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Cardiac patient remote monitoring using multiple tone frequencies from central station to control functions of local instrument at patient's home

  • US 5,467,773 A
  • Filed: 05/21/1993
  • Issued: 11/21/1995
  • Est. Priority Date: 05/21/1993
  • Status: Expired due to Term
First Claim
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1. A cardiac patient follow up system comprising a local instrument having ECG lead inputs for connection to ECG electrodes coupled with a patient and further having telephone line inputs for connection with a central instrument through a telephone network utilizing dual tone multifrequency signals for dialing, said local instrument comprising:

  • a local telephone set for establishing a two-way telephone connection with said central instrument through a telephone line and telephone network, said local telephone set having a telephone circuit including a speaker for converting a voice signal received over said telephone line to a sound signal and a microphone converting a sound signal received at the microphone into a signal for transmission over said telephone line and network; and

    a local dual tone multifrequency decoder responsive to dual tone multifrequency signals received over said telephone line to generate respective local command signals;

    a patient monitoring portion coupled to said telephone set, said patient monitoring portion including;

    an amplifier coupled with said inputs for ECG leads to amplify signals received thereat;

    an ECG filter and a pulse filter each coupled with the amplifier to receive signals amplified thereby, said ECG filter comprising circuitry tending to pass ECG signals while suppressing pulse signals corresponding to cardiac pacemaker pulses, and said pulse filter comprising circuitry tending to pass pulse signals corresponding to cardiac pacemaker pulses while suppressing ECG signals;

    a pulse detector coupled with said pulse filter to detect leading and trailing edges of pulses passed thereby and to generate in response relatively short pulses signifying said leading and trailing edges;

    a pulse width encoder coupled with said pulse detector and, when enabled by a respective local command, responding to each pair of said short pulses corresponding to a pacemaker pulse to generate a respective pulse width encoded signal;

    a fixed pulse encoder coupled with said pulse detector and, when enabled by a respective local command, responding to each pair of said short pulses corresponding to a pacemaker pulse to generate a respective fixed width pulse;

    an FM encoder coupled with said pulse width encoder and said fixed pulse encoder and, when enabled by a respective local command, receiving said pulse width encoded signal and said fixed width pulse therefrom and encoding said pulse width encoded signal and said fixed width pulse into an FM signal having a specified center frequency and deviations therefrom corresponding to parameters of said pulse width encoded signal and said fixed width pulse for transmission over said telephone line and network to said central instrument;

    a patient alert indicator displaying at least one message for a patient using said local instrument;

    a logic control circuit coupled with said local dual tone multifrequency decoder and responsive to said local command signals therefrom to generate respective local commands for selectively enabling said FM encoder, pulse encoder, pulse width encoder, and patient alert indicator; and

    an isolation stage connecting said FM encoder and said logic control circuit with said telephone circuit to pass information therebetween while suppressing electrical interaction therebetween.

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