Method and apparatus for analyzing uterine electrical activity from surface measurements for obstetrical diagnosis

• US 5,776,073 A
• Filed: 04/25/1997
• Issued: 07/07/1998
• Est. Priority Date: 05/19/1994
• Status: Expired due to Term

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Boyle, Mary B., Garfield, Robert E.
• Primary Examiner(s): HINDENBURG, MAX F
• Application Number:
  US08/845,689
• Time in Patent Office: 438 Days
• Field of Search: 600/546, 600/547, 600/587, 600/591, 600/595
• US Class Current: 600/546
• CPC Class Codes: A61B 5/035 Intra-uterine probes therefor
• CPC Class Codes: A61B 5/282 Holders for multiple electrodes for introduction into the body A61B5/287
• CPC Class Codes: A61B 5/391 of genito-urinary organs
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: A61B 5/7242 using integration
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

A method and apparatus is presented for recording uterine electrical activity from the surface of the abdomen or vagina for the purpose of diagnosing contractile patterns of the uterus or abdominal muscles in pregnant and nonpregnant patients. The present invention provides data analysis techniques for analyzing electromyographic data measured from the surface of a patient to characterize uterine activity. The method and apparatus described include algorithms for the systematic analysis of electrical signals recorded from the abdominal surface. Such processing comprises integration of signals, frequency spectral analysis, 3-dimensional power density mesh plots, vector analysis, fast wavelet transform, and joint time-frequency characteristics. These techniques and apparatus are appropriate for use in a clinic or through communication lines for use as a remote or home uterine monitoring system. As such, uterine electrical activity may be measured at a remote location and processed at a central facility through on-line communications channels, such as a telephone line. The techniques and apparatus disclosed are also useful in predicting successful treatment for cases where either the uterus fails to develop forceful contractions at term or begins to contract pre-term.

Claims

1. A method for characterizing uterine electrical activity, comprising:

a. applying action potential measuring electrodes to an abdominal or vaginal (or cervical) surface of a patient;

b. acquiring analog electromyographic signals transmitted through said electrodes, at a sampling frequency between about 0.5 and 1 kHz, for a duration of time sufficient to record at least one burst of action potentials;

c. amplifying said electromyographic signals;

d. storing acquired electromyographic signals, including at least one burst of action potentials;

e. analyzing uterine activity indicating parameters from at least one burst of action potentials within the stored electromyographic signals; and

f. characterizing uterine activity of said patient based on said parameter analysis.

2. The method of claim 1, wherein said analyzing further comprise determining the frequency, duration, amplitude, and power density spectrum of said bursts and the frequency, duration, and amplitude of a plurality of action potentials in one or more of said bursts.

3. The method of claim 1, wherein said analyzing further comprises:

a. determining the mean frequency of a plurality of action potentials in at least one of said bursts;

b. determining the starting frequency of action potentials in at least one of said bursts; and

c. determining the ending frequency of action potentials in at least one of said bursts.

4. The method of claim 2, wherein said analyzing further comprises:

a. determining the rate of rise of amplitude in at least one action potential in at least one of said bursts; and

b. determining the rate of fall of amplitude in at least one action potential in at least one of said bursts.

5. The method of claim 1, wherein said analyzing uterine activity comprises examining one or more trends in uterine activity indicating parameters over time.

6. The method of claim 5, further comprising displaying one or more trends in uterine activity indicating parameters over time.

7. The method of claim 5, further comprising the step of predicting future uterine activity based upon one or more identified trends of examined uterine activity indicating parameters.

8. The method of claim 7, wherein said predicting future uterine activity comprises the steps of:

a. comparing identified trends of a patient'"'"'s examined uterine activity with trend data collected from other patients in order to identify matching trends; and

b. predicting future uterine activity for a patient under examination based upon the trend behavior shown in the matching trends.

9. The method of claim 8 wherein said predicting is performed with the use of an expert system.

10. The method of claim 7, wherein said predicting future uterine activity comprises using a chaotic model of electromyographic activity to predict future uterine activity.

