic first attends to a wmmded soldier in the battle(cid:173)
`field and thence through the many transfer stages to the point
`of full hospital care. general1 y removed from the combat
`scene. Similar needs are evident in the civilian collllllunity
`where critical care is administered by first responders at the
`scene of accidents. by emergency room staff, and by intensive
`care unit staff. It is often desirable to obtain maximum infor(cid:173)
`mation using as little equipment as possible. The system and
`method described herein support this need. They reduce the
`burden of equipment logistics. the burden of extra wires and
`sensors on and around the patient. and the complex.ity and
`cost of using multiple devices.
`(0016] For both military and civilian applications. a dispos(cid:173)
`able, wearable device in keeping with the systen1 and method
`described herein can be adapted to stay with a patient a nd to
`report vital signs throughout the care and transport processes.
`Further. tlJe system ca11 be configured to provide medical
`personnel with real-tin1e visibility of vital signs as well as
`recording of this information tor playback by attending medi(cid:173)
`cal staff at a later time. 111e disposability of the device allows
`it to be fabricated with low cost parts and eliminates lhe need
`for sanitization and asset tracking logistics in large scale
`clinical or military uses.
`(0017] Sucb system and methods additionally support
`applications in fitness monitoring. where lheirease of use and
`robustness make them a compel.ling altemative to chest strap
`monitors for the monitoring ofcardiacand respiratory param(cid:173)
`eters during exercise. An ear-wom device can also integrate a
`speaker w1it for mobile electronic devices such as mobile
`phones or music players.
`(0018) An advantage of applying a uonstationary fre(cid:173)
`quency estimation method (e.g., analysis involving monitor(cid:173)
`ing the frequency changes of tbe signal over time. such as
`monitoring changes in the instantaneous principal frequency
`over time) is that it is possible to avoid a tradeoff inherent in
`lll311Y stationary estimation methods between frequency reso(cid:173)
`lution and duration of data signals being ru1alyzed. For
`exan1ple, if the signal is assumed to be stationary within each
`of a series of data windows, the frequency resolution is gen(cid:173)
`erally inversely proportional to the duration of the window.
`As the window duration increases, the assumption of a sta(cid:173)
`tionary signal is increasingly violated and/or nonstationary
`events (e.g .. transients) are more difficult to detect. At least
`some nonstationary frequency analysis methods. which may
`be based. wi thout limitation. on a Hilbert transform approach,
`tracking of a nonstationary model, nonstat ionary principal
`frequency ru1alysis. or other time-frequency methods, miti(cid:173)
`gate the effects of such a time-frequency tradeoJT. Further(cid:173)
`more, us eo f sucb nonstationary techniques, as opposed to use
`of time domaiu peak picking and/or threshold based tech(cid:173)
`niques, can provide robustness of algorithm against artifacts,
`and provide sensitivity to periodicity without being burdened
`by a window that can reduce the time resolution.
`[0019] Other features and advantages are apparent from the
`following description and from the appended claims.
`
`13RI EF DESCRIPTION OF DRAWINGS
`
`[0020) PIG. J is a schematic diagram of a photoplethysmo(cid:173)
`graph (PPG) sensor system.
`
`[0021) FIG. 2 is a graph of a PPG detector s ignal taken over
`a 25 second period by an earlobe PPG device.
`[0022] FIG. 3 is a flow diagranJ of signal processing of a
`detector sig nal from a PPG device to obtain heart rate and
`respiration rate parru11eters.
`[0023) FIG. 4 is a graph of a result of band-pass filteri11g the
`data shown in FIG. 2 between 0.5 Hz and 5.5 Hz to extract a
`cardiac signal.
`[0024] FIG. 5 is a graph of a result of band-pass filtering the
`data shown in FIG. 2 between 0.17 Hz and 0.5 Hz to extract a
`respiration signal.
`(0025] PIG. 6 is a graph of an imer-beat interval obtained by
`applying an instantaneous frequency method to the cardiac
`signal shown in FIG. 4.
`[0026] FIG. 7 is a graph of a spectral analysis o f the inter(cid:173)
`beat in te1val data shown in FIG. 6.
`[0027] FIG. 8 is a graph of the respiration rate obtained by
`applying an instantaneous frequency method tO the respira(cid:173)
`tion signal shown in FIG. 5 .
