JPH0331046B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a non-invasive automatic blood pressure measurement method and device, and in particular, it shortens the measurement process from measuring and determining the systolic blood pressure of a subject to near the diastolic blood pressure. This invention relates to an automatic blood pressure measuring device that enables this.

[Prior art and its problems] The measurement process in conventional non-invasive automatic blood pressure monitors is to uniformly increase the cuff pressure to a set value (150 to 200 mmHg) and then increase it at a constant rate (2 to 3 mmHg).
During the process of decreasing the cuff pressure (Hg/sec), the systolic blood pressure and diastolic blood pressure were determined by continuous measurements in that section. For this reason, the time required to measure blood pressure depends on the subject's blood pressure value (pulse pressure) when the cuff pumping speed is constant. During this period, the blood flow is almost stopped, resulting in a state of congested blood. This has often resulted in errors in determining the diastolic blood pressure. In addition, meaningful measurements are actually performed during a few heartbeats around the systolic and diastolic blood pressures, and constant blood pressure measurements in other intervals would actually take unnecessary measurement time. This not only caused pain to patients, but also hindered the realization of high-speed measurement to capture short-term blood pressure fluctuations.

In addition, conventional automatic blood pressure monitors use diaphragm pumps, piston pumps, etc. as pressurizing means, and the noise emitted by the pressurizing means every time a measurement is made causes stress not only to the subject but also to the people around them. This was the cause of the addition. Moreover, at night, this noise wakes patients on long-term blood pressure monitors from their sleep.
This has caused the inconvenience of not being able to capture blood pressure dynamics during sleep.

[Object of the Invention] The present invention has been made in view of the above-mentioned drawbacks of the prior art, and its purpose is to shorten the constant blood pressure measurement process up to around the diastolic blood pressure after determining the systolic blood pressure. Therefore, it is an object of the present invention to propose an automatic blood pressure measuring device that can quickly and accurately measure blood pressure.

Another object of the present invention is to provide an automatic blood pressure measuring device that eliminates cuff pressurization noise.

Another object of the present invention is to provide an automatic blood pressure measuring device that is small and lightweight and can be used continuously for long periods of time.

[Summary of the Invention] In order to achieve the above object, the automatic blood pressure measuring device of the present invention includes a pressurizing means for increasing the cuff pressure, a first pressure reducing means for decreasing the cuff pressure at a predetermined speed, and a first pressure reducing means for decreasing the cuff pressure at a predetermined rate. a second pressure reducing means for lowering the pressure at a speed faster than a predetermined speed; a pressure detecting means for detecting cuff pressure; a K sound detecting means for detecting a Korotkoff sound and outputting a K sound signal; and energizing the pressurizing means. determining means for determining the predicted diastolic blood pressure based on the cuff pressure at the time when the K sound signal first appears, and the K sound signal detected while the first pressure reducing means is activated after the stop of pressurization; A systolic blood pressure determining means for determining the systolic blood pressure; and a pressure reduction control means for energizing the second pressure reducing means based on the systolic blood pressure determination and rapidly lowering the cuff pressure to a pressure slightly higher than the predicted diastolic blood pressure. This is how it was done.

Further, when the predicted diastolic blood pressure value can be determined, the cuff pressure may be lowered by the pressure reduction control means to a value obtained by adding the first pressure value to the predicted diastolic blood pressure value.

In addition, when the predicted diastolic blood pressure value cannot be determined,
The cuff pressure may be lowered by the pressure reduction control means to a value obtained by subtracting a second pressure value from the cuff pressure at the time of determining the systolic blood pressure.

Further, as an example of the pressurizing means, it is preferable to use liquefied gas sealed in a liquefied gas cylinder as the pressure source.

