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`US 20030236647A1
`
`(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2003/0236647 A1
`Yuan at al.
`(43) Pub. Date: Dec. 25, 2003
`
`
`(S4) DIAGNOSTIC METHOD AND APPARATUS
`USING LIGHT
`
`Publication Clafislficatinn
`
`(76)
`
`Inventors; Gil-won Yvon, Seoul (KR); Hung-Sig
`Kim, Scongnam-cily (KR); Kye-jin
`Jean. Suwon-cily (KR); Jong-youn
`Lee, Yongin-cily (KR); Kun-knuk
`Park, Yongin-City (KR); Su-jin Kim,
`Dacjcon (KR); HnuII-jmlg .Iwa, Seoul
`(KR)
`
`(‘orrcsrmndcncc Address:
`LEE & STERBA, PLC.
`ll01 Wilson Boulevard, Suite 2000
`Arlington, VA 22209 (US)
`
`(21)
`
`Appl. No;
`
`10,387,552
`
`(22
`
`(30)
`
`Filed:
`
`Mar. 14, 2003
`
`Foreign Application Priority Data
`
`Mar. 16, 2002
`
`(KR) ....................................... 2002—14277
`
` (206!" [5/00
`.. 702.3183; Till-'19
`
`ABSTRACT
`(57)
`
`A diagnosis rnclhod and apparatus for measuring hloocl
`hemoglobin concenlration, oxygen saturation, pulse ralc,
`rcspiralion rate. or degree of aging, of blood vessels using.
`lighl includes an inputfoutpul unil for receiving a command
`for measurement [rum 2: user and for providing information
`on the result of a measurement to the user; a control unit for
`Iccciving lhc command for rnca5ururncnt from [he inpulr'
`outpul unil and for generaling a control signal; a light
`generaling unil for generaling :11 least lwo lighl beams l'or
`Incasurcmcnl according In Ihc control signal; a lighi rccciv-
`ing unil for receiving the lighl [mama lransmitlcd lhmugh an
`ohjccl Illa] is subjccl lo measurcmcm and for converting the
`rcucivcd lighl beams into clcclrical signals; and a data
`processing unil for processing 1hr; clcclrical signals received
`from [he light receiving unit and for oulputling information
`on [he msull of a predetermined measurement.
`
`101
`
`
`10?.
`
`103
`
`LlCHT
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`UNIT
`
`OBJECT TO
`BE MEASURED
`
`
`
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`
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`
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`
`104
`
`CONTROL
`UNIT
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`105
`
`
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`LIGHT
`RECEIVING
`UNIT
`
`
`
`DATA
`PROCESSING
`
`UNIT
`
`
`001
`
`Apple Inc.
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`US. Patent No. 8,923,941
`
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`

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`Patent Application Publication Dec. 25, 2003 Sheet 1 0f 9
`
`US 200150236647 A1
`
`FIG.
`
`1
`
`101
`
`10?
`
`103
`
`
`
`INPUT
`LIGHT
`/OUTPUT
`COLTNTEOL
`GENERATING
`
`
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`
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`PROCESSING
`UNIT
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`RECEIVING
`UNIT
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`
`20.3
`
`LIGHT
`RADIATOR
`
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`

`

`Patent Application Publication Dec. 25, 2003 Sheet 2 0f 9
`
`US 20030236647 A1
`
`FIG. 4
`
`
`
`RATIO
`CALCULATION
`PORTION
`
`
`
`HEMOGLOBIN
`CONCENTRATION AND
`OXYGEN SATURATION
`CALCULATION PORTION
`
`
`
`
`
`PULSE RATE
`CALCUI ATION
`PORTION
`
`
`
`
`
`RESPIRATION RATE
`CALCULATION
`PORTION
`
`
`
`DOA
`CALCULATION
`PORTION
`
`
`
`
`
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`

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`Patent Application Publication Dec. 25, 2003 Sheet 3 0f 9
`
`US 20030236647 A]
`
`FIG. 5
`
`
`
`004
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`

`

`Patent Application Publication
`
`Dec. 25, 2003
`
`Sheet 4 of 9
`
`US 20030236647 A1
`
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`

