United States Patent [19J
`Arc el us
`
`I lllll llllllll Ill lllll lllll lllll lllll lllll 111111111111111111111111111111111
`US006149602A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,149,602
`*Nov. 21, 2000
`
`[54] USER-WORN ELECTROCARDIOGRAM
`VIEWER DEVICE
`
`[76]
`
`Inventor: Almudena Arcelus, 147 Longwood
`Ave. #2, Brookline, Mass. 02146
`
`[ * ] Notice:
`
`This patent issued on a continued pros(cid:173)
`ecution application filed under 37 CFR
`1.53( d), and is subject to the twenty year
`patent term provisions of 35 U.S.C.
`154(a)(2).
`
`[21] Appl. No.: 08/825,828
`
`[22]
`
`Filed:
`
`Mar. 29, 1997
`
`[60]
`
`[51]
`[52]
`[58]
`
`[56]
`
`Related U.S. Application Data
`Provisional application No. 60/024,788, Sep. 10, 1996.
`Int. Cl.7 ................................................... A61B 5/0432
`U.S. Cl. ............................................. 600/523; 600/509
`Field of Search ..................................... 600/509, 520,
`600/523; 607/32
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`8/1978 Schmid ................................... 600/523
`4,108,166
`4,120,294 10/1978 Wolfe ...................................... 600/523
`4,635,646
`1/1987 Gilles et al.
`............................ 600/509
`4,791,933 12/1988 Asai et al.
`.............................. 600/509
`3/1989 Ascher .................................... 600/523
`4,809,705
`4,825,874
`5/1989 Uhlemann ............................... 600/523
`4,889,134 12/1989 Greenwold et al. .................... 600/523
`5,003,984
`4/1991 Muraki et al. .......................... 600/523
`4/1994 Koestner et al.
`......................... 607/32
`5,300,093
`5,304,209
`4/1994 Adams et al.
`............................ 607/32
`5,336,245
`8/1994 Adams et al.
`............................ 607/32
`
`5,343,869
`5,383,912
`5,417,222
`5,577,510
`5,620,472
`5,623,926
`5,682,902
`5,738,104
`
`9/1994 Pross et al. ............................. 600/523
`1/1995 Cox et al. ................................. 607/32
`5/1995 Dempsey et al. ....................... 600/509
`11/1996 Chittum et al. ......................... 600/523
`4/1997 Rahbari . .... ... ... ... ... ... .... ... ... ... ... . 607 /27
`4/1997 Weiss ...................................... 600/509
`11/1997 Herleikson .............................. 600/521
`4/1998 Lo et al.
`................................. 600/509
`
`Primary Examiner-Kennedy Schaetzle
`Attorney, Agent, or Firm-Fish & Richardson, P.C.
`
`[57]
`
`ABSTRACT
`
`A user-worn electrocardiogram viewer acquires data relating
`to a user's electrocardiogram signal. The viewer receives the
`electrocardiogram signal (by wired or wireless link) and
`displays it on a self-contained display screen (10). The
`viewer provides switches (12, 14, 16) operated by the user
`to adjust the display and processing of the electrocardiogram
`signal through the selection of parameters such as size of the
`electrocardiogram signal to be displayed, bandwidth of the
`electrocardiogram signal to be processed, and speed of the
`electrocardiogram signal when displayed through the screen.
`The viewer also includes a storage capability to store the
`electrocardiogram signal for later recall and analysis. The
`viewer also includes an infrared port (50) to communicate
`with the serial port of other devices. The viewer provides
`other support functions to the user such as display of heart
`rate, visual display of QRS-detection, and time and date
`information. The viewer also provides the user with the
`capability to set a heart rate target zone and heart rate trend.
`The viewer is easy to operate by the user and suitable for
`attachment (38, 40) to the user's upper limb, preferably the
`wrist.
`
`20 Claims, 11 Drawing Sheets
`
`28
`
`18
`
`46
`
`50
`
`IPR2018-00294
`Apple Inc. EX1008 Page 1
`
`

`

`U.S. Patent
`
`Nov. 21, 2000
`
`Sheet 1 of 11
`
`6,149,602
`
`18
`
`50
`
`46
`
`40
`
`FIG. l
`
`IPR2018-00294
`Apple Inc. EX1008 Page 2
`
`

