JPH05317270A - Electronic sphygmomanometer - Google Patents

Abstract

PURPOSE:To stably detect strength of a Korotkov sound by converting a count number of a beat in which the Korotkov sound is detected to a prescribed cuff pressure reduction speed and correcting the count number. CONSTITUTION:In a step S21, a pressure reduction speed of a cuff per one beat at the time of measuring a K sound is calculated. In this case, when a threshold level for recognizing strength of a K sound is set to copml, a CPU extracts a cuff pressure value PL which exceeds compl first, and a cuff pressure value PF which exceeds compl finally. Also, the number of beats NK between these PL-PF is derived, and the pressure reduction speed SP per one beat is calculated. Subsequently, in a step S22, the number of beats NK of the beat having the K sound exceeding compl is converted to the number of beats NK' at the time when the pressure reduction speed is 3mmHg/beat, and when NK' is >=3, a recognition level is set to comp2, and when it is <=3, the recognition level is set to comp3 (steps S23-25).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic sphygmomanometer using a Korotkoff sound level recognition method in an electronic sphygmomanometer using the Korotkoff sound method.

[0002]

2. Description of the Related Art In an electronic sphygmomanometer for measuring blood pressure using the Korotkoff sound method, when a Korotkoff sound is recognized from a detected pulse wave waveform, a recognition level is provided for noise discrimination. That is, of the detected pulse wave signals, signals exceeding the recognition level are processed as Korotkoff sounds. Then, in general, in order to improve the noise discrimination ability, a method of changing the recognition level according to the strength of the Korotkoff sound is adopted. This recognition level is a level for determining the generation point and the disappearance point of the Korotkoff sound that determines the blood pressure measurement value. Therefore, the accuracy and reliability of the blood pressure measurement depend on the setting of this recognition level.

Therefore, since the means for detecting the intensity of the Korotkoff sound is required to set the recognition level, the following processing is executed.

First, filtering is performed to extract only Korotkoff sounds from the pulse wave waveform detected by a microphone or the like, and then amplification is performed within a range where saturation is not achieved. A / D conversion is performed on the amplified signal to recognize the detected waveform. Then, in this case, the method for obtaining the strength of the Korotkoff sound is as follows. The maximum amplitude value of the Korotkoff sound signal waveform is the strength of the Korotkoff sound. 2. Take the sum of the amplitude values of the Korotkoff sound signal waveform. For example, the effective value of the Korotkoff sound signal waveform is calculated.

However, the above method is complicated,
It requires a fairly fast A / D converter. Then, the resolution of the A / D converter greatly affects its performance. That is, there is a problem that the device becomes very expensive because it requires a high-performance A / D converter in addition to the large scale structure.

In order to deal with such a drawback, there is the following method as a method of detecting the intensity of Korotkoff sound with a simple structure.

The gain of the amplifier is set so that the point at which the Korotkoff sound is generated and disappeared falls within the dynamic range of the amplifier, and the intermediate Korotkoff sound has its waveform saturated. Then, the output from this amplifier is set to a certain threshold (recognition level) by using a voltage comparator or a high-speed A / D converter with poor resolution.
The Korotkoff sound is recognized by detecting only the above signals.

When the strength of the Korotkoff sound is detected by this method, a threshold value larger than this recognition level is set separately from the recognition level for recognizing the Korotkoff sound. Then, the number of beats in which Korotkoff sounds that exceed this threshold are detected consecutively is counted, and the number of counts determines the rank of "strong", "medium", "weak", etc. with respect to the strength of the Korotkoff sounds. Make a mark. The recognition level for noise discrimination is set according to this rank.

[0009]

However, in the detection of the intensity of the Korotkoff sound by the Korotkoff sound recognition method of the above-mentioned conventional example, the count value of the number of beats exceeding a predetermined threshold is the pulse rate and the decompression speed of the cuff. There is a problem in that the intensity (level) of the Korotkoff sound cannot be detected correctly due to the influence of changes such as.

For example, a normal automatic sphygmomanometer is provided with a constant velocity exhaust device for keeping the cuff decompression speed constant at the time of measurement from the viewpoint of measurement accuracy, but the cuff is wound or the cuff of the examinee's arm is thick and the like. The amount of air in the cuff changes and it is not possible to perfectly compensate for the change in the decompression speed of the cuff. When the decompression speed of the cuff changes in this way, the count number of beats exceeding a predetermined value decreases when the decompression speed is fast, and conversely increases when the decompression speed is slow.

