JPH0318890B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention detects Korotkoff sounds, their expression,
The present invention relates to an electronic blood pressure monitor that measures blood pressure using extinction.

[Background technology]

The currently common standard clinical method for pessimistic blood pressure measurement is based on Korotkoff's auscultation method.

This method involves wrapping a cuff around the upper arm of the human body, injecting air into the cuff, and lowering the expected systolic blood pressure by 20
Apply high pressure to ~30mmHg to compress the artery and stop blood flow. Next, increase the air pressure inside the cuff by 2 to 3 mmHg/
Gradually exhaust the air at a speed of sec. Eventually, the artery opens slightly and blood flows out, producing a damped vibration sound called Korotkoff sound in the lateral direction of the blood vessel wall. This Korotkoff sound continues to occur in synchronization with the pulse, but eventually disappears when the artery is sufficiently opened and the blood flow becomes constant. The arm cuff pressure when this Korotkoff sound occurs is the systolic blood pressure, and the arm cuff pressure before it disappears, that is, when the last Korotkoff sound occurs, is the diastolic blood pressure.

By the way, when blood pressure measurement can be performed under good conditions, Korotkoff sounds are classified into the following four phases as shown in FIG. 2a. At first, a clear tapping sound is generated (Phase 1), then it becomes a dull sound (Phase 2), and then it becomes a clear groove sound again (Phase 3).
phase). Then, it suddenly becomes a small dull sound (phase 4) and disappears. However, if blood pressure is measured under poor conditions, the second phase of dullness will not occur. Therefore, detecting whether dullness has occurred and notifying the user through a display or the like is very useful in the sense of notifying whether the blood pressure measurement was performed in good conditions.

[Purpose of the invention]

The present invention has been provided in view of the above-mentioned points, and an object of the present invention is to detect voiced sounds that can be used as an indicator of whether blood pressure measurement has been carried out in good condition. It is an object of the present invention to provide an electronic blood pressure monitor that can detect dull sounds without malfunctioning due to noise.

[Disclosure of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. Figure 1 shows a block diagram. In the figure, 1 is a detection microphone which is a conversion means that collects the Korotkoff sound obtained by compressing an artery with a cuff and converts it into an electrical signal, and 2 is a detection microphone 1. This is a bandpass filter that discriminates the electrical signal from the oscilloscope into a discrimination signal as shown in FIG. 2a, which includes the Korotkoff sound signal. 3 is a Korotkoff sound (K sound) which compares the discrimination signal from the band filter 2 with a preset comparator level and outputs a Korotkoff sound signal as shown in FIG. 2b.
It is a comparator. That is, if the discrimination signal is greater than the comparator level of the reference voltage, it is output as a Korotkoff sound signal. 4 is a monostable multivibrator, which expands the Korotkoff sound signal from the Korotkoff sound comparator 3 into a pulse having a certain time width, as shown in FIG.
This is outputted to the Korotkoff sound output terminal 5 as a Korotkoff sound pulse signal.

By the way, regarding the detection of voiced sounds, the difference between voiced sounds and other Korotkoff sounds is that a weak signal exists for a certain period of time in the latter half of the Korotkoff sound signal, as shown in FIG. 2a. This weak signal is the cause of the sound being heard as dullness, and is consistent with the sense of hearing. The present invention attempts to detect voiced sounds using Korotkoff sound signals and time management based on the Korotkoff sound signals. 6 is a gate signal generation circuit, which generates a signal for a certain period (about 40 msec) after a certain time (about 50 msec) from the rise of the Korotkoff sound pulse signal from the monostable multivibrator 4.
A gate signal as shown in FIG. 2 d having a period of time of ~60 msec) and a gate as shown in FIG. Generate a signal.
Reference numeral 7 denotes a voiced sound comparator which compares the discrimination signal from the band filter 2 with a preset comparator level and outputs a signal as shown in FIG. 2f. 8 and 9 are AND gates, which take the AND of the output of the voiced sound comparator 7 and the gate signal from the gate signal generation circuit 6, and the output of each AND gate 8 and 9 is connected to the monostable multivibrator 10, 11 respectively. The monostable multivibrators 10 and 11 output pulse signals having a time width longer than the time width of the gate signal from the gate signal generation circuit 6 (FIG. 2 i, j).
These, voiced sound comparator 7, and gate 8,
9 and monostable multivibrators 10 and 11 constitute a waveform conversion means. 12 is an AND gate serving as a logical product means, which logically ANDs the output pulse signals of both monostable multivibrators 10 and 11, and outputs the output as a voiced sound signal to the voiced sound output terminal 13;
Thereafter, it is processed as appropriate for notification purposes and the like. Furthermore, the first
A to k in the figure and FIG. 2 correspond to each other.

The detection microphone 1 detects the Korotkoff sound from the cuff, and the discrimination signal as shown in FIG.
The output from the Korotkoff sound comparator 3 as shown in FIG. 2b is outputted by the monostable multivibrator 4 as a pulse signal as shown in FIG. The gate signals shown in FIG.
is input to one input end of the . On the other hand, the output from the voiced sound comparator 7 as shown in FIG. The AND gates 8 and 9 are used to logically multiply the second
A signal is output after a certain period of time has elapsed from the rise of the Korotkoff sound as shown in Figures g and h. This signal is transmitted to the second monostable multivibrator 10, 11, respectively.
As shown in Figures i and j, expanded pulse signals are output, and both pulse signals are passed through the AND gate 12 to output a pulse signal as a voiced sound signal as shown in Figure 2k. In other words, if there are signals detected together within the time span of both gate signals, it is assumed that a voiced sound is occurring, and the voiced sound signal is reliably output. Therefore, unlike the case of detecting voiced sounds using only one gate signal after the rise of the Korotkoff sound, it is possible to detect voiced sounds without detection errors due to noise.

