5,964,701
`[11] Patent Number:
`[19]
`Ulllted States Patent
`
`Asada et al.
`[45 J Date of Patent:
`Oct. 12, 1999
`
`U3005964701A
`
`[54] PATIENT MONITORING FINGER RING
`SENSOR
`
`[75]
`
`Inventors: Haruhiko H. Asada, Concord; Boo-Ho
`,
`-_
`-
`gigfigggjvtfillkfifilvggncghgflnny Slu’
`.
`’
`g’
`chmgtmh all Of Mass-
`_
`.
`[73] Assignch WiassaChuscttS “WWW 0f
`chbnOlOgy, Cambridge, Mass.
`
`4,827,943
`4,924,450
`5,152,296
`
`.......................... .. 128/668
`5/1989 Bornn et al.
`.. 367/118
`5/1990 Brashear et al.
`
`.. 600/483
`10/1992 Simons ..... ..
`
`lsncfkcr -~
`-~
`o oge .
`..
`/
`,
`,
`4/1996 Hon .........
`.. 128/633
`5,511,546
`
`..
`128/653.1
`6/1997 Diab etal.
`5,638,818
`8/1997 Sallen et al.
`.. 340/573
`5,661,460
`
`12/1997 Cowings ............................... .. 128/905
`5,694,939
`4/1998 Lcmclson .............................. .. 600/483
`5,738,102
`6/1998 Cobb ..................................... .. 128/903
`5,771,001
`FCHIEICHJIKXTEPJT‘[)O(HJhAElJTS
`
`[21] 1\ppl.llo; 08/957,789
`.
`Flledi
`
`061- 24s 1997
`
`[22]
`
`Related US. Application Data
`
`[63] Continuationeinepart of application No. 08/954,889, Oct. 8,
`1997
`Provisional application No. 60/029,253, Oct. 24, 1996.
`6
`
`[60]
`
`..................................................... .. A61N 5/00
`Int. Cl.
`[51]
`........................................... .. 600/300; 128/903
`[52] US. Cl.
`[58] Field of Search ........................... .. 128/903; 600/300,
`600/301> 322> 483> 561> 549
`_
`References Clted
`Us. pATENT DOCUMENTS
`
`[56]
`
`/1974 Brown ................................ 128/205 F
`3,835,839
`4,1975 Rochelle ............................... .. 340/5 R
`3,878,502
`7/1976 Fletcher et al.
`.................. .. 340/189M
`3,972,038
`. . . .. 128/2.1
`/1976 Kalman . . . . .
`3 972 320
`
`4’06q’4m 12,1977 Welling
`€8/38R
`
`
`. [34% DD
`43956905 Q1983 \rveaver
`8/1985 Levental ................................ .. 340/574
`4,535,324
`...................... .. 128/633
`4,700,708 10/1987 New, Jr. et al.
`
`4,799,062
`1/1989 Sanderford, Jr. et al.
`342/450
`4,825,872
`5/1989 Tan et al.
`.............................. .. 128/633
`
`.
`1/1992 European Pat. Off.
`4/1996 European Pat. 0ft. .
`8/1996 European Pat. Off.
`.
`6/1991
`France .
`10/1987 Germany.
`9/1993 WIPO .
`
`0467853 A1
`0706776 A1
`0724860 A1
`2655834 A1
`3609913 A1
`WO 93/16636
`.
`.
`Primary Examlflcrficbcrt L~ Nasser
`Assistant Examiner—Michael Astorino
`Attorney) Agent, or Firm_Br0mberg & Sunstein LLP
`57
`ABSTRACT
`
`J
`[
`A monitoring system for monitoring the health statlls of a
`patient and transmitting to a remote receiver a signal, based
`on measured physiological parameters. Asensor is incorpo-
`rated in a finger ring or other article of apparel so as to
`monitor skin temperature, blood flow, blood constituent
`concentration, or pulse rate of the patient. The data are
`encoded for Wireless transmission by mapping a numerical
`1
`~
`t d
`~th
`hdt
`t
`1
`~tt d ft
`va “6 “so” e
`.W1
`eac
`.a um 0 a P“ 56 eml 6.
`a .er a
`delay of a speclfied duratlon [ollowmg a fiduclal
`tlme.
`Multiple ring bands and sensor elements may be employed
`for dcriVing three-dimensional dynamic characteristics of
`arteries and tissue of the finger.
`
`16 Claims, 4 Drawing Sheets
`
`BATTERY TRANSMITTER
`CPU, ASIC MEMS ACCEL.
`
`
`
`0001
`
`US. Patent No. 8,652,040
`
`Apple Inc.
`APL1064
`
`Apple Inc.
`APL1064
`U.S. Patent No. 8,652,040
`
`0001
`
`

