United States Patent [19]
`Allum
`
`US005919149A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,919,149
`Jul. 6, 1999
`
`[54] METHOD AND APPARATUS FOR ANGULAR
`POSITION AND VELOCITY BASED
`DETERMINATION OF BODY SWAY FOR
`THE DIAGNOSIS AND REHABILITATION OF
`BALANCE AND GAIT DISORDERS
`
`[76] Inventor: John H. Allum, Hebel Str. 109, Basel,
`Switzerland, CH-4056
`
`[21] Appl. No.: 08/818,319
`[22]
`Filed:
`Mar. 14, 1997
`
`Related US. Application Data
`
`[60] Provisional application No. 60/029,010, Oct. 24, 1996.
`
`[51] Int. Cl.6 ................................................... .. A61B 5/103
`
`[52] US. Cl. ............................................................ .. 600/595
`[58] Field of Search ................................... .. 600/587, 595;
`73/862042, 865.4
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`600/595
`5/1963 Corti et a1.
`3,090,226
`340/213 R
`5/1978 Fletcher et al.
`4,092,633
`128/782
`4/1988 Nashner ............. ..
`4,738,269
`128/782
`4/1989 McStravick et a1.
`4,817,633
`128/787
`5/1989 Nashner et a1.
`4,830,024
`7/1989 NitZan et a1. ......................... .. 128/740
`4,848,358
`7/1990 Brunelle et a1. ...................... .. 600/595
`4,938,476
`5,052,406 10/1991 Nashner ..... ..
`128/782
`5,209,240
`5/1993 Jain et al.
`128/779
`
`5,281,957
`
`1/1994 Schoolman . . . . . . .
`
`. . . . . . .. 345/8
`
`4/1994 Nashner et a1. .
`5,303,715
`8/1994 Jain et al.
`5,337,757
`5,361,778 11/1994 SeitZ ........... ..
`5,368,042 11/1994 O’Neil et a1.
`5,469,861 11/1995 Piscopo et a1. ..
`5,551,445
`9/1996 Nashner ......... ..
`5,627,327
`5/1997 Zanakis ...... ..
`5,749,372
`5/1998 Allen et a1.
`
`128/782
`128/779
`128/779
`600/595
`.. 128/781
`128/782
`73/862042
`600/595
`
`FOREIGN PATENT DOCUMENTS
`
`3416873 A1 11/1985 Germany.
`W0 88/ 04909 7/1988 WIPO .
`
`OTHER PUBLICATIONS
`
`G.H. Begbie, “Some Problems of Postural Sway”, in “Myo
`tatic, Kinesthetic and Vestibular Mechanisms”, pp. 80—104
`(A.V.S. deReuck & Julie Knight, eds., 1967).
`L.M. Nashner, “A Model Describing Vestibular Detection of
`Body Sway Motion”, Acta Otolaryng 72, pp. 429—436,
`1971.
`E.V. Gur?nkel, “Physical Foundations of the Stabilogra
`phy”, Agressologie, 14, C, pp. 9—14, 1973.
`
`(List continued on neXt page.)
`
`Primary Examiner—MaX Hindenburg
`Attorney, Agent, or Firm—Foley & Lardner
`
`[57]
`
`ABSTRACT
`
`A method and apparatus for the diagnosis and rehabilitation
`of abnormal postural sway of a subject during standing or
`the performance of movement tasks is provided. Body sway
`sensors, such as angular velocity transducers, are attached to
`the body, such as the upper torso, of the subject. Output
`signals from the body sway sensors are transformed into
`detailed body sway angular displacement and velocity infor
`mation by a system processor. The body sway angular
`displacement and velocity information may be displayed to
`an operator for diagnosis of the subject’s balance or gait
`disorders. The angular displacement and velocity informa
`tion may also be provided as feedback to the subject, to
`augment the signals normally used by the subject’s brain to
`help stabilize body sway and improve balance. Rehabilitory
`feedback may be in visual, auditory, and/or tactile form,
`and/or in the form of electrical stimulation of the vestibular
`nerve. For visual feedback, a lightweight imaging system
`mounted on a pair of eyewear may be used to project a body
`sway angle and angular velocity feedback display into an
`eye of the subject. An angular position and velocity based
`body sway diagnosis system in accordance with the present
`invention may be used to monitor simultaneously the body
`sway of multiple subjects, and to provide rehabilitory feed
`back to such subjects, without interfering with or restricting
`the normal movement activities of the subjects.