`[0028] FIG. 9 is a diagram ofPPG measurements related to
`physiological states used to determine intrathoracic pressure.
`[0029] FIG. 10 is a graph of the otuptll of a matched filter(cid:173)
`ing process using thePPG detector signal shown in FIG. 2 and
`a pulse pilot signal.
`[0030] PIG. 11 is a block diagram of a least mean squares
`(LMS) adaptive fi lter.
`(0031 j FIG. 12 is a schematic diagram of au active clamp(cid:173)
`ing mechanism used to stimulate capillary refill.
`(0032) FIG. 13 is a diagram of a system model relating a
`PPG signal to blood pressure.
`(0033] FlG. 14 is a graph of trends in va rious physiological
`parameters bctore and duri11g a stress event.
`[0034] PIG. 15 is a block diagram of a portable electroJlics
`tmit.
`[0035] FIG. 16 is a flow diagram of methods to estimate a
`heart rate and a respiration rate.
`(0036] FIG. 17 is a flow diagram of a processing delay in
`the estimation of a heart rate.
`[0037] FIG. lS is a t1ow d iagram of a processing delay in a
`first method for the estimation of a respiration rate.
`[0038) FIG. 19 is a flow diagram of a processing delay in a
`second method for the estimation of a respiration ra te.
`(00391 FIG. 20 is a flow diagram of a processing delay in a
`third method for the estimation of a respiration rate.
`
`DE1:A. ILED DESCRIPTION
`
`(0040] Referring to FIG. 1, examples of an infrared pho(cid:173)
`toplethysmograph (PPG) device 100 are used to obtain physi(cid:173)
`ological signals related to o ne or more of heart rate. respira(cid:173)
`tion rate, blood pressure, and intrathoracic pressure. Such
`signals may be relevant for monitoring a pers011's s tate,
`rncluding one or more of tl1e person's physical state, long(cid:173)
`term health, psychological stare. and/or cognitive state. More
`generally, the physiological signals may provide information
`about the activity ofthe person's sympathetic and parasym(cid:173)
`pathetic nervous system. The PPG device 100 illustrated in
`FIG . 1 is attached to ane<u·lobe 102 of a person, lor exanJple.
`using a clamping or adhesive approach. However. i11 other
`embodiments. PPG device 100 is used on other areas of the
`skin of a person, including but not limited to a portion of a
`forehead, a neck, an arm, a forearm, a fmger. a leg, a back. an
`abdomen, or a stomach. In general. a requirement for the
`positioning of PPG device 100 is that the PPG sensor be
`located such that it can obtain a measurement via the skin that
`
`023
`
`

`

`US 2009/0 I 05556 A I
`
`Apr. 23, 2009
`
`3
`
`~~ rclat ... >d Ill bltlOd llO\\ t•r pressure. for example to measure a
`level ol blood m a capillary bed 104. for example. a blood
`\Oiumc. a rotc of blood 11o''· or a rote of change of blood
`volume. Note Jlso tlwt the approach is not limited to use of a
`l>in~le J>J>(, dC\ icc on an indi,idual. In some embodiments.
`multiple J>p(, dC\ 1ces are used. for example. on the torso
`and/or ut diOcrent extremities. and signals obtained at the
`dillcrent JIJ>(j devices arc processed independently or in com(cid:173)
`bination to determine underlying characteristics of the indi(cid:173)
`viduul's state.
`In some embodiments, such as that shown in FlG. l .
`100411
`nn infrared light source 106 illuminates theearlobe102. The
`blood level in copillory bed I 04 ai1ects the amount of light
`I 011 thot is backscattcred or rcnected by earlobe 102. Ligbt
`I 08 buckscattcn .. xl by earlobe 102 is received by an optical
`tronsduccr such O!> n photodctcctor lJ 0 and converted into a
`dcli .. 'CtOr signal 112. Since the blood now in capillary bed 104
`is cont"llled by the heart beat oft he person and thus the blood
`le\elmthc capillary bc..'<l varies with time. the backscath.:rcd
`light I 08 and hence the detector signal 112 are also time(cid:173)
`\ <If) 111~. In ttnother embodiment. the PPG sensor operates in
`tronsmis~1on mode and the light transmitted through the cap(cid:173)
`ilia!) bc..-d b recci\.1.-d b) the photodctector.