`Patent Application Publication Dec. 25, 2003 Sheet 5 of 9
`
`US 20030236647 A1
`
`FIG. 7
`
`
`
`RECEIVE COMMAND
`TO MEASURE FROM USER
`
`701
`
`
`
`
`
`GENERATE AT LEAST TWO
`LIGHT BEAMS HAVING
`DIFFERENT WAVELENGTHS
`BY DRIVING LED
`
`702
`
`703
`
`707
`
`
`
`
`
`RADIATF GENERATED LIGHT
`BEAMS INTO OBJECT
`
`SUBJECT TO MEASUREMENT
`
`
`RECEIVE LIGHT BEAMS
`TRANSMITTED THROUGH OBJECT
`
`705
`
`CALCULATE
`HEMOGLOBIN
`CONCENTRATION
`AND OXYGEN
`SATURATION
`
`
`
`CALCULATE
`DEGREE OF
`AGING OF BLOOD
`
`VESSELS
`
`
`
`CALCULATE PULSE RATE AND
`RESPIRATION RATE
`
`
`
`STORE CALCULATED RESULT
`AND PROVIDE IT TO USER
`
`
`
`
`
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`

`

`Patent Application Publication Dec. 25, 2003 Sheet 6 0f 9
`
`US 2003!!)236647 A1
`
`FIG. 8
`
`START
`
`SELECT AT LEAST TWO ISOBESTIC
`WAVELENGTHS FROM A RANGE OF
`WAVELENGTHS IN WHICH THE EXTINCTION
`COEFFICIENT FOR WATER IS SMALLER
`THAN THAT FOR HEMOGLOBIN
`
`INTO A SITE OF THE BODY
`
`SEQUENTIALL‘I’ RADIATE LIGHT BEAMS
`HAVING SELECTED WAVELENGTHS
`
`BO‘I
`
`802
`
`RECEIVE TRANSMITTED LIGHT BEAMS AND
`CONVERT THEM INTO ELECTRICAL SIGNALS
`
`803
`
`CALCULATE LIGHT ATTENUATION
`VARIATION FOR EACH WAVELENGTH
`
`80
`
`4
`
`CALCULATE AT LEAST ONE RATIO
`BETWEEN LIGHT ATTENUATION VARIATIONS
`
`805
`
`CALCULATE HEMOGLOBIN CONCENTRATION
`USING LIGHT ATTENUATION VARIATION RATIO
`
`806
`
`CALCULATE OXYGEN SATURATION USING
`HEMOGLOBIN CONCENTRATION
`
`807
`
`END
`
`007
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`FITBIT, EX. 1036
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`

`Patent Application Publication Dec. 25, 2003 Sheet ‘7 0f 9
`
`US 20030236647 A1
`
`FIG. 9
`
`9‘“
`
`90?
`"
`
`903
`
`904
`
`
`
`DETECT POINTS OF INFLECTION AT
`WHICH THE SLOPE CHANGES FROM
`POSITIVE TO NEGATIVE
`
`
`
`STORE THE POINT OF INFLECTION
`HAVING A VALUE GREATER THAN A
`PREDETERMINED THRESHOLD
`VALUE AS A PEAK
`
`FILTER PULSE WAVEFORM, COLLECTED
`FOR A PREDETERMINED PERIOD,
`THROUGH A BANDPASS FILTER TO
`OBTAIN PULSE WAVE SIGNAL
`
`DIFFERENTIATE FILTERED
`PULSE WAVE SIGNAL
`
`CALCULATE AVERAGE TIME INTERVAL
`BETWEEN DETECTED PEAKS
`
`905
`
`CALCULATE THE NUMBER OF PEAKS
`IN A BO SECOND INTERVAL. BASED
`ON THE AVERAGE TIME INTERVAL
`
`BETWEEN PEAKS, AS A PULSE RATE
`
`906
`
`END
`
`008
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`

