JPS582328Y2 - External tocodynamometer - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a non-invasive tocodynamometer, that is, an external tocodynamometer, which is particularly useful for monitoring childbirth and the like.

Conventionally, as an external tocodynamometer, a transducer in the form of a displacement meter or a stiffness meter called a compressor type or guard ring type is attached to the mother's abdomen, and a transducer is used to measure the muscle tissue directly under the abdominal wall during contraction attacks. Most of them were of the type that measured apparent hardness.

The measurement results with this type of mechanical transducer are
This method agrees fairly well with the results of direct measurement of intrauterine pressure using the catheter method, etc., and is currently widely used because it is possible to obtain highly reliable labor signal waves.

However, due to its operating principle, this type of external labor transducer must be used by pressing it against the abdominal wall surface with a certain preload force. The transducer was wrapped around the circumference and tightened to press the transducer against the abdominal wall.

This causes depression and considerable burden and pain to the mother, and when the mother's body position changes from supine to sideways to standing, etc., the preload force of the transducer is reduced. As a result, it has been difficult to perform stable measurements.

Therefore, the present invention aims to provide an external tocodynamometer that can measure labor pains with high reliability without causing any burden or pain to the mother's body and without being affected by the body position of the mother.

Contraction attacks are caused by contractions of the uterine muscles and additionally the rectus abdominis muscles.

Therefore, it is possible to measure labor pain by observing the myoelectric signals generated in these muscles during a labor attack.

Conventionally, this myoelectric component has been known as noise when extracting the maternal abdominal wall-induced fetal electrocardiographic signal and measuring the fetal heartbeat based on it, and has been removed as noise when measuring the fetal heartbeat.

According to the present invention, such myoelectric components are extracted and labor pains are measured based on their relative strength.

The biological signals obtained from electrodes attached to the mother's body contain a mixture of maternal electrocardiographic signals, fetal electrocardiographic signals, myoelectric signals, etc., and myoelectric signals are more sensitive than other cardiac signals. It is weak and cannot be completely extracted by a bandpass filter alone.

For example, as shown in FIG. 1, biological signals collected via a voluminous electrode 11 connected to the abdominal wall of the mother's body and an indifferent electrode 12 if necessary are amplified by an amplifier 13, and myoelectric components are filtered by a bandpass filter 14. Assuming a configuration in which only signal components in a frequency band around 30, which corresponds to the The width, level, and frequency of the mother and child's electrocardiographic signal components mixed in the mother and child, especially the R wave component, vary greatly from individual to individual, and cannot be completely removed with a simple bandpass filter.
For this reason, it is impossible to provide an appropriate baseline level with myoelectric signals mixed with such electrocardiographic signal components, making it difficult to effectively quantitatively measure weak early contraction attacks.

Therefore, in the external tocodynamometer according to the present invention, in order to eliminate the influence of the electrocardiographic signal components as described above, the electrocardiographic signal is extracted from the biosignal, and the biosignal is sampled only during the period excluding the period of existence of the electrocardiographic signal. It is characterized by executing, detecting and averaging the detected signals.

Hereinafter, with reference to FIG. 2, an embodiment of the external tocodynamometer according to the present invention will be described.

The biological signals collected by the quantified electrode 11 and, if necessary, the indifferent electrode 12 attached to the abdominal wall 10 of the mother's body are amplified by the amplifier 13 and inputted to the vano:2 filter 20.

This bandpass filter 20 has a passband of, for example, 10 to 45 stops, and receives a composite signal as shown in FIG. It acts to extract.

The composite signal from the bandpass filter 20 is sent to the delay circuit 2
2 and bandpass filter 24.

The bandpass filter 24 has a pass band of 10 to 20 Hz in order to extract the R wave component of the maternal electrocardiogram signal (the part indicated by waveform M in FIG. 3a) from the composite signal.

The output of the bandpass filter 24 is input to the maternal electrocardiogram R wave detection circuit 26 .

This maternal electrocardiogram R-wave detection circuit 26 detects a third wave having a width slightly longer than the width of the maternal electrocardiogram R-wave, almost in synchronization with the maternal electrocardiogram R-wave.
It outputs a pulsed binary signal as shown in Fig.
The trigger pulse generator disclosed in No. 04 (Utility Model Application Publication No. 53-147644) can be used.

On the other hand, the delay circuit 22 is provided to compensate for the time delay caused by the bandpass filter 24 and the detection circuit 26,
The time composite signal corresponding to the time delay is delayed and output to the next signal switch 28.

For example, a BBD delay line of several hundred stages driven by an appropriate lock is suitable for the delay circuit 22.

The signal switch 28 is controlled by the output pulse signal from the maternal electrocardiogram R wave detection circuit 26 and removes the portion corresponding to the maternal electrocardiogram R wave from the composite signal from the delay circuit 22.

That is, a composite signal delayed only for a period excluding the period corresponding to the maternal electrocardiogram R wave is sampled, and a composite signal as shown in FIG. 3 is output.

As mentioned above, this method applies a delay to the input signal, detects pulse-like noise in the input signal without delay, and removes the pulse-like noise by equivalently preempting the delayed input signal based on the detected pulse-like noise. is widely used,
It is publicly known.

As such a method, for example, Utility Application No. 52-5400
5 (Utility Model No. 53-148587, Utility Model No. 56-335
25) can be used.

