JPH0628638B2 - Electronic blood pressure monitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electronic blood pressure monitor employing a so-called vibration method, which determines a blood pressure by extracting a pulse wave component superimposed on a cuff pressure signal.

(B) Conventional technology In an electronic blood pressure monitor that employs the vibration method, a cuff is wrapped around the upper arm, etc., and the cuff pressure is applied to compress the artery to prevent ischemia. The pulse wave component that is superimposed on the pressure signal is extracted, the waveform information of this pulse wave component is converted into a pulse wave amplitude sequence (parameter sequence), and the maximum value of this pulse wave amplitude is extracted. There is one that determines the blood pressure based on the maximum value and the cuff pressure. As an algorithm for determining the blood pressure in this case, for example, the cuff pressure corresponding to the maximum value of the pulse wave amplitude is the average blood pressure, and 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 used as the systolic blood pressure, and the cuff pressure corresponding to the pulse wave amplitude on the low cuff pressure side corresponding to 70% of the maximum value of the pulse wave amplitude is determined as the diastolic blood pressure.

In this type of electronic blood pressure system, in order to extract the maximum value of the pulse wave amplitude train, conventionally, when the extracted pulse wave amplitude train is continuously attenuated a predetermined number of times, the maximum value extracted so far is Is fixed to the maximum value of the pulse wave amplitude train.

(C) Problems to be Solved by the Invention In the above-described method for extracting the maximum pulse wave vibration width of the electronic blood pressure monitor described above, when the exhaust speed of the cuff is slow, the original change of the pulse wave amplitude is small, and breathing If the pulse wave amplitude fluctuates due to body movement or body movement, a slight decrease in the pulse wave amplitude increase process will cause a false recognition that the maximum value of the pulse wave amplitude has been extracted. Since the blood pressure is fixed as the maximum value and the blood pressure is determined based on the maximum value, a large error may occur in the blood pressure value. For example, the cuff pressure shown in Figure 7 - in the pulse wave amplitude characteristics, though it should be determined that the cuff pressure C _M the mean blood pressure corresponding to the true maximum value AMAX, before the true maximum value AMAX is extracted maxima A'MAX is extracted, the cuff pressure C _'M corresponding thereto is the mean blood pressure, and also based on the maximum value A'MAX, because it determines the systolic and diastolic blood pressure, resulting This will cause a large error in blood pressure determination.

In view of the above, it is an object of the present invention to resist the electronic blood pressure system that can accurately extract the maximum value of the parameter such as the pulse wave amplitude and can accurately determine the blood pressure.

(D) Means and Actions for Solving Problems The electronic sphygmomanometer of the present invention has a cuff 1 and a cuff 1 connected to the cuff for pressurizing or depressurizing the cuff, as shown in the schematic configuration in FIG. The pressure system 2, the pressure sensor 3 for detecting the cuff pressure, the pulse wave extraction means 4 for extracting the pulse wave component contained in the output of the pressure sensor, and the pulse wave component extracted by the pulse wave extraction means. Parameter extraction means 5 for converting the pulse wave amplitude into a predetermined parameter sequence, parameter maximum value extraction means 6 for extracting the maximum value of this parameter sequence, and detection that the extracted parameter sequence is continuously attenuated Attenuation detection means 7, a parameter drop determination means 8 for determining that the parameter has dropped below a predetermined ratio with respect to the maximum value of the parameter, continuous attenuation detection by the attenuation detection means, and the parameter fall. The maximum value determining means 9 for determining the maximum value extracted so far by the parameter maximum value extracting means as the maximum value of the parameter string by the predetermined drop determination output by the lower determining means, the determined parameter maximum value and the cuff. Blood pressure determining means 1 for determining blood pressure based on pressure
It is composed of 0 and 0.

In this electronic sphygmomanometer, the attenuation detecting unit 7 detects that the parameter sequence is continuously attenuated, and the parameter drop determining unit 8 drops the parameter to a predetermined ratio or less with respect to the maximum value up to that point. If it is detected, the maximum value extracted by the parameter maximum value extraction means 6 until then is determined as the maximum value of the parameter sequence. Therefore, even if the parameter sequence is continuously attenuated, if the change is slight, the maximum value is not yet determined.

(E) Examples Hereinafter, the present invention will be described in more detail with reference to Examples.

