United States Patent 15
`Albertet al.
`
`US005735285A
`{11) Patent Number:
`[45] Date of Patent:
`
`5,735,285
`Apr. 7, 1998
`pr.
`/,
`
`7/1985 Reinhold, Jr. et al. wee 128/696
`4,531,527
`[54] METHOD AND HAND-HELD APPARATUS
`2/1986 Langer etal.
`..
`we 128/696
`4,567,883
`FOR DEMODULATING AND VIEWING
`2/1989 Fuetal. ..........
`364/413.03
`4,803,625
`FREQUENCY MODULATED BIOMEDICAL
`7/1990 Bergelson etal
`128/696
`4,938,229
`SIGNALS
`5,023,906—G/1991 Novas occcescsccssescsccsenecarsenuee 379/372
`.
`.
`.
`.
`5,191,891
`3/1993 Righter
`.........csscsessecreseteserees 128/710
`Inventors: ?aideer Tanderave T, Smith,
`5,321,618
`6/1994 Gessman
`364/413.06
`oth
`of Oklahoma
`City; Carl J. Rieger.
`5,333,616
`8/1994 Mills et al
`wn. 128/696
`Ponca City; Colin J. Cumming.
`5,336,245
`8/1994 Adams etal
`. 607/32
`Stillwater, all of Okla.; Leslie D. Hoy.
`5,339,824
`8/1994 Engira wees
`128/712
`Knoxville. Tenn.
`5,365,935
`11/1994 Righter et al.
`128/710
`5,433,736
`7/1995 Nilsson ......
`607/32 &
`5,466,246 11/1995 Silvian ......cccsssecssccsccsssneessssessees 607/32
`
`we 128/696
`5,503,158
`4/1996 Coppock etal.
`8/1996 Davis et al, ou.sesesessseeneeree 128/700
`5,544,661
`
`
`
`
`
`(75]
`
`[73] Assignee: Data Critical Corp., Oklahoma City,
`Okia.
`
`[21] Appl. No.: 658,236
`
`FOREIGN PATENT DOCUMENTS
`
`[22]
`Filed:
`Jun, 4, 1996
`E52] Ent, C18nceescscsccceneenennseesneeenenseees A61B 5/0432.
`[52] US. CU. ceeecsssesesereenete 128/696; 128/904; 128/710
`[58] Field of Searcha 00...ccecsesssenseseees 128/696, 710.
`128/711, 904; 364/413.03-413.06; 607/32.
`60
`
`[56}
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`S/L973 WiMAMS eeecsssscessessessesson 343/17.2 pc.
`3,731,311
`5/1975 DePedroet al.
`.
`3,882,277
`9/1975 Trott, Ir. et al. .
`3,909,599
`5/1977 Gilmore .
`4,027,146
`4,409,984 10/1983 Dick 20...secssssssscenessenseesseceneracens 128/696
`
`2181554
`4/1987 United Kingdom...............0 128/710
`Primary Examiner—Jefirey R. Jastrzab
`Attorney, Agent, or Firm—Dougherty & Hessin. P.C.
`[57]
`ABSTRACT
`.
`—
`Method and apparatus for transmission of biomedical wave-
`form data from a patient to an attending physician wherein
`the waveform data audio signal is frequency modulated for
`subsequent wireline or wireless transmission to a remote
`hand-held computer that functions to digitize. record and
`-—«demodulate the frequency modulated signal for display on
`the computer, for permanentprint-out, or for further retrans-
`mission.
`
`14 Claims, 5 Drawing Sheets
`
`12
`
`24 TELEPHONE
`
`SYSTEM
`
`1
`
`APPLE 1022
`
`1
`
`APPLE 1022
`
`

`

`U.S. Patent
`
`Apr. 7, 1998
`
`Sheet 1 of 5
`
`5,735,285
`
`TELEPHONE
`
`SYSTEM
`
`4|M
`
`ICROPHONE.
`
`34
`
`—————
`
`oo LL[
`36
`|
`!
`DIGITAL
`ANALOG TO
`BANDPASS
`DIGITAL
`
`CONVERTER|| FILTER |
`
`[
`48
`40
`|
`DIGITAL
`STORAGE
`|
`FILES
`POLYPHASE
`||
`_ oT"
`DEMODULATOR
`|}
`50 |
`DIGITAL
`ao-—t— |
`|
`
`
`TO ANALOG “sear|CONVERTER | sora
`
`ORA ||DISPLAY
`
`s L-_yJ— — 4
`8
`7
`44
`
`46
`
`ae
`
`54
`
`5
`
`6
`
`RELAY
`
`ADDITIONAL
`DIAGMOSTIC
`LOCATION
`
`oi
`
`2
`
`