FIG. 3 shows an embodiment of the combined invention, which includes a gate comparator 14 and a monostable multivibrator 15.
The output of the monostable multivibrator 15 is input to the gate signal generation circuit 6.
That is, the Korotkoff sound when a voiced sound is generated is characterized by a high signal level. This fact is utilized to further improve malfunctions caused by noise. In the previous embodiment, the Korotkoff sound signal detected for blood pressure measurement was used as the trigger for creating the two gate signals, but the comparator level of the Korotkoff sound comparator 3 for detecting this Korotkoff sound signal is It is set so that small signals can be detected when the expression or disappearance occurs. However, the signal level when voiced sounds occur is considerably higher than that. Therefore, a gate comparator 14 is provided which is set to a reference voltage comparator level higher than the reference voltage comparator level of the Korotkoff sound comparator 3, and this gate comparator 14 compares and detects the discrimination signal from the band filter 2. The reliability of voiced sound detection is improved by extending the output with the monostable multivibrator 15 and using this signal as a gate reference pulse to trigger the gate signal generation circuit 6, that is, to detect the rising edge of the Korotkoff sound signal. It is. In other words, by setting the detection level high in the gate comparator 14, malfunctions due to noise can be prevented. The other circuit configurations are the same as in the previous embodiment.

〔Effect of the invention〕

As mentioned above, the specified invention relates to an electronic blood pressure monitor,
A first gate signal having a predetermined time width is generated after a predetermined time from the rise of the Korotkoff sound signal from the detection means, and a second gate signal having a predetermined time width at the fall of the first gate signal. A gate signal generation circuit generates a pulse signal having a time width longer than that of the first and second gate signals by ANDing the discrimination signal from the filter and the first and second gate signals of the gate signal generation circuit, respectively. This device is equipped with a waveform converting means that outputs the pulse signal as , and an AND means that ANDs both pulse signals from the waveform converting means and outputs the voiced sound signal included in the Korotkoff sound. The first and second gate signals having different time zones and the discrimination signal from the filter are logically ANDed, and the output of this logical product is output for a time span longer than that of the first and second gate signals. By extending these pulse signals and ANDing them, if both signals are obtained within the time of the first and second gate signals, it is assumed that there is a voiced sound and a voiced sound signal is output. ,
Therefore, it is possible to reliably detect the second-phase dullness of the Korotkoff sound, which is an indicator of whether blood pressure measurement has been performed in good conditions.

In addition, the combined invention is capable of reliably detecting voiced sounds like the above-mentioned specified invention, and also gates the discrimination signal from the filter by setting the reference voltage of the comparator level higher than the comparator level of the reference voltage of the Korotkoff sound comparator. A gate comparator is used to output the signal reference pulse, and the reference pulse from the gate comparator is input to the gate signal generation circuit. By setting the gate comparator's detection level high, it is possible to detect weak signals such as noise. This has the effect that malfunctions due to noise can be prevented without detecting any signals.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an embodiment of the specified invention, Figure 2 is a block diagram of an embodiment of the specified invention.
The figure is a time chart same as the above, and FIG. 3 is a block diagram of an embodiment of the merged invention. 2 is a band filter, 3 is a Korotkoff sound comparator, 6 is a gate signal generation circuit, and 14 is a gate comparator.

Claims (1)

[Scope of Claims] 1. A conversion means for converting Korotkoff sounds emitted from a compressed artery into an electrical signal, a filter for discriminating the electrical signal from the conversion means into a discrimination signal including the Korotkoff sounds, and a discrimination signal from the filter. An electronic sphygmomanometer has a detection means for detecting a Korotkoff sound signal by comparing it with a reference voltage, and measures blood pressure by the appearance or disappearance of the Korotkoff sound signal from the detection means. a gate signal generation circuit that generates a first gate signal having a predetermined time width after a certain time from the rise of the signal and a second gate signal having a predetermined time width at the fall of the first gate signal; , a waveform conversion means for outputting an output obtained by logically multiplying the discrimination signal from the filter and the first and second gate signals of the gate signal generation circuit as pulse signals having a time width longer than that of the first and second gate signals, respectively. and a logical product means for logically multiplying both pulse signals from the waveform converting means and outputting a voiced sound signal included in Korotkoff sounds. 2. A conversion means for converting Korotkoff sounds emitted from a compressed artery into an electrical signal, a filter for discriminating the electrical signal from the conversion means into a discrimination signal including the Korotkoff sounds, and a comparison of the discrimination signal from the filter with a reference voltage. An electronic sphygmomanometer comprising a Korotkoff sound comparator for detecting a Korotkoff sound signal by means of detection means, and in which blood pressure is measured by the appearance or disappearance of the Korotkoff sound signal from the detection means, the comparator level of the reference voltage of the Korotkoff sound comparator is a gate comparator which is set to a reference voltage of a high comparator level and outputs the discrimination signal from the filter as a gate reference pulse; and a second gate signal having a predetermined time width at the rising edge of the first gate signal; The outputs obtained by ANDing with the gate signals of 2 and 2 are respectively
A waveform converting means for outputting a pulse signal having a time width longer than that of the second gate signal, and an AND means for logically multiplying both pulse signals from the waveform converting means and outputting a voiced sound signal included in the Korotkoff sound. An electronic blood pressure monitor characterized by comprising: