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`US 20070016086A1
`
`[19) United States
`[12) Patent Application Publication (10) Pub. No.: US 2007/0016086 A1
`
`Inukai et a]. Jan. 18, 2007 (43) Pub. Date:
`
`
`(30}
`
`Foreign Application Priority Data
`
`Jun. 294 2005 (JP) 2005-1904139
`Jun. 2‘). 2005
`(JP) .................................... .. EGGS-190470
`
`Publication Classmcafilm
`
`(5 1)
`
`Int. Cl.
`
`(200631)
`A613 5/02
`(52) U.S. (.I.
`............................................ 6001485. 600600
`(57}
`ABSTRACT
`
`[54) BLOOD PRESSURE MONITORING
`APPARATUS
`
`[75)
`
`Inventors:
`
`llidckatstl lnukal. Nagoya-511i (JP);
`Tot-u Oka. lchinomiya-shi (.ll’)
`
`Correspondence Address:
`DRINKER RIDDLE & REATH (DC)
`[500 K STREET. KW.
`SUITE 1100
`
`W‘SulNG-l-ON‘ DC 200054209 (Us)
`'
`
`Assignm: FUKUDA "Ex-SI" c0“ LT”
`
`AppL Nu;
`
`11f475‘938
`
`Filed:
`
`Jun. 28, 2006
`
`OPERATION
`UNIT
`
`100
`
`W 50
`
`_5_
`
`In blood pressure monitoring apparatus which continuously
`estimates and monitors blood pressure by using the pulse
`wave propagation time. blood pressure fluctuation can be
`accurately estimated. If both blood pressure estimated from
`tlte pulse wave propagation time and a waveform parameter
`obtained from the accelerated pulse wave have abnormal
`values.
`il
`is determined [ital
`the blood pressure is truly
`fluctuating. and blood pressure measuremenl by another
`method. e.g.. blood pressure measurement using a coil. is
`performed.
`
`US. Patent No. 8,923,941
`
`1 O
`
`CUFF
`
`1 2
`
`'
`
`PRESSURE
`SENSOR
`
`1 4
`
`20
`
`ELECTRO-
`CARDIOGRAM
`ELECTRODE
`
`FINGER SENSOR
`{SP02,
`PULSE WAVE)
`
`OTHER
`SENSORS
`
`_
`
`'
`
`-
`
`
`
`
`
`—t-
`
`—=*
`
`PRINTER
`
`60
`
`DISPLAY
`
`70
`
`CONTROLLER
`
`_
`
`_
`
`I
`
`TO EXTERNAL
`APPARATUS
`
`Apple Inc.
`APL1035
`
`Apple Inc.
`APL1035
`U.S. Patent No. 8,923,941
`
`001
`
`FITBIT, Ex. 1035
`
`

`

`Jan. 18, 2007 Sheet 1 of S
`
`US 2007/0016086 A}
`
`.O¢H0m4m
`
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`
`FITBIT, Ex. 1035
`
`

`

`FIG. 2
`
`PLEI'HYSMOG RAPH
`
`US 2007/0016086 A1
`
`Patent Application Publication Jan. 18, 2007 Sheet 2 of 5
`
`ACCELERATED PULSE WAVE
`
`003
`
`FITBIT, Ex. 1035
`
`

`

`Patent Application Publication Jan. 18, 2007 Sheet 3 of S
`
`US 2007/0016086 A1
`
`FIG“ 3
`
`BLOOD PRESSURE
`MONITORING PROCESS
`
`START BLOOD PRESSURE
`MEASUREMENT USING
`CUFF, AND ACQUISITION
`OF ECG AND PULSE WAVE
`
`..
`
`S111
`
`8121
`
`MEASUREMENT USING CUFF
`
`HAVE
`TWO CONDITIONS
`BEEN CONTINUOUSLY MET
`FOR PREDETERNIINED PERIOD,
`OR HAS PREDEI'ERMINED TIME
`ELAPSED SINCE LAST
`MEASUREMENT
`9
`
`CALCULATE ACC ELERATED
`PULSE WAVE
`
`CALCULATE PULSE WAVE
`PROPAGATION TIME
`
`I
`
`r
`
`CALCULATE WAVEFORM
`PARAMETER
`
`IS FLUCTUATION
`AMOUNT ABNORMAL?
`
`OUTSIDE
`NORMAL RANGE?
`
`I'
`
`YES
`
`BLOOD PRESSURE
`
`S1 40
`
`004
`
`FITBIT, Ex. 1035
`
`

