JPH02295543A - Automatic blood pressure measuring device - Google Patents

Abstract

PURPOSE:To cancel the erroneous measurement of blood pressure caused by noise by determining the peak blood pressure value and/or average blood pressure value of an organ based on the waveform change of a central side beating tone to be detected by a central side beating tone detecting means. CONSTITUTION:From the change in the waveform of the central side beating tone detected by any one of piezoelectric sheets 18, 20 and 22 which are arranged in the central side end part of a cuff 10, the peak blood pressure value and average blood pressure value are determined. Only when the blood pressure value is not different from the blood pressure value determined based on a Korotkoff tone detected by piezoelectric sheets 24, 26 and 28 in a center in the breadwise direction of the cuff 10, the blood pressure is displayed on a display 48. Thus, by comparing the blood pressure value, which is determined based on the waveform change of the central side beating tone, with the blood pressure value determined based on the Korotkoff tone, the possibility of the blood pressure measuring value based on the korotkoff tone is determined. Then, since the reliability of the measured value is improved, it can be canceled that the erroneous blood pressure measurement is executed by the noise of the same frequency component as the Korotkoff tone or the noise generated in the same period of the Korotkoff tone.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an automatic blood pressure measuring device that automatically measures the blood pressure value of a living body.

Conventional technology A type of automatic blood pressure measuring device includes a cuff that is attached to a part of a living body to compress an artery within that living body, and a Korotkoff sound that detects the Korotkoff sound generated from the artery during the compression process by the cuff. Some devices include a detection means and a blood pressure value determination means that automatically determines a blood pressure value based on the Korotkoff sounds detected by the Korotkoff sound detection means. In such automatic blood pressure measuring devices, Korotkoff sound detection means, such as a microphone, is usually disposed at the distal edge of the cuff, and detects, for example, a series of Korotkoff sounds that occur as pressure drops across the cuff. Once detected, the cuff pressure at which the first of these Korotkoff sounds occurs is determined to be the systolic pressure, and the cuff pressure at which the last Korotkoff sound occurs is determined to be the diastolic pressure. It is configured.

Problems to be Solved by the Invention However, in the conventional automatic blood pressure measuring device as described above,
Noise is removed by sampling the Korotkoff sounds through a bandpass filter that blocks the passage of frequency components other than those that make up the Korotkoff sounds, or by sampling the Korotkoff sounds through a time window triggered by an electrocardiogram. However, noise with the same frequency components as the Korotkoff sounds or noise that occurred at the same time as the Korotkoff sounds could lead to incorrect blood pressure measurements.

The present invention has been made against the background of the above circumstances,
The objective is to provide an automatic blood pressure measuring device that can determine blood pressure values without using Korotkoff sounds.

Means for Solving the Problems The inventors of the present invention have conducted various studies based on the above circumstances, and have developed a waveform of a central pulse sound detected by a pulse sound detecting means disposed at the central end edge of the cuff. We found that there are characteristic changes around the systolic and mean blood pressure values of living organisms. The present invention has been made based on this knowledge.

That is, the gist of the present invention is to provide a cuff that is attached to a part of a living body to compress an artery in that living body, and to measure blood pressure based on the pulse sound generated from the artery during the compression process by the cuff. An automatic blood pressure measuring device of a type that automatically determines a blood pressure value, the device comprising: (a) central pulse sound detection means disposed at the central end of the inner circumferential surface of the cuff to detect central pulse sounds; , (b) blood pressure value determination means for determining the systolic blood pressure value and/or the mean blood pressure value of the living body based on the waveform change of the central pulse sound detected by the central pulse sound detection means. be.

Effects and Effects of the Invention With this, the blood pressure value determination means can determine the systolic blood pressure value and/or the average blood pressure value of the living body based on the waveform change of the central pulse sound detected by the central pulse sound detection means. It is determined. For this reason, for example, in an automatic blood pressure measuring device that automatically determines the blood pressure value based on the occurrence and disappearance of Korotkoff sounds, the blood pressure value determined based on the waveform change of the central pulse sound is not determined based on the Korotkoff sounds. By comparing the blood pressure value with the measured blood pressure value, it is possible to determine whether the blood pressure measurement based on the Korotkoff sounds is accurate or not, and the reliability of the measurement is increased. Therefore, it is possible to prevent incorrect blood pressure measurement from being performed due to noise having the same frequency component as the Korotkoff sound or noise occurring at the same time as the Korotkoff sound.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

