JPS59164037A - Pulse discriminating method and blood pressure measuring apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a pulse wave discrimination method for discriminating the fundamental wave of a pulse wave contained in pressure vibrations from pressure vibrations within a cuff that presses a part of the human body, and a pulse wave discrimination function. The present invention relates to a blood pressure measuring device equipped with a blood pressure measuring device.

There is a method that measures blood pressure based on changes in the pulse wave of seeds. This is the so-called vibration method (oscillometric method). When measuring blood pressure using this method, the fundamental wave of the pulse wave is determined from the pressure vibration of the cuff, which includes the pulse wave (fundamental wave), its harmonics, and motion artifacts caused by the movement of the subject. It is important to remove only the blood and use it for blood pressure measurement, etc.

However, since pulse waves differ from person to person and vary within a predetermined range, blood pressure measurement devices using this method use a wideband filter with a frequency band that can pass within that range to measure pulse waves. Pulse waves had to be discriminated from other noises, and a sufficiently differentiated pulse wave could not always be obtained.

Therefore, when blood pressure is measured using the vibration method, the blood pressure is measured based on a pulse wave that still contains some noise, so the accuracy of the measured blood pressure value may be a problem or it may not be possible to measure it.

The present invention has been made in order to eliminate the above-mentioned disadvantages, and its gist is that when blood pressure is measured using the vibration method, pressure oscillations within the cuff that presses on a part of the human body, A pulse wave discrimination method that discriminates the fundamental wave of the pulse wave included in the pressure vibration, which detects the pulsation period or number of pulsations per unit time of the human body, and detects the pulsation period or number of pulsations per unit time determined in advance. Determine the actual fundamental frequency of the pulse wave corresponding to the detected pulse period or number of beats per unit time from the relationship between
A filter that passes the determined fundamental frequency is selected from a plurality of types of narrowband filters prepared in advance with different passable frequency bands, and the fundamental wave of the pulse wave is generated by passing the pressure vibration through the selected filter. It is characterized by that it obtains.

By shifting in this way, the fundamental frequency of the pulse wave, which differs for each subject, can be easily determined, and by selecting a narrow-band filter accordingly, pressure vibrations can be passed through that filter. The fundamental wave of the pulse wave with noise removed satisfactorily can be obtained. Therefore, if blood pressure is measured based on the fundamental wave of the pulse wave, the accuracy of blood pressure measurement can be greatly improved.

Here, the pulse wave included in the pressure vibration within the cuff appears in synchronization with the pulsation of the human body.

On the other hand, the Korotkoff sound (K sound) used in conventional blood pressure measurement also appears in synchronization with the pulsation of the human body, but the frequency of its fundamental wave is generally around 4QHz, and the number of pulsations of the person being measured is Or, there is no correlation at all with the beating period. However, as a result of the inventor's analysis of the frequency of the pulse wave shown in Figure 1, as shown in Figure 2, the fundamental frequency of the pulse wave has the minimum frequency of each peak; It has become clear that the linear correlation shown in FIG. 3 holds between the frequency and the number of pulsations or pulsation period per unit time of the subject. In the present invention, the pulse wave included in the pressure vibration within the cuff is based on the correlation with the pulsation period or number of pulsations of the subject.
It is of great significance that the fundamental frequency of the pulse wave collected for each subject can be easily determined. for example,
If you try to select multiple narrowband filters prepared in advance using conventional technology, it is necessary to collect pulse waves for each subject and
The fundamental frequency had to be determined using an expensive and large frequency analyzer (spectrum analyzer).

Since the pressure oscillations within the cuff are mainly composed of pulse waves, the pulsation period or number of pulsations per unit time is determined by detecting pulsations (occurrence of pulse waves) based on the pressure oscillations. Alternatively, the output signal of a well-known electrocardiograph or pulse rate monitor may be used.

The predetermined relationship shown in FIG. 3 may be prepared in advance using a functional formula, and the fundamental frequency may be calculated based on the functional formula and the vibration signal, but the predetermined relationship may be prepared as a table. The actual fundamental frequency may be determined by preparing a table in advance and performing a logical operation using the table and the actual pulse period or number of pulses per unit time.

In addition, multiple types of narrowband filters may be configured by a combination of individual filters that regulate high and low frequencies in the signal transmission path, and may have partially overlapping passable frequency bands. Of course, this is also a good thing.

