JP3393432B2 - Electronic blood pressure monitor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic sphygmomanometer. In general, an electronic sphygmomanometer pressurizes a living artery by pressurizing a cuff, and in the subsequent decompression process, a blood vessel such as a pulse wave, a K sound and the cuff pressure are used to obtain a maximum blood pressure and a minimum blood pressure. Determine blood pressure. In this type of electronic sphygmomanometer, there are conventional methods for reducing pressure during measurement, that is, pressure drop methods. At the time of pressure drop, the displacement adjusting means is adjusted so that a predetermined pressure drop speed is obtained. At the time of pressure drop, the displacement adjusting means is adjusted so that the pressure drop speed calculated according to the detected armband pressure and pulse is obtained (Japanese Patent Laid-Open No. 5-84221).
No. JP-A-5-337090). The pressure reduction rate is adjusted in accordance with the disturbance of the pulse wave amplitude during pressurization (Japanese Patent Laid-Open No. 5-200005). The pressure reduction rate control method employed by these conventional electronic sphygmomanometers changes the voltage applied to the control valve at a fast control cycle in order to quickly deliver the target pressure reduction rate after the pressurization is completed. When the depressurization speed reaches the target speed, initial high-speed control is performed to return to a normal control cycle in which blood pressure can be calculated. In the above-described conventional pressure reduction control method for an electronic sphygmomanometer, the initial value of the control valve drive voltage is set to a high voltage that can sufficiently close the valve.
Until reaching the drive voltage that can achieve the target pressure reduction, a time delay of a few seconds has occurred because of the fast control. For this reason, the measurement time becomes longer,
There is a problem that measurement cannot be started unless the human body is pressurized more than necessary. The present invention has been made paying attention to the above-mentioned problems, and an object thereof is to provide an electronic sphygmomanometer capable of making measurements as fast as possible without losing accuracy. The electronic sphygmomanometer of the present invention is a process in which at least a part of an artery of a human body is pressurized to a pressure higher than the maximum blood pressure using a fluid pressurizing means, and then gradually reduced. Pressure pressure change information detecting means for detecting pressure force change information during pressurization, comprising fluid pressure control means for controlling the pressure reduction rate by adjusting the flow rate of the fluid; , Pressure rise measurement during pressurization, fluid pressurization
From the amount of operation of the means, the wearing state of the human body compression part and the compression site
Compliance measuring hand with information on biological characteristics
Compliance calculated in steps and preset
From the pressure end pressure, using the characteristics of the fluid pressure control means
Immediately after depressurization, fluid pressure is reached so that the depressurization target speed is reached.
Determining an initial value to be provided to the force control unit, Ru and a speed control initial value determining means for indicating the initial value of the characteristic amount at the start of pressure reduction in the fluid pressure control means. In this electronic blood pressure monitor,
Immediately after pressurization, stable decompression control at the target decompression speed
Can be performed without the need for wasted time and extra pressure to control stability, it can be measured with minimum time and pressure,
In addition, the accuracy is not lost. DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in more detail below with reference to embodiments. FIG. 1 is a block diagram of an electronic sphygmomanometer according to an embodiment of the present invention. This embodiment of the electronic sphygmomanometer includes a sphygmomanometer body 1 and an arm band 2 attached to a human body measurement site. The sphygmomanometer body 1 includes a pressure sensor 3 that detects the armband pressure and a pressure pump 4 that pressurizes the armband.
