Note: Descriptions are shown in the official language in which they were submitted.
~47~
` BACKGROUND OF THE INV~NTION
.
1 Field of the Inventlon-
The present invention relates generally to the field
of medical electronics. More specifically, the present invention
relates to means for monitoring and displaying vital signs
including EKG of a patient in a line-over--line compressed-data
manner which facilitates analysis.
2 Descri tion of Prior Art:
Over the years, various medical-electronic systems
have been developed which aid physicians in diagnosing and
providing therapy to patients. Particular?y, in the area of
cardiology and heart disease, there have been significant
advances. For example, heart pacers and EKG monitoring equip-
ment are but two of the types of equipment that have proved to
be valuable to physician and patient alike. These devices are
now tending to become somewhat famil~ar to laymen as well.
As is well known in the medical field, EKG strips are
taken by a physician by attaching Leads or conductors to the
body of a patient (generally three leads). Electrical signal
activity generated by the patient's heart is sensed by these
conductors or sensors. These electrical signals are extended
to EKG amplifiers and eventua:Lly to galvanometer pens for
scribing on the surface of a paper. The paper is generally
spool-wound chart paper and advanced in a continuous manner,
the direction of
~.
mb/~l 2 -
47~
advance of paper belng the direction of a time axis. Deflec-
tions of the galvanometer pen are generally perpendicular or
transverse to direction of motion of the paperO The resultant
trace, if the EKG is taken for any appreciable length of time,
is very long Anyone with experience in this field knows
that the accumulated chart paper is unwieldy and cumbersome.
It is thus difficult to accurately compare a patient's heart
activity over periods of an hour or more when the EKG is left
running continuously. Simply, too much paper exists for
facile manual control and analysis. This is a severe problem
of the prior art.
The present invention is a solution to the prior art
problem of recording and displaying large quantities of vital
sign data and particularly the EKG of a patient. It provides
an automatic line-over-line compression of data in a compact
and easily usable form and thus facilitates analysis.
mb/~- ~ 3 ~
47~S
The present invention relates to a system for dis~
playing vital signs of a patient, comprising: means for sensing
the vital signs and for providing analogous electrical signals,
means for amplifying the electrical signals, a chassis, a cylinder
having axially directed slit means in the surface of the cylinder
and extending the entire length of the cylinder for receiving two
substantially parallel edges of looped paper fitted to and support-
- ed by the surface and for clamping the edges to create a smooth
overlapping of the paper around the cylinder, means supported by
the chassis for rotating the cylinder thereby advancing and re~
cycling the paper, galvanometer pen means for scribing of the
paper in scribing directions transverse to the direction of motion
of the paper, means connected to the chassis for supporting the
pen means and for translatlonally moving the pen means in one of
the scrlbing directions from an initial position towards a final
position, and means for extending the signals to the galvanometer
pen means.
SUMMARY OF TH~ INVENTION
Thus, the chart paper direction is one time axis, and
~he direction of motion of the galvanometer pen is a second quan-
ti~ed time axis. Continuous transverse motion of the galvanometer
pen permits scribing a helix on the surface of the cylinder's chart
paper. Deflections due to the EKG signal are in directions also
~ransverse to direction of chart paper motion. The display system
includes EKG sensing and amplifying means, a rotatably mounted
cylinder, closed loop chart paper fitted to the cylinder, and a
transversely movable galvanometer pen assembly for scribing on the
paper in the manner described above. Another feature of the pres-
ent invention includes circuitry for providing a ditherin8 mark a-t
:, .
~t`JJj" - 4
s
selected portions of the recorded data either upon manual command
or automatically to indicate the average rate of heartbeat for a
given portion of EKG data.
An advantage of the present invention is that it
compresses vital sign data, from a long paper trace readaut into
a single sheet line-over-line vital sign "picture" thereby facil-
itating analysis. It is thus advantageous to patient and physician
alike.
It is thus an ob;ect of the present invention to pro
vide an improved system for displaying vital signs of a patient.
It is another object of the present invention to
provide an improved EKG monitor and display device.
It is a ~urther object of the present inventlon to
provlde an improved EKG display system that has means for indicat-
ing average heartbea~ rate for a selectable period of time and
has means for marking occurrences of other events on a chart paper
trace.