`
`67 Claims, 5 Drawing Sheets
`
`FITBIT, INC. v. LOGANTREE LP
`Ex. 1007 / Page 1 of 19
`
`

`
`5,919,149
`Page 2
`
`OTHER PUBLICATIONS
`
`J. Dichgans, et al., “Postural Sway in Normals and Atactic
`Patients: Analysis of the Stabilizing and DestabiliZing
`Effects of Vision”, Agressologie 17, C, pp. 15—24, 1976.
`L.M. Nashner, “Adapting Re?exes Controlling the Human
`Posture”, EXp. Brain Res., vol. 26, pp. 59—72, 1976.
`SH. KooZekanani, “On the Role of Dynamic Models in
`Quantitative Posturography”, IEEE Trans. Biorned. Eng.,
`vol. BME—27, No. 10, pp. 605—609, Oct. 1980.
`F. OWen Black, et al., “Effects of Visual and Support Surface
`Orientation References Upon Postural Control in Vestibular
`De?cient Subjects”, Acta Otolaryngol 95, pp. 199—210,
`1983.
`Mary E. Tinetti, et al., “Fall Risk Index for Elderly Patients
`Based on Number of Chronic Disabilities”, Am. J. Med.,
`vol. 80, pp. 429—434, Mar. 1996.
`F. OWen Black, et al., “Effects of Unilateral Loss of Vesti
`bular Function on the Vestibulo—Ocular Re?ex and Postural
`Control”, Ann. Otol. Rhinol. Laryngol. 98, pp. 884—889,
`1989.
`
`Emily A. Keshner & John H]. Allurn, “Muscle Activation
`Patterns Coordinating Postural Stability from Head to Foot”,
`in “Multiple Muscle Systerns: Biornechanics and Movement
`Organization”, pp. 481—497, (J .M. Winters & S.L.—Y. Woo,
`eds., 1990).
`Karnran Barin, “Dynarnic Posturography: Analysis of Error
`in Force Plate Measurement of Postural SWay”, IEEE Eng.
`in Med. Biol., vol. 11, No. 4, pp. 52—56, Dec., 1992,
`D. Perennou, et al., “Optoelectronic assessment of upper
`body sWay in erect posture: validation for 3—D stabilorn
`
`etry”, in “Vestibular and neural front”, pp. 57—60, Taguchi, et al., eds., 1994).
`
`Y. Ehara, et al., “Comparison of the performance of 3D
`camera systems”, Gait & Posture, vol. 3, pp. 166—169, Sep.
`1995.
`Thomas E. Prieto, et al., “Measures of Postural Steadiness:
`Differences BetWeen Healthy Young and Elderly Adults”,
`IEEE Trans. Biorned. Eng., vol. 43, No. 9, pp. 956—966, Sep.
`1996.
`
`Ex. 1007 / Page 2 of 19
`
`

`
`U.S. Patent
`
`Jul. 6, 1999
`
`Sheet 1 0f5
`
`5,919,149
`
`10
`\
`
`16
`l
`
`Memor
`y
`
`Printer/
`Plotter
`
`:
`
`Angular
`12
`Rate
`Transducer /
`
`A
`
`v
`
`14
`\
`
`20
`l
`
`18
`\
`
`m :
`
`NC
`
`>
`
`=
`
`Operator's
`Display
`
`24
`/
`
`Subject's
`Visual
`Display
`
`26
`/
`
`Subject's
`Auditory
`Feedback
`
`‘
`
`<
`
`Operator's
`input
`
`Subject's
`Tactical
`Feedback
`
`22_
`
`,
`
`28 __
`
`_
`
`>
`
`I
`s
`Vestibular
`30— Feedback
`
`Fig.1
`
`Ex. 1007 / Page 3 of 19
`
`

`
`U.S. Patent
`U.S. Patent
`
`Jul. 6, 1999
`Jul. 6, 1999
`
`Sheet 2 of5
`Sheet 2 0f5
`
`5,919,149
`5,919,149
`
`Ex. 1007/ Page 4 of 19
`
`Ex. 1007 / Page 4 of 19
`
`

`
`U.S. Patent
`
`Jul. 6, 1999
`
`Sheet 3 0f5
`
`5,919,149
`
`40
`/
`
`Path D99
`300
`
`°/o cone of
`
`RMS Velocity
`
`250
`200
`
`Stability
`80
`
`64
`
`20
`
`60
`40
`
`20
`
`0
`
`74
`
`15
`10
`
`5
`
`0
`
`55
`
`
`
`150
`100
`
`50
`
`O
`
`43
`
`Trunk Angular Velocity
`
`Deg/Sec
`Pitch
`40
`20
`
`
`
`0
`
`2°
`
`40
`
`20
`
`0
`
`20
`
`40
`Deg/Sec
`Roll
`
`Fig.3
`
`44
`
`6f
`
`Roll
`Stability
`
`Pitch
`Stability
`
`Left
`
`Right
`
`Forw Backw
`
`deg
`
`/5*?eg
`
`%‘
`
`§
`
`$
`
`s
`
`S
`
`5
`
`S
`
`3
`
`L #1
`69
`
`Ex. 1007/ Page 5 of 19
`
`Ex. 1007 / Page 5 of 19
`
`

`
`U.S. Patent
`
`Jul. 6, 1999
`
`Sheet 4 of5
`
`5,919,149
`
`94_
`
`/U
`
`106
`
`I
`
`l
`
`108
`
`\98
`
`100
`
`“N 104
`
`II:
`\
`108
`
`Fig.5
`
`J
`
`\
`96
`
`Ex. 1007 / Page 6 of 19
`
`

`
`U.S. Patent
`
`Jul. 6, 1999
`
`Sheet 5 of5
`
`5,919,149
`
`—122
`
`———1 24
`
`—123
`
`—130
`
`134
`
`———1 36
`
`———1 38
`
`146
`
`140
`l
`\
`Update Feedback Display (Fig. 5)
`l
`142 - Issue Fall Warnings
`t
`144 _ Log Fa" Warnings
`
`:
`
`lnitialize Sensors, Displays, and Interfaces --12O
`l
`Begin Shell Program
`l
`Select Task Type
`l
`Select Cone of Stability
`l
`Set Task Parameters
`l
`Begin Real-Time Data Collection and Reduction *132
`l
`Zero Upright Position
`l
`Sample Angular Velocity Sensors
`l
`integrate for Angular Position
`i
`Update Operator Display (Fig. 3)
`148
`l
`End Real-Time Data Collection )
`Begin Final Data
`Reduction and Display
`l
`Display Results and
`150 -- Comparison Data
`l
`Store Results in
`152 — Storage Medium
`l
`Print Results
`
`Modify Feedback
`‘ Gain Sensitivity
`/
`156
`
`154 —-
`
`Fig.6
`
`Ex. 1007 / Page 7 of 19
`
`

`
`1
`METHOD AND APPARATUS FOR ANGULAR
`POSITION AND VELOCITY BASED
`DETERMINATION OF BODY SWAY FOR
`THE DIAGNOSIS AND REHABILITATION OF
`BALANCE AND GAIT DISORDERS
`
`This application claims the bene?t of US. Provisional
`Application No. 60/029,010, ?led Oct. 24, 1996.
`
`FIELD OF THE INVENTION
`
`This invention pertains generally to methods and devices
`for providing non-invasive testing of the postural sWay of a
`human subject during standing or movement tasks, and more
`particularly to such methods and devices that employ direct
`measurement of body position using displacement or motion
`transducers or other sensing devices attached to the body.
`This invention also pertains generally to prosthetic methods
`and devices for aiding in the rehabilitation of balance and
`gait de?cits and, more particularly, to such methods and
`devices that provide feedback of postural information to the
`subject.
`
`10
`
`15
`
`BACKGROUND OF THE INVENTION
`
`Individuals Who suffer from a balance control de?cit are
`abnormally prone to falling and have poor gait control When
`Walking or engaging in other movement tasks. A balance
`control de?cit may be the result of a Wide variety of sensory
`and/or motor disorders that impair the posture and equilib
`rium control of the subject. In order to make a correct
`assessment of a subject’s balance de?cit, and thereby to take
`remedial measures, an examining physician, or physical
`therapist, must determine the subject’s balance control abil
`ity for a number of motor tasks, such as standing, getting up
`out of a chair, Walking doWn steps, etc. By observing the
`subject performing such motor tasks, the physician may be
`able to determine if the subject’s balance control is Within
`normal limits and, if not, hoW best to bring balance control
`near or Within normal limits again. HoWever, to provide a
`more accurate and objective assessment of the individual’s
`sensory and motor components of posture and equilibrium,
`a test system Which provides an objective quanti?able
`assessment of balance control is required.
`Quantitative information on the human sense of balance
`can be obtained using a variety of methods and devices.
`Quantitative information on the efficacy of the human sense
`of balance can be obtained by the electrophysiological
`measurement of eye movements or of the postural responses
`of the limbs. A balance control de?cit is indicated if a
`response is outside of the limits expected for individuals
`having a normal balance function. Quantitative postural
`information may also be obtained by measuring contractile
`activity of the muscles generating the internal body forces
`for maintaining the equilibrium position using electromyo
`graphic (EMG) recordings.
`Balance de?cits are, hoWever, normally quanti?ed by
`recording body sWay, i.e., the displacement of the body from
`the equilibrium position. Quanti?cation of the postural sWay
`of a subject is knoWn as “stabilometry” or “posturography”.
`One such method for quantifying balance de?cits involves
`the measurement of body sWay in terms of displacement of
`the center of foot pressure (CFP), sometimes termed “center
`of force”, generated by the inherent instability of a test
`subject standing on a ?xed support surface. CFP is computed
`from the signals provided by force transducers Which are
`typically embedded in the four corners of the support
`surface. The force transducer outputs are employed to obtain
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`5,919,149
`
`2
`a projection, on the support surface platform, of the resultant
`forces acting at the subject’s center of gravity. An anterior,
`front-to-back, projection is obtained by assuming that the
`difference betWeen the force detected by the for and aft force
`transducer-pairs equals torque about the ankle joint. The
`anterior projection is obtained by dividing the ankle torque
`by the total vertical force. This calculation also assumes that
`the upright body can be represented by a simple upright
`pendulum. Thus, only the effect of movement at the ankle
`joints is considered, the effect of movements at the knee and
`hip joints is ignored. A similar calculation employs the
`signals provided by the lateral pairs of force transducers on
`each side of the support platform to obtain a lateral force
`projection. The vectorial sum of the anterior and lateral force
`projections equals the CFP. As body sWay frequencies
`exceed 0.2 HZ, hoWever, this method for estimating the
`movement of the body’s center of gravity based on CFP
`becomes increasingly inaccurate, because oscillations of the
`upper body enter the CFP measurements as inertial reaction
`forces. Furthermore, if the multi-link nature of the body is
`ignored, serious errors in understanding a subject’s balance
`disorders can occur.
