JPH064063B2 - ECG recording / reproducing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrocardiogram recording / reproducing apparatus.

[Prior Art] Conventionally, in order to diagnose, treat, or prevent a cardiovascular disease, an electrocardiogram is taken from a living body for a long time, for example, 24 hours, and reproduced at a speed of 60 times or 120 times. Observation is taking place.

Thus, in general, a long-term electrocardiogram waveform obtained from a living body includes, in addition to the original observation target signal as a high-frequency component on the baseline, a drift of a low-frequency component caused by moving the body, etc. Represented as superimposed on the baseline. That is, the low frequency drift causes the base line of the observation target signal, which is a high frequency component, to fluctuate up and down.

Therefore, the above-mentioned drift has an unfavorable effect on the observation of the electrocardiogram waveform, and in particular, the electrocardiogram waveform often fluctuates up and down to deviate from the display range of the display device, which hinders observation of the waveform. Therefore, it is desired to remove the drift and flatten the baseline.

However, focusing on the frequency difference between the low-frequency component drift and the high-frequency component observation target signal, when attempting to remove the low-frequency drift by a means such as a low-frequency cutoff filter, the time constant of the filter is set appropriately. Even if the drift can be removed, it is inevitable that phase distortion will occur in the observation target signal. It is natural that this phase distortion has an unfavorable influence on the diagnosis of diseases from the electrocardiogram waveform.

Therefore, when removing the drift, it is necessary to prevent phase distortion from occurring in the high-frequency observation target signal, but the one using a computer or the like as a signal processing circuit for realizing it is extremely complicated and expensive. In addition, it takes a long time to process the signal, and the data processing cannot be performed at high speed.

[Problems to be Solved by the Invention] An object of the present invention is to reproduce an electrocardiographic recording at high speed and observe it without causing phase distortion in an observation target signal.
An object of the present invention is to provide a device capable of removing a drift from a baseline as an extremely simple and inexpensive device.

[Means for Solving Problems] In order to achieve the above object, the recording / reproducing apparatus of the present invention comprises a recording unit for detecting and recording an electrocardiographic signal of a subject, and a reproducing unit for reproducing the recorded electrocardiographic signal. The recording unit records the observation target signal in a state in which a phase distortion has occurred by passing through the filter, and a low-frequency cutoff filter that removes the drift of the low frequency component in the electrocardiogram signal detected from the subject. And a reproducing unit that reproduces the signal recorded in the recording unit by inverting the positive / negative of the time axis, and the reproduction signal of the reproducing unit.
It is configured to include a low-frequency cutoff filter that causes a phase distortion that cancels and removes the phase distortion included in the signal, and a recording indicator that records and displays the result.

[Operation] When the electrocardiogram signal detected from the subject passes through the low-frequency cutoff filter, the drift component is removed from the baseline of the electrocardiogram signal, but at the same time, phase distortion occurs in the observed signal, which is a high-frequency component. , Is recorded in the recorder in that state. The electrocardiogram signal recorded in the recording device is reproduced in the reproducing device by reversing the positive / negative of the time axis, that is, in the direction opposite to the time of recording. When the reproduced signal passes through the low-frequency cutoff filter in the reproducing section, a new phase distortion is generated at that time, but the phase distortion is canceled by the phase distortion generated earlier, and as a result, the phase distortion is generated. It is possible to obtain a long-term electrocardiogram signal without drifting without causing the drift.

[Embodiment] FIGS. 1 and 2 show an embodiment of an electrocardiogram recording / reproducing apparatus according to the present invention. This electrocardiogram recording / reproducing apparatus comprises a recording section as shown in FIG. And a reproducing unit as shown in FIG.

In the recording unit shown in FIG. 1, 1 is a subject, and an electrode 2 for detecting an electrocardiogram signal is attached to the subject 1, and the electrode 2 is connected to an electrocardiogram amplifier 4 via a low frequency cutoff filter 3. To be done. The filter 3 is for removing a drift component as a low frequency component from the electrocardiogram signal, and is composed of a capacitor and a resistor, and its time constant is set to, for example, about 0.3 seconds in consideration of the drift period and the like. It

The output terminal of the amplifier 4 is connected to the recorder 5.
The recorder 5 is for recording the electrocardiogram signal that has passed through the filter 3 and the amplifier 4. Various types of recording devices can be used as the recording device 5, but the signal once recorded is stored by reversing the positive and negative of the time axis by the reproducing device 11 described later, that is, recording can be taken out in the reverse direction in time. What is possible is, for example, a tape recorder or a card type magnetic disk (electronic memory) capable of recording a low frequency signal can be used.