Also, there are individual differences in pulse rate (for example, pulse rate per minute), and in the case of a person with a large pulse rate, the number of beats exceeding a predetermined value is large, and conversely, a person with a small pulse rate. In case of, the number of counts decreases.

The present invention has been made in view of the above problems, and by converting the count number of the detected beats of the Korotkoff sound into a predetermined cuff depressurization rate and correcting the count number, stable operation is achieved. An object of the present invention is to provide an electronic sphygmomanometer using a Korotkoff sound level recognition method for detecting the intensity of Korotkoff sound.

[0013]

The electronic sphygmomanometer according to the present invention for achieving the above object has the following configuration. That is, in an electronic sphygmomanometer that measures blood pressure using the Korotkoff sound method, storage means for storing the Korotkoff sound data based on the Korotkoff sound and the cuff pressure data based on the cuff pressure in association with each other, and a Korotkoff exceeding a predetermined level. Using the counting means for counting the number of beats having a sound, the calculating means for calculating the inter-beat decompression rate which is the cuff decompression rate per beat from the storage means, and the inter-beat decompression rate calculated by the calculating means A converting means for converting the number of beats counted by the counting means into the number of beats at a predetermined decompression rate, and the strength of the Korotkoff sound input based on the number of beats obtained by the converting means. And a noise discrimination level for identifying the Korotkoff sound based on the strength of the Korotkoff sound recognized by the recognition means. And a Korotkoff sound detecting means for detecting a Korotkoff sound is generated from the set the storage means.

[0014]

With the above arrangement, the storage means stores the Korotkoff sound data based on the detected Korotkoff sound and the cuff pressure data based on the detected cuff pressure in association with each other. The counting means counts the number of beats having Korotkoff sounds exceeding a predetermined level. Further, the calculating means calculates the cuff depressurization rate per beat (inter-beat depressurization rate) using the Korotkoff sound data and the cuff pressure data stored in the storage means. Then, since the number of beats counted by the counting means and the beat-to-beat depressurization rate at that time are obtained, the number of beats is converted into the number of beats at a predetermined beat-to-beat depressurization speed, and the converted beat Recognize the strength of Korotkoff sounds by numbers.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a block diagram showing the schematic arrangement of an electronic blood pressure monitor according to the first embodiment. 1 is CP
U, which controls the entire electronic blood pressure monitor. 2 is RO
M is a control program executed by the CPU 1 and various constants are stored. A RAM 3 stores measured Korotkoff sound (hereinafter referred to as K sound) data, cuff pressure data, measured blood pressure value, and the like. A display unit 4 displays the measurement result and the like. An operation unit 5 includes a blood pressure measurement start switch, a stop switch, and the like. Reference numeral 6 denotes a K sound sensor, which is built in the cuff 10 and is mounted on the upper arm of the person to be inspected together with the cuff 10 to detect a pulse sound signal including the K sound. Reference numeral 7 denotes a filter, which extracts the K sound signal from the pulse sound signal input from the K sound sensor 6. An amplifier 8 amplifies the K sound signal. The gain of the amplifier 8 is set so that the K sound signal in the vicinity of the generation and extinction points of the K sound falls within its dynamic range and the intermediate K sound is saturated. Reference numeral 9 is an A / D conversion unit, which A / D converts the K sound signal amplified by the amplifier 8. The K sound signal converted into digital data is RAM
3 is stored.

Reference numeral 10 denotes a cuff (arm girdle), which is wound around the upper arm of the person to be inspected and pressurizes and depressurizes using air.
A pressure sensor 11 detects the pressure value of the cuff 10. Reference numeral 12 is an amplifier that amplifies the detection signal from the pressure sensor 11. Reference numeral 13 is an A / D converter, which is an amplifier 12
The output pressure signal is converted into a digital value. The pressure signal converted into digital data is stored in the RAM 3. A booster pump 14 is driven by a pump driver 15 to boost the pressure of the cuff 10. The constant speed exhaust valve 16 executes pressure reduction of the cuff 10 at a constant speed. Reference numeral 17 denotes an exhaust valve, which is driven by a valve drive unit 18 and releases the cuff 10 under pressure when the blood pressure measurement is completed.