`Investigators have used different types of force platforms
`to analyZe postural sWay. Some such force platforms are
`speci?cally targeted toWards tests for analyZing balance
`disorders caused by vestibular de?cits. Quantitative exami
`nation of CFP data suggests that subjects having a unilateral
`vestibular balance de?cit, e.g., a balance de?cit caused
`solely by impairment of the vestibular end organs in the ear,
`perform Within normal ranges When tests are employed
`using a ?xed force sensitive support surface to perform the
`balance tests. For this reason, techniques have been intro
`duced Which make the control of spontaneous sWay by a
`subject positioned on the CFP measuring support surface
`more dif?cult. These techniques make quanti?cation of a
`vestibular balance de?cit easier by interrupting the non
`vestibular sensory inputs that the subject may otherWise use
`to maintain his balance. One such technique involves mov
`ing the support surface so that it is tilted (forWard or
`backWard) in relation to changes in the subject’s CFP. This
`type of controlled platform instability may be obtained using
`a purely mechanical device, or With a more ?exible elec
`tronic and computer controlled motor unit. The movement of
`the support surface platform disrupts the somatosensory
`inputs Which Would otherWise be available to the subject. A
`second technique involves the use of a movable visual
`surround, Which surrounds the subject, and Which is moved
`to folloW the subject’s body sWay, as estimated by CFP
`measurement of the subject. This technique disrupts the
`visual stabiliZation inputs used by the subject to maintain
`balance control. By disrupting the somatosensory and visual
`inputs, a test procedure for analyZing a subject’s balance
`control is able to focus more particularly on the vestibular
`balance control mechanism. Examples of such test systems
`and procedures are described in more detail in US. Pat. Nos.
`4,738,269, 5,052,406, and 5,303,715 issued to Nashner, et
`al. Analysis of tests employing these improvements to CFP
`sWay quanti?cation have indicated that destabiliZation of the
`support surface beneath the subject provides a major diag
`nostic improvement. HoWever, destabiliZing a visual sur
`round by moving it in relation to the CFP provides little
`additional diagnostic information as far as vestibular balance
`de?cit is concerned.
`A major draWback of CFP based systems for quantifying
`body sWay is that the freedom of movement of the subject
`is limited by the fact that the subject must remain in contact
`With the force sensing support surface. Thus, the physician’s
`
`Ex. 1007 / Page 8 of 19
`
`

`
`5,919,149
`
`3
`ability to determine a subject’s balance control While per
`forming a variety of motor tasks is limited by the CFP
`method. Amore ?exible system that may be used to measure
`body sWay employs light-Weight light-emitting sources that
`are mounted on a subject’s body. HoWever, such three
`dimensional camera based systems are typically prohibi
`tively expensive for most physical therapy practices special
`iZing in rehabilitation of gait and balance de?cits. Moreover,
`these systems also have a number of technical drawbacks,
`including excessive computer poWer requirements, limited
`on-line capabilities, sensitivity to interfering light sources,
`and limited range of operation. Thus, although such systems
`are capable of quantifying gait and other dynamic postural
`abnormalities, Which cannot be achieved using CFP mea
`suring support surfaces, this advantage is outWeighed by the
`price and ease-of-operation advantages of more conven
`tional CFP systems. Thus, CFP systems are still the system
`of choice for quantifying the body sWay of subjects With
`balance de?cits.
`After a balance de?cit has been diagnosed and quanti?ed,
`a physician may prescribe remedial measures to bring the
`subject’s balance control near or Within normal limits. The
`physician may prescribe medication that reduces the action
`of peripheral senses on the brain. Alternatively, the physi
`cian may prescribe a course of physical therapy, Which Will
`typically last at least several Weeks, With the object of
`training the subject’s brain to deal With a reduced sense of
`balance When trying to maintain the body upright and
`prevent a fall. HoWever, neither of these techniques Will
`have an immediate rehabilitory effect on the subject’s bal
`ance de?cit. Moreover, medication can have side effects, and
`can also reduce the capability of the brain to process balance
`information from the peripheral senses. Acourse of physical
`therapy requires a long training period Which may extend
`over more than tWo months. These dif?culties and limita
`tions associated With conventional remedial measures for
`dealing With balance de?cits are most problematic When the
`subject is older and likely to have a falling tendency.
`In the ?eld of hearing, Which is physiologically related to
`that of balance, tWo types of prostheses are used to augment
`a subject’s hearing ability. The ?rst type of device involves
`augmenting the sound Waves in the external ear canal so that
`they have greater excursions When they reach the inner ear
`Where they are transduced into electrical signals that reach
`the brain. The second type of device for improving hearing
`ability involves direct electrical stimulation of the auditory
`nerve in the inner ear. For the sense of balance, hoWever, in
`Which sensory signals from different neurophysiological
`systems, including a major input from the vestibular system
`of the inner ear, are combined by the brain to yield a unitary
`sense of balance, no prosthetic device exists.
