US 3902478 A
A disaster alarm consisting of the combination of a small cardiac monitor, switching and signal coder controlling a transmitter which is actuated when high or low levels of a function such as heart rate are exceeded. The signal is picked up by a receiver which in turn is connected to an alarm system which continues to operate due to self-latching circuits until re-set.
Description (OCR text may contain errors)
United States Patent 11 1 Kono asek et al. Se t. 2 1975 P P a DISASTER ALARM 3,646,930 3/1972 Patterson et a1 128/2.1 A 3,774,594 11 1973 H 128 2.1 A  Inventors: Francis Konopasek, 83 Laval Dr.; uszav Thomas Edward Cuddy, 1 Paradise I Bay; Monte Raber, 83 Coralberry Przmary Examzner-Wflham E. Kamm Ave. Bryan William Kirk 229 Attorney, Agent, or Firm-Stanley G. Ade Lamont Blvd., all of Winnipeg, Manitoba, Canada 5 ABSTRACT Filed: 1973 A disaster alarm consisting of the combination of a  APPL NO; 414,390 small cardiac monitor, switching and signal coder controlling a transmitter which is actuated when high or Related pp Data low levels of a function such as heart rate are ex-  Continuation-impart of Ser. No. 104,673, Jan. 7, ceeded. The si nal is picked up by a receiver which in g 1971, abandoned. turn is connected to an alarm system which continues  U S Cl 128/2 06 128/2 1 A to operate due to self-latching circuits until re-set,  Int. Cl. A61B 5/04 TWO embodiments r ho n on in whi h alarm  Field of Sear h 128/205 R, 2,06 A, 206 F signals only are transmitted in a pulsed or continuous 128/206 R 2 1 A fashion rather than the cardiac signal; and the other which operates in a fail-safe mode which not only  References Cited transmits an alarm signal when necessary, but UNITED STATES PATENTS periodically transmits an operating signal, the absence 2,684,278 7/1954 Marchand 128 206 B g s zli f g i g g gr s i l 3,426,150 2/1969 Tygavt 128/2.1 A 6 SY "I a no 1 S n g a 3,517,662 6/1970 Finch et a1. l28/2.06 B wammg 3,572,316 3/l97l Vogelman et al.. l28/2.l A 3,613,670 10/1971 Edenhofer 128/206 F 2 Claims, 7 Drawing Figures PATIENT 32A ROOM UNITS REOEIVERB GENTRAL I4 LocAL CONSOLE i MR |Q I REMOTE ALARM ll I3 IO 32A l2 32 36 IO i II 32A PATENTED 3E? ,2 75
SHEET 1 OF 5 32A :ggavms a we consouz \L 5 ALARM 5 REM" ALARM u T I2 3ZA 5 Y .H n
INVENTOR F2400: Aawe fllree 72mm: fauna C0100)! I70":- 4? E489? Aldrin Maud-q 47 BACKGROUND OF THE INVENTION This invention relates to new and useful improvements in cardiac disaster alarms. 1
Patients with acute myocardial infarction are routinely kept under observation in a coronary care unit and monitored for the first 72 hours when the incidence of potentially fatal arrhythmias is greatest. Then the patients are transferred to a regular medical ward for 14 to 21 days. However, they cannot'be kept under constant observation while on a regular ward an'it is found that a small but disturbing number of these patients die suddenly and unexpectedly, presumably due to undetected fatal arrhythias. Irrespective of the cause of an arrhythia, lives can be saved if the staff could be warned of a cardiac catastrophe when it occurs, and so immediately incur resuscitation. I
Cardiac monitors in current use are relatively large, and require specially trained staff since they are designed for constant visual observation. Such equipment is useless on a regular ward since the ordinary ward staff are not trained in their use. Further, the entire ECG is continuously transmitted. A simple type of monitor is needed for this use to immediately warn of trouble by giving an alarm if the heart rate is too slow or too fast. The Cardiac Disaster Alarm has been devised to fulfill this need.
