Monitoring myoelectric signals

• US 4,213,466 A
• Filed: 08/11/1978
• Issued: 07/22/1980
• Est. Priority Date: 08/11/1978
• Status: Expired due to Term

• Current Assignee: Children's Medical Center Corporation
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Inventors: Stulen, Foster B.
• Primary Examiner(s): Michell, Robert W.
• Assistant Examiner(s): Jaworski, Francis J.
• Application Number:
  US05/933,071
• Time in Patent Office: 711 Days
• Field of Search: 128/733, 307/233 R, 324/78 F, 328/167, 330/109
• US Class Current: 600/546
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• CPC Class Codes: A61B 5/397 Analysis of electromyograms

Abstract

A muscle fatigue monitor featuring detecting a myoelectric signal and providing a first output signal representative of said myoelectric signal, producing a second output signal corresponding to a portion of said first output signal having components in a selected frequency band, providing a control signal corresponding to the difference in magnitude between said output signals, varying the magnitude of said second signal in accordance with the value of said control signal, and displaying the variation in the frequency spectrum of said myoelectric signal as a function of time.

Claims

1. In a neurological monitor for measuring the spectral variation in a myoelectric signal, said monitor being of the type including

an electrode suitable for contacting a living being and detecting said myoelectric signal,

circuitry for processing said myoelectrical signal to provide a display signal representative of said spectral variation, said circuitry comprising

means for amplifying said myoelectric signal to provide an amplified signal,

filter means for providing a filtered signal corresponding to a portion of said amplified signal having frequency components on one side of a variable cutoff frequency,

means for comparing said filtered signal to a reference signal and providing a control signal that is dependent on the difference in magnitude between said filtered and reference signals,

means for automatically varying said cutoff frequency in accordance with the value of said control signal,

means for providing a display signal representitive of said spectral variation in said myoelectric signal, and

a display driven by said display signal, for observing said spectral variation in said myoelectric signal,

the improvement comprising an attenuator for receiving said amplified signal and producing said reference signal, the attenuation being selected to make the magnitudes of said reference and filtered signals equal when said cutoff frequency is set at a median frequency of said myoelectric signal,

whereby said circuitry will tend to adjust said cutoff frequency to said median frequency.