JP2842696B2 - Electronic sphygmomanometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic sphygmomanometer.

[0002]

2. Description of the Related Art An oscillometric electronic sphygmomanometer captures a pulse wave superimposed on a cuff pressure and calculates a blood pressure based on a change in the amplitude. This amplitude change is small when the cuff pressure is sufficiently higher than the systolic pressure (systolic blood pressure), and then increases as the cuff is depressurized, as shown in FIG. (Maximum cuff pressure = mean blood pressure). That is, the pulse wave is at the maximum point / point P. Then it decreases.
The blood pressure is calculated based on the change in the amplitude. In the oscillometric method of calculating the blood pressure based on the amplitude change, such an amplitude change pattern (envelope) is required.
For example, according to a certain method, the systolic pressure (systolic blood pressure) and the diastolic pressure (diastolic blood pressure) are equal to a certain ratio of the maximum value on the high and low pressure sides of the pulse wave amplitude from the maximum point (point P). (S point / D point). That is, unless all three points S, P, and D on the envelope can be captured, the blood pressure cannot be calculated. Capturing all three points means that it is necessary to apply a pressure equal to or higher than the S point before starting the measurement operation. If the pressurization at the S point or higher is not achieved, the absence of the S point is detected at the time of detecting the P point in the blood pressure measurement operation, and the systolic pressure (systolic blood pressure) cannot be calculated, and the measurement fails. Therefore, the user has to re-pressurize at a higher setting and measure again. However, the point S (systolic pressure) is unknown to the user, and it is difficult to predict and appropriately set the pressure by estimating the S point, particularly for a hypertensive subject with remarkable blood pressure fluctuation. If the measurement fails, the measurement takes a long time. Therefore, in the related art, the pressure value is set to be higher than necessary, which often causes the subject to suffer. Also, in order to solve the above problem, a pulse wave signal is detected during the cuff pressurization process, a pulse wave having the maximum amplitude is detected from the pulse wave signal, the cuff pressure at that time is stored, and the cuff pressure value is also measured. An apparatus in which the cuff is pressurized to a value obtained by adding a predetermined value to the cuff has already been filed (Japanese Patent Application No. 63-8646).
No. 5: JP-A 1-256930).

[0003]

The variation in pulse wave amplitude varies greatly between individuals, and the envelope pattern of the pulse wave amplitude sequence sometimes exhibits a very peculiar shape. For example, a flat head is one example. In this case, the maximum point of the pulse wave amplitude giving the average blood pressure (usually, the cuff pressure corresponding to the maximum pulse wave amplitude) becomes unclear, and a large measurement error may occur.
It is well known that the pulse wave amplitude causes rattling due to instantaneous or continuous blood pressure fluctuations (due to respiration, arrhythmia, etc.), but in this case, it is almost impossible to identify the average blood pressure. The above-described conventional automatic pressurization method is based on the premise that the relationship between the average blood pressure and the systolic blood pressure is substantially constant. However, the relationship between the mean blood pressure and the systolic blood pressure varies greatly between individuals and is wide (10 to 100 mmH).
g), unless the predetermined value is set to a considerably large value, the frequency of insufficient pressurization increases. In this case, excessive pressurization is always imposed on a person having an average systolic blood pressure-average blood pressure relationship. As described above, in calculating the pressurization target value to be set for the systolic blood pressure, the conventional method has two error factors—the estimation accuracy of the average blood pressure,
An error in setting the pressurization target from the average blood pressure intervenes. For this reason, there is a problem that it is difficult to reliably set the pressure.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided an electronic sphygmomanometer capable of automatically performing appropriate pressurization in accordance with the blood pressure of a subject by overcoming the above-mentioned drawbacks of operability of an oscillometric sphygmomanometer. With the goal.

[0005]

In order to achieve this object, an electronic sphygmomanometer according to the present invention has the following configuration. An electronic sphygmomanometer determines the blood pressure using a pulse wave obtained from a living body when the cuff is depressurized and a pressure value of the cuff by a pressure sensor. Threshold value calculating means for detecting and calculating a threshold value based on the maximum value, comparing the threshold value calculated by the threshold value calculating means with the pulse wave amplitude during pressurization, Judgment means for judging whether the pulse wave amplitude is smaller than the threshold value, and when this judgment means judges that the pulse wave amplitude during pressurization is smaller than the threshold value, linear interpolation of the pulse wave amplitude is performed. A systolic blood pressure estimating means for setting the pressure value corresponding to the linear complement value to an estimated value of the systolic blood pressure, and a time when the pressure value increases by a predetermined pressure with respect to the estimated value estimated by the systolic blood pressure estimating means. A pressure setting means for stopping the cuff pressure is provided. That.

