Method and apparatus for producing a model EMG signal from a measured EMG signal

• US 6,411,843 B1
• Filed: 05/09/2000
• Issued: 06/25/2002
• Est. Priority Date: 05/28/1999
• Status: Expired due to Term

• Current Assignee: RIC INVESTMENTS LLC (Respironics Incorporated)
• Original Assignee: Respironics Incorporated
• Inventors: Zarychta, Jaroslaw
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Application Number:
  US09/567,795
• Time in Patent Office: 777 Days
• Field of Search: 128/203.14, 128/204.23, 600/546, 600/513
• US Class Current: 600/546
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 2210/1014 Diaphragm
• CPC Class Codes: A61M 2230/04 Heartbeat characteristics, e.g. ECG, blood pressure modulation
• CPC Class Codes: A61M 2230/08 Other bio-electrical signals
• CPC Class Codes: A61M 2230/60 Muscle strain, i.e. measured on the user

Abstract

A model EMG signal is produced from a measured EMG signal that includes a patient'"'"'s EMG signal and ECG signal by processing the measured EMG signal to produce a logic signal that is in a first binary state in the absence of a P wave, a QRS complex and a T wave of an ECG cycle of the measured EMG signal and that is in a second binary state during at least one of the P wave, the QRS complex and the T wave of the ECG cycle. The measured EMG signal is processed to produce a first envelope signal. The model EMG signal is produced as a function of the first envelope signal when the logic signal is in the first binary state and the absence of the first envelope signal when the logic signal is in the second binary state.

Claims

1. A method of producing a model EMG signal from a measured EMG signal, wherein the measured EMG signal includes a patient'"'"'s EMG signal and an ECG signal, the method comprising the steps of:

(a) processing a measured EMG signal to produce a logic signal that is (1) in a first binary state responsive to an absence of a P wave, a QRS complex and a T wave in a measured EMG signal and (2) in a second binary state responsive to a presence of at least one of the P wave, the QRS complex, and the T wave in the measured EMG signal;

(b) processing the measured EMG signal to produce a current first envelope signal; and

(c) producing a model EMG signal as a function of (1) the current first envelope signal responsive to the logic signal being in the first binary state and (2) a signal other than the current first envelope signal responsive to the logic signal being in the second binary state.

2. The method as set forth in claim 1, wherein step (a) comprises:

processing the measured EMG signal to produce a second envelope signal;

processing the second envelope signal to produce a fast signal;

processing the second envelope signal to produce a first slow signal having a slew rate slower than a slew rate of the fast signal; and

processing the fast signal and the first slow signal to produce the logic signal.

3. The method as set forth in claim 1, wherein step (b) comprises the steps of:

high pass filtering the measured EMG signal to produce a high pass signal;

rectifying the first high pass signal to produce a rectified signal; and

low pass filtering the rectified signal to produce the first envelope signal.

4. The method as set forth in claim 1, wherein step (c) comprises the steps of:

providing, responsive to the logic signal being in the first binary state, a moving average of the current first envelope signal; and

providing, responsive to the logic signal being in the second binary state, a set value that corresponds to a value of the moving average of the first envelope signal existing when the logic signal changed from the first binary state to the second binary state.

5. The method as set forth in claim 2, wherein the step of processing the measured EMG signal to produce the second envelope signal includes:

low pass filtering the measured EMG signal to produce a first filtered signal, and

rectifying the first filtered signal to produce the second envelope signal;

wherein the step of processing the second envelope signal to produce the fast signal includes;

low pass filtering the second envelope signal to produce a second filtered signal,

amplifying the second filtered signal to produce a first amplified signal,

low pass filtering the first amplified signal to produce a third filtered signal, and

combining the second filtered signal and the third filtered signal to produce the fast signal;

wherein the step of processing the second envelope signal to produce the first slow signal includes;

amplifying the second envelope signal to produce a second amplified signal, and

low pass filtering the second amplified signal to produce the first slow signal; and

wherein the step of processing the fast signal and the first slow signal to produce the logic signal includes comparing the fast signal and the first slow signal to produce, as a function of the comparison, the logic signal.