`

`Patent Application Publication Dec. 25, 2003 Sheet 8 of 9
`
`US 200310236647 A]
`
`FIG. 10
`
`START
`
`IOOI
`
`1002
`
`I003
`
`1004
`
`1005
`
`1006
`
`
`
`DIFFERENTIATE FILTERED '
`
`RESPIRATION RESPIRATION SIGNAL
`
`DETECT POINTS OF' INFLECTION AT
`WHICH THE SLOPE CHANCES FROM
`POSITIVE TO NEGATIVE
`
`FILTER PULSE WAVEFORM, COLLECTED
`FOR A PREDETERMINED PERIOD.
`THROUGH A BANDPASS FILTER TO
`OBTAIN RESPIRATION SIGNAL
`
`
`
`STORE THE POINT OF INFLECTION
`HAVING A VALUE GREATER THAN A
`PREDETERMINED THRESHOLD
`VALUE AS A PEAK
`
`CALCULATE AVERAGE TIME INTERVAL
`BETWEEN DETECTED PEAKS
`
`CALCULATE THE NUMBER OF PEAKS
`IN A 60 SECOND INTERVAL. BASED
`ON THE AVERAGE TIME INTERVAL
`BETWEEN PEAKS. AS A RESPIRATION RATE
`
`
`
`END
`
`009
`
`FITBIT, EX. 1036
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`009
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`FITBIT, Ex. 1036
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`

`

`Patent Application Publication Dec. 25, 2003 Sheet 9 0f 9
`
`US 20030236647 A]
`
`FIG. 11
`
` FILTER PULSE WAVEFORM. COLLECTED
`
` 1101
`
`
`FOR A PREDETERMINED PERIOD,-
`TO OBTAIN PULSE WAVE SIGNAL
`
`DIFFERENTIATE FILTERED
`PULSE SIGNAL TWICE
`
`DETECT POINTS OF INFLECTION AT
`WHICH THE SLOPE CHANGES FROM
`POSITIVE TO NEGATIVE
`
`
`
`
`1 102
`
`1103
`
`1104
`
`
`
`CALCULATE DEGREE OF AGING OF
`BLOOD VESSELS BASED ON THE
`VALUES OF .INFLECTION POINTS
`
`
`
`
`
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`
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`

