MONITORING APPARATUS WITH AUDIO OUTPUT FREQUENCY RESPONSIVE TO EKG SIGNAL AMPLITUDE

• US 3,565,058 A
• Filed: 10/04/1967
• Issued: 02/23/1971
• Est. Priority Date: 10/04/1967
• Status: Expired due to Term

• Current Assignee: Peter B. Mansfield
• Original Assignee: Peter B. Mansfield
• Inventors: Mansfield, Peter B.
• Application Number:
  US04/672,784
• Time in Patent Office: 1,238 Days
• US Class Current: 600/514
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/305 Common mode rejection
• CPC Class Codes: A61B 5/308 for electrocardiography [ECG]
• CPC Class Codes: A61B 5/486 Bio-feedback A61B5/375 takes precedence
• CPC Class Codes: A61B 5/7415 Sound rendering of measured values, e.g. by pitch or volume variation A61B5/741 takes precedence
• CPC Class Codes: A61B 7/00 Instruments for auscultation

Abstract

An electrocardiograph tone output signal is provided so that the audible frequency of the tone is representative of the amplitude of the EKG signal. The EKG signal is sensed by conventional electrodes, amplified and then modulates the frequency of an audible signal centered about 1,500 cycles so that a positive EKG signal increases the frequency of the audio signal. This frequency-modulated tone is reproduced by a loudspeaker so that the medical personnel may concentrate their eyes on the operation or other medical procedure while continuously monitoring the EKG with their ears. A typical unit provides a frequency deviation of from 100 to 8,000 cycles.

Claims

1. Electrocardiographic apparatus comprising:

means defining an input for receiving an EKG signal from a patient whose condition is to be monitored;

a source of an audio frequency signal;

means responsive to the EKG signal on said input for modulating said audiofrequency signal so that the frequency thereof is representative of the amplitude of the EKG signal at said input;

transducing means for providing an audible tone of frequency corresponding to that of said audiofrequency signal;

means for coupling the modulated audiofrequency signal to said transducing means to provide an audible tone of pitch representative of the EKG signal applied to said input; and

means responsive to the EKG signal on said input for effecting an incremental change in said audiofrequency in response to a prescribed incremental change in EKG signal amplitude that is greater when changing from a first audiofrequency which than when changing from a second audiofrequency which first audiofrequency is greater by at least a predetermined amount than said second audiofrequency.

2. Electrocardiographic apparatus in accordance with claim 1 wherein said means for modulating includes means for varying said audiofrequency over the range from substantially 100 to 8,000 Hz. about a quiescent frequency of substantially 1,500 Hz.

3. Electrocardiographic apparatus in accordance with claim 1 wherein said means responsive to the EKG signal on said input includes a means for attenuating spectral components of the EKG signal above a predetermined frequency which predetermined frequency is below powerline frequency and high enough to pass spectral components meaningful for aural analysis of said EKG signal and said predetermined frequency is within the range of substantially 20-30 Hz.

4. Electrocardiographic apparatus in accordance with claim 1 wherein said source of an audiofrequency signal comprises:

oscillatory circuit means defining a relaxation oscillator;

said oscillatory circuit means including a capacitor whose rate of charging is related to said audiofrequency;

said means for modulating includes modulating circuit means defining a current source for providing a current of amplitude related by a gain factor to that of the EKG signal on said input for charging said capacitor at a rate related to the current amplitude; and

said modulating circuit means including means responsive to the EKG signal amplitude for effecting changes in said gain factor.