`

`FIG. 2
`
`INPUT
`1----c=J PROTECTION
`
`ECG
`INSTRUMENTATION
`AMPLIFIER
`
`SIGNAL
`CONDITIONING
`
`44
`
`26
`
`30
`
`42
`
`12
`
`14
`
`16
`
`58
`
`NON VOLATILE
`MEMORY
`
`32
`
`10
`
`MICROCONTROLLER
`WITH
`
`6 1 RAM l 1 EEPROM 1 1
`SE~~AL 1
`
`50
`
`IR
`
`34
`
`46
`
`DISPLAY
`
`BATTERY-BASED
`POWER SUPPLY
`
`ON/OFF
`
`d •
`\JJ.
`•
`~
`~ ......
`~ = ......
`
`z
`0
`~
`N
`"'"" ~
`N c c c
`
`'Jl =(cid:173)~
`~ .....
`N
`0 .....,
`"'""
`"'""
`
`0--,
`....
`~
`~
`\C
`....
`
`0--, = N
`
`IPR2018-00294
`Apple Inc. EX1008 Page 3
`
`

`

`U.S. Patent
`
`Nov. 21, 2000
`
`Sheet 3 of 11
`
`6,149,602
`
`/~-..
`
`Y"<__-- "'
`/---(
`\..
`'
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`I
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`I
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`
`I
`\ \
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`I
`~ I
`\l
`\
`\
`
`\ \
`\
`
`IPR2018-00294
`Apple Inc. EX1008 Page 4
`
`

`

`U.S. Patent
`
`Nov. 21, 2000
`
`Sheet 4 of 11
`
`6,149,602
`
`FIG.4
`
`IPR2018-00294
`Apple Inc. EX1008 Page 5
`
`

`

`FIG. 5
`
`26
`
`60
`
`30
`
`42
`
`1
`
`INPUT
`1 PROTECTION
`CIRCUIT
`
`ECG
`INSTRUMENTATION
`AMPLIFIER
`
`SIGNAL
`CONDITIONING
`
`32
`
`50
`
`IR
`
`MICROCONTROLLER
`
`54
`
`FM
`TRANSMITTER
`
`34
`
`BATTERY
`BASED
`POWER SUPPLY
`
`ON/OFF
`
`46
`
`d •
`\JJ.
`•
`~
`~ ......
`~ = ......
`
`z
`0
`~
`N
`'"""' ~
`
`N c c c
`
`'Jl =(cid:173)~
`~ .....
`Ul
`0 .....,
`'"""'
`'"""'
`
`0--,
`....
`~
`~
`\C
`....
`
`0--, = N
`
`IPR2018-00294
`Apple Inc. EX1008 Page 6
`
`

`

`FIG. 6
`
`32
`
`NON VOLATILE
`MEMORY
`50
`
`FM RECEIVER
`
`MICROCONTROLLER
`
`IR
`
`58
`
`34
`
`10
`
`DISPLAY
`
`BATTERY
`BASED
`POWER SUPPLY
`
`46
`
`ON/OFF
`
`d •
`\JJ.
`•
`~
`~ ......
`~ = ......
`
`z
`0
`~
`N
`'"""' ~
`
`N c c c
`
`'Jl =(cid:173)~
`~ .....
`O'I
`0 .....,
`'"""'
`'"""'
`
`0--,
`....
`~
`~
`\C
`....
`
`0--, = N
`
`IPR2018-00294
`Apple Inc. EX1008 Page 7
`
`

`

`U.S. Patent
`
`Nov. 21, 2000
`
`Sheet 7 of 11
`
`6,149,602
`
`START
`
`FIG. 7A
`
`100
`
`110
`
`INITIALIZE:
`- VARIABLES
`- INTERRUPT
`- DISPLAY
`- AID CONVERTER
`- SERIAL PORT
`
`ENABLE
`INTERRUPT
`SERVICE ROUTINE
`
`No
`
`No
`
`No
`
`To FIG. 7B -- Box 150
`
`From FIG. 7B -- Box 160
`and Box 165
`
`DISPLAY ECG
`
`125
`
`135
`
`UPDATE HEART
`RATE
`
`145
`
`IPR2018-00294
`Apple Inc. EX1008 Page 8
`
`

`

`U.S. Patent
`
`Nov. 21, 2000
`
`Sheet 8 of 11
`
`6,149,602
`
`FIG. 7B
`
`From FIG. 7A-- Box 140
`and Box 145
`
`UPDATE
`MISCELLANEOUS
`FUNCTIONS
`
`155
`
`Yes
`
`SEND DATA TO
`SERIAL PORT
`
`165
`
`No
`
`To FIG. 7 A -- Box 120
`
`IPR2018-00294
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`
`

