U.S. patent number 3,841,314 [Application Number 05/379,508] was granted by the patent office on 1974-10-15 for pulse activity indicator.
Invention is credited to Robert E. Page.
United States Patent |
3,841,314 |
Page |
October 15, 1974 |
PULSE ACTIVITY INDICATOR
Abstract
A cardiovascular monitoring system employs a photoelectric
monitoring circuit to obtain analog signals corresponding to the
heartbeat of a subject. Cooperating amplification and detecting
circuitry provide an audible tone corresponding to each pulse beat
as well as a readout of the pulse rate of the subject and blood
pressure. Circuitry is provided which detects and displays both
systolic and diastolic blood pressure. Additionally, an auxiliary
input permits selection of the subject's pulse at separate points.
Circuitry providing a simultaneous output for additional
electro-physiological measurement, such as electro-cardiograph
instrumentation, is also included.
Inventors: |
Page; Robert E. (San Diego,
CA) |
Family
ID: |
23497549 |
Appl.
No.: |
05/379,508 |
Filed: |
July 16, 1973 |
Current U.S.
Class: |
600/479 |
Current CPC
Class: |
A61B
5/02416 (20130101); A61B 5/02255 (20130101); A61B
5/02 (20130101); A61B 5/30 (20210101) |
Current International
Class: |
A61B
5/0428 (20060101); A61B 5/0402 (20060101); A61B
5/0225 (20060101); A61B 5/024 (20060101); A61B
5/02 (20060101); A61b 005/02 () |
Field of
Search: |
;128/2L,2.5A,2.5M,2.5P,2.5Q,2.5R,2.5T,2.6E,2.6F,2.6R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kamm; William E.
Attorney, Agent or Firm: Sciascia; Richard S. Johnston;
Ervin F. Skeer; William T.
Claims
What is claimed is:
1. A cardiovascular instrumentation system for measuring
cardiovascular activity having a plurality of positive peaks
comprising:
sensor means for generating an electrical analog signal of
cardiovascular activity of a living subject;
a linear amplifier connected to said sensor means for increasing
the power of said electrical analog signal;
first logic circuit means connected to said linear amplifier for
producing a digital pulse signal having a pulse duration
corresponding to the time of cardiovascular activity;
second logic circuit means connected to said first logic circuit
means for producing a digital signal having a pulse duration
corresponding to the length of time from the initiation of the
cardiovascular activity to the first peak thereof;
a first measuring circuit means connected to said second logic
circuit and to said linear amplifier for measuring the value of
said amplified cardiovascular analog signal in response to the
output of said second logic circuit means and connected to said
first logic circuit means for enabling said first measuring circuit
means to measure succeeding pulses;
a first display means connected to said first measuring for
providing an indication of the measured value;
third logic circuit means connected to said first logic circuit
means for generating a digital signal having a pulse duration
corresponding to the length of time from the initiation of the
cardiovascular activity to a second peak thereof;
a second measuring circuit means connected to said third logic
circuit and to said linear amplifier for measuring the value of
said amplified cardiovascular analog signal in response to the
output of said third logic circuit means and connected to said
first logic circuit means for enabling said second measuring
circuit means to measure succeeding pulses;
a second display means connected to said second measuring circuit
means for providing an indication of the measured value;
a stabilized voltage source;
a trigger generator circuit connected to said first logic circuit
means for generating a pulse in response thereto;
a first switch means connected to said trigger generator circuit
and to said stabilized voltage source for timely switching said
voltage in response to the trigger pulse;
a capacitor connected to said first switch to be charged to the
stabilized voltage upon operation of said first switch means;
a plurality of resistances connected to said capacitor to serve as
a discharge path therefor;
a plurality of switch means, each connected to one of said
plurality of resistances and effectively connected to said capcitor
to complete the discharge path; and
fourth logic circuit means connected between said trigger circuit
means and said plurality of switches for sequential energization of
each switch.