6. The method as set forth in claim 2, further comprising:

processing the second envelope signal to produce a second slow signal having a slew rate slower than the slew rate of the fast signal; and

processing the fast signal, the first slow signal, and the second slow signal to produce the logic signal.

7. The method as set forth in claim 6, wherein the step of processing the fast signal, the first slow signal and the second slow signal to produce the logic signal includes:

comparing the fast signal and the first slow signal to produce a first comparator signal;

comparing the fast signal and the second slow signal to produce a second comparator signal; and

combining the first comparator signal and the second comparator signal to produce the logic signal.

8. The method as set forth in claim 2, wherein step (b) includes continuously processing the EMG signal to produce a third envelope signal;

and wherein step (c) includes;

providing, responsive to the logic signal being in the first binary state, a moving average of the current first envelope signal, and

providing, responsive to the logic signal being in the second binary state, a moving average of the third envelope signal.

9. The method as set forth in claim 8, wherein the step of processing the measured EMG signal to produce a first envelope signal includes:

high pass filtering the measured EMG signal to produce a first high pass signal,

rectifying the first high pass signal to produce a first rectified signal, and

low pass filtering the first rectified signal to produce the first envelope signal; and

wherein the step of continuously processing the measured EMG signal to produce a third envelope signal includes;

high pass filtering the measured EMG signal to produce a second high pass signal,

rectifying the second high pass signal to produce a second rectified signal, and

low pass filtering the second rectified signal to produce the third envelope signal.

10. The method as set forth in claim 1, further including at least one of:

filtering the measured EMG signal prior to processing the measured EMG signal in at least one of steps (a) and (b); and

amplifying the measured EMG signal prior to processing the measured EMG signal in at least one of steps (a) and (b).

11. An apparatus for producing a model EMG signal from a measured EMG signal, wherein the measured EMG signal includes a patient'"'"'s EMG signal and an ECG signal, the apparatus comprising:

logic signal processing means for processing the measured EMG signal to produce a logic signal that is (1) in a first binary state responsive to an absence of a P wave, a QRS complex and a T wave in a measured EMG signal and (2) in a second binary state responsive to a presence of at least one of the P wave, the QRS complex, and the T wave in the measured EMG signal;

first envelope processing means for processing the measured EMG signal to produce a first envelope signal; and

averaging means for producing a model EMG signal as a function of (1) the current first envelope signal responsive to the logic signal being in the first binary state and (2) a signal other than the current first envelope signal responsive to the logic signal being in the second binary state.

12. The apparatus as set forth in claim 11, wherein the logic signal processing means includes:

second envelope processing means for processing the measured EMG signal to produce a second envelope signal;

fast signal processing means for processing the second envelope signal to produce a fast signal;

first slow signal processing means for processing the second envelope signal to produce a first slow signal having a slew rate slower than a slew rate of the fast signal; and

comparing means for comparing the fast signal and the first slow signal to produce the logic signal.

13. The apparatus as set forth in claim 11, wherein the first envelope processing means includes:

high pass filtering means for high pass filtering the measured EMG signal to produce a high pass signal,

rectifying means for rectifying the high pass signal to produce a rectified signal, and

low pass filtering means for low pass filtering the rectified signal to produce the first envelope signal.

14. The apparatus as set forth in claim 11, wherein the averaging means provides (1) a moving average of the current first envelope signal, responsive to the logic signal being in the first binary state and (2) a set value that corresponds to a value of the moving average of the first envelope signal existing when the logic signal changed from the first binary state to the second binary state, responsive to the logic signal being in the second binary state.

15. The apparatus as set forth in claim 12, wherein the second envelope processing means includes:

first low pass filtering means for low pass filtering the measured EMG signal to produce a first filtered signal, and

first rectifying means for rectifying the first filtered signal to produce the second envelope signal;

the fast signal processing means includes;

second low pass filtering means for low pass filtering the second envelope signal to produce a second filtered signal,

first amplifying means for amplifying the second filtered signal to produce a first amplified signal,

third low pass filtering means for low pass filtering the first amplified signal to produce a third filtered signal, and

combining means for combining the second filtered signal and the third filtered signal to produce the fast signal;

the first slow signal processing means includes;

second amplifying means for amplifying the second envelope signal to produce a second amplified signal, and

fourth low pass filtering means for low pass filtering the second amplified signal to produce the first slow signal; and

wherein the comparing means compares the fast signal and the first slow signal to produce, as a function of the comparison, the logic signal.