`

`U.S. Patent
`
`Apr. 7, 1998
`
`Sheet 2 of 5
`
`5,735,285
`
`
` TELEPHONE
`
`SYSTEM
`
`iro.
`
`16R
`
`100
`
`(A)
`
`READ 80 INPUT
`SAMPLES
`
`110
`
`
`
`VARIABLES ENCOUNTEREDCew)
`
`INITIALIZE
`
`EOF
`
`Y
`
`104
`
`106
`
`108
`
`ANDOUTPUT
`FILES
`
`READ THE *.WVE
`FILE HEADER
`INFORMATION
`
`STORE THE
`
`NUMBER OF
`SAMPLES.
`IN
`THE FILE
`
`.
`ALAW DECODE
`SAMPLES
`
`BANDPASSFILTER
`ceookhz O=2
`
`116
`
`P18
`
`120
`
`a (B)
`(POSITIVE)
`
`122
`
`Sori
`
`3
`
`

`

`U.S. Patent
`
`Apr. 7, 1998
`
`Sheet 3 of 5
`
`5,735,285
`
`
`BANDPASS
`FILTER
`
`(OPTIONAL)
`
`MICROPHONE
`
`60
`
`
`
`38
`
`
`ANALOG TO
`ANALOG
`DIGITAL
`FM
`
`DEMODULATOR
`CONVERTER
`
`
`
` DIGITAL
`
`BANDPASS
`FILTER
`
`
`
`64
`66
`
`
`BANDPASS
`FILTER
`
`
`
`
` CYCLE
`
`ACCUMULATOR
`
`ss
`—S-St
`
`4
`
`

`

`U.S. Patent
`
`Apr. 7, 1998
`
`Sheet 4 of 5
`
`5,735,285
`
`0
`
`40
`
`«WINDOW 1
`
`80
`
`)
`
`120
`
`160
`
`200
`
`\
`
`WINDOW 2
`
`)
`
`\
`
`WINDOW 1
`
`J
`
`DOULODOOOIIRZ
`
`\
`
`WINDOW 2
`
`J
`
`Beoddeeere
`
`5
`
`

`

`USS. Patent
`
`Apr. 7, 1998
`
`Sheet 5 of 5
`
`5,735,285
`
`POINT TO
`FIRST SAMPLE
`
`143
`
`124-176
`
`128
`
`is
`SAMPLE
`;
`Osity
`Y
`
`432
`
`134
`
`Y
`
`
`
`
`
`IS
`
`
`SAMPLE THE
`POINT TO THE
`
`NEXT SAMPLE
`41st SAMPLE
`
`
`
`
`146
`
`
`LOOK UP CYCLE
`
`RESIDUE ESTIMATE
`
`
`(ARCTAN TABLE,
`
`
`SAMPLE 39 & 40)
`
`ADD ESTIMATE TO
`CYCLECOUNT 1
`
`
`
`ADD 256 TO
`CYCLECOUNT 1
`
`AND
`
`CYCLECOUNT 2
`
`OUTPUT TO
`FILE
`CYCLECOUNT 1
`
`
`
`36
`
`ASSIGN LASTSIGN
`(SIGN OF THE
`SAMPLE)
`
`RESET
`CYCLECOUNT 1
`
`(256-ESTIMATE)
`i ——
`170
`
`134
`
`(Cc)
`
`152
`
`is
`ST
`OSITIV
`Y
`
`N
`
`"8
`
`160
`
`
`
`Y
`ADD 256 TO
`CYCLECOUNT 1,
`
`CYCLECOUNT 2
`
`
`
`162
`ASSIGN LASTSIGN
`(SIGN OF THE
`SAMPLE)
`
`164
`
`POINT TO THE
`NEXT SAMPLE
`
`es
`168
`
`N
`
`ac
`AMPLE THE 81s
`SAMPLE
`
`Y
`
`i ———
`
`144
`
`148
`
`150
`
`152
`
`172
`
`
`LOOK UP CYCLE
`RESIDUE ESTIMATE
`
`
`(ARCTAN TABLE,
`
`
`SAMPLE 79 & 80)
`174
`
`ADD ESTIMATE TO
`CYCLECOUNT 2
`
`OUTPUT TO FILE
`CYCLECOUNT 2
`
`174
`
`178
`
`RESET
`CYCLECOUNT 2
`(256—ESTIMATE)
`
`6
`
`

