JPS624972B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in electronic sphygmomanometers, and more particularly to an electronic sphygmomanometer that reliably detects Korotkoff sounds by distinguishing them from other sounds such as noise.

Conventionally, the blood flow is temporarily stopped by compressing the blood vessel artery with a cuff, and then the cuff pressure is reduced, and when the blood flow starts flowing again, a blood flow sound called Korotkoff sound is often generated in the blood vessel. Are known.

In the auscultation method, the cuff pressure at which the first Korotkoff sound is heard during this cuff pressure drop is defined as the systolic blood pressure. This Korotkoff sound also continues to occur while the cuff pressure is decreasing and continues until blood flow continues.
The cuff pressure at which this Korotkoff sound disappears is defined as the diastolic blood pressure.

Furthermore, the electronic blood pressure monitor automatically measures and displays the cuff pressure when the Korotkoff sound appears and disappears.

In this way, when measuring blood pressure, it is necessary to detect Korotkoff sounds, but in conventional electronic blood pressure monitors, it is difficult to detect whether the "sounds or vibrations generated from blood vessels" are pressure pulse waves that include Korotkoff sounds, pressure pulse waves, or pressure pulse waves. Frequency, signal strength of its frequency components, synchronization with pressure pulse waves, etc. are used as criteria for determining whether it is noise. That is, by providing an appropriate filter circuit in the signal path, the wave height levels of pressure pulse waves and noise are lowered, and Korotkoff sounds are discriminated based on a set threshold value. However, there are individual differences in the main constituent frequencies of Korotkoff sounds, ranging from several tens of Hz to 200-300 Hz. Therefore, it is impossible to set up a filter circuit that passes only the necessary and sufficient Korotkoff sound components for all test subjects in order to discriminate Korotkoff sounds. cannot be distinguished from pressure pulse waves, which have frequency components from several Hz to 30 to 40 Hz, and Korotkoff sounds cannot be identified. Furthermore, there were other problems such as the inability to measure blood pressure in people whose amplitude of "sounds or vibrations generated from blood vessels" was small.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to provide an electronic blood pressure monitor that identifies Kotlokoff sounds by extracting features on a signal waveform without using a filter that limits the frequency. In order to achieve this, the electronic blood pressure monitor of the present invention includes a pickup for detecting sound or vibration generated from blood vessels, a peak value holding means for holding the peak value of a signal waveform detected by the pickup, and a peak value holding means for holding the peak value of the signal waveform detected by the pickup. and a recognition means for recognizing the Kotlokoff sound based on the time sequence of the pulse train of the comparison result signal of the level comparison means. There is.

An embodiment of the present invention will be described in detail below.

FIG. 1 is a block diagram showing the configuration of an apparatus according to an embodiment of the present invention.

In FIG. 1, 1 is a pickup that detects "sound or vibration generated from blood vessels." The signal detected by the pickup 1 is input to an amplifier 2, and the detection signal amplified by this amplifier 2 has a peak value. The signal is input to the hold circuit 3 and is also added to the positive input of the level comparison means 4. Further, the output signal of the peak value hold circuit 3 is added to the negative input of the level comparison means 4, and the output of the level comparison means 4 is inputted to the recognition means 5 constituted by logic and time management circuits. The recognition means 5 receives the pulse train of the comparison result signal from the level comparison means 4, identifies Korotkoff sounds, and outputs a Korotkoff sound recognition signal f, which is transmitted to the systolic and diastolic blood pressure recognition circuit (not shown) of the electronic blood pressure monitor. ) will be introduced. Further, a control signal is input from the recognition means 5 to a reset signal generation circuit 6, and the hold value of the peak value hold circuit 3 is reset by the output of the circuit 6.

In the above configuration, "sound or vibration generated from blood vessels" detected by pickup 1
The signal obtained by amplifying the signal of
It is detected as a signal having an output waveform as shown in Figures A to D. In FIG. 2, signal A is a signal waveform detected in a pressure region higher than systolic blood pressure, signal B is a signal waveform detected at systolic blood pressure, and signal C is a signal waveform detected near diastolic blood pressure. The signal D is a signal waveform detected in a pressure region lower than the diastolic blood pressure.

The detection signal detected by the pickup 1 and then amplified by the amplifier 2 as described above is input to the peak value hold circuit 3, and the peak value of the detection signal is held by the peak value hold circuit 3. Depending on the area, the signal A'~ shown in Figure 3
D' (a signal holding the maximum value of the signals A to D shown in FIG. 2) is output from the hold circuit 3, and this signal is applied to the negative input of the level comparing means 4. It is compared with the level of the output signal of amplifier 2 applied to the side input.
The appearance of each signal waveform at this time is shown in Figure 4, and the signal waveforms A'' to D'' in Figure 4 are superimposed to make it easier to compare the levels of each signal waveform shown in Figures 2 and 3. The solid line waveform in Figure 4 is the detection signal waveform shown in Figure 2, and the broken line waveform is the hold circuit output waveform shown in Figure 3, which are slightly shifted for ease of viewing. . The level comparing means 4 which compares the levels of the above two input signals outputs signals A to D shown in FIG. 5 as output pulses as a result of the comparison.
Output. This output pulse is sent to the next stage recognition means 5.
The recognition means 5 recognizes the signal waveforms B and C in FIG. 5 as Korotkoff sounds.

More specifically, when a sharp negative wave characteristic of a Korotkoff sound occurs, the level comparison means 4 shows a difference of 5 milliseconds to
A pulse output with a short duration of several tens of milliseconds appears,
Immediately after that, due to the presence of Korotkoff sound spikes, a relatively long pulse with a time width of 200 to 300 milliseconds appears until the peak value hold circuit 3 is reset, as will be described later. 5
Signal waveforms B and C) in the figure. In addition, in the case of only a pressure pulse wave, since there is one peak value on the waveform, only pulses with a relatively long time width are generated (signal waveforms A and D in FIG. 5). That is, the recognition means 5 recognizes that the comparison result pulse output from the level comparison means 4 is 200~
If only one pulse output with a time width of 300 milliseconds appears, it is recognized as a pressure pulse wave, and as shown in Fig. 5B.
Or, if a pulse output with a short time width of several milliseconds to several tens of milliseconds appears, and then a pulse output with a long time width of 200 to 300 milliseconds appears after a similar time interval, as shown in C, it is considered a Korotkoff sound. It operates to recognize and output a recognition pulse. Furthermore, if only one or several pulses with a short time width occur in succession, it is noise.

The recognition means 5 includes, for example, retriggerable monostable multivibrators 11, 12, as shown in FIG.
13, flip-flop circuits 14 and 15, AND gates 16 to 18, OR gate 19, inverter circuits 20 to 24, and single pulse generation circuit 25. The output pulse width of the monostable multivibrator 11 is set to T1 seconds (a predetermined value of about 200 to 300 milliseconds), and the output pulse width of the monostable multivibrator 12 is set to T2 seconds (several millimeters to tens of milliseconds). (predetermined value).

If the output of the level comparison means 4 has a waveform as shown in FIG. 5 A or D, the signal is input to the recognition means 5, and the monostable multivibrators 11 and 12 are triggered at the rising edge of the signal A or D, respectively. The monostable multivibrator 1
From 1 and 12, the constant pulse width T1 seconds and
Signals b, c having T2 seconds are output. The AND gate 16 is opened due to the high level output signal C of the monostable multivibrator 12, but within this high level period T2 seconds, the signals A and D are
does not change to a low level, so flip-flop 1
4 is not set, so flip-flop 15 remains reset and AND gate 17 remains closed. Therefore, after T1 seconds, the output b of the monostable multivibrator 11 changes to a low level,
The output is applied to the AND gate 17 via the inverter 20, but due to the closed state of the AND gate 17, the monostable multivibrator 13 is not triggered, and the detection output f remains in a low level state. No sound detection signal is output.

Next, when the output of the level comparison means 4 has a waveform as shown in FIG. 5B or C, each of the monostable multivibrators 11 and 12 is triggered at the rising edge of the first pulse of the signal waveform a shown in FIG. The monostable multivibrators 11 and 12
As a result, output signals b and c having constant pulse widths T1 seconds and T2 seconds, respectively, are output. Next, since the signal a falls to a low level within T2 seconds after the first pulse of the signal a rises, this low level signal is input to the AND gate 16 via the inverter 22, and the monostable multivibrator 12 AND gate 1 which is in the open state due to the high level signal of the output c of
The output of the flip-flop circuit 14 becomes high level and the flip-flop circuit 14 is set.
The set output d of becomes high level (Fig. 7d),
AND gate 18 becomes open. Then T2
When the next pulse of signal a rises to a high level within seconds, the signal is applied to the set input of flip-flop circuit 15 through AND gate 18, and flip-flop circuit 15 is set;
The set output e becomes high level (FIG. 7e), and the AND gate 17 becomes open. Next, when the output c of the monostable multivibrator 12 changes to a low level after T2 seconds have elapsed, this signal is applied to the reset terminal of the flip-flop circuit 14 via the inverter 21, and the flip-flop 14 is reset. Furthermore, when the output b of the monostable multivibrator 11 changes to a low level after T1 seconds have elapsed, this signal is given to the AND gate 17 via the inverter 20, and the output of the AND gate 17 changes to a high level. The multivibrator 13 is triggered and an output signal f of a predetermined width is derived as the Korotkoff sound detection output (FIG. 7f). Further, this signal f is passed through the inverter 24, the single pulse generating circuit 25, and the OR gate 19 to the flip-flop circuit 15.
The flip-flop circuit 15 is reset at the falling edge of the detection output f, and the falling signal of the monostable multivibrator 11 is fed as a control signal to the reset signal generating circuit 6 described above, and the peak value hold circuit The hold value of 3 is reset.

Further, when the output of the level comparing means 4 is a series of short pulses due to noise or the like, the falling signal of the second and subsequent input pulses a is inputted to the reset terminal of the flip-flop circuit 15 via the inverter 23 and the OR gate 19. If the flip-flop circuit 15 has been set first, its state is reset, and thereafter the AND gate 17 is closed and the detection signal f is not output.

As described above, the Korotkoff sound detection signal is generated only when the second pulse is generated within T2 seconds after the rise of the pulse signal of the output a of the level comparison means 4 and the pulse remains at a high level until T1 seconds have elapsed. An output pulse of f will be derived.

As described above, according to the present invention, when identifying Korotkoff sounds from "sounds or vibrations generated from blood vessels," it is possible to identify the sharp negative waves that are characteristic of Korotkoff sounds without using a filter that limits the frequency. Since the system detects spikes and identifies Korotkoff sounds based on waveform characteristics, it is possible to reliably identify Korotkoff sounds for any test subject with any main constituent frequencies of Korotkoff sounds. It is possible to detect Korotkoff sounds, and it is also possible to effectively identify Korotkoff sounds even in the case of noise having the same frequency component as the component frequency of the Korotkoff sounds and pressure pulse waves with large amplitudes.

Furthermore, according to the present invention, when detecting Korotkoff sounds, the peak value of the signal waveform itself is captured and compared with the original waveform, and unlike conventional methods, discrimination based on signal strength is not performed, so that the peak value of the signal waveform itself is captured and compared with the original waveform. It is possible to extract the waveform characteristics of the Korotkoff sound as a pulse train regardless of the amplitude of the signal, the depth of the negative wave, the sharpness of the spike, etc. without the need to set a threshold, and as a result, the Korotkoff sound can be stabilized. can be reliably identified.

In the above embodiment, the peak value hold circuit 3 is reset after completely holding the peak value voltage for a certain period of time, but the present invention is not limited to this, and the present invention is not limited to this. The peak voltage may be lowered with an appropriate time constant larger than the fall of the spike, and returned to the zero level before the next signal is input. In this case, the peak value hold reset signal generating circuit 6 is not required.

Furthermore, although the case where a flip-flop circuit and a monostable multivibrator are used as an example of the recognition means 5 has been described, the present invention is not limited to this.
For example, a similar recognition means as described above may be programmed using a microcomputer to set similar functions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an apparatus according to an embodiment of the present invention, FIGS. 2 to 5 are signal waveform diagrams of each part thereof, and FIG. 6 is a block diagram showing a specific example of the recognition means of the present invention. FIG. 7 is a signal waveform diagram for explaining the operation. 1...Picking up, 3...Peak value holding means, 4...Level comparison means, 5...Recognition means.

Claims (1)

[Claims] 1 A pickup for detecting sound or vibration generated from blood vessels, a peak value hold means for holding the peak value of the signal waveform detected by the pickup, and an output signal of the peak value hold means and the level of the signal detected by the pickup. and a level comparing means for outputting a pulse when the level of the signal detected by the pickup is lower than the level of the output signal of the peak value holding means; An electronic blood pressure monitor characterized in that it is equipped with recognition means for recognizing Korotkoff sounds when pulses with a long duration are output within hours.