`

`US. Patent
`
`Oct. 12,1999
`
`Sheet 1 0f 4
`
`5,964,701
`
`10
`
`
`
`1.0
`
`ABSORBENCY
`COEFFICIENT
`
`0.1
`
`23
`
`gm
`W 4m AX: AGGREGATE ARTERIAL DIAMETER
`
`VARIATION (PASSIVE VASODILATION,
`VASOCONSTRICITION)
`
`
`FIG. 2b
`
`0002
`
`0002
`
`

`

`US. Patent
`
`Oct. 12,1999
`
`Sheet 2 0f 4
`
`5,964,701
`
`32
`
`MEASURED PLETHYSMOGRAM
`+
`(DISTORTED)
`——————>
`
`
`
`REAL PLETHYSMOGRAM
`
`MEASURED MOTION
`
`ADAPTIVE
`FILTER
`
`
`
`BATTERY TRANSMITTER
`
`CPU, ASIC MEMS ACCEL.
`
`
`
`0003
`
`0003
`
`

`

`US. Patent
`
`Oct. 12,1999
`
`Sheet 3 0f4
`
`5,964,701
`
`50
`
`FIG.5
`
`52
`
`
`COMPUTER
`
`
`
`CABINET7.
`
`
`50
`
`0004
`
`0004
`
`

`

`US. Patent
`
`Oct. 12,1999
`
`Sheet 4 0f 4
`
`5,964,701
`
`
`
`i
`
`i
`
`i
`
`66
`
`00000000100000 0000001000000000000000010000
`
`V V
`
`9
`
`6
`
`9
`
`FIG. 6
`
`0005
`
`0005
`
`