`

`US 2003/0236647 A1
`
`Dec. 25, 2003
`
`DIAGNOSTIC METHOD AND APPARATUS USING
`LIGHT
`
`BACKGROUND OF THE INVENTION
`
`[0001]
`
`l. Field of the Invention
`
`invention relates to a diagnostic
`[0002] The present
`method and apparatus using light. More particularly,
`the
`present
`invention relates to a method and apparatus for
`measuring bleed hemoglobin concentration, oxygen satura-
`tion, pulse rate, respiration rate, and degree of aging of blood
`vessels using light.
`[0003]
`2. Deseription ol' the Related Art
`[0004] Hemoglobin in red blood cells is responsible for
`supplying oxygen throughout the human body and is essen-
`tial for the normal function of every cell in the body. A
`reduced supply of oxygen to the body restricts the intercol-
`lular energy metabolism in tissues, and a lack of oxygen for
`a prolonged period of time results in death. Hemoglobin
`content is used as a measure of anemia and is measured to
`qualify a blood donor and to determine the volume of blood
`that may safely be taken from a blood donor.
`[0005] There is a need for real-time monitoring of a
`patient’s condition by measuring hemoglobin concentration,
`oxygen saturation, pulse rate, respiration rate, and degree of
`aging of blood vesscLs, especially in patients that are bleed—
`ing as the result of a trafiic accident and in patients in need
`of a surgical operation.
`In addition,
`there is a need for
`introducing a convenient method that enables a health care
`provider to check frequently biological conditions ot‘ chil-
`dren and pregnant females. in particular. by measuring these
`parameters.
`
`[0006] Conventionally, hemoglobin concentration is mea-
`sured in a medical institute for therapeutic or prophylactic
`purposes through chemical analysis ol'bloocl drawn from the
`body. The measurements of pulse rate, respiration rate, or
`degree of aging of blood vessels are typically conducted
`only by health care providers. Therefore, a convenient
`method enabling the general public to personally measure
`each of these parameters at home is required.
`
`SUMMARY 01" THE INVENTION
`
`[0007] The presrznt invention provides a method and appa-
`ratus for measuring blood hemoglobin concentration, oxy-
`gen saturation, pulse rate, respiration rate, and degree of
`aging of blood vessels using light.
`
`[0008] According to an aspect of the present invention,
`there is provided a diagnosis apparatus using light, including
`an inpulloutpul unit for receiving a command [or measure-
`ment from a user and for providing information on the result
`ol‘a measurement to the user; a control unit for receiving the
`command for measurement from the inputfoutput unit and
`for generating a control signal; a light generating unit for
`generating at least two light beams, each light beam having
`an initial intensity, for measurement according to the control
`signal; a light receiving unit for detecting the intensity of
`each of the at
`least
`two light beams after transmission
`through an object that is subject
`to measurement and for
`converting the received light beams into electrical signals;
`and a data processing unit [or processing the electrical
`signals received from the light receiving unit and for out-
`
`putting information on the result of a predetermined mean
`surcment to the inputtoutput unit.
`
`includes a
`the light generating unit
`Preferably,
`[0009]
`digitaletoianalog converter for receiving the control signal
`from the control unit and for converting the received control
`signal into an analog signal; a light emitting diode driver for
`driving a light emitting diode to generate the at
`least two
`light beams according to the analog signal; and a light
`radiator for radiating the generated light beams onto the
`object.
`
`Preferably, the light receiving unit includes a pho—
`[0010]
`todetector for detecting the intensities of the at least two
`light beams after transmission through the object and for
`converting the detected light beam intensities into analog
`electrical signals; a low-pass filter for filtering out a high
`frequency component of the analog electrical signals (rep-
`resenting the intensity of the at
`least
`two light beams
`received from the photodetector); and an analog-to-digital
`converter for converting the analog electrical signals (reps
`resenting the intensity of the light beams, from which the
`high-frequency component has been removed) into digital
`electrical signals
`
`In one embodiment of the present invention. the
`[0011]
`data processing unit may include a ratio calculation portion