`

`5,735.285
`
`1
`METHOD AND HAND-HELD APPARATUS
`FOR DEMODULATING AND VIEWING
`FREQUENCY MODULATED BIOMEDICAL
`SIGNALS
`
`A Microfiche Appendix is included in the application
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention.
`The invention relates generally to improved method and
`apparatus for monitoring a patient’s biomedical waveform
`data and. more particularly, but not by way of limitation. it
`relates to an improved method and apparatus for monitoring
`a patient’s electrocardiogram (ECG)data using a hand-held
`computer in association with a wireline or wireless tele-
`phone system.
`2. Description of the Prior Art
`The prior art includes numerous systems wherein ECG
`data or the like is transmitted from a patient to a particular
`doctor’s office or health service center. U.S. Pat. No. 4.938,
`229 discloses an earlier form of monitoring system which
`includes apparatus for demodulating a constant amplitude
`audio FM ECGsignal. The analog FM signal is processed
`through a zero crossing counter which generates a digital
`pulse for every crossing. The time intervals between pulses
`are then averaged to produce a digital ECG signal at a
`predetermined sample rate. This procedure differs from the
`present inventionasit does not digitize the audio FM signal,
`nor doesit utilize such as a polyphase demodulator to derive
`the ECG data in digital form. U.S. Pat. No. 4,531,527
`discloses another system for transtelephonic ECG monitor-
`ing; however, this system requires special hardware consid-
`erations and differs in may other aspects from Applicants’
`method and apparatus.
`U.S. Pat. No. 4.409.984 discloses a method for square
`pulse frequency modulation and demodulation of ECG data
`in a multiple patient monitoring system. The system does not
`employ polyphase demodulation since it processes a con-
`stant amplitude FM signal to detect zero crossings, and
`neither doesit provide portable storage and display of ECG
`data in the manner of the present invention. The similar
`digital FM demodulator is taught in the U.S. Pat. Nos.
`4,027,146 and 3,909,599, but there is no teaching of the
`digitization of an FM data signal nor of possible retrans-
`mitting of the FM signal. In addition,
`these patents all
`require hardware of specialized design for carrying out
`specific circuit functions.
`The U.S. Pat. Nos. 5,365,935; 5,191,891; and 5,333,616
`all relate to an ECG monitoring system that utilizes wrist-
`worn transtelephonic ECG recorders and transmitters. The
`disclosure does not deal with any form of signal demodu-
`lation and display or any storage and retransmission capa-
`bilities. The present invention would be compatible for use
`to receive, display, store and/or retransmit biomedical sig-
`nals derived by the teachings of these patents.
`ECGdata is usually transmitted directly from the patient
`to the analyzing location and one such system, available
`from Instromedix, Inc. of Hillsboro. Oreg.. utilizes a Heart
`Card to provide a recording of the ECG signal from thirty
`seconds upward to five minutes. This system provides for
`transmission via a wired or wireless telephone system of
`such recorded or realtime ECG data in the form of a
`frequency modulated audio signal. The transmitted FM
`audio signal is then demodulated at the doctor’s office or
`health service center for viewing of the actual ECG data
`whereupon the patient’s personal doctor is alerted if a
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`2
`problem is seen in the data. Further, the actual ECG data
`waveform may be sent via facsimile to the attending doctor.
`SUMMARYOF THE INVENTION
`
`The present invention relates to an improved communi-
`cation system for conveying ECG data or other biomedical
`waveform data more directly between the patient and an
`attending doctor’s location. The patient employs a Heart
`Card-type of device that converts the patient’s ECG signal
`into a frequency modulated audio signal that may then be
`analyzed by audio inputting via a telephone system to a
`selected hand-held computer device that functions to
`digitize. record and demodulate the frequency modulated
`signal for presentation and viewing on the hand-held com-
`puter display screen. Also, the operator has the option of
`printing out the demodulated biomedical signal for further
`viewing separate from the hand-held computer. Thereisstill
`further an option of retransmitting the stored ECG audio
`signal via telephone, either wireline or wireless, to a desig-
`nated doctor’s office; or. if no one answers. the call may be
`forwarded to another nurse or doctor as designated. At any
`ofthe first or forwarded receiverstations, the attendant may
`also have a programmed hand-held computer that can
`receive the audio FM biomedical signal for digitization.
`recording and demodulation for viewing. The hand-held
`computer is one with integrated microphone, audio analogto
`digital converter, digital to analog converter. speaker, and
`central processing unit with memory for performing various
`computational, data storage and signal processing tasks.
`Therefore,
`it is an object of the present invention to
`provide a highly accurate and portable biomedical signal
`monitor for use with a telephone system, either wireline or
`wireless.
`It is also an object of the present invention to provide a
`highly accurate andreliable patient monitoring system that
`allows the doctor to interface directly over a telephone
`system with the patient at anytime or anywhere.
`It is yet further an object of the present invention to
`provide a patient monitor system that may be quickly and
`reliably deployed in monitoring operation.
`It is still further an object of the present invention to
`provide a reliable and accurate patient ECG monitoring
`system with first hand communication between doctor (or
`other healthcare provider) and patient.
`Finally, it is an object of the invention to provide a
`hand-held computer with proprietary software that combines
`with a telephone system to provide remote monitoring of a
`patient’s electrocardiogram (ECG).
`Other objects and advantages of the invention will be
`evident from the following detailed description when read in
`conjunction with the accompanying drawings that illustrate
`the invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is an idealized block diagram of an ECG moni-
`toring system;
`FIG.2 is a functional block diagram of a preferred form
`of signal processing circuitry as effected by a hand-held
`computer;
`FIG.3 is an idealized block diagram of a monitoring relay
`link for further transmission of ECG data;
`FIG.4 is a functional block diagram of an alternative form
`of patient monitoring circuitry as effected by a programmed
`hand-held computer;
`PIG. 5 is a diagram of a programmed signal process as
`utilized in the preferred form of circuitry;
`
`7
`
`7
`
`