`

`5,964,701
`
`1
`PATIENT MONITORING FINGER RING
`SENSOR
`
`The present application is a continuation-in-part of US.
`patent application Ser. No. 08/954,889, filed Oct. 8, 1997,
`and claims priority from US. provisional application num—
`ber 60/029,253, filed Oct. 24, 1996, which is herein incor-
`porated by reference.
`
`FIELD OF THE INVENTION
`
`This invention relates to a method and apparatus for
`monitoring the health status and location of a patient and
`sending a warning of abnormality to a medical professional.
`
`BACKGROUND ART
`
`5
`
`10
`
`15
`
`The population of aged people living alone is expected to
`continue its recent upward trend. As people live longer and
`the social and economic circumstances continue to change,
`more aged people live alone having no supervision or ’
`limited attendance by caregivers, and aged spouses may be
`unable to properly care for each other. Such individuals
`suffer a high risk of accidents, and this is a major concern
`and even a fear for those aged people living alone.
`Close monitoring is the key to avoiding or responding to
`such accidents or medical emergencies. While technologies
`are known for remotely monitoring certain physiological
`parameters, these tend to be cumbersome and a patient may
`easily forget to don the monitor if it is removed, for example,
`while taking a shower. Less cumbersome monitors require
`strategies for prolonging the life-time of the battery or other
`energy source which provides power for transmitting the
`monitored physiological parameters and which is necessar-
`ily limited by the space available for housing it. The limited
`power source must be used efficiently so that even a tiny
`battery may last for a reasonable period of time, on the order
`of a few months. Among many components involved in a
`remote monitoring device, a radio transmitter may consume
`over 40% of the total power, hence power saving in the radio
`transmitter will make a significant contribution to the exten—
`sion of battery life. A power-saving wireless transmission
`protocol
`is thereby desirable for this and other power-
`sensitive applications.
`The most power-consuming part of digital RF transmitters
`is often an oscillator circuit
`involving a CMOS power
`transistor, which consumes a significant amount of power
`only when the output is high, i.e. l-bit. Therefore significant
`energy may be saved by minimizing the total duration of
`time the output is high.
`
`40
`
`45
`
`SUMMARY
`
`In accordance with a preferred embodiment of the present
`invention, a patient’s health status is monitored by an article
`of apparel, such as a finger ring, equipped with miniaturized
`sensors and a wireless transmitter. The finger ring sensor
`may be worn by the patient at all times, hence the health
`status is monitored 24 hours a day. The sensors packed into
`the finger ring may include a thermocouple for measuring
`skin temperature, an electrical impedance plethysmograph,
`and one or more optical sensors for pulse count and mea-
`surements of blood constituent concenetration and blood
`flow. The sensor data are transmitted 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 is detected by analyzing
`the sensor data. Both the physiological sensors and the
`
`2
`position sensor are used to make an accurate decision as to
`whether a warning signal must be sent to a medical profes-
`sional caring the patient. This monitoring system is particu—
`larly useful for caring for the elderly living alone and
`patients with minor impairments at potential risk by reason
`of living alone.
`In further accordance with a preferred embodiment of the
`present invention, there is provided a monitoring system for
`monitoring the health status of a patient based on an article
`of apparel, to be worn by the patient, that has at least one
`sensor for providing a signal based on at least one of skin
`temperature, blood flow, blood constituent concentration,
`and pulse rate of the patient and a transmitter for converting
`the signal to a wave. The wave may be any form of wireless
`communication between the monitor and at
`least one
`
`receiver for receiving the wave. Additionally, the monitoring
`system has a controller for analyzing the wave and deter-
`mining an abnormal health status.
`In accordance with alternate embodiments of the present
`invention,
`the monitor may include a sensor that
`in a
`temperature sensor for monitoring skin temperature, and an
`optical sensor for measuring at least one of the blood flow,
`blood constituent concentration, and pulse rate of the
`patient.
`In accordance with another aspect of the present
`invention, there is provided a method for encoding a datum,
`the method comprising the steps of associating a number
`with the datum, mapping the number to a specified duration
`of time, and representing the datum by a pulse emitted after
`a delay following a fiducial time wherein the delay equals
`the specified duration of time. Aplurality of data may thus
`be communicated, in accordance with an embodiment of the
`invention, by associating a numerical value with each
`datum, mapping the numerical value to a specified duration
`of time, and transmitting a pulse after a delay following a
`periodic fiducial time, wherein the delay equals the specified
`duration of time. The step of transmitting may also include
`emitting an electrical or electromagnetic pulse after a delay
`following a periodic fiducial time, wherein the delay equals
`the specified duration of time.
`In accordance with yet a further aspect of the present
`invention, in one of its embodiments, there is provided a
`method for monitoring the health status of a patient. The
`method has a first step of providing a monitor to be worn by
`the patient, where the monitor has at least one sensor for
`providing a measurement based on at least one of skin
`temperature, blood flow, blood constituent concentration,
`and pulse rate of the patient, and a transmitter for converting
`the signal to a wave. Further steps of the method are those
`of associating a numerical value with the measurement,
`mapping the numerical value to a specified duration of time,
`transmitting a pulse after a delay following a periodic
`fiducial time, wherein the delay equals the specified duration
`of time, receiving the pulse, and analyzing the delay
`between the periodic fiducial time and the received pulse
`wave to determine an abnormal health status.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`60
`
`65
`
`FIG. 1 is a perspective view of a finger ring sensor
`according to an embodiment of the invention.
`FIG. 2a depicts infrared spectra typical of hemoglobin
`and oxygenated hemoglobin, showing the isobestic wave-
`length employed in an embodiment of the present invention.
`FIG. 2b is a schematic showing the measurement of
`arterial diameter variation in accordance with an embodi-
`ment of the present invention.
`
`0006
`
`0006
`
`

`

`5,964,701
`
`3
`FIG. 3 is a schematic diagram of a motion filtering
`scheme in accordance with an embodiment of the present
`invention.
`
`FIG. 4 is a perspective view of a dual ring finger sensor
`in accordance with an embodiment of the present invention.
`FIG. 5 is a diagram of a typical home layout showing
`receiver
`locations according to an embodiment of the
`present invention.
`FIG. 6 depicts a unary encoding method in accordance
`with an embodiment of the present invention.
`DETAILED DESCRIPTION OF SPECIFIC
`EMBODIMENTS
`
`invention and its several
`Advantages of the present
`improvements will be seen when the following detailed
`description is read along with the attached drawings. These
`drawings are intended to provide a better understanding of
`the present invention, but they are in no way intended to
`limit the scope of the invention.
`A finger ring is nonintrusive and can be worn at all times.
`Even when taking a shower, people keep wearing rings.
`Therefore, finger rings are an appropriate locus for imbed-
`ding patient monitoring sensors and wireless transmitter in
`order to keep track of the patient twenty-four hours a day.
`Other articles of apparel may also be used in the manner
`described below with respect to finger rings.
`Asimple finger ring sensor with a wireless transmitter has
`been designed to demonstrate the concept. As shown in FIG.
`1, one or more photo diodes 2 and one or more light-emitting
`diodes (LEDs) 4 are imbedded in a ring 10 facing each other
`inside the ring. The LEDs may emit light in the visible or
`infrared, and may be particularly chosen to emit light at one
`or more specified wavelengths, such as the isobestic wave-
`length discussed below. The pulse of the patient may be
`detected as a periodic change in the sensor output. This ring
`may be placed on one of the fingers.
`In a preferred
`embodiment, ring 10 is placed on the middle finger, which
`is not only convenient for wearing the ring but also suitable
`for counting pulse. The outer skin of the middle finger is
`thin, particularly at the sides of the finger, and a digital artery
`runs right beneath the thin skin. With an appropriate
`threshold,
`the sensor detecting the beat produces a pulse
`train of on-oif signals and the pulse-train is sent
`to a
`transmitter (not shown) contained within an electronics
`module 6 which, in a preferred embodiment, is realized as a
`flexible printed circuit board.
`interference from the
`When optical sensors are used,
`ambient light may corrupt the photo probe signals. As the
`patient moves, the ambient light coming to the ring photo
`probes varies, resulting in inconsistent data. A simple
`approach to preventing ambient
`light
`interference is to
`acquire the signal when all LEDs are turned oil, and subtract
`this background effect from the measured signals. In accor-
`dance with an embodiment of the present invention, the
`optical sources, which may be LEDs, may be temporally
`modulated, and detection may be performed using synchro-
`nous detection techniques known to persons of ordinary skill
`in the art of signal processing.
`Referring now to FIG. 2a, arterial blood flow and pressure
`may be measured using LEDs emitting at the wavelength
`corresponding to the isobestic point of hemoglobin and
`oxygenated hemoglobin, at approximately 800 nanometers.
`The absorption coefficients of hemoglobin 200 and oxygen-
`ated hemoglobin 202 are plotted as a function of wavelength
`k. At the isobestic wavelength hi, the optical absorption is
`insensitive to the fraction of oxygenated hemoglobin. Thus,
`
`10
`
`15
`
`40
`
`45
`
`4
`as shown in FIG. 2b, the aggregate arterial diameter varia-
`tion Ax of artery 210 can be measured directly. Since arterial
`diameter, flow rate, and pressure are directly related, varia-
`tion of the arterial diameter is proportional to changes AP in
`the arterial pulse pressure, so that the pulse may be measured
`with light emitted by LED 206 at the isobestic and detected
`by photo detector 208, without using a cuff.
`Referring, again, to FIG. 1, a major source of interference
`with sensor readings in wearable physiological sensors is
`that of artifacts induced in the signal train by motion of the
`patient. In accordance with a preferred alternate embodi-
`ment of the invention, motion artifacts are reduced or
`eliminated by using one or more accelerometers 7 to detect
`body motion and techniques of adaptive digital filtering
`known to persons skilled in the art of signal processing to
`eliminate motion artifacts in the signal train. The acceler-
`ometers may be any microelectromechanical systems
`(MEMS) accelerometer, as known to persons of ordinary
`skill in the art of instrumentation. As shown schematically in
`FIG. 3, in adaptive noise cancellation, adaptive filter 30,
`which, in a preferred embodiment is a digital filter, adap-
`tively eliminates interference due to the motion artifact by
`removing, by means of summer 32, the motion signals from
`the sensor signals.
`Referring again to FIG. 1, a transmitter 11 of the finger
`ring sensor transmits a wave which propagates without
`wires, such as a radio wave, an optical or infrared wave, or
`an ultrasound wave transmitted through the air. A radio
`transmitter is considered by way of example. In a preferred
`embodiment, radio transmitter 11 is a narrow-band, short-
`range, compact transmitter used for radio—controlled model
`cars, and transmission is via antenna coils 14 and 16, which,
`by virtue of their orthogonal polarizations, provide a radio
`signal which,
`in the far field, may be detected without
`sensitivity to a particular polarization. Various modulation
`schemes known to persons skilled in the art may be
`employed to encode information on the transmitted signal.
`These include, for example, amplitude, frequency, or pulse-
`code modulation. Power is provided by battery 12.
`The temporal profile of the pulse pressure curve is depen—
`dent upon the compliance of the arterial wall and other
`parameters.
`In accordance with an embodiment of the
`invention, visco-elastic properties of the digital arteries may
`be derived by correlating the dynamic response of the
`plethysmographic signal to finger movements as measured
`by the MEMS accelerometer described above. This dynamic
`model of digital arteries may further be used to estimate the
`blood pressure and blood flow.
`Referring now to FIG. 4, in an alternate embodiment of
`the invention, spatially distributed optical sensors are
`employed in the ring configuration to monitor a patient’s
`health conditions. Photo diodes 42 and LEDs 44 of appro-
`priate wavelengths may be imbedded not only along the ring
`facing inwards, but also distributed in the longitudinal
`direction of the finger or other body member with a double-
`band configuration 40. The signal processing electronics,
`transmitter, antenna, battery, and MEMs accelerometer are
`contained within sensor module 48 in a manner described
`
`60
`
`65
`
`with reference to FIG. 1. Lights to be transmitted and
`reflected through the tissue of the body member may be
`collected three-dimensionally and integrated to estimate the
`patient’s arterial blood pressure and blood flow, arterial
`blood volume, hematocrit, and oxygen saturation. Hemat-
`ocrit refers to the volume percentage of erythrocytes in the
`patients blood. Similarly, other blood concentrations may be
`derived by suitable choice of optical wavelengths.
`More particularly, sensors distributed longitudinally on
`separate bands may be used to acquire the pulse wave transit
`
`0007
`
`0007
`
`