16. The apparatus as set forth in claim 12, wherein the logic signal processing means includes second slow signal processing means for processing the second envelope signal to produce a second slow signal having a slew rate slower than the slew rate of the fast signal, and wherein the comparing means produces the logic signal as a function of the fast signal, the first slow signal and the second slow signal.

17. The apparatus as set forth in claim 16, wherein the second envelope processing means includes:

first low pass filtering means for filtering the measured EMG signal to produce a first filtered signal, and

first rectifying means for rectifying the first filtered signal to produce the second envelope signal;

the fast signal processing means includes;

second low pass filtering means for filtering the second envelope signal to produce a second filtered signal,

first amplifying means for amplifying the second filtered signal to produce a first amplified signal,

third low pass filtering means for filtering the first amplified signal to produce a third filtered signal, and

combining means for combining the second filtered signal and the third filtered signal to produce the fast signal;

the first slow signal processing means includes;

second amplifying means for amplifying the second envelope signal to produce a second amplified signal, and

fourth low pass filtering means for low pass filtering the second amplified signal to produce the first slow signal;

the second slow signal processing means includes;

the second amplifying means for amplifying the second envelope signal to produce the second amplified signal, and

fifth low pass filtering means which low pass filters the second amplified signal to produce the second slow signal; and

the comparing means includes;

first comparing means for comparing the fast signal and the first slow signal to produce a first comparator signal,

second comparing means for compares the fast signal and the second slow signal to produce a second comparator signal, and

logic gate means for combining the first comparator signal and the second comparator signal to produce the logic signal.

18. The apparatus as set forth in claim 11, further including at least one of:

filtering means for filtering the measured EMG signal prior to at least one of the logic signal processing means and the first envelope processing means processing the measured EMG signal; and

amplifying means for amplifying the measured EMG signal prior to at least one of the logic signal processing means and the first envelope processing means processing the measured EMG signal.

19. The apparatus as set forth in claim 16, wherein the comparing means includes:

first comparing means for comparing the fast signal and the first slow signal to produce a first comparator signal;

second comparing means for comparing the fast signal and the second slow signal to produce a second comparator signal; and

logic gate means for combining the first comparator signal and the second comparator signal to produce the logic signal.

20. The apparatus as set forth in claim 19, wherein the second slow signal processing means produces the second slow signal as a function of the second envelope signal responsive to the first comparator signal being in the first binary state and wherein the second slow signal processing means produces the second slow signal as a set value corresponding to a value of the second envelope signal existing when the first comparator signal changed from the first binary state to the second binary state responsive to the first comparator signal being in the second binary state.

21. The apparatus as set forth in claim 12, further including:

third envelope processing means for continuously processing the measured EMG signal to produce a third envelope signal, wherein the averaging means provides (1) a moving average of the first envelope signal responsive to the logic signal being in the first binary state and (2) a moving average of the third envelope signal responsive to the logic signal being in the second binary state.

22. The apparatus as set forth in claim 21, wherein:

the first envelope processing means includes;

first high pass filtering means for high pass filtering the measured EMG signal to produce a first high pass signal,

first rectifying means for rectifying the first high pass signal to produce a first rectified signal, and

first low pass filtering means for low pass filtering the first rectified signal to produce the first envelope signal; and

the third envelope processing means includes;

second high pass filtering means for high pass filtering the measured EMG signal to produce a second high pass signal,

second rectifying means for rectifying the second high pass signal to produce a second rectified signal, and

second low pass filtering means for low pass filtering the second rectified signal to produce the third envelope signal.