2. A cardiovascular instrumentation system according to claim 1
wherein said sensor means includes:
a receptacle configured for receiving a part of the anatomy of the
test subject;
light source means mounted on one wall of said receptacle for
emitting light energy for impinging the part of the anatomy of the
test subject engaged therebetween;
photo-electric detector means mounted on the opposite wall of said
receptacle from said light source electrically connected to said
linear amplifier means and positioned to intercept the light energy
passing through the engaged part of the anatomy of the test
subject;
secondary electrophysiological detector means carried by a wall of
said receptacle and configured to contact the engaged part of the
anatomy of the test subject;
amplifier means electrically connected to said secondary
electrophysicalogical detector means for increasing the detected
signal means; and
connector means electrically connected to said amplifier means for
cooperatively coupling said amplified signal to an external
indicator for simultaneous inspection thereof with the measured
value of the cardiovascular activity displayed by the aforesaid
first and second display means.
3. A cardiovascular instrumentation system according to claim 1 in
which said fourth logic circuit means includes:
a plurality of monostable multivibrator circuits each connected to
one of the plurality of switch means except the last switch means
and series connected to each other for sequential operation in
response to the aforedescribed trigger pulse; and
fifth logic circuit means connected to said plurality of series
connected monostable multivibrator means, and connected to the
aforesaid first logic circuit means, and connected to the last of
said plurality of switch means for actuating said last switch means
in response to the absence of any of the outputs from said
plurality of monostable multivibrator means, and the presence of an
output from said logic circuit means.
4. A cardiovascular instrumentation system according to claim 3 in
which said first logic circuit means includes a zero-crossing
detector.
5. A cardiovascular instrumentation system according to claim 4 in
which said second logic circuit includes a monostable
multivibrator.
6. A cardiovascular instrumentation system according to claim 5 in
which said third logic circuit means includes a monostable
multivibrator.
7. A cardiovascular instrumentation system according to claim 6 in
which said first and second measuring circuit means are sample-hold
analog voltmeter circuits.
Description
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or
for the Government of the United States of America for governmental
purposes without the payment of any royalties thereon or
therefor.
FIELD OF THE INVENTION
The invention pertains to the field of biomedical instrumentation.
By way of further explanation, this invention pertains to the
electronic instrumentation of the cardiovascular condition of a
living subject. In still greater particularity, the invention
provides simultaneous indications of a plurality of cardiovascular
conditions. The invention is further characterized by providing an
indication of both systolic and dynamic diastolic pressure. By way
of further explanation, this invention pertains to an instrument
which provides a readout of the pulse rate of a living animal
together with an audible indication thereof. Further, the invention
provides an instrument which will read the pulse rate at a
plurality of spaced points on a living animal and will provide an
indication of the pulse rate as well as the dynamic diastolic and
systolic blood pressures at the selected points.
Description of the Prior Art
In modern times great advances have been made in biomedical
instrumentation. Particularly, significant strides have been made
in the instrumentation pertaining to the circulatory system. Such
information has become the basis of the diagnosis of certain
abnormal conditions as well as the determination of normal
conditions in a variety of animals including humans.
Traditionally, a physician or biological research worker has
listened to the audible pulses produced by the heart of a living
organism by mechanically coupling his acoustic sensory channels to
the body cavity of the subject. The apparatus permitting this
acoustic coupling, termed stethoscope, form the basis of the
historical development of the cardiovascular instrumentation arts.
In modern times, the field of electronics has made wide inroads
into other disciplines and devices substituting electrical pickups
for this audio energy and its amplification to a usable signal have
become commonplace. These electronic techniques have also been
successfully employed to provide other indications of
cardiovascular condition by incorporating such circuitry with other
instrumentation advances. One example of such electronic
amplification is shown by the U.S. Pat. No. 3,651,798 for "Blood
Pressure Indicator and Noise" issued to Paul H. Egli et al on Mar.
28, 1972.
It is also known in the biomedical instrumentation arts to use
photoelectric response of a photo cell positioned to intercept a
light beam passing through a narrow portion of the human body as a
biomedical detector. As an example of such a device, attention is
invited to U.S. Pat. No. 3,628,525 for "Blood Oxygenation and Pulse
Rate Monitoring Apparatus," issued to Michael L. Polanyi on Dec.
22, 1971, in which the earlobe of a patient is monitored to
indicate the amount of oxygen in the blood stream. These systems,
described above, and others are examples of a large fund of
clinical instrumentation knowledge. In general, however, only
little inroads have been made in the more ordinary doctor-patient
or research-subject relationship. In general, these more ordinary
situations are still monitored by conventional stethoscope on
chronometer method.
