JPH0618549B2 - Blood pressure measurement device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a blood pressure measurement device, and more particularly to a technique for removing noise during blood pressure measurement.

Conventional technology Conventionally, Korotkoff sound, pulse wave (pressure vibration of cuff), which is generated with a pressure change of a cuff wound around a part of a living body,
Pulse synchronization waves such as arterial wall vibration detected using the Doppler effect of ultrasonic waves are sequentially sampled by the pulse synchronization wave detection means, and the blood pressure value of the living body is measured based on the change in the magnitude of the pulse synchronization waves. A blood pressure measuring device is provided.

Problems to be Solved by the Invention However, in such a blood pressure measurement device, noise may be mixed into the collected pulse synchronization wave, and thus blood pressure measurement may not be performed accurately.

Means for Solving Problems The present invention has been made in the background of the above circumstances,
The gist of the point is that, as shown in the claim correspondence diagram of FIG. 1, pulse-synchronous waves generated with changes in pressure of a cuff wound around a part of a living body are sequentially sampled, and the pulse-synchronous waves are collected. A blood pressure measurement device for measuring a blood pressure value of a living body based on a change in size, (a) sequentially moving a first window of a predetermined constant time width, the pulse synchronization in the first window By calculating the difference between the maximum value and the minimum value of the wave, the pulse synchronization wave is converted into a noise-removed first signal wave having a period shorter than the first window and an amplitude smaller than the pulse synchronization wave. First signal wave processing means for sequentially processing, (b) by sequentially moving the second window of a predetermined constant time width, the center of the second window is the maximum of the first signal wave in the second window Must match the value By setting the value of the first signal wave corresponding to the center of the second window at that time to zero, and setting the maximum value to the value at that time when they match, the first signal wave is converted into a pulse-shaped second signal. A second signal wave processing means for sequentially processing a wave, and (c) blood pressure value determining means for determining a blood pressure value based on the second signal wave.

By doing so, the first signal wave processing means sequentially moves the first window having a predetermined constant time width, and the difference between the maximum value and the minimum value of the pulse synchronization wave in the first window is reduced. By the calculation, the pulse-synchronized wave has a period shorter than the first window and is sequentially processed into a first signal wave from which noise having an amplitude smaller than the pulse-synchronized wave is removed, and the second signal wave is also processed. When the processing means sequentially moves the second window having a predetermined constant time width and the center of the second window does not match the maximum value of the first signal wave in the second window, the second window at that time is moved. The value of the first signal wave corresponding to the center of the two windows is set to zero, and when they match, the maximum value is set to the value at that time. The blood pressure value is processed into the second signal wave, and the blood pressure value is determined by the blood pressure value determination means based on the second signal wave.

As a result, even if noise is mixed in the collected pulse synchronization wave, if the noise cycle is shorter than the time width of the first window and the noise amplitude is smaller than the pulse synchronization wave amplitude, The noise can be effectively removed, and the blood pressure measurement can be performed more accurately than before.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 2, reference numeral 10 denotes a rubber bag-shaped cuff that is wound around the upper arm of the subject. A pressure sensor 12, an air pump 14, a throttle 16 for slow exhaust, a solenoid valve 18, and a solenoid valve 20 for rapid exhaust are connected to the cuff 10 via pipes 22, respectively. The pressure sensor 12 supplies a pressure signal SP indicating the pressure in the cuff 10 to the static pressure discrimination circuit 24 and the pulse wave discrimination circuit 26, respectively. The static pressure discrimination circuit 24 includes a low-pass filter, discriminates the cuff pressure signal SK representing the steady pressure contained in the pressure signal SP, and supplies the cuff pressure signal SK to the CPU 30 via the A / D converter 28. To do. The pulse wave discrimination circuit 26 includes a band pass filter, and the pulse wave signal S representing the pulse wave included in the pressure signal SP.
M is discriminated and the pulse wave signal SM is supplied to the CPU 30 via the A / D converter 28. This pulse wave is a pressure vibration wave of the cuff 10 that is generated in synchronization with the heartbeat of the measurement subject.

The CPU 30 uses the data bus line to read the ROM 34,
RAM 36, display 38, and output interface 4
0, and performs signal processing while utilizing the storage function of the RAM 36 according to a program stored in the ROM 34 in advance, and the air pump 14 and the solenoid valves 18 and 20.
On the other hand, a series of blood pressure measurement operations are executed, the blood pressure value is determined by the oscillometric method based on the pulse wave signal SM and the cuff pressure signal SK, and the blood pressure value is displayed on the display 38.