`for receiving the electrical signals (representing the intensity
`ofthe at least two light beams received by the light receiving
`unit) from the light receiving unit and for calculating, for
`each wavelength ofthe at least two light beams, a ratio of the
`intensity of the light received by the light receiving unit with
`respect to the initial intensity of the light radiated from the
`light generating unit; and a hemoglobin concentration and
`oxygen saturation calculation portion for calculating a
`hemoglobin concentration value using the ratio calculated
`by the ratio calculation portion based on a correlation
`between light intensity variations and hemoglobin concen-
`trations and for calculating an oxygen saturation value using
`the calculated hemoglobin concentration value.
`
`invention,
`In another embodiment of the present
`[0012]
`the data processing unit may include a pulse rate calculation
`portion for receiving the electrical signals (representing the
`intensity of the at least two light beams output from the light
`receiving unit) from the light receiving unit, for extracting a
`pulse wave signal having a frequency corresponding to an
`average pulse rate per minute for humans from the received
`electrical signals, and for calculating a pulse rate based on
`an average time interval between peaks detected from the
`extracted pulse wave signal.
`
`In yet another embodiment of the present inven-
`[0013]
`tion, the data processing unit may include a respiration rate
`calculation portion for receiving the electrical signals (rcp-
`resenling the intensity of the at least two light beams output
`from the light receiving unit) from the light receiving unit,
`for extracting a respiration signal having a frequency cor-
`responding to an average respiration rate per minute for
`humans from the received electrical signals, and for calcu-
`lating a respiration rate based on an average time interval
`between peaks detected from the extracted respiration sig-
`nal.
`
`In still another embodiment of the present inven-
`[0014]
`tion, the data processing unit may include a degree of aging
`of blood vessels calculation portion for receiving the elec-
`
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`US 2003/0236647 A1
`
`Dec. 25, 2003
`
`trical signals (representing the intensity of the at least two
`light beams output From the light receiving unit) from the
`light receiving unit, for extracting a first pulse wave signal
`having a frequency corresponding to an average pulse rate
`per minute for humans from the received electrical signals,
`for differentiating the extracted first pulse wave signal into
`a second pulse wave signal
`to detect
`inflection points
`therein, for calculating a diagnostic index for the degree of
`aging of blood vessels using the values of the inflection
`points, and for calculating a degree of aging ofblood vessels
`using the calculated diagnostic index, based on a correlation
`between the degrees of aging of blood vessels and diagnostic
`indices therefor.
`
`In addition, the data processing unit may further
`[0015]
`include a data storage portion [or storing measured results
`and for outputting to the input/output unit a calculated result
`according to a control signal of the control unit.
`[0016] According to another aspect ol’ the present inven-
`tion,
`there is provided a diagnosis method using light,
`including (a) receiving a command for measurement from a
`user;
`(b) generating a control signal according to the
`received command for measurement; {c} generating at least
`1W0 light beams, each light beam having an initial intensity,
`for measurement according to the control signal; (d) radi-
`ating the at
`least
`two light beams onto an object
`that is
`subject to measurement, detecting the intensities of the at
`least two light beams after transmission through the object,
`and converting the detected intensities of the at
`least two
`light beams into electrical signals; and (e) processing the
`electrical signals to obtain int‘on‘nation on the result 01' a
`predetermined measurement.
`[001?]
`Preferably, generating the at least two light beams
`includes (cl) receiving the control signal and convening the
`received control signal into an analog signal; (c2) generating
`the at least two light beams according to the analog signal;
`and (c3) radiating the generated light beams onto the object.
`[0018]
`Preferably, radiating the light beams onto an object
`includes {dt)dctecting the intensities of the at least two light
`beams after transmission through the object and converting
`the detected light beam intensities into analog electrical