FIG. 2 is a block diagram of an electronic sphygmomanometer in which the present invention is implemented. In the figure, a cuff 11 is a well-known rubber bag to be wound around an arm, and is connected to an exhaust valve 13 and a pressurizing pump 14 constituting a pressure system 12 by a rubber tube 15. Further, the pressure sensor 16 is also attached to the cuff 1 by the rubber tube 15.
1 is connected to convert the cuff pressure into an electric signal. As will be described later, the output of the pressure sensor 16 includes a pulse wave component that is superimposed on the direct current component of the cuff pressure, and this output is converted into a digital signal by the A / D converter 17 and is then sent to the CPU 18. It is supposed to be included.

The CPU 18 executes a predetermined process in accordance with a built-in program and takes in raw data from the pressure sensor 16,
Separation of cuff pressure and pulse wave component from the raw data, the function of extracting the cuff pressure and pulse wave component respectively, the function of extracting the amplitude of the pulse wave component, the function of extracting the maximum value of the extracted pulse wave amplitude, A function to detect that the extracted pulse wave amplitude sequence is continuously attenuated, a function to determine that the extracted pulse wave amplitude has dropped below a predetermined ratio to the maximum value, and the maximum value of the pulse wave amplitude It has a function to determine the maximum and minimum blood pressure from the cuff pressure. The determined blood pressure value is displayed on the display device 19.

When the measurement start key (not shown) is operated, the CPU 18 starts the operation of the pressurizing pump 14 by the command a,
The cuff 11 is pressurized, and the exhaust amount of the exhaust valve 13 is controlled by the command b. Further, the cuff pressure superposed with the pulse wave component from the pressure sensor 16 is read at a predetermined sampling cycle by the command c.

Next, the operation of the electronic blood pressure monitor of the above embodiment will be described with reference to the flow chart shown in FIG.

When performing the measurement, the cuff 11 is wrapped around the upper arm and the measurement start key is pressed. As a result, the operation is started. First, the pressurizing pump 14 is started to operate by the command a, and pressurization of the cuff 11 is started [step ST (hereinafter abbreviated as ST).
1]. Then, the pressurization is continued to a predetermined value. This predetermined value is higher than the normal systolic blood pressure value of the subject (example:
It is preset to +30 mmHg). When the cuff pressure reaches a predetermined value (ST2), the operation of the pressurizing pump 14 is stopped and the pressurization is stopped (ST3). Then, the exhaust valve 13 is set to a slow speed exhaust in response to the command b, and a slow depressurization process is started from the state where the exhaust valve 13 is pressurized to a predetermined value until then (ST
4). That is, the measurement operation starts. When the slow speed exhaust is started, the timer T ₁ (time 10 to 30 milliseconds) built into the CPU 18 is started (ST5), and every time the time is up,
In other words, every time T ₁ elapses (ST6), the A / D converter 1
The output data of No. 7 is read (ST7). The output data of the A / D converter 17 is raw data in which the pulse wave component is superimposed on the cuff pressure (DC component), as shown in FIG. 5 S (i). Next, the raw data S (i) is calculated to obtain the cuff pressure Pc (i) (ST8). This cuff pressure Pc (i) is
As described above, the pressure gradually drops during the depressurization process [see FIG. 5 Pc (i)].

Further, the raw data S (i) is subjected to arithmetic processing as a digital filter to extract the pulse wave component A (i) shown in FIG. 5 (ST9). This filtering process is the cut frequency
It is a secondary high pass of 0.3 to 1 Hz. Instantaneous pulse wave component A
After (i) is extracted, it is determined whether or not one pulse wave worth of data for obtaining the pulse wave amplitude is obtained (ST10), 1
If the pulse wave data has not been extracted, the process returns to ST5,
The processes of ST5 to ST10 described above are repeated to extract the cuff pressure data Pc (i) and the pulse wave data A (i) for each T ₁ .

When the pulse wave data for one pulse wave is obtained, the determination in ST10 is YES, the difference value between the maximum value and the minimum value of the pulse wave data A (i) for one pulse wave is calculated, and the pulse wave amplitude A (n) is calculated (ST11). Further, the cuff pressure Pc (n) corresponding to the extracted pulse wave amplitude A (n) is selectively stored (ST12).
When the pulse wave amplitude A (n) until the end of the measurement is arranged in correspondence with the cuff pressure Pc (n), the pulse wave amplitude train shown in FIG. 5 is obtained.