`

`Jan. 18, 2007 Sheet 4 of 5
`
`US 2007/0016086 A1
`
`mm>odimmw>OJ<nE
`
`wmomr
`
`8memac.
`
`n0.Ua.mbuP.n0.Ua.mD.D.AtnetaP.
`
`
`E39..-.l....m
`E953-.__.._...a?
`
`
`
`
`
`$8$5ll
`
`EBHED.II
`
`$39
`
`
`
`mwz<méfimoz
`
`005
`
`FITBIT, Ex. 1035
`
`

`

`Patent Application Publication Jan. 18, 2007 Sheet 5 of S
`
`US 2007/0016086 A1
`
`FHGDS
`
`EXPRESSION CALIBRATING PROCESS
`
`ACQUIRE ACTUALLY MEASURED VALUE
`
`S201
`
`3203
`
`COMPARE WITH ESTIMATED BLOOD PRESSURE
`VALUE 0R PAST ACTUALLY MEASURED VALUE
`
`w
`
`N0
`
`IS CALIBRATION NECESSARY?
`
`'
`
`S205
`
`YES
`
`CALIBRATE COEFFICIENT a
`
`8207
`
`8209
`
`IS WAVEFORM PARAMETER
`FLUCTUATION LARGE?
`
`YES
`
`D
`
`006
`
`FITBIT, Ex. 1035
`
`