The traditional method of obtaining a pulse strength and rate
information leaves something to be desired in both the time
required to perform it, the accuracy of the information obtained,
and the relevance of the information obtained to the normal
condition of the subject. That is, the technique requires trained
personnel. Too, the results are influenced by psychologically
generated stresses caused by the investigation itself.
Additionally, the results do not show short time variations as may
occur from one heartbeat to the next.
Thus, there has been a need for an instrument which would provide a
plurality of cardiovascular indices without psychological intrusion
of the patient or subject and which would require a minimum of
expenditure of time by trained personnel. Additionally, a system
which would reveal short term variations in the cardiovascular
system of the subject undergoing examination is a long-felt,
unsatisfied need in the biomedical investigative field.
SUMMARY OF THE INVENTION
The invention provides a blood pressure and pulse rate meter which
provides an instantaneous readout of the pulse rate of the subject
and which has a minimum of interference with the subject. In
particular, a photoelectric pickup provides an electrical analog of
the blood flow of the subject. This electrical analog is converted
to information readouts indicating the pulse rate, dynamic
diastolic, and systolic pressure of the subject. Additionally,
provision is made for an audible indication of the pulse beat.
STATEMENT OF THE OBJECTS OF THE INVENTION
It is the primary object of this invention to provide an improved
cardiovascular instrumentation system.
Another object of the present invention is to provide an improved
pulse activity meter.
Still another object of the present invention is to provide a
cardiovascular instrumentation system having a very fast response
time.
Still another object of the present invention is to provide a
cardiovascular instrumentation system which indicates the blood
pressure of the subject.
Still a further object of the present invention is to provide a
cardiovascular instrumentation system which provides a readout of
both dynamic diastolic and systolic blood pressures.
Yet another object of the present invention is to provide a
cardiovascular instrumentation system having a non-invasive
photoelectric input.
These and other objects of the invention will become more readily
apparent from the ensuing specification when taken with the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view showing the invention in use;
FIG. 2 is a front elevational view showing the invention in
use;
FIG. 3 is a block diagram showing the interface of the various
circuits comprising the system of the invention;
FIG. 4 is a partial sectional view of a photoelectric detection
system used in the invention;
FIG. 5 is a schematic showing of the electrocardiogram detector
circuit of FIG. 3;
FIG. 6 is an illustration of waveforms useful in understanding the
operation of the invention;
FIG. 7 is a schematic representation of the detector circuit and
associated logic circuitry used in the invention;
FIG. 8 is a graphic representation of the solution of pulse rate
versus time;
FIG. 9 is a simplified diagrammatic showing of the pulse rate
circuit and readout of FIG. 3.
FIG. 10 is a schematic representation of the circuit of FIG. 9;
FIG. 11 is a waveform diagram of logic control pulses generated by
the circuitry of FIG. 10;
FIG. 12 is a simplified diagrammatic showing of the systolic and
diastolic pressure circuits of FIG. 3; and
FIG. 13 is a schematic representation of the circuit of FIG.
12.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a console 21 encloses the circuitry comprising
the cardiovascular instrumentation system of the invention. In
operation, console 21 is placed on a suitable support and
convenient to subject 22 whose cardiovascular responses are being
monitored. As shown, a portion of the anatomy of subject 22, here a
finger, is placed within an aperture provided in console 21.
Additionally, a pickup 23 may be attached to subject 22 at the
position spaced from the portion received in console 21, and the
circuitry contained therein, by means of a suitable electrical
conductor 24.
Although subject 22 is illustrated as a human being, the system of
the invention performs equally well with other members of the
animal kingdom. In particular, it should be specifically noted that
the invention has proven satisfactory for the measurement of
cardiovascular responses of certain of the marine mammals.
Referring to FIG. 2, a plan view of the front of console 21 is
shown as it would appear in operation. Along the lower edge of
console 21, an input switch 25 is positioned to be movable between
two positions corresponding to the internal pickup and the remote
pickup. Switch 25 performs other switching functions as will be
more completely described herein. To the left of switch 25, an
electrical connector 26 is positioned for the convenient sampling
of additional electro-physiological phenomena which may be
monitored by the device of the invention. To the left of connector
26, another connector 27 is positioned to serve the purpose of
providing external oscilloscope connection. An external
oscilloscope permits the operator to view the electrical pulse
analog of subject 22. A pilot light 28 is positioned to the left of
scope connector 27 and indicates whether console 21 is energized by
means of a power switch 29 which is positioned to the left
thereof.