`

`U.S. Patent
`
`Nov. 21, 2000
`
`Sheet 9 of 11
`
`6,149,602
`
`FIG. 8
`
`INTERRUPT
`ROUTINE GETS
`ACTIVATED
`
`GET SAMPLE
`FROMA/D
`CONVERTER
`
`ACTIVATE 50 HZ
`OR 60 HZ NOTCH
`FILTER
`
`SA VE SAMPLE IN
`MEMORY
`
`ACTIVATE QRS
`DETECTOR
`ROUTINE
`
`DEBOUNCE AND
`CHECK USER
`SWITCHES
`
`UPDATE SWITCH
`FLAGS
`
`UPDATE TIMERS
`
`RETURN TO
`MAIN ROUTINE
`
`200
`
`210
`
`220
`
`230
`
`240
`
`250
`
`260
`
`IPR2018-00294
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`
`

`

`U.S. Patent
`
`Nov. 21, 2000
`
`Sheet 10 of 11
`
`6,149,602
`
`FIG. 9A
`
`QRSDETECTOR
`ROUTINE GETS
`ACTIVATED
`
`COMPUTE ACTIVITY
`FUNCTION
`
`300
`
`310
`
`500
`
`Yes
`
`COMPUTE
`THRESHOLD
`
`To FIG. 9B -(cid:173)
`Box 510
`
`No
`
`410
`
`DECREMENT
`THRESHOLD DECAY PERIOD
`-
`-
`
`425
`
`~---Yes--- THRESHOLD /=2
`
`THRESHOLD=
`2 *NOISE
`
`No
`
`To FIG. 9B -- Box 440
`
`IPR2018-00294
`Apple Inc. EX1008 Page 11
`
`

`

`U.S. Patent
`
`Nov. 21, 2000
`
`Sheet 11 of 11
`
`6,149,602
`
`FIG. 9B
`
`From FIG. 9A -(cid:173)
`Box 500
`
`510
`
`DECREMENT
`REFRACTORY
`PERIOD
`
`From FIG. 9A-- Box 420,
`Box 430, and Box 435
`
`450
`
`Yes
`
`QRS_FLAG =TRUE
`REFRACTORY PERIOD = 100 MS
`
`530
`
`QRS FLAG= FALSE
`Yes THRESHOLD DECAY
`-
`-
`PERIOD= 100 MS
`
`RETURN TO
`SERVICE
`INTERRUPT
`ROUTINE
`
`460
`
`COMPUTE
`HEARTRATE
`
`IPR2018-00294
`Apple Inc. EX1008 Page 12
`
`