23. An apparatus for producing a model EMG signal from a measured EMG signal, wherein the measured EMG signal includes a patient'"'"'s EMG signal and ECG signal, the apparatus comprising:

a logic signal processor adapted to receive the measured EMG signal to produce a logic signal that is (1) in a first binary state responsive to an absence of a P wave, a QRS complex and a T wave in a measured EMG signal and (2) in a second binary state responsive to a presence of at least one of the P wave, the QRS complex, and the T wave in the measured EMG signal;

a first envelope processor adapted to receive such a measured EMG signal and output a first envelope signal based on the measured EMG signal;

an averager operatively coupled to the first envelope processor, wherein the averager outputs a signal corresponding to a moving average of the first envelope signal; and

a switch system operatively coupled to the logic signal processor and to at least of the first envelope processor and the averager, wherein the switch system operates based on the logic signal to at least one of (1) communicate the measured EMG signal to the first envelope processor and (2) communicate the first envelope signal to the averager responsive to the logic signal being in the first binary state so that the averager provides the model EMG signal as a function of a current first envelope signal responsive to the logic signal being in the first binary state, and wherein the switch operates based on the logic signal to at least one of (3) prevent communication of the measured EMG signal to the first envelope processor and (4) prevent communication of the first envelope signal to the averager responsive to the logic signal being in the second binary state so that the averager provides the model EMG signal as a function of a signal other than the current first envelope signal responsive to the logic signal being in the second binary state.

24. The apparatus as set forth in claim 23, wherein the switching system includes:

a first switch that couples the measured EMG signal to the first envelope processor responsive to the logic signal being in the first binary state and isolates the measured EMG signal from the first envelope processor responsive to the logic signal being in the second binary state; and

a second switch that couples the first envelope signal to the averager responsive to the logic signal being in the first binary state and isolates the first envelope signal from the averager responsive to the logic signal being in the second binary state.

25. The apparatus as set forth in claim 24, wherein the logic signal processor includes:

a second envelope processor adapted to receive such a measured EMG signal and output a second envelope signal based on the measured EMG signal;

a fast signal processor operatively coupled to the second envelope processor, wherein the fast signal processor outputs a fast signal based on the second envelope signal;

a first slow signal processor operatively coupled to the second envelope processor, wherein the first slow signal processor outputs a first slow signal based on the second envelope signal;

a comparer operatively coupled to the fast signal processor and the first slow signal processor, wherein the comparer compares the fast signal and the first slow signal to produce the logic signal.

26. The apparatus as set forth in claim 25, wherein the logic signal processor further comprises a second slow signal processor operatively coupled to the second envelope processor and the comparer, wherein the second slow signal processor outputs a second slow signal based on the second envelope signal, wherein the comparer produces the logic signal as a function of the fast signal, the first slow signal and the second slow signal.

27. The apparatus as set forth in claim 26, wherein the comparer includes:

a first comparator operatively coupled to the fast signal processor and the first slow signal processor, wherein the first comparator compares the fast signal and the first slow signal and outputs a first comparator signal based on this comparison;

a second comparator operatively coupled to the fast signal processor and the second slow signal processor, wherein the first comparator compares the fast signal and the second slow signal and outputs a second comparator signal based on this comparison; and

a logic gate operatively coupled to the first comparator and the second comparator, wherein the logic gate logically combines the first comparator signal and the second comparator signal to produce the logic signal.

28. The apparatus as set forth in claim 27, wherein the second slow signal processor includes:

an amplifier operatively coupled to the second envelope processor, wherein the amplifier amplifies the second envelope signal and outputs an amplified signal;

a low pass filter operatively coupled to the amplifier, wherein the low pass filter low pass filters the amplified signal and outputs the second slow signal; and

a third switch operatively coupled to the amplifier and the low pass filter, wherein the third switch couples the amplifier to the low pass filter responsive to the first comparator signal being in a first binary state and isolates the amplifier from the low pass filter responsive to the first comparator signal being in a second binary state, wherein the low pass filter produces the second slow signal as a function of (1) the amplified signal responsive to the first comparator signal being in the first binary state and (2) a set value corresponding to a value of the amplified signal existing when the logic signal changed from the first binary state to the second binary state responsive to the first comparator signal being in the second binary state.

