JP4607547B2 - Pressure control method and pulse wave discrimination method for electronic sphygmomanometer - Google Patents

Description

  The present invention relates to a pressure control method for an oscillometric electronic sphygmomanometer that detects a pulse wave amplitude value in the process of compressing an artery with a cuff and changes the cuff pressure, and determines the blood pressure using the pulse wave amplitude value, and The present invention relates to a pulse wave discrimination method.

  In an oscillometric electronic sphygmomanometer, a cuff is wrapped around the upper arm or wrist of the subject to be measured, the cuff is pressurized and the artery is compressed to block the blood, and the pressurization process or the process of depressurization thereafter, While detecting the cuff pressure with the pressure sensor, the pulse wave component superimposed on the cuff pressure signal is extracted, and the blood pressure is determined based on the transition of the pulse wave amplitude and the cuff pressure. For example, the cuff pressure corresponding to the maximum value of the pulse wave amplitude is the average blood pressure, the cuff pressure corresponding to the pulse wave amplitude on the high cuff pressure side corresponding to 50% of the maximum value of the pulse wave amplitude is the maximum blood pressure, and the pulse wave amplitude The cuff pressure corresponding to the pulse wave amplitude on the low cuff pressure side corresponding to 70% of the maximum value is determined as the minimum blood pressure.

  In order to measure accurate blood pressure in this type of electronic sphygmomanometer, the cuff pressure must be increased or decreased at a constant rate. In other words, in the case of a sphygmomanometer that measures blood pressure during the slow pressurization process, the current cuff pressurization speed by the pressurization means is monitored and a predetermined pressurization speed (the pressurization speed is constant) The pressurizing means must be controlled so that For example, when the discharge amount of the pressurizing means is proportional to the input current, when the pressurizing speed is too fast, the pressurizing means is decreased by reducing the current of the pressurizing means, and when the pressurizing speed is too slow, the pressurizing means The current is increased to increase the pressurization.

  In addition, in the case of a sphygmomanometer that measures blood pressure in the slow depressurization process after pressurization, the current depressurization rate of the cuff is monitored and the predetermined depressurization rate (depressurization rate is constant) The motorized exhaust valve must be controlled. For example, when the valve opening of the electric exhaust valve is proportional to the input current, when the exhaust speed is too high, the electric exhaust valve current is increased to slow down the exhaust, and when the exhaust speed is too slow, the electric exhaust valve current It is controlled to reduce exhaust and speed up exhaust. Depending on the type of the electric exhaust valve, the control input may be a voltage value or a duty value instead of the current.

  As a method for controlling the pressurization speed and decompression speed, conventionally, before the pulse wave is generated, the pressurization speed and decompression speed are detected based on the pressure difference per unit time (difference between the detected cuff pressure and the target cuff pressure). Then, the energization (current) of the pressurizing means and electric exhaust valve is controlled, and after the pulse wave is generated, the pressurization speed and pressure are reduced by the pressure difference (difference between the detected cuff pressure and the target cuff pressure) immediately before each pulse wave rises. The speed is detected and the energization (current) of the pressurizing means and the electric exhaust valve is controlled. In other words, the pressurization speed and pressure reduction speed are calculated from the pulse wave-to-pulse wave interval (time) and the rising pressure value, and the energization control of the pressurizing means and the electric exhaust valve is performed only once per pulse wave. (See, for example, Patent Document 1). The reason for this is that when the pressurizing means and the electric exhaust valve are controlled based on the cuff pressure where the pulse wave is present, the detected value of the cuff pressure at that time itself is the baseline (the line used as the reference for pulse wave determination). This corresponds to a change curve of the cuff pressure when there is no pulse wave), and the pressurization speed control and the decompression speed control are not properly performed.

Next, as a conventional example, a pressure control method and a pulse wave discrimination method in the measurement method during pressurization will be described.
FIG. 10 shows a change curve of the cuff pressure at the time of blood pressure measurement.
The whole is divided into three sections: (A) rapid pressurizing section, (B) constant speed pressurizing section, and (C) rapid exhaust section.
(A) The rapid pressurization section is from the measurement start (pressurization start) until the cuff pressure reaches the predetermined value P1.
(B) The constant speed pressurization section is from the cuff pressure P1 to the end of measurement (end of blood pressure detection).
(C) The rapid exhaust period is from the end of measurement to the end of exhaust.

  The cuff pressure P1 is a cuff pressure value at which constant speed pressurization (pulse wave detection) is started, and is set to a value lower than the lowest possible minimum blood pressure value. As an example, 25 mmHg is set.

(B) The constant speed pressurization section is divided into three sections (1) to (3) due to a difference in control.
In each step (1) to (3) in the figure, the control method is different.
(1) Control in a section where no pulse wave is detected:
As shown in FIG. 11, in this section, the discharge amount of the pressurizing means (pressurizing pump) is controlled every predetermined time interval T (Example: 250 mSec.).
The target cuff change amount dp during time Tn is compared with the actual cuff pressure change amount dp1,
dp1> dp: Decreases the discharge rate of the pressure pump (in the case of the figure).
dp1 <dp: Increase the discharge rate of the pressure pump.
dp1 = dp: The discharge amount of the pressure pump is maintained.