`

`6,149,602
`
`1
`USER-WORN ELECTROCARDIOGRAM
`VIEWER DEVICE
`
`This application claims benefit of Provisional Appln.
`60/024,788 filed Sep. 10, 1996.
`
`BACKGROUND-FIELD OF INVENTION
`
`This invention relates to equipment for displaying the
`electrical activity of the heart in a living body, and particu(cid:173)
`larly to a portable electrocardiogram viewer worn by the
`user.
`
`BACKGROUND-DESCRIPTION OF PRIOR
`ART
`
`Many portable devices have been described before that
`detect the electrical activity of the heart (henceforth elec(cid:173)
`trocardiogram signal). Many of them allow the user to see
`only a numeric of the heart rate computed from the detected
`electrocardiogram signal. Others may include a display of
`the actual electrocardiogram signal but do so in a very
`limited way: either for brief and limited periods of time or
`only for the convenience and use of the examiner and not the
`user. Furthermore, such devices do not allow the user
`unrestricted activity; therefore, they are not suitable for long
`term view of his/her electrocardiogram signal.
`
`Prior Art That Shows Only A Numeric of Heart
`Rate
`
`Righter et al (in U.S. Pat. No. 4,938,228) describe a
`wrist-watch device capable of detecting and transmitting an
`electrocardiogram signal but not displaying it to the user.
`The device is intended to transmit the electrocardiogram
`signal via telephone to medical personnel on a remote
`location. Similar aspects are described in subsequent patents
`of the same inventor (U.S. Pat. Nos. 5,191,891; 5,226,425;
`and 5,365,935).
`Mills et al (in U.S. Pat. No. 5,289,824) describe another
`wrist-watch device capable of detecting and transmitting an
`electrocardiogram signal. The device is intended to transmit
`the electrocardiogram signal via telephone to medical per(cid:173)
`sonnel on a remote location. Similar aspects are described in
`subsequent patents of the same inventors (U.S. Pat. Nos.
`5,317,269; 5,333,616; and 5,351,695).
`The devices described above are not intended nor are
`capable of displaying a continuous, real time electrocardio(cid:173)
`gram signal. Their purpose is to facilitate the acquisition and
`transmission of an electrocardiogram signal while providing
`the user with an indication of heart rate.
`
`Prior Art That Displays the Electrocardiogram
`Signal for the Convenience and Use of the
`Examiner or for Brief and Limited Periods of Time
`
`Geddes et al (in U.S. Pat. No. 4,606,352) describe a
`hand-held electrocardiogram monitor to be placed against
`the chest of a patient by placing and holding the monitor
`with one hand, on the chest of the patients while performing
`the reading of the electrocardiogram signal. This monitor is
`designed to be used by medical personnel in relation to
`medical emergencies and used for brief periods of time only.
`The user cannot see his/her electrocardiogram signal
`because the display is facing away from the user. In addition,
`the device will not be able to remain in position for long
`because it requires active support from the examiner to stay
`in place.
`Suzuki (in U.S. Pat. Nos. 5,002,062 and 4,974,599)
`describes other hand-held portable electrocardiogram moni-
`
`5
`
`2
`tors to be used by a physician or technician to perform a
`quick examination of the patient's heart or as an event
`recorder to be carried by the user during certain activities.
`These designs emphasize the use of a touch screen to
`facilitate operator interaction and a memory card for pre(cid:173)
`programmed functions and event recording. These designs
`are not intended for continuous view of the electrocardio(cid:173)
`gram signal by the user.
`Allain (in U.S. Pat. Nos. 5,002,064 and 5,029,590)
`10 describes a pocket-size monitor for electrocardiogram signal
`or electroencephalogram monitoring. This monitor is
`assumed to be carried in the hand by medical personnel or
`placed in an adjacent table while performing the reading. It
`is not designed to be operational while the patients engages
`15 in physical activity. This monitor is designed to be used by
`medical personnel. The design includes the use of electrodes
`attached to the device in such a way that the user cannot see
`his/her own electrocardiogram signal.
`Platt et al (in U.S. Pat. No. 5,123,419) describe a hand-
`20 held device suitable for electrocardiogram signal evaluation
`including pacemaker activity. This monitor is assumed to be
`carried in the hand by medical personnel or placed in an
`adjacent table while performing the reading. This monitor is
`not designed to be used or worn by the user.
`Fujii (in U.S. Pat. No. 5,213,107) describes a portable
`electrocardiogram monitor to be used by a physician or
`technician as an event recorder to be carried by the user
`during certain activities. The primary goal of this design is
`30 to reduce battery consumption. In order to better accomplish
`that goal, the device allows the health care provider to either
`acquire electrocardiogram signals from the patient or to
`display a previously stored electrocardiogram signal but not
`both simultaneously. The device is intended as an event
`35 recorder and not for continuous view of the electrocardio(cid:173)
`gram signal by the user.
`None of the above devices will actually facilitate to the
`user to see and evaluate his/her own electrocardiogram
`signal because they are primarily designed to be used by a
`40 medical/health care professional rather than by the user
`him/herself. These patented designs are intended to be
`evaluation aids under certain medical circumstances.
`Furthermore, they also share the disadvantage that are not
`designed to be used for extended periods of time. As a result,
`45 their shape, size, or mode of use make them difficult or
`impossible to simultaneously wear and operate by the user.
`
`25
`
`OBJECTS AND ADVANTAGES
`
`The present invention entirely focuses on the concept that
`50 the user wants to see his/her own cardiac activity without the
`need for any health-care professional. This is a radical
`departure from all prior art. This departure produces a design
`that opens up new and unexpected possibilities. As will be
`later described in the embodiments and claims, the user can
`55 now track his/her electrocardiogram signal from several
`sources (wired or wireless); for the first time an athlete can
`perform his/her activity while being able to constantly
`monitor his/her electrocardiogram signal; or a patient with
`an implantable device (e.g., pacemaker with telemetry
`60 capability) can now see his/her electrocardiogram signal at
`will. These and other new uses cannot be handled by the
`limitations found in the prior art.
`Hence, the present invention solves the aforementioned
`limitations and presents the user with a convenient (easy to
`65 operate, easy to wear) and continuous, real time display of
`his/her electrocardiogram signal, while at the same time
`allowing the user unrestricted activity.
`
`IPR2018-00294
`Apple Inc. EX1008 Page 13
`
`

`

`6,149,602
`
`4
`by the user in a variety of medical and non-medical situa(cid:173)
`tions. The device detects (wired mode) or receives (wireless
`mode) the electrocardiogram signal of the user, amplifies,
`filters, and converts it to a digital representation suitable for
`display and storage. The device provides switches, operated
`by the user, to adjust the display and processing of the
`electrocardiogram signal through the selection of parameters
`such as size of the electrocardiogram signal to be displayed,
`bandwidth of the electrocardiogram signal to be processed,
`10 and the speed of the electrocardiogram signal when dis(cid:173)
`played through the screen. The device also includes a
`storage capability to store the electrocardiogram signal for
`later recall and analysis. The device also includes an infrared
`port to communicate with the serial port of other devices.
`15 The device provides other support functions to the user such
`as display of heart rate, visual display of QRS-detection, and
`time and date information. The device also provides the user
`with the capability to set a heart rate target zone and heart
`rate trend. The device is easy to operate by the user and
`20 suitable for attachment to the user's upper limb, preferably
`the wrist.
`
`DESCRIPTION-MAIN EMBODIMENT-FIGS.
`1,2
`
`3
`Accordingly, one object and advantage of the invention is
`to provide an electrocardiogram signal display. Other
`objects and advantages are to provide such a display in a
`continuous, real time and clearly visible manner. Further
`objects and advantages are to provide a display that is easily 5
`worn and operated by the user with minimal interference
`with his/her activities.
`This invention may prove extremely valuable for indi(cid:173)
`viduals who want to have an active lifestyle but are not sure
`about the state of their cardiac activity and want to monitor
`it: from athletes in training to persons suffering from car(cid:173)
`diovascular disease to persons with implantable devices.
`The invention may also prove helpful when teaching about
`cardiac physiology.
`Still further objects and advantages will become apparent
`from a consideration of the ensuing description and accom(cid:173)
`panying drawings.
`DRAWING FIGURES
`FIG. 1 shows an external view of the preferred embodi(cid:173)
`ment of the invention.
`FIG. 2 shows the block diagram of the electronic com(cid:173)
`ponents of the preferred embodiment of the invention.
`FIG. 3 shows an example of use of the preferred embodi(cid:173)
`ment.
`FIG. 4 shows the external view of the chest belt with 25
`transmitter unit used in other embodiment of the invention.
`FIG. 5 shows the block diagram of the electronic com(cid:173)
`ponents contained in the chest belt (transmitter unit) of other
`embodiment of the invention.
`FIG. 6 shows the block diagram of the electronic com(cid:173)
`ponents contained in the viewer portion (receiver unit) of
`other embodiment of the invention.
`FIGS. 7A and 7B show the flowchart for the main
`software routine of the preferred embodiment of the inven(cid:173)
`tion.
`FIG. 8 shows the flowchart for the interrupt service
`routine of the preferred embodiment of the invention.
`FIGS. 9A and 9B show the flowchart for the QRS detector
`used in detecting the R waves and calculating heart rate in 40
`the preferred embodiment of the invention.
`
`FIG. 1 shows the external (user) view of the invention.
`The invention is an electronic device with a fiat display 10
`enclosed by a plastic housing 18. There are four switches in
`the lower part of the assembly: left switch 12, center switch
`14, right switch 16, and on/off switch 46. The electrode cable
`30 28 attaches to the left side of the assembly by a connector
`(not shown) and to two or three electrodes 44 on the other
`end. There are two flexible plastic straps attached to the
`assembly, an upper edge strap 38 and a bottom edge strap 40.
`There is also an infrared port 50 on the right side of the
`35 housing.
`FIG. 2 illustrates the functional blocks of the electronic
`components of the present invention. The invention has an
`electrode cable 28 attached through a connector, followed by
`an input protection circuit 26 and an electrocardiogram
`signal instrumentation amplifier 30. Next, there is a signal
`conditioning stage 42 connected to the microcontroller 32
`unit. Also connected to the microcontroller 32 are a liquid
`crystal display 10; three switches: left switch 12, center
`switch 14, and right switch 16; an infrared port 50; and
`additional non-volatile memory 58. Finally, there is a battery
`based power supply 34 circuit with an on/off switch 46.
`
`45
`
`OPERATION-MAIN EMBODIMENT-FIG. 1
`
`50
`
`The invention is a portable electronic device, battery
`operated, with a clearly readable display that can be easily
`worn by the user or attached to a nearby object (e.g. a bicycle
`frame). The essential operation of the device is to acquire the
`electrocardiogram signal from the user or patient and con-
`55 veniently display it within easy reach of the user.
`The operation of the device requires that the user attaches
`either two or three electrodes 44 to the his/her skin in any of
`the conventional electrode positions or other electrode posi(cid:173)
`tions. The user then connects those electrodes to the elec-
`60 trade cable 28 which in turn is connected to the housing 18.
`Finally, the user finds a position where to attach the housing
`18 to his/her body or a nearby object. Normally, the left or
`right arm or wrist is a suitable place. Other places may be
`possible, e.g., the waist, a nearby table, a bicycle frame, or
`65 a treadmill frame. With the device properly connected and
`attached, the user is able to see his/her electrocardiogram
`signal in a continuous manner.
`
`REFERENCE NUMERALS IN DRAWINGS
`
`10
`12
`14
`16
`18
`26
`28
`30
`32
`34
`38
`40
`42
`44
`46
`50
`52
`54
`56
`58
`60
`
`display
`left switch
`center switch
`right switch
`housing
`input protection circuit
`electrode cable
`instrumentation amplifier circuit
`microcontroller
`power supply
`upper edge strap
`bottom edge strap
`signal conditioning stage
`electrodes
`on/off switch
`infrared port
`chest belt
`FM transmitter
`FM receiver
`non-volatile memory
`dry electrodes
`
`SUMMARY OF THE INVENTION
`The invention is a portable electronic device with a
`clearly readable display that can be easily operated and worn
`
`IPR2018-00294
`Apple Inc. EX1008 Page 14
`
`