Following the pulse wave amplitude calculation and the corresponding cuff pressure selection, it is determined whether or not the pulse wave maximum amplitude has been detected (ST13). Normally, since the pulse wave amplitude is rising for each pulse wave at the beginning of the measurement, this determination is NO, the process proceeds to ST14, the pulse wave amplitude maximum value detection processing is performed, and the pulse wave maximum value is detected in ST15 ( (Decided) is determined. At the beginning of measurement, the determination in ST15 is NO for the above reason, and the process returns to ST5. The details of the pulse wave amplitude maximum value detection processing in ST14 and ST15 will be described later.

When the measurement operation progresses and the pulse wave amplitude maximum value AMAX is detected, the determination in ST15 is YES, and then αAMAX (AMA) is obtained by multiplying the pulse wave amplitude maximum value AMAX by α (eg, α = 0.5).
The cuff pressure Pc (s) corresponding to the cuff pressure higher than X) is determined as the systolic blood pressure (ST16). Then, the process returns to ST5.

Even after that, while the depressurizing process of the cuff continues, the processes after ST5 are continued. Since the pulse wave amplitude maximum value has already been detected, the determination in ST13 is YES, and then the current pulse wave amplitude A (n) is β in the extracted pulse wave amplitude maximum value AMAX.
(Example: β = 0.7) It is determined whether or not βAMAX has been reached (ST17). While the pulse wave amplitude A (n) is larger than βAMAX, this determination is NO, the process returns to ST5 and S
The processes of T5 to ST13 and ST17 are continued. When the pulse wave amplitude A (n) reaches βAMAX, the determination in ST17 is YES.
Then, the cuff pressure Pc (D) corresponding to βAMAX (lower cuff pressure side than AMAX) is determined as the minimum blood pressure (ST1).
8). This completes the measurement. Although illustration is omitted, when the minimum blood pressure is determined, the maximum blood pressure, the minimum blood pressure, etc. are displayed on the display unit 19, and the inside of the cuff 11 is rapidly exhausted.

Next, the pulse wave amplitude maximum value detection processing in ST14 will be described in detail with reference to FIG.

In the main flow shown in FIG. 3, when the operation enters ST14, as shown in FIG. 4, first, the maximum value AMAX of the pulse wave amplitude up to then is compared with the current pulse wave amplitude A (n), and " A
MAX ≧ A (n) is “judged” (ST41). If the pulse wave amplitude A (n) is increasing with the progress of processing, as in the beginning of the measurement, the judgment of ST41 is NO, and this time The pulse wave amplitude A (n) is updated and stored as a new maximum pulse wave amplitude value AMAX (ST42), the flag FAMAX indicating that the maximum pulse wave amplitude has been detected is set to 0 (ST43), and the counter CT is set to 0 (ST44). , Return to ST5.

When the pulse wave amplitude A (n) changes from rising to falling, ST4
The determination of 1 is YES, the counter CT is then incremented by 1 (ST45), and it is determined whether the content of the counter CT is K or more (ST46). This counter CT is CPU1
8 is provided to count the number of continuous falling (attenuation) of the pulse wave amplitude A (n).

If the count value of the counter CT is smaller than K (eg, K = 3), the determination in ST46 is NO and ST is left unchanged.
Returning to step 5, when the count value reaches K, the determination in ST46 becomes YES, and subsequently "γ × AMAX ≥ A (n)" is determined (ST47). That is, the pulse wave amplitude A (n) has a predetermined value γ (eg, γ =
(0.7 to 0.9) and determine whether it has become smaller than the value. If this judgment is NO, even though the pulse wave amplitude A (n) continuously decreases, the change is slight and the maximum value up to that time is, for example, A'MAX in FIG. It means that it is not a true pulse wave amplitude maximum value. Therefore, the process directly returns to ST5.

When γ × AMAX ≧ A (n) is satisfied, pulse wave amplitude A
This means that the pulse wave amplitude A (n) was sufficiently attenuated in the descending process of (n), and in this case, the extracted AMAX is highly likely to be the true maximum value of the pulse wave amplitude.