`signals; {d2} filtering out a high frequency component ofthe
`analog electrical signals (representing the intensity of the
`transmitter] light beams); and (d3) converting the analog
`electrical signals (representing the intensin of the light
`beams, front which the high-frequency component has been
`removed] into digital electrical signals.
`[0019]
`In one embodiment of the present invention, pro-
`cessing the electrical signals may include (e1) calculating,
`for each wavelength of the at least two light beams. a ratio
`of the intensity of the light beam detected in (d) with respect
`to the initial intensity of the light generated in (c); (e2)
`calculating a hemoglobin concentration value using the ratio
`calculated in (el) based on a correlation between light
`intensity variations and hemoglobin concentrations and cal-
`culating an oxygen saturation value using the calculated
`hemoglobin concentration value.
`invention,
`[0020]
`In another embodiment of the present
`processing the electrical signals may include extracting a
`pulse wave signal having a frequency corresponding to an
`average pulse rate per minute for humans from the electrical
`Signals obtained in (d); and calculating a pulse rate based on
`an average time interval between peel-ts detected from the
`extracted pulse wave signal.
`
`In yet another embodiment of the present invenu
`[0021]
`tion, processing the electrical signals may include extracting
`a respiration signal having a frequency corresponding to an
`average respiration rate per minute for humans from the
`electrical signals obtained in (d); and calculating a respira-
`tion rate based on an average time interval between peaks
`detected from the extracted respiration signal.
`[0022]
`In still another embodiment of the present inven-
`tion, processing the electrical signals may include extracting
`a first pulse wave signal having a frequency corresponding
`to an average pulse rate per minute for humans from the
`electrical
`signals obtained in
`(d); differentiating the
`extracted first pulse wave signal into a second pulse wave
`signal to detect inflection points therein; calculating a diag-
`nostic index for the degree of aging of blood vessels using
`the values of the inflection points; and calculating a degree
`of aging of blood vessels using the calculated diagnostic
`index. based on a correlation between the degrees of aging
`of blood vessels and diagnostic indices therefor.
`
`[0023] The diagnosis method may further include provid
`ing the result of the predetermined measurement to the user.
`wherein the user may be remotely located from the object
`subject
`to measurement. The diagnosis method may also
`further include storing the information on the result of the
`predetermined measurement.
`
`In any of the aspects and embodiments of the
`[0024]
`present invention. preferably, the at
`least two light beams
`have dih‘erent wavelengths. Also preferably. the at least two
`light beams are selected from a range of wavelengths in
`which the extinction cocflicient for water is smaller than that
`of hemoglobin and have a wavelength no longer than 1300
`nm. Preferably, the at least two light beams are isobestic and
`each has a wavelength selected from the group consisting of
`422 nm, 453 nm. 499 nm, 529 nm, 546 nm, 569 nm. 584 am.
`805 nm, and 1300 am.
`
`[0025] Another feature of an embodiment of the present
`invention is to provide a computer readable medium having
`embodied thereon a computer program for any of the
`above-described diagnosis methods.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0026] The above features and advantages of the present
`invention will become more apparent to those of ordinary
`skill in the art by describing in detail preferred embodiments
`thereof with reference to the attached drawings in which:
`[0027] FIG. 1 is a block diagram illustrating the overall
`configuration of a diagnosis apparatus using light, according
`to an embodiment of the present invention;
`[0028] FIG. 2 is a detailed block diagram of the light
`generating unit of FIG. 1;
`[0029] FIE. 3 is a detailed block diagram of the light
`receiving unit of FIG. 1;
`
`[0030] FIG. 4 is a detailed block diagram of the data
`processing unit of FIG. 1;
`[0031] FIG. 5 is an exemplary pulse wave measured in
`accordance with an embodiment of the present invention;
`
`[0032] FIG. 6 are graphs ofquantitative diagnostic indices
`for the degree ol‘ aging 01‘ blood vessels, which are applied
`in the present invention;
`
`012
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`