`

`6,149,602
`
`5
`The device automatically calculates and displays the heart
`rate (the number of beats per minute), displaying a small
`symbol (e.g., a heart) every time a beat is detected. Other
`functionality may include functions related to the electro(cid:173)
`cardiogram such as heart rate trends or convenience func-
`tions such as the time of day, the date, and low battery
`indication.
`
`5
`
`6
`The software consists of the following three routines: the
`main routine, the interrupt routine, and the QRS detector
`routine. Once the user has turned the device on, the main
`routine starts running indefinitely, only to be briefly inter(cid:173)
`rupted by the interrupt routine that receives a sample of the
`electrocardiogram signal and processes it through a digital
`notch filter and the QRS detector routine. Once the interrupt
`routine completes its tasks, the main routine resumes opera(cid:173)
`tion until the next interrupt takes effect.
`
`Main Routine-FIGS. 7A, 7B
`
`The main routine initializes the device, updates all items
`on the display, and sends data through the serial link when
`needed. FIGS. 7A and 7B depict a flowchart of the main
`15 routine. Block 100 initializes all the global variables, the
`timers, the display, the AID port, the serial port, and the
`interrupt service routine during the start up of the device.
`Block 110 enables the interrupt routine (described below).
`Block 120 checks one of the timers to check if it is time to
`20 update the electrocardiogram signal on the display. Block
`125 updates the display with the latest electrocardiogram
`data with the desired sweep speed (12.5, 25, or 50 mm/sec).
`Block 130 checks for the flags associated with the user
`switches. These flags are set in the interrupt routine. Block
`135 displays the appropriate selection. Block 140 checks for
`a new value of heart rate. Block 145 displays the heart rate
`at the upper right hand corner of the display. Block 150
`keeps track of the calibration and battery charge and allows
`Block 155 to update them. Finally, Block 160 checks for a
`request to send data through the serial port and Block 165
`transfers the data to it.
`
`25
`
`Hardware Operation-FIG. 2
`FIG. 2 refers to the operation of the electronic compo- 10
`nents. The electrocardiogram signal is sensed by either two
`or three electrodes 44 attached to the skin of the user or
`patient. Normally, two electrodes are sufficient to pick up the
`electrocardiogram signal. The use of the third electrode is
`recommended to reduce power line noise in some environ(cid:173)
`ments. In addition, this third electrode increases the range of
`electrode positions available (e.g., modified chest leads).
`The electrode cable 28 receives the electrocardiogram signal
`from the electrodes 44 and sends it to the input protection
`circuit 26. This input protection circuit provides high(cid:173)
`voltage protection (e.g., defibrillation shock). The electro(cid:173)
`cardiogram signal then continues to the instrumentation
`amplifier 30 that consists of a conventional configuration
`with three operational amplifiers. The gain at this stage is 8.
`Next is the signal conditioning stage 42 that consists of (1)
`a single pole low-pass filter with frequency cutoff at 20, 40,
`or 125 Hz; (2) a single pole high-pass filter with frequency
`cutoff at 0.05 or 0.5 Hz; (3) a variable gain of 65.5, 125, 250,
`or 400 for an overall gain of 500, 1000, 2000, or 4000
`respectively; and ( 4) an additional single pole high-pass
`filter with frequency cutoff at 3.5 Hz. This filter will be used
`only for brief periods for the purpose of controlling the
`sudden baseline deviations that sometimes occur during
`normal operation. The microcontroller 32 controls the cutoff