`
`10
`
`15
`
`25
`
`35
`
`4
`body and maintaining the angular position and angular
`velocity of the body Within a cone of angular stability. Once
`this cone of stability is exceeded, With an excessive angular
`velocity, normal individuals Will respond by correcting the
`trunk position Within 200 milliseconds.
`The present invention employs light-Weight Wearable
`body sWay sensors, such as velocity transducers, that are
`preferably attached to the upper body, e.g., the chest, of a
`subject. The sensor output signals are transformed into
`detailed angular displacement and velocity information. The
`subject need not remain in contact With a support-surface in
`order for body sWay measurements to be made, therefore,
`subject movement is not restricted. Moreover, the body sWay
`sensors employed in the present invention are not limited in
`accuracy by the assumptions used for calculating body sWay
`based on CFP from the signals provided by force transducers
`embedded in a force plate support surface.
`Signals from the body sWay sensors on the subject are
`provided to a microprocessor based system processor. The
`system processor is programmed to transform the angular
`position and velocity information provided by the sensors
`into useful information formats that are displayed to an
`operator on an operator’s display unit. Quanti?ed body sWay
`information that may be provided to the operator as part of
`the operator’s display includes: time histories of the sub
`ject’s angular sWay deviations and angular velocity in the
`roll and pitch directions, histograms of the sWay deviations
`and sWay velocities over an examination trial period for the
`roll and pitch directions, a measurement of the total vectorial
`angular path transversed by the subj ect’s upper body during
`the examination trial period, and measures of maximum
`instability in the roll and pitch directions. The operator’s
`display may also provide for comparisons betWeen exami
`nation trial results from different trials or betWeen exami
`nation trial results and body sWay information obtained from
`a normal sample population. Moreover, the operator’s dis
`play may provide an objective measure of the subject’s
`stability by comparison of the subject’s Zero-velocity cone
`of stability With the maximum trunk sWay angle deviations
`occurring during the examination trial period. Since the
`body sWay sensors employed by the present invention do not
`interfere With subject movement, this detailed information
`may be obtained for examination trials involving the per
`formance of a Wide variety of movement tasks by the
`subject.
`The system processor of the present invention may also be
`programmed to provide rehabilitory postural feedback to the
`subject based upon the body sWay angle and sWay velocity
`information obtained from the body sWay sensors. This
`feedback may be in the form of visual, auditory, or tactile
`stimulation, or may be provided in the form of an electrical
`signal that is used to directly stimulate the vestibular nerve.
`A single type of feedback may be used, or different types of
`feedback may be provided to a subject in combination. The
`rehabilitory feedback immediately augments the balance
`signals normally used by the subject’s brain to help stabiliZe
`body sWay and improve balance. The feedback gain, the
`amount of feedback provided to the subject relative to the
`measured body sWay angle and angular velocity, may be
`adjusted by the system operator. The information provided
`on the operator’s display provides an objective measure for
`determining improvements in balance brought about by the
`application of feedback, and by altering feedback gains.
`For visual feedback, a visual feedback system incorpo
`rated in a pair of lightWeight eyeWear may be used. An
`imaging system mounted in the eyeWear is used to project a
`visual feedback display generated by the system processor
`
`SUMMARY OF THE INVENTION
`
`The present invention provides a method and apparatus
`for performing non-invasive, sensitive, and reliable tests for
`the presence of abnormalities in the postural sWay of a
`human subject during standing or movement tasks. A
`method or device in accordance With the present invention
`may be used as both a diagnostic and a rehabilitory tool for
`subjects Who are prone to abnormal falling or Who Wish to
`improve their movement control. The present invention may
`speci?cally be used to provide prosthetic feedback to aid in
`the rehabilitation of balance and gait de?cits.
