Electrocardiograph telemetry system including method and means for indicating inoperative conditions

• US 3,953,848 A
• Filed: 04/12/1974
• Issued: 04/27/1976
• Est. Priority Date: 06/25/1973
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Larsen, James L., Dillman, Richard F., Nardizzi, Alfred M.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Groody, James J.
• Application Number:
  US05/460,629
• Time in Patent Office: 746 Days
• Field of Search: 340/180, 340/181, 340/186, 340/409, 340/207 R, 340/208, 340/177 CA, 340/279, 340/253 Y, 324/58 A, 128/2.05 R, 128/2.06 R, 128/2.1 A
• US Class Current: 340/870.09
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

Special circuitry in the transmitter of an electrocardiograph (ECG) telemetry system detects various malfunctions of the system and changes the transmitted signal to indicate their presence to the system receiver. When the transmitter detects that an input electrode has become detached from the patient, it changes the frequency of the subcarrier signal to indicate this problem to the receiver. The receiver monitors the subcarrier frequency and flashes an alarm light when the frequency corresponds to the electrode inoperative condition.

Claims

1. In an electrocardiac telemetry system having a receiver and a transmitter which transmits to the receiver a carrier signal that is modulated by a subcarrier that is modulated by electrocardiac signals applied to the transmitter from electrodes that are attached to a patient, apparatus for producing an indication that an electrode is detached from the patient comprises:

circuit means in the transmitter coupled to the electrodes for producing a control signal in response to the open circuit condition of an electrode detached from a patient;

a signal-controlled source of subcarrier signal in the transmitter having first and second subcarrier operating frequencies;

means coupled to said source for applying electrocardiac signals thereto to modulate the operating frequency thereof about the first subcarrier frequency in response to applied electrocardiac signal;

means coupling said circuit means to said source for altering the operating frequency thereof to the second subcarrier frequency in response to control signal applied thereto from said circuit means;

carrier signal generating means coupled to said source for transmitting a carrier signal modulated by said subcarrier signal;

receiver means including a detector responsive to transmitted carrier signal modulated at said second subcarrier frequency received by the receiver means for producing an output that is indicative of electrode detachment from a patient.

2. In an electrocardiac telemetry system having a receiver and a transmitter which transmits to the receiver a carrier signal that is modulated by a subcarrier that is modulated by electrocardiac signals applied to the transmitter from electrodes that are attached to a patient, the method of producing an indication that an electrode is detached from the patient, comprising the steps of:

detecting the open circuit condition of an electrode detached from a patient;

altering the frequency of the subcarrier in the transmitter form one frequency to another frequency in response to detection of a detached electrode;

sensing the altered subcarrier frequency at the receiver; and

providing an indication of inoperative condition in response to the altered subcarrier frequency received at the receiver.