Other objects and advantages of the present invention
will become apparent to one having reasonable skill in the art
after referring to the detailed description of the appended
drawings in whlch:
.~
r~
1~47~15
BRIEF DESCRIPTION OF T~E DRAWINGS
Fig. 1 depicts a block diagram of an illustrative
embodiment of the present invention;
Fig. 2 depicts certain detail of the block diagram
of Fig. l;
Fig. 3 depicts a perspective view of certain
mechanical detail of the illustrative embodiment of the
present invention;
Fig. 4 depicts another perspective view of other
certain mechanical aspects of the illustrative embcdiment of
the present invention; and
Fig. 5 depicts the resultant chart paper compressed
data display generated by the present invention.
mb/~ 6 -
1~7~15
DESCRIPTION OF T~IE PREFERRED EMBODIMENTS
In Fig. 1, patient 101 i6 connected by ~KG leads
102 to EKG (ECG) amplifier electronics 103. ~lerein, a
conductor or lead is intended to imply conductors or leads
if approprlate.) Outpu~ from amplifier electronics 103 is
extended on conductor 104 to selector switch 105. Likewise,
output from ECG amplifier electronics 103 is extended on
conductor 115 to heart rate module 117. Output from heart
rate module 117 is extended to selector switch 105 on conductor
137. Output from selector switch 105 is provided on conductor
106 to galvano~eter drive electronics 107. Output from
electronics 107 is extended on conductor 108 to galvanometer
pen and carriage assembly 109. Scribing output from carriage
assembly 109 i9 provided to chart paper on drum 111 via input
(pen) 110. This is the basic sensing, amplifying, monitoring,
and recording (and/or displaying) functional chain.
Synchronous motor 129 provides rotational mechanical
output 128 to gear train 125 which, in turn, provides rotational
outputs 126 and 127 to assembly 109 and drum 111, respectively.
Synchronous motor 129 is supplied by AC line power 131 through
speed control 150 on conductor 130. AC line power 131 likewise
provides power inputs to power supply 119 on conductor 132,
and to dither circuitry 134 on condutor 133. Power supply 119
i9 a DC power supply, and suplies DC voltage to dither circuitry
134 over conductor 124, heart rate module 117 over conductor 123,
selector switch 105 over conductor 122,
mb/Jk - 7 -
~471~L~
electronics 107 over conductor 121, ampliEier electronics 103
over conductor 120, and speed control 150 aver conductor 151.
A rotational position input 112 is provided frorn
cylindrical drum 111 to electro-optics 113. The OUtptlt from
electro-optics 113 is provided to selector switch 105 on
conductor 114. A manual input 116, in the form of a push-
button switch (not shown) or other switch, is provided to
~elector switch 105.
Re~erring now to Fig. 2, cylindr:ical drum 200, which
rotates in direction 250, shows axially directed slit 201 at
its surface. Electro-optics assembly 113, located in general
at the periphery of the cylinder, provides input 114 through
selector switch 105. (In Fig. 2, phantom line 105 represents
the outline of selector switch 105 as shown in Fig. 1,) Input
114 is provided to reset circuitry 213, output thereof being
extended on conductor 210 to digital counter 204. The other
input to counter 204 is provided on conductor 203 from clock
202. Counter 204 provides an output on conductor 205 to ramp
generator 206. Output from ramp generator 206 is extended on
conductor 207 to one input of comparator 208. The other input
of compar~tor 208 is provided by heart rate module 117 on
conductor 137. 0utput from comparator 208 is extended on
co~ductor 209 as an input to monostable circuitry 214. Another
input to monostable circuitry 214 is manual input 116. 0utput
from mon~stable circuitry 214 is provided to solid state
switch 212 on conductor 2110 Other inputs to solid state switch
212 include inputs on conductors 135~ and 104O 0utpu~ from
solld state switch 212 is extended on conductor 106 to galvano-
meter drive electronics 107 as indicated in Figo 1.
