as) United States
`a2) Patent Application Publication (10) Pub. No.: US 2002/0095092 Al
`(43) Pub. Date: Jul. 18, 2002
`
`Kondoetal.
`
`US 20020095092A1
`
`(54) PULSE WAVE MEASURING APPARATUS
`AND PULSE WAVE MEASURING METHOD
`
`(30)
`
`Foreign Application Priority Data
`
`(75)
`
`Inventors: Shinji Kondo, Kariya-shi (JP); Toru
`Takemoto, Toyota-shi (JP); Toshihiro
`Honda, Toyota-shi (JP); Noriaki
`Sakakibara, Kariya-shi (JP)
`
`Correspondence Address:
`OBLON SPIVAK MCCLELLAND MAIER &
`NEUSTADT PC
`FOURTH FLOOR
`1755 JEFFERSON DAVIS HIGHWAY
`ARLINGTON,VA 22202 (US)
`
`(73) Assignee: KABUSHIKI GAISYA K-AND-S,
`Kariya-shi (JP)
`
`(21) Appl. No.:
`
`10/004,431
`
`(22)
`
`Filed:
`
`Dec. 6, 2001
`
`Dec. 6, 2000
`
`(IP) wee tecessessessseceteessesneenne 2000-371370
`
`Publication Classification
`
`Tint. C7 eeeeeeccceccceeeeeeseeenneeeeceesnnesecenneeeee A61B 5/02
`(SV)
`(52) U.S. C1. eee ecssseseecsecnecneeeneess 600/503; 600/490
`
`(57)
`
`ABSTRACT
`
`,
`:
`A maximum blood pressure and a minimum blood pressure
`are first measured using an oscillometric method. Pulse
`waves of a vessel occurring during the measurement are
`measured by a reflection-type photoelectric sensor. The
`maximum and minimum blood pressures and the pulse
`waves occurring at the times of maximum and minimum
`blood pressures are associated with each other. After that,
`the blood pressure is calculated from the associated values
`and the pulse waves of the vessel serially detected by the
`reflection-type photoelectric sensor.
`
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`1
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`

`

`Patent Application Publication
`
`Jul. 18, 2002 Sheet 1 of 15
`
`US 2002/0095092 Al
`
`FIG. 1
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`Patent Application Publication
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`Jul. 18, 2002 Sheet 2 of 15
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`US 2002/0095092 Al
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`Patent Application Publication
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`Jul. 18,2002 Sheet 3 of 15
`
`US 2002/0095092 Al
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`FIG. 3
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`Jul. 18, 2002 Sheet 4 of 15
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`Patent Application Publication
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`Jul. 18,2002 Sheet 5 of 15
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`US 2002/0095092 Al
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`FIG. 5A
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`Patent Application Publication
`
`Jul. 18,2002 Sheet 6 of 15
`
`US 2002/0095092 Al
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`FIG. 6
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`7
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`

`Patent Application Publication
`
`Jul. 18,2002 Sheet 7 of 15
`
`US 2002/0095092 Al
`
`FIG. 7
`
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`

`

`Patent Application Publication
`
`Jul. 18, 2002 Sheet 8 of 15
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`Patent Application Publication
`
`Jul. 18,2002 Sheet 9 of 15
`
`US 2002/0095092 Al
`
`FIG. 9
`
`$100
`
`START
`
`$110
`
`INPUT CUFF PRESSURE,
`PRESSURE PULSE WAVES
`
`$120
`
`MEASURE REFERENCE MAXIMUM/MINIMUM
`BLOOD PRESSURES, PULSE RATE
`
`S130
`
`CALCULATE REFERENCE BLOOD
`PRESSURE AREA(Ax)
`
`$140
`
`$150
`
`BODY MOTION PROCESS
`OF PULSE WAVES
`
`INPUT PULSE WAVES
`
`|
`
`S160,
`
`-
`
`CALCULATE PULSE
`AREA(Vs)
`
`$170
`
`$180
`
`$190
`
`CALCULATE AREA
`RATIO (Ax/Vs)
`
`DETECT PULSE WAVES
`
`CALCULATE CORRECTED
`PULSE AREA
`
`200
`
`s
`
`CALCULATE MAXIMUM/MINIMUM
`
`BLOOD PRESSURES
`
`$210
`
`10
`
`