In an electronic blood pressure monitor having such a configuration,
A pulse wave signal during cuff pressurization is captured, a systole is estimated from a change in pulse amplitude, and pressurization is stopped at an appropriate cuff pressure according to the systolic period. Therefore, the cuff pressurization can be set automatically, so that the subject can be pressurized without excess or shortage, improving operability, speeding up measurement, and reducing pain during measurement. it can.

[0007]

FIG. 4 is a circuit block diagram showing a specific embodiment of the electronic sphygmomanometer according to the present invention.

The electronic sphygmomanometer comprises a cuff 1, a pressurizing pump 2 for pressurizing the cuff 1, a quick exhaust valve 3 for reducing the pressure inside the cuff 1,
The slow exhaust valves 4 are connected via air tubes 5 to form an air system. And this pressurizing pump 2
The quick exhaust valve 3 is electrically connected to an MPU 6 which will be described later, and is driven and controlled. The air tube 5 is provided with a pressure sensor 7. As the pressure sensor 7, for example, a diaphragm converter using a strain gauge, a semiconductor pressure conversion element, or the like is used. The output signal (analog amount) of the pressure sensor 7 is sent to the A / D converter 9 via the low-pass filter 8 and is output to the A / D converter 9.
Is converted to a digital value. This low pass filter 8
Is to remove the pressure noise of the pressure pump 2 mixed in the cuff pressure signal when detecting the pulse wave during the pressurization. The MPU 6 takes in the output signal of the pressure sensor 7 which has been converted into a digital value and from which noise has been removed, at a constant period. The MPU 6 has a pulse wave extraction processing function (a function of capturing a pulse wave from cuff pressure data), a pulse wave amplitude calculation function (a function of recognizing a start point and an end point of a pulse wave for each beat and calculating a pulse wave amplitude), a blood pressure It has a calculation processing function (a function of calculating the maximum and minimum blood pressure values from a plurality of obtained pulse wave amplitudes, that is, envelopes). Further, the MPU 6 calculates a threshold value based on the maximum pulse wave during the cuff pressurization (threshold value for determining the systolic pressure, in this embodiment, 50% of the maximum value Amax of the pulse wave) and the pressure pulse. A function of determining whether the wave is smaller than the threshold value and determining the cuff pressure at the time when the pressurized pulse wave is smaller than the threshold value as an estimated systolic pressure, and an appropriate pressurized value based on the estimated systolic blood pressure. Is calculated, and the cuff pressure is stopped when the cuff pressure becomes equal to the cuff pressure. Also, MPU
Reference numeral 6 has a function of displaying the determined systolic and diastolic blood pressure values on the display 10.

FIG. 1 is a flowchart showing a specific processing operation of the electronic blood pressure monitor of the embodiment. When the power switch and the pressure switch are turned on during the measurement, the pressure of the cuff 1 starts (step (hereinafter, referred to as ST) 1). During the cuff pressurization, based on the output signal of the pressure sensor 7,
The pulse wave is captured, and the starting point and the ending point of the pulse wave are recognized for each beat, and the pulse wave amplitude is calculated. Further, the systolic blood pressure is estimated from the obtained pulse wave envelope. (ST2). In ST3, it is determined whether or not the systolic blood pressure estimated value SP has been determined. If the cuff pressure has not been sufficiently increased and the systolic pressure (SP) has not been determined yet, the determination in ST3 is NO, and ST2 is determined.
Return to Now, if the systolic pressure (SP) is determined,
The determination in ST3 becomes YES, and the process proceeds to the next ST4. ST
In 4, it is determined whether or not the cuff pressure has reached an appropriate pressure application value. That is, it is determined whether or not the current pressure of the cuff 1 during pressurization has reached an appropriate pressurization value according to the determined systolic pressure estimated value. Here, the appropriate pressurization value is a value that is not excessive or insufficient with respect to the estimated systolic pressure value. That is, in consideration of the systolic pressure estimation error and the pressure drop from immediately after the stop of pressurization to the start of the measurement process, for example, a value such as 30 mmHg is added to the systolic pressure and set. If the cuff pressure has not risen to the appropriate pressurization value, the determination in ST4 becomes NO, and pressurization is continued until the cuff pressure reaches the proper pressurization value. When the cuff pressure reaches the appropriate pressurization value, the determination in ST4 becomes YES, the driving of the pressurizing pump 2 is stopped, and the pressurization is completed (ST4).
5). Then, the cuff 1 is evacuated at a very low speed, and the process proceeds to the measurement process (ST6). In this slow exhaust process, pulse wave extraction, pulse wave amplitude calculation, and blood pressure calculation processing are executed in the same manner as the processing during pressurization (ST7). In ST8, the diastolic blood pressure value DP
(Including the systolic blood pressure value) is determined. This process is continued until the systolic and diastolic blood pressures in the cuff evacuation process are calculated, and the diastolic pressure (diastolic pressure) is calculated.
Is determined, the determination in ST8 becomes YES, the cuff 1 is rapidly evacuated, and the measured blood pressure value is displayed on the display 10 (ST9).