Optionally, the circuitry comprising the invention may be
internally powered by battery power sources, not shown. In such
instances, pilot light 28 provides a rough indication of battery
strength and, if desired, may be replaced with a conventional
battery powered indicator having more accurate power monitoring
capabilities.
Suitable meters 31, 32, and 33 are positioned vertically in line
above switch 25, connectors 26 and 27, and pilot light 28. The
uppermost of these, meter 31, indicates the systolic blood pressure
of subject 22. Directly beneath meter 31, meter 32 provides an
indication of the diastolic blood pressure of subject 22. Finally,
meter 33 provides an indication of the pulse rate of subject 22.
Meter 33 also provides a calibration marker which is useful in
calibrating the optical portion of the circuit.
Along the right hand edge of console 21 and arranged in vertical
alignment, three rotary motion controls, control 34, switch 35, and
control 36, are positioned in vertical alignment. Control 34 is a
"Normalize" control and is used to adjust the gain of the system to
a preestablished datum level. Switch 35 is movable between a
calibrate and a read position and is used to adjust the internal
circuitry of console 21 in a manner to be further described so as
to permit the calibration of the optical system. Control 36 is a
"Calibration" control and when the calibration switch 35 is placed
in the calibration position, CAL., is used to calibrate the optical
system.
In the illustrated position, subject 22 is shown to have a systolic
pressure of 140, a dynamic diastolic pressure of 90, and a pulse
rate of 62.
Of course, other arrangements of front panel controls may be
provided if desired. Likewise, other switches, connectors, and
controls may be positioned on the front panel of console 21 if
desired. However, those controls illustrated in FIG. 2 have proven
to be the minimum necessary for successful operation of the
invention by medical technicians and were chosen to minimize the
amount of training required to satisfactorily use the
invention.
Referring to FIG. 3, a block diagrammatic representation of the
major circuit groupings housed within the console 21 is
illustrated. As shown, two pulse detectors, indicated at 38 and 39,
are selected by switch 25. Switch 25 is shown as a three-section,
two-position switch, each section being designated as 25', 25", or
25'". Section 25' selects an appropriate output from either pulse
detector 38 or pulse detector 39 and feeds the output to a pulse
rate readout circuit 42. Section 25" connects the output of either
pulse detector 38 or pulse detector 39 to a systolic pressure
circuit 43 and a diastolic pressure circuit 44. Each of these
pressure circuits has an appropriate associated readout 45 and 46.
Section 25'" selects a linear output from either pulse detector 38
or pulse detector 39 and feeds it to connector 27 for external
viewing, as previously described.
As noted above, console 21 may also monitor other
electro-physiological phenomena of subject 22. In the illustrated
arrangement of FIG. 3 this comprises an electrocardiogram detection
amplifier 41. Although other electro-physiological phenomena may be
monitored, the invention will be described as including an
electrocardiogram detection.
Referring to FIG. 4, a sectional view of an illustrative example of
a photoelectric pickup employed by the invention will be described.
As shown, console 21 is apertured to receive the finger of subject
22. A receptacle 47 is supported by the wall of console 21 and
extends inwardly so as to receive the finger of subject 22.
A soft rubber pad 48 is mounted on the innermost wall of receptacle
47. Pad 48 is used as an index for subject 22 to press his finger
against. In this manner, the finger is assured to be over an
optical housing 49 which extends from the lower side of receptable
47. The depth of receptacle 47 and the dimensions of pad 48 are
chosen to conform with the average physical dimension of the
portion of the anatomy of subject 22 through which the pulse is
monitored. In case of a finger, the area covered by the fingernail
has proven most satisfactory. A wall 50 of receptacle 47 is
positioned on the other side with respect to optical housing 49 and
is resiliently biased to engage finger of subject 22. This
engagement pressure is chosen so as to be light enough to avoid
deleterious effects on the circulatory system of subject 22 and,
yet, sufficiently strong to minimize inadvertent motions, termed
artifacts, of subject 22 which might introduce erroneous readings.
A transparent member 51 is mounted on the lower wall of housing 47
and a similar transparent member 52 is mounted in and carried by
wall 50.
Transparent member 52 is shown as a plain unfigured transparent
window. However, transparent member 52 may be configured to form a
lenticular surface so as to provide a beam-forming function. A
source of light energy, here incandescent bulb 53, is positioned
above transparent member 52. The envelope of incandescent bulb 53
may also be figured such as to have an optical beam forming
function.
Transparent element 51 is positioned opposite transparent element
52 and transmits the light passing through the finger of subject
22. A lens 54 is carried within optical housing 49 and focuses the
emerging light beams onto the sensitive surface of a suitable
photo-electric detector 55, here a photo-semiconductor.
Photo-semiconductor 55 is connected by means of suitable electrical
conductors 56 to the remainder of circuitry housed within console
21.
Although optical housing 49 is illustrated on the lower surface of
receptacle 47 and the light source including light bulb 53 and
element 52 are located on the resiliently biased opposite wall 50,
it should be apparent that the reversal of these two parts is well
within the scope and intent of the invention.
An EKG pickup is provided by a contact 57. Contact 57 is mounted in
the one wall of receptacle 47 by means of a suitable insulating
surround 58. The positioning of electrode 57 is such as to monitor
the electro-physiological activity of subject 22. Electrical
connection to contact 57 is provided by means of a suitable
conductor 59.
As previously indicated, a second photoelectric pickup may be
provided if desired. In such instances, the construction of the
pickup is essentially similar to that shown in FIG. 4 but housed
such as to be portable. Such pickups are known in the art and, for
purposes of completeness, it should be noted that the photoelectric
pickup shown in U.S. Pat. No. 3,628,525 issued on Dec. 21, 1971 to
Michael L. Polanyi for "Blood Oxygenation and Pulse Rate Monitoring
Apparatus" may be used with suitable modifications, if desired.
Such modifications would include the adjustment of clamping
pressure such as not to interfere with normal blood flow of subject
22 within that area.
Referring to FIG. 5, the details of an EKG detector amplifier
circuit 41 will be described. As shown, conductor 59 transmits the
electrical energy from contact 57 to an input of an integrated
amplifier module 61. Similarly, a conductor 62 from the other EKG
contact, not shown, carries a similar signal to an identical
integrated amplifier module, shown at 63. Modules 61 and 63 are
connected by the illustrated resistance and capacitor network to a
third integrated amplifier module 64 which amplifies the signals
and produces a linearly amplified output signal. As previously
noted, this output signal is fed to the EKG connector 26. Suitable
state-of-the-art operational amplifiers may be used for amplifier
modules 61, 63, and 64. However, for purposes of illustrative
completeness, it should be noted that developmental models employ
all type 741 integrated amplifier modules. Such amplifier modules
provide adequate output voltage to drive existing state-of-the-art
EKG recording and display apparatus.
Of course, the EKG detector amplifier 41 and associated circuitry
is not an essential part of the cardiovascular system of the
invention but may be incorporated with a small additional cost.
This small cost, especially when considered with the versatility
provided, justifies the inclusion in such a system. As noted above,
and as recognized by those versed in the electronic arts, other
sensor mechanisms may be used in place of EKG detector amplifier
circuitry 41.
Referring to FIG. 6, an illustration of basic waveforms developed
by the invention will be described. An analog of the pulse beat
indicated as Ia is shown as waveform 65. The waveform 65 exhibits
the characteristic double hump pulse wave developed by the opening
and closing of the valves within the heart of subject 22 and the
vascular responses thereto. A peak 66 occurring at time L1 is
indicative of that pressure known as systolic pressure. A smaller
peak 67 occurring at a time L2 is characteristic of that pressure
peak known to be associated with the diastole of the heart and the
diastolic blood pressure. The waveform represents the amount of
blood in the optical path. The first peak 66 corresponds to the
contraction of the heart muscle. The second peak occurs after the
initial contraction and corresponds to the relaxation of the heart.
The peak is due to secondary expansion of the blood vessel by fluid
dynamics arising from the action of the heart, the flexibility of
the blood vessel and other circulatory variables. Because this
information is related to the diastolic blood pressure and occurs
during the initial diastole of the heart, it is given the name
dynamic diastolic pressure by the inventor.