`

`5,735,285
`
`3
`FIG. 6 is a diagram illustrating cycle accumulation
`between filtered data and decimated data output;
`FIGS. 7, 8 and 9 are a flow diagram for the demodulation
`procedure carried out by the Rhythm-Stat SX software; and
`FIG. 10 is a top plan view of a Psion 3a hand-held
`computer.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`Referring to FIG. 1, a patient monitoring system 10
`consists of a Heart Card 12 disposed on the patient and
`capable of detecting and recording the electrocardiogram
`signal (ECG)for a predetermined time and then actuable to
`transmit the ECG as a frequency modulated audio band
`signal 14. The Heart Card 12 is a commercially available
`device that functions to sense the ECG data for a predeter-
`mined time period and, after the period. the Heart Card 12
`can be actuated to transmit the audio frequency modulated
`ECG data. Such Heart Card sensor/transmitters may be
`obtained from such as Instromedix, Inc. of Hillsboro, Oreg.
`Other devices that perform the same or similar functions
`(i.e.. recording the ECG and transmitting over a phone
`system as a frequency modulated audio signal) are available
`from Instromedix, Inc. and other vendors.
`The frequency modulated audio signal 14 may then be
`transmitted via telephone, either wireline or wireless; or, the
`frequency modulated audio signal 14 may be played directly
`into the audio microphone of a palmtop computer 16 which
`includes resident software that processes the biomedical data
`contained in the frequency modulated audio signal and
`displays the data on the computer screen 18. In most cases,
`the patient and Heart Card 12 will be remote from the
`palmtop computer 16 and the attending physician or diag-
`nostician. In this situation the Heart Card 12 need only
`transmit the frequency modulated audio into the receiver 20
`of telephone 22 which is connected via a suitable telephone
`system 24, either wireline or wireless, to a telephone 26 at
`the attending physician’s office whereupon the telephone
`transmitter 28 can direct frequency modulated audio data 14
`into the microphone of the palmtop computer 16 to complete
`the information relay.
`A preferred embodimentof the invention uses a Psion 3a
`palmtop personal computer with proprietary software as will
`be further described. The hand-held computer 16 must have
`an integrated microphoneor direct audio electrical jack that
`can interface to a wireline or wireless phone. A laptop
`computer could be used for the present invention; however,
`it does not have the portability feature that makes the
`hand-held version preferred.
`The preferred form of the invention is illustrated in the
`functional block diagram of FIG. 2 which illustrates the
`functional componentsof the programmed Psion 3a palmtop
`computer 16. The frequency modulated audio biomedical
`data may be input directly to microphone 30 or, in some
`cases, it may be received directly through a connector jack
`32 to inputlead 34 to analog/digital converter 36. The output
`from analog to digital converter 36 is then applied to a
`digital band-passfilter 38, e.g., over the band of 0.05 Hz to
`40 Hz. and thento a digital polyphase demodulator 40. The
`dash-line 41 outlines the central processing unit and memory
`components of the palmtop computer 16 (FIG. 1). The
`demodulator 40 employs two simultaneous filters which
`have been optimized for integer operation using a
`micropower microprocessor. The output from demodulator
`40 may then be applied directly to display 18, or the filtered
`digital signal can be applied directly to a storage file 42 for