11. The method of claim 7, wherein said predicting future uterine activity comprises identifying situations in which treatment for pharmacologically inducing or inhibiting labor in said patient may be indicated.

12. The method of claim 1, wherein said characterizing further comprises detecting the contraction of abdominal muscles in the patient.

13. The method of claim 1 wherein said analyzing uterine activity comprises determining the fast wavelet transform characteristics of said frequency components of bursts of action potential within said electromyographic signals.

14. The method of claim 1 wherein said analyzing step further comprises determining joint time-frequency characteristics of said frequency components of bursts of action potentials within said electromyographic signals.

15. The method of claim 1, further comprising:

a. stimulating a vagina of said patient while said electromyographic signals are being stored; and

b. diagnosing labor as a function of said analysis of uterine activity.

16. The method of claim 1, wherein said analyzing step further comprises generating a three dimensional mesh plot of said power density spectral characteristics, said mesh plot displaying energy levels versus frequency versus time of pregnancy.

17. An apparatus for recording and analyzing uterine electrical activity for the abdominal or vaginal surface, comprising

a. at least one electrode capable of measuring action potentials emitted from the abdominal or vaginal surface of a patient under analysis and further capable of emitting an analog signal indicative of action potentials measured by said electrode;

b. an amplifier electrically coupled to said electrode to receive and amplify a signal indicative of action potentials measured by said electrode;

c. a memory comprising sufficient storage capacity to store data resulting from a sampling of electromyographic signals at a sampling frequency of at least 100 Hz for a duration of time sufficient to record at least five bursts of action potentials, said memory coupled to receive a digital input from said amplifier indicative of action potential signals received by said converter;

d. a filtering device capable of segregating and identifying electromyographic signals, including action potentials, in a frequency range of 0.3 Hz to 50 Hz from electromyographic signals outside said range; and

e. a computer comprising an expert system programmed to analyze the frequency, duration, amplitude, and power density spectrum of action potential bursts and individual action potentials, said expert system further being capable of characterizing uterine activity based upon said analysis.

18. The apparatus of claim 17, wherein said expert system is further capable of identifying abdominal muscle contraction.

19. The apparatus of claim 17, wherein said memory is capable of storing said electromyographic signals in discrete, predetermined frequency ranges.

20. The apparatus of claim 17, wherein said expert system is further capable of determining the mean frequency, starting frequency, and ending frequency of a plurality of action potentials.

21. The apparatus of claim 17, wherein said action potential measuring electrode is a needle electrode.

22. The apparatus of claim 17, further comprising a monitor coupled to said computer, said monitor capable of displaying said electromyographic signals.

23. A remote uterine monitoring system for remotely characterizing uterine activity, comprising:

a. at least one electrode capable of measuring action potentials emitted from the abdominal or vaginal surface of a patient under analysis and further capable of emitting an analog signal indicative of action potentials measured by said electrode;

b. an amplifier electrically coupled to said electrode to receive and amplify a signal indicative of action potentials measured by said electrode;

c. a data transmission system capable of receiving an amplified signal from said amplifier and transmitting said signal to a remote location from said electrode;

d. a remote analog to digital converter coupled to said data transmission system to receive an analog input from said amplifier indicative of action potentials measured by said electrode;

e. a memory comprising sufficient storage capacity to store data resulting from a sampling of electromyographic signals at a sampling frequency of at least 100 Hz for a duration of time sufficient to record at least five bursts of action potentials, said memory coupled to receive a digital input from said analog to digital converter indicative of action potential signals received by said converter;

f. a filtering device capable of segregating and identifying electromyographic signals, including action potentials, in a frequency range of 0.3 Hz to 50 Hz from electromyographic signals outside said range; and

g. a computer comprising an expert system programmed to analyze the frequency, duration, amplitude, and power density spectrum of action potential bursts and individual action potentials, said expert system further being capable of characterizing uterine activity based upon said analysis.