`

`007
`
`[0013] According to one aspect of the present invention,
`there is provided a blood pressure monitoring apparatus
`comprising: blood pressure measuring urtit adapted to mea—
`sure blood pressure in response to blood pressure measure-
`ment designation; pulse wave acquiring uttit adapted to
`acquire a pulse wave in a predetermined location ofa living
`body: pulse wave propagation time calculating unit adapted
`to calculate a pulse wave propagation time from the pulse
`wave. and one of an electrocardiogram and a pulse wave
`acquired from a location dillerent from the predetermined
`location; estimated blood pressure calculating unit adapted
`to calculale an estimated blood pressure on the basis of the
`pulse wave propagation time; accelerated pulse wave cal-
`culating unit adapted to calculate an accelerated pulse wave
`from the pulse wave; waveform parameter calculating unit
`adapted to calculate a predetermined waveform parameter
`from a waveform contained in the accelerated pulse wave:
`and control unit adapted to provide the blood pressure
`tneasumment designation to the blood pressure measuring
`unit to cause the blood pressure measuring unit to measure
`blood pressure, if both the estimated blood pressure and the
`predetermined waveform parameter are abnormal.
`
`BLOOD PRESSURE MONITORING APPARATUS
`
`CLAIM OF PRIORITY
`
`[0001] This application claims priority from Japanese
`Patent Application Nos. 2005490496 and 2005-1901170.
`both filed on .ltlll. 29. 2005. which are hereby incorporated
`by reference herein.
`
`F1 ii] ’1) OF THE lNV’IfiiN'I‘ION
`
`invention relates to blood pressure
`[0002] The present
`monitoring apparatus for noninvasiver and continuously
`monitoring blood pressure.
`
`BACKGROUND OF THE lNVENTION
`
`In an operating room. ICU. or the like. it is sortie-
`[0003]
`times necessary to continuously monitor the blood pressure
`ofa patient. As a conventional tec‘rmique of noninvasiver
`and continuously monitoring the blood pressure. blood
`pressure estimation based on the pulse wave propagation
`time is known.
`
`[0004] This technique uses the fact that tlte tirlte (pulse
`wave propagation titne) required for a poke wavo to propa-
`gate between two points in a living body or the pulse wave
`propagation velocity obtained by dividing the blood vessel
`length between the two points by the pulse wave propaga-
`tion time has a correlation with the blood pressure. For
`example. the pulse wave propagation time is continuously
`measured and applied to an expression having a precali-
`busted coefficient.
`thereby continuously calculating and
`monitoring an estimated blood pressure (cg, Japanese
`Patent Laid—Open No. 10—66681).
`
`To measure the pulse wave propagation time. how-
`[0005]
`ever. pulse waves rnust be measured in different locations. so
`the measurement requires a long time. Also. it is sometimes
`difficult to attach sensors or ends for measuring pulse waves
`to two locations. As described in Japanese Patent Laid~0pen
`No. 10-65681. therefore. a general approach is to calculate
`the pulse wave propagation time by using an electrocardio-
`gram (ECG) normally measured by a biological infomtatiou
`monitoring apparatus and a pulse wave measured in one
`predetermined location (e.g.. a fingertip) of a living body.
`
`[0006] Unfortunately. the use of an [ECG in the calculation
`ofthe pulse wave propagation time has a problem of the
`measurement accttracy. That is. an ECG is a signal which
`represents not a pulse wave but the electrical state change of
`the heart. There is a time ditference (preejection period]
`between the tinting at which [lie electrical state change
`occurs and the timing at which the heart actually contracts
`to generate a pulse wave. Accordingly.
`the pulse wave
`propagation time calcttlaled by using the observation timing
`ofthe feature point of an ECG as a starting point contains an
`error caused by the preejection period.
`
`If the preelection period is constant. this error is
`[0007]
`easy to correct. However. the preejection period changes
`front one person to another. and can change occasionally
`even in the same person. Therefore. an improvement of the
`accuracy by correction is limited.
`
`[0008] Blood pressure monitoring apparatus normally per-
`forms control such that
`if blood pressure continuously
`measured on the basis of the pulse wave propagation time is
`
`US 2007f0016086 Al
`
`Jan. 18, 2007
`
`is
`abnonnaL more accurate blood pressure measurement
`performed by using a cuff or the like. and an alarm is outpttt
`if an abnom'ral value is detected by this measurement.
`
`[0009] Blood pressure measurement using a coil is estab—
`lished as a ruetltod of noninvasiver measuring the blood
`pressure. and effective to automatically obtain a well reliable
`blood pressure. However. this method requires avascular—
`ization. so the frequent use of the method is undesirable
`because the load on a patient increases. Therefore. accurate
`determination of the need for cutl‘ blood pressure measure-
`ment is important not only to perform an appropriate therapy
`but also to reduce the load on a patient.
`
`as
`accuracy
`determination
`the
`increase
`[0010] To
`described above. it is also important to increase the accuracy
`of the estimated blood pressure based on the pulse wave
`propagation time calculated from an ECG and a pulse wave
`observed at one point.
`
`SUMMARY Ol’ Tllll INVENTION
`
`[0011] The present invention has been tirade in consider—
`ation of the problems of the prior art as described above. and
`ltas as its object to make it possible to more accurately
`determine the necessity of lugh-acctuncy blood pressure
`measurement. in blood pressure monitoring apparatus which
`continuously estimates blood pressure on the basis of the
`pulse wave propagation time. and performs more accurate
`blood pressure measurement where necessary.
`
`invention to
`is another object of the present
`it
`[0012]
`increase the accuracy of an estimated blood pressure in
`blood pressure monitoring apparatus which continuously
`estimates blood pressure on the basis of the pulse wave
`propagation time.
`
`[0014] According to another aspect of the present inven—
`tion. there is provided a blood pressure monitoring apparatus
`comprising: blood pressure measuring unit adapted to mea—
`sure blood pressure by a predetermined method: pulse wave
`acquiring unit adapted to acquire a pulse wave in a prede—
`tem’rinetl location of a living body: pulse wave propagation
`time calculating unit adapted to calculate a pulse wave
`
`007
`
`FITBIT, Ex. 1035
`
`