Waveform 68 shows a digital index signal having a square-wave pulse
corresponding in length to the pulse duration of the analog index
waveform 65.
Waveform 69 is a systolic index pulse and has a square-wave profile
having a pulse length corresponding in time of occurrence and
duration to time L1 or the peak of the systolic pressure.
Waveform 70 is a digital square-wave having a profile which
corresponds in time of occurrence and duration to the time of the
diastolic pressure peak, L2.
Referring to FIG. 7, the schematic presentation of a pulse detector
circuit is illustrated. At the outset, it should be noted that
pulse detector circuit 38 and pulse detector 39 are identical
circuit configurations. Therefore, for purposes of brevity and
clarity, only our pulse detector circuit will be described.
As shown, light bulb 53 is connected to a voltage source through
the "CAL.-ZERO" control 36. By contrast, photoelectric detector 55
is connected to a voltage supply source through a fixed resistance
network. Thus, with a given absorptive medium between lightbulb 53
and photoelectric detector 55, adjustment of calibrate control 36
will vary the voltage developed across photoelectric detector 55.
This voltage may be measured by a meter 33, as previously noted, by
placing switch 35 in the "CAL." position. The output of
photoelectric detector 55 is capacitively coupled to a linear
amplifier module 71. The gain of amplifier module 71 is controlled
by "Normalize" control 34 which is connected thereto. The linear
output of amplifier module 71 is connected to scope output
connector 27 by means of switch 25'", as previously described. The
output of amplifier module 71 is further amplified by a linear
amplifier module 72 to produce the analog index signal Ia, shown in
FIG. 6 as waveform 65. The output of linear amplifier module 72 is
resistance coupled to integrated amplifier module 73 which is
configured as a zero-crossing detector. The output of amplifier 73
is the required digital index signal I, shown as waveforms 68 in
FIG. 6.
The digital index signal output from integrated circuit 73 is
connected to an integrated logic circuit 74. Circuit 74 is
connected as a monostable multivibrator. The pulse width of the
output of logic circuit 74 is determined by a resistance connected
between pins 9 and 14 thereof. This resistance is adjusted to
produce an output which is coincident with the systolic pressure
peak as indicated as waveform S shown at 69, FIG. 6.
The adjustment of this resistance is facilitated by observing the
analog index signal on the oscilloscope connected to connector 27,
as previously described. An output from logic circuit 74 is
connected to key a free running audio oscillator 75 which produces
an audio frequency output which is coupled, via volume control 76
to an appropriate transducer 77. This audible signal provides a
rough measure or indication of the operability of the circuit as
well as permitting the checking of the pulse rate by conventional
means.
Index waveform 68 is also coupled to a logic circuit 78 which is
connected as a monostable multivibrator in a similar fashion to
circuit 74. The resistance connected between pins 9 and 14 of
circuit 78 is used to adjust the pulse duration of the output to
correspond with the diastolic pressure peak indicated as waveform
70, FIG. 6.
Before considering the precise fashion in which the pulse rate of
subject 22 is determined by the invention, an analysis of the pulse
rate problem should be considered. FIG. 8 shows a diagram of the
pulse rate equation, pulse rate equaling 60 seconds divided by the
period between commencement of successive pulse in seconds. This
equation is graphed for pulse rates from 200 to 43 pulses per
minute. Of course, equation may be extended for other pulse rate
values. However, those shown have proven satisfactory for human
subjects and most sea mammals.
As shown, the graph solution 79 is broken into approximately linear
increments P1 through P4. A voltage analog corresponding to each of
these curve segments is given in association with its particular
segment. Dividing this range into the four increments shown has
proven satisfactory for accuracies of plus or minus two percent
over the entire range. Quite naturally, if greater linearity is
desired, a greater number of increments may be used.
FIG. 9 illustrates a simplified computer which will solve the
equation illustrated in FIG. 8. As shown, a capacitor 89 is charged
to a reference voltage by the closure of a charge switch 80.
Capacitor 89 is permitted to discharge through resistances 81, 82,
83, and 84. The rate of discharge may be controlled by the value of
the resistances to approximate the slopes given by the equations
shown in FIG. 8.