29. The apparatus as set forth in claim 25, wherein:

the first envelope processor includes;

a first high pass filter adapted to receive such a measured EMG signal, wherein the first high pass filter high pass filters the measured EMG signal and outputs a first high pass signal,

a first rectifier operatively coupled to the first high pass filter, wherein the first rectifier rectifies the first high pass signal and outputs a first rectified signal, and

a first low pass operatively coupled to the first rectifier, wherein the first low pass filter low pass filters the first rectified signal and outputs the first envelope signal;

the second envelope processor includes;

a second low pass filter adapted to receive such a measured EMG signal, wherein the second low pass filter low pass filters the measured EMG signal and outputs a second low pass signal,

a second rectifier operatively coupled to the second low pass filter, wherein the second rectifier rectifies the second low pass signal and outputs the second envelope signal;

the fast signal processor includes;

a third low pass filter operatively coupled to the second envelope processor, wherein the third low pass filter low pass filters the second envelope signal and outputs a third low pass signal,

an amplifier operatively coupled to the third low pass filter, wherein the amplifier amplifies the third low pass filtered signal and outputs a first amplified signal,

a fourth low pass operatively coupled to the amplifier, wherein the fourth low pass filter low pass filters the first amplified signal and outputs a fourth low pass signal, and

a combiner operatively coupled to the third and the fourth low pass filters, wherein the combiner combines the third low pass signal and fourth low pass signal and outputs the fast signal; and

the first slow signal processor includes;

a second amplifier operatively coupled to the second envelope processor, wherein the second amplifier amplifies the second envelope signal to produce the amplified signal and a fifth low pass filter which filters the amplified signal and outputs the first slow signal.

30. The apparatus as set forth in claim 23, further comprising a second envelope processor adapted to receive the measured EMG signal and output a second envelope signal based on the measured EMG signal, wherein the switch system communicates the measured EMG signal to the second envelope processor responsive to the logic signal being in the first binary state and prevents communication of the measured EMG signal to the second envelope processor and responsive to the logic signal being in the second binary state.

31. The apparatus as set forth in claim 23, further including a third envelope processor adapted to receive such a measured EMG signal, wherein the third envelope processor continuously processes the measured EMG signal and outputs a third envelope signal, and wherein the switch system couples the first envelope signal to the averager responsive to the logic signal being in the first binary state and couples the third envelope signal to the averager responsive to the logic signal is in the second binary state, with the averager producing the model EMG signal as a function of the first envelope signal responsive to the logic signal being in the first binary state and the third envelope signal responsive to the logic signal being in the second binary state.

32. The apparatus as set forth in claim 27, wherein at a leading edge of the P wave, the fast signal increases above the first and second slow signals, the first and second comparator signals change to deasserted, the second slow signal assumes the set value and the logic signal changes to the second binary state;

and

at a trailing edge of the P wave, the fast signal decreases below the first and second slow signals, the first and the second comparator signals change to asserted, the second slow signal initiates changing from the set value as a function of the amplified signal and the logic signal changes to the first binary state.

33. The apparatus as set forth in claim 27, wherein at a leading edge of the QRS complex, the fast signal increases above the first and second slow signals, the first and second comparator signals change from a first binary state to a second binary state, the second slow signal assumes the set value and the logic signal changes to the second binary state;

during the QRS complex, the fast signal decreases below the first slow signal, the first comparator signal changes to the first binary state and the second slow signal initiates changing from the set value as a function of the amplified signal whereby the second slow signal converges toward the first slow signal; and

at a trailing edge of the QRS complex, the fast signal decreases below the second slow signal, the second comparator signal changes to the first binary state and the logic signal changes to the first binary state.

34. The apparatus as set forth in claim 27, wherein at a leading edge of the P wave, the fast signal increases above the second slow signal, the second comparator signal changes to the second binary state and the logic signal changes to the second binary state;

and

at a trailing edge of the P wave, the fast signal decreases below the second slow signal, the second comparator signal changes to the first binary state and the logic signal changes to the first binary state.

35. The apparatus as set forth in claim 23, further including at least one of:

a filter adapted to receive the measured EMG signal and operatively coupled to at least one of the first envelope processor and the logic signal processor, wherein the filter filters the measured EMG signal prior to at least one of the first envelope processor and the logic signal processor processing the measured EMG signal; and

an amplifier adapted to receive the measured EMG signal and operatively coupled to at least one of the first envelope processor and the logic signal processor, wherein the amplifier amplifies the measured EMG signal prior to at least one of the first envelope processor and the logic signal processor processing the measured EMG signal.

36. The apparatus as set forth in claim 23, further comprising a pair of sensors adapted to be coupled to a patient to output the measured EMG signal.