`

`Patent Application Publication
`
`Jul. 18,2002 Sheet 10 of 15
`
`US 2002/0095092 A1
`
`FIG. 10
`
`BLOOD
`
`Pyg be
`
`CUFF PRESSURE
`
`PRESSURE
`eneeePeee
`
`
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`
`PULSE WAVE
`
`TIME
`
`11
`
`

`

`Patent Application Publication
`
`Jul. 18,2002 Sheet 11 of 15
`
`US 2002/0095092 A1
`
`
`
`SINGLE STROKE Tx
`
`12
`
`

`

`Patent Application Publication
`
`Jul. 18,2002 Sheet 12 of 15
`
`US 2002/0095092 A1
`
`FIG. 12
`
`BLOOD
`FLOW
`
`SINGLE STROKE Tx
`
`TIME
`
`13
`
`

`

`Patent Application Publication
`
`Jul. 18,2002 Sheet 13 of 15
`
`US 2002/0095092 A1
`
`FIG. 13
`
`$300
`
`$310 Ga
`
`S320
`
`YES
`
`
`START CUFF PUMP
`
`
`APPLY CUFF PRESSURE
`DETECT CUFF PRESSURE
`
`DETECT PRESSURE PULSE WAVE
`
`
`
`
`
`
`AQuiRE REFERENCE PULSE WAVE,
`REFERENCE BODY MOTION LEVEL
`
`
`CALCULATE BLOOD PRESSURE
`COUNT FROM REFERENCE PULSEWAVE
`
`
`$340
`
`S350
`
`PRESSURE
`
`HECK PRESSUR
`PULSE WAVE
`
`YES
`
`CALCULATE REFERENCE MAXIMUM BLOOD
`PRESSURE VALUE,MINIMUM BLOOD PRESSURE VALUE
`
`S360]
`
`$370
`
`
`
`
`
`ABNORMAL BLOOD
`PRESSURE?
`
`
`NO
`
`OUTPUT PULSE WAVE FOR DATA DISPLAY
`
` PULSE WAVE
`REGENERATING
`PROCESS
`
`14
`
`

`

`Patent Application Publication
`
`Jul. 18, 2002 Sheet 14 of 15
`
`US 2002/0095092 Al
`
`
`
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`

`

`Patent Application Publication
`
`Jul. 18,2002 Sheet 15 of 15
`
`US 2002/0095092 A1
`
`FIG. 15
`
`S500
`
`COMPLETE APPLICATION
`
`OF CUFF PRESSURE
`
`S510
`
`PROCESSING OF DETECTING REFERENCE
`
`PULSE WAVE AFTER PULSE WAVES STABILIZE
`
`$520
`
`DETERMINE HYPOTHETICAL FLOW
`
`SPEED OF BLOOD FLOW SPEED
`
`S530\_/—CAreuLATE VESSEL INSIDE
`WALL DIAMETER
`
`S540
`
`CALCULATE RELATIVE AMOUNT
`OF BLOOD FLOW PER STROKE
`
`S550
`
`S560
`
`CALCULATE CORRECTION FACTOR FROM
`_ MEASURED BLOOD FLOW PARAMETER
`
`CALCULATE STROKE MASS, APPROXIMATE
`AMOUNT OF BLOOD FLOW PER STROKE
`
`$570
`
`OUTPUT WAVEFORMS OF STROKE MASS,
`AMOUNT OF BLOOD FLOW FOR DATA DISPLAY
`
`16
`
`16
`
`

