Method and an apparatus for use in electromyography to determine risk of muscular disorder

• US 5,645,073 A
• Filed: 06/07/1994
• Issued: 07/08/1997
• Est. Priority Date: 07/31/1989
• Status: Expired due to Fees

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Synectics Medical AB (Medtronic Plc)
• Inventors: Oberg, Tommy, Kadefors, Roland, Sandsjo, Leif
• Primary Examiner(s): Sykes, Angela D.
• Application Number:
  US08/255,256
• Time in Patent Office: 1,127 Days
• Field of Search: 128/696, 128/706, 128/731-3, 128/781-2, 128/774, 128/905
• US Class Current: 600/546
• CPC Class Codes: A61B 5/389 Electromyography [EMG]

Abstract

The invention relates to a method and an apparatus for detecting muscular status. The apparatus includes an electrode (7) for taking up analog myoelectric signals, an amplifier (1) which is followed by an A/D converter to which is connected a signal processing unit (3). A signal (4) is connected to the signal processing unit.

The analog signals collected by the electrode (7) are converted, after amplification, into binary signals which are analyzed in the signal processing unit (3). This calculates the occurrences of muscle activity below a certain muscle activity level related to an initial muscle activity determined on commencement of the detection. Signals relating to the occurrences of muscle activities below said level are emitted from the signal (4) or stored in a storage device.

Claims

1. A method for detecting, over a period of time, muscular status to determine risk of muscular disorder, said method comprising producing analog myoelectric signals in response to activity of a muscle under examination, amplifying said signals to produce amplified signals, converting the amplified signals into digital signals, in successive calculation periods, producing from said digital signals a signal which characterizes myoelectric signals during each calculation period, comparing the signals which characterize the myoelectric signals to a base signal related to the frequency spectrum sensed on commencement of said period of time of detection, producing output signals based on said comparing to represent muscular status for enabling detection of risk of muscle disorder based on the occurrences of intervals during which the muscle activity is below a predetermined level and transforming said output signals representing muscular status into a state perceivable by a human being.

2. The method of detecting muscular status as claimed in claim 1 comprising selecting the predetermined level to correspond substantially to the level of a relaxed muscle.

3. The method of detecting muscular status as claimed in claim 2 comprising detecting the muscular status of a substantially relaxed muscle based on the shift of a mean frequency of the frequency spectrum of the myoelectric signal until a predetermined location.

4. The method of detecting muscular status as claimed in claim 3 comprising detecting the muscular status of a substantially relaxed muscle based on the absence of shift of said frequency spectrums.

5. The method of detecting muscular status as claimed in claim 1, comprising storing the digital signals representing the myoelectric signals and said output signals in a memory.

6. The method of detecting muscular status as claimed in claim 1, comprising storing said output signals in a memory.

7. The method of detecting muscular status as claimed in claim 1, comprising producing a signal when any detection of the risk of muscle disorder is made thereby to signal risk of disorder.

8. The method of detecting muscular status as claimed in claim 1 wherein said output signals are transformed into the state perceivable to a human being, at least one of an optical, acoustical and tactile signal.

9. The method of detecting muscular status as claimed in claim 8 comprising forming said output signals with one of an amplitude and frequency which is switched on or of, or varies with the risk of muscle disorder.

10. The method of detecting muscular status as claimed in claim 1 calculating during a specific period of time the number of occurrences or the added duration of muscle activity being below the predetermined level.

11. The method of detecting muscular status as claimed in claim 1 comprising storing in a memory the number of occurrences or the added duration of muscle activity being below the predetermined level during a specific period of time.