[Embodiment of the Invention] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an automatic blood pressure monitor according to an embodiment of the present invention. In the figure, 1 is a cuff wrapped around the arm, 2 is a microphone for detecting Korotkoff sounds, and 3 is a pipe connecting the cuff 1 and the main body of the device to detect and control cuff pressure. The main body consists of three main parts. Reference numeral 4 designates a pressure control section that detects and controls cuff pressure, 5 a Korotkoff sound detection section that detects Korotkoff sounds, and 6 a central processing unit (CPU) that performs main control of the main body of the apparatus. Furthermore, numeral 7 is a display section for displaying the subject's systolic and diastolic blood pressure, etc., and is normally provided in the main body. Reference numeral 8 is a recording unit for recording systolic and diastolic blood pressure, etc., and is connected when automatic measurement is to be performed over a long period of time.

The pressure control unit 4 includes a pressure source 9 consisting of a cylinder filled with liquefied oxygen or liquefied carbon dioxide (CC ₂ ), or a cylinder filled with compressed air, etc., and a regulator 1 that adjusts the gas pressure output from the pressure source 9 to a constant level.
0, an air supply valve 11 for pressurizing the cuff, a constant evacuation valve 12 for reducing the cuff pressure at a constant rate (2 to 3 mmHg/Sec), and a rapid evacuation valve for rapidly reducing the cuff pressure. A valve 13, a pressure sensor 14 that detects cuff pressure and converts it into an electrical signal, and an A/D converter that converts an analog signal output from the pressure sensor 14 into a digital signal.
It consists of a D converter 15. The reason why the device of this embodiment does not use a pump as the pressure source 9 is to eliminate pressurization noise at all. Furthermore, the reason why this embodiment uses a gas cylinder instead of a pump is that a pulsation-free increase characteristic can be easily obtained when increasing the cuff pressure, and the advantage of linearly increasing the cuff pressure will be clear from the explanation below. Let's become. Furthermore, by preferably using a liquefied gas cylinder, it is possible to obtain a pressure source 9 that is small and lightweight and has an extremely large vaporization capacity _.
When using a liquefaction cylinder, it can be used continuously about 100 times, and the cylinder can be installed so as not to put strain on the lower back of the subject.

The Korotkoff sound detection unit 5 includes an amplifier 16 that preamplifies the weak sound signal detected by the microphone 2, and a signal corresponding to the Korotkoff sound by extracting each predetermined frequency component from the output signal of the amplifier 16 and comparing the amplitudes. A K-sound filter 17 separates the K-sound signal k (hereinafter also referred to as K-sound) by forming the K-sound signal k (hereinafter also referred to as K-sound), and extracts the amplitude signal component of blood vessel pulse pressure vibration contained in the output signal of the pressure sensor 14. It consists of a pulse filter 18 which separates the signals, shapes them into pulses, and outputs a pulse synchronization signal m. The pulse synchronization signal m captures the expansion and contraction movement of the blood vessel compressed by the cuff as the pressure applied to the cuff 1 is gradually decreased, and generally this signal appears earlier than the K sound and disappears later. Are known. Therefore, this amplitude signal component is extracted by the pulse filter 18 and used as a gate signal for detecting the K sound, thereby accurately detecting the weak K sound from the noise.

The CPU 6 includes a ROM containing the processing program of this embodiment, a microprocessor for executing the program, a RAM necessary for data processing, a PIO for inputting and outputting processing data, and supply/discharge valves 11 to 13.
The CPU 6 includes a driver circuit for driving the CPU 6, and various functions realized by executing the processing program are shown as blocks. To briefly explain these functional blocks, 19 is a control means that controls the main control of the CPU 6;
20 is the cuff pressure detection signal p output from the A/D converter 15
A pressure control means 21 reads the K sound signal K which appears and disappears within the pulse synchronization signal m, and controls the valves 11 to 13 to obtain a predetermined pressurization and depressurization state in the cuff. This is a blood pressure determination means for determining the systolic blood pressure and diastolic blood pressure of a subject.