`

`US 2002/0095092 Al
`
`Jul. 18, 2002
`
`PULSE WAVE MEASURING APPARATUS AND
`PULSE WAVE MEASURING METHOD
`
`INCORPORATION BY REFERENCE
`
`[0001] The disclosure of Japanese Patent Application No.
`2000-371370 filed on Dec. 6, 2000 including the specifica-
`tion, drawings and abstract is incorporated herein by refer-
`ence in its entirety.
`
`BACKGROUND OF THE INVENTION
`
`[0002]
`
`1. Field of the Invention
`
`[0003] The invention relates to a pulse wave measuring
`apparatus and a measuring method thereof
`
`[0004]
`
`2. Description of the Related Art
`
`[0005] A typical technique of measuring measuring blood
`pressure pulse waves is a pressure pulse wave vibration
`method termed an oscillometric method. In this method,
`after a cuff wrapped arounda finger tip or an arm is supplied
`with air so as to compress the blood vessels,
`the blood
`pressure is measured during a decompressing process. On
`the basis of changes in the values of blood pressure deter-
`mined by repeating the above-described operation a plurality
`of times, a pulse wave is measured. However, in the above-
`described construction, a finger or an arm is repeatedly
`compressed, and so blood flow is repeatedly stopped in the
`thus-compressed portion. Therefore, a lengthy measurement
`may becomea burden onthe patient. Furthermore, since the
`blood pressure fluctuates depending on the ambient envi-
`ronment and the internal state of the patient’s body, there
`also is a danger of an inaccurate measurements result due to
`patient movements.
`
`SUMMARYOF THE INVENTION
`
`is an object of the invention to
`it
`[0006] Accordingly,
`provide a pulse wave measuring apparatus capable of accu-
`rately measuring stable pulse waves continuously for a long
`time without imposing a burden ona patient.
`
`[0007] Specifically, an aspect of the invention is a pulse
`wave measuring apparatus that
`includes a photoelectric
`sensor having a light-emitting portion that emits a light to a
`vessel under the skin of a patient and a light-receiving
`portion that receives reflected light from the vessel, a blood
`pressure meter that measures the blood pressure of the
`patient, and a control portion that measures, as a pulse wave,
`a time-dependent changeof a state of the vessel based on the
`reflected light.
`
`[0008] Furthermore, in the pulse wave measuring method
`of the invention, light is emitted to a vessel under the skin
`of a patient, and reflected light from the vessel is received.
`The blood pressure of the patient is measured. A time-
`dependent change of a state of the heart or the vessel is
`measured, as a pulse wave, based on the reflected light.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0009] The foregoing and further objects, features and
`advantages of the invention will become apparent from the
`following description of preferred embodiments with refer-
`ence to the accompanying drawings, wherein like numerals
`are used to represent like elements and wherein:
`
`[0010] FIG. 1 is a perspective view illustrating a state
`where a pulse wave measuring apparatus in accordance with
`a first embodimentof the invention is attached to a wrist of
`a patient;
`
`[0011] FIG. 2 is a sectional view of the pulse wave
`measuring apparatus of the first embodiment;
`
`FIG.3 is a plan view illustrating an arrangement of
`[0012]
`light-emitting portions andlight-receiving portions in accor-
`dance with the first embodiment;
`
`[0013] FIG. 4 is a block diagram schematically illustrat-
`ing the electronic layout of the pulse wave measuring
`apparatus of the first embodiment;
`
`[0014] FIGS. 5A and 5B are sectional views of a wrist
`illustrating a relationship between an arterial vessel and a
`reflection-type photoelectric sensor of the pulse wave mea-
`suring apparatus of the first embodiment;
`
`[0015] FIG. 6 isa conceptual diagram indicating results of
`output of a monitor in accordance with the first embodiment;
`
`[0016] FIG. 7 is a schematic illustration of an apparatus
`for realizing a pulse wave measuring method in accordance
`with a second embodimentof the invention;
`
`[0017] FIG. 8 is a block diagram schematically illustrat-
`ing an electronic layout of a pulse wave measuring apparatus
`in accordance with the second embodiment;
`
`[0018] FIG. 9 is a flowchartillustrating a blood pressure
`measuring procedure in the second embodiment;
`
`[0019] FIG. 10 is a waveform diagram indicating the cuff
`pressure and the pressure pulse wave in an oscillometric
`method;
`
`[0020] FIG. 11 is a diagram indicating a blood pressure
`area;
`
`(0021] FIG. 12 is a diagram indicating a pulse wave area;
`
`[0022] FIG. 13 is a flowchartillustrating a blood pressure
`measuring procedure;
`
`[0023] FIG. 14 is a flowchart illustrating a pulse wave
`complementing procedure; and
`
`[0024] FIG. 15 is a flowchart illustrating a procedure of
`calculating the amount of flow of blood.
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`
`[0025] A preferred embodiment of the invention will be
`described hereinafter with reference to FIGS. 1 to 6. First, a
`construction of the invention will be described. As shown in
`
`FIG. 1, a pulse wave measuring apparatus in accordance
`with the embodiment has a control portion 11 and a mea-
`suring portion 12 in a wristband 10. The wristband 10 has
`two end portions that are interconnectable, as in a watch-
`band. The entire pulse wave measuring apparatus is wrapped
`in an annular fashion around a wrist, with the two end
`portions of the wristband 10 being connected.
`
`[0026] The control portion 11 has a flat rectangular par-
`allelepiped shape. The control portion 11 has a monitor 11A
`on an obverse side, and has in a side surface various
`operating switches SW and a piston PT for injecting air into
`a cuff 20 described below.
`
`17
`
`17
`
`