Reference numeral 19 denotes a power supply unit, which supplies power to each of the above-mentioned components. Reference numeral 20 denotes a bus line, which is connected to each of the above-mentioned components to exchange data between the components. Also, 2
Reference numeral 1 is an air tube for forming an air circuit.

The operation of the electronic sphygmomanometer having the above configuration will be described below.

FIG. 2 is a flow chart showing the outline of the blood pressure measuring operation by the electronic blood pressure monitor of the first embodiment. It is assumed that the cuff 10 has been normally set by the person to be inspected and the blood pressure measurement start switch provided on the operation unit 5 has been pressed prior to the start of the processing according to this flowchart.

First, in step S11, various initial values are set, such as setting the cuff pressure value to 0. Next, in step S12, pressurization of the cuff 10 is started by driving the booster pump 14 by the pump driving unit 15. Then, in step S13, it is checked whether the pressure value obtained from the pressure sensor 11 is larger than the pressurization upper limit value, and if it exceeds the pressurization upper limit value, step S14.
Go to. If the pressure value does not exceed the upper limit of pressurization, the process returns to step S12 to continue pressurizing the cuff 10.
It should be noted that the pressurization upper limit value used here is stored in the ROM 2.

In step S14, the boost pump 14
And the depressurization of the cuff 10 is started by the constant speed exhaust valve. At this time, the K sound signal is checked in step S15, and if the K sound is detected immediately after the pressure reduction is started, it is determined that the pressurization is insufficient, and the process proceeds to step S16. Step S1
In 6, the pressure is repressurized to the upper pressure limit value +30 mmHg, and the process returns to step S14.

On the other hand, if it is not determined in step S14 that the pressurization is insufficient, the process proceeds to step S17. In step S17, measurement of the K sound signal and the pulse wave signal is started.
Here, the pulse wave signal detected by the K sound sensor 6 passes through the filter 7 for discriminating the K sound, and the discriminated K sound signal is amplified by the amplifier 8. Then, it is converted into a digital value by the A / D converter 9. The CPU 1 writes and stores this value in the RAM 3 as needed. In addition, step S18
In, the pressure value detected by the pressure sensor 11 is amplified by the amplifier 12 and converted into a digital signal by the A / D converter 13. The CPU 1 always sets this value to RA
Write to M3. The K sound signal and the pressure value are stored in the RAM 3 in association with their detection times.

Next, in step S19, it is checked whether or not the pressure value of the cuff 10 is below the lower pressure lower limit value, and if it is below, the process proceeds to step S20. As the lower limit value of decompression, for example, a value equal to or lower than the lowest value of blood pressure that a human can take is used. On the other hand, if the pressure value is higher than the lower pressure lower limit value, the process returns to step S17 to continue measuring the K sound. In step S20, the exhaust valve 17 is driven by the valve drive unit 18 to release the cuff 10, and the K sound measurement process ends.

Next, the processing procedure for K sound measurement will be described with reference to the flowchart of FIG. FIG. 3 is a flowchart showing a processing procedure of K sound measurement.

First, in step S1, measurement of K sound for each beat is executed. The measured K sound signal is stored in the RAM 3. When the blood pressure measurement is completed in step S2, the K stored in the RAM 3 in step S3.
The "K sound intensity" is detected from the sound signal, and the K sound recognition level is set based on the detected "K sound intensity". And
In step S4, blood pressure measurement by the K-tone method is executed using the set recognition level. The blood pressure measurement value obtained here is displayed on the display unit 4 in step S5.

Next, the "setting of the K sound recognition level" in step S3 of the above-mentioned flowchart of FIG. 3 will be described. FIG. 4 is a flowchart showing a processing procedure for setting the recognition level of the K sound. Further, FIG. 5 is a diagram showing the data stored in the RAM 3 by the above-mentioned K sound measurement. In FIG. 5, the data stored in the RAM 3 is represented by a graph for the sake of explanation.

