The invention is claimed as follows
1. A portable electrocardiographic signal apparatus comprising a housing, a display screen on the front of said housing, pickup electrode means carried by said housing on the back thereof and positioned externally thereof for placement against a patient's chest, mounting means for said electrode means extending into said housing, spring means mounted internally of said housing and bearing on said mounting means resiliently to bias said electrode means outwardly of said housing, positive stop means in said housing acting on said mounting means to limit outward movement of said electrode means, means in said housing engaging and laterally stabilizing said mounting means and hence said electrode means, electronic circuitry means in said housing interconnecting said electrode means and said display screen, and pistol grip means on and extending down from the bottom of said housing substantially centrally thereof for normal gripping of said pistol grip means by one hand of an operator to support said housing in one hand with said pickup electrode means against a patient's chest and said screen disposed toward said operator in ready viewing position for said operator to display an instantaneous electrocardiographic signal.
2. A portable apparatus as set forth in claim 1 including means for adjusting said pistol grip relative to said housing.
3. A portable apparatus as set forth in claim 1 and further including light sensitive means on the exterior of said housing interconnected with the electronic circuitry means of said apparatus to control the brightness of display of said screen.
4. A portable apparatus as set forth in claim 3 wherein said display screen and said light sensitive means are on the front face of said housing and the electrodes are on the back of said housing.
The human heart puts out an electrical signal of approximately 1 millivolt upon beating. Electrical signals commonly are picked up from the chest of a patient by electrodes making good contact with the skin on the chest by means of an electro-gel. Preferably the electrodes are arranged in a triangular pattern know an the Eindhoven triangle. The two outer, upper electrodes comprise pickup electrodes, while the lower central electrode is a ground electrode. The two upper electrodes serve as differential input electrodes to a differential amplifier circuit. The prior procedures have required relatively long electrode leads which are prone to picking up external electrical noises, and since the heart signal is of rather low potential, it is essential that the electro-gel be used to make good contacts, whereby to apply as high a signal-to-noise ratio to the inputs of the electrocardiograph machine as is reasonably possible.
The pattern which a normal human heart makes upon beating is well known, and has been known for many years. Electrocardiograms commonly have been made for many years by the use of a moving paper web and a pen leaving an impression thereon. Many cycles of heartbeat are recorded in this manner, and can be studied carefully by a doctor for any possible malfunction of the heart. However, such examination is time consuming, and hence costly, and requires cumbersome equipment, whereby electrocardiograms are not commonly made unless some heart problem is expected, or unless the patient is having an extensive physical exam.
It is known that a cathode ray oscilloscope can be substituted for the moving pen type of recording apparatus for making electrocardiograms, whereby there is an instant display. However, this again requires the use of expensive and cumbersome machinery with long lead wires, and with the necessity of electro-gel to make a good contact between pickup electrodes and the skin of the patient's chest. Thus, the taking of an electrocardiogram is discouraged unless it is thought to be essential for some reason. This is not wise, as it would be ideal to take an electrocardiogram frequently of any patient whose health is less than the best, in the same manner that temperature and blood pressure readings are now taken. Those skilled in the medical art will realize that an electrocardiogram can be far more significant in revealing cardiovascular difficulties than can the simple temperature and blood pressure tests.
Accordingly, in accordance with the present invention, it is proposed to provide novel apparatus comprising a small cathode ray oscilloscope, having a tube face for display of about 2 inches by 3 inches. The total depth of the apparatus is on the order of 6 to 8 inches. The apparatus is battery powered and is provided with a hand grip or handle so that it readily can be supported by a doctor or technician. Pickup electrodes are provided directly on the back of the cathode ray oscilloscope unit, whereby leads are surpassingly short. Furthermore, the leads and the entire electrical apparatus are shielded by being housed in a metallic case. Accordingly, it is not necessary to use the electro-gel to insure proper contact, since a useful signal can be obtained of lower magnitude than heretofore, and since additional amplification is of no particular problem since amplifier stages are relatively cheap and since the signal-to-noise ratio is quite high due to the substantial total exclusion of noise signals.
The present invention will best be understood with reference to the accompanying drawings and the following specification, wherein:
FIG. 1 is a perspective view illustrating the application of the apparatus of the present invention to the chest of a patient;
Fig. 2 is a side view of an apparatus constructed in accordance with the present invention;
FIG. 3 is a back view thereof as taken from the left end of FIG. 2;
FIG. 4 is a back view similar to FIG. 3 but showing a different type of electrode arrangement;
FIG. 5 is another back view showing yet another electrode arrangement;
FIG. 6 is a back view similar to FIG. 5 showing a still further electrode arrangement;
FIG. 7 is an enlarged fragmentary sectional view taken along the line 7--7 in FIG. 3 showing a detail of electrode mounting;
FIG. 8 is a view similar to FIG. 7 taken along the line 8--8 in FIG. 5; FIG. 9 is a fragmentary side view of the apparatus showing a modified form of handle or hand grip; and
FIG. 10 is a similar view showing a modification for AC or line current operation.
An electrocardiographic unit constructed in accordance with the principles of the present invention is shown at 20 in FIGS. 1-3. The unit or apparatus comprises primarily a cathode ray oscilloscope including a sheet metal housing 22 of rectangular frontal construction, and somewhat trapezoidal top and side views. The total length from front to back is on the order of 6 to 8 inches. The apparatus is provided with a cathode ray tube having a display surface of face 24 on the order of two inches by three inches. Control knobs are provided at 26, and a light sensitive device 28, preferably a cadmium selenide cell is provided on the front to control the brightness of the cathode screen display in accordance with ambiant room lighting.