`selected output via printer 44.
`
`4
`Alternatively, the digital biomedical FM data signal out-
`put from analog to digital converter 36 may be applied via
`lead 46to a storage file 48. Selected data from storage file
`48 maythen be played back into digital to analog converter
`50 and the analog signal can then be applied to a loud
`speaker 52 and/or further telephone or facsimile relay 54 to
`a remote diagnostic location for further demodulation.
`review and opinion. As shown in FIG. 3,
`the original
`receiving phone 26 and handset 28 maybe used torelay the
`data via telephone system link 53 to yet another phone 26R
`and handset 28R as located at another remote location. Such
`further transfer may be necessitated by a need for second
`opinion or additional comparison data. The hand-held com-
`puter 16 may be operated to emit the audible ECG data from
`handset 18 for transmission via telephone interconnect 53 to
`the remote phone 26R whereupon handset 28R provides
`audible input to another hand-held computer 16R for pro-
`cessing and display of the ECG data.
`FIG. 4 illustrates an alternative design of the invention
`utilizing a palmtop computerof the type having a PCMCIA
`interface slot for signal processing and display. A received
`frequency modulated audio signal is fed either via micro-
`phone 30 or connector 32 to input lead 34 to the analog FM
`demodulator 58. The FM demodulator 58 may be such as a
`IC phase locked loop, Exar type 215. The analog FM
`demodulator 58 then applies output to an analog to digital
`converter 60 which provides digital output via the palmtop
`PCMCIA interface to the palmtop’s CPU for digital filtering
`(40), storage and display. Optionally, a band-pass filter 62
`may be interconnected between the demodulator 58 and the
`analog to digital converter 60. The output from digital filter
`38, having a pass-band of 0.05 Hz to 40 Hz., may then be
`applied to output display 18, or, it may be placed in storage
`file 42 for subsequent recall to printer 44. The demodulator
`58, converter 60 and bandpass filters 62 and 40 are all
`contained in the PCMCIA card.
`
`Referring to the preferred embodiment of FIG.2, it is an
`objective of the Rhythm-Stat program to demodulate a
`frequency modulated audio signal and to decimate the
`output for storage and plotting purposes. The Psion 3a
`computer 16 records sound files at an 8.000 samples per
`second rate and uses an A-Law analog to digital transfor-
`mation. Therefore. the program used to demodulate a fre-
`quency modulated ECG or biomedical signal must perform
`three functions. As shown in FIG.5, these functions are (1)
`an A-Law decoder 64, (2) a band-pass filter 66, and (3) a
`frequency estimator 68 which includes a residue estimator
`70 and a cycle accumulator 69. The A-Law decoder 64
`functions as an expander which reverses the action of the
`A-Law compressor in the Psion. The A-Law encoding is a
`standard approximation to the logarithmic compression as
`established by CCITT, the European standards body. The
`output of the A-Law compander is defined by
`
`F(xasgn(x)*ALA(1+n(A))
`
`OStI<V/A
`
`F(x)sgn(x)*(14In(Abel)¥(14in(A))
`
`1ASb1S1
`
`ay
`
`(2)
`
`10
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`355
`
`65
`
`where x is the analog input. F(x) is the A-Law compander
`output. sgn(x) is the sign (+) of x. and Ais the compression
`parameter. Since the Psion 3a computer 16 records the sound
`file in A~-Law encoded format(12-bit data stored in 8 bits, all
`at 8000 samples per second),
`these values need to be
`decoded in order to band-pass filter and demodulate the
`
`8
`
`8
`
`