In step S21, the decompression speed of the cuff 10 per beat in K sound measurement is calculated. Here, the threshold level for K sound intensity recognition is set to copm
When set to 1, the CPU 1 reads the cuff pressure value that first exceeds comp1 and sets it as P _L. Similarly, co
Read the cuff pressure value that exceeds mp1 at the end, and set it to P
_{Let's say F.} Then, (taking into even count beats in P _L and P _F) of the P _L to P count value and N _K number of beats between _F. From each of the above data, the depressurization speed SP per beat is calculated by SP = (P _L −P _F ) / (N _K −1).

In step S22, the count number N _{K of} beats having K sounds exceeding copm1 is converted into the count number N _K ′ when the pressure reduction speed is 3 mmHg / beat. N _K ′ is calculated by N _K ′ = (SP / 3) × N _K.

Then, in step S23, it is checked whether N _K 'is 3 or more. If it is 3 or more, step S24 is performed.
Then, the K sound recognition level is set to comp2. If it is less than 3, the process proceeds to step S25 to set the K sound recognition level to com.
Set to p3.

The above processing will be described more specifically with reference to FIG. Here, the K sound level of each beat (N _{1 to} N ₁₀ ) is
It is assumed that the difference between the maximum value and the minimum value of the K sound signal for each beat is used. Further, comp1 represents a threshold level for recognizing K sound intensity, comp2 represents a K sound recognition level when the K sound is strong, and comp3 represents a K sound recognition level when the K sound is weak. Further, the pressure values corresponding to N _{1 to} N ₁₀ of each beat are set to P _{1 to} P ₁₀ . Since the outputs of the beats N _{5 to} N ₇ are saturated in the amplifier 8, the output from the A / D converter 9 has the maximum value “255”.

The values used in the flow chart of FIG. 4 are read from this data. First, the beat at which the K sound exceeds the strength recognition threshold level comp1 for the first time is N ₄ , and the cuff pressure value P _L = P _{4 at} this time. Also, K
The last beat that the sound exceeds comp1 is N ₈ , and the cuff pressure value P _F = P _{8 at} this time. Therefore, the K sound is co
The number of beats exceeding mp1 is changed from N ₄ to N ₈ , and the count number N _K is 5. Based on the above data, the K sound recognition level setting process can be executed.

Then, in step S4 of the flowchart of FIG. 3, the blood pressure value is determined by the recognition level of the set K sound. For example, according to FIG. 5, if the K sound recognition level is set to comp2, the systolic blood pressure is P ₃ and the diastolic blood pressure is P ₉ . Further, when the K sound recognition level is set to comp3, systolic is P _2, diastolic blood pressure becomes P _9.

As described above, according to the electronic sphygmomanometer of this embodiment, when determining the strength of the K sound, the count number of beats having the K sound exceeding the predetermined level is counted at the predetermined decompression speed. Convert to a number. Therefore, it is possible to eliminate the influence of the cuff decompression speed, which varies depending on the way the cuff is wrapped and the thickness of the subject's arm, and the influence of individual differences in pulse rate,
The strength of the K sound can be correctly recognized.

<Embodiment 2> In Embodiment 2, an example in which the A / D converter 9 in Embodiment 1 is replaced with a voltage comparator will be described.

FIG. 6 is a block diagram showing the schematic arrangement of the electronic blood pressure monitor according to the second embodiment. Components having the same functions as those of the block diagram shown in FIG. 1 of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted here. The comparator 91 outputs "1" when the output voltage value from the amplifier 8 is equal to or higher than the K sound intensity recognition level (comp1), and otherwise outputs "0". In the comparator 92, the output voltage value from the amplifier 8 is the recognition level (com
When p2) or more, "1" is output, and in other cases, "0" is output. Further, the comparator 93 outputs "1" when the output voltage value from the amplifier 8 is equal to or higher than the recognition level (comp3) of the K sound, and otherwise outputs "0". The output values of the above comparators (91 to 93) are stored in the RAM 3 in correspondence with the elapsed time.

Since the blood pressure measuring operation by the electronic blood pressure monitor of the second embodiment is based on the flowcharts of FIGS. 2 to 4, detailed description thereof will be omitted here. However, in step S17 of FIG. 2, not the digital conversion value of the K sound signal, but the output of each comparator (91 to 93) is stored in the RAM 3. Therefore, when the K sound measurement ends, the RAM3
The data stored in is as shown in FIG. Here, the cuff pressure value (P1 to P12) for each beat is taken as the average value of the cuff pressure values measured while the output from the comparator is "1".

