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`US006402690Bl
`
`(12)United States Patent
`
`
`Rhee et al.
`
`No.:US 6,402,690 Bl
`
`(10)Patent
`Jun.11,2002
`(45)Date of Patent:
`
`
`
`(54)ISOLATING RING SENSOR DESIGN
`
`(75) Inventors: Sokwoo Rhee, Cambridge; Boo-ho
`
`
`
`
`Yang, Boston; Haruhiko H. Asada,
`
`Lincoln, all of MA (US)
`
`(73) Assignee: Massachusetts Institute of
`
`
`
`
`
`Technology, Cambridge, MA (US)
`
`( *) Notice: Subject to any disclaimer, the term of this
`
`
`
`
`
`
`patent is extended or adjusted under 35
`
`U.S.C. 154(b) by O days.
`
`(21)Appl. No.: 09/552,185
`
`5,152,296 A 10/1992 Simons
`
`5,285,784 A 2/1994 Seeker
`
`5,297,548 A 3/1994 Pologe
`
`5,309,916 A 5/1994 Hatschek
`
`5,511,546 A 4/1996 Hon
`
`5,638,818 A 6/1997 Diab et al.
`
`
`5,661,460 A 8/1997 Sallen et al.
`
`
`5,694,939 A 12/1997 Cowings
`
`
`
`5,735,800 A * 4/1998 Yasakawa et al. .......... 600/503
`
`5,738,102 A 4/1998 Lemelson
`
`5,771,001 A 6/1998 Cobb
`
`
`5,964,701 A 10/1999 Asada et al.
`
`
`6,322,515 Bl * 11/2001 Goor et al. ................. 600/485
`
`
`
`FOREIGN PATENT DOCUMENTS
`
`(22)Filed:Apr. 18, 2000
`
`31 50925 Al 6/1983
`DE
`3609 913 Al 10/1987
`DE
`
`0 467 853 Al 7 /1991
`EP
`Related U.S. Application Data
`
`
`0706 776 Al 4/1996
`EP
`
`
`
`
`(60)Provisional application No. 60/130,774, filed on Apr. 23,
`
`0 724 860 Al 8/1996
`EP
`1999.
`1 655 834 Al 6/1991
`FR
`WO WO 93/16636
`9/1993
`
`
`(51)Int. Cl.7 .................................................. A61B 5/00
`WO WO 98/17172 4/1998
`
`....................... 600/300; 600/485; 600/500; (52)U.S. Cl.
`
`
`
`
`* cited by examiner
`
`
`
`
`600/508; 600/310; 600/549; 600/323; 128/903
`
`
`
`(58)Field of Search ................................. 600/300, 301,
`
`Primary Examiner-Kevin Shaver
`
`
`
`600/309-311, 316, 323, 324, 326, 328,
`
`Assistant Examiner-Michael C Astorino
`
`
`
`340,344,345-348, 355, 361-365, 481-510,
`
`
`(74)Attorney, Agent, or Firm-Bromberg & Sunstein LLP
`
`
`549, 587, 595; 128/897, 898, 903, 920
`(57)
`
`ABSTRACT
`
`(56)
`
`
`
`References Cited
`
`A monitoring system for monitoring the health status of a
`
`
`
`
`
`
`patient by performing measurements such as skin
`
`
`temperature, blood flow, blood constituent concentration,
`
`
`
`3,835,839 A 9/1974 Brown
`
`and pulse rate at the finger of the patient. The monitoring
`
`
`3,878,502 A 4/1975 Rochelle
`
`system has an inner ring proximate to the finger as well as
`
`
`
`
`3,972,038 A 7/1976 Fletcher et al.
`
`
`an outer ring, mechanically decoupled from the inner ring,
`
`
`
`3,972,320 A 8/1976 Kalman
`
`
`
`4,063,410 A 12/1977 Welling
`
`
`
`that shields the inner ring from external loads. Measure­
`
`
`
`4,396,906 A 8/1983 Weaver
`
`
`
`ments are performed in accordance with a protocol that may
`
`
`
`4,535,324 A 8/1985 Levental
`
`
`be preprogrammed, or may be modified on the basis of
`
`
`
`4,799,062 A 1/1989 Sanderford, Jr. et al.
`
`
`real-time data or by command from a remotely located
`
`
`
`4,825,872 A 5/1989 Tan et al.
`medical professional.
`
`
`
`4,827,943 A 5/1989 Bornn et al.
`
`
`
`
`4,924,450 A 5/1990 Brashear et al.
`
`
`
`
`
`5,025,793 A * 6/1991 Richey et al. .............. 600/485
`
`U.S. PATENT DOCUMENTS
`
`20 Claims, 5 Drawing Sheets
`
`STATION
`UNIT g§
`
`10
`
`NO EXTERNAL
`FORCE APPLIED
`
`MASIMO 2005
`Apple v. Masimo
`IPR2020-01523
`
`