`

`5,735,285
`
`5
`signal, The decoding is accomplished by using a look-up
`table. The range of A-Law encoded values is —128 to 127,
`therefore. an array of length 256 is initialized to contain the
`A-Law decoded values. The array is indexed from zero to
`255 as the decoded value contained at indexed zero corre-
`sponds to the A-Law value of -128, and the decoded value
`contained at index 255 corresponds to the A-Law value of
`127. Therefore, to decode any A-Law value. 128 is added to
`the A-Law value and the result is used to index into the array.
`The digital band-pass filter 66 is utilized to remove
`unwanted signal introduced when recording with the Psion
`3a. The equation used to realize the band-passfilter is
`
`10
`
`aon)byX(n)tbx(n)rbax(n-2)ta,y(n—l)tagy(n-2)
`
`(3)
`
`15
`
`where x(n)is the input data, y(n) is the outputdata, and a,,
`b, are constant coefficients. For data that is sampled at 8000
`Hz, to obtain a band-pass filter with a Q=2 and a center
`frequency of 2000 Hz, the coefficients are set to
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`b.=-1
`This realizes a band-pass filter with a transfer function
`
`H(z(1-27(140.5277)
`
`4
`
`This portion of the demodulation procedure is implemented
`directly after the A-Law decoder 64 and before the cycle
`counting procedure.
`The frequency estimator 68 functions by windowing the
`input data and counting the number of complete cycles
`contained within the window. The phase of the incomplete
`cycle located at the end of each window is estimated by
`using the arctangent function. Therefore.
`the frequency
`estimator 68 contains two sections which are (1) the cycle
`accumulator and (2) a residue estimator. See FIG. 6. The
`cycle accumulator consists of two overlapping windows and
`FIG. 6 showsthe relationship between the two windows.
`Thefiltered data appears on line 72 with 40 unit graduations
`while the decimated output data appears along line 74. The
`size of each window determines the amount of decimation in
`the demodulation procedure. Choosing a window size of 80
`decimatesthe data from 80 input points to 1 (80:1). however.
`with two overlapping windowsthe final output is decimated
`by 40:1. Thus, with an original sampling of 8000 samples
`per second, the output is resampled to 200 samples per
`second after decimation. For a frequency estimate, each
`window counts the number of complete cycles of 80 band-
`pass filtered data points. For each complete cycle, 256
`(corresponding to 2m radians) is added to the window
`counters. After determining the number of complete cycles
`contained in 80 data points, a window calls the residue
`estimator passing the 79th and 80th data points to determine
`the amount of the incomplete cycle on the end of the
`window.
`Using the last two data points of the cycle accumulator
`window,the residue estimator 70 determines the amount of
`an incomplete cycle by using a look-up table technique. The
`look-up table contains arctangent values for every possible
`point in the first quadrant of a sine wave. The values are
`scaled to range from zero to 64 (corresponding to 0-1/2
`radians). Using the sign of the two points passed from the
`cycle counter, the residue estimator 70 determines in which
`quadrantthe points are located. These points are then scaled
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`6
`so that both are less than 64 in order to index into the
`arctangent look-up table. The quadrant determination with
`the arctangent value, determines the output of the residue
`estimator as follows:
`1st quadrant: Residue Estimate=arctangent value
`2nd quadrant: Residue Estimate=128 —arctangent value
`3rd quadrant: Residue Estimate=128 +arctangent value
`4th quadrant: Residue Estimate=256 —arctangent value
`The residue estimate is added to the window calling the
`residue estimator 70 and thus is used as an outputpoint. The
`window counter is then reset to 256 minus residue estimate
`to include an estimate of the incomplete cycle located at the
`beginning of the next 80 filtered data points.
`FIGS. 7, 8 and 9 are a flow diagram of the demodulation
`procedurethat is carried out under the system program.i.e.
`the Rhythm-Stat XL software, as will be further described
`below. In FIG. 7. the process begins at START 100 where-
`upon variablesare initialized in flow stage 102 and the input
`and outputfiles are readied at stage 104. The flow stage 106
`then reads the *.WVE file header information and the
`number of samples in the file is stored at flow stage 108.
`Flow stage 108 then proceeds to stage 110 which sees
`reading of eighty input samples after which decision stage
`112 tests to see whether or not end of file (EOF) has been
`encountered. If end of file does appear, then the affirmative
`output proceeds to END stage 114 and completion of the
`program operation. If end of file is not yet reached, the
`negative output passes flow to stage 116 which functions to