`100421 The dct ... -cton.ignal ll2 is sentto a signal processing
`unit 114 '' h1eh proccssc..'S the detector signal. which contains
`inft>rmation about the person's pulse. to extract desired physi(cid:173)
`ological dat<1. 10 variou~ embodiments including one or more
`nfin,t;mlanl'OII.,Iwar1 r:lh' inll'r·OOll interval. bean r.He \<tri(cid:173)
`ability. htgb·hl\\ hc..-nn mte rauo. rcspirotion rate. inter-breath
`interval. rc'pm.llion rJtc \-:Inability. blood pressure. and
`intrathoracic pre:.surc. A sin~le PPG de,·ice 100, referred to
`belo"' as an lntcgmtod Muhi-Modal Physiological Sensor
`(IMMJ>S), is cupublc of producing muhiple (or all) of such
`types or physiolngicul data.
`10043]
`In some embodiments, ihe PPG device 100 provides
`real-time visibility nf physiological parameters and vital
`signs, which can be tmnsmittcd tO other equipment for real(cid:173)
`time pn1cessing or J'or pl<eybnck or off-line processing at <I
`Inter time. In some cmb<ldimcnts, the PPG device includes
`user uutput devices. such as a set of light emitting diodes
`{1 liDs) (e.g .. u rc..xll Fl) 11 6. a yellow LED ll8. and a green
`I Fl) 120) or an :tudio device for producing alert sounds.
`which pro' kle <ln-de\ icc status on PPG device J 00. As an
`example IC.lr u~ of such output de\ ices, when a selected
`physiolo~icnl pnmmcter is in a normal range. green LED 120
`is 1un11.>d on.'' hen the physiological parameter is in a slightly
`nbnom1al mn~c. yellO\\ lfD 118 is turned on: when the
`ph) ,ioluttical raromcter IS in a dangerous range. red LED 116
`is turned on In some embodiments. the audio output device is
`u~>d to pro' IUc other nud1o output. such as the output for an
`ck'Clronic dC\ ICC -.uch a~ a mobile phooe or a music player. In
`some cmbodmJents. a'' irclcss link 122 to an external moni(cid:173)
`lorin~ sy,tcm J 24. such as n bedside system or a \vearable
`sy:.tcm. pro' ide' sensor data to the external system enabling
`a numcnc readout 126 of vnrious physiological parameter.>.
`In some embodiments. the PPG device. or at least some
`"'euruble portiun oft he device. is disposable. In such dispos(cid:173)
`:tble embodiments, the bedside system can be designed to be
`stcrilitcd tmd M1s1..-d: in another embodiment, the bedside
`system itself is also disposable. ln some embodiments, the
`b1..'Cisidc system includes Qr communicates with a centralized
`1nonitl'ring system thot monitor.> PPG devices of multiple
`putients.
`
`In 'i(lmc embodiments. the photodelector based
`100441
`detector 'i~nal is nugmentcd '' ith other signals. for example.
`accelerometer or pi'C~\ure o;cnsor signal~. For example. aux(cid:173)
`iliarv sensor. 130 arc cxmnectcd to signal processing unit J U
`'ia ~ '' in:d COIUlc..'CtiOil 132 In other embodiments. au.xiliary
`sensor.. 130 are OOMI..'Cted to signal processing unit 114 via a
`'' irclcss cmmcction .• \ux1liory sensor.> l30. such as tempera(cid:173)
`ture sensor:.. uccclerl)llleters. pressure transducers. optical
`deti..'Ctors. or p1C/Oclc..'Ctric films or matrices can provide aux(cid:173)
`iliary signals 132 rclat1..xl to ambient sources of noise to signaJ
`processing unit 11 4. Signnl processing unit l14 incorporates
`auxiliary signals 132 into the signal processing, for example,
`to incret~se t.he signal-to-noise ratio of the desired pbysioJogi(cid:173)
`cul claw.
`
`llet1rt nnd Rcspimtion Rate Signals
`
`(c.t11ttll...,/( I)J+ 4,.(/ICO<> (w,.u-..Jt(n}+
`
`100451 Rclcrrins to FIG . 2, in <111 embodiment of the PPG
`device 1h.1t usc~ n photodeteclor signal obtained from at an
`earlobe location. a dctc..'Ctor signal200 obtained from the PPG
`dc..'Vice 100 ha' a higb-Ji-~.-qucncy