On the other hand, another aspect of the present invention has been made for the purpose of providing a highly accurate blood pressure measuring device that measures blood pressure based on an accurate fundamental wave of a pulse wave. However, it is a blood pressure measuring device that includes a cuff that compresses a part of the human body and measures blood pressure based on changes in pulse waves included in pressure oscillations within the cuff. (2) a pulse rate detection means for outputting a pulse signal representing the pulse rate of the human body or the number of pulses per unit time based on the signal; and (2) a pulse rate or pulse rate per unit time determined in advance based on the pulse signal (3) a calculation means for determining the actual fundamental frequency of the pulse wave from its relationship with the fundamental frequency of the pulse wave; filter selection means for discriminating the pulse wave signal representing the pulse wave from the pressure signal by passing the pulse wave signal through the selected filter; blood pressure measuring means for determining a blood pressure value based on the blood pressure value and outputting the determined blood pressure value.

By shifting in this way, as shown in the claim correspondence diagram in FIG. Then, a filter is selected that selectively passes the signal of that fundamental frequency, and the discriminated signal is sent to the blood pressure measuring means through the filter.

Therefore, similar to the above-mentioned invention, the fundamental frequency of the pulse wave for each subject can be easily determined without using a spectrum analyzer, so a filter suitable for the pulse wave can be selected, and the accuracy of blood pressure measurement can be improved. 78 They were greatly forced to leave the country.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below based on the drawings.

In FIG. 5, 10 is a well-known long glove-shaped cuff that is wrapped around a part of the human body such as the upper part of the body or the thigh.
The cuff 10 includes an air pump 12 that pumps air into the cuff 10, a pressure sensor 14 that detects the pressure of the cuff 101';' and outputs a pressure signal SP representing the pressure, and exhausts the air inside the cuff 10. a rapid exhaust valve 16 for rapidly lowering the pressure inside the cuff 10, and a constant speed exhaust valve for gradually exhausting the air inside the cuff 10 to bring the pressure drop inside the cuff 10 to a rate of descent suitable for blood pressure measurement. 18 are connected in parallel.

Note that 20 is a throttle inserted between the constant speed exhaust valve 18 and the cuff 10 to determine the rate of pressure drop during constant speed exhaust.

The pressure signal SP passes through an amplifier 22 to a low bass filter z.
bta24. First filter 26.12 filter 28. Third
Filter 30. 4th filter 32° and waveform shaping circuit 3
4. The low-pass filter 24 filters the pressure signal S
The pressure value signal PV ((A/D converter 8
6, and the A/D converter 36 converts the pressure value represented by the pressure value signal PV into a code signal and outputs the code signal to the I10 boat 38.
supply to.

First filter 26. Second filter 28. Third filter 3
0. and the fourth filter 32 are narrow band filters with different permissible frequency bands, and as shown in FIG. 6, these bands are connected to reduce the variation range due to individual differences in the fundamental frequency of the pulse wave. is covered. In other words, the fundamental frequency of the pulse wave generally varies from 0.67 to 3.33 Hz depending on the person to be measured. 20~2.61-1
a second filter 28 with a pass tolerance band of y;
4-2. It is covered by a third filter 30 with a pass tolerance band of 0.0 Hz and a fourth filter 32 with a pass tolerance band of 0.67 to 1.41 (z). 28.30.32, when a pulse wave in its own passable band exists in the pressure signal SP, the pulse wave signal SM representing the pulse wave is sent to each port 1'l + P2) of the multiplexer 4o. P4
supply each.

The waveform shaping circuit 34 forms a pulsed tone signal PP synchronized with the pulsation (pulse) of the subject from the manually input pressure signal SP, and supplies it to the pulsation period calculation circuit 44 . That is, as shown in FIG. 1, the pressure vibration of the cuff 10 represented by the pressure signal SP is mainly composed of pulse waves generated in synchronization with the pulse rate of the subject, so that the peak Alternatively, by detecting the level near the peak, the pulse signal is shaped into the pulse signal shown in FIG.
4.

The pulse period calculation circuit 44 calculates the period T of the tone signal PP, and supplies the period signal SY, which is a pulse signal representing the actual pulse period T of the subject, to the filter selection circuit 46. Normally, the pulse period calculation circuit 44 is composed of a reference signal generator and a counter that counts signals from the reference signal generator, is reset by a tone signal PP, and outputs the count contents at the time of reset as a periodic signal SY. ,
The pulse generation period of the key signal PP is detected. That is, the waveform shaping circuit 34 and the pulse rate calculation circuit 44 form the pulse rate detection means.