`A-Law decode the samples. The A-Law decoding expands
`the A-Law encoded values to the original value.
`Data handling proceeds to flow stage 118 which effects
`bandpassfiltering and subsequent flow stage 120 functions
`to assign samples in accordance with polarity of the last
`sign. Continuing on to FIG. 8. the line 122 connects from
`Terminal B to flow stage 124 which pointsto first sample
`with data flow on line 126 to a series of decision stages. A
`first decision stage 128 tests for whether or not the sample
`is positive with a negative response by-passing on line 130,
`and an affirmative response proceeding to the subsequent
`decision stage 132 which queries for last sign negative. A
`negative response directs flow to by-pass line 130 and an
`affirmative response continues process to stage 134 which
`adds 256 to cyclecount 1 and cyclecount2. A flow stage 136
`then assigns a lastsign the sign (+) of the sample being
`processed.
`Flow line 138 then proceeds to stage 140 which functions
`to point to the next sample prior to decision stage 142 which
`queries whether the sample is the forty-first sample in the
`sequence. If negative, and the sample is other than the
`forty-first sample. flow recycles via line 143 to the decision
`stage 128 which tests whether or not the sample is positive;
`but, if stage 142 is affirmative. flow proceeds to stage 144
`wherein the look-up cycle residue is estimated. That is, a
`value is obtained from the arctangent table for samples
`thirty-nine and forty as flow proceeds to stage 146 which
`adds the estimate to cyclecount 1. A next flow stage 148 sees
`outputto file of cyclecount 1 with flow stage 150 resetting
`the cyclecount 1 before proceeding on line 152 for connec-
`tion to the C terminal at FIG. 9.
`The line 152 leads to a series of decision stages wherein
`stage 154tests for a positive sample and, if negative. cycles
`aheadvia line 156, and,if affirmative, query is made of the
`next decision stage 158 as to whetheror notthe last sign was
`negative. If not. cycle ahead via lead 156 is made or. if
`affirmative, flow proceeds to stage 160 which adds 256 to
`each of cyclecount 1 and cyclecount 2.
`Flow proceeds from stage 160 as well as by-pass line 156
`to a stage 162 which functions to assign the lastsign or
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`5,735,285
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`7
`previous sample sign. Thereafter. flow stage 164 points to
`the next sample as indication proceeds via line 166 to a
`decision stage 168 which queries whether the sample is the
`eighty-first sample in the succession. If not, flow proceeds
`via line 170 to recycle through stages 154 and 158 and
`succeeding stages; however, if the decision is affirmative
`(the eighty-first sample) then stage 172 establishes the
`look-up cycle residue estimate, i.e., samples 79 and 80 from
`the arctangent look-up table. The estimate is added to the
`cyclecount 2 in flow stage 174 and outputtofile in flow stage
`176 priorto the reset of cyclecount 2 in stage 178. Flow then
`proceeds through terminal A back to FIG. 7 for recycle
`through flow stage 110 which reads the next eighty input
`samples. Eventually, when end offile is encountered as at
`flow stage 112. the affirmative output proceeds to END 114
`to terminate the process.
`The program for controlling the Psion 3a hand-held
`computer 16 is termed the Rhythm-Stat XL software andit
`functions to acquire frequency modulated biomedical data,
`e.g.. ECG data, as generated by an Instromedix™ recording
`device knownas the Heart Card 12 or other similar medical
`data recording device. The Psion 3a computer 16 is pro-
`grammed with the Rhythm-Stat XL program that functions
`with the Psion floating point emulator. Data files with a
`*WVE extension must be first placed in the ECG data
`directory, and these are Psion sound files that will be
`decoded, demodulated, and displayed by the Rhythm-Stat
`XL program as an ECG rhythm strip.
`Onstart up (see FIG. 10), the program displays a title
`screen, and pressing the ESCAPE key 76 continues opera-
`tion with an empty graphics grid as the program title will
`appear on display screen 18. The MENU key 78 may then
`be depressed to access the program menusandselected hot
`keys will be shown to the right of the listed menu items. In
`order to use an item, it is necessary to hold down the Psion
`special key 80 while pressing the desired character key. As
`shown in FIG. 19, the white keys are the standard Qwerty
`keys while the black keys are various function and control
`keys. The ECG data scaling. keyboard display controls, and
`data acquisition and relay are summarized below.
`Theinitial display represents a 12.5 mm/secondscale that
`is divided into 200 ms graduations. Up to three 9.6 second
`periods of ECGtotalling 28.8 seconds of ECG rhythm, may
`be displayed. Expanded scales of 25 and 50 mm per second
`are available.