`

`5,964,701
`
`5
`time by measuring the time difference of the plethysmo-
`graphic pulse waves between two points along an artery
`since the pulse wave transit time is functionally related to the
`blood pressure.
`In accordance with an additional embodiment of the
`
`invention, the absolute blood flow may be measured based
`on electrical impedance plethysmogram (EIP) by utilizing
`double-band ring sensors 40. Electrodes 46 attached at the
`two bands can provide measurement of the impedance
`change in a body segment, which is directly mediated by
`blood volume change. Then, an integration of the impedance
`change over time, together with a measurement of blood
`volume, may provide a direct determination of the influx of
`blood.
`
`In an alternate embodiment of the invention, phase modu-
`lation spectroscopy (PMS) is used to detect,
`locate and
`characterize the optical properties of an heterogeneity such
`as arterial blood in human tissue. In PMS, the light intensity
`of the source is sinusoidally modulated and the phase shift
`is measured at a detector. The obtained phase shift is related
`to the mean pathlength of the detected photons, which in
`turn depends on the optical properties of the heterogeneity,
`and more accurate measurements may be made of blood
`pressure, blood flow and oxygen saturation and other physi-
`ological properties that cannot be measured non-invasively
`otherwise. The PMS technology along with the multiple
`photo detectors may also provide the relative position of the
`ring to the patient’s finger, compensating for the uncertainty
`due to misalignment of the ring.
`Referring now to FIG. 5, one or more stationary receivers
`50 installed in the patient’s home 54 detect this radio signal
`and provide it
`to a home computer 52,
`In a preferred
`embodiment of the invention, the pulse may be counted by
`home computer 52 rather than at the location of the sensor,
`and the home computer may decide, based on programmed
`criteria, whether a warning signal must be sent to a medical
`professional. In an alternate embodiment of the invention,
`preprocessing may be performed at the location of the sensor
`itself. In addition to measuring the pulse, other physiological
`parameters may be similarly monitored by the sensor and
`telemetered to a remote receiver. The use of tactile,
`electrical,
`thermocouple, and optical sensors, as well as
`other sensors for measuring such physiological parameters
`as skin temperature, blood flow, and blood constituent
`concentration are known in the art and are within the scope
`of the present invention.
`The location of the ring wearer can be estimated by using
`known techniques of radio location sensing in conjunction
`with the transmitter described above. The objective of using
`many receivers 50 installed within a house is twofold:
`to cover the entire house, so that no matter where the
`wearer moves within the house, the transmitted signal
`may be received;
`to locate the ring wearer, using known methods of radio
`location sensing.
`The accuracy of position estimation can be improved by
`considering the properties of radio signal propagation within
`the indoor environment.
`In general,
`the magnitude of
`received signal is inversely related to the distance from the
`transmitter. In an indoor environment, however, the signal
`propagates through multiple paths due to reflection and
`diffraction at the walls and edges, resulting in a complex,
`nonlinear distance-power relationship. However,
`the con-
`figuration of the house does not vary and the location of
`major furnishings does not change either for a long period of
`time. Therefore, the relationship between the location of the
`
`10
`
`15
`
`40
`
`45
`
`60
`
`65
`
`6
`ring wearer and the magnitude of the received signal at each
`receiver installed in the house may be substantially constant
`over the period. By calibrating the transmitter—receiver
`relationship, a nonlinear map between the ring wearer’s
`position and the receiver readings may be established. This
`allows the ring wearer’s position to be estimated.
`In order to reduce the power consumption of the patient
`monitor, a unary data transmission protocol may be
`employed in accordance with a preferred embodiment of the
`invention. Referring now to FIG. 6, this protocol is similarly
`applicable to other situations where power consumption is
`critical. The unary transmission protocol
`is preferably
`implemented by providing transmitter and receiver circuits
`such that
`the pulse width of l-bit
`is minimized while
`assuring that every 1-bit can be correctly received by the
`receiver. At the software layer, a unary transmission protocol
`is employed that reduces the number of 1-bits while carrying
`the same amount of information.
`In the standard RS—232 protocol, the average number of
`1-bits involved in the transmission of 8-bit binary data is
`four. This can be significantly reduced by using a different
`coding method. Each 8-bit sample is, instead, encoded into
`a unique (but longer) codeword with a reduced number of
`1-bits. Consider a simple example illustrating this basic idea.
`For simplicity, it may be assume that each physiological
`sample is encoded as a 4-bit binary number, which repre-
`sents 24:16 levels (from 0 to 15). Aunary encoding of each
`sample will then consist of 16 bits, with each codeword
`consisting of only one 1-bit.
`Thus, more particularly, the binary number 0111 (which
`represents level 7),
`for example, becomes,
`in unary
`encoding, 0000000010000000. Similarly, the binary number
`1111 (which represents level 15)
`in unary encoding is
`1000000000000000.
`Any datum, such as the value 60 of a variable plotted as
`a function of time 66 that can be assigned a numerical value
`may be encoded in the manner described. The assignment
`scheme depicted in FIG. 6, where a pulse 64 is triggered by
`signal 60 crossing sawtooth 62 imposes certain sampling
`requirements relative to the time rate of change of the signal.
`Other sampling schemes are also within the scope of the
`claimed invention. In general, a k-bit binary-encoded sample
`can be uniquely transformed into a 2k-bit unary-encoded
`sample, transmitted at a specified increment of time after a
`fiducial
`time to provide synchrony of transmission and
`detection. The reduction in power consumption using this
`unary encoding scheme is determined as follows: For k=8,
`each binary-encoded sample will have four 1-bits on
`average, whereas each unary-encoded sample requires
`exactly one 1-bit. This results in a factor of 4 in power
`reduction for k=8. It is easy to see that we will save a factor
`of k/2 in power consumption using unary encoding for
`general k-bit binary-encoded samples. Since the encoding
`scheme transforms each 8-bit sample to a longer codeword,
`a higher bit rate may be provided in order to obtain the same
`rate of data transmission.
`The methods described herein may have applications
`besides the clinical and home healthcare applications in
`terms of which the invention has been described. Generally,
`the invention may be applied in air conditioning control,
`home appliances, automobiles, and security, as well. The
`described embodiments of the invention are intended to be
`merely exemplary and numerous variations and modifica-
`tions 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
`claims.
`
`0008
`
`0008
`
`