SUMMARY OF THE INVENTION The cardiac disaster alarm is a small, portable instrument, worn by a patient,-which senses the hearts activity and transmits an alarm signal if the patients heart rate deviates beyond preset limits. In additionto the alarm signal, the instrument can also be made so asto transmit an Operating OK. which provides'a check on the operation of the entire monitor-alarm system, and, in another embodiment, this O.K'. signal could be coded so as to transmit the value of the patients heart rate.
This device will give an alarm should the heart rate become too high or too low (tachycardia and brachycardia respectively), the particular rates at which the alarm is triggered may be set to the needs of each individual patient. The alarm can also identify the patient and give his location'so that the necessary action may be taken. l
A pulsed, codedalarm signal can "be transmittedor a periodic coded Operating O.K. signal can be trans mitted. The bandwidth "and signal handling requirements are greatly reduced over alternate methods which transmit the electrocardiogram on a continuous basis. This method uses much less power than usual telemetry. V v I With the considerations and inventive objectsherein set forth in view, and such other or further purposes,.
advantages or novel'features as. may become apparent from consideration of this disclosure and specification, the present invention consists of the iriventiveiconcept DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of one embodiment of the invention.
FIG. 2 is a schematic diagram of a suitable circuit for the patient unit. I
FIG. 3 is a schematic diagram of a suitable circuit for the room receiver transmitter.
DETAILED DESCRIPTION Referring now to the drawings by reference characters, there is shown in FIG. 1 the layout of the nonfailsafe system. Carried by either ambulatory or stationary patients are the patient units 10, described in detail below, whichare, of vest pocket size. Should the heart rate of apatient reach a predetermined alarm condition, a small transmitter in the unit is switched on automatically. The waveform of the output of this transmitter is modulated in a mannercharacrteristic of that particular patient (though patients served by different room'units may have transmitters with the same modulation). This signal is sent through the room to a room receiver 11, which may actuate a local alarm 12. Alternatively, under favourable transmission conditions, this signal could go directly to the central station. The room receiver unit-then changes the carrier frequency to one suitable for sending throughout the building either by power supply mains, hard wire connections or telemetry. The characteristic modulating waveform remains unaltered by this process. The room receiver units in eachward may send out a different carrier frequency which will serve to identify thelocation of the patient. When the central console 13, picks up this frequency an alarm, 14 is sounded and from the information re-.
ceived, the patient and his location is automatically identified; Alternatively, the receiver may be incorporated in the central station or alarm circuits may be in- Y corporated in the room receiver.
which is comprised, embodied, embraced or included I 1 in the method, process, construction,,composition, arrangement or combination of parts, or new use of any of the foregoing, herein exemplified in one or more specific embodiments of such concept. reference being had to the accompanying Figures in which:
FIG. 2 is a schematic diagram showing a suitable conventional circuit vfor the patient unit. The important sections of the circuit shown are 15, balanced input to dual differential amplifiers; 16, waveform filters; 17, trigger level setting; 18, monostable circuit; 19, an integrator; 20, upper and lower level detectors; 21, power supply gate; 22, tone oscillator; 23, radio frequency oscillator; 24, R.F. modulator; and 25, RF. amplifier.
The device operates in the following manner:
Electrodes 27 are connected to the patient as for an electrocardiogram. The output from the first stage therefore, at 28, is the voltage waveform developed across the heart, plus some interfering signals which are weaker than the desired signal pulse due to filtering action. I
With each input pulse the monostable circuit gives a fixed voltage outputfor a pre-set length of time, before dropping back to zero. Interfering signals as well as the desired ones may trigger this circuit, and to prevent this happening, a trigger level setting device 29 may be adjusted so that only the strongest signals operate the monostable circuit. A fast heart rate gives a greater mark to space ratio in the rectangular-wave output than a slow one. When these pulses are fed into the integrator, the steady output voltage is higher, the faster the heart rate. This is developed at 30 and then fed into upper and lower level detectors.
Should the voltage level at 30 reach certain pre-set upper or lower limits, the power supply gate will be closed and the transmitter made operative. The upper and lower level detactors may be adjusted by means of variable resistors 31 and 32 so that alarm is transmitted when certain heart rates are reached, these limits being determined by the condition of each individual patient. Alternatively, these may be pre-set and, for simplicity, these fixed alarm settings are preferred.
Under normal conditions, all the stages after the power supply gate are inoperative, ensuring economic -battery usage. When an alarm condition is reached, the
power supply gate is closed and the final stages are made operative. The transmitter may be made to operate in a pulsed fashion, if desired, to increase range and conserve power. The tone oscillator A, radio frequency oscillator B, modulator C and amplifier D, all function in the normal manner. The modulating signal is made different for each patient unit in a particular ward. The modulated wave is then transmitted from the portable antenna 32A to be picked up by the room receivers.
FIG. 3 is a schematic diagram showing a suitable conventional circuit for the room receiver.
As this device operates in a conventional way, only a brief description will be entered into here. The signal from the patient unit is received on an antenna 36, and amplified as at 37. This is then fed into the mixer 38, where it is mixed with another frequency produced by the oscillator 39, the difference in frequency being the intermediate frequency. The room receivers in each ward may have a different intermediate frequency or other indentifying characteristics. This signal is picked out and amplified. It is modulated by the waveform characteristic of the patient whose alarm is operative.
By means of the tuned circuits at point 33 this signal is fed into the power supply mains or other communicating link, through which it is conducted to the central console. An automatic gain control cirucit 40, is also included so that the circuits are not overloaded by strong signals. Reference character 41 indicates an LP. amplifier circuit and 42 the IF. power amplifier circuit.
FIG. 4 is a schematic diagram showing a suitable circuit for the central console. The important sections of the circuit shown are (1) radio frequency amplifiers (2) tone frequency (audio frequency) amplifier and filter 44 (3) automatic gain control 45 and (4) self latching alarm system 46.
The device shown here is only capable of receiving one intermediate frequency, though only minor modifications are needed to take more. It operates in the following manner:
The desired signals are removed from the mains by tuned circuits at point 34. These signals are then amplified in several stages, automatic gain control being applied to one of them. The modulating audio frequency is detected and amplified.
This signal is then fed into resonant circuits corresponding to the various modulation waveforms of the different patient units. Only the one that corresponds to the signal being received will be activated, and this will then set off an alarm. An advantage of the circuit shown is that it is self latching, i.e. regardless of the signals received the alarm 35 will sound until re-set by a push button 35 or the like.
Semi-conductor types, component values and apparatus designations are given solely by way of example, and not in a limiting sense. The invention is not limited solely to sending an alarm for heart rates, this being given as an example. The system is capable of giving a warning of many abnormalities, e.g. biological processes, blood pressure, temperature, malfunction of the equipment and the like. While tone-modulated coding is used in this example, digital coded signals (pulses) could also be used.
Summarizing, our device is capable of signal processing at the source, transmission of coded alarm signals, transmission via remote receiver transmitters to central monitor or identifying the location of a malfunction or disaster as well as identification of the malfunction or disaster.
FIG. 5 shows a schematic block diagram of the nonfail-safe version in which the amplifier is indicated by 15 and includes a rate meter 47 which in turn is connected to alarm limit circuitry 48 as hereinbefore described. The transmitter control 49 operates transmitter 56 and receiver 13 operates alarm circuits 14. In FIG. 5, corresponding reference characters of the previous embodiments are shown in parenthesis.
In this embodiment, only alarm signals are transmitted as hereinbefore described.
FIGS. 6 and 7 show schematic block diagrams of preferred embodiments and dealing first with FIG. 6, the amplifier 15, rate meter 47, and alarm limit circuits 48 are similar to those shown in FIG. 5. An alarm modulator 50 connects to the transmitter control 49 which operates the transmitter 56 and receiver 13 feeds to decoding circuits 31 which in turn are connected to an operating indicator 52 for locating the source of the signal and to alarm signals 14. Corresponding reference characters of the previous embodiments are shown in parenthesis.
An operating signal and modulator circuit shown by reference character 53 connects to the transmitter control and is adapted to periodically transmit an operating signal thus allowing the operator to check on the fact that the circuit is in operating condition. When an alarm is triggered, then of course the circuit operates in a manner similar to that hereinbefore described. A similar or different kind of alarm will be sounded if the decoding circuits (51) do not sense the periodic Operating" signal (53).
FIG. 7 shows a modification in which the amplifier 15 and rate meter 47 are similar to those hereinbefore described. A sampler and modulator circuit 54 connects to the transmitter control 49 and hence to the transmitter 56 with the receiver 13 being connected to a location indicator 52 and to a rate meter with alarm shown by reference character 55. This particular version periodically transmits rate data so that a continuous monitoring can be kept on the patient and at the same time of course if the high or low levels that have been preset, are exceeded, then the alarm signals will also Show. Also cessation of the coded rate data will cause an alarm.
The basic differencebetween the present invention and previous types of electrocardiographic monitors is that in the present device, pulsed signals are transmitted, while in ordinary telemetry the entire ECG is con tinuously transmitted. The present device has the advantage that the signals are easier to handle in this form so that it should be significantly less expensive than existing apparatus.
As mentioned previously, the invention can take two forms, either fail-safe or nonfail-safe. The simplest form shown schematically in FIGS. 1 to 5 inclusive, is nonfail-safe. In this form, the monitor senses the heart rate in the patient-transmitter but only broadcasts an alarm signal. Therefore there is no assurance that the system is working and capable of an alarm but it is the least expensive approach so far as the receiver is concerned.
The fail-safe versions will automatically monitor the operation of the patient-transmitter and sound an alarm if the system malfunctions, as well as if the heart rate limits are exceeded. The two methods described and shown in FIGS. 6 and 7 can be used to implement this version.
The first method shown in FIG. 6 indicates that the patient-transmitter can broadcast an intermittent operating signal in addition to the alarm signal. The absence of several operating pulses would then be an alarm condition showing malfunction of the device.
In FIG. 7, instead of a simple operating signal, the patient-transmitter periodically transmits coded pulses representing the heart rate and the rate alarm circuitry may be located at the receiver. This coded, intermittent rate signal may serve the same purpose as the operating signal described in reference to FIG. 6.
By appropriate coding, either type of pulsed signal can of course be used to identify and locate the patient.
In any version of the disaster alarm hereinbefore described, because the heart rate is computed in the patient unit the transmitted signal can be intermittent or pulsed, and can be coded for ease of handling and identification.
This provides a distinct advantage over prior methods which required the continuous high-fidelity transmission of the ECG to the receiver/rate meter.
Since various modifications can be made in our invention as hereinabove described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.
What we claim is our invention:
1. A cardiac disaster alarm system for use with a central alarm console comprising in combination at least one portable unit, each unit including a transmitter having a source of power, circuits which may be operatively connected to a ptient for monitoring cardiac function, means for actuating said transmitter to transmit coded alarm signals when predetermined high or low levels of said cardiac function are exceeded, a receiver within radio ran ge of said transmitter operatively connected to the associated central alarm console, said alarm being connected to said alarm console, means in said receiver for decoding the alarm signals and causing said alarm signals are received, means for controlling and turning off said alarm, said console and receiver also including means to identify the location transmitting the alarrn by the coding of the transmitted signal, means for transmitting, receiving and decoding an intermittent Operating signal for automatically checking the operation of said system, and means in said re ceiver for operating said alarm when said intermittent Operating signal is absent.
2. A cardiac disaster alarm system for use with a central alarm console comprising in combination at least one portable unit, each unit including a transmitter having a source of power, circuits which may be operatively connected to a patient for monitoring cardiac function, means for actuating said transmitter to transmit coded alarm signals when predetermined high or low levels of said cardiac function are exceeded, a receiver within radio range of said transmitter operatively connected to the associated central alarm console, said alarm being connected to said alarm console, means in said receiver for decoding the alarm signals and causing said alarm to indicate when said alarm signals are received, means for controlling and turning off said alarm, said console and receiver also including means to identify the location transmitting the alarm by the coding of the transmitted signal, and means for periodically transmitting, receiving and decoding coded pulses representing the heart rate of the patient being monitored, the periodicity of said coded pulses automatically checking the operation of said system, and means in said receiver for operating said alarm when said coded pulses are absent.
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