The operation of this embodiment will be described below with reference to the flowchart of FIG.

When the power is turned on, the initial process of step S1 is executed, and step S2 is executed to determine whether or not the measurement start push button switch 42 has been operated. If this determination is denied, step S2 is repeatedly executed to enter the standby state, but if the switch 42 is operated, step S3 is executed so that both solenoid valves 18 and 20 are closed. At the same time, the air pump 14 is activated and the pressure inside the cuff 10 is increased. Next, in step S4, it is determined whether the cuff pressure P has exceeded a predetermined constant target cuff pressure Pm.
The target cuff pressure Pm is a pressure sufficiently higher than the systolic blood pressure value, for example, a value of about 180 mmHg. When the cuff pressure P has not yet exceeded the target cuff pressure Pm, step S3
Although S4 and S4 are repeatedly executed, when the cuff pressure P exceeds the target cuff pressure Pm, step S5 is executed to stop the air pump 14 and open the solenoid valve 18 to open the cuff 10. The gradual reduction of voltage is started. Subsequently, when step S6 is executed, sampling of the pulse wave signal SM discriminated by the pulse wave discriminating circuit 26 is started. FIG. 4 is a graph showing the relationship between the magnitude of the pulse wave signal SM thus obtained and the time n as a waveform X (n) for the sake of convenience. Not visible. This also applies to the waveform Y (m) and the waveform Z (1) described later. In this embodiment, the waveform X (n) representing the pulse wave corresponds to the pulse synchronization wave, and the pulse wave discrimination circuit 26 and step S6 correspond to the pulse synchronization wave detection means. Next, by executing step S7, if the current sampling time point of the pulse wave signal SM in FIG.
From the time point k2, which is a predetermined time N / 2 back from
The difference Y (m) between the maximum value X _max of the waveform X (n) and the minimum value X _min after the maximum value X _max in the first window WN having the time width N centered at Is calculated according to. In the pulse wave, the lower peak usually occurs immediately after the upper peak, and therefore the minimum value X _min after the maximum value X _max is targeted.

Y (m) = X _max [k2-N / 2, k2 + N / 2] -X _min [n xmax, k2 + N / 2] (1) where m = n-N / 2 n xmax: at the time of X _max N In this case, when the minimum value X _min exists before the maximum value X _max , Y (m) = 0. FIG. 5 is a graphical representation of the waveform Y (m) processed from the waveform X (n) by sequentially moving the first window WN.
The time width N of the first window WN is, for example, 225.
It is set to about ms. Next, when step S8 is executed, the time width M around the time point k3, which is a predetermined fixed time period M / 2, goes back from the time point k1 (the same time point as the time point k1 in FIG. 4) in FIG. Second window WM
Is set and whether or not the time point k3, which is the center thereof, coincides with the time point of the maximum value Y _max in the second window WM of the waveform Y (m), and when they do not coincide, the second window WM at that time is determined. The value of the waveform Y (m) corresponding to the center of is set to zero, and when they match, the maximum value Y _max is set to the value at that time. At the time point k3, the value at the time point k1 is set to zero in FIG. 6 because it does not match Y _max . Then, by sequentially moving the second window WM, when the center of the second window WM is located at the time point k1 in FIG. 5, a pulse-like pulse having a size Y _max at the time point k1 + M / 2 in FIG. The signal is obtained. As a result, the waveform Y (m) is processed into the pulse-shaped waveform Z (1). Note that 1 = m−M / 2. In this embodiment, the waveform Y (m) corresponds to the first signal wave and the waveform Z (1) corresponds to the second signal wave, and step S7 is the first signal wave processing means and step S8 is Each corresponds to the second signal wave processing means. The time width M of the second window WM is set according to the person to be measured, and is, for example, 6
The time is set to 1.5 times the average of the pulse interval or about 1.5 times the minimum value of the pulse interval up to an arbitrary time point. In this case, a predetermined fixed time width, for example, a time width of about 500 ms is adopted until the second window WM is calculated as described above. Next, when step S9 is executed, it is determined whether or not the signal corresponding to the pulse wave is detected, based on whether or not Z (1) is zero. When Z (1) is zero, the pulse wave is not detected, so steps S6 to S9 are repeatedly executed.
When it is determined that Z (1) is not zero, the following step S
10 is executed and the magnitude of Z (1) and the cuff pressure P at that time are read into the RAM 36 together with the time data.
Next, in the blood pressure value determination routine of step S11, the so-called oscillometric method for determining the systolic blood pressure value and the diastolic blood pressure value based on the change in the magnitude of the processed waveform Z (1) is well known. A blood pressure determination algorithm is executed, which determines the systolic and diastolic blood pressure values. This step S11 corresponds to the blood pressure value determining means of this embodiment. Next, when step S12 is executed, it is determined whether or not the blood pressure value measurement is completed. If not completed, steps S6 to S12 are repeatedly executed, but if the blood pressure measurement is completed, The following step S13 is executed and the maximum blood pressure value and the minimum blood pressure value are displayed on the display unit 38.