`The method and apparatus of the present invention is
`based on the ?nding that the unitary sense of balance
`computed by the human brain involves monitoring the upper
`
`55
`
`65
`
`Ex. 1007 / Page 9 of 19
`
`

`
`5,919,149
`
`10
`
`15
`
`25
`
`35
`
`45
`
`5
`into the eye of the wearer of the eyeWear. Because the
`vieWer’s vision is not otherwise restricted by the eyeWear,
`the projected display appears to ?oat in the normal visual
`?eld of the subject. The subject is thus able to see both the
`World around him and the display simultaneously. The visual
`feedback display preferably includes a horiZontal bar that
`moves in relation to the forWard and backWard (pitch) and
`left and right (roll) sWay of the subject’s upper body. The
`Width of the horiZontal bar increases or decreases in relation
`to the vectorial combination of the roll and pitch velocities
`of the subject’s upper body. As the subject’s angular sWay
`approaches the subject’s angular cone of stability, a portion
`of the horiZontal bar ?ashes to indicate to the subject that he
`is in danger of falling. The sensitivity of the movement and
`Width of the horiZontal bar to the sWay angle and sWay
`velocity of the subject, as Well as the proximity of the
`subject’s sWay to the cone of stability necessary for a
`Warning to be indicated, are visual feedback gain
`parameters, Which may be adjusted by the operator to help
`improve the subject’s control of body sWay, and therefore
`improve the subj ect’s balance control for selected movement
`tasks.
`For auditory feedback, the information Which is visually
`displayed When used for visual feedback is presented to the
`subject aurally. Roll and pitch angular displacements of the
`subject may be provided as frequency modulations around
`tWo different audible tone center frequencies, e.g., 500 HZ
`and 1500 HZ. The velocity of angular sWay may be presented
`as an increased or decreased tone volume. AWarning that the
`subject is approaching his cone of stability can be given in
`the form of an audible Warning signal that is provided to the
`subject. The depth of frequency modulation, loudness of the
`auditory signals, and conditions for providing the Warning
`signal, are auditory feedback gain parameters Which may be
`set by the operator to help improve the subject’s control of
`body sWay, and therefore improve the subject’s balance
`control for one or more movement tasks.
`Tactile feedback may be provided by vibrators that are
`used to convey a sense of rotation of the subject’s torso. For
`example, tWo vibrators placed on the subject may be used to
`convey a sense of forWard and backWard sWay by modula
`tion of the frequency of vibration With respect to the
`measured sWay velocity, and by varying the amplitude of
`vibration With respect to the sWay angle. Aseparate vibrator
`may be used to signal the subject that the sWay angle has
`exceeded the limits of safety for the subject. Each of these
`parameters, modulation frequency, amplitude of vibration,
`and the body sWay safety limit, is a tactile feedback gain
`parameter that may be adjusted by an operator to improve
`the subject’s control of body sWay and therefore improve the
`subject’s balance control for one or more movement tasks.
`Body sWay and sWay velocity feedback signals may also
`be provided as varying electrical signals Which are used to
`directly stimulate the vestibular nerve. Such stimulation is
`sensed by the subject as a change in the angular and/or linear
`position of the head. Feedback signals for such direct
`electrical stimulation are transmitted transcutaneously to an
`implantable device directly connected via electrodes to the
`close proximity of the vestibular nerve or to the nerve itself.
`The pulse rate, amplitude, and duty cycle of the electrical
`stimulation signal at the electrodes is varied With respect to
`the sWay angle and angular velocities that are determined by
`the system processor based on the signals provided by the
`body sWay sensors attached to the subj ect’s upper body. The
`relationship of the signal amplitude, pulse rate, and duty
`cycle to the body sWay angles and angular velocity are
`among the adjustable feedback gain parameters for this type
`of feedback.
`
`6
`Besides providing a more accurate and reliable method
`and apparatus for testing for the presence of balance
`disorders, and for providing rehabilitation feedback to
`improve such disorders, the present invention may also be
`used to monitor the safety of a large number of subjects Who
`are in danger of falling, as Well as for providing a record of
`hoW and When a subject, for example, in a home for the
`elderly, actually fell. In accordance With the present
`invention, a subject’s body sWay angle and sWay angular
`velocity is measured using light-Weight Wearable body sWay
`sensors that don’t restrict the subject’s movement. Thus,
`continuous subject monitoring may be obtained, and feed
`back provided, Without signi?cantly interfering With the
`subject’s day-to-day activities. The information provided by
`the Wearable body sWay sensors may be continuously pro
`vided to a system processor attached to the subject and
`stored therein for future analysis. Moreover, the body sWay
`signals provided by the body sWay sensors Worn by multiple
`subjects may be provided, via conventional Wireless trans
`mission techniques, to a “remote” system processor,
`Whereby the safety of a large number of subjects may be
`monitored simultaneously. Such a system may be pro
`grammed to provide Warnings to the operator When one of
`the subjects exceeds a pre-de?ned body sWay safety limit for
`that subject, indicating that the subject is in danger of falling.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a schematic block diagram of an angular position
`and velocity based body sWay diagnosis and rehabilitation
`system in accordance With the present invention.