`

`US 2002/0095092 Al
`
`Jul. 18, 2002
`
`[0027] The measuring portion 12 is connected to the
`control portion 11 via an accordion-like connecting portion
`12A. The pulse wave measuring apparatus is attached to a
`subject’s wrist so that the measuring portion 12 contacts a
`portion of the wrist where an arterial vessel extends. More
`specifically, as shown in FIG.2, the measuring portion 12
`has a plate member 15 that is disposed within a case portion
`14 having an opening in a surface that contacts the wrist. The
`plate member 15 is slidably mounted at a position at which
`the plate member 15 closes the opening of the case portion
`14 and a receded back wall of the case portion 14. The plate
`member15 is always urged toward the opening side of the
`case portion 14 by a compressed coil spring 16 provided
`between the plate member 15 and the back wall of the case
`portion 14.
`
`[0028] Therefore, the plate member 15 is pressed against
`a patient’s wrist. The elastic restoration force of the com-
`pressed coil spring 16 is set to such a magnitude that the
`blood stream in the arterial vessel will not be stopped.
`
`[0029] The plate member 15 has a plurality of through-
`holes. LEDs as light-emitting portions 17 of a reflection-
`type photoelectric sensor 13, and photo-diodes as light-
`receiving portions 18 of the reflection-type photoelectric
`sensor 13 are fixed to the through-holes of the plate member
`15 so as to face toward the opening side of the case portion
`14.
`
`input port of the CPU 23. The pressure sensor 21 and the
`light-receiving portions 18 are connected to input terminals
`of the multiplexer 24 via an A/D converter 25 and an
`amplifier 26. One of an output signal of the pressure sensor
`21 and an output signal of the light-receiving portions 18 is
`appropriately selected by the multiplexer 24,and is inputted
`to the CPU 23. A result of data processing of the CPU 23 is
`displayed on the monitor 11A connected to an output port of
`the CPU 23.
`
`[0034] An output port of the CPU 23 is connected to an
`amount-of-light adjuster 29 and a level adjuster 28 via a D/A
`converter 27. The amount of light from the light-emitting
`portions 17 is adjusted based on the output signal of the
`amount-of-light adjuster 29. The gain of the output amplifier
`26 of the light-receiving portions 18 is adjusted by an output
`signal of the level adjuster 28. The pulse wave measuring
`apparatus starts operating upon a signal from the switch SW.
`
`[0035] Next, an operation of the embodiment constructed
`as described above will be described. First described will be
`a methodof setting the pulse wave measuring apparatus for
`operation. The pulse wave measuring apparatus is attached
`to a wrist or a forearm ofa patient by using the wristband 10
`in such a mannerthat the light-emitting portions 17 and the
`light-receiving portions 18 of the reflection-type photoelec-
`tric sensor 13 contact a portion of the wrist or the forearm
`where an arterial vessel extends (see FIG.2).
`
`[0030] A drive circuit for driving the light-emitting por-
`tions 17 and a reception circuit for processing output signals
`of the light-receiving portions 18 are provided in,
`for
`example, a control circuit baseboard (not shown) that is
`disposed in the control portion 11. The reflection-type pho-
`toelectric sensor 13 is formed by the drive circuit,
`the
`reception circuit,
`the light-emitting portions 17 and the
`light-receiving portions 18. The control circuit baseboard is
`connected with the light-emitting portions 17 and the light-
`receiving portions 18 by electric cables (not shown)thatare
`excellent in flexibility, so that the plate member 15 can be
`slid.
`
`[0036] Subsequently, using a switch SW provided on a
`side surface of the control portion 11,
`the pulse wave
`measuring apparatus is powered on. Upon the powering-on
`operation, the light-emitting portions 17 of the reflection-
`type photoelectric sensor 13 emit light having a wavelength
`of 600 to 800 nm to the patient’s skin. As shown in FIGS.
`5A and 5B, light passes through the patient’s skin, and
`strikes an outer peripheral surface of an arterial vessel 90 in
`the wrist. Light is reflected from the outer peripheral surface
`of the arterial vessel 90, and is received by the light-
`receiving portions 18 of the reflection-type photoelectric
`sensor 13. In response, the light-receiving portions 18 output
`a light-reception signal that has a magnitude corresponding
`In the pulse wave measuring apparatus, the cuff 20
`[0031]
`to the distance between the reflection-type photoelectric
`having a tube-like shape extends along an upper peripheral
`sensor 13 and the arterial vessel 90. The light-reception
`edge portion in FIG.2. The cuff 20 has an air injection hole
`signal is inputted to the CPU 23 via the amplifier 26 and the
`like.
`in the control portion 11. By using the piston PT (see FIG.
`1) protruded fromaside surface ofthe control portion 11,air
`[0037] As the arterial vessel 90 pulsates in accordance
`is injected into the cuff 20. Thus, the cuff 20 is expanded to
`with the pulsation of the heart, the distance between the
`constrict the entire wrist. The wrist-constricting pressure
`reflection-type photoelectric sensor 13 and the arterial vessel
`from the cuff 20 is measured by a pressure sensor 21 thatis
`90 changes as indicated by FIGS. 5A and 5B. In accordance
`provided as a blood pressure meter (described below) in the
`with such a change in the distance,
`the amount of light
`control portion 11.
`received by the light-receiving portions 18 changes, and
`therefore, the magnitude of the light-reception signal out-
`putted from the light-receiving portions 18 also changes.
`The CPU 23 determines that the pulse wave measuring
`apparatus has been properly attached when, for example, it
`detects periodical fluctuations of the light-reception signal
`outputted from the light-receiving portions 18.
`
`[0032] The arrangementof the light-emitting portions 17
`and the light-receiving portions 18is illustrated in detail in
`FIG. 3. The light-receiving portions 18 are disposed as a
`pair in a central portion of the plate member 15. The
`light-emitting portions 17 are disposed at four positions that
`are equidistantly present on a circle aroundthe light- receiv-
`ing portions 18. Two of the light-emitting portions 17 are
`[0038] Next described will be a procedure of measuring
`disposed onaline extending through the two light-receiving
`pulse waves. First, an operation instruction, for example,
`portions 18.
`“OPERATE PISTON TO RAISE CUFF PRESSURE?”orthe
`
`[0033] The block diagram of FIG. 4 schematically illus-
`trates the electronic layout of the pulse wave measuring
`apparatus. As shown in FIG.4, the pulse wave measuring
`apparatus has a CPU 23. A multiplexer 24 is connected to an
`
`like, is displayed on the monitor 11A. When the piston PT
`is accordingly operated, the cuff 20 is supplied with air, and
`is gradually inflated. As the air injection into the cuff 20 is
`continued, the light-reception signal output from the light-
`
`18
`
`18
`
`

`

`US 2002/0095092 Al
`
`Jul. 18, 2002
`
`receiving portions 18 stops fluctuating. This means a
`stopped-bloodstream state, that is, a state where the arterial
`vessel 90 is compressed to stop pulsating by expansion of
`the cuff 20. The blood pressure present during this state is
`measured by the pressure sensor 21. The measured valueis
`inputted to the CPU 23 via the amplifier 26 or the like, and
`is stored as a maximum blood pressure in a memory (not
`shown). Furthermore, the light-reception signal at the time
`of measurement of the maximum blood pressure value is
`also stored in the memory (not shown) as a signal corre-
`sponding to the maximum blood pressure. The maximum
`blood pressure and the signal corresponding to the maxi-
`mum blood pressure are associated with each other by the
`CPU 23. After the mode is switched to a continuous mea-
`surement mode described below,
`the CPU 23 is able to
`calculate a blood pressure value based only on the output
`signal from the light-receiving portions 18, by using the
`associated values.
`
`[0039] Next, when the force by which the cuff 20 com-
`presses the arterial vessel 90 (hereinafter, referred to as “cuff
`pressure”) is increased to a predetermined value(e.g., about
`200 mmHg), an instruction, for example, “END PISTON
`OPERATION”orthe like, is displayed on the monitor 11A.
`After the piston operation is ended, air is discharged from
`the cuff 20. As air is discharged, the cuff pressure gradually
`decreases. During the decrease in the cuff pressure,
`the
`light-reception signal output of the light-receiving portions
`18 starts to fluctuate again. This means the bloodstream
`blockage is removed. The blood pressure present at this time
`is also measured by the pressure sensor 21. The CPU 23
`stores a result of the measurement as a minimum blood
`pressure in the memory. Furthermore,
`the light-reception
`signal from the light-receiving portions 18 corresponding to
`the minimum bloodpressure is also stored in the memory.
`The minimum blood pressure and the light-reception signal
`corresponding to the minimum blood pressure are associated
`with each other by the CPU 23.
`
`[0040] After the maximum blood pressure and the mini-
`mum blood pressure are stored in the memory, the pulse
`wave measuring apparatus,
`for example, automatically
`switches to the continuous measurement mode. Then, the
`light-receiving portions 18 start to continuously detect the
`pulsation of the arterial vessel 90. As indicated in FIG.6,
`time-dependent changes of the light-reception signal out-
`putted from the light-receiving portions 18 are displayed in
`the form of a graph on the monitor ILA. The CPU 23
`determines a maximum value and a minimum value of pulse
`wavesfor every heart beat (stroke), and calculates a maxi-
`mum blood pressure and a minimum blood pressure for
`every heart beat based on the aforementioned associated
`values, and display the calculated values on the monitor 11A
`(as indicated by H1 in FIG. 6). The CPU 23 counts the
`number of fluctuations of pulse waves measured, and cal-
`culates the heart rate in terms of beats per minute, and
`outputs it on the monitor (as indicated by H2 in FIG.6).
`After that, the CPU 23 repeatedly acquires light-reception
`signals from the light-receiving portions 18, and displays the
`results of the calculation on the monitor 11A. Then, by
`checking the graph of the pulse waves, the blood pressure
`values and the heart rate displayed on the monitor 11A,the
`physical condition of the patient is diagnosed.
`
`[0041] The magnitude or degree of the pulsation of a
`vessel may greatly vary, for example, between a condition in
`
`which a patient is under anesthesia and a condition in which
`the anesthetic effect has come to an end. Therefore, for
`example,
`if the amplification factor of the pulse wave
`measuring apparatus is fixed in accordance with a state in
`which the pulse waves are small under anesthesia,
`the
`light-reception signal output from the light-receiving por-
`tions 18 may become excessively great and the light-
`reception signal may exceed an appropriate range when the
`anesthetic effect ends and pulse waves becomegreat. Taking
`these points into consideration, the pulse wave measuring
`apparatus of this embodimentis designed so that the CPU 23
`drives and controls the amount-of-light adjuster 29 and the
`level adjuster 28 so that
`the output signal of the light-
`receiving portions 18 will not exceed the maximum value
`and the minimum value of the appropriate range. Thatis, the
`CPU 23 drives the amount-of-light adjuster 29 to adjust the
`amountof light emitted by the light-emitting portions 17 in
`accordance with the output signal of the light-receiving
`portions 18. Furthermore,
`the CPU 23 drives the level
`adjuster 28 to adjust the amplification factor of the amplifier
`26 related to the light-reception signal from the light-
`receiving portions 18. Therefore,
`it becomes possible to
`continuously and stably measure pulse waves from the state
`where the patient is under anesthesia to the state where the
`anesthetic effect ends.
`
`[0042] According to this embodiment, the compression of
`a patient’s wrist is performed only when the maximum
`blood pressure and the minimum blood pressure are mea-
`sured in order to associate the blood pressure and the
`pulsation with each other. After that, the measurementof the
`blood pressure is performed by repeatedly detecting pulse
`waves from the state of pulsation of the vessel by the
`reflection-type photoelectric sensor 13, and continuously
`calculating the blood pressure using the associated values.
`Therefore, the burden on a patient is reduced in comparison
`with a conventional pulse wave measuring apparatus that
`repeatedly compresses a vessel. Furthermore, unlike the
`conventional art in which a vessel is compressed directly by
`a cuff for detection of pulse waves, the pulse wave measur-
`ing apparatus of the embodiment measures pulse waves in
`an indirect manner based on reflection of light. The pulse
`wave measurement in accordance with the embodimentis
`
`less likely to be affected by movements of a patient, and
`therefore can be stably performed. Still further, the pulse
`wave measuring apparatus can be fixed to a wrist or a
`forearm by the wristband 10, and the blood-pressure meter
`(the cuff 20, the measuring portion 12, etc.) is integrally
`provided. Therefore, the operation of associating fluctua-
`tions of pulse waves with the maximum blood pressure and
`the minimum blood pressure can easily be performed.
`
`[0043] Second Embodiment
`
`[0044] A second embodiment of the invention will be
`described with reference to FIGS. 7 to 12. FIG. 7 shows a
`cuff 31 that is attachable to, for example, a wrist. The cuff
`31 contains a rubber bag. The rubber bag is connected to an
`air-supplying pump 32 via a tube. An on-off valve 33 is
`provided in an intermediate portion of the tube. In accor-
`dance with the opening and closing actions of the on-off
`valve 33, air can be supplied to and discharged from the
`rubber bag provided in the cuff 31. Further provided within
`the cuff 31 is a pressure sensor 34 as a blood-pressure meter
`for detecting fluctuations in air pressure in the rubber bag.
`
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`The pressure sensor 34 is connected to a control unit 35
`provided as a control portion.
`
`[0045] A light-emitting sensor 36 is provided at a side of
`the cuff 31. The light-emitting sensor 36 includes a photo-
`electric sensor 37 and a body motion sensor 38 disposed
`adjacent to the photoelectric sensor 37.
`
`[0046] FIG. 8 is a block diagram schematically illustrat-
`ing an electronic layout of a measuring apparatus in accor-
`dance with this embodiment. The photoelectric sensor 37 is
`formed by a red-light LED (infrared-emitting portion 37a)
`that emits infrared light having a near-infrared wavelength
`(e.g., 640 nm) to the skin, and a phototransistor (light-
`receiving portion 37b) that receivesa reflected light. Emitted
`infrared light passes through a skin surface and reaches a
`radial artery or a forearm artery located in a deep portion of
`the skin. Infrared reflected from the radial artery or the
`forearm artery is received bythe light-receiving portion 37b,
`which outputs a signal. From the output signal of the
`light-receiving portion 37b, changes in light absorbance
`caused by volume fluctuations of the radial artery or the
`forearm artery can be obtained as relative changes in the
`amountof blood flow.
`
`[0047] The body motion sensor 38 is formed by a blue-
`light LED (blue light-emitting portion 38a) capable of
`emitting light having an ultra-blue wavelength (e.g., 420
`nm) to the skin, and a phototransistor (light-receiving por-
`tion 38b) that receives reflected light. Ultra-blue light is
`reflected from a skin surface, and is received by the light-
`receiving portion 38b. From an output signal of the light-
`receiving portion 38b, minute movements of the patient
`(body motions) detected by the reflected light during the
`measurement can beattained.
`
`[0048] The pressure sensor 34 in the cuff 31 is connected
`to a low-passfilter 39, and is connected to a high-passfilter
`40. Therefore, the output signal from the pressure sensor 34
`is processed by the low-passfilter 39 and the high-passfilter
`40 so that predetermined frequency componentsare cut off.
`Then,
`the output signal
`is inputted to a CPU 43 via a
`multiplexer 42. The photoelectric sensor 37 is connected to
`a high-pass filter 46, and is connected to a pulse wave
`correcting circuit 47 described below, via an amplifier 44
`and a low-passfilter 45. The low-pated to the photoelectric
`sensor 37 cuts off a frequency component equal to or lower
`than 30 Hz in order to remove low-frequency components,
`including body motions andthe like, from the output signal
`from the light-receiving portion 37b. The high-pass filter 46
`is designed so as to cut off a predetermined high-frequency
`component (equal to or higher than 150 Hz). The body
`motion sensor 38 is connected to an active filter 49 via an
`
`45, the high-pass filters 40, 46, the pulse wave correcting
`circuit 47, the activefilter 49, an automatic amount-of-light
`adjuster 51, and an automatic gain adjuster 52.
`
`[0051] An operation executed by the CPU 43is illustrated
`by the flowchart of FIG. 9. First, the pulse wave and the
`blood pressure are associated with each other for pulse wave
`measurement. That is, after a cuff pressure (blood pressure)
`and a pressure pulse waveare inputted (S110), the absolute
`values of a pulse rate and maximum and minimum blood
`pressures that serve as references at a predetermined timing
`are measured based on the cuff pressure and the pressure
`pulse wave (S120). The maximum and minimum blood
`pressure values are determined by an oscillometric method.
`
`[0052] The oscillometric method will be briefly described
`with reference to FIG. 10. Vibrations of a vessel wall
`synchronouswith beats of the heart are reflected as fluctua-
`tions in the cuff pressure (pressure pulse waves). First, the
`cuff pressure is raised until the pressure pulse waves of a
`patient disappear (becomeconsiderably small). After that, as
`the cuff pressure is gradually reduced, pressure pulse waves
`appear(or rapidly becomegreat). The blood pressure occur-
`ring at that time is determined as a maximum bloodpressure
`(Pxs in FIG. 10). As the cuff pressure is further reduced,
`pressure pulse waves disappear again (or rapidly become
`small). The blood pressure occurring at that time is deter-
`mined as a minimum blood pressure (Pxd in FIG. 10).
`
`[0053] Next, a blood pressure area (reference blood pres-
`sure area Ax) at the time of attainment of the reference
`maximum and minimum bloodpressure valuesis calculated
`(S130). The reference blood pressure area is determined by
`an area of a plane figure determined by maximum and
`minimum blood pressures during a time Tx of a heart beat
`in a graph with the abscissa axis indicating time and the
`ordinate axis indicating blood pressure. Specifically,
`the
`entire reference blood pressure area (Ax) is determined as a
`sum of a rectangular region (a lower region Axp2) whose
`horizontal sides are the beginning and end of a single at heart
`beat (Tx) and whose top vertical side is the minimum blood
`pressure (Pxd), and a generally triangular region (an upper
`region Axp1) whose bottom side has a length corresponding
`to the heart beat time (Tx) and which has a height corre-
`sponding to a difference between the maximum blood pres-
`sure and the minimum blood pressure (Pxs—Pxd).
`
`[0054] As for the output of the photoelectric sensor 37
`(i.e.,
`input of pulse waves) (S150), after execution of a
`correcting process corresponding to a body motion as
`described below,a pulse area is calculated based onrelative
`changes in pulse waves outputted from the CPU 43 via aD/A
`converter (not shown) (S160). Specifically, a reference pulse
`amplifier 48. Of the output signal from the light-receiving
`wave area (Vs) is determined as a value of integration of
`portion 385 of the body motion sensor 38, components other
`changes in the amount of blood flow in the heart beat time
`than a predetermined frequency bandare cutoff. Asaresult,
`(Tx) as indicated in FIG. 12. Next, the CPU 43 calculates an
`the signal is inputted as a body motion componentto the
`area ratio (Ax/Vs) between the reference pulse wave area
`pulse wave correcting circuit 47 and the multiplexer 42.
`(Vs) and the reference blood pressure area (Ax) (S170). The
`[0049] The pulse wave correcting circuit 47 subtracts a
`thus-obtained area ratio (Ax/Vs) becomes a value in which
`filtered output signal of the body motion sensor 38 from a
`the pulse wave and the blood pressure are associated with
`filtered output signal of the photoelectric sensor 37 so as to
`each other. On the basis of the associated value, the infrared-
`generate a waveform obtained by removing a body motion
`emitting portion 37a of the light-emitting sensor 36 is
`componentfrom the output signal of the photoelectric sensor
`automatically adjusted in terms of the amountoflight by the
`37.
`automatic amount-of-light adjuster 51. Furthermore,
`the
`light-receiving portion 37b ofthe light-emitting sensor 36 is
`automatically adjusted in terms of gain by the automatic
`
`[0050] The control unit 35 includes the amplifiers 41, 44,
`48, the multiplexer 42, the CPU 43, the low-passfilters 39,
`
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`US 2002/0095092 Al
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`Jul. 18, 2002
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`gain adjuster 52. In this manner,the level of the output of the
`light-emitting sensor 36 is automatically adjusted.
`
`[0055] After execution of the gain adjustment andthe like
`as described above, the blood pressure is measured. In this
`case too, a process for removing noise components such as
`bo