Each resistance has an associated switch connected therewith. Thus,
resistor 81 is connected by switch 85. Similarly, resistor 82, 83,
and 84 have switches 86, 87, and 88 associated therewith. If each
switch is closed in sequence corresponding to the time interval
indicated in FIG. 8, it may be seen that the resultant voltage on
capacitor 89 will correspond to the graphic solution represented by
curve 79. Thus, if each switch is closed for its appropriate period
during the duration of index pulse 68, the resultant voltage on
capacitor 89 will be the electrical analog of pulse rate as shown
in FIG. 8. This voltage is amplified by operational amplifier 90
and transferred, via hold switch 91, to an appropriate storage
capacitor 92. The stored voltage on capacitor 92 is read by
operational amplifier 93 and connected to the suitable pulse rate
meter 33.
Thus, it may be seen that the analog of the pulse rate of subject
22 may be obtained by timely energization of switches 85 through 88
during the duration of index pulse 68. A circuit for accomplishing
this electrical operation will now be described.
Referring to FIGS. 10 and 11, the circuit implementation
represented by the simplified diagrammatic showing of FIG. 9 will
be described. As shown, the systolic pulse output SI from
monostable multivibrator 74 toggles bistable multivibrator 94
which, in turn, triggers monostable multivibrator 95 which
generates as output C which is connected to an inverter 99 as well
as a succeeding monostable multivibrator 96. The duration of the
conduction pulse from monostable multivibrator 95 is controlled by
means of a variable resistance connected between pins 9 and 14 of
the integrated circuit. This circuit provides a charging switch
pulse of such length as to ensure the complete charging of
capacitor 89 to the reference voltage level and short enough so as
not to interfere with the switching pulse duration corresponding to
200 pulses per minute.
Inverter 99 has an output which is amplified and impedance matched
by a semiconductor 100 and is connected, via diode 101, to a
field-effect switch 80 so as to connect the source of reference
voltage to capacitor 89 for charging purposes, as previously
explained.
The conduction period of monostable multivibrator 96 is similarly
resistance-controlled and produces an output P1 which corresponds
in time duration to the period illustrated on FIG. 8 and is
represented by waveform 107, FIG. 11. The output of monostable
multivibrator 96 is connected, via a suitable inverter means, to a
semiconductor switch 85 which permits capacitor 89 to discharge
through resistance 81. The output of monostable multivibrator 97
which is resistance controlled to produce an output P2 which is the
reciprocal of waveform 108, FIG. 11. Monostable multivibrator 97 is
connected, via a suitable inverter, to restore the illustrated
waveform and trigger semiconductor switch 86, thereby permitting
conduction through resistance 82.
The output of monostable multivibrator 97 is also connected to a
monostable multivibrator 98 which is also resistance controlled for
conduction time. Monostable multivibrator 97 produces an output P3
which is inverted to produce output wave 109, FIG. 11. This signal
triggers semiconductor switch 87 and permits capacitor 89 to
continue discharging through resistance 83.
The output from monostable multivibrators 96, 97 and 98 are also
connected through suitable inversion logic circuitry to a switch 88
which permits capacitor 89 to finish discharging through resistance
84 in the absence of the output from the monostable multivibrators
96, 97, and 98 prior to the commencement of the next charge cycle
initiated by monostable multivibrator 94.
The charge on capacitor 89 is amplified by means of amplifier 90
and coupled to capacitor 92 by means of a semiconductor switch 91.
This connection of semiconductor switch 91 is controlled by means
of inverter 102, semiconductor 103, and diode 104 in response to
the output of monostable multivibrator 94.
As previously explained, capacitor 92 is coupled, via voltage
follower 93, to a readout 33 when the CAL.-READ switch 35 is in the
read position. It may also be desirable to provide a rear panel
connection to feed the analog pulse rate value to other auxiliary
equipment and is within the scope of the present invention.
Referring to FIG. 12, a simplified circuit arrangement is
illustrated for converting the analog output signal from pulse
detectors 38 and 39 to a dynamic diastolic and systolic pressure
reading. Since each of these pressure circuits is essentially the
same and differs only in the control circuit aspects, previously
discussed, they may be considered together for descriptive
purposes.