The values used in the flow chart of FIG.
It is read from the data shown in 7. First, the K sound
Beats that first exceed the strength recognition threshold level comp1
Is N _Five And the cuff pressure value P at this time_L = P_Five Tona
It The number of beats where the K sound exceeds comp1 at the end is N₈ so
Yes, the cuff pressure value P at this time_F = P₈ Becomes Obey
The number of beats where the K sound exceeds comp1 is N_Five To N₈ Tona
The number of counts N_K Is 6. Based on the above data
Setting the K sound recognition level according to the flowchart in Fig. 4
Processing can be performed.

Then, in step S4 of the flowchart of FIG. 3, the blood pressure value is determined by the recognition level of the set K sound. For example, according to FIG. 7, the recognition level is co
If it is set to mp2 adopts the output of the comparator 92, the systolic blood pressure is P _3, diastolic blood pressure becomes P _10. Further, the recognition level is adopted the output of the comparator 93 when it is set to comp3, systolic is P _2, a minimum blood pressure P ₁₁
Becomes

As described above, according to the electronic sphygmomanometer of this embodiment, when determining the strength of the K sound, the count number of beats having the K sound exceeding the predetermined level is counted at the predetermined decompression speed. Convert to a number. Therefore, it is possible to eliminate the influence of the cuff decompression speed, which varies depending on the way the cuff is wrapped and the thickness of the subject's arm, and the influence of individual differences in pulse rate,
The strength of the K sound can be correctly recognized.

In each of the above-described embodiments, the K sound recognition level is selected from two types, comp2 and comp3, but the invention is not limited to this. For example, if the count number of beats having K sounds exceeding a predetermined value (comp1) is 1 to 2, comp1
0, 3 to 4 comp11, 5 or more co
Various setting methods such as mp12 are possible.

[0042]

As described above, according to the electronic sphygmomanometer provided with the Korotkoff sound level recognition method according to the present invention, the count number of the detected beats of the Korotkoff sound is converted into a predetermined cuff depressurization rate and counted. By correcting the, it becomes possible to stably detect the intensity of the Korotkoff sound.

[0043]

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a schematic configuration of an electronic blood pressure monitor according to a first embodiment.

FIG. 2 is a flowchart showing an outline of a blood pressure measurement operation by the electronic blood pressure monitor of the first embodiment.

FIG. 3 is a flowchart showing a processing procedure of K sound measurement.

FIG. 4 is a flowchart showing a processing procedure for setting a recognition level of K sound.

FIG. 5 is a diagram showing data stored in a RAM 3 by K sound measurement according to the first embodiment.

FIG. 6 is a block configuration diagram showing a schematic configuration of an electronic blood pressure monitor according to a second embodiment.

FIG. 7 is a diagram showing data stored in a RAM 3 by K sound measurement according to the second embodiment.

[Explanation of symbols]

 1 CPU 2 ROM 3 RAM 4 Display part 5 Operation part 6 K sound sensor 7 Filter 8, 12 Amplifier 9,13 A / D conversion part 10 Cuff 11 Pressure sensor

Claims (1)

[Claims] 1. An electronic sphygmomanometer for measuring blood pressure using the Korotkoff sound method, a storage means for storing the Korotkoff sound data based on the Korotkoff sound and the cuff pressure data based on the cuff pressure in association with each other, and a predetermined level. Counting means for counting the number of beats having a Korotkoff sound exceeding 1, a calculating means for calculating an interbeat depressurization speed which is a cuff depressurization speed per beat from the storage means, and the interbeat depressurization calculated by the calculating means. Conversion means for converting the number of beats counted by the counting means into the number of beats at a predetermined inter-beat decompression speed using the speed, and Korotkoff input based on the number of beats obtained by the converting means. Recognition means for recognizing the strength of sound, and Korotkoff for distinguishing Korotkoff sound based on the strength of Korotkoff sound recognized by the recognition means An electronic sphygmomanometer comprising: a Korotkoff sound detection unit that sets a Coff sound recognition level and detects the Korotkoff sound from the storage unit.