The filter selection circuit 46 is a calculation means, and is
Based on the pulse period T of the subject represented by Y, the select signal SL is sent to the boat select terminal P of the multiplexer 40.
Supply to S. The multiplexer 40 receives a select signal S
One of the input ports P1 to P4 is alternatively selected based on L, and the pulse wave signal SM supplied thereto is A.
, /D converter 48. That is, the filter selection circuit 46 stores in advance a table representing the relationship between the pulse wave period and the fundamental frequency of the pulse wave shown in FIG. The fundamental frequency of the wave is the input boat P1
, if the period T is 038 to 05, the human-powered boat P
2, input boat P3 when the period T is 0.5 to 07, and human-powered boat P when the period T is 07 or more.
A select signal S_L for selecting 4 is output from the filter selection circuit 46. Therefore, the filters 26.28, 30.32 and the multiplexer/
The IO forms a filter selection means for selecting a filter suitable for the fundamental frequency of the actual pulse wave, and this filter selection means, the pulse rate detection means and the calculation means form a pulse wave discrimination device 47. . Note that the filter selection circuit 46 stores in advance a table representing the relationship between the number of heartbeats per unit time and the fundamental frequency of the pulse wave, and the pulse rate detection means detects the actual number of heartbeats, and based on the number of heartbeats, a table is stored in advance. The fundamental frequency may also be determined.

The A/D converter 48 converts the pulse wave signal SM into a code signal and supplies it to the I10 boat 38, while the I1
A start signal 88 is supplied to the 0 port 38 from the start switch 50 by pressing the start switch 50 .

The I10 boat 38 is connected to the CPU 52 via a data bus.
．． fOM54. AM55 is connected. C.P.
U52 performs signal processing using the temporary storage function of AM56 according to a program stored in advance in ROM54, and operates the air pump 12. A pump start signal AP, a rapid exhaust signal EQ, and a constant speed exhaust signal ES are supplied to the rapid exhaust valve 16 and the constant speed exhaust valve 18, respectively, and the pulse wave signal 8 is supplied from the A/D converter 48.
The blood pressure value is determined based on the change in the magnitude of M, and a blood pressure value signal SD for displaying the measured blood pressure on the blood pressure display device 58 is supplied. Therefore, they are CPU52. ROM
54. The AM 56, blood pressure display device 58, and the like form blood pressure measuring means.

The operation of this embodiment will be explained below according to the flowchart shown in FIG.

First, step S1 is executed, and it is determined whether or not the start switch 50 has been operated. Step S1 is repeated while the start switch 50 is not operated, but when the start switch 50 is operated and the start signal SS is supplied to the I10 boat 38, step S2 is executed. In step S2, the temperature of the rapid exhaust valve 16 and constant speed exhaust valve 1 is
8 is prohibited from supplying the rapid exhaust signal EQ and the constant speed exhaust signal ES to the rapid exhaust valve 16 and the constant speed exhaust valve 18.
is closed, and a pump activation signal AP is supplied to the air pump 12 to drive the air pump 12. As a result, as shown in section O-4 in FIG.
The pressure inside is increased.

Next, step S3 is executed, and it is determined whether the actual pressure P within the cuff 10 represented by the pressure value signal PV exceeds the maximum pressure PM, which is set in advance to be equal to or higher than the expected systolic blood pressure.

If the actual pressure P is smaller than the maximum pressure PM, the execution of step S3 is repeated, but as soon as the actual pressure P exceeds the maximum pressure PM, step S4 is executed, and the air is supplied to the air pump 12. The output of the pump activation signal AP that had been in effect is prohibited, and the driving of the air pump 12 is stopped. Then, step S5 is executed, the constant speed exhaust signal ES is supplied to the constant speed exhaust valve 18, the constant speed exhaust valve 18 is opened, and the pressure within the cuff 10 starts to decrease. A in Figure 9
The dots indicate this state.

After that, step S6 is executed to measure blood pressure,
The blood pressure display device 58 displays the systolic blood pressure value and the diastolic blood pressure value.

Here, in the blood pressure measurement in step S6, a so-called vibration method is used, and the blood pressure value is measured based on the magnitude of the pulse wave represented by the pulse wave signal SM. Therefore, in order to maintain measurement accuracy, it is necessary to The pulse wave contained in the 1o pressure vibration must be accurately extracted. In other words, the pressure vibration of the cuff 1o includes not only the fundamental wave of the pulse wave but also the second wave of the pulse wave.
．． Since it contains various noises such as 3rd order high harmonics and motion arch 7 act generated by the movement of the subject, a narrow band filter that selectively passes the fundamental frequency of the pulse wave is used. However, it is known from experience that the fundamental frequency of the pulse wave varies from subject to subject, and conventional methods have been used to absorb this variation. For example 08~
A bandpass filter was used that allowed signals with a frequency of about 1QEIz to pass. Therefore, even if such a filter is used, noise passing through that band can still be removed.
Blood pressure measurement accuracy was limited.