`

`U.S. Patent
`
`Jun. 11, 2002
`
`Sheet 1 of 5
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`US 6,402,690 B1
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`U.S. Patent
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`Jun. 11, 2002
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`Sheet 2 of 5
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`US 6,402,690 B1
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`FIG.2
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`

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`U.S. Patent
`
`Jun. 11, 2002
`
`Sheet 3 of 5
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`US 6,402,690 B1
`
`EXTERNAL
`
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`EXPERIMENT CONFIGURATION
`FIG. 3
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`

`

`Jun. 11, 2002
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`Sheet 4 of 5
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`U.S. Patent
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`Jun. 11, 2002
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`Sheet 5 of 5
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`US 6,402,690 B1
`
`2
`FIG. 1a is a cross-sectional diagram of an isolating ring
`sensor design in accordance with preferred embodiments of
`the present invention;
`FIG. 16 illustrates the effect of an external force on the
`isolating ring sensor of FIG. 1a;
`FIG. 2 depicts a perspective view of an embodimentofthe
`ring sensor device of FIG. 1a;
`in axial
`FIG. 3 shows an experimental configuration,
`cross-section, for evaluating the operation of an isolating
`ring sensor in accordance with an embodimentof the present
`invention;
`FIG. 4 showsthe responseofa prior art ring sensor in the
`face of applied external forces; and
`FIG. 5 shows the response of an isolating ring sensor, in
`accordance with an embodimentof the present invention,in
`the face of applied external forces.
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`
`10
`
`15
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`20
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`25
`
`30
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`35
`
`40
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`45
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`50
`
`55
`
`60
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`65
`
`Embodiments of the present invention provide improve-
`ments upon finger-ring sensors of the kind described in U.S.
`Pat. No. 5,964,701, and may also be applied to other sensors
`wor on the body for monitoring any of a variety of
`physiological parameters, including, without limitation, skin
`temperature, electrical impedance, pulse, blood constituent
`concentration, and/or blood flow. In accordance with pre-
`ferred embodiments of the invention, sensor data is trans-
`mitted to a computer through a wireless communication link
`and the patient status is analyzed continually and remotely.
`Any trait of abnormal health status and possible accidents
`may be detected by analyzing the sensor data. Asensor worn
`as a finger ring sensor has particular advantages such as that
`such a sensor may be worn bythe patient at all times, hence
`the health status may be monitored 24 hours a day. For
`purposes of the present description,
`the sensor will be
`referred to, without limitation, as a ring sensor, and the
`sensing modality, again without limitation, will be described
`in terms of a photoplethysmographic device for measuring a
`pulse using optical elements such as infrared light-emitting
`diodes (LEDs) and photodiodes.
`the ring
`In a preferred embodiment of the invention,
`sensor is a miniaturized telemetered ambulatory monitoring
`device in a ring configuration that combines the technology
`of pulse oximetry with microelectronics and wireless com-
`munication technologies. This device optically captures the
`pulsation and the oxygensaturation ofthe arterial blood flow
`of the patient and transmits the signals to a personal com-
`puter in a wireless manner. The light emitted from LED
`further embodiments of the
`In accordance with yet
`traverses human -tissue, and reaches the photodetector, with
`invention, a health monitoring system may be provided that
`someof the photons absorbed bytissue including the blood.