`FIG. 2 is a schematic illustration of a human subject
`Wearing body sWay sensors that are used to provide body
`sWay and angular velocity data in roll and pitch directions,
`and an exemplary visual body sWay angle and angular
`velocity feedback device used for providing improved bal
`ance control in accordance With the present invention.
`FIG. 3 is an illustration of an exemplary operator’s
`display for providing body sWay angle and angular velocity
`information to an operator in accordance With the present
`invention.
`FIG. 4 is an illustration of an exemplary visual body sWay
`angle and angular velocity feedback system in accordance
`With the present invention.
`FIG. 5 is an illustration of an exemplary visual body sWay
`angle and angular velocity feedback display in accordance
`With the present invention.
`FIG. 6 is a How chart illustrating the steps of an exemplary
`system processor control program algorithm for sampling
`body sWay sensors, providing an operator’s display, and
`providing visual body sWay angle and angular velocity
`feedback in accordance With the present invention.
`
`55
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`The present invention provides a method and apparatus
`for signi?cantly improving the speci?city, accuracy and
`reliability of non-invasive diagnostic tests for the presence
`of balance and gait disorders. The present invention also
`provides a rehabilitory method and apparatus for improving
`a subj ect’s balance and gait control. An angular position and
`velocity based body sWay diagnostic and rehabilitory system
`for monitoring body sWay and for providing body sWay
`feedback to a subject to help improve the subject’s control
`of body sWay is illustrated generally at 10 in FIG. 1.
`Light-Weight Wearable body sWay sensors 12 are attached to
`
`65
`
`Ex. 1007 / Page 10 of 19
`
`

`
`5,919,149
`
`7
`the upper body of a subject and provide body sWay signals
`to a system processor 14 Which derives body sWay angle and
`body sWay angular velocity information therefrom. As Will
`be discussed in more detail below, various types of body
`sWay sensors, including angular velocity transducers, may
`be used to provide body sWay signals indicative of the upper
`body motion of a subject to the system processor 14.
`The system processor 14 may be implemented as a
`conventional microprocessor based computer system having
`computer memory 16, an operator’s display unit 18, e.g., a
`standard 14-inch computer display console, a printer or
`plotter 20, and an operator’s input device 22, such as a
`conventional computer keyboard. The processor memory 16
`may include short-term memory, e.g., RAM, as Well as
`long-term memory, such as is provided by a conventional
`magnetic disk storage system. The system processor’s
`memory 16 operates in a conventional manner to store the
`programmed series of instructions and algorithms that con
`trol operation of the system processor 14 and to store data
`generated by the system processor.
`In accordance With the present invention, the system
`processor 14 is programmed to transform the body sWay
`signals provided by the body sWay sensors 12 into useful
`body sWay angle and body sWay angular velocity informa
`tion formats. The body sWay angle and body sWay angular
`velocity information is displayed by the system processor 14
`in the form of an operator’s display that is presented to the
`operator on the operator’s display unit 18. From this for
`matted information, the system operator, e.g., a physician, is
`able to analyZe the body sWay of a subject during the
`performance of various motor tasks, to thereby diagnose the
`existence of a balance or gait de?cit. Ahard copy of the body
`sWay information provided on the operator’s display unit 18
`may be obtained using the system printer or plotter 20. It
`should be noted that body sWay sensors 12 may also be
`attached to other portions of the subject’s body, such as the
`Waist, upper leg, or loWer leg, to provide info