`

`US 2003/0236647 A1
`
`Dec. 25, 2003
`
`DJ
`
`illustrating a diagnosis
`flowchart
`[0033] FIG. 7 is a
`method using light, according to an embodiment of the
`present invention;
`illustrating a method for
`[0034] FIG. 8 is a flowchart
`measuring hemoglobin concentration and oxygen saturation
`in step 705 of FIG. 7;
`illustrating a method for
`[0035] FIG. 9 is a flowchart
`calculating pulse rate in step 706 of FIG. 7;
`
`illustrating a method for
`[0036] FIG. 10 is a flowchart
`calculating respiration rate in step 706 of FIG. 7; and
`
`illustrating a method for
`[0037] FIG. 11 is a flowchart
`calculating degree of aging of blood vessels in step 70'? of
`FIG. 7.
`
`DETAILED DESCRIPTION OF TIIE
`INVENTION
`
`[0038] Korean Patent Application No. 2002-14272, filed
`on Mar. 16, 2002, and entitled: “Diagnostic Method and
`Apparatus Using Light ." is incorporated by reference herein
`in its entirety.
`
`[0039] Several embodiments of a diagnosis method and
`apparatus for measuring blood hemoglobin concentration,
`oxygen saturation, pulse rate, respiration rate, and degree of
`aging of blood vessels using light, according to the present
`invention, will now be described with reference to the
`appended drawings.
`
`[0040] FIG. 1 shown the overall configuration of a diag-
`nosis apparatus using light. according to an embodiment of
`the present invention. The diagnosis apparatus of FIG. 1
`includes an inputtoutput unit 101, a control unit 102, a light
`generating unit 103, a light receiving unit 104, and a data
`processing unit 105.
`
`In operation, a user provides the input/output unit
`[0041]
`101 a parameter to be measured, such as blood hemoglobin
`concentration, oxygen saturation, pulse rate, respiration rate,
`degree of aging of blood vessels {hereinafter "DOA"). The
`inputtoutput unit 101 informs the user of the result of a
`measurement of the input parameter. The inputt‘output unit
`101 may use a button, a mouse, a keyboard, or the like as an
`input device and may use a computer monitor, a liquid
`crystal display (LCD), or other display as an output device
`for providing the information regarding the result of the
`measurement to the user. Alternatively. information on the
`result of a measurement may be transmitted via,
`for
`example. an R5232 port to an external personal computer
`(PC). a personal digital assistant (PDA), or the like. Accord—
`ingly, the user may be remotely located from the patient and
`the object subject to the measurement.
`
`[0042] The control unit 102 receives a command to mea-
`sure a predetermined parameter from the inputioutput unit
`101 and transmits information on the parameter to the light
`generating unit 103, the light receiving unit 104, and the data
`processing unit 105‘ The control unit 102 also verifies the
`operation of each unit of the diagnosis apparatus.
`
`[0043] The light generating unit 103 generates at least two
`light beams having predetermined wavelengths for measure-
`ment according to the information on the parameter received
`from the control unit 102. A detailed configuration of the
`light generating unit 103 is shown in FIG. 2. Referring now
`
`the light generating unit 103 may include a
`to FIG. 2,
`digital-to-analog converter (DAC) 201 for converting a
`digital control signal received from the control unit 102 into
`an analog signal. a light emitting diode (LED) driver 202 for
`receiving the analog control signal and for driving an LED
`that generates the at least two light beams having predeter—
`mined wavelengths, and a light radiator 203 [or externally
`radiating the at least two light beams onto an object to be
`measured.
`
`[0044] Referring back to FIG. I, the light receiving unit
`104 measures the intensities of the light beams transmitted
`through the object, among the light beams emitted from the
`light generating unit 103, and converts the light beams to
`electrical signals. The configuration of the light receiving
`unit 104 is shown in detail in FIG. 3. Referring now to FIG.
`3, the light receiving unit 104 may include a photodetector
`301 for detecting the intensities of the light beams trans-
`mitted through the object and for converting the light beams
`to electrical signals. a low-pass filter (LPF) 302 for filtering
`out a high frequency component of the electrical signals
`representing the intensity of the light beams received from
`the photodetector 301, and an analogue—digital converter
`(ADC) 303 for converting the analog electrical signals, from
`which the high-frequency component has been removed by
`the [,PF 302, into digital electrical signals.
`
`[0045] Referring back to FIG. 1. the data processing unit
`105 receives the electrical signals representing the intensity
`of the received light beams from the light receiving unit 104
`and processes the received electrical signals to provide
`information on the result of a measurement of the input
`parameter, such as blood hemoglobin concentration, oxygen
`saturation, pulse rate, respiration rate, and DOA of blood
`vessels. The configuration ut‘thc data processing unit 105 is
`shown in detail in FIG. 4.
`
`[0046] Referring to FIG. 4, the data processing unit 105
`may include a data storage portion 406, a ratio calculation
`portion 401, a hemoglobin concentration and oxygen satu-
`ration calculation portion 402, a pulse rate calculation por-
`tion 403, a respiration rate calculation ponion 404, and a
`DOA calculation portion 405. The function ofeach of these
`elements will now be explained.
`
`[0047] The ratio calculation portion 401 receives the digi—
`tal intensity signals for the received light beams output from
`the light receiving unit 104 and, for each of the light beams,
`calculates a ratio of the intensity of the light received by the
`light receiving unit 104 with respect to the initial intensity of
`the light radiated from the light generating unit 103 onto the
`object that was subjected to the measurement.
`
`[0048] The hemoglobin coneentrat ion and oxygen satura—
`tion calculation portion 402 calculates a hemoglobin con-
`centration value using the ratio calculated by the ratio
`calculation portion 401 based on a correlation between light
`intensity variations and hemoglobin concentrations. and
`calculates an oxygen saturation value using the calculated
`hemoglobin concentration value. A method for calculating
`oxygen saturation following the calculation of hemoglobin
`concentration is briefly described below. Oxygen saturation,
`which is expressed as a percentage of the concentration of
`oxyhemoglobin bound to oxygen with respect to total hemo-
`globin concentration, is measured to quantify the amount of
`oxygen saturated in blood for the normal function of body
`cells. To measure oxygen saturation, red light and infrared
`
`013
`
`FITBIT, EX. 1036
`
`013
`
`FITBIT, Ex. 1036
`
`