`hasat least one sensor coupled to a ring proximatetoafinger
`Since the near infrared (NIR) absorption coefficient of blood
`of the patient for providing a signal based on at least one of
`exceeds that of the other intervening tissue, the intensity of
`skin temperature, blood flow, blood constituent
`received light depends on the amountofthe blood in the path
`concentration, and pulse rate of the patient, and an electron-
`throughthe tissue. As a result, when the digital arteries and
`ics module disposed on the ring for processing the signal
`the capillaries in the finger expand by the pumpingactivity
`provided by the sensor, wherein the electronic module
`of the heart, the intensity of light received by the detector
`includes a protocol scheduler for specifying a schedule of
`decreases. Conversely, the measured light intensity becomes
`physiological measurements. The monitoring system may
`higher whenthe arteries and the capillaries contract. Such a
`have a transponderfor transmitting physiological data based
`ring sensor can be worn by the patient twenty-four hours a
`on the sensor signal to a remote station unit and a receiver
`day at home. Real-time, continuous monitoring with the ring
`for receiving protocol scheduling commands from the
`remote station unit.
`sensor allows not only for emergency detection of an abrupt
`changeof the patient health condition but also for long-term
`monitoring of vital signs of otherwise difficult and noncom-
`pliant patients such as demented elderly people.
`Sensors such as the ring sensor, however, are inevitably
`susceptible to a variety of motion and ambientlightartifacts.
`
`1
`ISOLATING RING SENSOR DESIGN
`
`The present application claims priority from U.S. Pro-
`visional Application Ser. No. 60/130,774, filed Apr. 23,
`1999, which is incorporated herein by reference.
`TECHNICAL FIELD
`
`The present invention pertains to a device for monitoring
`the health status of a patient and, more particularly, for
`isolating such an apparatus from external disturbances.
`BACKGROUND OF THE INVENTION
`
`The present invention is an improvementuponfinger-ring
`sensors such as those described in U.S. Pat. No. 5,964,701,
`issued Oct. 12, 1999, which incorporated herein by refer-
`ence.
`
`One of the most difficult problems in implementing a
`sensor that may be worn on the body is the issue of
`eliminating signal artifacts due to motion of, or forces
`exerted upon, the sensor. A further problem is the inflex-
`ibility of preprogrammed operating protocols.
`SUMMARYOF THE INVENTION
`
`In accordance with preferred embodiment of the
`invention, there is provided a monitoring system for moni-
`toring the health status of a patient. The monitoring system
`has an inner ring characterized bya first mass. The inner ring
`is proximate to a finger of the patient and hasat least one
`sensor coupled to the inner ring for providing a signal based
`on at
`least one of skin temperature, blood flow, blood
`constituent concentration, and pulse rate of the patient. The
`monitoring system also has an outer ring characterized by a
`second mass. The outer ring is coupled to the finger of the
`patient. The monitoring system has an electronics module
`disposed on the outer ring for processing the signal provided
`by the sensorand a flexible electrical coupling for conveying
`the signal from the sensor to the electronics module in such
`a manneras to maintain mechanical decoupling of the inner
`and outer rings.
`In accordance with further embodiments of the invention,
`the pressure of the inner ring against the finger of the patient
`may be adjustable within a specified range, including by
`means of a material having a stiffness that is a nonlinear
`function of extension. The monitoring system mayalso have
`a light source and a detector for monitoring a characteristic
`of arterial blood flow within thefinger, and a control loop for
`regulating the intensity of light emitted by the light source.
`Regulation may be in responseto a ratio of signal to noise
`in the detector or to a signal generated by the temperature
`sensor.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention will more readily be understood byrefer-
`ence to the following description taken with the accompa-
`nying drawings in which:
`
`

`

`US 6,402,690 B1
`
`3
`For example, in a highly accelerated motion of the patient,
`the inertia may causethe optical sensor unit to moveorslide
`on the skin surface, and, as a result,
`the optical sensor
`measurement may be distorted or even ruined completely.
`Evena static external force may cause a similar distortion of
`the measurement due to the relative displacement of the
`sensor to the finger. Additionally, ambient light may be
`another major source of measurementartifacts. These kinds
`of external disturbances can seriously degrade the quality of
`measurement of the ring sensor. The optical method of
`measuring pulse is particularly prone to external
`disturbances, both mechanical and optical. As the signal
`detected by the optical sensor is amplified thousands of
`times, any small disturbance on the sensor will result in
`significant change of the amplified signed and eventually
`degrade the measurement.
`Referring now to FIG. 1a,a ring sensor, denoted generally
`by numeral 10 is shown in cross-section. An inner ring 12,
`proximate to a finger 14 of the subject, includes a sensor
`unit, denoted generally by numeral 16. Inner ring 12, and
`thus sensor unit 16, are decoupled from most of the inertia
`of the device. The decoupling may be achieved, in preferred
`embodiments of the invention, by having two rings, namely
`inner ring 12 and outer ring 18, which are mechanically
`independentto each other. By putting the optical sensor unit
`16 on one of the rings while a circuit board and battery
`module 20 is on theotherring,it is possible to protect sensor
`unit 16 from the influence of the most of any inertia force to
`which the ring 10 is subjected.
`The problem caused by external static forces can also be
`solved by same approach. Thering device 10 comprises two
`rings, with a first ring 12 enclosed in the second outer ring
`18. Inner ring 12 floats inside outer ring 18 so that static
`displacement of the outer ring 18 does not substantially
`influence inner ring 12. The problem of ambientlight can be
`also alleviated by this design since outer ring 18 worksas an
`optical seal for sensor unit 16 on the inner ring 12.
`In accordance with preferred embodiments of the
`invention, inner ring 12 is basically a thin band that carries
`optical sensor unit 16 which, in turn, includes one or more
`LEDs 22 and one or more photodiodes 24. Inner ring 12 is
`made of light material such as plastic or acrylic, or even a
`rubber band. A rubberor latex bandis preferable in thatit is
`flexible and compliant. From the analysis of finger models,
`it has been foundthat giving a certain pressure on the optical
`sensor on the skin may increase the amplitude of the
`measured signal, resulting in a higher signal to noise ratio.
`Additionally, using a compliant material for the inner ring
`may advantageously contribute to holding the finger firmly.
`The second part of ring device 10 is the outer ring 18 that
`carries the circuit board and battery module 20. Additionally,
`module 20 mayinclude a radio-frequency or other transpon-
`der or transmitter for transmitting signals conveying physi-
`ological data to a station unit 28, either elsewhere on the
`person of the patientor in the vicinity-of the patient. Second
`part 18 is madeofa stiffer material such as metal or PVC so
`that it can sustain the circuit board and the batteries. It also
`
`works as a mechanical shelter against external forces. First
`part 12 is put into the second part 18 such thatthe first part
`12 can float inside the second part 18. Sensor unit 16 is
`mechanically coupled to the first part 12 and is electrically
`connected to the circuit board 20 on the second part 18 by
`means of a few flexible, thin wires 26 that are long enough
`that the rotation of outer ring 18 does not substantially
`influence the inner ring 12. Wires 26 are the only connection
`between the first part 12 and the second part 18. With this
`configuration,
`the first part carrying the sensor unit
`is
`
`10
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`15
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`20
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`25
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`30
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`35
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`4
`virtually de-coupled from the movementof the secondpart,
`and unconstrained by the influence of the movement of the
`second part.
`FIG. 15 illustrates the effect of an external force applied
`in direction 30 on device 10. When an external force is
`
`applied to outerring 18, the relative position of the inner ring
`12 to the outer ring 18 changes, however the relative
`position of the finger 14 to the sensor unit 16 that is attached
`on the inner ring 12 does not change. It is preferred that the
`wires 26 that connect the circuit board 20 and the sensor unit
`
`16 electrically be thin and long enough that when the outer
`ring 18 rotates by any kind of external torque, the inner ring
`12 does not rotate substantially although the outer ring 18
`may rotate to some extent.
`In preferred embodiments of the invention, the miniatur-
`ized sensor unit 16 is attached on the internal ring 12 whose
`massis almost negligible with respect to the total mass ofthe
`device. Typically the ratio of the massof the outer ring to the
`mass of the inner ring is at least an order of magnitude.
`Sensor unit 16 preferably includes a small circuit board (5
`mmx5 mmx0.8 mm) that contains two light emitting pho-
`todiodes and a photodetector, although other embodiments
`such as an integrated optical unit are within the scope of the
`present
`invention. The main circuit board and batteries
`comprising module 20 are relatively heavy and bulkysit on
`the external ring 18 which may also be referred to as a
`housing. The main circuitry is composed of many small
`element, which may be of surface mountstyle or bare die
`form. Resistors and capacitors are either wire-bonded or
`glued with conducting epoxy. Integrated circuits may be in
`die forms and wire-bonded on gold pads onthe circuit board.
`Even though small and light components are used,the total
`mass of this circuit board is not negligible. In addition.
`button type batteries used for providing powerto the circuit
`haverelatively large mass. In a preferred embodimentof the
`invention, these components sit on the surface of the outer
`ring.
`Inner ring 12 and the outer ring 18 are connected only by
`a few wires 26 that are flexible and thin. As a result, the inner
`ring and the outer ring are virtually isolated mechanically.
`The outer ring is subject to external forces including direct
`forces and inertial forces, and it may moveor rotate around
`the finger. However,
`the inner ring is not substantially
`influenced by the movementof the outer ring. Moreover, the
`inner ring floats inside the outer ring. When a person wears
`the device, both inner ring 12 and outer ring 18 are worn
`simultaneously, but there is no direct mechanical connection
`between the two rings except a few thin wires 26 for signal
`exchange. Thus, any external force applied to the device
`applies substantially only to the outer ring, and the force is
`sustained mostly by the parts of the outer ring that are in
`contact with the finger, The external force-does not substan-
`tially influence the contact point between the finger and the
`internal ring since the two rings are virtually de-coupled. As
`a result, the measurement from the sensor unit can be kept
`stable even in the presence of external forces applied to the
`outer ring.
`in accordance with embodi-
`The isolating ring sensor,
`ments of the present invention, may provide the additional
`advantage of optical isolation since outer ring 18 may serve
`to block the penetration of ambient light such that the sensor
`measurementis not influenced significantly by such light.
`The pressure with which inner ring 12 is held against
`finger 14 is knownto affect the level of signal in the case of
`certain measurements. For example, pressure on the outside
`of blood vessels reduces the stiffness of blood vessel walls,
`
`