2 to 5 relate to the operating principle of the apparatus of this embodiment, and FIG. 2 is a diagram showing one typical step of blood pressure measurement. In the figure, when the air supply valve 11 opens, the cuff pressure begins to rise quickly and without pulsation from point a to point b. The CPU 6 monitors the K sound during this interval and sets the cuff pressure at the time when the first K sound Pk ₁ appears as the predicted diastolic blood pressure PREDIA of the subject. As the cuff pressure increases, K sounds Pk ₂ , Pk ₃ , etc. occur at almost constant intervals.
is detected. Based on this cycle, CPU6 then
The maximum time interval t in which a sound should appear is determined, and if there is a K sound within that interval, this is confirmed. When the cuff pressure eventually exceeds the subject's systolic blood pressure, the K sound disappears, but the CPU 6 calculates the predicted systolic blood pressure of the subject using the cuff pressure at the time when the last K sound Pkn appears.
PRESYS and at the same time have a predetermined time t.
Since no sound is generated, the air closure valve 11 is closed.
The cuff pressure at this point is the optimal pressurization point b (PRESYS+α) that allows rapid measurement of subsequent systolic blood pressure. In this embodiment, since a liquefied gas cylinder is used as the pressure source 9, the increase in cuff pressure does not include any pulsating component. Therefore, in this section, the weak K sound can be accurately detected without worrying about noise being mixed into the microphone.
Therefore, the onset and disappearance of the K sound is monitored while the cuff pressure is rising, and based on this, a guideline for the subject's systolic and diastolic blood pressure is provided, making the main measurement process during cuff decompression described below extremely efficient.

Next, when the constant discharge valve 12 opens, the cuff pressure decreases from point b toward point c at a constant rate (2 to 3 mmHg/sec). During this period, the CPU 6 monitors the appearance and disappearance of the K sound in a more rigorous manner than before. That is, the true K sound signal is separated from noise by logical product processing with the pulse synchronization signal m, and the cuff pressure at the time when the first K sound _k1 appears is taken as the subject's systolic blood pressure SYS.
However, to confirm this, the CPU 6 determines the systolic blood pressure by detecting the K sound for at least three beats.

When the systolic blood pressure is determined, the sudden evacuation valve 13 is opened, and the cuff pressure changes from point c to the sudden evacuation target value d (predicted systolic blood pressure).
PREDIA+β). This is because it is actually unnecessary to detect the K sound in this section. at the same time
The CPU 6 monitors the cuff pressure detection signal p, and closes the quick discharge valve 13 when the cuff pressure reaches point d.

As a result, the cuff pressure is reduced again by the constant discharge valve 12, making it possible to accurately detect the K sound using the same method as described above. In this interval, CPU6 is at least 1
If K sounds are detected, it can be confirmed that the pressure at the sudden evacuation target value point d exceeds the diastolic blood pressure. When the cuff pressure eventually falls below the subject's diastolic blood pressure, the K sound also disappears, but in order to confirm this, the CPU 6 confirms that the K sound disappears by confirming that there is no K sound within the pulse synchronization signal m of at least 2 beats. The cuff pressure at the time when the last K sound km appeared was determined to be the subject's diastolic blood pressure DIA. Immediately after determining the diastolic blood pressure, the rapid drainage valve 13 is opened, the cuff pressure rapidly decreases from point e to point f, and one step is completed.

Compare the process of this embodiment described above with the conventional process of continuously monitoring the K sound from its appearance to its extinction (indicated by a chain dot in FIG. 2). conventionally,
As is generally done, the pressure is increased to a uniformly determined g point within the range of 150 to 200 mmHg, and then the pump is discharged. In contrast, the present embodiment automatically detects point b, which is slightly higher than the subject's systolic blood pressure SYS, and automatically determines the optimal pressurization point for entering constant drainage. This has the advantage that systolic blood pressure can be measured immediately. Conventionally, the K sound was continuously measured during constant ejection from point g to point i after pressurization. On the other hand, in this embodiment, when the systolic blood pressure is determined at point c during regular evacuation, the systolic blood pressure is immediately ejected and the measurement is omitted, and then the diastolic blood pressure is determined during the constant evacuation from point d to point e. Then, one step of measurement is completed.