FIG. 2 shows a reproducing unit for a long-term electrocardiogram signal recorded in the recording unit, and 11 is a reproducing unit, which is a signal recorded in advance on a recording medium such as a magnetic tape by the recording unit 5 in a temporally reverse direction, In addition, it can be played back faster than the recording time,
The regenerator 11 is passed through a regenerative amplifier 12 to a low cutoff filter.
Connected to 13 inputs.

The filter 13 has a phase distortion which is complementary to the phase distortion generated when the filter 3 is passed first, that is, a phase which cancels and removes the previous phase distortion by superimposing it on the reproduction signal passing therethrough. Distortion is caused, and its time constant is set according to the reproduction speed of the above-mentioned reproducing device 11. For example, when reproducing at 60 times the recording time, the time constant of the filter 3 of the recording section is set to 0.3 seconds. Therefore, it is set to 0.3 / 120 seconds when reproducing at a speed of 0.3 / 60 seconds and 120 times.

At the output side of the low-frequency cutoff filter 13, a sequential analysis device 14
Also, a record indicator 15 is connected. The analysis device 14 is for performing analysis when reproducing the signal sent through the low-frequency cutoff filter 13 as an electrocardiogram waveform, and based on the signal sent from the analysis device 14, a recording indicator 15
The electrocardiogram waveform is recorded on a recording sheet or displayed on another recording indicator. At the time of the above-mentioned display, the electrocardiogram waveform can be divided into several lines at regular intervals by writing to, reading from, etc. in the memory.

In the device having the above configuration, the electrode 2 is attached to the subject 1, and the electrocardiogram amplifier 4 and the recorder 5 in the recording unit are attached.
In the operating state, the electrocardiogram signal detected through the electrode 2 is sent to the recorder 5 via the low-frequency cutoff filter 3 and the electrocardiogram amplifier 4, and is recorded on the recording medium such as a magnetic tape in the recorder 5. It

In the above process, when the electrocardiogram signal detected by the electrode 2 reaches the filter 3, the low frequency component drift in the electrocardiogram signal is removed and only the original observation target signal, which is a high frequency component, passes through. Since the phase shift of the signal No. differs depending on the frequency, the signal to be observed is recorded in the recorder 5 in a state in which the phase distortion has occurred.

The recording medium, such as a magnetic tape, for which the recording of the electrocardiogram signal has been completed by the recording device 5 for a long time is performed in the reverse direction in time by the reproducing device 11, that is, the time axis is reversed, and the recording medium is compared with the recording time. The reproduction signal is reproduced at a very high speed, and the reproduction signal obtained thereby is sent to the low-frequency cutoff filter 13 via the reproduction amplifier 12.

This reproduced signal again causes phase distortion by passing through the low-frequency cutoff filter 13, and this phase distortion and the phase distortion that was previously received when passing through the low-frequency cutoff filter 3 are superposed and canceled. , Thus, the reproduced signal reaches the analyzer 14 with the phase distortion removed, and after being subjected to the necessary analytical processing, is sent to the recording indicator and displayed as an electrocardiogram waveform on the recording paper or the like in the recording indicator. To be done.

As described above, the electrocardiographic waveform is displayed while being reproduced in the reverse direction in time, so that it is inevitably recorded and displayed in the reverse direction in time, but not only is the baseline drift removed, The phase distortion is also removed. Therefore, by observing this waveform, it is possible to more accurately diagnose the circulatory system disease.

Needless to say, the recording unit and the reproducing unit can be configured as an integrated type having both recording and reproducing functions.

When a small-capacity electronic memory is used as the recorder 5, the electrocardiogram signal is not continuously recorded for a long time, but when a symptom of a circulatory system disease occurs, a certain time (for example, It is possible to record only for 10 minutes). Furthermore, when using such a small-capacity electronic memory, the electrocardiogram signal (0.1 to 20 Hz) should be recorded in the electronic memory for a certain period of time, and the data should be output at high speed (for example, 1,000 times). Due to the large capacity 1
It can be transferred to and stored in a normal tape recorder that can only record in the frequency range of 00Hz to 10KHz, and in this case, even if the tape recorder is played back at a normal speed, the ECG signal is played back at a substantially high speed. Therefore, a general-purpose inexpensive tape recorder can be used.