FIG. 2 is a flowchart showing a detailed processing operation of the blood pressure estimation processing (ST2) executed during the pressurization. Here, (n) of the pulse wave amplitude AMP (n)
Is a pulse wave number. It is assumed that the AMP (n) and the corresponding cuff pressure PC (n) have been calculated in the pulse wave amplitude calculation process already executed immediately before this process. A variable Am for storing the pulse wave number (n) and the maximum value of the pulse wave amplitude.
ax is assumed to have been initialized to “0” at the start of measurement. First, when the pulse wave number n is updated (ST21), the pulse wave amplitude AMP (n) is compared with the pulse wave amplitude maximum value Amax (ST22). Here, when AMP (n) is larger than Amax, it is determined that the pulse wave envelope is in a rising process (that is, the pulse wave envelope has not reached the maximum point), and the determination in ST22 is YES, and the AMP (n) Is substituted into Amax (ST23), and the process returns. And then A
When MP (n) becomes smaller than Amax, the determination in ST22 becomes NO. That is, it is determined that the pulse wave envelope has already passed the maximum point and is in the process of decreasing, and the process proceeds to ST24. ST24
In, it is determined whether or not AMP (n) has decreased below a threshold value (0.5 × Amax in the embodiment) for determining the systolic pressure. If AMP (n) has not decreased below the threshold value, the determination in ST24 is NO and the process returns (return to ST21). But,
If AMP (n) decreases below the threshold,
The determination in ST24 is YES, and an estimated value of systolic pressure (estimated systolic blood pressure value) Esp is calculated (ST25). During pressurization, the change in cuff pressure is large and the pressure interval between pulse waves is wide. Therefore, if the cuff pressure at the point where the pulse wave amplitude decreases below the threshold value is directly used as an estimated value, accuracy cannot be ensured. Therefore, in the embodiment, the calculation of Esp is performed by linear interpolation to obtain the following equation. Here, THs is a threshold value.

[0011] Thus, after calculating the estimated pressurization value Esp, the process returns.

FIG. 3 is a flowchart showing a detailed processing operation of the blood pressure calculation processing (ST7) executed during the pressure reduction. Here, it is assumed that necessary data such as AMP (n) and Pc (n) has already been calculated in the pulse wave extraction / pulse wave amplitude calculation processing executed immediately before. Also, the pulse wave number n
It is assumed that the systolic pressure SP and the diastolic pressure DP have already been initialized to “0”, respectively.

