ELECTROCARDIOGRAPHY TRANSMITTER AND TRANSMISSION METHOD

• US 3,872,251 A
• Filed: 02/20/1973
• Issued: 03/18/1975
• Est. Priority Date: 02/20/1973
• Status: Expired due to Term

• Current Assignee: Albert A. Auerbach, George M. Katz, Sidney Steinberg
• Original Assignee: Albert A. Auerbach, George M. Katz, Sidney Steinberg
• Inventors: Katz, George M., Auerbach, Albert A., Steinberg, Sidney
• Primary Examiner(s): Cooper, William C.
• Assistant Examiner(s): Brigance, Gerald L.
• Application Number:
  US05/334,078
• Time in Patent Office: 756 Days
• Field of Search: 128/2.6R,2.6B,2.1A 179/2R,2DP,2A,3,4 340/177CA,180,27R
• US Class Current: 379/106.02
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker
• CPC Class Codes: Y10S 128/904 Telephone telemetry

Abstract

Described is a portable, battery-operated electrocardiography (EKG) transmitter, and method of transmission, from the patient'"'"''"'"'s location via telephone lines to a diagnostic central. The transmitter, which includes a '"'"''"'"''"'"''"'"'calibration'"'"''"'"''"'"''"'"'-signal generator for producing a reference signal, an EKG-signal amplifier and a frequency-modulator, operates at a nominal carrier frequency of 1800 HZ. Each (periodic or emergency) transmission commences with a sequence of calibrate-signal square waves at about 5 Hz for about 5 seconds. The calibrate signals modulate the 1800 Hz carrier to produce a 225 Hz deviation and deflect the EKG recording pen at the diagnostic central by 1 cm. The diagnostic central maintains a fixed sensitivity of 1 cm deflection per 225 Hz Delta f as a reference signal for all patients. At the end of the 5 second interval, the calibration signal generation terminates automatically, and then the amplified EKG-signals are switched to modulate the carrier. The reference signal, as penrecorded preceding and juxtaposed to the recorded EKG-signals proper, serves to provide: (1) a convenient visual reference and an accurate calibration marker for the EKG-signal amplitudes, to indicate changes in EKG signals relative to previous transmissions; (2) a basis for discrimination between changes attributable to physiological changes in the patient and changes attributable to aging and drift of transmitter components; (3) a forecast of failure of a patient'"'"''"'"'s pacemaker; (4) early warning of the approach of end of the battery life. However, long battery and low drift are assured by automatic shut-off of the transmitter after operational use thereof for about 90 seconds maximum, and by selection of stable components.

Claims

1. Apparatus for use in transmission of electrocardiographic (EKG) signals derived from a patient, transmission being from the patient'"'"''"'"'s location via a common carrier transmission means to a central location, the apparatus being normally in an inactive state, comprising an amplifier for amplifying the patient-derived EKG signals;

reference signal generating means for generating a reference signal of predetermined amplitude;

a frequency modulator operating at a carrier frequency within the audio range for frequency-modulating the carrrier with input signals to the modulator;

a patient-operable switch momentarily operable for activating the apparatus;

automatically timed switching means responsive to the momentary operation of the patient-operable switch for switching in as input signals to the modulator, the amplified EKG signals such that the amplified EKG signals and the reference signal are timewise juxtaposed;

means for coupling the resultant frequency-modulated signal to the common carrier transmission means;

a shut-off timing signal generator responsive to patient-operable switch for producing a shut-off timing signal having a given duration; and

means responsive to the termination of the shut-off timing signal for automatically shutting off the apparatus to return it to the inactive state.

2. Apparatus as claimed in claim 1, wherein the reference signal generating means comprises means for generating a train of pulses of predetermined amplitude.

3. Apparatus as claimed in claim 2, wherein the reference signal generating means is a square wave generator.

4. Apparatus as claimed in claim 1, wherein the automatically timed switching means first switches-in to the input of the frequency-modulator solely the reference signal, and after the termination of the reference signal switches-in to the input of the frequency-modulator the amplified EKG signals.

5. Apparatus as claimed in claim 4, wherein the common carrier transmission means comprises a telephone set located at the patient'"'"''"'"'s location, and wherein the coupling means includes a loudspeaker driven by the frequency-modulator and acoustically coupled to the mouthpiece of the patient'"'"''"'"'s telephone set.

6. Apparatus as claimed in claim 1, further comprising a battery-type power supply source to which the apparatus proper in its inactive state presents essentially neglibible loading effect, a normally likewise inactive voltage regulator for the apparatus, circuit-connecting means activated by the patient-operable switch for actively connecting the voltage regulator to the power supply source, thereby to activate the voltage regulator and to cause application of regulated voltages to the apparatus proper to place the apparatus proper into its active state, a reference signal timing means responsive to operation of the patient-operable switch to generate a reference signal timing signal of a given duration, thE reference signal generating means being responsive to initiation and to termination of the reference signal timing signal to generate the reference signal solely while the reference signal timing signal persists, said automatically timed switching means also being responsive to, an during persistence of, the reference signal to feed to the input of the frequency-modulator solely the reference signal, and responsive to termination of the reference signal to feed to the input of the frequency-modulator the amplified EKG signals, the circuit-connecting means being responsive to termination of the shut-off timing signal to break the power supply-to-voltage regulator connection, thereby to render once more inactive the apparatus proper.

7. Apparatus as claimed in claim 6, wherein voltage to the reference signal timing means is supplied directly by the power supply source upon operation of the patient-operable switch.

8. Apparatus as claimed in claim 6, wherein power to the circuit-connecting means is supplied directly by the power supply source upon operation of the patient-operable switch.

9. Apparatus as claimed in claim 9, wherein voltage to the circuit-connecting means is supplied as a regulated voiltage from the voltage regulator.

10. Apparatus as claimed in claim 1, further comprising a clamping circuit connected to the input of the frequency modulator for clamping such input signals to the frequency modulator, as would otherwise be of excessive amplitudes, to fixed maximum amplitudes.

11. Apparatus as claimed in claim 10, wherein the clamping circuit is arranged to clamp the otherwise excessive amplitude input signals to both positive and negative fixed maximum amplitudes.

12. Apparatus as claimed in claim 1, wherein there is provided, preceding the amplifier, a patient-operable switching unit for switching in to the amplifier patient-derived electrocardiography signals which correspond to the desired one of the plurality of standard electrocardiography electrode-connection-modes.

13. Apparatus as claimed in claim 1, wherein the amplifier comprises plural stages, and wherein in at least one stage there is provided a diode-shunting circuit effective to alter a time-constant of such stage for excessive amplitudes of signals passing through such stage, whereby to suppress undesired transient signals.