Title:
PULSE ACTIVITY INDICATOR
United States Patent 3841314


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 R
Application Number:
05/379508
Publication Date:
10/15/1974
Filing Date:
07/16/1973
Assignee:
PAGE R,US
Primary Class:
International Classes:
A61B5/02; A61B5/0225; A61B5/024; A61B5/0428; (IPC1-7): A61B5/02
Field of Search:
128/2L,2
View Patent Images:
US Patent References:
3704706HEART RATE AND RESPIRATORY MONITOR1972-12-05Horczfeld et al.
3662746APPARATUS FOR DETECTING, ANALYZING AND RECORDING BIOELECTRIC POTENTIALS1972-05-16Saltzberg et al.
3661147PULSE RATE COUNTER AND DISPLAY AND METHOD OF OPERATION1972-05-09Mason et al.
3623476BLOOD PRESSURE MEASUREMENT APPARATUS1971-11-30Robillard
3572322N/A1971-03-23Wode
3400709Arterial blood pressure monitor1968-09-10Funfstuck
3227155Sphygmomanometric measuring apparatus1966-01-04Erickson et al.
3051165Apparatus for automatically measuring blood pressure and pulse rate1962-08-28Kompelien



Primary Examiner:
Kamm, William E.
Attorney, Agent or Firm:
Sciascia, Richard Johnston Ervin Skeer William S. F. T.
Claims:
What is claimed is

1. A cardiovascular instrumentation system for measuring cardiovascular activity having a plurality of positive peaks comprising:

2. A cardiovascular instrumentation system according to claim 1 wherein said sensor means includes:

3. A cardiovascular instrumentation system according to claim 1 in which said fourth logic circuit means includes:

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.