As the discharge control amount of the pressurizing means for the difference between dp and dp1, a numerical value obtained empirically for each cuff volume (size) or cuff pressure value at the time of control is used as a function.
The target cuff pressure change curve is defined as a change curve (Example: 4 mmHg / Sec.) Having a constant speed pressurization characteristic starting from the constant speed pressurization start point P1 (Example: 25 mmHg).

(2) Control immediately before and after the first pulse wave is detected:
As shown in FIG. 12, the time Tf from the last discharge amount correction until the first pulse wave is detected is a predetermined amount (Example: 1/3) of the discharge amount control cycle T (Example: 250 mSec.). ) In the following cases, the discharge amount by T (n) / dp is maintained.
When Tf exceeds a predetermined value of T (Example: 1/3), the ejection amount is corrected with the correction value obtained from Tf / dpf at the time of detecting the pulse wave.

(3) Control while pulse wave is detected:
As shown in FIG. 13, the detection interval T (Int (n)) between the preceding pulse wave P (n-1) and the following pulse wave P (n), and the preceding pulse wave P (n-1) and the following pulse wave. The discharge amount is corrected when the trailing pulse wave P (n) is detected with the correction amount obtained from the cuff pressure difference dpp (n) when the pulse wave P (n) is detected. This is performed every time a pulse wave is detected.

Moreover, as shown in FIG. 14, the detection of the pulse wave is performed as follows.
(A) The cuff pressure P (n) is sampled at equal intervals t.
(B) Average pressure difference for each sampling obtained from the pressure difference dpH (n) between the current value P (n) of the cuff pressure and the cuff pressure value PH before the predetermined time H (Example: 3t). dp (n) (Example: dpH (n) / 3) is determined for each sampling of the cuff pressure P (n).
(C) At the same time, a value dpst (n) (Example: 1.3 to 1.5 dp (n)) larger than the average pressure difference dp (n) by a predetermined amount is obtained, and the cuff pressure added to the current value P (n) of the cuff pressure Set the value PTHR (n) to the pulse wave threshold value.
(D) Here, when the next cuff pressure value dp (n + 1) exceeds the pulse wave threshold value PTHR (n), the flow proceeds to pulse wave detection with P (n) as a base point. (Detects the rise of the pulse wave)
(E) The cuff pressure sampling is continued, and the leading cuff pressure dp (n) and the trailing cuff pressure dp (while satisfying the condition of the leading cuff pressure dp (n) <the trailing cuff pressure dp (n + 1) A value obtained by adding the pressure difference dp (n) of n + 1) (dp1 to dp3 in the figure) is detected as a pulse wave amplitude value.
(F) When the cuff pressure value dp (n) does not exceed the pulse wave threshold value PTHR (n), the operations (a) to (d) are repeated.

JP-A-6-47011

By the way, the above conventional control method has the following problems.
First, in the measurement method during pressurization, while the pulse wave is not detected, the discharge amount of the pressurizing means is controlled at predetermined time intervals, but after the pulse wave detection is started, it is performed only for each pulse wave cycle. The discharge rate cannot be controlled, especially when the subject's pulse rate is low, and the discharge rate control interval becomes coarse. As a result, in some cases, the baseline when detecting the pulse wave component from the cuff pressure change curve The sphygmomanometer itself caused fluctuations, which contributed to hindering measurement accuracy. In addition, if the subject's pulse rate is low, or if the pulse wave is not detected for a predetermined period of time after the start of pulse wave detection, there is a problem that control delay occurs and control cannot be performed correctly at the predetermined slow pressurization speed. It was.

  In addition, in terms of pulse wave detection, the baseline fluctuation accompanying discharge amount control may be erroneously detected as a pulse wave, and in such a case, an erroneous inclination different from the original baseline is derived, As a result, there was a problem that control was further disturbed. In addition, when the baseline fluctuation accompanying the discharge amount control overlaps with the actual pulse wave, there is a problem that the amplitude of the actual pulse wave signal cannot be captured correctly. In particular, the rising point of a pulse wave having a small amplitude may not be accurately captured. In this case, the pulse wave cannot be captured, or an error is caused in the amplitude value. Moreover, the pulse wave capture sensitivity depends on the pulse wave threshold value, and if it is reduced, the pulse wave capture sensitivity increases, but it is more susceptible to the baseline fluctuation caused by the discharge amount control of the pressurizing means. The evil that coexisted.