Now, assuming that both pressurizing points are point b, the time difference Δt per measurement between the measurement process according to this embodiment and the measurement process according to the conventional method will be considered. The conventional measurement process in this case is shown by a two-dot chain line in the figure. Here, both cuff pressure and constant evacuation speed are
If PexmmHg/sec, the subject's systolic blood pressure is
Since there is no difference between SYS and diastolic blood pressure DIA, the time difference Δt per measurement in both processes is expressed as Δt = (SYS - DIA) / Pex - (TK ₂ + β / Pex), and this example is extremely short. It is clear that time is being measured.

FIGS. 3a and 3b are diagrams showing details of how the optimum pressurizing point b of this embodiment is determined. In figure a,
As mentioned above, when the first K sound Pk ₁ is detected as the cuff pressure increases, the cuff pressure at that time is used as the subject's predicted diastolic blood pressure PREDIA. Furthermore, when the second K sound Pk ₂ is detected, the upper limit t of the K sound generation period can be predicted from this point. That is,
Based on the first period t ₁ , CPU 6 will produce the next K sound at the latest.
It can be predicted that Pk ₃ will occur within t=(1±γ)t ₁ . This γ is a value determined by clinical empirical rules by extracting and comparing heart rate fluctuation data from multiple subjects, and in this example, a fixed value of γ = 0.1 to 0.5 is selected, for example. However, in this case, the values from ±0 to ±0.5 are shown in the table as γ.
It is prepared as Through many years of experience, the test subject's K
Even if the sound generation period fluctuates greatly in a short period of time, this can be covered if the above-mentioned γ is an appropriate value. When the K sound PK ₃ actually occurs, the next K sound Pk ₄ will be generated at the latest based on the new period t ₂ at t = (1 ±
γ) Can be predicted to occur within t ₂ . Of course,
In this case, the average of t ₁ and t ₂ may be taken and used for predicting the occurrence of K sound Pk ₄ . In this way, Pk ₃ and Pk ₄ continue, and if the K sound does not occur within the next time t = (1 ± γ) t ₃ , the air supply valve 11 is immediately closed, and the optimum pressurization point is determined using the cuff pressure at this point. b. K sound Pk ₄
The cuff pressure corresponding to PRESYS is the subject's systolic blood pressure.
It appears because it is predicted to be SYS.

Figure b shows a state in which only one K sound was detected during cuff inflation. In this case, the first K sound
Upon detection of Pk ₁ , the cuff pressure at that time is not considered the subject's predicted diastolic blood pressure PREDIA. This is because the K sound near the diastolic blood pressure is relatively weak, so it is thought that the K sound was not detected and was lost. In addition, in this case, since PREDIA is not determined, the pressure difference for determining the sudden evacuation target value after determining the systolic blood pressure is set to a predetermined value (for example,
40mmHg). This is because it has been confirmed through many years of clinical practice that the average pulse pressure amplitude is about 40 mmHg. Furthermore, in this case, since the aforementioned time t cannot be obtained, the optimum pressurizing point b is determined using a predetermined value (for example, 1.6 seconds) instead of the actual period _t1 . The predetermined value of 1.6 seconds indicates that the pulse is
This assumes a maximum cycle of 38 beats/min.

Furthermore, when no K sound is detected, the safety measure is to set the predetermined cuff pressure at point b' as shown in a and b in the same figure.
The limit of increase should be set at Pa (for example, 150 to 200 mmHg). The CPU 6 can easily perform this control by reading the cuff pressure detection signal p at appropriate times.

FIG. 4 is a timing chart showing a case where blood pressure measurement of a subject is successfully performed in one trial. Most of what is shown in this figure has already been described in the explanation of FIG. Here, the relationship between the pulse synchronization signal m and the K sound signal k will be described. As mentioned above, the pulse synchronization signal m captures the expansion and contraction movement of the blood vessels compressed by the cuff, and it is generally known that this signal appears earlier than the K sound and disappears later. Only the K sound generated within the pulse synchronization signal m during cuff constant evacuation is determined to be a true K sound signal, and K
It is used for the purpose of removing noise mixed in with sound.
Although not adopted in this embodiment, this method may be used to detect the K sound during cuff pressurization.

FIG. 5 is a timing chart showing a case where blood pressure measurement of a subject is performed by one automatic retry. In the figure, from cuff pressurization to constant evacuation,
The process up to point c, which determines the systolic blood pressure SYS, is the second step.
It is similar to that shown in the figure. Figure 5 shows that the predicted diastolic blood pressure PREDIA was much lower than the actual diastolic blood pressure DIA, so from point c to the sudden target value d' (e.g.
PREDIA - 10mmHg) indicates that the cuff pressure has already fallen below the diastolic blood pressure DIA. Constant β used to set the sudden target value
(10mmHg is selected in the example) is, for example
Based on the blood pressure fluctuation range (standard deviation SD of DIA) within the measurement time from PREDIA to DIA, 6mmHg is selected to cover 2SD, and 10mmHg is selected to cover 3SD.
Now, in the case of FIG. 5, the CPU 6 counts the pulse synchronization signal m for two beats in the constant interval from point d' to point e', but no K sound is detected. Therefore, approximately 2 mmHg is added to the cuff pressure at this point (point e') to raise the cuff pressure to point d''.Experientially, the cuff pressure at this time is approximately
The figure shows that the value is PREDIA + 20mmHg. Therefore, if such a retry is performed three times, the cuff will be pressurized to PREDIA + 40 mmHg, which will sufficiently cover the diastolic blood pressure DIA. As mentioned earlier, the average pulse pressure amplitude is about 40 mmHg. Next, when the cuff pressure rises to point d'', it shifts to constant evacuation again.In the figure, this pressure covers the diastolic blood pressure DIA, so some K sounds are detected within the pulse synchronization signal m.Soon, the cuff pressure increases. Subject's diastolic blood pressure
The K sound also disappears when it drops below DIA, but CPU6
To confirm this, a pulse synchronization signal of at least 2 beats m
Confirm the disappearance of the K sound by confirming that there is no K sound in the
The cuff pressure at the time the last K sound km appeared was determined to be the subject's diastolic blood pressure DIA. Immediately after the diastolic blood pressure is determined, the rapid drainage valve 13 is opened, the cuff pressure rapidly decreases from point e to point f, and one step is completed.

6 to 9 relate to the program control procedure of the apparatus of this embodiment which executes control according to the above-mentioned operating principle, and FIG. 6 is a flowchart showing the control procedure of one step of blood pressure measurement. In step S1, the air supply valve 11 is opened, and in step S100, optimal pressurization control processing is executed. The details of the optimum pressurization control process will be described later, but it is a process for determining the optimum pressurization point b of the cuff. Upon returning from this process, the air supply valve 11 is closed in step S2, and the constant discharge valve 12 is opened in step S3.
During the constant evacuation after pressurization, a systolic blood pressure determination process is performed in step S200, and the systolic blood pressure is displayed in step S4. Immediately after the systolic blood pressure is determined, the rapid drainage valve 13 is opened in step S5 to rapidly reduce the cuff pressure.
In step S6, it is determined whether the predicted diastolic blood pressure PREDIA has been determined in the optimum pressurization control process. If the determination is YES, wait for the cuff pressure to drop to the sudden evacuation target value (PREDIA+10mmHg) in step S7. If the determination is NO, the process advances to step S8 and the sudden evacuation target value (sudden evacuation starting pressure - 40 mmHg)
Wait until the pressure is reduced to When the target value is reached, the rapid discharge valve 13 is closed in step S9, and constant discharge can be started in that state. Of course, the constant discharge valve 12 may be closed during the sudden discharge described above. In step S10, a retry counter RC is initialized to 0. The retry counter RC is a counter that counts the number of retries when the first attempt at measuring the diastolic blood pressure is unsuccessful. During the regular evacuation after the sudden evacuation,
In step S300, diastolic blood pressure determination processing is executed.
The condition for returning from this process is when no K sound is detected within the pulse synchronization signal m for two beats. step
In S11, the value of the K sound counter KC is checked, and when KC is not 0, it indicates that 1 or more K sounds have been detected, and the flow advances to step S12, where the diastolic blood pressure is displayed and one step ends. However, if KC is 0 as determined in step S11, a retry is necessary, and the flow advances to step S13 to check whether retry has been performed three times. If the process has been repeated three times, the process advances to step S20 and error processing occurs. However, if it has not been repeated three times, the process advances to step S14 and the content of the retry counter RC is incremented by one. In steps S15 and S16, the constant exhaust valve 12 is closed and the air supply valve 11 is opened. In step S17, wait until the cuff pressure reaches the pressurization start pressure + 20 mmHg.
In steps S18 and S19, the air supply valve 11 is closed and the constant discharge valve 12 is opened, and the process returns to step S300 to execute the diastolic blood pressure determination process.

FIG. 7 is a flowchart showing the optimum pressurization control processing procedure. In step S101, a series of initialization processing is performed. That is, the K sound counter KC becomes 0,
Pressure register PR is set to upper limit of cuff pressurization Pa, timer register TR is set to constant 1.6sec, K sound detection flag
KF is initialized to 0. K sound detection flag KF is K
This flag becomes logic 1 when the sound signal k rises, and is reset when the CPU 6 senses this. In step S102, it is determined whether the cuff pressure detection signal p has reached the pressurization limit PR (in this case, the upper limit Pa). If the timer t has not reached the timeout, it is determined in step S103 whether or not the timer t has timed out. The timer is for detecting whether or not there is a next K sound within a predetermined time from the preceding K sound, and is not activated at first. The flow then advances to step S104 to check the k-sound counter KC. first K sound
KC is 0 until Pk ₁ is found. The flow jumps to step S107 and checks the K sound detection flag KF. If KF is not 1, the process returns to step S102 and the above-described loop is repeated until the first K sound occurs. If a K sound is found in step S107, step
Proceeding to S108, the value of the cuff pressure detection signal p at that time is stored in the predicted blood pressure memory (PRE memory).
This is because it will be used later as the predicted diastolic blood pressure PREDIA. In step S109, KC is increased by +1. In step S110, it is determined whether KC is 2 or more.
If KC is smaller than 2, it is not possible to calculate the upper limit t of the cycle at which the next K sound occurs, so the process advances to step S112 and the timer is activated.

Again in step S102, it is checked whether the pressurization limit is present or not, and if it is not satisfied, it is checked in step S103 whether or not there is a timeout. At this point TR is a constant
1.6 seconds is entered, and if there is no next K sound by then, it is judged as a timeout, the process is exited, and the optimal pressure point b is determined when only one K sound is detected during cuff inflation. decide. If it is before the timeout, the flow advances to step S104 to check KC. Always step if one or more K sounds occur.
Proceeding to S105, processing for separating the K sound from the noise is performed. That is, in step S105, the timer is
Determine whether it is 300mS or more, and select from the preceding k sound.
Using the empirical rule that the next K sound does not occur within 300 mS (corresponding to a heart rate of 200 beats/min or more), previous K sound signals are ignored. Step S106
Then, check whether timer t exceeds 1.6 seconds or not, and use the empirical rule that the next K sound will not occur if the time exceeds 1.6 seconds from the preceding K sound (corresponding to a heart rate of 38 beats/min or less). and ignores subsequent K sound signals. Therefore, the K sound is checked only within the range that satisfies both steps S105 and S106, and when the K sound is detected in step S107, the cuff pressure p at that point is stored in the memory in step S108, and the cuff pressure p at that point is stored in the memory.
Add 1 to KC in S109, and check KC in step S110. When KC becomes 2 or more, it becomes possible to calculate the upper limit of the period at which the next K sound should occur. The flow advances to step S111, where the time register TR is set to (1±
γ) Set t. Until now, TR was constant 1.6sec
However, from the next point on, a value multiplied by (1 ± γ) to the previous period t is used, and optimal pressure control is performed for faster and more accurate main measurements according to the subject's condition. be exposed. In step S112, the timer is started again, and the process returns to step S102. When the K sound eventually disappears, a timeout is detected in step S103, the process is exited, and the optimal pressure point b is determined when two or more K sounds are detected during cuff inflation.

FIG. 8 is a flowchart showing the procedure for determining systolic blood pressure. In step S201, a series of initialization processing is performed. That is, pulse counter MC becomes 0, K
The sound counter is initialized to 0, the pressure register PR is initialized to the lower limit value Pb of pressure reduction, the pulse detection flag MF is initialized to 0, and the K sound detection flag is initialized to 0. The lower limit Pb is, for example, a value below which systolic blood pressure cannot exist. The pulse detection flag MF is a flag that becomes logic 1 when the rising edge of the pulse synchronization signal m is detected, and is reset when the CPU 6 senses this. If the cuff pressure exceeds the decompression limit in step S202, the process advances to step S214 to process an error. However, such a situation rarely occurs in practice. In step S203, pulse counter MC is checked. The processing in steps S204 to S206 is the same as that described in steps S104 to S106 in FIG. 7, except that the target is the pulse synchronization signal m. In step S206, the pulse detection flag MF is checked, and the above loop is repeated until the first MF is found. When the first MF is found, the K sound flag KF is checked in step S207.
If KF is detected, the cuff pressure p at that time is stored in the memory in step S208, and KC is incremented by 1 in step S209. Also, while the K sound is not detected, the step
Proceeding to S210, the level of the raw pulse synchronization signal m is checked. While the signal level is logic 1, K sound detection is repeated. This is to remove noise by detecting only the K sound in the pulse synchronization signal m. Eventually, when the level of the pulse synchronization signal m becomes logic 0, the step
Proceed to S211 and add +1 to MC. In step S212
Check KC, if KC=3, determine systolic blood pressure SIS,
Exit processing. If KC is smaller than 3, the timer is activated in step S213, and the process returns to step S202. The subsequent processing is the same as that described in FIG. 7, so the explanation will be omitted.

FIG. 9 is a flowchart showing the procedure for determining diastolic blood pressure. In step S301, a series of initialization processing is performed. The pressure register PR is initialized to an even lower lower limit value Pc of reduced pressure. The rest is the same as step S201 in FIG. Furthermore, the processing from step S302 to step S307 is performed in accordance with the steps in FIG.
It is the same as the process from S202 to step S207,
Explanation will be omitted.

Now, when the K sound flag KF is detected in step S307, the cuff pressure p at that time is stored in the memory in step S308, KC is incremented by 1 in step S309, and MC is reset in step S310. The minimum blood pressure is
Since the determination is made based on the fact that only two consecutive beats of MF are detected after at least one KF is detected, the MC is reset after the KF is detected. Further, if the level logic 0 of the pulse synchronization signal m is detected in step S311 even though no K sound is detected in step S307, the flow advances to step S312 and MC is incremented by 1. When this route is passed, a state in which no K sound is generated in the pulse synchronization signal m is shown. In step S313, it is checked whether MC is 2 or not.
If MC is 2, the process exits. Also, when MC is smaller than 2, the timer is activated in step S314,
Return to step S302. The subsequent processing is similar to that described in FIG. 7 or 8.

The entire device of the present application is small and lightweight, and as mentioned above, by carrying the cylinder on the waist of the subject, even subjects other than those who are bedridden can carry the entire device without interfering with their normal daily lives. It is. Therefore, for example, data for a whole day can be measured every 30 minutes without the subject having to go to a predetermined location. In this case, the CPU mentioned above
A built-in timer means controls the start of measurement at each predetermined time. At this time, if the first measurement time is at a time with a poor separation such as 〇〇: Sometimes I do. By doing this, it is easier to prepare a system for accepting measurements from test subjects, data from multiple test subjects can be compared on the same time axis, and fluctuation patterns and reproducibility can be easily examined.