However, according to the present embodiment, the pulse period T of the subject is detected based on the pressure vibration of the cuff 10 that appears as the pressure within the cuff 1o approaches a preset maximum pressure PM, and the pulse period T of the subject is detected. The fundamental frequency of the actual pulse wave is determined from the relationship between the period T and the fundamental frequency of the pulse wave, and a filter suitable for that fundamental frequency is selected, so that the pulse wave is determined from the pressure vibration of the cuff 1O represented by the pressure signal SP. The waves are preferably discriminated prior to blood pressure measurement.

In other words, the pressure vibration of the cuff 1o represented by the pressure signal SP is mainly composed of pulse waves that are synchronized with the pulse rate, and forms a periodic waveform that is synchronized with the pulse rate. The waveform shaping circuit 34 generates a pulsed pulse signal P.
The actual pulse period T of the subject is calculated from the pulse signal PP, and a periodic signal S representing the period T is calculated.
Y is supplied from the pulse period calculation circuit 44 to the filter selection circuit 46. Then, in the filter selection circuit 46,
The select signal S L for selecting the filter most suitable for the actual pulse period T of the subject is sent to the multiplexer 40.
It is supplied to For example, if the actual pulse period T of the subject is 0.6 seconds, the select signal SL for selecting the input port P3 is sent to the multiplexer 40.
Since it is the second filter, it distinguishes only the signal near the fundamental frequency of the pulse wave of the subject from the pressure vibration of the cuff 10 and supplies it to the A/I) converter 48.

As a result, even if the fundamental frequency of the pulse wave varies from subject to subject, only signals around the fundamental frequency of the pulse wave are used for blood pressure measurement, resulting in high blood pressure measurement accuracy.

Returning to FIG. 8, when blood pressure measurement is completed, step S7 is executed and a rapid exhaust signal EQ is supplied to the rapid exhaust valve 16. Therefore, the quick evacuation valve 16 is opened and the cuff 10
The internal pressure is rapidly reduced. Point E in FIG. 9 shows this state.

In this way, according to this embodiment, the fundamental frequency of the pulse wave, which differs for each subject, can be easily determined by detecting the pulse period of the subject without using a spectrum analyzer. Based on the fundamental frequency, a narrow band filter is selected that passes only signals around the fundamental frequency of the actual pulse wave. Therefore, high-order harmonics of the pulse wave and noise mixed in the pressure vibrations of the cuff 10 can be removed very easily, and blood pressure measurement accuracy can be maintained at a high level.

Next, another embodiment of the present invention will be described. Incidentally, the same reference numerals are given to the parts common to those of the above-mentioned embodiment, and the explanation thereof will be omitted.

In FIG. 10, the pulse pulse signal PP output from the waveform shaping circuit 34 is directly supplied to the I10 port 38, and based on the pulse pulse signal PP, the multiplexer 40
The select signal S L for selecting M input ports P1 to P4 is determined according to a program stored in the ROM 54 in advance.

That is, the operation for performing such determination processing will be explained according to the flowchart of the fundamental frequency determination subroutine shown in FIG. is calculated, and step S as a calculation means
Step S2 is executed to determine the fundamental frequency of the actual pulse wave based on the pulse period 'J'. That is, a table showing the relationship between the fundamental frequency of the pulse wave and the pulse period shown in FIG. The fundamental frequency F of the wave is determined. Then, step 883 is executed to obtain the actual fundamental frequency F.
It is determined whether or not the frequency is greater than a predetermined frequency of 1?1. If the fundamental frequency 1' of the actual pulse wave is larger than the predetermined frequency F1, step s84 is executed, and a selection is performed to select the human-powered boat P1 to allow passage of the output signal from the first filter 26. Shinsha S
L, 1. /(→The boat 38 is supplied to the multiplexer 40. In step 883, if the actual JIT main frequency F is smaller than the predetermined frequency F1, the actual fundamental frequency F is the predetermined frequency]
Although it is between Sl and FZ, Anzu is judged. If the actual fundamental frequency F is between them, step S86 is executed, and the select signal SL for selecting the human-powered boat P2 to allow the output of the second filter 28 to pass.
is supplied to the multiplexer 40. In step s85, the actual fundamental circle/wave number F is set to a predetermined frequency F2.
If it is even smaller than , step SS7 is executed,
Actual fundamental frequency F is predetermined frequencies F2 and F3
It is judged whether there is a difference or not. Actual fundamental frequency F
is between them, step SS8 is executed and a select signal SL for selecting the human-powered boat P3 is supplied to the multiplexer 40, but if the actual fundamental frequency F is smaller than the predetermined frequency F3. has input 1
-) A select signal SI- for selecting P4 is supplied to the multiplexer 40. That is, steps SS3 to SSg are filters 26°28.30, 32.
．． Together with the multiplexer 4o, it forms filter selection means. In addition, in step S82, the relationship between the fundamental frequency of the pulse wave and the pulse period T is stored in advance in the ROM 54 by a functional formula, and the pulse wave is calculated based on the functional formula and the pulse period T determined in step SS1. Of course, the fundamental frequency F may also be calculated.