12. An apparatus for detecting muscular status to determine risk of muscular disorder comprising electrode means for producing analog myoelectric signals related to muscular activity of a muscle of a subject under examination, amplifier means for amplifying said signals, A/D converter means connected to said amplifier means for converting said analog signals into digital signals, signal processing means connected to said A/D converter means for receiving signals therefrom and forming intermediate signals at periodic intervals related to the occurrences of intervals during which the muscle activity is below a predetermined level, the apparatus including means for detecting, at said periodic intervals, occurrences of intervals with the muscle activity below the predetermined level, means for emitting, during each said periodic interval, at least one signal representing muscular status of the muscle under examination based on said occurrences of intervals with the muscle activity below the predetermined level and for producing an output to indicate risk of muscle disorder if the distribution and duration of muscle activity below the predetermined value are beyond predetermined limits, storing means for storage at least temporary of the signals representing the myoelectric signals produced by the electrode means, signal means for transforming said signals representing muscular status into information which is perceivable by a human being, and means for connecting at least one of said storing means and said signal means to said signal processing means.

13. The apparatus as claimed in claim 12 wherein said information from said signal means comprises a signal which is at least one of optical, acoustic, and tactile signals.

14. The apparatus as claimed in claim 12 wherein said signal means produces signals having a characteristic related to the shift of a frequency spectrum within a predetermined range for the signals produced by the electrode means.

15. The apparatus as claimed in claim 14 wherein the characteristic of the signals produced by the signal means is at least one of amplitude and frequency.

16. The apparatus as claimed in claim 12 wherein said means for detecting the occurrences of intervals with the muscle activity below the predetermined level is included in said signal processing means.

17. The apparatus as claimed in claim 12 wherein said communication and control unit includes said means for detecting the occurrences of intervals with the muscle activity below the predetermined level.

18. The apparatus as claimed in claim 12 wherein said signal means produces signals having a characteristic related to the distribution and duration of intervals without any shift of the frequency spectrum for the signals produced by the electrode means.

19. The apparatus as claimed in claim 12 wherein the apparatus includes means for transforming the signals produced by the electrode means to signals representing the muscle activity e.g. averaged rectified signals or root mean squared signals.

20. The apparatus as claimed in claim 12 wherein said means for transforming the myoelectric signals to signals representing the EMG signals is disposed to supply the signals to the A/D converter means.

21. The apparatus as claimed in claim 12 wherein the apparatus includes filtering means for restricting the range of frequencies supplied to the means for transforming the myoelectric signals to the signals representing the EMG signals.

22. The apparatus as claimed in claim 12 wherein the apparatus is including filtering means for restricting the range of frequencies supplied to the A/D converter.

23. The apparatus as claimed in claim 12 wherein said signal means includes means for converting electrical signals to acoustical, optical or tactile signals.

24. The apparatus as claimed in claim 12 comprising a control and communication means interconnected between said signal processing means and said signal means.

25. The apparatus as claimed in claim 24 wherein said control and communication means emits signals which are at least one of analog and digital.

26. The apparatus as claimed in claim 24 wherein said control and communication means supplies control signals to said signal means for activating said signal means or adjusting, at least one of the frequency and amplitude of the signals produced by said signal means.

27. The apparatus as claimed in claim 12 comprising control and communication means connected to said signal processing means and including said signal means.

28. The apparatus as claimed in claim 12 wherein said signal means produces signals having amplitude and frequency, at least one of which is changed when the mean frequency of the frequency spectrum of the signals produced by the electrode means is shifted beyond a predetermined location.

29. The apparatus as claimed in claim 12 wherein said signal means produces signals having amplitude and frequency, at least one of which is changed when the distribution and duration of intervals without any shift of the frequency spectrum pass predetermined limits.

30. The apparatus as claimed in claim 12 wherein said signal means produces signals having amplitude and frequency, at least one of which is changed when the distribution and duration of intervals with muscle activity below the predetermined values pass predetermined limits.

31. The apparatus as claimed in claim 12 wherein said signal processing means supplies control signals to said signal means for activating said signal means or adjusting at least one of the frequency and amplitude of the signals produced by said signal means.

32. The apparatus as claimed in claim 12 wherein said storing means stores digital information relating to the muscle activity represented by the myoelectric signals produced by the electrode means, said storing means being separable from the apparatus.

33. The apparatus as claimed in claim 12, comprising means for establishing a threshold for said predetermined value of the change of frequency spectrum derived from the muscle activity measured during the calibration period.