mb/i~ - 8 -
1~4~ S
Next, proceeding with description of Figs. 3 and 4
prior to describing operation o the preferred embodiment, Flg,
3 depicts cylinder or ~riting surface 200 with slit 201, the
writing surface rotatably mounted about a substantially vertical
axis 350. Writing surface 200 can have cylindrical, conical,
or other shape. Writing surface 200 is intended to be adapted
for magnetic drum recording as well as paper displays. Thls
axis need not be vertical; however, for purposes of clarity of
illustration it is herein thus depicted. ~xis 350 is shown
rotatably mounted to base or chassis ~00 in Fig. 4. Galvano-
meter pen 300 is arranged to scribe on the surface of cylinder
or drum 200, there being chart paper or paper 351 (partially
indlcated for purposes of clarity of illustration) wrapped
around and fastened in slit 201, It is to be understood that
paper 351 extends the entire substantial length of cylinder or
drum 200 and essentially wraps around and covers the surface
area of the drum. Pen 300 scribes or writes on paper 351.
Lead screw 302 is shown substantially parallel to axis
350 and is likewise rotatably mounted to chassis 400. Rod 303
i8 fixedly mounted parallel to lead screw 302. Sliding on rod
303 is slidably mounted carriage 304 which, in turn, supports
galvanometer 301. Galvanometer 301 receives an electrical signal
input on conductor wires (not shown in Figs. 3, 4) which signals
are transduced into mechanical motion of pen 300. Motor 305
(depicted in Fig. l as 129) provides rotational output to gear
train 307 tdepicted in Fig. l as 125). The gear train provides
rotational motion 250 to cylinder 200 about axis 350, and provideq
rotational motlon to lead screw 302 about its longitudinal axis,
Carrlsge 304 is threadingly en8aged with threads of lead screw
302, Thus, rotatlonal mo~ion of lead screw 302 provides trans-
latlonal motlon
mb/~ 9
,
~4~
of carriage 304 in a dlrection substantlally parallel to axis
350. Gears of gear train 307 are des-lgned to provide a plurality
of rotations of drum 200 corresponding to a slngle motion in a
translational manner from the top of drum 350 (an initial posltion)
to the bottom of drum 350 (a final position), Thus, gear train
307 need not have the specific arrangement depicted in Fig. 3.
When chassis 304 reaches final position, it makes physical contact
and operates micro-switch 306. The micro-switch is electrically
connected between power 131 and motor 305 3 and operation of the
micro-switch disconnects power to the motor thereby stopping the
rotational and translational motions of the system. There is
provided carriage disengagement means (not shown) for rapid
return of the galvanometer to the initial position~ not causing
the drum to rotate.
In Fig, 1, electro-optlcs 113 was depicted as being
functionally connected between the drum and the selector switch
105. In Pigs. 3 and 4, the electro-optics 9 which is comprised of
phototransistors and photodiodes, commercially available, are
mounted as shown. Electro-optic elements 113a and 113b are
approximately 90 displaced on the periphery of one end of drum
200. These electro-optical elements rotate with the rotating dru~.
Mounted on base or chassis 400 is a fixed electro-optic sensor
113c. As the rotatable electro-optical elements 113a and 113b in
turn pa9s ad~acent electro-optical element 113c, optical communi-
catlon is achieved there betweenD The purposes of these optical
elements will be discussed more fuliy below~
Slit 201 is shown in Fig~. 2, 3, and 40 Chart paper
having fixed length and having substantially parallel edges may
be wrapped around drum 200. Edges of paper 351 are inserted into
slit 201 and are fastened there~n by rotatable
mb/`~f~ ; 10 -
~ L~D47~LS
clamping con~rol 352.
In operation, the preferred embodiment as descrlbed
in Fig~ 4, and the obtained dlsplay of Fig. 5 to be described,
provides a compressed EKG ~or other vital sign) data display.
The RKG signal of patient 101 is amplified in electronics 103,
extended to selector switch 105 extended to galvanome~er driver
electronics 107 which drives galvanometer pen means 301 which
in turn causes pen 300 to scribe on paper 351 supported on
cylinder 200. While this signal is being applied to pen 300
and while scribing motion is taking place, cylinder or drum 200
rotates in direction 250. Si~ultaneously carriage 30~ translated
in a downward vertical direction. This combined rotational and
translation motion crestes a helical base line on paper 351.