`

`US 2007f0016086 Al
`
`Jan. 18, 2007
`
`the pulse wave. and one of an
`propagation time tion:
`electrocardiogram and a pulse wave acquired from a loca-
`tion difi'erent from the predetermined location: estimated
`blood pressure calculating unit adapted to calculate an
`estimated blood pressure by applying the pulse wave propa-
`gation time to a predetermined expression; accelerated pulse
`wave calculating unit adapted to calculate an accelerated
`pulse wave from the pulse wave: waveform parameter
`calculating unit adapted to calculate a predetermined wave-
`form parameter from a waveform contained in the acceler-
`ated pulse wave: and calibrating unit adapted to calibrate the
`expression by using a value measured by the blood pressure
`measuring unit. wherein if a fluctuation amount of the
`waveform parameter exceeds a predetermined amount. the
`calibrating unit performs the calibration after correcting a
`calibration amount which is applied when the fluctuation
`amount of the waveform parameter does not exceed the
`predetermined amount.
`
`008
`
`[0023] FIG. 5 is a flowchart explaining the operation of
`calibrating an expression for calculating an estimated blood
`pressure. in the biological information monitoring apparatus
`according to the embodiment of the present invention.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`[0024] A preferred embodiment of the present invention
`will now be described in detail
`in accordance with the
`accompanying drawings.
`
`[0025] FIG, 1 is a block diagram showing an example of
`the functional arrangement of a biological
`information
`monitoring apparatus as blood pressure monitoring appara-
`tus according to the embodiment of the present invention.
`
`[0026] Referring to FIG. I. a cufi'lfl has a band-like form.
`and incorporates a rubber pouch which expands and corn
`tracts by pumping of a pump 14. The cnfl' 10 is normally
`attached to one of Lhe limbs. typically the upper arm of a
`patient. A pressure sensor 12 senses a change in pressure
`applied to the gas filled in the internal rubber pouch ofthe
`cufl'lO. converts the pressure signal into an electrical signal.
`and outputs the electrical signal to a controller 100.
`
`[0027] An electrocardiogram (ECG) electrode 20 com-
`prising a plurality of electrodes is attached to a predeter—
`mined position of the chest of a patient. and outputs an
`induced waveform as an ECG signal to the controller 100.
`A finger sensor 30 is a so-called pulse oximetcr which
`optically senses and outputs an oxygen saturation degree
`(SPOZ) and plethysmograph to the controller 100. The
`absorbancc of hemoglobin changes in accordance with
`whether hemoglobin combines with oxygen. and also
`changes in accordance with the wavelength of light. On the
`basis ofthese facts, the finger sensor 30 generally measures
`the oxygen saturation degree by using two wavelengths. i.e..
`red light and infrared light. Also. since the AC component of
`transmitted light or reflected light changes in accordance
`with the blood [low volume. this AC component is detected
`as a photoplethysmograph (PTG).
`
`[0028] Other sensors 40 sense other biological informa-
`tion such as the respiration and body temperature of a
`patient. and one or more sensors are connected to the
`controller 100 as needed. The other sensors 40 are not
`directly related to the blood pressure monitoring operation
`of this embodiment, so no further explanation thereof will be
`made.
`
`[0029] An operation unit 50 is a man—machine interface by
`which the user (measurcr) inputs various settings and infor-
`mation concerning a patient and provides instructions to the
`biological information monitoring apparatus. The operation
`unit 50 is generally constructed by appropriately combining
`a keyboard. a mouse. buttons. switches. dials. a touch panel.
`and the like,
`
`[0030] A printer 60 and display 70 are representative
`output devices. and visually output the state ofthe apparatus.
`measurement results. and the like. An external interface (NF)
`80 is typically a network interface. serial interface (cg. a
`USB or IEEE1394). modem. or the like. and communicates
`with an external apparatus which is connected invasively or
`across a network.
`
`[0031] A storage limit 90 is typically a hard disk drive. and
`records programs for controlling the operation of the bio-
`
`In the present invention having the above arrange
`[0015]
`the necessity of blood pressure measurement by
`ntents.
`another method is determined by considering: the waveform
`parameter. which is obtained from the accelerated pulse
`wave and reflecting the functional state of the blood vessel.
`is taken into consideration as well as the continuous esti-
`mated blood pressure. which is based on the pulse wave
`propagation time calculated from an ECG and a pulse wave
`observed atone point. therefore. the determination accuracy
`can be increased.
`
`[0016] Also. according to the present invention. the wave-
`form parameter obtained from the accelerated pulse wave is
`taken into consideration in the calculation ofthe continuous
`estimated blood pressure based on the pulse wave propaga-
`tion time calculated from an IECG and a pulse wave mea-
`sured at one point. Accordingly. the accuracy of the esti-
`mated blood pressure can be increased
`
`[0017] Other features and advantages of the present inven—
`tion will be apparent front the following description taken in
`conjunction with the accompanying drawings. in which like
`reference characters designate the same or similar parts
`throughout the figures thereof.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[00.18] The accompanying drawings. which are incorpo-
`rated in and constitute a part of the specification. illustrate
`embodiments of the invention and.
`together with the
`description. serve to explain the principles of the invention.
`
`FIG. 1 is a block diagram showing an example of
`[0019]
`the arrangement of a biological
`infomiation monitoring
`apparatus as blood pressure monitoring apparatus according
`to an embodiment of the present invention;
`
`FIG. 2 is a graph showing examples ofan original
`[0020]
`waveform and its accelerated pulse wave;
`
`FIG. 3 is a flowchart explaining the blood pressure
`[0021]
`monitoring operation of the biological iulbrmation monitor-
`ing apparatus according to the embodiment of the present
`invention:
`
`FIG. 4 is a graph showing actual examples of blood
`[0022]
`pressure calculated by the biological information monitoring
`apparatus according to the embodiment, a direct blood
`pressure measured invasivcly. and waveform parameters:
`and
`
`008
`
`FITBIT, Ex. 1035
`
`