The apparatus is provided on its underside with a pistol grip 30 so that it can readily be held by the hand 32, as of a doctor, and pressed against the chest 34 of a patient. A trigger 36 is provided behind the pistol grip 30 for depression by the index finger to activate the apparatus to provide the cathode ray screen with the desired readout of the heartbeat. An envelope of a normal heartbeat is shown in broken lines at 38, the scale being too small to reproduce the pulses displayed by a normal heartbeat.
The apparatus is provided on its back with three electrodes 40, 42 and 44. These are respectively the right side and left side electrodes (also known as negative and positive electrodes) and an indifferent electrode. These electrodes project only a very short distance from the rear of the apparatus so as to minimize problems of noise pickup.
Preferably, as shown in FIG. 7, each electrode, the electrode 40 being exemplary, is provided in the form of a disc 46 having a boss 48 on the rear thereof and having a socket therein cooperating with a ball 50 on the end of a shaft 52. The shaft projects from the rear wall 54 of the apparatus, and is resiliently urged outwardly thereof by a spring 56 encircling the shaft and trapped between an abutment 58, such as a C washer on the shaft and a depending stop 60 within the housing. A lead wire 62 extends from the inner end of the shaft 52 to the input of the electronic circuitry, illustrated as "black boxes" 64 and 66 in broken lines in FIG. 2. The cathode ray tube 68 having the face or display screen 24 also is shown in broken line outline in FIG. 2.
Reference heretofore has been made to construction of the case or housing 22 of metal for shielding purposes. As will be understood, the same ends can be attained by different means, such as by use of a molded plastic housing with a foil lining or conductive paint on the inner surface thereof.
A two lead pickup rather than a three lead pickup is shown in FIG. 4. In this figure the parts remain the same as heretofore described, similar numerals being used with the addition of the suffix a. The distinction is, that instead of having the three electrodes in the Eindhoven triangle, as illustrated in Fig. 3, there are but two electrodes 44a and 42a, respectively being the indifferent electrode and the positive electrode. Again, the electrodes preferably have a ball and socket mounting and are spring biased to form the firm engagement with the chest of a patient.
A further modified electrode structure is shown in Fig. 5, the parts which are similar again being identified by similar numerals, this time with the addition of the suffix b. In this instance, the positive electrode 42b is centrally located, and has spaced from it a negative electrode 40b concentric therewith. Outwardly of the negative electrode and also in spaced relation therefrom and concentric therewith is a yet larger ring comprising the indifferent electrode 44b. In FIG. 8 there will be seen a structure similar to that in Fig. 7 for supporting the electrodes of FIG. 5, only the support for the outer ring or indifferent electrode 44b being shown. There are four arcuately spaced shafts or rods 52b supporting the ring 44b, each being outwardly biased by a spring 56b compressed between a stop 58b on the shaft and a fixed stop 60b in the housing. Thus, as in the previous figures, structure is provided for firmly, yet resiliently, and hence comfortably postioning the electrodes against the patient's chest. A somewhat modified electrode display is shown in FIG. 6, this again being a two lead pickup as distinguished from a three lead pickups of FIGS. 3 and 5. The positive pickup in this instance comprises a ring 42c having in spaced, insulated relation thereto and concentrically outwardly therefrom an indifferent electrode 44c. The structure otherwise remains the same.
The pistol grip 30 shown in FIG. 2 is fixed angular relation relative to the case or housing. A modification of the structure is shown in FIG. 9, similar parts being identified by similar numerals with the addition of the suffic d. A handle 30d is mounted on a depending flange 65 by means of a threaded stud 67 having a wing nut 69 thereon. Upon loosening of the wing nut, the handle 30d may be arranged to any desirable or comfortable position, as illustrated by the single solid line and two broken line positions of FIG. 9. Subsequent tightening of the wing nut 69 on the threaded stud 67 locks the handle in the desired adjusted position.
It is intended that for utmost portability and electrical safety, the present apparatus should be battery operated. However, it is contemplated that in some instances it would be desired to use line cord or AC operation. A modification to this end is shown in FIG. 10, similar numerals again being used with the addition of the suffix e. The distinguishing feature of FIG. 10 is that the pistol grip handle 30e is provided with a line cord 70 extending from the lower end thereof, and leading up through the handle into the housing for attachment to a power supply unit to operate the electronic circuits and the cathode ray tube therein.
Due to the small size and light weight of the present apparatus, and also due to the mounting of the electrodes directly thereon and the preferred battery operation, it is a simple matter for a doctor to carry such an apparatus with him, and to take a quick electrocardiographic signal of a patient as routinely as blood pressure and temperature and pulse rate are taken. Since the apparatus can be constructed relatively inexpensively as electronic medical apparatus goes, and since little additional time is required for the taking of the instantaneous electrocardiographic signal, the added cost to the patient for the taking of an electrocardiographic signal along with the measuring of pulse rate, blood pressure, and temperature is of inestimable benefit both to the patient and to the doctor.
The specific examples of the invention as herein shown and described are for illustrative purposes only. Various changes in structure will no doubt occur to those skilled in the art, and will be understood as forming a part of the present invention insofar as they fall within the spirit and scope of the appended claims.