`frequencies of the filters and the gain using analog switches.
`The output of the signal conditioning stage 42 is connected
`to the analog-to-digital port and other control pins of the
`microcontroller 32.
`The microcontroller is also connected to the liquid crystal
`display 10, three switches 12, 14, 16, and to the circuitry
`needed by the microcontroller such as a crystal oscillator
`(not shown) and contrast control for the display (not shown).
`The microcontroller 32 has an internal analog-to-digital
`conversion capability, RAM and EEPROM memories, and a
`serial port for communication with other devices. Non(cid:173)
`volatile memory 58 with a capacity of 2 Kbytes, is con(cid:173)
`nected to the microcontroller 32 to allow for storage of user
`settings and electrocardiogram signal segments. The serial
`output of the microcontroller 32 is connected to the infrared
`port 50 that allows the device to communicate with outside
`devices while maintaining complete isolation for the user.
`The battery-based power supply 34 that provides power to
`all the circuits has a reset circuit to reset the microcontroller
`32, a voltage regulator (not shown), and an on/off switch 46. 55
`Software Operation-FIGS. 2, 7A, 7B, 8, 9A, 9B
`
`30
`
`Interrupt Routine-FIG. 8
`
`35
`
`The interrupt routine samples the electrocardiogram
`signal, performs additional filtering (50 or 60 Hz), runs the
`QRS detector routine, updates timers, and polls the user
`switches. Control flags and timers updated by the interrupt
`routine are used by the main routine to update the display.
`40 FIG. 8 shows a block diagram describing the interrupt
`routine. Block 200 gets a sample of electrocardiogram signal
`every 2 msec. The sample is filtered by a notch filter (Block
`210) at either 50 Hz or 60 Hz. The filtered electrocardiogram
`sample is stored in memory by Block 220. Block 230 is the
`45 QRS detector routine (described below). Block 230 detects
`the R waves in the electrocardiogram signal and calculates
`heart rate from them. Block 240 debounces and checks the
`user switches. Block 250 updates all the flags associated
`with the state of the switches. Finally, Block 260 updates the
`50 timers.
`
`QRS Detector Routine-FIGS. 9A, 9B
`
`The QRS detector finds the R-waves in the electrocardio(cid:173)
`gram signal and calculates the heart rate from them (Sun, Y.
`et. al., "Microcontroller-Based Real-Time QRS Detection,"
`Biomedical Instrumentation and Technology 1992;
`26:477-484). This QRS detector routine is activated through
`the interrupt routine and returns the processed information to
`the interrupt routine to be displayed. Referring to FIGS. 9A
`60 and 9B, Block 300 computes an activity function based on
`the first-order backward difference d[ n]. Ifs[ n] denotes the
`current ECG sample, then d[ n ]=s[ n ]-s[ n-1] denotes the
`first-order backward difference. The activity function is
`computed as follows: AF[ n ]=d[ n ]xd[ n-1 ]xd[ n-2] if d[ n ],
`65 d[n-1], and d[n-2] have the same sign, otherwise AF[n]=O.
`Block 310 computes the noise level of the signal. Block 310
`is designed to prevent the threshold to become too low.
`
`The microcontroller 32 has programming instructions
`(software) to coordinate all the functions of the device. The
`software includes the analog-to-digital conversion of the
`electrocardiogram signal, typically, with 8 bits of resolution
`at 500 samples per second. The code includes instructions to
`present the data acquired to the liquid crystal display, to
`detect the QRS component of the electrocardiogram signal,
`and to calculate the heart rate. In addition, the software
`allows the user to modify the operation of the device via the
`use of switches 12, 14, and 16.
`
`IPR2018-00294
`Apple Inc. EX1008 Page 15
`
`