`

`US 2007l0016086 A1
`
`Jan. 18, 2007
`
`information monitorittg apparatus. various data,
`logical
`measurement results, personal information of patiettts. and
`the like. The storage unit 90 may also include at least one
`other type of storage device. e.g.. a device which reads and
`writes a writable removable medium such as a memory card
`or an optical disk.
`[0032] The controller 100 controls the operation of the
`whole biological
`in'lortttatiott monitoring apparatus. The
`controller 100 has. e.g.. a CPU and RAM. and controls the
`individual units by loading the control programs stored in
`the storage unit 90 into the RAM and executing the loaded
`programs by the CPU.
`thereby implementing processes
`including the blood pressure monitoring operation (to be
`described later] of the biological
`information monitoring
`apparatus. Note that not all the processes need be executed
`using software by the CPU. For example. signal processing
`such as All.) conversion and filtering of signals input from
`the various sensors may also be assigned to a DSIJ or
`dedicated hardware.
`thereby appropriater using another
`arrangement.
`
`009
`
`telesystolic component obtained when the blood pressure
`was measured last time by ttsing a cufl' is used as the other
`condition described above. That is.
`it is possible to deter“
`mine that the possibility Lhat the blood pressure has actually
`fluctuated is higher when a change is found in the center or
`periphery in addition to the change in estimated blood
`pressure.
`than when only the estimated blood pressure
`fluctuates or only the change in the center or periphery is
`found.
`
`[0039] Note that in this embodiment. a wave height ratio
`bio of b—wave to a—wave is used as a parameter indicating the
`state of tlte center. attd a wave height ratio dfa of dawave to
`a-wave is used as a parameter indicating the state of the
`periphery. The ratios to the wave height of a-wave are herein
`used in order to compare the parameters obtained from an
`accelerated pulse wave when no calibration exists in a strict
`sense. and this is a kind of normalization.
`
`the blood
`[0040] On the basis of the above deseription.
`pressure monitoring operation of the biological information
`monitoring apparatus according to this emboditnent will be
`explained with reference to a flowchart shown in FIG. 3.
`
`[004]] First. in step 510]. the acquisition ol'an ECG and
`pulse wave is started. Also. as initialization.
`initial blood
`pressure measurement using a eufi~ is perl'omted. and the
`initial values of an accelerated pulse wave parameter and
`estimated blood pressure are calculated by a method to be
`explained below. and stored in the storage unit 90. After that.
`the processing (steps 81]] to $115) of the accelerated pulse
`wave and the process (steps $121 to $125) ofestimating the
`blood pressnrt: on the basis ol‘ the pulse wave propagation
`velocity are performed in parallel.
`
`the controller 100 calculates the
`In step 8111.
`[0042]
`accelerated pulse wave frotn the photoelectric pIetItysmo-
`graph from the finger sensor 30. In step $113. on the basis
`of a-wave to d-wave contained itt one pulse of the acceler-
`ated pulse wave. parameters concerning the presystolic
`component and telesystolic component. i.e.. the wave height
`ratios bfa and dfa in this embodiment. are obtained.
`
`In step 8115, the controller 100 calculates fluctua-
`[0043]
`from the obtained panunctcr values and values
`tions
`obtained in the last eufl' blood pressure measurement. and
`determines whether
`the fluctuations are abnormal. For
`example, the controller 100 sets
`D1 (54:): l — {bi’n(currenll]flaxbtrel'tix [00
`Date/atet—{d/atcmreno}.-'{:rat:en}xton
`
`The controller 100 can check the presence/absence ofabnor—
`maIity by determining whether one. both. or a predetermined
`one of
`
`IJ'Jlfblln‘i
`Ifllg‘bi’hn’
`
`(In)
`Elli)
`
`is satisfied. Since. however. bta is a parameter indicating the
`state of the center. it is desirable to take account of at least
`the value of his. In step 3115. the parameters as objects of
`abnormality determination. the expressions for abnormality
`determination. and the threshold values used are predeter-
`mined. Ilowcvor. these values and expressions need not be
`fixed but can be changed any time.
`
`[0044] Note that in the above equations. (current) indi-
`cates a present calculated value. and (rot) indicates 3 refer-
`
`[0033] The blood pressure monitoring operation by the
`biological information monitoring apparatus of this embodi-
`ment will be explained below.
`
`[0034] The biological information monitoring apparatus
`ol'this embodiment is similar to the prior art in that the pulse
`wave propagation velocity is continuously calculated by
`using an ECG and plethysmograph. and an estimated blood
`pressure is continuously calculated by ttsittg an expression
`having a precalibrated coefficient. and that the necessity of
`blood pressure measurement using a cull is determined by
`using the estimated blood pressure.
`
`In this embodiment. however. it is determined that
`[0035]
`blood pressure measurement using a cufi'is necessary only
`when another condition is met in additiott to the estimated
`blood pressure. thereby increasing thc abnormality detection
`accuracy in continuotts blood pressure monitoring. This
`embodiment is characterized in that the value ol‘a parameter
`obtained from an accelerated pulse wave is used as the other
`condition.
`
`[0036] The accelerated pulse wave is obtained by calcu-
`lating second-order titnc differential of a pulse wave. and has
`characteristic waves from a-wave to e-wave as shown in
`FIG. 2. A-wave attd b-wave represent presystolic compo-
`nents. c—wave and d-wave represent
`telesystolic compo-
`nents. and e—wave represents a diastolic component (e.g..
`[kctani ct aI.. “Plcthysmograph [Accelerated Pulse Wave]
`for Evaluating Degree oI'Arteriosclcrosis by Hypertension".
`vol. 10. no. 6. 2003. pp. 54-60).
`
`[0037] According to lketani et at. the presystolic compo-
`nent reflects-a driving pressure wave generated by ejection
`of the blood when the heart contracts. and the telesystolic
`component is a re-elevated pressure wave generated when
`the driving pressure wave propagates to the periphery. and
`the returned reflected wave overlaps the driving pressure
`wave. Accordingly. it can be presumed that the presystolic
`component represents the state of the hean (center). and the
`telesystolic component represents the state of the periphery.
`
`in this embodiment. therefore. the condition that at
`[0038]
`least one of the presystolic component or telesystolic com—
`ponent fluctuates by an amount exceeding a predetermined
`amount from the value of the presystolic component or
`
`009
`
`FITBIT, Ex. 1035
`
`