In FIG. 1, 10 is a band-shaped cuff that is attached to a part of a living body, for example, the upper arm, to compress it;
A rubber bag connected to piping 12 is provided inside. A pressure control valve 14 connected to this piping 12 prevents exhaust from the cuff 10 when the pressure of the cuff 10 is increased, and at the same time prevents exhaust from the bomb 16 according to a drive signal from a control device 46 to be described later.
The compressed air sent from
During slow pressure reduction at 0, compressed air from pump 16 flows into cuff 1.
The cuff 10 is configured to prevent the compressed air from flowing into the cuff 10 and at the same time allow the compressed air in the cuff 10 to gradually flow out to the atmosphere. On the inner circumferential surface of the cuff 10, a piezoelectric sheet (
In this example, a total of 6) are placed at multiple locations.
The piezoelectric sheets 18, 20, and 22 are used exclusively to detect central side (arterial upstream side) pulse sounds, and are arranged in the circumferential direction at the central side end edge of the cuff IO. Furthermore, the piezoelectric sheets 24, 26, and 28 are used exclusively for detecting Korotkoff sounds, and correspond to the three piezoelectric sheets 1, 2o, and 22 at the center of the width direction of the cuff 10. Arranged circumferentially. In this embodiment, the piezoelectric sheets 18, 20, and 22 correspond to central pulse sound detection means, and the piezoelectric sheets 24, 26, and 28 correspond to Korotkoff sound detection means.

The signals output from the piezoelectric sheets 18, 20, 22, 24, 26, 28 are passed through the bandpass filter 3o to the A/D
The signal is input to the converter 32, where it is converted into a digital signal and then supplied to the CPU 34. Above band filter 3
0 has a cutoff frequency that allows only a band containing frequency components constituting pulse sounds and Korotkoff sounds generated from the artery compressed by the cuff 10 in synchronization with the heartbeat to pass through. In addition, the pressure sensor 3 connected to the pipe 12
The pressure signal output from 6 is converted into a digital signal by an A/D converter 38, and then supplied to the CPU 34.

The CPU 34 constitutes a control device (so-called microcomputer) 46 together with the ROM 4 0SRAM 4 2 and the interface circuit 44, and the RA
Utilizing the primary memory function of the M42, the input signal is processed according to a program stored in the ROM 40 in advance, and the pressure control valve 14 and the pump 16 are driven, and the blood pressure value is determined and displayed according to the blood pressure determination algorithm stored in advance. display on the device 48.

Next, the operation of the control device 46 will be explained according to the flowchart shown in FIG. First, the cuff 10 has its piezoelectric seats l8, 20, 22,
24, 26, and 28 are attached to a part of the living body so as to be located on the artery. Next, when a starting switch (not shown) is operated, step 31 is executed, the pump 16 is started, and the air from the pump 16 is force-fed into the cuff 10 by the pressure control valve 14. As a result, the pressure inside the cuff 10 is rapidly increased. In step S2, it is determined whether the actual pressure P within the cuff lO detected by the pressure sensor 36 has reached a predetermined pressure increase target value Pm. Initially, it does not reach the target pressure increase value Pm, so steps S1 and S2 are repeatedly executed, but when it is determined that the pressure P within the cuff 10 has reached the target pressure increase value Pm,
In step S3, the bomb 16 is stopped, and the pressure control valve 14 starts to gradually exhaust the air in the cuff 10 to the outside. This allows the pressure of the cuff 10 to increase at a rate suitable for blood pressure measurement, for example 2 to 3.
Blood pressure is slowly lowered to mHg/see.

When the slow pressure lowering process as described above is started, step S
At step 4, it is determined whether or not a pulse sound is generated from the artery based on any of the signals output from the piezoelectric sheets 18, 20, 22, 24, 26, and 28. If it is determined in step S4 that no pulse sound has occurred, the system is put on standby, but if it is determined that a pulse sound has occurred, the Korotkoff sound sampling routine of step S5 is executed. That is, in step SSI of FIG. 3, each piezoelectric sea}
After the central pulse sound data detected by the piezoelectric sheets 24, 26, and 28 and the Korotkoff sound data detected by the piezoelectric sheets 24, 26, and 28 are stored, in step S52, the cuff 10 is The central pulse sounds detected by the piezoelectric sheets 18, 20, and 22 located at the central edge are compared, and the maximum pulse sound sensor that outputs the largest central pulse sound is determined. In the subsequent step S83, the optimum Korotkoff sound sensor located among the piezoelectric sheets 24, 26, and 28 at the center in the width direction of the cuff 10 corresponding to the maximum pulse sound sensor is determined. For example, if the largest pulse sound is detected by the piezoelectric sheet 20 among the piezoelectric sheets 18, 20, 22 disposed at the central edge of the cuff lO, the piezoelectric sheet 20 detects the largest pulse sound. The piezoelectric sheet 26 that is determined as a sensor and is disposed corresponding to the piezoelectric sheet 20 is determined as the optimum position Korotkoff sound sensor.