If the determination in ST47 is YES, then the cuff pressure Pc (AMAX) corresponding to the pulse wave amplitude maximum value AMAX is the predetermined pressure Pc.
₁ (Pc ₁ = 110-120 mmHg selected) It is judged whether or not (ST48), and if the judgment is YES, that is, Pc (AMA
X) is Pc ₁ or more, pulse wave amplitude maximum value AMAX is D (D = 1 to 2 mmHg) or more (ST49), and if ST48 is NO, that is, Pc (AMAX) is Pc. If it is less than ₁ , the maximum pulse wave amplitude AMAX is E
When (E = 0.5 to 1 mmHg) or more (ST50),
The flag FAMAX for which the maximum pulse wave amplitude has been detected is set to 1 (ST51). The processing of ST48 to ST50 is
This is done to prevent false detection of noise. Then ST5
2, the cuff pressure Pc (n) corresponding to the current pulse wave amplitude A (n)
Is above a predetermined pressure Pc ₂ (Pc ₂ = 90 to 110 mmHg), the process returns to ST5 even if the maximum value has already been detected.
The pulse wave amplitude maximum value detection process is continued to run, and if A (n) exceeding AMAX is detected, the processes of ST42 to ST44 are performed, and the pulse wave amplitude maximum value detection process is newly performed.

In the above embodiment, the maximum amplitude value is checked depending on whether the corresponding cuff pressure Pc (AMAX) is Pc ₁ or more.
Although it is performed at two levels of D and E, as shown in FIG. 6, Pc (AMAX) and AMAX may be checked as a continuous function. The check regarding ST49 and ST50, or the check according to FIG. 6 utilizes the phenomenon that the pulse wave amplitude is high in a hypertensive patient and small in a hypotensive patient.

However, in the above-mentioned embodiment, in order to perform more complete detection of the pulse wave amplitude maximum value, the processing after ST48 is performed.
Therefore, these processes are omitted and ST46 and ST47 are executed.
Only with the above process, the pulse wave amplitude maximum value can be detected more accurately than the conventional one.

(F) Effect of the Invention According to the present invention, in addition to the detection of continuous attenuation of the maximum value of the parameter such as the pulse wave amplitude, when there is an attenuation of a predetermined ratio or more with respect to the maximum value up to that time, The maximum value of the pulse wave parameter that has been extracted up to is determined as the true maximum value of the pulse wave parameter.Therefore, when the exhaust velocity is slow, the Since it is possible to determine only the true maximum value of the pulse wave parameter as the maximum value without determining the maximum value of, the blood pressure can be determined with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of the present invention, FIG. 2 is a block diagram of an electronic sphygmomanometer in which the present invention is implemented, and FIG. 3 is a main flow for explaining the operation of the electronic sphygmomanometer. 4 and 5 are flow charts showing the pulse wave amplitude maximum value detection processing routine of the main flow chart in more detail, and FIG. 5 is a waveform time chart for explaining the operation of the electronic sphygmomanometer. Figure 6 shows the cuff pressure Pc (A
MAX) and pulse wave amplitude maximum value AMAX, which shows the verification characteristics, No. 7
The figure is a figure which shows the cuff pressure-pulse wave amplitude characteristic for demonstrating the problem of the conventional electronic sphygmomanometer. 1: Cuff, 2: Pressure system, 3: Pressure sensor, 4: Pulse wave extracting means, 5: Parameter extracting means, 6: Parameter maximum value extracting means, 7: Attenuation detecting means, 8: Parameter drop determining means, 9: Maximum value fixing means, 10: blood pressure determining means.

Claims (1)

[Claims] 1. A cuff, a pressure system connected to the cuff for pressurizing or depressurizing the cuff, a pressure sensor for detecting the cuff pressure, and a pulse wave component contained in the output of the pressure sensor. Pulse wave extracting means, parameter extracting means for converting the pulse wave amplitude of the pulse wave component extracted by the pulse wave extracting means into a predetermined parameter string, and parameter maximum value extracting means for extracting the maximum value of the parameter string. An attenuation detecting unit that detects that the extracted parameter sequence is continuously attenuated, a parameter drop determining unit that determines that the parameter has dropped below a predetermined ratio with respect to the parameter maximum value, The maximum value extracted so far by the parameter maximum value extraction means is determined by the continuous attenuation detection by the attenuation detection means and the predetermined drop determination output by the parameter fall determination means. Maximum value determining means and an electronic sphygmomanometer comprising a pressure determining means for determining a blood pressure based on the determined parameter maximum value to the cuff pressure to determine the maximum value of the parameter column.