`

`US 2007f0016086 Al
`
`Jan. 18, 2007
`
`010
`
`(1) Both the pulse wave parameter and estimated
`[0058]
`blood pressure are continuously found to be abnormal for
`a predetermined period.
`[0059]
`(2} A predetermined time has elapsed since the last
`culT blood pressure measurement.
`[0060]
`If one of these conditions is met. the controller 100
`controls the pump 14 to raise the pressure of the coil [0.
`monitors the input signal from the pressure sensor 12 while
`gradually exhausting the air after avascularization. and cal~
`culates the highest blood pressure. average blood pressure.
`and lowest blood pressure on the basis of the wellAknown
`oscillometric method. The controller 100 also stores. in the
`storage unit 90.
`the waveform parameters and estimated
`blood pressure obtained immediately before the blood pres-
`sure measurement using the cull 10. and uses them in
`calibration of the coeflicients o. and [3 contained in the
`equation for calculating the estimated blood pressure and in
`processing after that. Note that during the cod blood pres—
`sure measurement. the wavetbrm parameter calculation and
`determination process in steps 31]] to $115 and the esti-
`mated blood pressure calculation process ln steps 8121 to
`5125 are interrupted. or the results are ignored.
`
`ence calculated value obtained in the last cutlblood pressure
`measurement. Note also that the threshold values Thb and
`Thd indicating normal ranges can be either equal or indiw
`vidually set. In addition. the fluctuation need not be absolute
`values. and it is also possible to individually set the thresh-
`old value (ripper limit) on the increasing side and the
`threshold value (lower limit) on the decreasing side. Prac-
`tical values of the threshold values can be appropriately
`determined. For example, 'l‘hb='I'hd=20(%) can be set in
`inequalities (la) and (lb).
`
`It is also possible to dynamically change the thresh—
`[0045]
`old values in accordance with the results ot'periodical blood
`pressure measurements using a cull For example. if the
`result of cull~ blood pressure measurement is smaller than a
`predetermined value.
`it
`is possible to make the threshold
`value on the decreasing side stricter (make the threshold
`value easier to exerted) than when the measurement result is
`not smaller than the predetennined value. thereby monitor—
`ing the decrease in blood pressure more strictly. More
`specifically, when the normal range is defined by the upper
`and lower limits. the lower limit is set to be high. In this
`case.
`tlte lower limit becomes easier to exceed. so the
`decrease in blood pressure can be strictly monitored. On the
`contrary. if the CUITIHCEISUI'EIIIEIIL result is large. it is possible
`to make the threshold value on the increasing side stricter
`(make the upper limit of the normal range smaller).
`
`[0046] The fluctuation amount need not be a ratio (per-
`centage). but may also be a difference.
`[0047]
`If the fluctuation amount is found to be abnormal in
`step $115. the flow advances to step $130. If the lluctualion
`amount is found to be normal in step 8115, the flow returns
`to step 311] to continue the processing for the next heart
`beat.
`
`In steps 812] to $125. the same blood pressure
`[0048]
`estimating process as the conventional method is executed.
`
`In step 312], the pulse wave propagation time is
`[0049]
`calculated on the basis of an ECG detected by the electro~
`cardiogranr electrode 20 and a plethysmograph sensed by
`the. finger sensor 30. More specifically. the controller 100
`performs signal proceSsing such as noise removal and wave-
`form shaping normally performed on an ECG and plethys-
`mograph. and calculates the time difference between feature
`points in the heart beats of the ECG and plethysmograph as
`the pulse wave propagation velocity, In this case. the feature
`point of the ECG can be. e.g.. the peak position of the R
`wave. and the feature point of the plethysmograph can be the
`leading edge of the waveform. Also. as described above.
`there is a time ditfercnce (prcelection period) between the
`appearance of the R wave to the generation of tire actual
`pulse wave. Therefore. correction can be performed by
`subtracting a time corresponding to a preejection period
`statistically calculated beforehand from the time difl'erence
`between the feature points.
`
`In step 3123. an estimated blood pressure is
`[0050]
`obtained from the calculated pulse wave propagation time.
`[0051] That is. an estimated blood pressure is calculated
`by applying the pulse wave propagation time to
`Estirrutcd blood pressure‘crxtpulsc wave propagation
`{2)
`time [msec]t+[l
`(or and B are coefficients. CI<0. [330) as disclosed in. e.g..
`Japanese Patent Laid-Open No. 10-66681.
`
`[0052] Note that the coefficients 0. and [i need only be
`determined in advance. That is. this equation is a linear
`equation with two unknowns. so the values of the coefliw
`cients or and |i can be detcnnined by using at least two
`actually measured blood prettsnres and the corresponding
`pulse wave propagation times.
`
`[0053] Each coeflicient need not be fixed but may also be
`updated to an optimum value by using an actually measured
`value obtained by another method (cull measurement or
`direct measurement) and the pulse wave propagation time at
`the corresponding timing.
`
`In step 8125. whether the estimated blood pressure
`[0054]
`is an abnormal value is determined. This detenninatiori can
`be perfonned by determining whether the estimated blood
`pressure is larger than the ripper limit or smaller than the
`lower limit of a predetermined normal range. or determining
`whether the estimated blood pressure lluctuatcs more than a
`prEdetermined amount (which can be either a fluctuation
`ratio or diflemilcc) from the value of the last cull blood
`pressure measurement.
`
`[0055] Like the threshold values of the wavefonn param-
`eters. these upper limit. lower limit. arid fluctuation amount
`can be either fixed with respect to the value of cuff blood
`pressure measurement, or dynamically changed in accor—
`dance with practical measured values.
`
`If the estimated blood pressure is found to be
`[0056]
`abnormal in step $125. the flow advances to step 5130. It'the
`estimated blood pressure is found to be normal in step 3125.
`the flow returns to step 8121 to continue the processing for
`the next heart beat.
`
`In step 3130. whether the conditions tor executing
`[0057]
`cufl‘ blood pressure measurement are satisfied is determined.
`That is. whether one of the following conditions is met is
`determined.
`
`[006]] After that. the above processing is repeated tuttil
`the termination of monitoring is designated.
`
`1"1G. 4 is a graph showing the relationship between
`[0062]
`an estimated blood pressure continuously calculated by the
`
`010
`
`FITBIT, Ex. 1035
`
`