In step SS4, it is determined whether the Korotkoff sound detected by the optimal position Korotkoff sound sensor is located within a time window that is opened for a predetermined time after a predetermined time from the generation time of the pulse sound detected by the maximum pulse sound sensor. will be judged.

Note that the above-mentioned time window is opened only during the normal Korotkoff sound generation time period to remove noise in other time periods, and is opened, for example, 50 ms after the central pulse sound generation time and closed 350 n+s later. Furthermore, the pulse sounds and Korotkoff sounds that exceed a predetermined level are recognized.

If the Korotkoff sound detected by the optimum position Korotkoff sound sensor is not located within the time window, the routine of FIG. 3 is terminated. However, if the Korotkoff sound is located within the time window, it is a Korotkoff sound that occurred during a normal generation time, so in step SS5, the time of occurrence of the Korotkoff sound and the cuff 10 at that time are determined. Pressure is memorized.

When the Korotkoff sound sampling routine in step SS5 is completed as described above, a blood pressure value is determined in step S6 of FIG. 2 according to a predetermined blood pressure determination algorithm. That is, the time point at which the first Korotkoff sound occurs and the time point at which the last Korotkoff sound occurs among a series of Korotkoff sounds that occur as the pressure drops in the cuff 10 are determined;
The cuff pressure at the time when the first Korotkoff sound occurs is determined as the systolic blood pressure value, and the cuff pressure at the time when the last Korotkoff sound occurs is determined as the diastolic blood pressure value.

Furthermore, an average blood pressure value is calculated from these systolic blood pressure values and diastolic blood pressure values. In the subsequent step S7, it is determined whether the blood pressure measurement has been completed, in other words, whether the systolic and diastolic blood pressure values have been determined in the step S6. In step 7, if the systolic and diastolic blood pressure values have not yet been determined, such as because the final Korotkoff sound has not been recognized, steps 34 and subsequent steps are executed again. However, when it is determined that the systolic and diastolic blood pressure values are determined and the blood pressure measurement is completed, the cuff 10 is immediately evacuated rapidly in step S8 and the compression by the cuff 10 is released, and then, in step S9, the piezoelectric sheet 20 The systolic blood pressure value and the mean blood pressure value are determined based on the pulse sound data detected and stored in step SS1. That is, as shown in Fig. 4, the central pulse sound has the characteristic that the amplitude from the baseline to the 10th side occurs near the systolic blood pressure value, and the amplitude from the baseline to the 1st side disappears near the mean blood pressure value. Therefore, in step S9, the time point at which the amplitude to the side occurs is detected according to a predetermined algorithm,
While the cuff pressure at this point is determined as the systolic blood pressure value,
The point at which the amplitude to one side disappears is detected according to a predetermined algorithm, and the cuff pressure at this point is determined as the mean blood pressure value.

In step 510, the systolic blood pressure value and mean blood pressure value determined based on the central pulse sounds as described above are compared with the systolic blood pressure value and mean blood pressure value determined based on the Korotkoff sounds in step S6. If it is determined that the difference between them is greater than or equal to a predetermined criterion value, an abnormality will be displayed on the display 48, but if it is less than the criterion value, it will be determined based on the Korotkoff sound in step S6. The systolic blood pressure value, average blood pressure value, and diastolic blood pressure value are displayed on the display 48.

In the automatic blood pressure measuring device configured as above,
In step S9, the systolic blood pressure value and the mean blood pressure value are determined from the change in the waveform of the central pulse sound detected by any of the piezoelectric sheets 18, 20, and 22 disposed at the central end edge of the cuff lO. Since the blood pressure value is displayed only when it does not differ from the blood pressure value determined based on the Korotkoff sounds, the reliability of the blood pressure measurement based on the Korotkoff sounds is increased. That is, by comparing the blood pressure value determined based on the waveform change of the central pulse sound with the blood pressure value determined based on the Korotkoff sound, the validity of the blood pressure measurement value based on the Korotkoff sound is determined, and the reliability of the measurement is determined. This improves the sensitivity of blood pressure, which eliminates the possibility of erroneous blood pressure measurements caused by noise with the same frequency component as the Korotkoff sound or noise that occurs at the same time as the Korotkoff sound.

Further, according to this embodiment, the cuff 10 attached to the upper arm
Piezoelectric sheets 18, 20, 2 arranged at the center side edge of
2 is pressed against the upper arm in a stable state compared to when it is provided at the distal end edge, so there is less friction with the skin due to body movement or displacement of the cuff, and the central pulse Systolic blood pressure values and mean blood pressure values determined based on sound have the advantage of relatively high reliability.