`

`US 6,402,690 B1
`
`5
`thereby increasing the amplitude of pulse measurement
`signals, for example. On the other hand,a trade-off exists in
`that pressure must, not be increased to such an extent as to
`occlude the free flow of blood within the vessel. Pressures
`for sensor ring applications have been found advantageously
`to lie in the range of 10-30 mm Hg. In accordance with an
`embodiment of the invention, a preferable nonlinear char-
`acteristic of tension in ring 12 as a function of extension of
`the ring is provided by fashioning the ring from an elas-
`tomer. In particular, it is desirable that the tension saturate
`with extension. A preferable material for providing that
`property is a elastomeric weave such as used in the elastic
`bands of clothing.
`Other factors effect blood flow in the extremities of a
`mammal, and, more particularly in the finger of a human
`subject. One such factor is low ambient temperature which
`causes a reduction in blood flow in the extremities. To
`
`compensate for temperature effects, in accordance with an
`embodiment of the invention, the intensity of light emitted
`by LED 22 is increased to maintain an acceptable level of
`signal-to-noise. To that end, a temperature sensor 8 may be
`provided as part of circuitry 20 to allow for automatic
`compensation of LED intensity. Alternatively, in accordance
`with further embodiments of the invention, a signal-to-noise
`level
`ratio may be specified, either in hardware or
`in
`software, and the LED level may be adjusted by a control
`loop to maintain the specified ratio or to optimize the signal
`level within specified constraints which may include power
`utilization, for example.
`FIG. 2 depicts a perspective view of ring sensor device 10,
`in accordance with a preferred embodimentofthe invention.
`Outer ring 18 is divided into two pieces 32 and 34 for ease
`of wearing by the patient. Module 20 containing the signal
`processing electronics and transmitter is part of outer ring
`piece 34.
`To verify new designs in accordance with an embodiment
`of the present invention, the measurement obtained from the
`new dual-ring sensor was compared with that of an old ring
`sensor. The old ring sensor uses just a simple ring made out
`of aluminum, which is only one piece. The circuit board is
`attached on the outer surface of the ring and the sensor unit
`is attached inner surface of the same ring. Referring now to
`FIG. 3, an experiment was conducted giving an external
`static force on the ring 40 at various positions. Digital
`arteries 42 are shown for angular orientation about axis 44
`of finger 14.
`Initially, an external pressure was applied on the point of
`angle 0=0°, and the corresponding photoplethysmograph
`was measured. The same experiments were conducted with
`6=90°. 6=180°, and 6=270°, respectively. The photoplethys-
`mographs from the experimentsof the plain (old) ring sensor
`are shown in FIG. 4, and the results of the new ring are
`shownin FIG. 5.
`
`6
`a small air gap can exists between the optical sensor and the
`skin, which will seriously degrade the measurement. In the
`case of 6=180°, the air gap becomeseven larger and we can
`hardly recognize the pulses. Actually this is the worst
`configuration among the four cases.
`Referring now to FIG. 5,
`the photoplethysmographs
`graphs of a new ring sensor, in accordance with a preferred
`embodiment of the present invention, show much better
`results. Because of the reason explained above, the signalis
`most clear and the amplitude is large with @=0° or 270°.
`However, even with an external force applied at 6=90° or
`180°, the photoplethysmographic signalis still clear andit is
`not difficult to identify the pulses. Even at the worst con-
`figuration which is @=180°,
`the amplitude of signal
`is
`relatively small, but is clearly reflecting the human pulse to
`the extent that is enoughto identify the pulse. With this new
`ring design,
`there exists no air gap between the optical
`sensor and the skin even though the outer ring will move
`from its original position significantly.
`The ring sensor apparatus described herein may be
`operated, in accordance with embodiments of the invention,
`in a variety of modes. It is recognized that there are inherent
`trade-offs between accuracy of measuring any physiological
`parameters and power consumption bythe sensor electronics
`and thus battery charge lifetime. Under some episodic
`conditions, frequent and accurate monitoring of vital signs
`may beessential, such as if the patient is undergoing some
`cardiac distress. Under routine conditions, however,
`less
`frequent monitoring will allow for longer operation between
`battery maintenance operations.
`Therefore, various flexible contingent measurement pro-
`tocols may be provided. For example, a feedback mode
`provides for modification of the measurement schedule
`based on real time data. A protocol scheduler 6 (shown in
`FIG. 1a) is provided, in software or hardware, either on
`board the ring or at remote station unit 28,
`to initiate a
`specified time series of scheduled physiological measure-
`ments. Protocol scheduler 6 may be responsive to a com-
`mand packet uploaded to the ring from a remotely located
`medical professional or may respond to variations in locally
`monitored signal-to-noise or to monitored physiological
`parameters that are programmedto cause a modification of
`the measurement protocol.
`In accordance with an alternate embodiment of the
`
`invention, protocol scheduler 6 provides a medical profes-
`sional at station unit 28 with a menu of physiological
`monitoring protocols and allows, via bidirectional commu-
`nications with the sensor ring, for selection by the medical
`professional of a preferred modeof vital sign measurement.
`The described embodiments of the invention are intended
`
`10
`
`15
`
`20
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`25
`
`30
`
`35
`
`40
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`45
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`50
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`to be merely exemplary and numerousvariations and modi-
`fications will be apparent to those skilled in the art. All such
`variations and modifications are intended to be within the
`scope of the present invention as defined in the appended
`In the case of the old ring composed of one piece, the
`claims.
`measurementvaried significantly as a function of the exter-
`We claim:
`nal forces. With an external force at an angle of @=0° or
`1. Amonitoring system for monitoring the health status of
`270°, the photoplethysmograph is clear with large ampli-
`a patient, the monitoring system comprising:
`tude. It is known from analysis of finger models that the
`60
`a. an inner ring characterized byafirst mass, the inner ring
`signal becomes stronger with a certain pressure on the
`adapted to be proximate to a finger of the patient;
`sensor unit. In the experiment with an external force at 0° or
`b. at
`least one sensor coupled to the inner ring for
`270°, the amplitude of signal is actually larger than the case
`providing a signal based on at
`least one of skin
`with no external force due to the pressure applied on the
`temperature, blood flow, blood constituent
`sensor unit. However. when the external force is applied at
`concentration, and pulse rate of the patient; and
`90°, the amplitude of the signal is significantly reduced and
`the pulses are hard to detect. In this configuration,
`the
`c. an outer ring characterized by a second mass,the outer
`pressure applied on the sensor unit is almost zero, and even
`ring adapted to be coupled to the finger of the patient
`
`55
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`65
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`

`

`US 6,402,690 B1
`
`8
`7
`that the control loop regulates the intensity of light emitted
`substantially externally to the inner ring, the second
`by the light source in responseto the signal generated by the
`mass beinglarger than thefirst mass, such that the outer
`temperature sensor.
`ring shields the inner ring from any external loads.
`15. A monitoring system for monitoring the health status
`2. Amonitoring system according to claim 1, wherein the
`of a patient, comprising:
`outer ring further shields the inner ring from ambientlight.
`3. Amonitoring system according to claim 1, wherein the
`a. an inner ring characterized byafirst mass, the inner ring
`outer ring shields the inner ring from inertial loads.
`adapted to be proximate to a finger of the patient;
`4. Amonitoring system according to claim 1, wherein the
`b. at
`least one sensor coupled to tee inner ring for
`outer ring further shields the inner ring from static external
`providing a signal based on at
`least one of skin
`forces.
`temperature, blood flow, blood constituent
`5. A monitoring system according to claim 1, further
`concentration, and pulse rate of the patient;
`comprising a flexible electrical coupling for conveying the
`c. an outer ring characterized by a second mass,the outer
`signal from the sensor to an electronics module in such a
`ring adapted to be coupled to the finger of the patient
`manner as to maintain mechanical decoupling of the inner
`the second mass being larger than the first mass, such
`and outer rings.
`that the outer ring shields the inner ring from any
`6. Amonitoring system according to claim 1, wherein the
`external loads;
`pressure of the inner ring against the finger of the patient is
`d. an electronics module disposed on the outer ring for
`adjustable within a specified range.
`processing the signal provided by the sensor; and
`7. Amonitoring system according to claim 1, wherein the
`e. a flexible electrical coupling for conveying the signal
`pressure of the inner ring against the finger of the patient is
`from the sensor to the electronics module in such a
`within the range of 10-30 mm Hg.
`manner as to maintain mechanical decoupling of the
`8. A monitoring system according to claim 1, wherein the
`inner and outer rings.
`pressure of the inner ring against the finger of the patient is
`16. A monitoring system according to claim 15, wherein
`maintained by a material havingastiffness that is a nonlinear
`25
`function of extension.
`the flexible electrical coupling includes a plurality of wires.
`17. A monitoring system according to claim 15, further
`9. Amonitoring system according to claim 1, wherein the
`comprising:
`pressure of the inner ring against the finger of the patient is
`a. a transmitter for converting the signal to a wave;
`maintained by an elastomer.
`b. at least one receiver for receiving the wave from the
`10. A monitoring system according to claim 1, further
`transmitter; and
`including a light source and a detector for monitoring a
`characteristic of arterial blood flow within the finger.
`c. a controller for analyzing the wave and determining an
`abnormal health status.
`11. A monitoring system according to claim 10, wherein
`the light source is a light-emitting diode.
`18. A monitoring system according to claim 15, wherein
`12. A monitoring system according to claim 10, further
`the massof the outerringis at least ten times the massof the
`including a control loop for regulating the intensity of light
`inner ring.
`emitted by the light source.
`19. A monitoring system according to claim 15, wherein
`13. A monitoring system according to claim 12, wherein
`the inner ring includes a flexible material.
`the control loop regulates the intensity of light emitted by the
`20. A monitoring system according to claim 19, wherein
`the tension on the flexible material is a nonlinear function of
`light source in response to a ratio of signal to noise in the
`detector.
`extension of the flexible material.
`
`20
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`10
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`15
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`30
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`35
`
`40
`
`14. A monitoring system according to claim 12, further
`including a temperature sensor for generating a signal such
`
`

`

`UNITED STATES PATENT AND TRADEMARKOFFICE
`CERTIFICATE OF CORRECTION
`
`PATENT NO.—: 6,402,690 B1 Page 1 of 1
`
`
`DATED
`: June 11, 2002
`INVENTOR(S): Sokwoo Rhee etal.
`
`It is certified that error appears in the above-identified patent and that said Letters Patentis
`hereby corrected as shown below:
`
`
`Column 8
`Line 8, replace “tee” with -- the --.
`Line 13, replace “patient” with -- patient, --.
`
`Signed and Sealedthis
`
`Twenty-first Day of January, 2003
`
`JAMES E. ROGAN
`Director of the United States Patent and Trademark Office
`
`