`

`5,964,701
`
`8
`sponding to the isobestic point of hemoglobin and oxygen-
`ated hemoglobin.
`11. Amonitoring system according to claim 9, wherein the
`optical source is a light emitting diode.
`12. A monitoring system according to claim 7, wherein
`the optical sensor comprises a plurality of optical sources
`employing temporal and spatial modulation.
`13. A monitoring system according to claim 1, wherein
`the at least one sensor is an electrical impedance plethys-
`mograph.
`14. A monitoring system for monitoring the health status
`of a patient, comprising:
`a. a monitor having a first and a second band to be worn
`by the patient on a single finger, the monitor compris-
`ing:
`i. at least one sensor disposed on the first band for
`providing a first signal based on at least one of skin
`temperature, blood flow, blood constitucnt
`concentration, and pulse rate of the patient;
`ii. at least one sensor disposed on the second band for
`providing a second signal based on at least one of
`skin temperature, blood flow, blood constituent
`concentration, and pulse rate of the patient; and
`.
`.
`b. a controller for analyzmg the first and second signals
`and determining a physiological characteristic of the
`patient.
`15. A monitoring system according to claim 14, wherein
`30 the physiological characteristic is one of the group of arterial
`blood flow, hematocrit, and blood oxygen saturation.
`16. A monitoring system according to claim 14, further
`comprising:
`a. a transmitter for converting the first and second signals
`to a wave; and
`b. at least one receiver for receiving the wave from the
`monitor.
`
`5
`
`10
`
`15
`
`25
`
`35
`
`7
`
`We claim:
`1. Amonitoring system for monitoring the health status of
`a patient, comprising:
`a. a finger ring to be worn by the patient, the finger ring
`comprising:
`i. at least one sensor for providing a signal based on at
`least one of skin temperature, blood flow, blood
`constituent concentration, and pulse rate of the
`paticnt;
`ii. a transmitter for converting the signal to a wave; and
`iii an accelerometer disposed within the finger ring for
`removing signal artifacts due to finger motion;
`b. at least one receiver for receiving the wave from the
`finger ring; and
`c. a contro ler for analyzing the wave and determining an
`abnormal health status.
`
`2. Amonitoring system according to c aim 1, wherein tie
`controller fu ther includes a means for determining tie
`location of the patient.
`3. Amonitoring system according to c
`wave is a rac io wave.
`
`aim 1, wherein tic
`
`
`
`
`
`aim 1, wherein tie
`
`aim 1, wherein tie
`
`4. Amonitoring system according to c
`wave is a ligit wave.
`5. Amonitoring system according to c
`wave is an u trasound wave.
`6. Amonitoring system according to c aim 1, wherein tie
`sensor incluc es a temperature sensor for measuring skin
`temperature.
`7. Amonitoring system according to c aim 1, wherein tie
`sensor includes an optical sensor for measuring at least one
`of the blood i ow, blood constituent concentration, and pulse
`rate of the patient.
`8. Amonitoring system according to c aim 7, wherein tie
`optical senso comprises a modulated source and synchro-
`nous detector.
`
`
`
`9. Amonitoring system according to c aim 7, wherein tic
`sensor comprises an optical source and an optical detector.
`10. A monitoring system according to claim 9, wherein
`the optical source has a wavelength substantially corre-
`
`0009
`
`0009
`
`