The analog input from voltage follower 72, FIG. 7, is connected,
via switch 111, to a capacitor 112. Capacitor 112, in turn, is
connected to voltage follower 114 and is selectively discharged,
via switch 113. The value stored on capacitor 112 is transferred to
a capacitor 116 by means of a hold switch 115 at appropriate timing
intervals. The charge stored on capacitor 116 is then connected to
a suitable readout, in the illustrated case systolic pressure meter
31, by means of a voltage follower 117 where it is displayed as a
reading thereon.
Thus, it will be seen that the operation of the systolic pressure
readout is similar to the pulse rate readout with the exception
that the initial capacitance is charged to a voltage analog of the
pulse waveform and is selectively read, without time delay, by the
monitor and hold system similar to that used in the rate signal
development circuit.
Referring to FIG. 13, the circuit implementation of FIG. 12 will be
described. As shown, the analog pulse signal is connected to
capacitor 112 by means of a semiconductor switch 111. Switch 111 is
controlled, via inverter 118, semiconductor 119, and diode 120, in
response to the S1 output of monostable multivibrator 74, FIG. 7.
As shown, the charge on capacitor 112 is transferred to capacitor
116 by means of a voltage follower 114 operating through
semiconductor switch 115. Semiconductor switch 115 transfers the
instantaneous analog value present on capacitor 112 as determined
by inverter 121, semiconductor 122, and diode 123 which are timely
energized by output signal S1 from monostable multivibrator 74,
FIG. 7. This signal is stored on capacitor 116 during the interval
of the duty cycle of the circuit and is read on meter 31 to which
it is coupled by means of a voltage follower 117. If desired, this
value may also be supplied to a rear panel output terminal 124, not
elsewhere illustrated.
The dynamic diastolic pressure readout circuit functions in
precisely the same way with the exception that inverter 118 and
inverter 121 receive the D1 and D1 outputs respectively from
monostable multivibrator 78, FIG. 7.
PREFERRED MODE OF OPERATION
The internal operation of the respective circuits comprising the
cardiovascular instrumentation system of the invention have been
adequately described in connection with the physical description of
the respective circuits. Since the operation of these circuits are
well understood in modern logic and signal processing technology, a
description thereof is unnecessary for the understanding of the
invention. However, a brief overview of the operation of the
complete instrument is believed to be helpful in the understanding
of the device and to better appreciate the highly advantageous
results made possible thereby.
Referring to FIGS. 1 and 2, subject 22 may be easily connected to
the instrument 21 by placement of the external pulse monitor
earpiece 23 on his earlobe and the insertion of his finger within
the aperture provided on the back of console 21. If desired, an
external finger monitor may be used to record the "fingerprint"
pulse implication. This alternative arrangement is particularly
advantageous when subject 22 is confined to a bed or immobilizing
test apparatus.
Once subject 22 has been connected to the monitor and the system is
energized, a pulse rate will immediately appear corresponding to
the heart rate of the patient. If this reading is erratic or
otherwise suspect a device may be calibrated for the individual's
skin opacity by placing the CAL.-READ switch 35 in the calibrate
position and adjusting the CAL.-ZERO control 36 to obtain the
referenced voltage. If desired, an audible tone corresponding to
the individual pulse beats may be heard in dependence upon the
setting of volume control 76, as previously described. Then,
control 34 may be adjusted to normalize subject 22's systolic or
diastolic pressure readings to a previously ascertained value.
The system is now completely operational and subject 22 may then be
subjected to the various medical tests and his cardiovascular
performance instantly monitored on console 21.
If a more complete cardiovascular diagnosis is required, an
oscilloscope may be connected to the scope output 27 and
appropriate electrocardiogram equipment may be connected to output
26.
Selection of the appropriate monitoring points, either earlobe or
fingertip, may be obtained by moving switch 25 to the appropriate
position, marked "INT" and "REMOTE."
The foregoing description taken with the appended claims constitute
a disclosure such as to enable a person skilled in the
bioelectronics and data processing arts and having the benefit of
the teachings herein to make and use the invention. Further, the
structure herein described meets the aforestated objects of the
invention and generally constitutes a meritorius advance in the art
unobvious to such a worker not having the benefit of these
teachings.
Obviously, many modifications and variations of the present
invention are possible in the light of the above teachings, and, it
is therefore understood that within the scope of the disclosed
inventive concept, the invention may be practiced otherwise than
specifically described.
* * * * *