First, the pulse wave number n is incremented by 1 (ST71). In the next ST72, the AM immediately after the calculation is performed.
P (n) is compared to Amax. Assuming that AMP (n)
Is smaller than Amax, it is determined that the pulse wave envelope has not yet reached the maximum point, and the determination in ST72 is YE
S, the AMP (n) value is substituted for Amax (ST73), and the process returns to ST71. Conversely, AMP
If (n) is larger than Amax, the determination in ST72 is NO, and the process proceeds to the next ST74. When AMP (n) is larger than Amax, it means that the envelope has already passed the maximum point and is in a decreasing process. In the next ST74,
It is determined whether the systolic pressure (systolic blood pressure) SP is “0”. Here, if the SP is “0”, it is determined that the SP has not been determined. In this case, the determination in ST74 is Y
It becomes ES, and shifts to SP calculation processing in ST75 to ST78. Conversely, if the SP has been determined, this ST74
Is NO, and the process shifts to ST79 to execute a DP calculation process. Now, assuming that SP is "0" and has not been determined, the pulse wave counter j is set to the current pulse wave number n in ST75 (ST75). Next, j is decremented by 1 (ST76), and the pulse wave amplitude AMP (j) specified by j
Is compared with the maximum value Amax × 0.5 (ST77). Here, if AMP (j) is larger than Amax × 0.5, the determination in ST77 becomes NO, and the process returns to ST76.
Conversely, if AMP (J) is smaller than Amax × 0.5, PC (j) is set as systolic pressure (systolic blood pressure) SP (ST78). Then, the process proceeds to the diastolic pressure DP calculation process. First, in ST79, it is determined whether or not AMP (n) has decreased below the DP calculation threshold value (AMP × 0.7). If AMP (n) decreases to Amax × 0.7 or less, the determination in ST79 becomes YES, and Pc
(N) is set as DP (ST80), and the process returns.

[0014]

According to the present invention, as described above, the maximum value of the pulse wave amplitude to be extracted during the cuff pressurization is detected, and a threshold value is calculated based on the maximum value. It is determined whether or not the pulse wave amplitude is smaller than the threshold value, and when the pulse wave amplitude during pressurization becomes smaller than the threshold value , linear interpolation of the pulse wave amplitude is performed.
The cuff pressure corresponding to the linear complement value is used as the estimated value of systolic blood pressure,
Since the cuff pressurization is stopped when the cuff pressure further increases and the estimated systolic blood pressure value rises by a predetermined pressure, the pulse wave component is extracted during the cuff pressurization, and the pulse wave signal is extracted. By estimating the systolic pressure based on the pressure, it is possible to automatically stop the pressurization with a cuff pressure that is not too much or too short according to the blood pressure. Therefore, do not apply the micro-speed pressurization (do not reduce the pressurization speed).
While maintaining the same measurement speed by combining linear interpolation
The pressurization target value can be calculated correctly, and
Since it is not necessary to change the output and pressurization target,
As a whole, the time required for the measurement can be reduced , the operability can be improved, the measurement can be speeded up, the pain at the time of the measurement can be reduced, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a main flowchart showing a specific processing operation of an electronic blood pressure monitor according to an embodiment.

FIG. 2 is a flowchart illustrating a blood pressure estimation process during pressurization of the electronic blood pressure monitor according to the embodiment.

FIG. 3 is a flowchart illustrating a blood pressure calculation process during decompression of the electronic blood pressure monitor according to the embodiment.

FIG. 4 is a block diagram illustrating a circuit configuration example of the electronic blood pressure monitor according to the embodiment.

FIG. 5 is an explanatory diagram showing a blood pressure determination process in an oscillometric sphygmomanometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cuff 2 Pressurizing pump 3 Rapid exhaust valve 4 Slow exhaust valve 6 MPU 7 Pressure sensor

Continuing from the front page (72) Inventor Akihiro Sasahata 17 Science Center Building, Chudo-ji Minamicho, Shimogyo-ku, Kyoto (72) Inventor Yoshinori Miyawaki 17 Science Center Building, Chudo-ji Minami-cho, Shimogyo-ku, Kyoto Omron Life Science Laboratory Co., Ltd. (56) References JP-A-60-40038 (JP, A) JP-A-62-292138 (JP, A) JP-A-2-234740 (JP, A)

Claims (1)

(57) [Claims] An electronic sphygmomanometer that determines a blood pressure using a pulse wave obtained from a living body at the time of depressurization of a cuff and a pressure value of a cuff detected by a pressure sensor. Threshold value calculating means for detecting and calculating a threshold value based on the maximum value, comparing the threshold value calculated by the threshold value calculating means with the pulse wave amplitude during pressurization, Judgment means for judging whether the pulse wave amplitude is smaller than the threshold value, and when this judgment means judges that the pulse wave amplitude during pressurization is smaller than the threshold value, linear interpolation of the pulse wave amplitude is performed. A systolic blood pressure estimating means for setting the pressure value corresponding to the linear complement value to an estimated value of the systolic blood pressure, and a time when the pressure value increases by a predetermined pressure with respect to the estimated value estimated by the systolic blood pressure estimating means. Pressure setting means for stopping cuff pressurization. Child sphygmomanometer.