And the electromagnetic valve 5 for adjusting the flow rate for releasing the air in the arm band to the outside and reducing the pressure, the following calculation control units configured in the one-chip microcomputer 1a, and turning on / off the power and starting measurement Etc., and a display unit 18 for displaying a blood pressure value and a pulse as measurement results. The one-chip microcomputer 1a includes a pressure sensor 3
A pulse wave detection unit 6 for detecting a pulse wave signal superimposed on a pressure signal output from the pressure, a pressure for converting the pressure signal into a pressure value, outputting the pressure value, and detecting a representative pressure value of the armband when the pulse wave is generated The detection unit 7 extracts a feature amount from the pulse wave signal and the representative pressure value, calculates the feature amount together with the representative pressure value, and determines a parameter that correlates with the blood pressure value. The pulse wave feature amount calculation unit 8 correlates with the blood pressure value. Decompression rate determination unit 9 that determines a depressurization rate from parameters, a pulse wave cycle calculation unit 10 that calculates the cycle of a detected pulse wave signal, and a pressurization target value determination that determines a pressurization set value from parameters that correlate with blood pressure values The pressure control unit 12 that controls the voltage for driving the pressure pump 4, the speed control initial value determination unit 13 that determines the initial value of the solenoid valve drive voltage at the start of pressure reduction, and the pressure reduction speed determination unit 9 To depressurize at the target depressurization speed The pressure reduction control unit 14 that controls the drive voltage of the magnetic valve 5, the blood pressure calculation unit 15 that determines the blood pressure from the output of the pulse wave feature amount calculation unit, and the drive voltage-flow rate characteristic data of the electromagnetic valve that is stored in advance in a ROM or the like. A certain solenoid valve characteristic curve 16 is provided. FIG. 2 is a perspective view showing the appearance of the electronic blood pressure monitor of this embodiment. On the upper surface of the sphygmomanometer body 1, the display unit 1
2, power switch 11 a, measurement start switch 11
b. Next, the operation of each part of the electronic blood pressure monitor of this embodiment will be described. At the time of blood pressure measurement, the wristband 2 is wrapped around the measurement site, and the measurement is started after resting. Power switch 11
When measurement is started by pressing the measurement start switch 11b with a turned on, the pressure pump unit 4 sends air to the armband 2 to increase the armband pressure. The armband pressure is converted into a pressure signal by the pressure sensor 3, and then taken into the one-chip microcomputer 1a as a pressure signal by means such as AD conversion. The pulse wave detection unit 6 extracts a pulse wave signal superimposed on the pressure signal. Fig. 3 shows the pressure signal at the time of pressurization and the extracted pulse wave signal.
Shown in In the pressure detection unit 7, the pressure signal is corrected by the linearity correction of the pressure sensor 3 and the drift correction by the environmental change such as temperature, and an accurate pressure value is output and also output from the pulse wave detection unit 6. The representative pressure value when the pulse wave is generated is output in synchronization with the pulse wave detection timing signal. FIG. 3 shows the relationship between the pulse wave signal and the representative pressure value. The pulse wave feature amount calculation unit 8 calculates a pulse wave feature amount correlated with blood pressure from the pulse wave signal output from the pulse wave detection unit 6 and the representative pressure value output from the pressure detection unit 7, Output. An example of the pulse wave feature amount calculation will be described. First, the characteristics of the pulse wave waveform that changes depending on the relationship between the blood pressure value of the human body and the armband pressure include the pulse wave amplitude, the pulse wave area, the pulse wave width (time when the pulse wave amplitude is larger than a certain threshold value), etc. Although there are many others, the pulse wave amplitude and pulse wave width will be described here as an example. FIG. 4 shows the armband pressure during pressurization [(a) of FIG. 4], the pulse wave waveform extracted from the armband pressure signal [(b) of FIG. 4], and the armband pressure when the pulse wave is generated. The pressure value is plotted on the horizontal axis and the pulse wave amplitude at that time is plotted on the vertical axis [(c) of FIG. 4]. The pulse wave amplitude is
As an oscillometric blood pressure measurement method, it shows a generally well-known method, and it has a mountain shape with the largest amplitude in the vicinity where the armband pressure becomes the average blood pressure,
The amplitude rapidly decreases on the high pressure side from the maximum blood pressure and on the low pressure side from the minimum blood pressure. In FIG. 4C, the pressure Pmax at which the amplitude is maximum, and the pressures Ps and Pd at which the pulse wave amplitude envelopes having a certain threshold value Ths and Thd cross are illustrated.