`

`6,149,602
`
`7
`There is a refractory period (100 ms) after each detection
`to avoid multiple detections. Block 400 checks if the signal
`is within that period. If so, Block 500 sets a threshold at the
`maximum ofAF[n] during the refractory period (this refrac(cid:173)
`tory period includes the recently detected QRS). Block 510 5
`decrements the refractory period. Block 520 checks to see if
`the refractory period has expired. If so, Block 530 sets a
`QRS flag to false and resets the threshold decay period to
`100 ms. If Block 400 determines that the signal is not in the
`refractory period then Block 410 decrements the threshold 10
`decay period. When a fixed time period elapses (Block 420),
`the threshold is reduced by half (Block 425). The threshold,
`however, is not allowed to go below a minimum level, which
`is two times the noise level of the signal (Blocks 430 and
`435).
`Block 440 checks if the activity function is greater than
`the threshold, if so a new QRS wave has been recognized.
`Block 450 then sets the QRS flag to true and resets the
`refractory period to 100 ms. Finally, Block 460 computes the
`heart rate based on the last four QRS detected.
`
`15
`
`User Controls-FIG. 1
`
`8
`preferably on the chest of the user and attached to one
`end of the cable. The other end of the cable connects to
`the housing 18. Configurations with other cables that
`can handle more electrodes are also possible.
`Infrared Link-This infrared port 50 allows the device to
`have serial communication with other external devices
`with infrared serial ports. A special cable is provided
`(not shown) to connect to the serial port of devices
`without infrared capability. Isolation from the power
`line is maintained in all cases.
`
`Menu Selection-FIG. 1
`
`Three switches or pushbuttons are provided to select from
`a number of functions that enhance the operation of the
`device. The three switches 12, 14, 16 allow the user to scroll
`20 left, to scroll right, or to select from a menu of choices
`located on the bottom of the display 10. The four menu
`functions are "ECG," "HOLD," "HR," and "SETUP." These
`functions are shown as boxes on the lower part of the display
`10. Selecting any one of them displays a sub-menu, and each
`sub-menu in turn offers several selections that can be acti(cid:173)
`vated when pressing the center switch 14. The description of
`the menu structure is as follows:
`
`25
`
`The device includes four switches that allow the user to
`control the operation of the device. These four switches are
`shown in FIG. 1.
`On/Off-turns power on or off to the device.
`The following three switches allow the user to operate the
`menu buttons that appear at the bottom of the display
`("ECG", "HR", "HOLD", and "SETUP"):
`Left Switch-moves the focus to the menu button to the
`left of the currently selected (highlighted) menu button.
`Center Switch-activates the currently selected
`(highlighted) menu button.
`Right Switch-moves the focus to the menu button to the 35
`right of the currently selected (highlighted) menu but-
`ton.
`
`30 ECG Menu
`
`Submenu
`
`Selections
`
`Size
`Filter
`Speed
`Back
`
`5, 10, 20, 40
`monitoring, exercise, diagnostic
`12.5, 25, 50
`
`Display Indicators-FIG. 1
`All the indicators are shown on different regions of the 40
`display. An example of the display layout can be seen in
`FIG. 1.
`Heart Rate-Average heart rate is computed on the last 4
`RR intervals, and is updated only when the new value
`is different from the currently displayed value. The
`heart rate is shown as a numeric on the upper right hand
`corner of the display. The units are in beats per minute.
`QRS Plop-A small figure visually indicates that a QRS
`has been detected. This plop is updated every beat, and
`shown as a blinking heart to the left of the heart rate
`numenc.
`Hour-The hour in HH:MM format is updated every
`minute, and is shown at the lower right hand corner of
`the display.
`Date-The date in MM/DD format is updated every day,
`and is shown below the hour numeric.
`Low Battery-The small battery figure is displayed at
`lower right hand corner of the display when the battery
`reaches a critically low voltage.
`
`"Size" allows the user to increase or decrease the size of
`the electrocardiogram signal by the required amount (the
`units are in mm/m V). "Filter" allows the user to select three
`different filters