`The y scale is calibrated to show millivolts of signal
`value. During demodulation, and after the processing is
`completed, and the data replotted, a square calibration pulse
`will appear on theleft of the first segment of ECG data to
`provide signal calibration. An additional calibration pulse
`may be found at the end of a data set and these calibration
`pulses are nominally 1 millivolt on the y axis. A control key
`selects display scales of 25 or SO mm per second and
`selected arrow keys 86 may be used to select ECG epochs
`for display. When the ECG is expanded on the x axis, the y
`scale is 0.5 millivolts per graduation, and left and right arrow
`keys 96 and 98 will scroll the expanded display by one
`epoch at
`the selected scale. The user may increase or
`decrease the waveform amplitude by a factor of two with
`selected gain controls at any scale. The waveform may be
`shifted up or down in 0.5 my increments with up and down
`arrow keys of key group 86 for expanded displays. and also
`with the shifted up and down arrow keys in the initial 12.5
`mm per second display.
`The Rhythm-Stat XL program records. decodes and dis-
`plays acoustic frequency modulated ECG data that is gen-
`erated by such as the Instromedix Heart Card or other heart
`
`8
`is
`watch device, or by another Psion 3a computer that
`equipped with Rhythm-Stat XL program. as shown in FIG.
`3. Recording of the acoustic data may be direct. or it may be
`done with ordinary telephones across a wire line or wireless
`phone system.
`A more detailed operation description of menu options,
`keyboard controls, and ECG recording and relay procedures
`for this program follows. A first option in the FILES menu
`is the “open ECG file” which functions to display a list of
`files in the reversef/ECG directory. Left and right arrow keys
`96 and 98atthefiles display will present the file names. The
`only valid file types are *.RXL, *.RST and *.WVEfiles, and
`if other files are in the ECG directory. they will be shown.
`The program hasno provision for user interruption of.WVE
`input file processing, which takes about 30 seconds, or of
`ECGdata recording or playback, which takes 35 seconds.If
`necessary. a user may terminate the application duringfile
`processing or recording by holding down the Psion control
`key 80 while depressing the ESCAPE key 76.
`The Rhythm-Stat XL program is intended to record and
`display frequency modulated acoustic ECG data. and taking
`the record option will produce a file name selection dia-
`logue. When the desired file name is entered, a screen will
`tell the user that Rhythm-Stat XL program is ready to record
`and will begin when the “ENTER”key 82 is depressed.
`At this point, the user can place the output speaker on the
`Heart Card 12 as close to the Psion microphone opening
`(square opening at bottom right edge ofthe case) as possible.
`If recording over the telephone. place the Heart Card 12
`(FIG. 1) on the sender’s handset microphone 20 with the
`receiver’s handset speaker 28 as close to the Psion micro-
`phone opening as possible. The user can then initiate the
`playback and recording as close to simultaneously as pos-
`sible. The Heart Card 12 has a nominal 30 second playback
`period while the Psion 3a records 35 seconds of sound. The
`difference will accommodate a few seconds of variance in
`user synchronization of playback and recording.
`Note that there is no progress indicated for the recording
`and the program, and when Rhythm-Stat XL program com-
`pletes its recording, an annunciator chirps, and a third screen
`appears to tell the user that the recording is complete. The
`new WVE file will then be found amongthe file names
`offered in the files plus open menu option for processing and
`display.
`Another files menu item, playback ECG, appears in the
`Rhythm-Stat XL program. Thus, the program may be used
`to relay the FM ECGdata to another Psion equipped with the
`Rhythm-Stat XL program, by playing back the *.WVE ECG
`data file. Taking the playback option will producea file name
`selection dialogue. Once the file nameis selected, a second
`screen will tell the user that Rhythm-Stat XL is ready to play
`back the ECGdata file, and will begin when the ENTER key
`82 is depressed. The receiving Psion must be prepared for
`recording with the output speaker on the sending Psion as
`close to the microphone opening of the receiving Psion asis
`conveniently possible. If relaying the data over a phone
`system, the sending Psion speaker should be placed closely
`over the handset microphone with the receiving handset
`speaker as close to the related Psion opening as possible.
`Once again. the playback and recordingis initiated as close
`to simultaneously as possible and a high frequency warble of
`the frequency modulated ECG data will be audible and
`ceasing upon completion of playback. An annunciator chirp
`tells the user when the transfer has been accomplished.
`The remaining fi