Where Ps is the maximum blood pressure, Pd is the minimum blood pressure, Pmax
Is a value well correlated with mean blood pressure. In FIG. 5, the maximum amplitude value of the pulse wave itself is normalized so that all of the pulse wave waveforms described in FIG. 4 have the same amplitude. In order to normalize, the value obtained by dividing the pulse wave width _tw by the pulse wave period t _c is expressed as K
2 as shown in FIG. The pulse wave width ratio K2 is large in the vicinity of the minimum blood pressure, and decreases as the maximum blood pressure is approached. Therefore, the pressures Pks and Pkd at which the pulse wave width ratio K2 becomes the values Ks and Kd are values that are well correlated with the maximum blood pressure and the minimum blood pressure. The characteristic quantities Ps, Pd,
A decompression speed method using Pmax, Pks, or Pkd will be described below. In the decompression speed determination unit 9, the feature amounts Ps, Pd, Pmax that are outputs of the pulse wave feature amount calculation unit 8.
Alternatively, the pressure reduction speed is determined by the following equation using Pks and Pkd as inputs. 1) When Ps and Pd are used Decompression rate def ₋ v = (Ps−Pd−mb1) × Pc / N (1) 2) When Ps and Pmax are used Decompression rate def ₋ v = (3 · Ps−3 · Pmax−mb2) × Pc / N (2) 3) When Pd and Pmax are used Depressurization speed def ₋ v = (3/2 · Pmax−3 / 2 · Pd−mb3) × PC / N (3) 4 ) When Ps is used Pressure reduction speed def ₋ v = (a · Ps + b−nb4) × Pc / N (4) where Pc is a pulse period calculated by the pulse period calculation unit 10. When Pc is not used, a period Pc = 1 second calculated from a normal person's pulse rate, for example, 60 beats / minute, may be used as a fixed value. N is between the systolic and diastolic blood pressures during decompression,
That is, the number of pulses generated between pulse pressures. When N is increased, the decompression speed is decreased, and the number of pulses generated between the pulse pressures is increased. On the contrary, if it is made smaller, the pulse number decreases, and it has been experimentally confirmed that the measurement accuracy is remarkably deteriorated when N = 2 to 3, and it is also clear from the viewpoint of the measurement principle. Therefore, the value of N should be set in consideration of the performance of the decompression measurement algorithm, and generally N = 5 is appropriate. The calculations in parentheses in the above equations (1) to (4) are all for calculating the pulse pressure (maximum blood pressure-minimum blood pressure).
The values of mb1 to mb4 are determined in consideration of the offset amount for calculating the pulse pressure and the margin amount for preventing the pressure reduction speed from being set too fast. The actual value is adjusted and set in advance according to the Ths and Thd values that are the parameter calculation thresholds. The pressure values Ps and Pd are the highest blood pressures,
When Ths and Thd are adjusted to match the minimum blood pressure, at least 2 of the maximum blood pressure, the average blood pressure, and the minimum blood pressure
This is an example of determining the pressure reduction rate using only the maximum blood pressure. Next, the characteristic amount Pks calculated from the pulse wave width,
The method of determining the decompression speed when Pkd is input is as follows. Depressurization speed def ₋ v = (Pks−Pkd−mb5) × Pc / N (5) Pc is the above-mentioned pulse period, and N is the number of pulses detected similarly between the above-mentioned pulse pressures. . Similarly for mb5, offset amount adjustment for calculating the pulse pressure and parameters Pks, Pk
It is adjusted according to the values of Ks and Kd used to calculate d and set in advance. As described above, when the depressurization speed is determined from the pulse wave information during pressurization, the pressurization target value is set next. When the armband pressure reaches the target value, pressurization is stopped and the depressurization measurement is performed. Transition. The pressurization target value is set for the purpose of detecting at least one pulse at a pressure higher than the maximum blood pressure when shifting to the decompression measurement. This is not necessarily the case when using a technique such as extrapolation in the decompression measurement algorithm to estimate the pulse wave at a pressure that was not actually pressurized. In order to ensure, it is necessary to pressurize up to the vicinity of the systolic blood pressure. The pressurization target value is calculated based on the feature value at the time of pressurization correlated with the systolic blood pressure to be measured or the estimated systolic blood pressure at the time of pressurization. To the time when a pulse effective for measurement can be detected varies depending on the speed of the pulse of the person to be measured and the timing of shifting to decompression. For example, a person having a pulse of 60 beats / minute is decompressed at a rate of 10 mmHg / second. When measuring with a maximum of 10m