  Similarly, in the case of the measurement method during decompression, the electric exhaust valve is controlled every predetermined time while the pulse wave is not detected. However, after the pulse wave detection is started, the electric exhaust valve is operated only for each cycle of the pulse wave. The control interval of the motorized exhaust valve becomes rough, especially when the subject's pulse rate is low, and as a result, the baseline fluctuation when detecting the pulse wave component from the cuff pressure change curve The sphygmomanometer itself invited it, which contributed to hindering measurement accuracy. In addition, when the pulse rate of the subject is low, or when the pulse wave is not detected for a predetermined time after the start of pulse wave detection, there is a problem that control delay occurs and the control cannot be performed correctly at a predetermined very low pressure reduction speed.

  In addition, in terms of pulse wave detection, the baseline fluctuation accompanying the control of the motorized exhaust valve may be erroneously detected as a pulse wave. In such a case, an erroneous inclination different from the original baseline is derived. As a result, the problem that the control is further disturbed occurred. Further, when the baseline fluctuation accompanying the control of the electric exhaust valve overlaps with the actual pulse wave, there is a problem that the amplitude of the actual pulse wave signal cannot be captured correctly. In particular, the rising point of a pulse wave having a small amplitude may not be accurately captured. In this case, the pulse wave cannot be captured, or an error is caused in the amplitude value. In addition, the pulse wave capture sensitivity depends on the pulse wave threshold value.If the pulse wave capture sensitivity is reduced, the pulse wave capture sensitivity increases, but it is easily affected by the baseline fluctuation caused by the control of the electric exhaust valve. Also coexisted.

  In consideration of the above circumstances, the present invention can control the pressurization speed and the decompression speed to be constant regardless of the presence or absence of a pulse wave, thereby improving the blood pressure measurement accuracy. An object is to provide a pressure control method and a pulse wave discrimination method.

  The pressure control method according to the first aspect of the present invention includes a cuff that compresses a living artery, a pressurizing unit that can pressurize the cuff at a low speed, a pressure sensor that detects cuff pressure, and a pulse wave in the process of pressurizing the cuff at a low speed. Blood pressure calculation means for analyzing the signal from the superimposed pressure sensor to determine the blood pressure value, sampling the cuff pressure at equal intervals, and adding the cuff pressure during the slow pressurization and the time In a pressure control method for an electronic sphygmomanometer that obtains a pressure speed and feedback-controls the pressurizing means so that the slow pressurization speed becomes the target pressurization speed based on the difference between the fine pressurization speed and the target pressurization speed. After rapid pressurization to the specified pressure from the start of measurement, shift to fine pressure pressurization and measure the cuff pressure every sampling from the base point with one point determined arbitrarily after shifting to the fine pressure pressurization. To the base point The pressure difference between the pressure value at the measurement point and the pressure value at the measurement point, and the time difference from the base point to the measurement point, the pressurization speed is obtained, and the obtained pressurization speed is sampled every time the cuff pressure is sampled. A predetermined number is stored together with the corresponding pressure value data, and the value from the oldest data in the stored section where the pressurization speed in the predetermined section is the smallest, and the latest section in the stored section is stored in the predetermined section. The value with the smallest pressurization rate is extracted, the average pressurization rate is obtained from the pressure value corresponding to these two points of data and the time difference, and the difference between the calculated average pressurization rate and the target pressurization rate Based on the above, the pressurizing means is feedback-controlled so that the fine pressurizing speed becomes a predetermined target pressurizing speed.

  A pulse wave discrimination method according to a second aspect of the present invention provides a current cuff pressure value during slow pressurization and a cuff of a predetermined time before the pulse wave is detected by performing the pressure control method according to the first aspect. An average pressure difference for each sampling obtained from the pressure difference with the pressure value is obtained for each cuff pressure sampling, and at the same time, a value larger than the average pressure difference by a predetermined amount is added to the current cuff pressure value to obtain the value. When the pulse wave threshold value is set and the cuff pressure value by the next sampling exceeds the pulse wave threshold value, the pulse wave detection is started from the previous sampling point, and one of the cuff pressure values from the preceding sampled cuff pressure value. When a state in which the cuff pressure value that is later sampled is large continues for a predetermined time or a predetermined number of times, it is determined that the pulse wave is detected, and the subsequent sampling is performed one time after the cuff pressure value that has been sampled in advance. In the cuff pressure value is greater state lasted interval has a value obtained by cumulative addition of the pressure difference between the preceding cuff pressure value and the following cuff pressure value, and calculates a pulse wave amplitude value.

  According to a third aspect of the present invention, there is provided a pressure control method comprising: a cuff that compresses a living artery; a pressurizing pump that pressurizes the cuff; an electric exhaust valve that depressurizes the cuff; a pressure sensor that detects the cuff pressure; A blood pressure calculation means for analyzing a signal from the pressure sensor on which a pulse wave is superimposed in the process and calculating a blood pressure value, and obtaining a slow depressurization speed from the pressure decrease amount of the cuff during depressurization and its time, and the slow depressurization In the pressure control method of the electronic sphygmomanometer that feedback-controls the electric exhaust valve so that the slow depressurization speed becomes the target depressurization speed based on the difference between the speed and the target depressurization speed. Then, the cuff pressure is measured every sampling from the base point as one base point arbitrarily determined after shifting to the slow pressure reduction, and the pressure value at the base point and the pressure at the measurement point are measured. The pressure reduction speed is obtained from the pressure difference from the value and the time difference from the base point to the measurement point, and each time the cuff pressure is sampled, the determined pressure reduction speed together with the corresponding pressure value data. Store and extract the largest value of the decompression speed in the predetermined section from the oldest data in the stored section and the largest value of the decompression speed in the predetermined section from the latest data in the stored section. Thus, an average decompression speed is obtained from the pressure value corresponding to the data at these two points and the time difference, and based on the difference between the obtained average decompression speed and the target decompression speed, the fine decompression speed becomes the predetermined target decompression speed. The electric exhaust valve is feedback-controlled.

  According to a fourth aspect of the present invention, when the pulse wave is detected by executing the pressure control method according to the third aspect of the present invention, the current cuff pressure value during the slow depressurization and the cuff pressure a predetermined time before that are detected. An average pressure difference for each sampling obtained from the pressure difference with the value is obtained for each cuff pressure sampling, and at the same time, a value larger than the average pressure difference by a predetermined amount is added to the current cuff pressure value, and the value is pulsed. When the cuff pressure value is set to the wave threshold value and the cuff pressure value by the next sampling exceeds the pulse wave threshold value, the pulse wave detection is started from the previous sampling point, and one cuff pressure value after the cuff pressure value sampled in advance. It is determined that the pulse wave has been detected when a state in which the cuff pressure value that has been sampled is large continues for a predetermined time or a predetermined number of sampling times, and the subsequent sampling is performed one time after the cuff pressure value that has been sampled in advance. In the cuff pressure value is greater state lasted interval has a value obtained by cumulative addition of the pressure difference between the preceding cuff pressure value and the following cuff pressure value, and calculates a pulse wave amplitude value.

  According to the present invention, in a sphygmomanometer that measures blood pressure during slow pressurization or a blood pressure meter that measures blood pressure during slow depressurization, a true baseline (pulse) that is not affected by the pulse wave superimposed on the pressure. It is a line used as a reference for wave judgment, and the slope of the cuff pressure change curve when there is no pulse wave can be extracted, so the target fine pressurization speed or the target fine depressurization speed can be accurately obtained. Can be controlled. As a result, the pulse wave can be discriminated with high accuracy, the measurement stability is improved, and high-accuracy measurement is possible.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of an electronic blood pressure monitor of a blood pressure measurement system during pressurization used here, and FIG. 2 is a diagram showing a relationship between sampling and cuff pressure. 3-8 is explanatory drawing of the control method of this invention.

  As shown in FIG. 1, this sphygmomanometer includes a cuff 1 that compresses a living artery, a pressurizing pump (pressurizing means) 2 that can pressurize the inside of the cuff 1 at a very low speed (variable discharge amount), and a cuff 1. Electric exhaust valve 3 for reducing the pressure inside, pressure sensor 4 for detecting the pressure in the cuff 1 (cuff pressure), control means 10 comprising a microcomputer for performing general control calculation processing, and control from the control means 10 A drive circuit 11 for a pressure pump that receives a command and supplies a drive signal to the pressure pump 2, and a drive for an electric exhaust valve that receives a control command from the control means 10 and supplies a drive signal to the electric exhaust valve 3 A circuit 12, an A / D converter 13 that converts the analog output of the pressure sensor 4 into a digital signal and inputs it to the control means 10, an input operation unit 16 such as operation keys, and a display unit 17 such as a liquid crystal display device. It has.

  The control means 10 provides a control signal to the pressurization pump 2 and the electric exhaust valve 3 based on a signal from the pressure sensor 4 to control each operation (corresponding to the pressurization pump control means and the exhaust valve control means). In the process of pressurizing or depressurizing the cuff 1 by the pressurizing pump 2 or the electric exhaust valve 3, a function of analyzing a detection signal from the pressure sensor 4 on which the pulse wave is superimposed and calculating a blood pressure value (for the blood pressure calculating means) Equivalent). Further, it has a function of displaying various information to be displayed on the display unit 17, a function of executing various commands in response to an input from the input operation unit 16, and the like.

Next, the contents of control will be described.
This sphygmomanometer has a function of advancing the processing in the following order when a blood pressure measurement trigger is given at some timing with the cuff 1 wrapped around the wrist or upper arm.

(1) Pressurization by the pressurization pump 2 starts with the start of measurement. During the pressurizing operation, the cuff pressure P (n) is sampled at equal intervals t as shown in FIG.
P (n): Cuff pressure value for each sampling t: Sampling interval (Example: 30 mSec.)

(2) As shown in FIG. 3, a reference cuff pressure value P (0) that is a constant velocity pressurization start reference point is set.
-The cuff pressure value at which constant-speed pressurization is started is a value that is lower than the subject's minimum blood pressure, and an optimum value obtained experimentally in consideration of the minimum blood pressure of the subject to be measured is used.
・ The discharge rate of the pressurization pump immediately after the start of constant speed pressurization shall be an appropriate value obtained empirically from the cuff size to be used, the cuff pressure value to start constant speed pressurization, etc., and pressurization with that discharge amount To start.
・ P (0) can stabilize the operation by setting the cuff pressure value after the elapse of the predetermined time B from the start of constant speed pressurization or the cuff pressure value when the predetermined pressure A rises from the start of constant speed pressurization. it can. Note that the position of P (0) can be set as an arbitrary point after shifting to constant speed pressurization.

  (3) Thereafter, as shown in FIG. 4, each time the cuff pressure value P (n) is sampled, the pressure difference dP (n) from the reference cuff pressure value P (0) and the reference cuff pressure value P (0) The elapsed time T (n) from the set time point is obtained, and the slope dP / dt (n) with the reference cuff pressure value P (0) as a reference is obtained. Each value is stored in memory.

(4) The storage in the memory is performed as follows.
First, a data window (DW) is defined.
The memory is a register that can store the cuff pressure value P (n) and the cuff pressure value slope dP / dT (n) corresponding to the pulse wave detection interval at the lowest measurable pulse rate and a predetermined time width longer than that. Consists of.
Example: When the minimum pulse rate is 40 beats / minute, DW ≧ 1.5 Sec.
・ As shown in Fig. 5, the data window (DW) is filled with P (n) and dP / dT (n) data (numbers in the figure) in order from the oldest data. After that, the old data is sequentially discarded and updated to new data. In FIG. 5, the number of data as an example is displayed smaller than the actual number of data for the purpose of illustration.

(5) Next, a true cuff pressure change curve for controlling the discharge amount is obtained.
In this case, first, as shown in FIG. 6 (a), the cuff pressure gradient data dP / dT (n) accumulated on the data window has a predetermined time Tf (example: 500 mSec) from the oldest data. .) DP / dT (n), the smallest dP / dT (n) value is extracted, and the cuff pressure P (n) corresponding to the data is changed to the preceding cuff pressure P (f). decide.
Next, as shown in FIG. 6 (b), among the cuff pressure gradient data dP / dT (n) accumulated on the data window, the newest data is used for a predetermined time Te (Example: 500 mSec.). DP / dT (n) is extracted, the smallest dP / dT (n) value is extracted, and the cuff pressure P (n) corresponding to the data is determined as the subsequent cuff pressure P (b). To do.
Here, as shown in FIG. 8, the time width of the leading edge window Tf and the trailing edge window Te of the data window DW is a time width including one pulse wave. In the embodiment, 500 mSec.
Next, P (f) and P (b) are detected by the above procedure every predetermined time, and from the pressure difference dP and time difference dT between P (f) and P (b) as shown in FIG. The true slope of the cuff pressure change curve between the obtained P (f) and P (b) is obtained. As shown in FIG. 7, the inclination in this case is defined with P (0) as a base point. When this inclination is plotted, the lower diagram in FIG. 7 is obtained.
Note that memory can be saved by configuring the cuff pressure and tilt data so that they are directly stored in the data window instead of being stored in memory.

(6) Next, the discharge amount is controlled.
・ Comparing the true slope of the cuff pressure change curve obtained in the above procedure with the target slope, appropriate values obtained empirically based on the size of the cuff used, the cuff pressure at the time of correction, etc. The discharge amount is controlled with a correct correction amount.
-Although the discharge amount is controlled every predetermined time, the slope of the true cuff pressure change curve has a large difference from the target slope of the cuff pressure curve, and if the correction is performed at once, the baseline fluctuation may occur. If there is, the discharge amount is controlled in a plurality of times.

Specific examples will be described below.
(1) When the pressurization start key in the input operation unit 16 is pressed, the display unit 17 is fully displayed for a predetermined time, and then the pressure value when the atmospheric pressure is released (no pressure applied) is read as a pressure zero set value. For example, 0 is displayed in the first digit of the maximum blood pressure value display area of the display unit 17. In this embodiment, by using a capacitance type sensor and incorporating the capacitance type sensor as a part of the transmitter, the pressure change is taken into the control means 10 (hereinafter referred to as CPU) as a change in the transmission frequency. Detect cuff pressure and pulse wave. Note that a semiconductor pressure sensor using a piezoresistor may be used as the pressure sensor, and the pressure sensor may be amplified to a predetermined level and taken into the CPU by A / D conversion.

  (2) After zero setting, the CPU outputs a drive signal to the pump drive circuit and the electric exhaust valve drive circuit, the electric exhaust valve is held in a fully closed state, and the pump is driven to start pressurization. The pressure value during pressurization is updated and displayed on the display unit.

  (3) When pressurization is started and the CPU determines that the pressure has reached a predetermined value, the CPU outputs a predetermined initial value to the pressurization pump drive circuit so as to achieve a predetermined fine pressurization speed. Here, the initial value is determined empirically. Pressurization speed measurement is performed at a pressure value at a point where a predetermined value (eg 5 mmHg) pressure has increased from the point at which fine pressure pressurization has started, or when a predetermined time (1 second) has elapsed since the start of slow pressure pressurization. It is memorized as the base point.

  (4) Every time the pressure value is sampled from the starting point of the pressurization control, the CPU determines the per-sampling from the differential pressure between the latest value and the reference value and the elapsed time (1 sampling time × sampling count). The inclination (pressurization amount dP) is calculated and stored in the RAM together with the latest pressure value data. At this time, if the data to be stored is equal to or greater than the period of the lowest measurable pulse extraction number (for example, 40 beats / minute), a baseline connecting regions that are not affected by the pulse wave can be obtained. In the embodiment, it is 1.5 seconds. Each time the pressure value sampling progresses, the data shifts and the oldest data is deleted and updated.

(5) After storing the dP for a predetermined time, the CPU extracts the data with the smallest inclination from the data within the predetermined time (eg, 500 mSec.) From the oldest dP data, The corresponding pressure value data P (f) is extracted. Similarly, data having the smallest slope in the data from the latest dP data to a predetermined time (eg, 500 mSec.) Before is extracted, and pressure data P (b) corresponding to the data is extracted.
・ Next, calculate the pressure difference between Pf and Pb. [DPX = P (b) -P (f)]
-Find the time between P (f) and P (b).
The CPU can determine from the RAM position where P (f) is stored what number of data is counted from the latest pressure sampling data, and similarly, what number P (b) is. Since it is possible, the difference sampling number × sampling period is calculated, and the time Xt between P (f) and P (b) is obtained by calculation.
・ From Xt and dPX, find the slope equivalent to one sampling. This value is the true baseline slope desired. [DPX / Xt]

(6) The CPU corrects the control output in accordance with the difference between the slow pressure target value and the true slope obtained in (5), and outputs the correction output to the pressure pump driving circuit, so that sampling proceeds. Each time, the above process is repeated to control the pressurization speed.
The output timing of the control signal is performed every predetermined time. If the difference is large, the control output value is not changed at a time, but the fluctuation of the base line during pressurization is suppressed, and the control signal value is greater than a predetermined amount. In this case, the output should be changed in time division.

(7) Discrimination of pulse wave The difference between the pressure difference between the latest pressure value data P1 and the previous pressure value P2 and the baseline dPX / Xt is obtained. As there is, the pulse wave discrimination process is started.
・ Start the pulse wave discrimination process to determine whether the pulse wave during discrimination is a true pulse wave. It may be determined by confirming whether or not there is no pressure increase with respect to the base line more than a predetermined number of times, which is not possible as a human pulse wave, and by confirming an amplitude value or the like.
When it is determined by the above processing that the pulse wave is correct, the CPU stores the pulse wave amplitude value discriminated from the start pressure of the pulse wave discrimination processing in the RAM.

(8) The above-described slow pressurization control and pulse wave discrimination are repeated until the measurement end condition is reached.
(9) When the measurement end condition is satisfied, the CPU calculates the blood pressure value by the oscillometric method and displays the result on the display unit. Details of the determination of the blood pressure value are the same as those of a conventionally known technique, and thus description thereof is omitted.

  In the above-described embodiment, the case of controlling the blood pressure measurement method during pressurization has been described, but the present invention can be similarly applied to the case of controlling the blood pressure measurement method during decompression. In that case, after pressurizing to a predetermined pressure, the process shifts to a slow depressurization, and a point after a predetermined time has passed or a predetermined pressure has been lowered (which can be arbitrarily determined) is cuffed every sampling from that base point. The pressure is measured, the pressure reduction rate is obtained from the pressure difference between the pressure value at the base point and the pressure value at the measurement point, and the time difference from the base point to the measurement point, and the cuff pressure is sampled based on the obtained pressure reduction rate. Each time, a predetermined number is stored together with the corresponding pressure value data, and from the oldest data in the stored section, the value with the highest decompression speed in the predetermined section and the latest data in the stored section The value with the largest decompression speed in the predetermined section is extracted, the average decompression speed is obtained from the pressure value corresponding to these two points of data and the time difference, and based on the difference between the obtained mean decompression speed and the target decompression speed. Fine Decompression speed feedback control of the electric exhaust valve so that a predetermined target decompression rate.

A specific embodiment in this case will be described.
(1) When the pressurization start key in the input operation unit 16 is pressed, the display unit 17 is fully displayed for a predetermined time, and then the pressure value when the atmospheric pressure is released (no pressure applied) is read as a pressure zero set value. For example, 0 is displayed in the first digit of the systolic blood pressure value display area of the display unit.

  (2) After zero setting, the CPU outputs a drive signal to the pump drive circuit and the electric exhaust valve drive circuit, the electric exhaust valve is held in a fully closed state, and the pump is driven to start pressurization. The pressure value during pressurization is updated and displayed on the display unit.

  (3) When the CPU determines that the pressurization is started and the pressure has reached the pressure set value (eg, 180 mmHg), the CPU stops the pressurization pump and the depressurization speed is a predetermined fine depressurization speed. A predetermined initial value is output so that The reference value for starting the fine speed control is the pressure value at the point where it has been determined that the pressure has dropped by a predetermined value (eg 10 mmHg) from the point at which fine pressure pressurization has started, or the predetermined time (eg: 1 second) has elapsed since the start of slow pressure reduction. Remember as.

  (4) Every time the CPU samples the pressure value from the reference point at which decompression starts, the slope per one sampling (pressurization) from the differential pressure between the latest value and the reference value and the elapsed time (one sampling time × sampling count) The amount dP) is calculated and stored in the RAM together with the latest pressure value data. At this time, it is not necessary to store all the data to be stored for the convenience of saving RAM. However, if it is less than the minimum measurable pulse rate (for example, 40 beats / minute), the region is not affected by the pulse wave. Therefore, it is necessary to store data for one beat or more of the lowest measurable pulse rate. In the embodiment, the time is 1.5 seconds. Each time the pressure value sampling progresses, the data shifts and the oldest data is deleted and updated and stored.

(5) After storing the dP for a predetermined time, the CPU extracts the data with the largest inclination from the data within the predetermined time (eg, 500 mSec.) From the oldest data of the dP data. The pressure value data P (f) corresponding to is extracted. Similarly, the data having the largest inclination in the data from the latest dP data to a predetermined time (eg, 500 mSec.) Before is extracted, and the pressure data P (b) corresponding to the data is extracted.
・ Next, calculate the pressure difference between P (f) and P (b). [DPX = P (b) -P (f)]
-Find the time between P (f) and P (b).
The CPU determines the number of data counted from the latest pressure sampling data from the RAM location where P (f) is stored, and similarly the number of data P (b). Therefore, the number of samplings of the difference × sampling period is calculated, and the time Xt between P (f) and P (b) is obtained by calculation.
・ From Xt and dPX, find the slope equivalent to one sampling. This value is the true baseline slope desired. [DPX / Xt]

  (6) The CPU corrects the control output according to the difference between the target value for the slow depressurization and the true slope obtained in (5), and outputs the control output to the electric exhaust valve drive circuit. The pressure rate is controlled by repeating the above process. Note that the timing of the control signal output is performed every predetermined time, but if the difference is large, the control output value is not changed at a time, but the fluctuation of the baseline during pressurization is suppressed, and the predetermined amount or more. If this is the case, the output should be changed in time division.

(7) Discrimination of pulse wave The difference between the pressure difference between the latest pressure value data P1 and the previous pressure value P2 and the baseline dPX / Xt is obtained. Then, the pulse wave discrimination process is started.
・ Start the pulse wave discrimination process to determine whether the pulse wave during discrimination is a true pulse wave. It may be determined by confirming whether there is no excessive pressure rise with respect to the baseline more than a predetermined number of times, which is impossible for a human pulse wave, and by confirming an amplitude value or the like.
When it is determined by the above processing that the pulse wave is correct, the CPU stores the start pressure of the pulse wave discrimination processing and the discriminated pulse wave amplitude value in the RAM.

(8) The above-mentioned slow speed pressure reduction control and pulse wave discrimination are repeated until the end of measurement.
(9) When the measurement end condition is satisfied, the blood pressure value is calculated by the oscillometric method, and the result is displayed on the display unit. (Details about determination of blood pressure are omitted)

It is a block diagram which shows schematic structure of the blood pressure meter for enforcing the method of this invention. It is explanatory drawing of the cuff pressure in the case of performing pressure control of embodiment of this invention, and a sampling period. It is explanatory drawing of the base in the initial stage in the case of the same pressure control. It is explanatory drawing of the inclination of the change curve of the cuff pressure in the case of the same pressure control, and the method of storing data. It is explanatory drawing of the storage order of the data in the case of the same pressure control. It is explanatory drawing of the method of calculating | requiring the true cuff change curve in the case of the same pressure control. It is explanatory drawing of the method of calculating | requiring the true cuff change curve in the case of the same pressure control. It is explanatory drawing of the method of calculating | requiring the true cuff change curve in the case of the same pressure control. It is explanatory drawing of the method of calculating | requiring the true cuff change curve in the case of the same pressure control. It is a characteristic view of conventional pressurization control. It is explanatory drawing of the conventional pressurization control. It is explanatory drawing of the conventional pressurization control. It is explanatory drawing of the conventional pressurization control. It is explanatory drawing for pulse wave discrimination.

Explanation of symbols

1 Cuff 2 Pressure pump (Pressurizing means)
3 Electric exhaust valve 4 Pressure sensor 10 Control means (exhaust valve control means, blood pressure calculation means, pressurization pump control means)

Claims (4)

A cuff that compresses a living artery, a pressurizing means that can pressurize the cuff at a low speed, a pressure sensor that detects the cuff pressure, and a signal from the pressure sensor on which a pulse wave is superimposed in the process of pressurizing the cuff at a low speed Blood pressure calculation means for determining the blood pressure value, sampling the cuff pressure at equal intervals, obtaining the slow pressurization speed from the amount of pressure increase of the cuff during the slow pressurization and the time, In a pressure control method for an electronic sphygmomanometer that feedback-controls the pressurizing unit so that the slow pressurization speed becomes the target pressurization speed based on the difference from the target pressurization speed,
After rapid pressurization to the specified pressure from the start of measurement, shift to fine pressure pressurization and measure the cuff pressure every sampling from the base point with one point determined arbitrarily after shifting to the fine pressure pressurization. The pressure rate is determined from the pressure difference between the pressure value at the base point and the pressure value at the measurement point, and the time difference from the base point to the measurement point,
Each time the cuff pressure is sampled, the determined pressurization speed is stored together with a predetermined number of pressure value data,
Extract the value with the smallest pressurization speed in the predetermined section from the oldest data in the stored section and the value with the smallest pressurization speed in the predetermined section from the latest data in the stored section,
From the pressure value and time difference corresponding to these two points of data, the average pressurization speed is obtained,
The pressure of the electronic sphygmomanometer is characterized in that the pressurizing means is feedback-controlled so that the fine pressurization speed becomes a predetermined target pressurization speed based on the difference between the obtained average pressurization speed and the target pressurization speed. Control method.   When detecting the pulse wave by performing the pressure control method according to claim 1, every sampling obtained from the pressure difference between the current cuff pressure value during the slow pressurization and the cuff pressure value a predetermined time before that The average pressure difference is calculated every time cuff pressure is sampled, and at the same time, a value larger than the average pressure difference by a predetermined amount is added to the current cuff pressure value to set the value as the pulse wave threshold value. When the cuff pressure value exceeds the pulse wave threshold value, pulse wave detection is started from the previous sampling point, and the cuff pressure value sampled subsequent to the preceding sampled cuff pressure value is larger. When a predetermined time or a predetermined number of samplings continues, it is determined that the pulse wave has been detected, and a state in which the cuff pressure value that is sampled subsequent to the cuff pressure value that has been previously sampled is larger is continued. Between the value obtained by cumulative addition of the pressure difference between the preceding cuff pressure value and the following cuff pressure value, the pulse-wave filter method of an electronic blood pressure meter and calculates a pulse wave amplitude value. A cuff that compresses a living artery, a pressurizing pump that pressurizes the cuff, an electric exhaust valve that depressurizes the cuff, a pressure sensor that detects the cuff pressure, and the pressure sensor on which a pulse wave is superimposed in the process of depressurizing the cuff A blood pressure calculation means for analyzing a signal from the blood pressure and calculating a blood pressure value, obtaining a slow depressurization speed from the pressure decrease amount of the cuff during decompression and its time, and based on the difference between the slow depressurization speed and the target decompression speed, In the pressure control method of the electronic sphygmomanometer that feedback-controls the electric exhaust valve so that the slow depressurization speed becomes the target depressurization speed,
After pressurizing to a predetermined pressure, shift to fine pressure reduction, measure cuff pressure every sampling from the base point with one point arbitrarily determined after shifting to slow pressure reduction, and the pressure value at the base point And the pressure difference between the pressure value at the measurement point and the time difference from the base point to the measurement point, the pressure reduction rate is obtained,
Each time the cuff pressure is sampled, the determined pressure reduction speed is stored together with a predetermined number of corresponding pressure value data,
Extracting the largest decompression speed in the predetermined section from the oldest data in the stored section and the largest decompression speed in the predetermined section from the latest data in the stored section,
From the pressure value and time difference corresponding to these two points of data, the average pressure reduction rate is obtained,
A pressure control method for an electronic sphygmomanometer, wherein the electric exhaust valve is feedback-controlled based on a difference between the obtained average pressure reduction speed and a target pressure reduction speed so that a fine pressure reduction speed becomes a predetermined target pressure reduction speed.   In detecting the pulse wave by carrying out the pressure control method according to claim 3, each sampling is obtained from the pressure difference between the current cuff pressure value during the slow depressurization and the cuff pressure value a predetermined time before that. An average pressure difference is obtained for each cuff pressure sampling, and at the same time, a value larger than the average pressure difference by a predetermined amount is added to the current cuff pressure value to set the value as the pulse wave threshold value. When the pressure value exceeds the pulse wave threshold value, pulse wave detection is started from the previous sampling point as a base point, and the state where the cuff pressure value sampled subsequent to the preceding sampled cuff pressure value is large is predetermined. It is determined that the pulse wave has been detected for a time or a predetermined number of times of sampling, and the cuff pressure value that has been sampled subsequent to the cuff pressure value that has been sampled one after the preceding cuff pressure value has continued. Between the value obtained by cumulative addition of the pressure difference between the preceding cuff pressure value and the following cuff pressure value, the pulse-wave filter method of an electronic blood pressure meter and calculates a pulse wave amplitude value.

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