FIGS. 3 and 4 A and B show examples of measurement of electrocardiographic waveforms by the conventional device and the device of the present invention.

FIG. 3A shows an electrocardiographic signal detected from the subject, and since the electrocardiographic waveform includes a drift of a low frequency component, the baseline of the waveform has a large fluctuation. On the other hand, according to the present invention, when the waveform is recorded by the recording unit as shown in FIG. 1, the fluctuation of the base line is eliminated as shown in FIG. However, as indicated by circles in FIGS. 9A and 9B, the waveform in FIG. 9B has phase distortion.

Further, FIG. 4A shows a case where an electrocardiographic signal including a drift of a low frequency component is reproduced as in FIG. 3A, while FIG. 4B shows a case as shown in FIG. 3B. It shows a case where an electrocardiographic signal having phase distortion is reproduced through a reproducing unit as shown in FIG. According to FIG. 3B, it can be seen that the phase distortion shown in FIG. 3B is completely erased and is displayed in a state in which no drift is included.

The time axis in FIGS. 4A and 4B is reversed from that in FIGS. 3A and 3B, as shown in the drawing.

[Effects of the Invention] According to the present invention, an apparatus that removes drift without causing phase distortion in an electrocardiogram signal when reproducing and observing electrocardiographic recording at high speed has a simple structure and is inexpensive. Can be provided as. In addition, the device according to the present invention can use the existing device as it is, and from this point as well, it is not stupid that the economy is excellent, and the following effects can be expected.

(1) In the conventional electrocardiographic recording device, the cutoff frequency in the low frequency range is usually set to 3.2 seconds, that is, 0.05 Hz. Therefore, when a large artifact voltage enters due to electrode deflection, etc., the circuit potential swings positively or negatively and becomes saturated,
Since this recovery takes place with a time constant of 3.2 seconds, it takes a very long time to recover normally.

As a countermeasure against this, a circuit called an instrument circuit is provided for temporarily short-circuiting the low-frequency cutoff capacitor and quickly restoring it.

However, in the present invention, the low cutoff frequency is 0.
Since the slope is steep at 12 dB / OCT or 24 dB / OCT in about 3 seconds, the above recovery is performed in a short time of 1/10 to 1/10 of that of the conventional device. No need for a circuit.

(2) According to the present invention, an input voltage of, for example, 0.5 Hz or less is attenuated to 1/10 to 1/100 of the conventional level. Therefore, when the signal is superimposed on the low frequency oscillation, the operating range of the circuit is
Since 1/10 to 1/100 is sufficient, it is not necessary to connect a conventional amplifier having a low amplification degree in a cascade to secure a dynamic range, and only one amplifier is required.

(3) In the present invention, the low frequency range is cut by the low frequency cutoff filter of 0.5 Hz on the reproduction side as well. Therefore, the DC stability required for the circuit is significantly reduced, and an inexpensive circuit configuration with low DC stability can be obtained.

[Brief description of drawings]

1 and 2 are block configuration diagrams of a recording unit and a reproducing unit according to an embodiment of the present invention, FIGS. 3A and 3B, and FIGS. 4A and 4B are electrocardiographic waveforms obtained by the conventional device and the device of the present invention. It is a diagram showing an example of measurement of. 1 ・ ・ Subject, 3,13 ・ ・ Low-pass filter, 5 ・ ・ Recorder, 11 ・ ・ Reproducer

Claims (1)

[Claims] 1. A recording unit for detecting and recording an electrocardiographic signal of a subject, and a reproducing unit for reproducing the recorded electrocardiographic signal, wherein the recording unit detects drift of low frequency components in the electrocardiographic signal detected from the subject. A low cutoff filter to remove,
And a recorder for recording an observation target signal in a state in which phase distortion has occurred by passing through the filter, and the reproducing section reproduces the signal recorded by the recorder by inverting the positive and negative of the time axis. A regenerator, a reproduction signal of the regenerator, a low-frequency cutoff filter that causes phase distortion to cancel and remove the phase distortion contained in the signal, and a recording indicator that records and displays the result. An electrocardiogram recording / reproducing device characterized in that