The composite signal from which the section corresponding to the maternal electrocardiogram R wave has been removed by the signal switch 28 is passed through a delay circuit 22A, a bandpass filter 24A, and a fetal electrocardiogram connected in the same manner as the circuit for removing the maternal electrocardiogram R wave section. The signal is input to a fetal electrocardiogram R-wave section removal circuit comprised of an R-wave detection circuit 26A and a signal switch 28A.

The difference between this circuit and the maternal electrocardiogram R wave section removal circuit is that the bandpass filter 24A
) to extract, for example, a passband of 20 to 40 stops.

Therefore, from the signal switch 28A controlled by the pulsed binary signal as shown in FIG. 3Y from the fetal electrocardiogram R wave detection circuit 26A, the maternal electrocardiogram R wave signal and the fetal electrocardiogram signal as shown in FIG. The electrocardiographic R wave signal is removed, and a signal consisting only of myocardial signal components is output.

The output signal of the signal switch 28A is sent via a bandpass filter 30 to an envelope detector 32, where it is subjected to envelope detection as shown in FIG. 3d.

When amplitude detection is performed simply in this way, the envelope of the section removed as corresponding to the electrocardiographic R wave becomes zero as shown in FIG. 3d.

Therefore, if the signals are simply averaged as they are, a correct amplitude signal cannot be obtained.

To be more specific, when each R-wave section is removed from the composite biological signal by the maternal electrocardiogram R-wave section removal circuit and the fetal electrocardiogram R-wave section removal circuit, the R-wave sections overlap with those electrocardiographic signals. The generated myoelectric signals are also removed.

Even if it is assumed that the removal interval is constant, the residual ratio of the myoelectric signal will change depending on the heart rate of the mother and fetus, and the frequency with which the maternal and fetal ECG signal removal intervals overlap. Therefore, if the output signal of the detector 32 is averaged over the entire time period, accurate measurement will not be obtained.

Therefore, it is necessary to average by a time rate that does not include the removal section.

Therefore, in the present invention, the output of the detector 32 is sent to the averager 3 through the signal switch 34 and the analog memory 36.
On the other hand, each output of the maternal electrocardiogram R wave detection circuit 26 and the fetal electrocardiogram R wave detection circuit 26A is applied as a control signal to the signal switch 38 via the OR gate 40.

With this configuration, when the output signal of the detector 32 is at zero level, that is, in the section that corresponds to the electrocardiographic R wave and is removed, the output of the detector 32 is equal to the averager 3.
The value that is not sampled to 8 and is held in analog storage 36 is provided to averager 38 .

The output of the averager 38 is then connected to a recorder 42.

As described above, according to the present invention, it is possible to measure the intensity of the myoelectric signal component from the biological signal obtained from the maternal abdominal wall without being influenced by the maternal electrocardiogram signal and the fetal electrocardiogram signal. Labor pains can be measured using a measurement method.

Furthermore, if necessary, the output of the fetal electrocardiogram R wave detection circuit 26A can be applied to the fetal JDab counter 44 to measure the fetal heartbeat, and if it is input to another channel of the recorder 42, The fetal heartbeat waveform is also recorded in parallel with the contraction waveform and can be viewed as a waveform.

Furthermore, in the embodiments described above, both the maternal electrocardiographic R-wave component and the fetal electrocardiographic R-wave component are removed from the biological signal.

In terms of actual signal energy, the maternal electrocardiogram R-wave component, which has a high amplitude and a long duration, is overwhelmingly stronger than the fetal electrocardiogram R-wave component, which has a small amplitude and a short duration. occupies the majority of

Therefore, in the above-described embodiment, even if the fetal electrocardiogram R-wave section removal circuit is omitted, labor pain measurement using myoelectric signals can be sufficiently carried out.

[Brief explanation of the drawing]

Fig. 1 is a schematic block diagram of a tocodynamometer using biological signals, Fig. 2 is a block diagram of an external tocodynamometer according to the present invention, and Fig. 3 is a waveform diagram of each point in the block diagram of Fig. 2. be. 11.12... Electrode, 13... Amplifier, 14, 20, 24, 24 A. 30...Band pass filter, 15.32...
...Detector, 16...Low pass filter,
17.42...Recorder, 22,22A...
... Delay circuit, 26.26 A ... Electrocardiogram R wave detection circuit, 28.28 A, 34 ... Signal switch, 36 ... Analog memory, 38.・・・・・・
・Averaging device.

Claims (1)

[Scope of utility model registration request] An electrode adapted to be attached to the base layer wall soil, an amplifier for receiving and amplifying a biological signal from the electrode, a means for removing an electrocardiographic signal component from an output signal of the amplifier, and a means for removing an electrocardiographic signal component from the output signal of the amplifier. The electrocardiographic signal component removing means is connected to a delay circuit and an output of the delay circuit. a bandpass filter connected to the input of the delay circuit for extracting the electrocardiographic R wave component; and a bandpass filter connected to the output of the bandpass filter for extracting the electrocardiographic R wave component
an electrocardiographic R wave detection circuit that opens the signal switch for a time corresponding to the wave component; a connected detector, a signal switch connected to the output of the detector and configured to be opened for a time corresponding to the R wave component by the electrocardiographic R wave detection circuit, and an output of the signal switch. An external tocodynamometer, which has an averager that receives the signals.