The subroutine consisting of steps SS1 to S89 described above can be executed after the pulse wave is captured as pressure vibrations of the cuff 10 and before blood pressure measurement is started. The same blood pressure measuring operation as in the above-mentioned embodiment is carried out between steps S1 and S6.

As described above, according to this embodiment, the fundamental frequency F of the actual pulse wave is easily determined, and a narrowband filter suitable for the fundamental frequency F is selected, so that the same In addition to this effect, since the pulse period T and the fundamental frequency of the actual pulse wave are calculated according to a pre-stored program, there is an advantage that the pulse period calculation circuit 44 and the filter selection circuit 46 are not required. . Therefore, the above-mentioned waveform shaping circuit 34 and state SS1
forms the pulse rate detection means, and steps SS2 to S89 form the calculation means.

It should be noted that the above is just one embodiment of the present invention,
The present invention can be modified in various ways without departing from its spirit.

[Brief explanation of the drawing]

FIG. 1 is a chart showing pressure oscillations within the cuff in relation to voltage and time. FIG. 2 shows a diagram obtained by frequency analysis of the vibration shown in FIG. 1. FIG. 3 is a chart showing the relationship between the fundamental frequency of the pulse wave and the beat period or number of beats. FIG. 4 is a diagram corresponding to claims of the present invention. FIG. 5 is a diagram showing the configuration of a blood pressure measuring device that is an embodiment of the present invention. FIG. 6 is a chart showing the characteristics of each filter provided in the embodiment of FIG. FIG. 7 is a diagram showing a waveform of a pulse signal formed from the pressure vibrations of FIG. 1. FIG. 8 is a flowchart 1 for explaining the operation of the embodiment shown in FIG. FIG. 9 is a chart showing the time change in the cuff internal pressure and the accompanying time change in the pulse wave during the operation of the embodiment shown in FIG. FIG. 10 shows another embodiment of the present invention and is 1/corresponding to FIG. 5. FIG. 11 is a flowchart illustrating the operation and operation of the embodiment shown in FIG. lO: Cuff 46: Filter selection circuit (calculating means) SP: Pressure signal SM: Pulse wave signal SY: Periodic signal (pulse signal) Step 881: Pulse detection means Step 882: Calculating means Applicant Nippon Corin Co., Ltd. Figure 4 Figure 6 Figure 7

Claims (2)

[Claims] (1) A method for distinguishing the fundamental wave of a pulse wave included in pressure vibrations from pressure vibrations in a cuff that compresses a part of the human body, and detecting the pulsation period or number of pulsations per unit time of the human body. ,
From the relationship between the predetermined pulsation period or number of pulsations per unit time and the fundamental frequency of the pulse wave, determine the actual fundamental frequency of the pulse wave corresponding to the detected pulsation period or number of pulsations per unit time. Then, a filter that passes the determined fundamental frequency is selected from a plurality of types of narrow band filters prepared in advance with different passable frequency bands, and the pressure vibration is passed through the selected filter, thereby generating a pulse wave. A pulse wave discrimination method characterized in that the fundamental wave of the pulse wave is obtained. (2) A blood pressure measuring device that includes a cuff that compresses a part of the human body and measures blood pressure based on changes in pulse waves included in pressure oscillations within the cuff, and based on a pressure signal representing the pressure oscillations. a pulse rate detection means for outputting a pulse signal representing a human body's pulse period or pulse rate per unit time; and a pulse rate detecting means that outputs a pulse signal representing a human body's pulse period or pulse rate per unit time; Based on this relationship, the present invention is equipped with an arithmetic means for determining the fundamental frequency of the actual pulse wave, and a plurality of types of narrow band filters having different passable frequency bands, and selectively selects the signal of the determined fundamental frequency from among the filters. filter selection means for selecting a filter to be passed through the pressure signal and discriminating a pulse wave signal representing a fundamental wave of the pulse wave from the pressure signal; A blood pressure measuring device characterized by comprising: blood pressure measuring means for determining a blood pressure value based on a change in magnitude of the pulse wave signal passed therethrough, and measuring the blood pressure value.