The first value of mHg is detected only when the pressure is reduced from the pressure end pressure. When the pressure is reduced at such a high speed, the pressure reduction speed is hindered unless the pressure target value is determined in consideration of the pressure reduction speed. In this embodiment, the electronic sphygmomanometer is provided with means for setting the pressurization target value using the feature quantity correlated with the systolic blood pressure and the pressure reduction speed, so that the measurement is carried out with the necessary and minimum pressurization. Can do. Specifically, the target pressure value is determined by the target pressure value determining unit 11 using the feature values Ps, Pd, and Pmax, which are output examples of the pulse wave feature value calculating unit 8. To do. 1) Pressurization target value Inf ₋ max = def ₋ v · (np × Pc + α) + Ps + β1 (6) 2) Pressurization target value Inf ₋ max = def ₋ v · (np × Pc + α) + (3 · Pmax− Pd) + β2 (7) Here, def ₋ v is a decompression speed that is an output of the decompression speed determination unit 9, np is a pulse rate detected at a pressure higher than the maximum blood pressure during decompression, and Pc is a pulse cycle. β1 and β2 are the terms Ps + β1, (3 · Pmax−P) in the equations (6) and (7).
d) It is set so that + β2 is close to the systolic blood pressure, and changes depending on the feature value determination thresholds Ths and Thd. When the armband pressure reaches the pressurization target value, the decompression is started at the set target speed, and the decompression measurement is performed. As the solenoid valve 5, a valve whose flow rate changes according to the voltage to be driven is used. The voltage-flow rate characteristics are shown in FIG. On the other hand, when the pressure reduction speed is controlled to the target value, a time delay occurs until the solenoid valve 5 is sufficiently closed during pressurization until the voltage reaches a voltage at which a flow rate for achieving the target pressure reduction speed can be obtained. This means that the pressure target value is absorbed until this delay is absorbed.
It means that it needs to be higher. In addition to increasing the measurement time, this increases the pressure value and increases the burden on the person being measured. In order to solve this problem, a pressure reduction speed initial value determining means 13 is provided which can set an initial value of a voltage for driving the solenoid valve 5 to a voltage at a flow rate at which a target speed can be obtained. A reduced pressure rate was obtained. In the pressure reduction control initial value determination unit 13, the pressure P that is the output of the pressure detection unit 7.
(I), the pump drive voltage Vb and the pressurization end pressure Inf _- max, which are the outputs of the pressurization control unit 12, and the voltage of the solenoid valve-
The initial value of the valve drive voltage is determined from the flow characteristic curve as follows. First, the compliance Cp at the end of pressurization is obtained by the following equation. Cp = {P (i) −P (i−1)} / Vb (8) In the equation (8), Vb is a pressure pump drive voltage,
It is proportional to the pump output. P (i) -P
(I-1) represents the amount of change per sampling of the pressure value, and compliance Cp is the pressure change amount of the armband, that is, the ratio between the pressurization speed and the flow rate sent to the armband. On the other hand, as shown in FIG. 7, in the electromagnetic valve characteristic curve, the relationship between the drive voltage and the flow rate changes depending on the pressure value on the cuff side of the electromagnetic valve. When the armband pressure at the end of the cuff is 200 mmHg, the flow rate for producing the target pressure reduction speed is 5