[Effects of the Invention] As described above, according to the present invention, after determining the systolic blood pressure, the cuff pressure is rapidly lowered to a pressure slightly higher than the predicted diastolic blood pressure detected during cuff inflation. Since the process is cut out, blood pressure can be measured quickly and accurately, and high-speed blood pressure measurement without measurement errors that can capture short-term blood pressure fluctuations, which was previously impossible, becomes possible.

Also, while the cuff pressure pressurizing means is being energized, the first K sound signal when the cuff pressure slowly rises is detected,
Since the cuff pressure at this time is used as the predicted diastolic blood pressure, the predicted diastolic blood pressure can be determined easily and reliably.
In addition, there is no need for special detection equipment.
Since the diastolic blood pressure can be reliably predicted, the device configuration can be simple and the cost can be reduced.

Further, since no pulsation source or noise source such as a diaphragm pump or piston pump is used as a pressurization source, the cuff pressure can be increased without pulsation (linearly). Therefore, the onset and disappearance of Korotkoff sounds during cuff pressurization can be accurately detected, and based on this, the diastolic blood pressure can be accurately predicted, and highly reliable extraction can be performed. Moreover, since there are no noise sources, there is no stress on surrounding patients, and even if continuous measurements are taken at night, long-term blood pressure monitor patients will not wake up from sleep, making it possible to accurately capture blood pressure movements during sleep. .

Furthermore, since a liquefied gas cylinder is used as the pressurization source, the device can be made smaller and lighter, and its vaporization capacity is large, so even if the device is made portable, it can be used for a long time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an automatic blood pressure monitor according to an embodiment of the present invention, FIG. 2 is a diagram showing a typical step of blood pressure measurement, and FIGS. Figure 4 shows the details of how pressure point b is determined. Figure 4 is a timing chart showing when the subject's blood pressure measurement was successfully performed in one attempt. Figure 5 is the timing chart when the subject's blood pressure measurement was performed automatically in one attempt. FIG. 6 is a timing chart showing the case where retry is performed; FIG. 6 is a flow chart showing the control procedure for one step of blood pressure measurement;
FIG. 7 is a flowchart showing the optimum pressurization control processing procedure, FIG. 8 is a flowchart showing the systolic blood pressure determination processing procedure, and FIG. 9 is a flowchart showing the diastolic blood pressure determination processing procedure. Here, 1...cuff, 2...mike, 3...pipe,
4...Pressure control section, 5...Korotkoff sound detection section, 6...
Central processing unit (CPU), 7
...display section, 8...recording section.

Claims (1)

[Scope of Claims] 1. A pressurizing means for increasing cuff pressure, a first pressure reducing means for decreasing cuff pressure at a predetermined speed, and a second pressure reducing means for decreasing cuff pressure at a faster rate than the predetermined speed. , a pressure detection means for detecting the cuff pressure, a K sound detection means for detecting the Korotkoff sound and outputting the K sound signal, and a cuff pressure when the K sound signal first appears while the pressurizing means is energized. determining means for determining the predicted diastolic blood pressure based on the K sound signal detected during activation of the first pressure reducing means after the stop of pressurization; An automatic blood pressure measuring device comprising: a pressure reduction control means that energizes the second pressure reduction means based on the determination and rapidly lowers the cuff pressure to a pressure slightly higher than the predicted diastolic blood pressure. 2. A patent claim characterized in that when the predicted diastolic blood pressure value can be determined by the determining means, the cuff pressure is lowered by the pressure reduction control means to a value that is the sum of the predicted diastolic blood pressure and the first pressure value. The automatic blood pressure measuring device according to item 1. 3. When the predicted diastolic blood pressure value cannot be determined by the determining means, the cuff pressure is lowered by the pressure reduction control means to a value obtained by subtracting the second pressure value from the cuff pressure at the time of determining the systolic blood pressure. An automatic blood pressure measuring device according to claim 1. 4. The automatic blood pressure measuring device according to claim 1, wherein the pressurizing means uses a liquefied gas sealed in a liquefied gas cylinder as a pressure source.