(It is intended herein that the words "helix","spiral" and "cQil"
can be used interchangeably.) The result can be seen in Fig. 5.
In Fig. 5, paper 500 (which is shown partially as
paper 351 in Fig. 3? is depicted as having usable display length
511 which corresponds to the circumference of drum 200, Dotted
lines 501 indicate where folds of the paper are made for insertion
of these folds into slit 201 as described earlier. Paper 500 is
shown in a broken diagrammatic fashion for purposes of clarity
of illustration. A time scale of zero through sixty seconds is
provided and break 504 in the paper takes place at approximately
be~ween 23 seconds and 53 seconds.
The scribing of pen 300 on paper 500 provides EKG wave
fDr~s 502. As intended to be depicted by lines 508, 509, 512,
and 513, the entire surface of the page can be scribed with EKG
signals. As noted earlier, the base line scribed on the surface
m~
~471~
of paper 500 when mounted on drum 200 would be a helix or spiral
When the paper is removed from slit 201 and opened flat, straight
lines with a slightly downward slope are observed. Thus, data
line 2 identified by numeral 2 at the left-hand edge of the usable
display paper, corresponds in time to the end of data line 1
identified as 2' at the right-hand data e~ge of the paper.
In other words, lines of EKG data are identified by
numerals 1, 2, 3, and 4 ....n, and the end of each line corresponds
in time to the beginning of the next successive line. Thus, the
point marked 2' corresponds in time to the end of line 1 and the
beginning of line 2, The designation "n" indicates that there
are an extensive plurality of data lines obtained and limited
only by size of paper and drum. The preferred embodiments are
designed to provide 60 seconds of data per line with 30 lines
per sheet thereby displaying a half hour of electrical heart
activity and to provide four minutes per line with 30 lines per
sheet thus providing a two hour displayO
Reference numeral 510 depicts a selectable period of
time during which heart rate is averaged in heart rate module 117
co~prised of standard circuitry. Module 117 is triggered by each
EKG wave to provide a constant width and constant amplitude
pulse output in response thereto. This pulse train is then
averaged on capacitor circuitry or other means to provide a DC
level corresponding to average heart rate.
Turning to Fig. 2, heart rate module 117 provides this
DC voltage to comparator 208. Digital counter 204 is reset by
a signal coming from optics 113 when pen 300 i5 positioned at slit
201 as will be fully explained below, This is the zero or reset
setting for the scribing motion. Digital
mb/l~ - 12 ~
" ~471~5
`- counter 204 is stepped by clock generator 202 once each second.
Clock generator 202 iB synced to 60 hertz power 131. At a pre-
determined count, which according to Yig. 5 i9 equal to about
56 counts (or 56 seconds), ramp generator 206 is energi~ed.
Counter 204 is constructed from standard digital circuitry and
may be a ring counter. Ramp generator 206 is likewise con~
structed from standard circuitry for charging a capacitor in a
linear fashion. Thus, ramp generator 206 is energized after
about 56 seconds and this energlzation takes place at line 520
on Fig. 5. Comparator 208 compares the two inputs and at co-
incidence between ramp generator voltage and DC ~oltage on
conductor 137, the comparator output is extended on conductor
209 to monostable 214. Comparator 208 is likewise standard
operational amplifier clrcuitry. Omission of deta~led discussion
of the circuit elements in these standard circuits does not
inhibit full understanding of the present invention.
In Fig. 1, dither generator 134 is powered by AC line
power 131 and is a conduit for 60 hertz power at a substantially
reduced power value. This 60 cycle/second signal is provided on
conductor 135 in Fig. 2, to solid state switch 212. Operation
of monostable 214 causes connection of the dithering signal on
conductor 135 to output conductor 106, Solid state switch 212
is comprised of standard transistor switching circuitry and
omission of detailed description does not detract from complete
understanding of the present invention. The average DC voltage
~enerated by heart rate module 117 corresponds ta rate scale 506
in Fig. 5 and thus, dithering mark 505 is indicated to be approx-
imately 60 beat~
m~ 3
: ~471~5
per minute. After a predetermined period of time determined
by time constants of monostable 21~, solid state switch 212
returns to its prior connection of conductors 104 and 106,
thereby reconnecting the EKG signal to pen 300. Mark 505
indicates average heartbeat rate for time period 510 of line 1.