Further, according to this embodiment, the piezoelectric sheets 24, 26, and 28 for detecting Korotkoff sounds are arranged at the center in the width direction of the cuff 10, which has a high and stable pressing force against the living body. For example, as shown at the bottom of Figure 5,
Compared to the conventional case (upper part of FIG. 5) in which a Korotkoff sound sensor for detecting Korotkoff sounds is provided at the distal edge of the cuff (upper part of FIG. 5), Korotkoff sounds are detected at a higher level. Therefore, even if the subject's pulse is weak,
Blood pressure values can be determined stably.

Furthermore, according to this embodiment, the piezoelectric sheets 24, 26, and 28 for detecting Korotkoff sounds are located at the center in the width direction where they can be closer to the artery in the living body than at the edge of the cuff 10. Since it is placed in the same position, it has the advantage that the influence of deviation from the artery is relatively small. When a microphone is installed at the edge of the cuff 10, if there is a misalignment between the microphone installation position and the point directly above the artery, the influence of muscles and bones on the propagation of Korotkoff sounds will be large, resulting in a signal level is easy to attenuate.

Further, according to this embodiment, piezoelectric sheets 18, 20, and 22 are arranged in the circumferential direction at the central end edge of the cuff 10 for exclusively detecting central side (arterial upstream side) pulse sounds. , piezoelectric sheets 24, 26, 28 exclusively for detecting Korotkoff sounds are arranged in the circumferential direction in the widthwise center of the cuff lO in correspondence with the three piezoelectric sheets l8, 20, 22. This has the advantage that blood pressure can be measured reliably even if there are variations in the position at which the cuff 10 is attached, and no skill is required to attach the cuff.

Further, according to the present embodiment, a piezoelectric sensor located corresponding to the maximum pulse sound sensor is placed within a time window that is opened for a predetermined time after a predetermined time from the generation time of the pulse sound detected by the maximum pulse sound sensor. Only when the Korotkoff sound detected by the sheet is located, it is recognized as a Korotkoff sound and used for blood pressure measurement, so noise caused by the subject's body movement or contact with the cuff 10 is suitably removed, and blood pressure measurement is performed. This has the advantage of increasing reliability.

Further, according to the present embodiment, the piezoelectric sheets 1B, 20, and 22 provided at the central end edge of the cuff 10 are located corresponding to the maximum pulse sound sensor that detects the maximum pulse sound. The Korotkoff sound detected by the piezoelectric sheet after a predetermined time from the time when the maximum pulse sound occurs is used for blood pressure measurement. There is an advantage that the sheet can be easily selected.

An embodiment of the present invention has been described above based on the drawings.
The invention also applies in other aspects.

For example, instead of the piezoelectric sheets 18, 20, 22, 24, 26, 28 used in the embodiments described above, a microphone capable of detecting pulse sounds or Korotkoff sounds may be used.

Further, in the above embodiment, the piezoelectric sheets 18, 20, 22 for detecting central pulse sounds and the piezoelectric sheets 24, 26, 28 for detecting Korotkoff sounds are provided. Only one piezoelectric sheet for detecting lateral pulse sounds may be provided at the proximal edge of the cuff IO.

The above-mentioned embodiment is merely one embodiment of the present invention, and various changes can be made to the present invention based on the knowledge of those skilled in the art without departing from the purpose thereof.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the configuration of an embodiment of the present invention. 2 and 3 are flowcharts illustrating the operation of the embodiment of FIG. 1. Figure 4 shows the first
It is a figure which shows the waveform change with respect to cuff pressure of the central side pulse sound in the Example of a figure. FIG. 5 is a diagram showing the Korotkoff sounds detected by the embodiment of FIG. 1 in comparison with the conventional one. 10: Cuff 24, 26, 28: Piezoelectric sheet (Korotkoff sound detection means) 46: Control device W (blood pressure value determination means) Applicant Korin Electronics Co., Ltd.

Claims (1)

[Scope of Claims] A cuff is attached to a part of a living body to compress an artery in the living body, and the blood pressure value is automatically determined based on the pulse sound generated from the artery during the compression process by the cuff. An automatic blood pressure measuring device of a type that determines the blood pressure, comprising: a central pulse sound detection means disposed at a central end of the inner circumferential surface of the cuff to detect central pulse sounds; and a central pulse sound detection means. an automatic blood pressure measuring device comprising: blood pressure value determining means for determining a systolic blood pressure value and/or an average blood pressure value of the living body based on a waveform change of a central pulse sound detected by the blood pressure measuring device.