Thus, according to this embodiment, the waveform X corresponding to the pulse wave
By performing a predetermined process in the first window WN that moves sequentially to (n), the first window WN
It is processed into a waveform Y (m) from which noise having a shorter cycle and an amplitude smaller than the pulse wave is removed, and a predetermined processing is performed in the second window WM which is sequentially moved to the Y (m). Pulsed waveform Z (1)
Since the blood pressure value is determined based on this waveform Z (1), even if noise is mixed in the waveform X (n), the noise cycle is shorter than the time width of the first window WN and When the amplitude of the pulse wave is smaller than that of the pulse wave, the noise can be effectively removed, and the blood pressure measurement can be performed more accurately than in the conventional case.

Further, according to the present embodiment, since the minimum value X _min of the waveform X (n) in the first window WN is the maximum value X _max or later, the substantial time of the first window WN is set. The width N can be reduced, and even if there is a minimum value due to noise before the maximum value X _max , the effect due to the noise can be eliminated.

In the above-described embodiment, real-time processing is performed in which Y (m) and Z (1) are calculated (processed) according to the sampling of the pulse wave signal SM, but this is not always necessary. For example, batch processing may be performed in which Y (m) and Z (1) are calculated (processed) at once based on the waveform X (n) after all pulse wave signals SM have been collected.

Further, in the above-described embodiment, the pulse wave is adopted as the pulse synchronization wave, but the pulse synchronization wave may be a pulse sound (Korotokov sound) generated with the pressure change of the cuff. In this case, the first window WN is, for example, 2
The second window WM is set to about 0 ms, respectively, similarly to the case of the pulse wave.

Besides, the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention. FIG. 2 is a block diagram showing an embodiment of the present invention. Figure 3 is second
6 is a flowchart for explaining the operation of the embodiment in the figure. FIG. 4 is a diagram showing a waveform X (n) in which a sampled pulse wave signal is graphically displayed. FIG. 5 is a diagram showing a waveform Y (m) obtained by subjecting the waveform X (n) of FIG. 4 to predetermined processing. FIG. 6 is a diagram showing a waveform Z (1) obtained by subjecting the waveform Y (m) of FIG. 5 to predetermined processing. 10: Cuff 26: Pulse wave discrimination circuit

Claims (1)

[Claims] 1. A pulse-synchronous wave that is generated with a change in pressure of a cuff wound around a part of a living body is sequentially sampled by a pulse-synchronous wave detecting means, and the pulse-synchronous wave is detected based on a change in the magnitude of the pulse-synchronous wave. A blood pressure measuring device for measuring a blood pressure value of a living body, wherein a first window having a predetermined constant time width is sequentially moved, and a difference between a maximum value and a minimum value of the pulse synchronization wave in the first window is calculated. First signal wave processing means for sequentially processing the pulse synchronization wave into a first signal wave from which noise has been removed by calculation, the period having a period shorter than the first window and an amplitude smaller than the pulse synchronization wave. And sequentially moving the second window having a predetermined constant time width, and when the center of the second window does not coincide with the maximum value of the first signal wave in the second window, the second window at that time is moved. Two windows A second signal wave is sequentially processed by setting the value of the first signal wave corresponding to the center to zero and setting the maximum value to the value at that time when they coincide with each other. A blood pressure measuring device comprising: a signal wave processing means; and a blood pressure value determining means for determining a blood pressure value based on the second signal wave.