`

`US 2007f0016086 A1
`
`Jan. 18, 2007
`
`blood pressure measuring apparatus of this embodiment. a
`direct blood pressure measured invasively. and waveform
`parameters.
`[0063] Referring to FIG. 4. ESYS indicates the estimated
`blood pressure calculated on the basis of the pulse Wave
`propagation time, and ISYS indicates the direct blood pres-
`sure measured invasively. The straight lines drawn above
`and below these blood pressures indicate values which are
`+20% and —20%. respectively. from culf measurement val—
`ues when cufl~ measurement is performed at times 1!}. ti. and
`t2.
`
`is. FIG. 4 shows the direct blood pressure
`[0064] That
`measured invasiver
`in order to show the relationship
`between the estimated blood pressure and the actual blood
`pressure. but no invasive measurement is performed by the
`actual blood pressure tttottilot‘ittg apparatus (if direct mea-
`surement is performed, blood pressure estimation itsnlfhas
`no meaning). ht practice. culf measurement is periodically
`performed. and. during a period in which no cuff blood
`pressure measurement
`is performed. monitoring is per-
`fomied using the estimated blood pressure based on the
`pulse wave propagation time. FIG. 4 shows the case in
`which the last cuff blood pressure measurement values
`s20% are used as the threshold values for determining
`whether the estimated blood pressure can be regarded as a
`normal value.
`
`value.
`
`FIG. 4 also shows whether the waveform parath-
`[0065]
`eters bio and d/a have exceeded the threshold values by
`EPAIi OVER and DPA1 3 OVER. respectively.
`[0066]
`In FIG. 4. between times t0 and t1. the waveform
`parameter (b/a] sometimes indicates an abnonual value.
`However. no cuff activation is performed because the esti-
`mated blood pressure falls within the normal range. and
`periodic cufl' blood pressure measurement is performed at
`time tl alter a predetermined time has elapsed sincetirne I0.
`[0067] After time I]. the estimated blood pressure exceeds
`the lower limit and upper limit in some periods. but both the
`two waveform parameters have normal values. so no cufl'
`activation is performed either. After that. however. both the
`estimated blood pressure and the wavefomt parameter (b/a)
`show abnormal values. so cufl blood pressure measurement
`is executed at time 12. Since (tl—tD]>(I2—tl], the cufi‘ acti-
`vation at time t2 is shorter than the periodic interval.
`[0068] After time t2. the waveform parameter shows an
`abnormal value fora while. but the estimated blood pressure
`falls within the normal range. so no cufi' activation is
`performed.
`[0069] As shown in FIG. 4. the blood pressure monitoring
`apparatus of this embodiment detemlines the presencet'
`absence of the true fluctuation in blood pressure by using the
`values of the parameters obtained from the accelerated pulse
`wave and indicating the state of the blood vessel, in addition
`to the estimated blood pressure calculated on the basis of the
`pulse wave propagation time obtained from an ECG and
`pulse wave. Accordingly. the necessity of cufl' blood pres-
`sure measurement can be deter-ruined more accurately than
`the conventional methods.
`
`[007]] As described above. when the result of