If it is 00 ml, the solenoid valve drive voltage is determined to be 1.45V from the characteristic curve of FIG. The flow rate at the target pressure reduction speed can be calculated from the compliance as follows. Target flow rate = K × reduced pressure target speed / Cp (9) The constant K includes a proportional relationship between the pump stroke amount and the voltage and a proportional relationship between the reduced pressure target speed and the flow rate, and is determined by experiment. Can do. Next, with reference to a flow chart shown in FIG. 8, the overall operation at the time of measurement of the electronic blood pressure monitor of this embodiment will be described. When the measurement start switch 11b is turned on while the power switch 11a is on, the measurement operation starts, the pressurizing pump 4 is turned on, and pressurization of the armband 2 is started (step). ST1). Thereafter, as the cuff pressure increases, the cuff pressure and the pulse wave superimposed on the cuff pressure are extracted, and the pulse wave feature amount calculation unit 8 obtains pulse wave amplitude data as several pulse wave feature amounts along with the pressurization. It is done. Based on the cuff pressure and some pulse wave amplitude data in the pressurizing process, the blood pressure calculation unit 7 estimates approximate systolic blood pressure and diastolic blood pressure (step ST2), and the pulse wave number is also measured (step ST3). Here, the maximum blood pressure and the minimum blood pressure are used as an example of the feature amount. Based on these estimations and measured data, the decompression speed def-V is calculated and determined by the decompression speed determining section 9 according to the above equation (1) (step ST4). For example, the pressurization target value determination unit 11 calculates the pressurization upper limit value by the above formula (6) (step ST5). In the pressurization process, after calculating the pressure reduction speed and the pressurization upper limit value, pressurization is continued until the cuff pressure reaches the pressurization upper limit value (step ST6). When the cuff pressure reaches the upper limit of pressurization (step ST6), the pressurization pump 4 is turned off, compliance is determined from the pressure change during pressurization and the pump drive voltage (step ST7), and then the target flow rate is calculated. (Step ST8), the solenoid valve initial drive voltage is determined (Step ST9), and pressure reduction is started (Step ST1).
0). When entering the depressurization process, the depressurization control unit 14 adjusts the depressurization speed so as to become the depressurization speed already calculated in the pressurization process. After starting the decompression, as shown in FIG. 3, the cuff pressure is detected, the pulse wave is extracted, and the pulse wave amplitude data is extracted. When the required number of pulse wave amplitude data is obtained, a well-known algorithm, for example, the cuff pressure corresponding to the maximum value of the pulse wave amplitude is the average blood pressure, and the envelope of the pulse wave amplitude on the side where the cuff pressure is higher than the average blood pressure The cuff pressure at the point where the line crosses the threshold value is determined as the maximum blood pressure, and the cuff pressure at the point where the pulse wave amplitude envelope crosses the threshold value is determined as the minimum blood pressure on the side where the cuff pressure is lower than the average blood pressure. Thus, blood pressure is determined (measured) (step ST11). In this embodiment, the blood pressure measurement algorithm is not particularly limited, and various other methods may be adopted. When the blood pressure measurement is completed (step ST1
2) The measured systolic blood pressure, diastolic blood pressure, pulse wave number, etc. are displayed on the display unit 18 (step ST13), the electromagnetic exhaust valve 5 is opened and exhausted rapidly (step ST14), and the operation is terminated. The inventors have confirmed by actual measurement that the systolic blood pressure and the pulse pressure have a proportional correlation as shown in FIG. FIG. 10 is a diagram showing a cuff pressure change characteristic for comparing the decompression speeds of a conventional general electronic blood pressure monitor, a conventional electronic blood pressure monitor capable of controlling the decompression speed, and the electronic blood pressure monitor according to the present invention. . The characteristic a is due to a conventional general slow exhaust valve, and is a pressure reduction speed of 3.19 mmHg / sec. The characteristic b has a conventional decompression speed control function, and its limit is 5.5 mmHg / sec. Characteristic c is
Each embodiment of the present invention is an electronic sphygmomanometer, and shows a decompression speed of 11 mmHg / sec. Depending on the subject, even if the decompression speed is increased, measurement can be performed with sufficient accuracy. It is. Even when compared with a conventional pressure-reducing speed controllable, measurement can be performed at twice the speed. According to the present invention, the pressure rise measurement during pressurization is performed.
From the amount of operation of the fluid pressurizing means
Compliant with information on the biological characteristics of the compression part
Compliance calculated by anance measurement means and pre-set
Pressurization using the specified characteristics of the fluid pressure control means
Immediately after the start of pressure reduction from the end pressure, the pressure reduction target speed is reached.
Determine the initial value given to the fluid pressure control means
Since the fluid pressure control means instructs the initial value of the feature value at the start of decompression, it is possible to perform stable decompression control immediately at the decompression target speed immediately after the pressurization, and waste until control stabilization There is no need for time and extra pressurization, measurement can be performed with the minimum necessary time and pressurization, and accuracy is not impaired.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a circuit configuration of an electronic blood pressure monitor according to an embodiment of the present invention. FIG. 2 is a perspective view showing an appearance of the electronic blood pressure monitor according to the embodiment. FIG. 3 is a view showing temporal changes in armband pressure extracted by the electronic blood pressure monitor according to the embodiment. FIG. 4 is a diagram for explaining temporal changes in armband pressure, pulse wave amplitude, and representative pressure in the pulse wave in the electronic sphygmomanometer according to the embodiment. FIG. 5 is a diagram showing a pulse wave waveform with normalized amplitude. FIG. 6 is a diagram showing a relationship between armband pressure and pulse wave width ratio. 7 is a diagram showing voltage-flow rate characteristics of an electromagnetic valve of the electronic blood pressure monitor shown in FIG. 1. FIG. FIG. 8 is a flowchart for explaining the overall operation of the electronic blood pressure monitor according to the embodiment; FIG. 9 is a diagram showing the relationship between systolic blood pressure and pulse pressure based on actually measured data. FIG. 10 is a depressurization characteristic diagram comparing the depressurization speeds of a conventional electronic sphygmomanometer and the electronic sphygmomanometer of the present invention. [Explanation of Symbols] 1 Blood pressure monitor body 2 Arm band 3 Pressure sensor 4 Pressure pump 5 Electromagnetic valve 6 Pulse wave detection unit 7 Pressure detection unit 8 Pulse wave feature amount calculation unit 9 Decompression speed determination unit 10 Pulse wave period calculation unit 11 Pressurization target value determination unit 12 Pressurization control unit 13 Depressurization control initial value setting unit 14 Depressurization control unit 15 Blood pressure determination unit 16 Solenoid valve characteristic curve 17 Operation unit 18 Display unit

─────────────────────────────────────────────────── ─── Continuation of Front Page (72) Inventor Akira Nakagawa 801 Shiomoji-dori, Horikawa-shi, Shimogyo-ku, Kyoto City 801, Omron Life Sciences Research Institute (72) Inventor Yoshinori Miyawaki Torihori, Shiokoji-dori, Shimogyo-ku, Kyoto 801 Minamifudo-do, OMRON LIFE SCIENCE LABORATORIES, INC. (56) References JP 5-84221 (JP, A) JP 6-319707 (JP, A) (58) Fields surveyed (Int.Cl ⁷ , DB name) A61B 5/02-5/0295

Claims (1)

(57) [Claims] [Claim 1] An apparatus for determining blood pressure in a process in which at least a part of an artery of a human body is pressurized to a pressure higher than a maximum blood pressure using a fluid pressurizing means and then gradually reduced. In the electronic sphygmomanometer comprising fluid pressure control means for controlling the pressure reduction rate by adjusting the flow rate of the fluid, pressure force change information detecting means for detecting pressure force change information during pressurization, and at the time of pressurization Pressure rise measurement, fluid pressurization means operating amount from human body
Information on the wearing state of the compression part and the biological characteristics of the compression part are added.
Compla calculated by tasted compliance measuring means
Ians and characteristics of preset fluid pressure control means
Immediately after starting the pressure reduction from the pressure end pressure.
The first time to give the fluid pressure control means to reach the target pressure
Determining the period value, the electronic sphygmomanometer, characterized in that the initial value of the characteristic amount at the start of pressure reduction and a speed control initial value determining means for instructing said fluid pressure control means.