Accordingly, a dithering rate mark is provided in the other
lines of data. This is very useful information since it provides
at a glance a hlstogram effect of heartbeat rate change of the
patient over a long period of time.
Numeral 503a and 503b refer to ectopic beats, whlch are
clearly visible in this display. Another module which detects
ventricular premature beats ~a form of ectopic beats) can be
connected between conductor 115 and selectr switch 105 ir. a
manner slmllar to connectlon of module 117. A premature ventrL-
cular contraction detector is dlsclosed in applicant's U.S. Patent
3,616,790 entitled MULTIFORM VE~TRICULAR PREMATURE BEAT VETECTCR
issued on November 2, 1971, which discloses suitable background
information. Portions of circuitry disclosed in this paten~
can be used with other circuitry to provide a DC voltage corres-
ponding to the number of PVC's per data line. Similarly to the
hlstogram display of average heartbeat rate for a patient of a
lLne by line basis, a separate histogram can be displayed at a
different location of the paper having a
14 _
~.':', ' ~
1~47~1S
d-lfferent scale for lndicatlng the number of occurrences of
premature ventricular be~ts.
In Eig, 5, direction 522 represents d$rection of
translational motion of carriage 30~ umerical designation
507 represents cross hatching which may be spread throughout
the page in a uniform manner as depicted. It is illustrated
only in a portion of sheet 500 for the purpose of clarity of
illustration.
Fig. 1 and Fig. 2 indicate manual input 116 to
selector switch 105 and more specifically tomonostable circuitry
214. This ùtilizes a push-button or other manual switch
arrangement whereby the phyician or operator of the system can
mark at ~ill on sheet 500, a dither signal such as mark 521.
As before, output 211 from monostable 21~ causes solid state
switch to make a connection between conductors 135 and 106.
Dither generator 134 provides a 60 cycle dithering signal to
conductor 106 and thus to pen 300 which scribes in a dithering
or vibrating manner on chart paper 500. Dither mark 521 is
displayed at this point in Fig. 5 ~or a special reason. It
marks the occurrence of a significant event such as patient
complaints of discomfort, or infusion of a drug, or the begin-
ning of exercise testing, etc.
After one minute and 21 seconds of EKG recording, the
p tient is subjected to exercise testing (not shown, but can be
treadmill walking with EKG leads attached to the patient). A
feature of the present invention is a speed-up switch 15~ as
shown in Fig. 1. This speed-up push-button switch, which is
de~ignated on the chassis of the preferred embodi~ent as "reset'79
increases the speed of the synchronous motor 129 thereby
mb/ ~ - 15 -
~471~S
operating gear train 125 more rapidly, As depicted in Fig, 5,
line 2, a~ter 22 seconds of recorded data, the galvanometer pen
iB translated to pocition 3' in a time ~hich is equal to or less
than the time between the last hearbeat and the next heartbeat.
At point 3', the speed control 150 is returned to its standard
speed arrangement. A purpose of this feature is to provide the
beginning of exerc$se testing at a beginning point of line 3
for purposes of clarity of presentation for later analysis.
Speed controi 150 is a device which changes current flow to
motor 129 ~305).
LiXewise, as noted the same display method can be
utilized with other tests such as drug testing. If the patient
is given certain drugs for medical reasons, the speed control
can be operated to "reset" the display, where the heartbeats
begin from the left-hand side of the paper as described above.
From Fig. 5, it is seen that approximately 8 seconds
elapse after exercise begins before a noticeable change in heart
rate occurs. This time value may not be realistic but does not
detract from understanding of the present invention. Manual
means 116 may also be operated to create designation 521 indicat-
ing the beginning of the increased heart rate.
Optlcal pick-ups 113a, 113b, and 113c are utilized in
the operation of speed control 150 as well as in other features
of the present invention. Speed control 150 is made to return
to its original state when optical pick-up 113b ~s
~ i'k - 16 -
,
.
:1~47115
- in optical communication with pick-up 113c. At ~hls point,
galvanometer pen 300 i8 positioned at slit 201. A signal from
optical pick-up 113c causes the switch in speed control 150 to
return to its original state.
The optical pick-ups function in at least two modes.
The first mode was described above. When the "reset button"
i8 depressed speed control 150 is operated and causes drum 200
to move rapidly until optical pick-up 113b is aligned with
optical pick-up 113c, (thus causing pen 300 to line up with slit
201). In another feature, when a "load button" is depressed,
speed control 150 again increases speed of motor 129, thereby
increasing speeds of rotation and translation of the system
components. But, when optical pick-up 113a is in optical com-
munication with 113c, all motion of the sys~em is stopped.
Control 150 disconnects motor 129 from AC power line 131. This
load button is depressed when it i9 desired to have the slit
position to the fr~nt of the apparatus for easy access regarding
loading and unloading of the paper. Depressing the "run" button
reconnects power to the motor.
The invention may be embodied in yet other specific
forms without departing from the spirit or essential character-
istics thereof. For example, one can use three galvanometers
with three galvanometer pens to monitor EKG leads 102. Leads
102 generally are three in number, and each of these leads may
be thus monitored. Thereby, lines 1, 29 and 3 in Fig. 5 could
be made to represent the outputs from three leads 102 from
patient 101. However, pitch or relative speed of lead screw
302 must be altered to accommodate this featureO In
mb/l~ - 17 -
~47~15 -
order for this to work properly, the end of line 1 would have to
correspond to the beginning of line 4, being sufficiently
displaced downward so as to not create interference with other
lines corresponding to the other two leads. Furthermore, other
sensors may be used to sense other vital signs (e.g.: blood
pressure) simultaneously with EKG. For another example, it is
to be understood that speeds other than constant speeds can
be utilized in the translational motion and rotational motions
of the invention. Rather than providing continuous translational
motion of carriage 304 transverse to direction of paper motion,
one could provide ra~chet means for stepping carriage 304 in
transverse manner upon each completion of a revolution of drum
200.
~t i9 to be understood that other means oE paper
attachment could be made. An assembly cartridge including drum
and paper could be used where one cylinder with paper is removed
and another cylinder with paper is installed ~where the paper is
not a single sheet but is an endless loop or belt of paper).
Furthermore, if cylinder 200 were held in a horizontal
position (rather than vertical as shown for purposes of clarity
of illustration only), a paper loop of the endless belt variety
(not shown), can be used which has a circumference in excess of
the circumference of drum 200. The system ~orks well if the
scribing point of contact between pen 300 and the surface of the
paper 351 on drum 200 remains smooth, Accordingly, even more
data can be recorded and displayed. And, another cylinder (not
shown) can be installed at a remote distance, to provide pulley
s~pport mesns for thi9 extended circumference endless paper loop,
However, these are alternative embodiments and the preferred
~0 embodiment is that which is shown in the Figures.
mb~ ~ - 18 -
~L~47~lS
It is to be further understood th~t more than 60
seconds or less than 60 seconds per line can be recorded and
that more than or le~s than 30 lines per page can be recorded.
A particularly advantageous util:Lty of the present
invention is in connection with the transc]ription of EKG
cassette tape recorders. Presently, portable tape recorders
exist which record a patient's EKG for long periods of time,
24 hours or more. Playback of 24 hours of EKG data at real
time would take thus 24 hours. On ordinary EKG chart paper, this
would amount to many feet of paper. But, to playback this
portable tape recorder data in a transcribing manner utilizing
the present invention, both the tape recorder and the present
invention's speed control can be increased by a factor of 20
or more (with respect to real time). Thus, all of this data
can be recorded on a large single sheet of paper in an hour
or less. The tremendous advantage of being able to analyze 2~
hours of EKG activity of a patient within an hour or less after
receiving that data on tape from the patient is cl~ar.
Thus, the present embodiments are to be considered in
all r~spects as illustrative and not restrictive, the scope
of the invention being indicated by the appended claims rather
than by the foregoing description and all changes which come
within the meaning and range of the equivalency of the claims
are therefor intended to be embraced therein,
mb 1-?~ - 19