`

`US 2003/0236647 A1
`
`Dec. 25, 2003
`
`light are transmitted through biological tissues, the absora
`bance for each wavelength of the radiated lights is measured
`using pulses of arterial blood, and a ratio of the measured
`absorbances is calculated as the oxygen saturation. Most of
`the light radiated on the human body is absorbed by bones,
`tissues. etc, which are not involved in pulsing, via prede—
`termined travelling paths, and only [—296 of the light radi-
`ated is absorbed by arterial blood, which induces pulses. By
`measuring the intensity of the light transmitted through the
`body, the light absorbencies of the pulsing components and
`the non-pulsing components for each wavelength of the
`radiated light beams can be calculated, which will give the
`light absorlaance of hemoglobin present in the arterial blood.
`As a result, the oxygen saturation of hemoglobin can be
`determined from the absorbsnce ratio between the two
`wavelengths of light.
`
`[0049] The pulse rate calculation portion 403 receives the
`digital signals corresponding to the intensities of the
`received light beams from the light
`receiving unit 104,
`extracts a pulse wave signal having a frequency correspond-
`ing to an average pulse rate per minute for humans from the
`received digital signal, and calculates a pulse rate per minute
`based on an average time interval between peaks detected
`from the extracted pulse wave signal.
`[0050] More specifically, the pulse rate calculation portion
`403 receives the digital signals corresponding to the inten-
`sities of the light beams sequentially transmitted through a
`predetermined body site to be measured, e.g., a linger, and
`extracts only a pulse wave signal having a frequency in
`accordance with an average pulse rate for humans from the
`received signals using, for example, software such as a
`filtering program, Dilferentiation is performed on the pulse
`wave signal passed through a filter, and inflection points, at
`which the slope changes from positive to negative, are
`detected from the dill'erentiated pulse wave signal. When an
`inflection point has a value greater than a predetermined
`threshold value, the inflection point is stored as a peak. An
`average time interval between detected peaks is calculated,
`and the number of peaks in a 60 second interval is calculated
`based on the average time interval as a pulse rate.
`
`[0051] A received signal, as described above, may be
`classified into pulse waves, velocity pulse waves, or accel-
`eration pulse waves according to the signal processing
`technique applied to the received signal. In general, pulse
`waves refer to the original waveform of body pulses and are
`used to characterize the original body puLses. However, the
`original body pulses have too smooth a waveform for
`variations to be detected. To compensate for this smooth-
`ness, the original body waves are differentiated for clinical
`applications. These differential body waves are called
`“velocity pulse waves.“ Velocity pulse waves are used to
`analyze variations in the waveform of the original body
`waves. Velocity pulse waves, i.e., difllflential pulse waves,
`are Used in currently available pulse wave detectors. How-
`ever, variations in the original body waves cannot be fully
`analyzed with velocity pulse waves. For this reason, velocity
`pulse waves are further dilfercntiated into "acceleration
`pulse waves" for clinical uses. Recent advances in the
`medical engineering field, especially in the diagnosis of
`circulatory system disorders, have put greater importance on
`the use of electrocardiograms, photocardiograms, cardiac
`catheterizations, and the like. Although various experiments
`have been conducted on pulse waves. the consequence of
`
`pulse waves as a diagnostic index tends to be underestimated
`due to the simple pulse waveform and its nature of being
`susceptible to a number of factors. Pulse waves are consid~
`ered to be significant only to some extent
`in a limited
`number of peripheral vaseular diseases. l-lowever, based on
`the possibility of measuring cardiac failure by the palpation
`of the radial artery, research on pulse waves as a measure of
`cardiac resnrve or cardiac insufficiency has been conducted.
`Measuring cardiac failure by the palpation of the radial
`artery is based on the fact
`that certain types of cardiac
`disorders lead to a typical alternation in the pulse waveform
`resulting from abnormal hemokinetic behaviors. In addition,
`pulse waves can be used as a diagnostic index for vascular
`diseases, such as arterial occlusive disorders, alterations in
`vascular elasticity, etc.
`[0052] An example of a pulse wave is illustrated in FIG.
`5. Referring now to FIG. 5, a waveform indicated by
`reference numeral 501 and “PTG” corresponds to an original
`body pulse wave, and a waveform indicated by reference
`numeral 502 and “SDPTG” corresponds to an acceleration
`pulse wave generated by diflerentiating the waveform 501
`twrce.
`
`respiration rate
`the.
`[0053] Referring back to FIG. 4,
`calculation portion 404 receives the digital signals corre-
`sponding to the intensities of the received light beams from
`the light receiving unit 104, extracts a respiration signal
`having a frequency in accordance with the average respira-
`tion rate per minute for humans, and calculates a respiration
`rate based on an average time interval between peaks
`detected from the extracted respiration signal.
`[0054] The method for calculating the respiration rate per
`minute will be described in detail. A respiration signal
`having a frequency in accordance with the average respira—
`tion rate for humans is extraded from a pulse wave signal
`using a bandpass filter. This bandpass filter used may be
`implemented using software.
`[0055] Normal adults breathe 10-20 times a minute in a
`stable state and up to about 45 times a minute when
`exercising